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Planning A Solar Power System - The Dodd/Kurylo Family`s House
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1. Each row contains one stock extension cable and its original length Columns to the right hold candidate PV pair cable IDs e g AB Pos CD Neg and how long it must be The far right column subtracts the Planning A Solar Power System Choosing Solar Panels Part 2 Page 80 candidate lengths in that row from the stock length and displays the number of feet remaining A negative number means that combination of candidates won t work for that stock cable try another combination Notice the columns containing JK Pos and LM Neg entries with zero length These are present for completeness and indicate that panel pairs JK and LM are close enough to the combiner box that they need no extension cable just cut off the connector and feed the cable directly into the combiner box The final step is to cross check to ensure that you have positive and negative entries for each panel or panel pairs in this case Connecting multiple PV panels Notice that the PV panels in Figure 24 are designated in pairs and each pair is considered a single unit To connect multiple PV panels in series imply plug the positive cable connector from one into the negative connector on the next and so on The unconnected cables at the ends of the string become the positive and negative cables to run to the combiner box How will the solar energy reach the system Once the PV panels are wired to the combiner box there must be a way to transf
2. Full power inverter current Breaker to feed solar box 6A 12A 10A 13A 17A 15A 18A 22A 20A 23A 27A 25A 29A 32A 30A 33A 37A 35A 38A 42A 40A 43A 47A 45A Table 24 Circuit breakers for maximum inverter currents 240VAC Feeding grid power to the solar box Look at Table 24 and ask the electrician to install an appropriately sized breaker in the grid box branch that feeds the solar box He might be surprised by feeding an entire breaker box with such a small breaker but assure him that you have done your homework and have a handle on the loads the solar box will feed Explain that ultimately the inverter which produces XX amps will power those same branches Planning A Solar Power System The Complete System Page 99 It is unlikely that any breaker with such a low rating is available for the solar box s main breaker position No problem tell the electrician to install the smallest main breaker available probably 60A The solar box is protected by the XX amp grid box branch breaker now and by the inverter later so the size of the solar box s main breaker is irrelevant Pretend you re on solar power for awhile Notice in Table 24 that the recommended breaker size falls in the middle of the inverter current range There is a reason for this Plan on powering the solar panel from the grid box for at least six months possibly while you re doing the year long site survey page 64
3. cscescecseesseeeseeeseeeseeseeeeseesenensaeeeenesseeneaes 115 Provide easy access to a solar Alayes aaia rania 115 Mark electrical OuUtUEtS tL 116 SS 2 rts MONO t 116 Se eq UE E et RE E eee oe 116 DEL Star ucc KI EM M E EE ae 117 he Dodd Kurylo Solar Power System The solar a Ea eiaa aa a 118 Making power in shade or eIOUS ssqesikdrrcdohiad c pk REX KER UR FRU GER DELA E RR OFEN ka DER EU RR 119 PY cabling to the TIES e 119 Cabine Me PU anay ee 120 Solar panel SUBBOEOS si ia inpr ER t UFU FEDI ORNA aa aiana eii 121 DEDE oou bU RD E Ed RIS vip UU NM EM IM EFI ME 122 LOU CODE oi reser ve e ieiunus iced tau Ei MEDIE EE E d eee eee 123 SEIRA ocossups du rca lE ser LM MEM E MM DE CE 125 Computer progr OBL cenam EN nkaraan NzRIAUM RUE MEGA E REEN LG MP LEFRUK E URNA KEAM D MM MENU M 125 SUM ante prag aii caussa REIP ivxe kl Bine co oh p Yo 2a Aenean 125 INTRODUCTION Hello my name is Mike Dodd In this document I explain how to design and install a solar power system using knowledge my wife Louise Kurylo and I gleaned from building one for our home We hope this information saves you some time and effort as you plan your own system I am not an expert on all types of solar power systems nor am I a professional engineer or electrician I m just a retired computer programmer But I have fiddled with many things mechanical and electrical over t
4. heavier than the 2 string cables Because each carries the full battery bank Figure 32 Battery cable tie points current rather than the 1 3 of it carried in a string cable The positive and negative terminals are flanked by plywood barriers and the enclosures are painted red for positive and black for negative for easy identification Notice the clear Lexan cover over the terminals This worthwhile safety feature prevents stray metal items like pliers or other tools from bridging the terminals which would cause an enormous electrical arc A negative black cable tie bar is barely visible in the upper right corner of Figure 7 This one is fabricated from heavy copper bar with holes for large bolts to hold the terminal lugs Equal cable lengths Each cable in a battery string must be exactly the same length as its counterpart in every other string The reason for this requirement is explained below Note the word counterpart This will become clear in the following paragraph Figure 33 illustrates the requirement In each string of four batteries the colored cables must be exactly the same length as their like colored counterpart cables in other strings Counterpart means in the same string position All of the green cables are in the same position in their strings as are all of the red cables Planning A Solar Power System The Complete System Page 88 and all of the teal cables All blue 1 cables are in the sa
5. Some solar power systems can start a generator automatically when needed Depending on the generator s starting circuit it might be able to connect directly to a system component such as the inverter or a special electronic module might be required to convert from 2 wire start to 3 wire start Read data sheets and talk to vendors to determine what equipment will work together Connecting the system to house wiring The basics A solar power system is useless if it s not connected to household wiring so it can run appliances Essentially you need a solar breaker box that is wired with branch circuits to appliances you identified in Warning Danger again Any breaker box that can receive power from more than one source must have mechanical interlocks to prevent any power source from being connected to any other power source This means that interlocks must allow only one power source to be connected to the box at a time It allows you to switch on a breaker only if all conflicting breakers are switched off There must be an interlock to disconnect grid power from the box whenever the inverter or generator is switched into it and disconnect those devices whenever the grid is switched in And as cautioned above there must be an interlock to prevent the inverter and the generator from being switched in at the same time Our choice auto start The Outback Radian inverter can close a relay to run a gene
6. Planning A Solar Power System by Mike Dodd mike mdodd com Revised November 8 2014 Copyright 2013 Michael M Dodd All rights reserved Table of Contents DESSEN isin esas ane Le ei VIA TRA LEMR Neale 1 Navigating the CO CUNNING 1 PICU ANS omino nnne e a a Ec 2 e A A nra a E C A EEA A A T 2 Personal comme mnSoi iade ea aE a Edu D TRES 2 Personal Gomshtes ied invo is Fc i tie e Forces ce cio aos e E Eo Pe HUE Gere ded dte tbi be aa I eevbennadeunaati 2 Internet ln KS cte rota et cese aN EeKE FF FeVYAHI a a 2 Electrical CLS TIPPER IIS uc cocco cnet dates ag rada Vtt eaa FEX a c Pa bv ace ados pases EAAS 3 Solar power QGHNIHONHS cirea sio Ginieithso ap ainiin rege tu o ree Peer ae eres eee 4 Electrical formulas nni iro er ee S 7 Reason F2 Backup POWO asinan oain anran AN o ariii 9 OWE firstchoice packup Pi 9 Reason 3 Independent LIVING ssscssessrvsessoasessssneesr0cever0nesenecesnrsansseanesanioansisnresaninassisinssaaisenntes 10 Reason 4 Selling POWGT sssini paie S ieee neler eee 10 Reason 5 Green enel Bossier bt EP FER FECHA aoea ia D UR hen 10 Reason 6 Lower electric bills 1 ecce eser serre eese rere enne nnnm e nna nnn anna naa nn aua 10 Ourcholce FA and 46 iin catt eee eoe eye EE Ede eects 10 Reason F7 You can afford E mm 11 How a Solar Power Sy
7. Pretend you re on solar power and use your lights and appliances normally If the solar box feeder breaker ever trips you know your inverter would have shut down under the same circumstances What caused the breaker to trip Did someone use two high power appliances at once Was this an isolated incident or does the breaker trip often An isolated incident is okay but if the breaker trips frequently especially when high power appliances e g microwave oven toaster well pump are not being used together it indicates your candidate inverter is too small It s time to re visit your solar power audit on page 18 Better to discover the problem now than after the system is bought and installed Provide for feed cables into a new house Building a new house offers the opportunity for feed cables from the solar array and generator to come into the house without drilling through walls later It is easy for a contractor to bury a length of 2 PVC conduit from inside the house to outside and cap the end When you are ready to bring feed cables inside dig out the buried conduit and pull your cables through Even if the solar power system is not located in a basement the conduit can run down a wall and through the foundation to reach the outside For a roof mounted PV array ask your vendor how to equip the new house for feed cables Figure 42 shows the end of conduit that was buried when the house was built It was dug u
8. an From To Next month Next Doy Curent eo N 7 TM KW 5 evtl N 50 ag We a 20 90 Bat pedi Figure 66 Solar power monitor program ev ae r Page 122 Planning A Solar Power System The Dodd Kurylo Solar Power System Some meter faces turn green when we are producing solar power and saving money and others turn red pink when we are buying power from the grid The program works well but it wasn t easy getting there The owner s manual for the MATE system controller states that it produces a data stream on the Ethernet port but discovering how to capture the data was a struggle Outback Power technical support didn t know anything about it so I was on my own Only after playing around on our Linux server for a few days did I discover the data stream s network format UDP and I was able to capture data from it Outback tech support was overjoyed when I passed along my discovery I wanted to keep data over time so any program capturing the data also needed to store it somewhere I wrote a C program running on the Linux server to capture the data and every five minutes write a new record in a MySQL database running on the same server The current record is updated every 10 seconds so the client has recent data The client side program on my PC connects to the database and reads whatever data it needs It can read the current status record or retrieve historical data for o
9. exceeds its capacity But you still need circuit breakers between the inverter and household wiring Figure 39shows two 50A breakers one on the grid input to the inverter and the second on the inverter output to a household breaker box In reality This 8 KW inverter will shut These breakers are down over 33A I P V page 7 interlocked with the 000 watts 240V 2333 5 so the ed bracket to allow the u E5 50A breakers are unlikely to trip EDES M 50 to a bypass mode which Figure 41 Inverter AC circuit breakers They are used mainly as switches for the bypass interlock connects the grid input directly to the household breaker box normally connected to the inverter s output This is useful when the inverter must be shut down for maintenance or to upgrade its firmware the microcontroller program that controls it Generator A generator definitely is optional in a solar power system But including one could mean the difference between having lights during a grid outage and not having lights No matter how large a solar array or battery bank you have sooner or later you will hit several days or a week of cloudy rainy or snowy weather What will you do when the battery bank is discharged and the inverter shuts down With a generator you can grit your teeth crank it up and burn expensive fossil fuel until the grid comes up or the sun shines again A large generator can power your solar applianc
10. http www topbulb com find low temperature cfl asp Receptacle also called outlet is the wall fixture into which appliances are plugged The words are used interchangeably Solar power definitions You will run across these terms in this document and in the solar power field in general Ultraviolet light abbreviated UV is light with a wavelength shorter than that of visible light UV light can pass through some clouds that block much visible light Photovoltaic abbreviated PV describes a material that produces a voltage when exposed to radiant energy such as light PV panel or solar panel is an assembly of PV cells wired together to provide power when illuminated by sunlight The terms PV panel and solar panel are used interchangeably PV array or solar array both refer to a group of PV panels wired together Planning A Solar Power System Definitions and Formulas Page 4 Azimuth is the direction of the sun from the observer expressed as the angular measurement from the north If the sun rises directly in the east its azimuth is 90 from north At solar noon the azimuth is 180 or due south If the sun sets directly in the west its azimuth is 270 from north Elevation is the angular measurement of the sun s height in the sky The elevation is 0 at the moment the sun rises or sets on a flat horizon the ocean It is at its lowest noon elevation at noon on the winter solstice near Decem
11. lower than the table s optimal tilt angle for winter Planning A Solar Power System Site Survey Part 2 Page 63 How to conduct a year long site survey It takes planning patience and persistence to collect the information you need over 12 months Keep a notebook or create a folder on your computer to store photos and notes You ll need a digital camera an inexpensive point and shoot model will work fine It s a plus if your camera can imprint a date and time on the image but this is not necessary You should save the image files on your computer but you might also want to copy them to a USB flash drive and take them to a local pharmacy or other store to have prints made 4 x6 prints are fine Follow these steps 1 Find a vantage point Pick a spot that gives a good view of your proposed solar array site It should be easily accessible even if the ground is wet or covered with snow 2 Find a repeatable camera location You should position the camera in the same spot each time you snap a photo of the site This allows you to quickly and easily see changes from one month to the next If you are skilled with photo editing software you later can create an animation that plays an entire year on your computer monitor I was fortunate that a bathroom window overlooks the site so I could rest my camera on Se i 30 Az 208 Flev 57 the open window s sill and shoot the same i scene consistently This photo is an exampl
12. auxiliary terminals that actuate under certain conditions One use for this feature is to turn on a small fan to exhaust hydrogen gas from the room while flooded cell batteries are charging Or you could have the system sound an audible alarm if battery voltage drops below a certain level or turn on a small light under some other condition Even though these bonus features might be located in the inverter or charge controller you use the system controller to configure them Provide easy access to a solar array Recall from Stuff falls on solar panels that sometimes you might need to walk to a ground mounted solar array to clear leaves or snow Hopefully you can walk up to the array with a push broom or rubber edge floor squeegee http www homedepot com p Unger 22 in Moss Rubber Floor Squeegee with Poly Propylene 961350 203177376 Uho833 wVuA on a long handle even in deep snow If you use a ladder to reach a PV array on the roof think seriously about how you will do this after a snowstorm Is the ladder directly beneath the solar panels Where will you rake the leaves or snow Consider driving a permanent stake into the ground and tie the bottom of the ladder to it each time you go up This eliminates the need to find non slippery non muddy footings for the ladder Also use a ladder stabilizer http www wayfair com Werner Aluminum Ladder Stabilizer AC96 AC96 L2988 K ZNB1064 html refid GX21919339860 ZNB1064 amp device c
13. charge controller and battery monitor inside the load center plug into this hub Circuit breaker box One of three breaker boxes installed when this house was built it is wired to the inverter s 240VAC output and feeds all branch circuits designated for solar power High power and non solar branch circuits are wired to the other two breaker boxes out of sight to the left of the solar box labeled secondary in the photo Planning A Solar Power System The Complete System Page 83 Generator auto start module Located to the right of the charge controller the small white object with wires sticking out is an electronic module that allows the inverter to start a 6 5 KW diesel generator if batteries discharge to a certain level The following sections discuss these components and now to plan for and install them Inverter The inverter converts the DC voltage from your battery bank into AC voltage for your house Location The inverter should be located close 3 4 to the batteries and fairly close to the circuit breaker box that houses branch circuits intended for solar power Many inverters are designed to hang on a wall using a bracket that bolts to studs behind the wallboard so you should have some free wall space Figure 27 shows an Outback Power 8 KW Radian inverter hanging on its wall bracket peeking out behind the left side The system controller is attached to the left side of the inverter and the cha
14. conjunction with Part 1 if you prefer but first read the remainder of Part 1 to get an idea of how many panels you will need and the space they ll require Look around Go outdoors and look at south facing locations on your house or in your yard You are interested in the sun s position at solar noon page 5 plus two hours before solar noon and two hours after solar noon Remember that solar noon is 1 00 PM clock time when DST page 5 is in effect So go out at 10 00 noon and 2 00 when DST is not in effect or at 11 00 1 00 and 3 00 when DST is in effect Take a camera and snap some photos that show if the area is in full sunlight or if there are shadows from trees or structures such as a garage a roof dormer etc Ideally you will find an area that is in full sunlight at all three times If so great The season affects shadows so don t be too concerned if there are shadows in morning or afternoon You ll need to do the full year long Site Survey Part 2 to learn if they might be a problem The important thing is that the area be in full sunlight at solar noon If you see shade at solar noon that location is not suitable find a different site Stuff falls on solar panels Do not locate your solar array directly under trees where storm broken limbs can crash into the panels Panels use tempered glass on the front for strength but a heavy branch could not only shatter the glass it could bend the aluminum frame a
15. 46 were too heavy and unwieldy for the truck driver to put on the lift gate and lower to the ground even with a pallet jack So he handed them to us one by one followed by the pallet then we re stacked them on the pallet on the ground If you aren t ready to move them to the final destination they can remain on the pallet indefinitely if they don t obstruct your normal household activities Even if the PV panels stay where they were unloaded eventually you ll have to move them to the array site How will you do this They have aluminum frames and glass fronts so they must be handled carefully Two people can carry a 60 pound panel without damage but is there an easier way Do you have a trailer or a pickup truck so you could load and transport some or all at once Inexpensive hand trucks can carry 500 600 pounds http www harborfreight com material handling hand trucks heavy duty hand truck 95061 html Use caution on hills or stairs For smooth flat surfaces like a concrete driveway or patio a four wheel dolly is a good choice This one can hold 1 000 pounds http www harborfreight com movers dolly 93888 html A tractor with a front loader bucket can carry heavy What we did items Do you own one or know a friend who has one We used our Enlist help to handle heavy items Even after they are subcompact moved from the unloading point you will later need to tractor to move hang the inverter place batteries
16. 60 6 5 KW diesel generator steel fuel tank The generator can be remotely started by the system controller if the batteries discharge below 5096 and the tank holds enough fuel to run the generator for 475 hours at full load longer at reduced power Figure 60 shows the generator but not the plastic doghouse we eventually installed over it or the 275 gallon tank The permanent electrical connection is on the left The low voltage remote start wire exits the conduit service head near the ground Work remains to be done at this writing August 2013 We need to plumb the tank to the generator and take a closer look at whether the plastic doghouse is ventilated well enough for the generator not to overheat and the doghouse not to melt Load center I can t speak highly enough of the factory wired load center for the Outback Power Radian inverter Figure 61 This saved enormous time effort and confusion The installation instructions for the inverter we originally considered http www outbackpower com index php outback products inverters chargers item sealed gtfx2524 category id 444 were very intimidating so having no experience with solar power I jumped at the opportunity for something simpler However not everything went according to plan There are three different types of load centers and we ordered the one wired for solar power not either of the other two models for custom systems Figure 61
17. 8 PV power potential 3 43KW PV power actual 3 43 KW 12 00 Azimuth 190 Elevation 61 PV power potential 385KW PV power actual 385 KW 1pm Azimuth 209 Elevation 58 PV power potential 3 33KW PV power actual 3 43 KW 2pm Azimuth 230 Elevation 0 PV power potential 2 55KW PV power actual 0 00 KW 3pm Azimuth 246 Elevation 40 PV power potential 1 64KW PV power actual 1 64 KW 4pm Azimuth 258 Elevation 29 PV power potential 0 82KW PV power actual 0 00 KW an Figure 64 Sun Angle Calculator program System monitor program After we commissioned the system I wanted a better way to monitor its performance than the system controller s browser page Figure 65 Planning A Solar Power System The Dodd Kurylo Solar Power System Page 121 PV Output 1770W Selling I 06 kW Charging 00 KW AC Load i 0 6 KW Status Battery 99 charged 0 7 ADC Current Battery Charge Charge Current Battery State of Charge 99 Channel A 29 1 ADC Min today 99 Channel B 0 ADC Days Since Full 40 9 Days Channel C 298 ADC Net Battery Ah 1 Ah Net 0 7 ADC Net Battery Kh 0 01 kWh Figure 65 System controller s browser status page My solution was to write a program that resembles a power station control panel with analog meters D Solar Power Monitor Utility KWH Aupet 1 200 Ov This month Today Aupat 13 2013 M4 Prev month Prev Day System status at 2 21 PM on August 13 2013
18. KWH button in a moment The KILL A WATT s major benefit is the convenience of directly reading power consumption but you also can use it to avoid Ohm s Law calculations with some appliances especially those having motors These list current amps instead of power watts on the nameplate Without the KILL A WATT you would need to use the power formula introduced on page 7 which is P Ex I Figure 5 KILL A WATT power or power equals voltage times current monitor in use Example If an appliance s nameplate lists 120V and 9 amps you would need to multiply these values together to calculate the power of 1 080 watts With the KILL A WATT you can read the power directly The red KWH button is used to accumulate power consumed over time Press it to display the power consumed since the appliance was turned on Press it again to switch to a timer that shows how many hours and minutes the appliance has been on Hold it to reset the power on timer to 00 00 Example Suppose you want to know how many hours per day your family watches TV and how much power was used during that time In the morning plug the KILL A WATT into an outlet then plug the TV into the KILL A WATT and turn it on Press the Watt button to see how much power your TV draws so you can write it in your power audit table on page 18 or your spreadsheet Use the TV normally throughout the day Planning A Solar Power System Getting Started Estimating Electrical Loa
19. Load center for Radian inverter Planning A Solar Power System The Dodd Kurylo Solar Power System Page 118 Unfortunately the manufacturer had put the wrong load center into a correctly labeled carton so we got a custom model Compare Figure 62 with Figure 61 above At first I didn t notice this but after reading the installation instructions several times I concluded something was wrong Circuit breakers were missing and there weren t nearly enough pre cut wires in the cabinet After calling our vendor and emailing some photos he and the manufacturer agreed that the manufacturer would ship me the correct load center It was a relief when it arrived and all the components were present Every wire was labeled with its purpose It was a pleasure to grab a bundle of pre stripped wires push them through a bushing into the inverter and have them all fit right into their terminals without any hassle at all The only glitch involved connecting the charge controller The installation instructions and actual mounting holes offered the option of attaching the charge controller to the right side of the load center or to the right side of the inverter I chose the inverter so its display would be at eye level But the wires in the load center as well as the supplied conduit were too short They would reach a charge controller on the side of the load center but not one on the inverter Fortunately t
20. Survey Part 1 you found a suitable site for your solar array and in Choosing Solar Panels Part 1 you identified candidate solar panels that will fit the chosen site Now it s time to refine the site survey A complete site survey requires a full year to complete because you need to observe and photograph how sun and shadows fall on the site for 12 months Here is the process 1 Find your location s latitude below 2 Find true north below 3 Learn how panel orientation affects solar energy collection page 51 56 4 Learn about the sun s movement through the sky page 54 5 Find the minimum and maximum heights of the sun at solar noon in summer and in winter page 54 6 See why summer isn t necessarily the season to harvest the most solar energy page 55 7 Discover the useful sun chart page 56 1 Learn how to conduct a year long site survey page 64 2 Calculate a tilt angle for the solar panels page 52 Finding your latitude You need to know your home s latitude in order to determine PV panel tilt Latitude is defined as the number of angular degrees that your location is north or south of the equator Angles are expressed in degrees minutes and seconds abbreviated DMS Sometimes just to make things more confusing angles are expressed in degrees and fractional degrees A minute of arc is 1 60 of a degree and a second is 1 60 of a minute or 1 3600 of a degree We care only about the degrees and minutes Exa
21. again and have a serious conversation Describe the full system and ask for opinions or advice By this time you should have a good idea what you want but the vendor might have suggestions that could save some money or make the system better or simpler to install Ready to build The last step is to actually order the equipment and build the system How do you proceed Will you build it yourself or hire a professional installer Will you need a building permit Buying the equipment A professional installer probably supply the equipment but you must order it if you plan to build the system yourself How will you pay for it Your solar power system is likely to cost thousands of dollars so decide well in advance about how you will pay for it Do you have cash in the bank you can wire to a vendor Will you put everything on credit cards Will you get a bank loan Can you finance through a vendor Know how you will pay before making a deal with the vendor Planning A Solar Power System Final Steps Page 104 Let s make a deal By now you should have collected prices from several vendors on the equipment you want Call each vendor and ask for a package deal Can he offer lower prices if you buy everything at once from him Is there any break on shipping Make it clear you know what you want and are aiming for the best price Ask the vendor to email you an itemized quotation including shipping costs Don t stop here Compare
22. ait 102 LIRE 102 LIVIUS 102 Install and use the solar breaker box early 1er serene eene enn nne n renean annus 102 Calculating inverter output CUETOTIL aue costed otros ip EEF aere eres cczba ka Sessa S saca RPM M SERM a aaia 103 Feeding grid power to the solar DUX cines au n kann ripe Qa os ca onse Qe np o Seba cre Sopas cR cRa ca case iaaii 103 Pretend you re on solar power for awhile 11e eere ern e enne r rennen nnnm annu nnnau 103 Provide for feed cables into a new NOUSEC L ccceeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeseeeeaseesaaeneseeesseeees 104 Example wiring CLAS AIN os cci eaaa En FER EE Eee e Eaa Eaa aaa aeai 104 Grid te consideratione nienie aaaeaii eandis adan Raise ER 105 Is theinverter capable suere tetto sen ascr enr nac a n coy eru v aaa KAKAVA FEE earn FE NSSE rand do aou a Eo 105 Utility permission or approva l uus snis riiuieus beue FERE M abore UEM FEYEFE Ve EK ECEN NEA YMO hdi HI Enn PS ni 106 Lir 51 eT S UIRRCRORRIHRURN 106 Ouiside safely CS COMING CU riae vatild ul ta PRAE eE i EA ERR SUE FED a VERLUST aatar 106 System configuration Tor Selling DOWOF u carin bb dai qu E X9A PM R aXX R IRR ERX IU FX EFE SEX Ra ex Van e EREA RO AC U A 107 i c 4 1 MEME nE c 108 Bu
23. amp gclid CL6pg COmbkCFYak4AodpGEAGw at the top for extra stability Planning A Solar Power System Finishing Touches Page 111 Mark electrical outlets With a solar power system some outlets and light fixtures are wired to the inverter and others are wired to the grid Wouldn t it be nice to see at a glance which are which There are two simple ways to accomplish this Put a yellow dot on the x Figure 48 Solar Figure 49 Grid outlet ID dot outlet ID screw cover plates of solar powered outlets Figure 48 and light switches and or put a black dot on grid non solar or dark cover plates Figure 49 14 yellow dots are available at office supply stores or online Avery makes this product http www avery com avery en_us Products Labels Identification Labels Color Coding Labels_05792 htm N 0 amp Ns amp refchannel c042fd03ab30a110VgnVCM1000002118140aRCRD Or you could spray paint the screw heads yellow You can buy dark colored cover plate screws at hardware stores or paint your own black Mark only the solar or the grid plates there is no need to mark both Once your family becomes accustomed to using solar power everyone will know which are solar and which are grid Establish rules for what can and cannot be plugged into solar outlets and how to conserve power during a grid outage by minimizing use of appliances plugged into solar outlets Use a grid status monitor One drawback of u
24. as assume complete n connecting to the house wiring responsibility for obtaining them and passing the inspections If you re E ing i If it s all um a ae permit for the PV panel supports Some people consider building inspectors to be a nuisance and a The feeder cables from the PV hindrance but in fact building inspectors are your friends Almost array to the house were required to universally their goal is to ensure public your safety Approach a E M E building inspector with a modicum of knowledge which you now Duc ei Geers have and a pleasant demeanor and you are likely to be rewarded with the combiner box a friendly knowledgeable response Hire a professional installer A knowledgeable and experienced professional can do the entire project saving your hours of work and potential hassle but at a higher cost than doing it yourself Ask the installer about the type of systems he or she has installed If your system is different from the installer s history consider another installer You don t want a situation where the installer has experience with for example off grid systems but none with grid tied systems like yours Bring the installer up to speed on your planning and the equipment selections you have made The installer might be accustomed to working with less informed clients and making all the choices himself It could be unusual for a client to be so well prepared This can work
25. connect them together Figure 28 is wiring diagram showing a 48V battery bank consisting of three strings each containing four 12V batteries In this case the AGM batteries are connected with metal bars so those interconnections are drawn with heavier lines than lines for normal cables Planning A Solar Power System The Complete System Page 85 Figure 7 on page 33shows a 24V battery Negative Feed to bank with three strings of four 6V flooded M SENE Positive Feed to Guns Contele cell batteries Notice the short black interconnection cables looping between the batteries 175A Breake Notice in Figure 28 how each string connects to a 175A circuit breaker These are for safety and convenience Not only do they protect the batteries in a string if a 175A Breake short circuit occurs in the cabling or connections very unlikely they also Negative Terminal Block Positive Terminal Block provide a way to switch out individual banks for maintenance such as when checking the tightness of connections or 175A Breake replacing old batteries Three similar circuit breakers can be seen in the upper right corner of Figure 7 Figure 28 48V battery bank wiring diagram Figure 29 shows one string of the 12V AGM batteries diagrammed in Figure 28 Notice the metal bars instead of cables to connect adjacent batteries Also notice the red cable on the right and black
26. convert sunlight into electricity These PV or solar panels often are mounted on the roof of a house but they also may be mounted on a framework installed on the ground The panels must be tilted to face the sun The tilt angle is always a compromise because the sun moves across the sky from east to west during the day and changes maximum elevation during the year Some people install their solar panels on tracking mounts which use motors to follow the sun s movements These trackers add considerable cost to a system PV panels are rated by the number of watts of power they can produce when pointed directly at the sun You can buy panels that produce as little at 1 watts but those suitable for a household system range from about 150 watts to 300 watts Typical prices in 2013 are about 1 25 per watt so a 300W panel costs about 375 A single PV panel isn t enough for most systems so multiple panels are wired together in an array to supply more energy The number of panels depends on the amount of energy you want to harvest and on the power rating of the individual panels Example Assume you want a capacity of 5 000 watts and you choose 200W panels You ll need 25 panels If you choose 300W panels instead you will need 17 Determining the required number of PV panels is slightly more involved than this and will be discussed in detail later Combiner box A combiner box is required by the National Electrical Code to wire
27. how it has worked out after a year of operation A complete diary with photos of the construction project is on our family website where you found this document http house mdodd com update_solar html The solar array Our house is surrounded by trees and the only clearings are the septic field and a one acre clearing for an astronomy observatory The observatory clearing has more open space but it is 300 from the house We d need to dig a trench for that entire length and cross the utility s buried electrical power line to the house We considered installing solar panels on the house roof but the house is round and each of the 18 roof segments has space for only three panels Plus the segments are 20 apart so the entire array would never face the sun at once Finally the house has tall trees nearby to the south so that alone makes it ill suited for solar panels Figure 52 Our round house sout isto the le t So the septic field it was The clearing is large enough for good sun much of the time but morning and afternoon shadows cut solar harvest by 25 from what we could expect with a clear horizon Oh well it is what it is We have 14 290 watt panels wired as seven pairs to provide a nominal array capacity of 4 KW You ve seen some photos of the array earlier in the document and more are shown below Planning A Solar Power System The Dodd Kurylo Solar Power System Page 114 Making power in shade or
28. in their final location heavy objects and gently lift large PV panels onto their mounts It TU EISE 3 Figure 4 7 Tractor carrying basement door inverter is 100 from the might be possible to do these tasks by yourself but consider the consequences of an injury and the cost of replacing a damaged or broken PV panel or inverter E a IT E Always err on the side of caution dolly was out of the question and using a hand truck would have been difficult The tractor saved the day Planning A Solar Power System Final Steps Page 110 FINISHING TOUCHES Keep safety convenience and ease of use in mind as you plan and build your system We covered safety earlier so if your system meets code it ought to be safe in that regard Here are some suggestions than could enhance convenience and ease of use Keep a clear path to the system Usually a solar power system operates without help from humans But occasionally something goes wrong and you ll need to hustle down and see what s going on Keep clear access to the system controller charge controller circuit breakers and GFDI and any other component that might require your attention Clear access can be convenient as well If the system controller is in the open and at eye level you can quickly glance at the display to see ho much power is being harvested and used or sold Take advantage of bonus system features Some inverters and charge controllers have
29. is this Solar cells inside a panel are wired in a series parallel configuration The panels in Figure 17 and Figure 18 have six strings of 12 cells If any part of a series string is interrupted current stops flowing through the entire string Planning A Solar Power System Site Survey Part 2 Page 66 Bypass diodes To prevent a shaded cell or cells from disabling the entire panel bypass diodes are installed to allow current to bypass the shaded strings and flow through the pane This improves efficiency by allowing the unshaded strings to produce power The first part of this article explains how bypass diodes operate http www digikey com us en techzone energy harvesting resources articles active bypass diodes improve solar panel efficiency html the last part is fairly technical As the article shows pairs of strings can be bypassed allowing the unshaded strings to produce power Summer Look at Figure 17 showing 14 PV panels wired as seven pairs The pairs are indicated by the numbered yellow ovals This shot was taken at mid afternoon in late August Only panel pairs 2 1 10 9 and 12 11 are producing full power Panels 6 5 and 8 7 are nearly Figure 17 Summer shadows on PV panels completely shaded so they are producing no power On the rear row 14 is disabled by shadows but 13 is mostly unshaded so it can produce nearly full power On the front row 4 is disabled by the shadow that cove
30. limit how much current batteries can supply Battery characteristics A solar power system places high demands on batteries so special deep cycle versions are used instead of regular automotive batteries There are two basic types of batteries for solar power systems wet cell or flooded and sealed A wet cell battery contains lead plates submerged in cells internal containers of sulfuric acid and water the electrolyte Hydrogen gas is released from the battery as it charges and this gas must not be allowed to accumulate in a closed room or an explosion might occur Water is lost during the battery s charge discharge cycles so you must replenish this water periodically A sealed battery has either a gelled electrolyte gel cell or has electrolyte absorbed into a fiberglass mat between the lead plates absorbed glass mat abbreviated AGM Sealed batteries like these don t release hydrogen nor do they require periodic water replenishment Batteries are charged with solar energy through the charge controller and supply DC power to the inverter to be converted into AC house power Sidebar continues on next page Important You will get only half the stated capacity from any battery Read the yellow But Wait sidebar below to find out why Planning A Solar Power System Choosing Batteries Page 30 Battery capacity in KWH Amp hours aren t very helpful for our
31. multiple PV panels together The combiner box contains a circuit breaker for each PV panel and its output is connected to the system charge controller see below A combiner box also might have a lightning arrestor wired to a nearby grounding rod Batteries Many but not all solar power systems include batteries to store energy from the PV array for use when the sun is not shining If you don t have batteries your system can provide power only during sunny periods Usually batteries are lead acid types similar to the one in your car A solar power system places high demands on batteries so special deep cycle batteries are used instead of regular automotive batteries Batteries are discussed in depth in Choosing Batteries Planning A Solar Power System How a Solar Power System Works Page 13 Charge controller For maximum life batteries must be charged in a tightly controlled manner and this is the job of the charge controller The electrical output from the solar panels through the combiner box is connected to the charge controller This electronic device senses the batteries state of charge and supplies solar energy to recharge them usually in three distinct stages For the most part the charge controller operates automatically without any intervention You might have to turn it back on after a rare incident where a DC circuit breaker tripped and has been reset Inverter The inverter s job is to convert DC
32. on the height of the post Once the posts were plumbed we dumped half a bag of dry concrete mix more for Two sets of supports support one row of panels We drilled the mounting holes in the 2x4 rails in advance and drove in 4 x 4 galvanized carriage bolts We planned to lift a 60 pound panel and place it over the four bolts in the two rails in one operation It was vital to get the rows spaced accurately so the bolts would line up precisely with the mounting holes in the PV panels To achieve this we made a template from cheap 5mm Luan plywood glued amp F into an X shape with holes drilled exactly at the four corner hole Figure 59 PV support spacing template locations of a pair of PV panels We placed the two front posts in their holes positioned the template over all four bolts and set the front posts with concrete This approach worked extremely well All panels dropped right onto their bolts Planning A Solar Power System The Dodd Kurylo Solar Power System Page 117 Generator One of our reasons for building the solar power system was to have a long term source of power if a calamity should befall our society and the grid goes down for weeks or months We knew that solar power couldn t provide all the power we need over the long haul Our locale can experience a week or two of clouds so we needed a backup to the backup Our solution was a 6 5 KW diesel generator and a 275 gallon Figure
33. or want to live in a remote location where commercial power is expensive or not available at all An off grid page 7 solar power system can provide all the electricity your household needs especially if you avoid high power appliances like an electric stove oven water heater or clothes drier A wood stove can provide heat in winter and shade and open windows in summer can substitute for air conditioning Most likely you will place a high value on solar power if this is your lifestyle Reason 4 Selling power It s appealing to think you can supply electricity to other homes in your community not to mention being paid to do so Do your research thoroughly if you re considering this Here s why In many areas of the country you can install a grid tied page 6 system that supplies solar power to household appliances and sells surplus solar energy by feeding it backward through the meter But in other areas if you want to sell power your system must be designed from the start to oz y sell power The utility installs a special electrical meter to measure the outgoing power and a of your system s power must be sold you can t use any of it to run your house Furthermore the utility considers you a small generator and pays only wholesale rates for your power In the former arrangement where the meter runs backward you re paid or credited at the retail rate listed on your electric bill Reason 5 Green energy No questi
34. power audit table Use Table 3 or create another spreadsheet to list appliances that will remain connected to the grid and not be powered by solar Notice that the total at the bottom is omitted We don t care very much about how much power Our choice heating appliances these appliances draw because they re already wired to a grid We installed an electric water heater connected breaker bor cooktop oven and clothes dryer when we built our house knowing that none of The main reason for this grid power audit is to clearly these can be used during a power outage identify appliances that will not be connected to the solar BP 5 Gas appliances would have avoided this power inverter Include high power appliances but also nuisance but we chose not to use gas anything you don t care about during a power outage such as Planning A Solar Power System Getting Started Estimating Electrical Loads Page 19 outdoor floodlights patio outlets or outlets in a little used bedroom Don t bother entering the load for these items just list them for future reference This table is useful for another purpose removing items from the solar power audit table above to reduce the total solar power load and use a smaller inverter This is explained in Fine tuning the inverter size on page 24 Don t just delete the item copy its full information here so you ll have it if you later decide to move it back to
35. purpose In the solar power audit Table 2 you found appliance loads in kilowatts and the number of kilowatt hours KWH each appliances uses per day It would be nice to know how many KWH a battery can supply so we can determine how many batteries are needed How do we get from amp hours to kilowatt hours As you saw in the power formula on page 7 watts are calculated by multiplying voltage and current P E x I Example if a 12V battery is delivering 15A to a load it is delivering 12V x 15A 180 watts Since kilowatt Zours are obtained by multiplying power by time we know that if the battery delivers 180 watts for 10 hours it has delivered 180W x 10H 1 800 WH or 1 8 KWH But can it do this At 15A the battery has supplied 150 amp hours over the 10 hours If the battery is rated for 300 AH it is now half discharged So the basic calculation is to take the battery s amp hour capacity and multiply it by the battery s voltage to get the number of KWH the battery can deliver Example a 12V battery rated at 200 AH can deliver 12V x 200 AH 2 400 WH or 2 4 KWH 1 200WH or 1 2 KWH Battery characteristics continued Batteries are heavy and costly You will probably need multiples of them and a sturdy place to set them You can buy batteries designed specifically for solar power systems or buy batteries intended for marine golf cart or other deep cycle use Each cell in a lead acid battery produce
36. solar energy reach the SYSt Irm sssssscssssscsscsssssssossssccsssssssessecssssecssseesssesessessnerens 83 Li Il o e 83 Cables from the array Io th SysLe Poussin eU YR RRFIUKU SFO RUFI VAPEO EU UCEQUTI UPU II RAE UE FDY PRU 84 he Complete System ji C UT 86 Enc e 86 tgp mE a a 86 olm 87 cc clade qj e 87 Cables and CONNCCHONS See 88 j p 88 Making CONMCCHOMNS e 89 Dur choice make a CHINDINE IGOL sitos Wed d pin iH EPHRAIM C VEXE SEC HII CERE UR 89 Tie points TOF multiple cables m 89 Egual cable D aln RR 90 bl4doLEcud go rime 91 Our choice sigle tie polisinin i HpNREH IA PA EIREH E UD aan PEL Rd EUR 92 cep m 93 icu ico MT 94 lar e 94 peo E Ee riz Rcg pe m 94 Load GEM Eiss e OS a A 95 Our choice a factory wired load CeNtel scssscsssssssesssessssecsscrssses
37. supports along the center line Single row supports should be fabricated from welded metal a bolted wood framework will quickly loosen and lose stability and alignment Figure 19 shows two rows of wooden PV supports The posts are 4x4s and the horizontal members are 2x4s The 4x4 posts are set in 8 diameter holes and anchored with concrete A footer footing is a concrete base to support a structure A wooden framework made of dimensional lumber doesn t need concrete Figure 19 Wooden PV panel supbo n footers unless local building code requires them But a commercial mounting system may well require a footers under each support Check with the manufacturer or vendor about footer requirements before choosing a ground mounting system One row or more You can install PV panels in more than one row if space is Our choice ground mount two rows The roof of our round house is not limited The main consideration is that the front southernmost row not shade the row behind it This is suitable for solar panels so we installed simple to check during planning You need to know the sun s uiemontuorowtondomensdewoodcn noon elevation on the winter solstice which you entered on ground mounts Details of this part of the page 55 This elevation must be higher than the angle from the project are on our family website at http house mdodd com update_solar ht can sketch this to scale and measure the angle with a ml PVs
38. the files will be sorted when listed in a file explorer Likewise put the time and serial number if any at the end of the name to sort multiple images on the same day There is no need to save the images of the slips of paper 5 Take notes Photos show a lot but they don t necessarily tell the whole story Often you might notice something that could prove helpful in the future Take a notebook and record the date and time plus anything you think might be valuable later 6 Review the information At the end of the year but not necessarily only at the end of the year look over your photos and notes Does it appear that your site receives good sunlight throughout the year Here are some things to look for 1 Shadows fall in different places throughout the year due to the sun s varying path across the sky 2 Leafy trees in summer cast denser shadows than bare trees in winter 3 Even though the December June sun path is the same as June December but in reverse the shadows will vary because leaves grow in spring and drop in fall at different points in the cycle You can t assume that December June shadows will be the same as June December shadows Let s talk about shadows Shadows cut solar power production more than you might expect Winter shadows are especially deceiving Even though it looks like plenty of sunlight is falling on the array the long thin shadows of bare trees can completely shut down an entire panel The issue
39. the solar inverter oe requires a mechanical interlock that connects to the solar breaker box through a branch F allows only one of these feeder circuit breaker which feeds all other branch circuits in the te circuit breakers to be turned on at box then the generator can connect to the same box once It must be absolutely impossible through a similar branch circuit breaker and feed the same ie connec 40V AC oarpu tab other branch circuits T he breaker box and appliances don t i the generator to the inverter s output care whether the power comes from the solar power system P P y or to connect the 240VAC inverter or from a generator i output generator Doing so will Read the warning in the adjacent sidebar Your damage or destroy one or both devices electrician should know about mechanical interlocks to allow only one breaker to be on at a time Do zo connect a generator to the solar breaker box without an interlock Manual or automatic start You can start a generator yourself or let the solar power system do it At minimum you can walk and pull a starter rope Better would be for the generator to have its own battery and an ignition key like a car Turn the key and the generator starts Still better is to run a cable from the ignition switch into the house so you don t have to walk outside inevitably at night in inclement weather Planning A Solar Power System The Complete System Page 97
40. to west across your time zone Read the information on page 5 about finding solar noon 3 Before solar noon drive one stake into the ground and tie one end of your string or tape to it Important Drive this stake as close to vertical as possible Use a level or plumb bob to check If it tilts the shadow it casts will be inaccurate 4 At exactly solar noon drive the second stake at the end of the shadow cast by the first stake This second stake will be due north of the first stake Tie the free end of the string or tape to the second stake This is your true north south baseline save it Leave the stakes and string in place for future reference In Figure 13 a white PVC pipe was slipped over the first stake to identify it for the photo and to cast a broader shadow 5 Finally transfer the north south baseline bearing to your compass Stand to the south of the first southern stake and sight across the compass base to the northern stake If you used steel stakes e g rebar stand well back from them so the metal doesn t affect the compass needle Rotate the compass dial until the arrow is aligned directly under the compass needle as shown in Figure 12 Repeat this procedure until you are positive that the compass needle is correctly aligned with its arrow while the compass base accurately lines up with both stakes Leave the compass set this way until the solar project is finished If necessary tape the dial in place If you
41. with two SolMeister inverters what else is needed to stack them and how much does it cost The vendor might suggest an inverter far too large for your loads Don t hesitate to say so and ask for something closer to your requirements There is no need to pay for capacity you won t use On the other hand the larger inverter might have benefits that are not obvious or might cost only slightly more than two smaller inverters and stacking components The 8 KW EZ PZ inverter sounds like more than I need Why is it a better choice than stacking two of the 3 KW SolMeisters Well the EZ PZ is fully integrated into one cabinet so it s much easier to install The SolMeister needs a cable raceway two junction boxes etc etc Plus the EZ PZ costs only 20 more than two SolMeisters once you add the stacking components Remember to ask about the inverter s input voltage What input voltage do these inverters use Are there models that use higher voltages If so tell me about them including prices Planning A Solar Power System Choosing an Inverter Page 27 The EZ PZ runs on 48V and is available only in the 8 KW model You can get the SolMeister for 24V and for 48V with not much difference in price If you plan to stack two of them for 6 KW I d recommend 48V Don t hesitate to ask other questions Tell the vendor you re learning about solar power and just getting started with the design Ask for the salesperson s full name phone numb
42. you can do it from the ground Walk away from your house until you have a clear view of the roof Sight along the level until it exactly aligns with the roof then read the angle from the level This is the angle up from horizontal so subtract it from 90 to get the tilt angle for PV panels For example if the roof angle is 27 angle a 6 12 pitch roof the PV panel tilt angle is 90 27 63 If your panels should be tilted 63 you can mount them flush with this roof If not you ll need an adjustable mount Given the wide variety of roof mounts and the scarcity of detailed information and photos on the Web discuss roof mounts extensively with vendors On the ground There are several varieties of ground mounting systems so vendor help is needed for these as well Some systems use a single row of poles along the center line to support the panel framework such as this one http www solarelectricsupply com solar panel mounts ground mounts dpw multi pole Others like this one http www bluepacificsolar com home solar ironridge ground mount html use two rows of supports near corners or edges Planning A Solar Power System Choosing Solar Panels Part 2 Page 69 You can of course build your own ground mounting structure from pressure treated dimensional lumber Support posts must be set in holes ideally with concrete for stability A wooden structure with two rows of supports is better than one with a single row of
43. 1000 KWH KWH 10 Target battery bank voltage from 4 VDC 11 _ No of candidate batteries in a string see text 12 Battery string capacity 5096 DoD see text KWH 13 Number of candidate battery strings in bank 14 Number of candidate batteries in bank 15 Candidate battery bank capacity KWH 16 Candidate battery bank run time see text Days 17 Candidate battery cost Each 18 Candidate battery bank cost 14 x 17 Table 6 Candidate battery information Instructions for Table 6 The left column in Table 6 contains reference numbers to make it easy to explain how certain values are calculated or where they come from 1 Enter the daily appliance load from your solar power audit Table 2 on page 19 This is the number of KWH per day consumed by those appliances 2 Enter the number of days you want to run the solar appliances from batteries as discussed in How much battery power do you need 3 Multiply 1 and 2 to get the target size for the battery bank For example if your daily power usage is 8 KWH and you want to run on batteries for two days your battery bank s target size is 8 KWH x 2 days 16 KWH This is a target you might not be able to hit it 4 Enter the nominal DC input voltage for the inverter you selected into the DC input voltage column in Table 4 on page28 This voltage will determine the number of batteries you must have in a string Planning A Solar Power System Choosing Batteries Pa
44. 35 is 0 819 Remember this number the azimuth cosine The panels are still tilted at 40 but now the sun s elevation is 64 64 elevation 40 tilt 24 The cosine of 24 is 0 914 which is the elevation cosine Next we multiply the azimuth cosine 0 819 by the elevation cosine 0 914 to get a true factor of 0 749 Only 74 9 of the sun s energy is captured one hour after solar noon on this particular date at this particular location and with this particular solar panel azimuth and tilt Introduction to solar panel tilt Solar panels are tilted to face the sun There is no optimal tilt angle for the entire year or even for every hour in a day Any fixed angle is a compromise Planning A Solar Power System Site Survey Part 2 Page 52 Tilt angle clarified or confused Not surprisingly the amount of PV panel tilt is referred to as i angle This document uses tilt angle to mean how many degrees a sun facing solar panel is tilted backward from vertical So if a south facing panel is standing vertically facing the horizon it has a tilt angle of 0 If you lean it backward 25 it has a tilt angle of 25 There is a reason for doing it this way Call this Method A Some websites use tilt angle as how much the panel is tilted from horizontal With this terminology if a panel is horizontal looking straight up its tilt angle is 0 If you tilt it 65 toward the south it has a tilt angle of 65 Call t
45. DE E 23 Choosing an Inverter Determine an approximate inverter size ceeecc cce Leer creen rennen nene nena nnn 24 gduzi ldi g qo 24 Ue ATS MUNI oo cool fec PET 26 Choose a candidate INVENTED scanned oap t QURE tH A CUR MW DK HA MK Fei 26 Call vendors Tor informatio ossiace rarmictnia stib ipii asbl E dpum FU D cu P Mu EN IR DU ORA KEEN LR RE RM EIE 27 Where d Rin doo d sete 28 Multiple batteries increase capacity 1 cere ccce Lc Lrrrceeeee nena nnam tnnnn 32 How much battery power do you needY eese eere cesis nennen een a nenas annm ea nnne ns 34 identifying candidate Ballelfesi used perii t PH DEFREPEQUdH b n E E itd uw FA FR ERR ER t Raid 34 Candidate battery SICHIAHOFIB visvipvivibie NH FR KE HIR FEMININE REVENU EIREN ERUNT VERE FPNKU V R ER UERS 35 Instructions for Table 6 near e cm Rer eMe cua vase esa aee eu exe coe etna uo aa 36 How many UIST SINES E usos adonde PEE Lr PUPPI Ra Qu F IM RRUA SN SVFOUIS IW VEM dS 38 Hitting the target storage Capiaclby uuuaeee eae neta tance so PraE e PRSE nan E nb Foe Eek epa Pa En UbRa pns aDa bassa nep rA 40 Site Survey Part 1 LOOK AOUN MR CKMC pP e eee orca er 42 Stufi fals os Bob panelo ciii boi Edo Pon uic ia i Dx P CELL EE 42 How many panels do you nee tussis inpia tiii xU FRE R
46. Each panel you add to a series string adds its Voc to the total Voc Here are the steps to see if N panels in series will work with your candidate charge controller Planning A Solar Power System Choosing Solar Panels Part 2 Page 73 1 Find your candidate PV panel s Voc from the data sheet Write it here VDC 2 Find the charge controller s CC maximum input voltage Write it here VDC 3 Find the temperature factor either from the PV data sheet of from the charge controller owner manual Write it here temperature factor 4 Multiply the PV Voc 1 by the temperature factor 3 for a panel s temperature adjusted Voc Write it here VDC 5 Write the number of candidate panels in one string 6 Multiply 4 by 5 for one string s temperature adjusted Voc Write it here VDC If the temperature adjusted PV string Voc 6 exceeds the charge controller s maximum input voltage 2 there are too many panels in one series string Decrease 5 by one panel and recalculate 6 Do this until 6 is less than or equal to 2 at which point 5 contains the number of panels you can have in one string Don t fret if you need M panels in your PV array but a string can contain only N panels You will connect multiple panel strings together in the combiner box so the array can be as large as necessary If you discover that N panels in a string would work if each panel s Voc were lower search for a panel of the same wattage but with a lowe
47. IED GEH eR el Va RO Fe Fei RA ERI i 44 The charge controller TactOl osse per His EUH Gd e RR PEE PORE QU RERQUUDO enn 44 Will ENE panels fit my tir TTE reme 45 What if the panels dont tit onore E etre tendere dei eI Ee eere Epitt i b nannies 46 Choosing Solar Panels Part 1 Site Survey Part 2 gun amp cl i i rs H 49 Fdinne Te Got TT 50 Use a compass een REED PEE PvE EE en rete od ctsus ciis su UE ErRORCH SESS Er ves EeerE IS 50 Use stakes and a SITadQoW 22 2 aeicece ru rede creep ndn erue aae a stack cassie leccstsccacegncasacsiesaasceeteedtsdeaviaciie 50 How much solar energy does a panel collect eese 51 Basic surmcaleulatioris ioi a I Pd tor ies ess eect eid ies 51 introduction TO SOIR AMG Bi fem 52 Tilt angle clarified Of COnfliSed ooo iioc ria coena ra Ecce ioca ree cacedesstdisaccens sais avec eagebah cewecet tei 53 How latitude affects sun elevation eeeeeeeeeee enne nnne nnnn nennen nnne nnn nnn 54 Sun elevations at your locatio MeR 54 Which season gives the most solar energy Important eese 55 Visualizing WiN a I CE pr EO oM 56 Choosing a Ruhr Er ESTE RE T 58 Adjustable MOUNtS C 58 Our choice qao e 58 Compari
48. Power System The Dodd Kurylo Solar Power System Page 123 That s it I wish you success on your project Please let me know how it goes and send a URL if you post photos and information on a website or blog Please ask before emailing photos because there is a monthly bandwidth limit on my rural Internet service My email address is mike mdodd com Planning A Solar Power System The End Page 124
49. Radian and eliminates many interconnection components needed by the older inverter The load center greatly simplified the system wiring Frankly having no prior experience with solar equipment I was intimidated by the older inverter s installation and hookup instructions Planning A Solar Power System Choosing an Inverter Page 29 Cuoosine BATTERIES It would be nice if we could get on with the solar part of the project and save batteries for later but you should know how much energy storage you need before you choose solar panels and decide where they will be located So batteries it is Let s first learn about battery capacity and then find out how much power you want the batteries to supply Finally we ll discuss types of batteries along with relative costs and benefits Battery capacity explained A battery stores and produces electrical energy by means of chemical reactions To learn more about lead acid batteries check out this Wikipedia article a ae a The capacity of a battery is stated in amp hours page 3 A fully charged battery with a capacity of 50 AH can deliver a current of 1A for 50 hours before becoming completely discharged If the load draws 5A the battery will become discharged in 10 hours If the load is 10A the time until discharge is five hours Does this mean the battery can deliver 50A for one hour or 100A for half an hour Probably not Internal properties
50. Read the next paragraph for why you might need to do this You will need longer cables to reach the combiner box below than are supplied with PV panels Extension cables are available for this purpose and how to use them is explained in the section on the combiner box Be alert to the connector designations when you buy solar panels and extension cables If some are MC4 e g extension cables and others are H4 e g solar panels you might face a minor hassle with the latch when connecting them Wiring it all together Figure 21 shows how a PV array of 12 panels might be wired In this 9 3 u v 2 a o a Charge Controller Negative Feed to Charge Controller example every PV panel has a Voc of 26V and three panels are wired in series positive to negative to make a string with a Voc of 78V We assume the necessary calculations have been performed to determine a temperature adjusted Voc page 73 If 78V adjusted for temperature is too high for the Combiner Box charge controller remove one panel 2 from each string and make two more 6 Voc Positive Bus Bar strings from the four removed panels The positive cables from all strings Figure 21 Example solar array wiring diagram are connected together in a combiner Planning A Solar Power System Choosing Solar Panels Part 2 Page 77 box below as are the negative cables From the combiner box heavy cables carry the solar ene
51. Subtract that appliance s power from the solar power total and use the lower total to size your inverter 3 Make a minor lifestyle change restrict certain appliances You and your family might have to accept the fact that using solar energy means no longer taking everything for granted One choice might be to require that certain inverter powered appliances never be used at the same time Each can be used alone but not both at once Make self adhesive labels for both appliances that say for example NEVER use the microwave and toaster at the same time This relatively simple change would reduce your inverter size by a kilowatt in this example Be careful to choose reasonable restrictions A hair dryer and a toaster are not good candidates you wouldn t expect someone with wet hair in the bathroom to ask someone in the kitchen if it s okay to use the hair dryer Similarly who is willing to walk to the basement to check if the pump is off before using the microwave Rules of thumb for minor lifestyle restrictions Restrict only high power appliances those that make a significant difference to your inverter size It makes no sense to say no TV 220W while the computer 175W is on Restrict only appliances located in the same room that are easy to check before using e Inform family members of restrictions and apply reminder labels to restricted appliances Make a note on your solar power audit next to the two applianc
52. V for volts Examples 120 VAC or 120 volts AC CFL is an abbreviation for Compact Fluorescent Lamp These light bulbs are much more efficient than traditional incandescent lamps and last longer CFLs are sold with their equivalent or replacement wattage printed on the package along with their actual power consumption For instance a 100W replacement CFL draws only 23 watts It s more useful to look on the packages and compare the ight output lumens of CFLs with incandescent lamps For example a typical ceiling light fixture can use two 60W incandescent lamps for a total light output of 1700 lumens 850 per 100W incandescent lamp But two 60W equivalent CFLs 13W apiece produce 1600 lumens 94 of the light but with just 26 of the power But wait You can use two 100W equivalent CFLs in that same fixture to get 2900 lumens a 71 increase in light Two 100W equivalent CFLs draw only 23W apiece which is not even close to the fixture s rating of two 60W incandescent lamps In fact the 46 total watts used by the two CFLs is less than the 60W that a single incandescent lamp consumes CFLs take 20 30 seconds to warm up and produce maximum light This can be annoying so you should decide if the lower power consumption is worth this minor annoyance CFLs might not operate well at low temperatures so you should shop around to find special CFLs that will work in outdoor fixtures such as porch lights One online source is
53. WH Table 13 Latitude 40 north 4 KW PV array tilt 30 Energy Difference From Date Production Dec 21 December 21 28 5 KWH September 21 amp March 21 25 7 KWH 10 June 21 12 5 KWH 56 4 day total 12 day total Jan 21 Dec 21 coe Energy Difference From Date Production Dec 21 December 21 27 6 KWH September 21 amp March 21 25 8 KWH 7 June 21 13 1 KWH 53 4 day total 92 3 KWH 12 day total Jan 21 Dec 21 276 5 KWH Table 15 Latitude 40 north 4 KW PV array tilt 40 Energy Difference From Date Production Dec 21 December 21 26 1 KWH September 21 amp March 21 25 7 KWH 2 June 21 13 7 KWH 48 4 day total 91 2 KWH 12 day total Jan 21 Dec 21 274 2 KWH Table 16 Latitude 40 north 4 KW PV array tilt 45 Planning A Solar Power System Site Survey Part 2 Page 60 Energy Difference From Date Production Dec 21 December 21 25 3 KWH September 21 amp March 21 25 3 KWH 0 June 21 14 KWH 45 4 day total 89 9 KWH 12 day total Jan 21 Dec 21 269 8 KWH Table 17 Latitude 40 north 4 KW PV array tilt 50 Energy Difference From Date Production Dec 21 December 21 23 9 KWH September 21 amp March 21 24 9 KWH 4 June 21 14 4 KWH 40 4 day total 88 1 KWH 12 day total Jan 21 Dec 21 263 4 K
54. WH Table 18 Latitude 40 north 4 KW PV array tilt 55 Energy Difference From Date Production Dec 21 December 21 22 3 KWH September 21 amp March 21 24 2 KWH 9 June 21 14 6 KWH 35 4 day total 85 3 KWH 12 day total Jan 21 Dec 21 255 KWH Table 19 Latitude 40 north 4 KW PV array tilt 60 Energy Difference From Date Production Dec 21 December 21 20 5 KWH September 21 amp March 21 23 3 KWH 14 June 21 14 7 KWH 29 4 day total 81 8 KWH 12 day total Jan 21 Dec 21 244 7 KWH Table 20 Latitude 40 north 4 KW PV array tilt 65 Planning A Solar Power System Site Survey Part 2 Page 61 Energy Difference From Date Production Dec 21 December 21 18 6 KWH September 21 amp March 21 22 2 KWH 19 June 21 14 6 KWH 22 4 day total 77 6 KWH 12 day total Jan 21 Dec 21 232 5 KWH Table 21 Latitude 40 north 4 KW PV array tilt 70 Energy Difference From Date Production Dec 21 December 21 16 5 KWH September 21 amp March 21 21 KWH 27 June 21 14 5 KWH 12 4 day total 73 KWH 12 day total Jan 21 Dec 21 218 5 KWH Table 22 Latitude 40 north 4 KW PV array tilt 75 We can we conclude several things from these tables for Columbus Ohio 40 north latitude 1 2 3 4 5 Table 14 shows that a 35 panel tilt backward from vertical yields the maximum total power on the four specified dat
55. aa gov gmd grad solcalc azel html The winter solstice is the worst case because the sun is lowest in the sky then The hours between 10 00 and 2 00 are reasonable choices for best solar collection but you might want to expand them to 9 00 and 3 00 since the winter sun can produce significant energy then It can be a balancing act If you space the rows far enough apart to avoid shadows will they fit in your available space And will they be clear of tree shadows you identified in your year long site survey page 64 Protection Safety is a primary concern with a solar power system PV panels must be securely mounted so they don t fall and injure someone or are destroyed All components in the system are high power so people must be protected from shock and property must be protected from fire The electrical code and local building codes require the system to meet certain standards Talk with your local building inspector to learn what these requirements are PV panel roof mounting Almost certainly your building code stipulates how solar panels must be installed on a dwelling roof how the cables must run into the house and how the installation must be protected against lightning Again talk with your building inspector Lightning Lightning strikes can destroy solar panels and can start fires A lightning arrestor can shunt this electrical surge to ground and is required by the national electric code Check with your local
56. able is shown in green in the diagram The electrician removed it two years later when the solar power system was built The branch breaker in the main box now feeds the inverter input and the inverter output feeds the solar box as shown in the drawing by the straight red lines to and from the inverter Grid tie considerations Recall from page 6 that as used in this document grid tied means being connected to the grid and capable of selling excess solar energy to the electric utility A grid tied inverter sends AC power produced from a renewable source e g solar wind hydro to the grid via the input cable Normally we think of an inverter putting AC power on its output cable to run appliances but in this case it puts it on its input cable This introduces several factors discussed below Is the inverter capable The inverter must be able to identify excess power originating from a green source and it must be able to apply the power to its input terminals The green factor is key you can t sell power from non renewable sources to the utility Planning A Solar Power System The Complete System Page 101 This means no power from a generator and none from batteries alone because they might have been charge from the grid or from a generator The solar array must be producing power and there must be more of it than the household requires Utility permission or approval Your electric utility wants to know if you pl
57. aight through this document or you can skip around Click your mouse pointer on a Table of Contents topic not on a page number to go directly to that topic Cross references to topics in the document are colored red such as this one to Ohm s Law Click on one to go to that spot Planning A Solar Power System Introduction Page 1 Sidebars Sidebars are yellow frames that information relevant to the main text but not directly related to it Sidebar In a sidebar you ll find relevant information that doesn t fit in the main text such as an explanation of how batteries work next to a discussion on choosing batteries Personal comments Occasionally you ll encounter a green sidebar like this one Personal comments that contains personal comments about a choice we made or This document tries to remain how or why we did something I 4 objective so our personal choices and Internet links decisions are reserved for green sidebars When a website contains in depth information on a topic scattered here and there or complete product data this document includes a link to it such as this one to a page that defines alternating current http www thefreedictionary com alternating current Click the underlined blue link to launch your Web browser and go to that page your PDF reader might ask for permission to open the website This PDF document remains open so switch back to it to resume read
58. all of the package quotes and think about which vendor you d like to deal with Which seems to offer the best support Who sounds the most knowledgeable A sales person might not have detailed technical information but gets high marks if he calls the factory for you If you favor a particular vendor call back and ask for a better price Overall your quote looks pretty good and I d like to buy the system from you but some of your prices are higher than other vendors have quoted Is there anything you can do The sales rep should ask for instances of lower prices so be prepared Be specific using vendor names and prices from the quotations If you find an online vendor advertising a lower price on something tell your vendor the URL even if you don t have a quote from that vendor You will need to compare exactly the same products except solar panels which are somewhat generic If you can find equivalent power and Voc solar panels at lower cost say so Your vendor might not In our case We got quotations from three vendors Vendor X had the best prices and we were ready to buy We called vendor Y to say so sorry but he asked where his prices were too high After we told him he beat most of the competing prices with a total around 4 less than vendor X He got the order We did not ask vendor Z for a better deal because that company did not seem very interested in our project during our researc
59. an to sell power and it What we did wants its linemen to be safe Consequently you must obtain i q y We buy power from a rural electric ermission or approval to sell power Regulations vary by region so P PP P 5 D epus cooperative give the utility a call and ask for information As mentioned on http www myrec coop residential age 10 in some areas if you want to sell power your system must be PADS d P p y index cfm designed from the start to oz y sell power so you can t use any solar Th imple Fi power yourself Check with your utility MIL QE mailed a notice of intent to sell h issi ll it is likely that the utili Once you have permission to sell power it is likely that the utility power and listed the required will insist on verifying that your inverter meets certain electrical and oo A technical information from the safety standards such as the voltage and frequency being within a inverter s owner manual certain limits This information is readily available from the inverter After the system was installed an manufacturer often is listed in the owner manual Most importantly y i n electrician from the utility came b the utility will want to verify that the inverter instantly stops selling y y d d pulled th power removes voltage from the input cable when grid power is Du Ng E f f l electric meter while the system was interrupted This latter is to protect linemen from elec
60. ank connects to a tie plate below two 175A The Radian inverter in this system circuit breakers The tops of these breakers connect directly to Contains two 4 KW power modules so each power module has its own breaker A the inverter s positive DC input terminal If an overload occurs the breakers will trip system with a single module inverter would need only one AC input protection muc The inverter is fed through a branch circuit circuit breaker in a household breaker box or breaker panel This branch breaker trips and protects the household wiring if an overload occurs In addition the AC input to the inverter must be protected If you are not using a load center with a built in circuit breaker you must provide one of your own Check with your vendor or the inverter Figure 40 AC input circuit breakers Planning A Solar Power System The Complete System Page 94 manufacturer to learn where this breaker should be installed Figure 40 shows the AC input circuit breakers in the Outback Power load center Our choice clarity Notice the Gen In breaker In this system if a generator is We painted the ends of the circuit present it is treated as an AC input just like the grid and requires its breaker levers orange to make own breaker them more visible AC output protection Miro I S The inverter protects itself usually shutting down if the AC load to clearly identify each breaker
61. anning A Solar Power System Why Do You Want a Solar Power System Page 8 There s more When the DC power from the solar panel goes through cables and a charge controller and into an inverter to be converted to AC house current it loses about 10 more So the overall efficiency is around 13 90 of 15 By the time those 1 860 watts make it to a household receptacle only about 240 watts are available to use That s barely enough to power one big screen TV And that s at high noon PV panels produce less power when the sun is off axis only a tiny amount on cloudy days and absolutely none at night Okay you say can t I add more PV panels to get more power Sure you can if you have the space for them and can you afford them Is doing so a good value In 2013 solar panels cost approximately 1 25 per watt of power generating capacity That 279 watt panel above would cost about 350 That s 3 500 for 10 panels to capture 18 6 KW of solar energy at noon on a sunny day and produce 2 5 KW of electrical power for you to use For 3 500 you can buy a really nice propane powered generator that will supply electricity to your entire house day and night Notice that the 3 500 buys on y the PV panels It doesn t include batteries a charge controller an inverter and other components needed to make the whole system operate A complete system might run three times that amount We will discuss costs in detail later Are you begi
62. ating current is the reason Nikola Tesla http en wikipedia org wiki Nikola_Tesla is the unsung hero of the electrical revolution Thomas Edison promoted direct current as the best way to distribute electricity but low DC voltages safe for household use could not be transported over long distances and there was no good way to transform the high voltage needed for long distances into safe household voltage Tesla patented the AC transformer and licensed it to George Westinghouse who along with Tesla as an employee developed the AC power distribution system we use today The 240V coming into your house s circuit breaker box is split in that box into two 120V legs or branches which are wired to wall outlets receptacles and lighting fixtures Some appliances such as an electric range or electric water heater use the full 240V Appliance power consumption All electric appliances from light bulbs to ovens consume power which is measured in watts W or kilowatts KW It is vital to know how much each appliance draws consumes because you can then estimate the total load and thus choose a system that will supply sufficient power We discuss how to determine each appliance s power consumption starting on page 16 and later we learn how to use this information to plan your system Planning A Solar Power System How a Solar Power System Works Page 12 Solar panels Let s start at the beginning Photovoltaic panels
63. ay s capacity instead of two days 3 Shift activities to daytime If your solar array can supply enough energy to charge the batteries while running your appliances maybe you could shift some power usage to daytime hours For example instead of settling down to watch three or four hours of TV in the evening record the programs and watch them on the next sunny day Perhaps you could use your computer more during the day and less at night These aren t easy choices Buying more batteries is costly as is switching from flooded cell to AGM batteries Gel cell batteries are even more expensive Stacking inverters also increases cost but allows you to increase your energy storage capacity Likewise buying a generator or adding a wind or hydro system adds to the cost Lifestyle adjustments are the least costly but they might be annoying and frustrating to deal with during a grid outage Planning A Solar Power System Choosing Batteries Page 41 Site Survey Part 1 The first step in choosing solar PV panels is to figure out where you can mount them PV panels should be in a clear area that faces south Many people mount PV panels on the roof of their house but ground mounts also work well The goal now is only to identify a location with good sun that is large enough for the estimated number of panels needed A complete site survey requires a full year and is described in Site Survey Part 2 Feel free to do that in
64. ber 21 It is at its highest noon elevation at noon on the summer solstice near June 21 The highest and lowest elevations depend on your latitude Insolation The amount of solar radiation received by an object such as a PV panel Daylight Saving Time DST is the regional practice of advancing clocks one hour in summer to provide more hours of daylight in the evening This also is known as Summer Time in some areas of the world Solar noon is the moment the sun is at an azimuth of 180 due south and is at its highest elevation of that day This is approximately 12 00 noon on the clock when DST is not in effect or approximately 1 00 PM on the clock when DST is in effect The closer you are to the eastern boundary of your time zone the earlier your solar noon occurs on the clock It occurs at 12 00 standard time at the approximate east west center of the time zone and later than 12 00 toward the western boundary This NOAA sunrise sunset calculator http www esrl noaa gov gmd grad solcalc sunrise html includes a field for solar noon Select a nearby city and click the Calculate Sunrise Sunset button then see the results below it Be sure to use the values in the Local row Harvest refers to the amount of power collected by a PV array during a particular time period such as a day Example Today we harvested 18 KWH of solar power Battery is is a device consisting of cells that produce electricity from a chemical
65. better face mount from pressure treated 4x4 and 2x4 the lower sun and in summer you d aim the panels higher in lumber Given the weight of this lumber the sky If you build a wooden support system you could build we elected to make it non adjustable a tilt adjustment into it concluding that adjusting such a large Adjusting tilt is more attractive with a ground level PV structure would be difficult and flexing array than with one on the roof Who wants to climb up on might damage the panels the roof twice a year Recall from Which season gives the most solar energy Important that for a typical array not adjustable solar energy production is lowest in summer but highest in December and only slightly lower Planning A Solar Power System Site Survey Part 2 Page 58 than December for much of the year It s your choice Do you want the added complexity of an adjustable mount and the chore of adjusting it twice a year or will you accept a slightly lower annual PV harvest Comparing tilt angles The websites mentioned above will tell you good winter and summer tilts if you plan to use an adjustable mount But if you want a non adjustable mount what is the best angle Let s revisit the hypothetical 4 KW PV array in Columbus introduced in Table 9 but compare various tilt angles in 5 increments Remember the tables show the total power produced on the four specific dates shown and the 4 day total is the tota
66. ble into it and into the system controller to add your system to the network after configuring the system controller Stringing an Ethernet cable might not appeal to you so consider a Wi Fi to Ethernet Adapter such as this one http www amazon com NETGEAR Universal Ethernet Adapter WNCE2001 dp B003KPBRRW z m Qa m gt m This device plugs into the system controller s Ethernet jack and connects to the Wi Fi router just like any other wireless device Range is limited so locate your router as close as possible to the solar power system Figure 51 shows a Wi Fi adapter glued to the top of a system controller The black cable is from the AC DC power adapter plugged into a nearby solar outlet and the blue Ethernet cable plugs into a jack on the rear of the system controller The red light on the adapter indicates that the Wi Fi connection is weak if possible the adapter should be moved closer to the router Get started Congratulations Your plans are complete so now you can move ahead with the actual project I hope this document helped in some small way Good luck to you The next chapter is an overview and photo gallery of our system should you care to have a look Planning A Solar Power System Finishing Touches Page 113 THE Dopp Kuryto Solar Power System This chapter describes our system many of the design decisions we made during the planning phase the compromises we made and
67. bles in place TA Figure 31 Terminal bus bar TBB Planning A Solar Power System The Complete System Page 87 These latter are known as terminal bus bars or TBB In Figure 31 the silver color TBB is held in place by two insulated black brackets The battery rack from Outback Power http www altestore com store Deep Cycle Batteries Enclosures for Deep Cycle Batteries Rack Type Battery Enclosures Outback Power 3 Shelf Integrated Battery Rack for 48V Systems p9859 has tie points built in and other brands likely do as well Check your manufacturer s data sheet for details If you don t buy a commercial battery rack with built in tie points you can build your own The enclosure in Figure 32 is made from 34 plywood and contains the positive and negative tie points between the battery bank and the inverter Each terminal is made from a heavy right angle steel bracket with a 1 14 20 bolt attached to it Four cable lugs are secured to each bolt with a nut and washer Two 2 gauge black cables from the battery strings negative terminals enter on the left and one enters on the right All are the same length Similarly two 2 red positive cables from the 175A circuit breakers enter on the left and one enters on the right All of these cables are the same length Heavier 00 two aught cables leave the tie points on the left and go through conduit into the load center beneath the inverter Why are these
68. building inspector Also ask your vendor what products are available for lightning protection and if they meet code Often a lightning arrestor is mounted in a hole in one side of the combiner box and a heavy wire runs from the combiner box cabinet to a ground rod driven into the earth Ground rods are commonly 8 copper clad steel rods with a bracket on the top end to attach the wire and are sold at hardware stores PV panel frames must be bonded together with a wire that also connects to the ground rod The panel manufacturer provides holes in the frame marked with a symbol consisting of a vertical line above three horizontal lines in the shape of a triangle For an example see http www incompliancemag com index php option com_content amp view article amp id 920 the grounding symbols amp catid 66 on your mark amp ltemid 204 Planning A Solar Power System Choosing Solar Panels Part 2 Page 71 Clamps or clips to attach the ground wire to solar panels are sold by vendors Here is one type of lug http www akarienergy biz Wiley Electronics W EEB Grounding Lug 67 WEEBL 67 WEEBL 67 htm Check your local electrical code for the size wire required for grounding solar panels 8 gauge is common and your code might also require bare uninsulated wire Ground faults and the GFDI A ground fault is a condition that allows current to flow to the system ground typically the earth instead of normally through the circuit wire
69. cable on the left These are discussed in the next section Cables and connections No matter how you interconnect your batteries you will need heavy duty cables with heavy duty terminals to connect them to other components such as tie points circuit breakers the inverter and the charge Figure 29 48V AGM battery string controller Wire size Wire size is measured in gauge in the American wire gauge AWG system A smaller number indicates a larger wire so 10 wire is larger than 12 0 wire is larger than 12 10 and even 1 Planning A Solar Power System The Complete System Page 86 Wire sizes can be larger than 0 and their gauge is represented with multiple zeros such as 00 abbreviated 2 0 000 3 0 and 0000 4 0 The 0 in these large gauges is pronounced aught so 000 or 3 0 is pronounced three aught Smaller sizes are commonly referred to as number 10 10 or 10 gauge Now you can ask for wire like a pro Making connections A typical battery string cable is 2 AWG 2 be 2 Our choice make a crimping tool auge and measures a little over 14 in diameter Cables pears Ne gauge Some crimping tools look similar to bolt feeding the inverter might be 2 0 two aught gauge You 5 5 ght gaug cutters so we converted a bolt cutter into a can t wrap cables this large around a screw you need a er crimping tool Y terminal sometimes called a lug on the end of t
70. ce you d enter 5 not 12 in the No column to get an accurate estimate of the typical load The Total KW column is simply the KW load multiplied by the quantity in the No column Notice the Hours on per day and KWH per day columns Estimate how many hours per day each appliance is used Multiply the total load KW by these hours to get the total power KWH used by that appliance in a typical day Example In Table 1 the five 26W ceiling fixtures together draw 130W 0 13 KW and all five are estimated to be turned on for 8 hours each day Multiplying 0 13 KW by 8 hours yields a daily power consumption of 1 04 KWH In this example the total solar load is 4 2 KW if all the listed appliances are operating at the same time This is a worst case condition but one for which the inverter should be sized and is a factor in determining the number of solar panels This example shows that 3 31 KWH are consumed per day The KWH per day value affects how many batteries you will need and is another factor in determining the number of solar panels Planning A Solar Power System Getting Started Estimating Electrical Loads Page 17 Enter your appliances and their power consumption in Table 2 or create a simple computer spreadsheet to hold the same information Solar power audit table If you prefer a paper table instead of a computer spreadsheet for your solar power audit print as many copies of Table 2 as you need to list all a
71. ce from the start Method A does that With Method A you can think The sun is at 68 elevation and my solar panels are tilted 68 so they are directly facing the sun You can t do this with Method B Be alert to this difference if you visit websites that discuss solar panel tilt This document uses Method A You may use Method B if you wish but remember to subtract one angle from 90 Websites abound that offer advice formulas and graphs on how to choose the optimal panel tilt Here is one http www macslab com optsolar html Planning A Solar Power System Site Survey Part 2 Page 53 But these websites don t always agree with each other And sometimes they present highly technical academic papers instead of simple formulas Worse some websites define tilt angle differently than others How latitude affects sun elevation The earth s axis tilts 23 4 The earth takes one year to orbit around the sun Twice during the year at the equinoxes approximately March 21 and September 21 the sun is directly over the equator and the axis is not tilted toward or away from the sun Once during the year at the summer solstice approximately June 21 the northern hemisphere is tilted 23 4 toward the sun and once at the winter solstice approximately December 21 it is tilted 23 4 away Because of the axis tilt the sun is at its highest solar noon elevation on the summer solstice and at its lowest solar noon elevation
72. cember 21 in Columbus the sun rises to 50 equinox elevation 23 4 tilt 26 6 You can check these two elevations on the sun chart in Figure 14 which is plotted for Columbus Sun charts are discussed below Calculate the sun s noon elevation at your location on the summer and winter solstices using the consolidated formulas below Write these elevations here or in your solar planning notebook Sun s summer solstice noon elevation 90 your latitude 23 4 tilt Planning A Solar Power System Site Survey Part 2 Page 54 Sun s winter solstice noon elevation 90 your latitude 23 4 tilt Which season gives the most solar energy Important With its longer days and higher sun you might think that summer is best for harvesting solar energy Not so Even though the sun is higher it moves across the sky faster giving fewer hours of useful sunlight Look ahead to the sun chart in Figure 14 on page 57 Notice how widely spaced the red hour lines are where they cross the June curve compared to where they cross the December curve In June the sun moves 42 in the hour before noon and another 42 in the hour following noon That s 84 in just two hours But in December the sun moves only 30 during those same two hours one third as much Still not convinced Look at this table showing solar harvest from a hypothetical fixed 4KW solar array pointed due south and tilted 38 in Columbus Ohio at 40 nort
73. clouds Surprising as it might seem PV panels will produce power under clouds or even when greatly shaded Moderate clouds can transmit considerable light and a clear sky is bright enough for shaded panels to add some power to the array These photos were taken in August so the sun travels lower in the sky than it was in June The captions give details Overcast day at 10 30 7OOW This doesn t look much different the photo at left but it s the same time and the sky is completely overcast notice the diffuse shadows Yet the array is making 700 watts just from light coming through the clouds That s 20 of what it was making in full sun In full sun 1 hours before solar noon and the sun is 43 off azimuth and 8 off tilt The array is making 3 5 KW 86 of its potential when directly facing the sun Partially shaded at 2 00 1 8 KW It s two hours after noon The sun is 51 off azimuth This is interesting A panels are mostly shaded and 9 off tilt Eight panels are unshaded three in enough so all the columns of series wired cells the front row and five in the rear The cosine math should be interrupted Yet the array is making 300 says that these seven panels should be producing watts despite the shadows 1 4 KW but the entire array is making 1 8 KW The extra 400W must be coming from the blue sky light striking the shaded panels PV cabling to the house With a ground mounted s
74. ction Here we cover only fixed mounts As you might expect the Internet abounds with websites telling you how to determine the best tilt angle for your solar panels For the most part they are confusing difficult to understand and frequently at odds with other sites Worse many of them tell you the best angle in winter and in summer but not the one that is the best compromise for the entire year Here are two if you wish to dive into the fray http www macslab com optsolar html and http www solarpoweristhefuture com how to figure correct angle for solar panels shtml This one offers a calculator http solarelectricityhandbook com solar angle calculator html The calculator is at the bottom of the page not the angle calculator advertisement midway down First review the sidebar clarifying tilt angle on page 53 so you know what the websites are talking about and what we are discussing here Adjustable mounts Solar panels attach to fixed frame usually made of aluminum that may be installed on a roof or at ground level Some frames are intended to attach flat to the roof but others have tilt adjustments Ground mounted frames might also come with adjusters Ask vendors for details If a frame is adjustable you have the option of adjusting Our choice non adjustable the tilt of the panels a couple of times during the year In We fabricated our own ground level winter you d decrease the tilt angle so the panels
75. d branch circuits in your house So if you discover that your solar appliances are dead but the solar power system appears to have no problems and no breakers are tripped check the safety disconnect outside Did someone flip the switch If so why Check with your utility about locking the box if you suspect vandals The lock could be a real padlock or a plastic cable tie anything to deter mischief System configuration for selling power Once the utility approves your system to sell power you must configure it to do so This is done using the system controller and instructions should be found in the system controller or inverter owner manual You probably can turn selling on and off at will should the need arise Planning A Solar Power System The Complete System Page 103 That s it we re almost done You have successfully Identified your reasons for wanting solar power Conducted a power audit to determine how large a system you will need Figured the size of the battery bank Chosen candidate PV panels and system equipment and refined your choices Conducted a site survey to find the best location for the solar array and determined the best tilt angle for the panels Learned how to build a battery bank Learned how to mount and wire solar panels Learned about the system components inside the house and how they are interconnected Using the knowledge you have gained call your favorite vendor once
76. d com batteries batteryblunders htm writes i Figure 34 Negative bus bar avoid stacking cable lugs at the battery terminals to make parallel connections Instead bring wires separately from each string to 2 bus bars outside the battery box Another website http solarprofessional com articles products Our choice single tie points quipment batteries high capacity battery banks page 0 5 says If using a bus bar is common Using battery terminals to interconnect series strings in parallel is a practice is it a good practice common practice in the field but is less than optimal A better approach We chose not to take a chance and is Zo run the positive and negative leads from each string to common used equal length cables to single busbars that combine the multiple battery strings at a central location tie points Circuit breakers As explained on page 86 175 amp circuit breakers are needed to protect battery strings and also as a convenient way to switch out individual strings for maintenance Expect a commercial battery rack to contain circuit breakers but if you don t use a commercial rack you can build circuit breaker bracket similar to the one shown here The circuit breakers are attached to the 4 plywood bracket with metal angles and screws The breakers are separated with barriers just in case because adjacent breaker terminal bolts are close together The three cables from the bat
77. d computer Microwave oven 1 8 KW Toaster 1 KW hair dryer 2 KW Water well pump 1 3 KW These four appliances alone total 6 1 KW and they alone would call for an inverter rated for at least 7KW This seems high what can we do Planning A Solar Power System Choosing an Inverter Page 24 Start by taking a close look at your solar power audit Will all of the high power appliances really be running at once At this point you can make several choices that affect inverter capacity Choose wisely and you might discover a smaller inverter lurking behind the numbers Here are several things you can do to reduce the size of your solar power load or at least be satisfied that your inverter will be correctly sized for your loads 1 Reduce the inverter s extra capacity Maybe the 20 to 40 extra capacity you added above is too high It s easy to get carried away with a feeling of power and end up with too much capacity Re evaluate your thinking maybe you can reduce the extra capacity without cutting things too close 2 Don t power an appliance from solar Some things don t need to be solar powered they can remain connected to the grid only For example do family members really need to dry their hair with solar electricity If the answer is no choose to leave bathroom outlets wired to the grid breaker box Delete the hair dryer from the solar power audit and enter it on the grid power audit as described on page 19
78. d in 13 Write this in 14 15 Now for the moment of truth now many KWH can your candidate battery bank store Multiply each string s KWH capacity in 12 by the number of strings in 13 and write this in 15 Remember that 12 is smaller than you might expect because of the 50 DoD reduction Line 15 accurately portrays the number of KWH you can expect from your battery bank while discharging it no more than 5096 Planning A Solar Power System Choosing Batteries Page 38 Compare the battery bank s KWH in 15 with the zarget capacity KWH in 3 If 15 is the same as or larger then 3 you re in good shape the candidate battery bank can store the needed energy If 15 is smaller you have some choices to make Read the yellow sidebar Hitting the target storage capacity on page 40 for things you can try to achieve your goal The sidebar is long After reading it come back here and complete lines 16 17 and 18 in Table 6 As you read the sidebar remember your fundamental reason for wanting a solar power system in the first place Re read Why Do You Want a Solar Power System and try to put a value on the decisions you have to make not only the monetary factors but lifestyle factors as well This is the first point where value is a key factor If you are concerned about anything now is a good time to evaluate the value you will receive relative to the cost effort and grid down lifestyle This is not meant to be discouraging Thin
79. ds Page 22 At the end of the day press the red KWH button to see how many KWH were consumed by the TV that day Press it again to see how many hours and minutes the TV was on Hold the red KWH button to reset the timer to 00 00 and clear the KWH value You can leave the TV plugged in for as many days as you want and check reset it every night If you average the power used by an appliance over several typical days you can enter that daily KWH directly into the solar power audit Table 2 without bothering with the number of hours the appliance is turned on each day Total solar power load Once you have collected the power consumption for all appliances you want to power from solar and that are expected to be turned on at the same time sum those figures to arrive at your total solar power load consumption Enter this number in the solar power audit Table 2 We will use it right away in the next section and again later Planning A Solar Power System Getting Started Estimating Electrical Loads Page 23 CHOOSING AN INVERTER The total solar power load in the solar power audit Table 2 is the basis for choosing an inverter Recall that the inverter page 6 converts DC power supplied by the batteries into 120 or 240 VAC to operate appliances The inverter must have the capacity to power at the same time all of the appliances listed in your solar power audit In other words it must be rated for at least your total solar power
80. e The site hasn t yet been marked with stakes and orange tape so the proposed site outline was added during photo editing Notice also the sun s azimuth and elevation that were added during editing These can be obtained for the date and time of a photo from an online calculator such as this one from NOAA http www esrl noaa gov gmd grad solcalc azel html Figure 15 Example site survey photo The azimuth and elevation are interesting notes only the photo shows there shadows fall It is important to know the date and time include it in your computer file name if you don t add it to the photo during editing 3 Choose a consistent day of the month and a consistent time It helps but isn t absolutely necessary to check your PV site on the same day and time each month Planning A Solar Power System Site Survey Part 2 Page 64 Date The equinoxes and solstices occur around the 21st of their months so this day is a good choice Then four times per year you can easily calculate the sun s noon elevation see page 54 which gives you four reference points Time Plan to survey your site three times on the designated day of each month two hours before solar noon at noon and two hours after This gives you a four hour optimum solar window Remember to adjust for Daylight Saving Time Explanation The four hours between 10 00 AM and 2 00 PM solar time are when the sun becomes reasonably high in the sky and your PV ar
81. e 81 Cables from the array to the system Follow the electrical code when running PV cables into your house You might need an electrical permit and inspections depending on where you live With a roof mounted array the cables must come down from the roof and run down a wall to some type of entrance inside the house Your building inspector or solar professional will tell you what is needed With a ground mounted array it is likely that the cables must be buried in a trench Again the building inspector is the person to ask about trench depth and how to get inside the house If the cables are buried in a trench you must provide a way for them to exit the trench and reach the combiner box They can t just come out of a hole and run along the ground or hang in the air A short length of PVC conduit with a service head on top is what you need with the cables firmly supported and entering the combiner box through appropriate bushings Or else attach the conduit directly to the combiner box using a conduit adapter fitting in one of the knockouts Figure 25 shows a service head atop conduit running from the second row of PV panels The heavy black cables in the other conduit are the array feed cables to he house Additional conduit will be attached to the elbow and attach directly to Figure 25 Service head the combiner box Planning A Solar Power System Choosing Solar Panels Part 2 Page 82 THe Compete SYSTEM Here it i
82. e ampere of current to flow for one hour It is abbreviated AH Watt hour WH is the measure of electrical energy equivalent to a power consumption of one watt for one hour A kilowatt hour KWH is 1 000 watt hours Examples The electricity you buy from the utility is measured in KWH by the meter on your house If you operate a 100 watt light bulb for 24 hours it consumes 2 400 WH or 2 4 KWH If your electricity costs 12 per KWH you ll pay about 29 for those 24 hours of light Circuit is the term used to describe a path over which current flows when a voltage is applied Example An appliance power cord plug has two terminals When the cord is plugged into a receptacle outlet current flows through one wire in the power cord into the appliance then out of the appliance through the other wire The power cord wires and the appliance make up a circuit Direct current abbreviated DC is current that flows in only one direction through a circuit PV panels and batteries produce direct current We omit the space before DC when it is preceded by V for volts Examples 72 VDC or 12 volts DC with space preceding DC Planning A Solar Power System Definitions and Formulas Page 3 Alternating current abbreviated AC is current that periodically reverses direction as it flows through a circuit The electrical power grid and your household wiring carry alternating current We omit the space before AC when it is preceded by
83. e will yield good solar energy production Planning A Solar Power System Site Survey Part 2 Page 68 CnoosiNc Sorar Panets Part 2 It s time to finalize most aspects of the PV panels so you ll be ready to order them and everything associated with them when it s time This is a bit more involved than calling your favorite vendor with a part number How will you mount the panels Solar panels must be securely fastened in place to prevent flexing and resist high wind Furthermore the panel frames must be connected together and to a ground rod driven into the earth see Lightning below Frames racks are available for roof mounting and for ground mounting or you can build your own with moderate carpentry skills On the roof Probably the easiest way to install PV panels on a roof is to buy commercial metal mounting system Flush mounts hold the panels close to the roof and at the same pitch Adjustable mounts let you adjust panel tilt independent of the roof pitch This vendor http www ecodirect com Solar Panels for Roofs s 587 htm sells several brands click on a manufacturer link if little information comes up on the mount First determine the pitch of your roof An electronic digital level such as this one http www homedepot com p Husky 9 in Digital Level THD9403 100653598 keyword THD9403 Uhd9in wVuA is a handy tool for this task You can climb up and set the level on the roof to measure the angle or
84. er Call vendors for information Okay you have determined you need a 5 3 KW inverter What now What 5 3 KW inverters are available It s time to call solar equipment vendors explain what you re trying to accomplish and ask for information The Internet is an excellent place to find vendors Here are four Google likely will turn up more The altE Store http www altestore com store This is where we bought our system Affordable Solar http www affordable solar com We talked with them first and the people seemed knowledgeable Civic Solar http www civicsolar com Wholesale Solar http www wholesalesolar com Take copious notes as you talk with vendors Here is how the conversation might go your side is in blue the vendor s side is in red I m planning a solar power system for my home and I ve determined I ll need a 5 kilowatt inverter What do you have in this capacity and how much do they cost know I ll need PV panels and batteries later but right now I m focusing just on the inverter You could use the 8 KW EZ PZ or you could stack two of the 3 KW SolMeister inverters to get 6 KW Often two or more inverters may be wired together stacked for increased capacity Naturally your total inverter cost is the total of all inverters plus any interconnection components If the vendor recommends stacking inverters ask for the price of each inverter plus the cost of interconnection components If 1 go
85. er By doubling the PV voltage we ve cut cable heat loss by a factor of 4 Solar panel open circuit voltage Voc When sunlight falls on a solar panel that is not connected to a load the voltage it creates is abbreviated Voc for open circuit voltage Voc is important because the charge controller to which the panel is connect has a maximum voltage rating that it can accept without damage The solar array s Voc cannot exceed the charge controller s open circuit input voltage specification But watch out A PV panel s Voc varies with ambient temperature higher when cold and lower when hot The charge controller owner manual probably says to multiply the panel s Voc by a temperature factor To be safe you should use the largest factor stated regardless of what you might hink is the lowest your temperature will ever drop Assume a charge controller can accept voltages up to 60V and a PV panel s Voc is 52V Sounds good initially but suppose the controller owner manual s largest factor is 1 25 for ambient temperatures of 5 to 40 Use the 1 25 factor Multiplying 52Voc by 1 25 gives a temperature adjusted Voc of 65V too high for the charge controller s 60V What does all this mean It means you should plan on wiring as many PV panels in series as you can without their temperature adjusted Voc exceeding the charge controller s maximum input voltage This will reduce current in the PV array feed cables and reduce power loss
86. er Two cables were used in this installation to reduce power loss as described in Reducing the cable resistance You might need only one of each cable depending on your situation Once the internal components are wired a panel snaps into place to conceal and protect the wiring All cables enter the combiner box through waterproof bushings or through conduit fastened in knockout holes on the box s sides and bottom The black objects at the bottom of Figure 22 are bushings for the PV cables and the large gray fitting surrounding the four heavy cables secures 114 PVC conduit from a nearby trench The red and green wires at the bottom are from a lightning arrestor mounted in a knockout hole in the box side just out of view Planning A Solar Power System Choosing Solar Panels Part 2 Page 78 PV extension cables Extension cables extend the PV panels short factory cables to the combiner box One end of each cable must have an MC4 connector to mate with the panel s MC4 connector and the other end must be cut and the insulation stripped about 1 2 to connect to a circuit breaker or negative TBB Common practice is to buy a stock 10 gauge extension cable with a male MC4 connector on one end and female MC4 on the other end such as this one http www altestore com store Cables Wiring Wiring For Solar Panels 50 H4 Connector Cable 10 AWG p10469 The cable is cut into two lengths each with an MC4 connector on one end and not
87. er and email address Thank you very much You ve been quite helpful Do you have a direct phone number or extension so I can call you again What is your email address Call several vendors as they often carry different brands It might turn out that Brand X makes exactly the inverter you need while Brand Y is too large and Brand Z requires stacking Once you have identified several candidate inverters visit each manufacturer s website and read as much as you can about each model Download the brochure installation manual and owner manual These usually are available as PDF files If you can t locate what you need call the manufacturer s sales or customer support line and ask where information can be found Enter information about your candidate inverter into Table 4 below The DC input voltage will be needed when you fill in Table 6 in the Candidate battery calculations section If you plan to stack two or more inverters enter that number in the Stack column Multiply each inverter s AC KW output by the number of inverters and enter the result in the Total KW output column Do not multiply the DC input voltage this is the same for all inverters in a stack Enter the total price for the inverters and stacking equipment so this isn t lost later Brand and model Total DC input Total KW number Vendor Price KW out Stack voltage output Table 4 Candidate inverter information W
88. er the electricity to the rest of the system inside the house Heavy cables are required for this their gauge determined both by your calculations related to cable size and power loss in Reducing the cable resistance and also possibly by the electrical code Wire size Look again at your PV array s maximum current on page 73 Then refer to a wire table copper http en wikipedia org wiki American wire gaugefTables of AWG wire sizes and look at the lowest current value in the ampacity amp capacity column equal to or higher than your current This is the smallest wire you can use to carry that current For example if your PV array can produce 100A of current the table shows that 1 cable is the smallest allowed Note the insulation temperature ranges in the ampacity column The lowest currents are for an insulation rated for 60 C If your wire supplier has wire rated for 75 C or 90 C you can use 3 instead of 1 possibly saving money with the smaller size If a particular gauge is not available buy the next larger gauge smaller number wire that is available If the wire from the table is the same gauge or larger smaller number than the wire you calculated in Reducing the cable resistance you re good to go If it is smaller buy the size you calculated It will exceed the ampacity of the gauge shown in the table thus exceeding code requirements Planning A Solar Power System Choosing Solar Panels Part 2 Pag
89. erator What A generator This definitely is optional no solar power system requires one But having one allows you to supply household power and charge the batteries during long grid outages combined with cloudy days Planning A Solar Power System How a Solar Power System Works Page 14 Some systems allow the generator to be connected directly to the inverter which can start it automatically and use its power when needed In grid tied systems approved to sell power to the utility the inverter will or sell power from the generator because it is not a green energy source To be sold power must flow through the charge controller e g from solar panels Generator power doesn t flow through the charge controller House circuit breaker box The inverter output feeds its output to a breaker box that is designated for solar power and wired to circuits you have determined are within the inverter s capacity We ll learn how to figure these loads later If your house presently has all of its circuits wired to breaker boxes that are connected to the grid an electrician can install a new solar box and rewire your designated circuits to it If you are planning a new house have the electrician install this solar box from the start It can be wired to a breaker in a grid box until you install your solar power system at which time the electrician can remove that cable and wire the inverter s input to the grid box and t
90. es The best angle might lie between 35 and 40 because their values are so close but we ll ignore that The 35 panel tilt also yields the best 12 day total as well Since this is the total power produced on the 21 of each month we can extrapolate to conclude that all of the days in each month will produce similar results so 35 is the best tilt angle for 40 north latitude Regardless of tilt summer production is always lower than winter production due to the sun s rapid movement across the sky Refer back to Which season gives the most solar energy Important A 70 panel tilt produces 16 more power on June 21 than 35 so if you need more solar power in summer 70 would give it to you but you d get 16 less power over the entire year Similarly if you need more solar power in winter tilting the panels to 20 produces 8 5 more power on December 21 than than 35 but with 4 3 less power over the year Points 4 and 5 might argue for installing an adjustable mount You could set it to 20 in winter for maximum power then set it to 70 in summer for June s 16 gain In reality you probably would want to change it on the equinoxes March 21 and September 21 Planning A Solar Power System Site Survey Part 2 Page 62 Optimal tilt angles for various latitudes Calculating total PV power production over a series of full Our choice not quite optimal days is complicated because it requires ca
91. es and charge your batteries at the same time allowing you to shut it down periodically and run from batteries for a few or many hours Three questions must be answered when considering a generator the type of generator how to connect it and how to start it Planning A Solar Power System The Complete System Page 95 Generator type Generators come in many forms from small 2 KW portable gasoline units to permanent 20 KW models burning propane or natural gas and capable of powering an entire house Gasoline goes bad forms gum after a year so a gasoline powered generator is not a good choice unless you drain the fuel and replace it periodically Some farm supply companies will deliver gasoline to a home tank A natural gas generator burns cleanly and is great if you have Our choice diesel generator We bought a 6 5 KW diesel generator from Central Maine Diesel http www generatorsales com ord er Yanmar 6875 Watt Diesel natural gas piped to your home If not propane in a tank will provide the same clean burning performance albeit at higher cost Propane companies will install a storage tank and deliver propane to it by truck on a regular basis Diesel fuel stores well especially if treated with additives and diesel engines are reliable However many diesel powered generators Generator asp page Y6875 Oi i ly will deli iesel fuel k are very loud Oil companies usually will deliver diese
92. es you choose to restrict subtract the smaller of the two loads from the total then use the lower total to size your inverter Subtract only one Planning A Solar Power System Choosing an Inverter Page 25 load because one appliance is assumed to be running while the other is not Subtract the smaller load to be on the safe side 4 Assume it won t happen often This isn t as risky as it sounds It might be extremely unlikely that two high power appliances on your solar power audit will ever run at the same time possible but probably not Consider the toaster and microwave probably not If you are willing to deal with a complete solar power outage in the event an overloaded inverter shuts down leave both unlikely appliances on your list but include the highest power in the load and KWH columns Highlight both appliances so you remember they pose a potentially unpleasant situation and size your inverter using the new solar power audit total 5 Believe your numbers If you ve made an accurate list of solar powered appliances that will be operating simultaneously trust your work As some folks say i is what it is If your solar power audit calls for an 8 KW inverter and you see no good way or aren t willing to reduce the solar load then plan on buying an 8 KW inverter Select a DC input voltage An inverter is designed to operate from a specific DC input voltage usually stated in the data sheet as nominal DC inp
93. ge 36 The nominal voltage might require you to string batteries together For example if an inverter is specified to run on 48 VDC and you plan on using 12V batteries a common choice you ll need four of them in series In this case the inverter gives you no choice if you don t want to string batteries search for a different inverter with a lower nominal operating voltage Choose a candidate battery from Table 5 on page 35 The examples shown here might be helpful in understanding calculations or decisions made in steps 5 16 The KWH value is obtained by dividing the price by the KWH The blank lines at the bottom is for you to enter your candidate battery s information from Table 5 for quick reference Brand amp No Vendor Type Volts AH KWH Price KWH Trojan L 16 RE 2V altE Store Flooded 2 1110 2 22 361 163 GC15DT altE Store Flooded 6 230 1 38 194 141 Trojan TE35 GEL altE Store Gel 6 210 1 26 335 266 Concorde PVX 3050T altE Store AGM 6 305 1 83 410 224 Concorde PVX 2580L altE Store AGM 12 258 3 1 699 225 Table 7 Example candidate batteries for Table 6 5 Enter the part number of battery you ve chosen as your candidate 6 Enter the battery type Almost certainly this will be flooded cell gel cell or AGM 7 Enter the battery s voltage In the Table 7 examples notice that voltages are multiples of 2V which is the cell voltage for lead acid batte
94. gth The positive and negative feed cables black in the drawing from the tie points to the charge controller may be of unequal lengths Why equal cable lengths The reason for this is to equalize wire resistance so all batteries are charged and discharged equally This is another example of how Ohm s Law affects system design E I x R and even though cable resistance is small the high current through the cables reduces voltage by a small amount This drop must be equal for all battery strings so all cables in the same string position must be equal length and of the same wire gauge or course If a cable to one battery string has a resistance only 0 0050 higher than a cable connected to a second string and a 50A charging current flows through each cable the string connected to the first cable receives a charging voltage 0 25V lower and the batteries in the first string will not recharge fully The same principle applies to discharging The rule is Every battery in a bank should charge and discharge equally and equal length cables help make this happen Planning A Solar Power System The Complete System Page 89 Here is a close up of the copper bus bar connecting the negative terminals on the battery bank inFigure 7 According to some experts this is not ideal because the distance from the cable on one end and the other two battery terminals is unequal For example this 27 year supplier http www survivalunlimite
95. gure 10 for a total of 2 9KW 15 of the 200W panels in Figure 11 would give you the same power but are 2396 shorter Could you fit 15 of the shorter panels in your space How about if you rearrange them as suggested in 3 below 3 Rearrange the panels If you are planning to install a row of portrait panels would two or three rows of landscape panels work better On a roof you can t go any higher than the ridge but on the ground you can can build one row in front of another until you have enough rows to hold all the panels 4 Ona roof it might be possible to allow a portion of the top row of panels to project above the ridge Panel mounting holes are 5 6 from each end and panels bolt to metal roof brackets Ask your vendor for options to allow one row of panels to project above the ridge Maybe a particular mounting framework can extend above the ridge Planning A Solar Power System Site Survey Part 1 Page 46 5 Choose a different site for the solar array Maybe that spot on the roof between two dormers isn t so good after all Or maybe the unsightly location out by the driveway is now preferred over the smaller site in the backyard 6 Reduce the target PV array power left column in Table 8 Lower array power means fewer panels This may or may not have profound implications depending on how the array was sized in the first place as well as your reasons for installing solar power If you hope to go off grid less p
96. gy systems placed in service after 2008 The expiration date is December 31 2016 but keep an eye on this if the political climate in Washington DC changes will the program be ended early As you tally the costs of the system remember that you must spend the money up front but you ll have to wait to get 30 of it back on your federal tax return Planning A Solar Power System Why Do You Want a Solar Power System Page 11 How a Sorar Power System Works Let s dive right into how a typical solar power system works We ll identify each major component and explain its function as part of the overall system This typical system might not be exactly the one you need but understanding one is a first step to choosing your own system Household electricity Appliances in your house run on electricity having a voltage of either 120V or 240V This electricity is alternating current AC that oscillates at a frequency of 60 cycles per second or Hertz abbreviated Hz The national electric grid carries electricity at much higher voltages tens of thousands of volts but at the same 60 Hz All power generating plants synchronize their generators to this exact frequency and phase so that any plant may connect to the grid at any time The super high voltage on the electric grid is stepped down to 240V for your house by nearby transformers Alternating current is what allows this voltage transformation Historical note Altern
97. h carry that brand but might give you a better deal on the panels you really want Ask if there is a price break on a full pallet of solar panels If you don t need pallet quantity decide if you can expand your PV array to hold the extras Remember if your panels will be series wired page 74 Buying one extra panel to reach a full pallet does no good if you need two for a series wired pair Ask for a break on shipping charges and a discount if you pay cash wire transfer or cashier s check Getting it shipped Many items can be shipped by UPS or FedEx Ground but heavy items must go by motor freight Read Planning for heavy objects so you re prepared when the vendor asks if you can receive freight deliveries As mentioned there ask how much extra it costs to deliver in a truck with a lift gate Ask if the vendor can ship all or most heavy items at once to possibly save a little on the freight charges and so you minimize the number of times you pay for a lift gate Planning A Solar Power System Final Steps Page 105 Building permits Your local building inspector is the person to ask about building In our case ermits You might need a structural permit an electrical permit or P 5 P P Our county required a residential some other type of permit If you re hiring a professional that person UP P y 5a p P electrical permit because we were should know what permits are required as well
98. h latitude the same location as the sun chart Date Harvest Difference From Dec 21 Dec 21 28 KWH Sept 21 amp March 21 25 8 KWH 7 9 June 21 12 9 KWH 53 9 Table 9 Seasonal solar harvest comparison panel tilt 38 That s dramatic During the six months from September through March PV output varies less than 8 but in June it drops to half its December level Aha you say The sun is higher in summer so why not tilt the panels more to favor summer Okay let s tilt the panels to 60 only 13 from the sun s highest June elevation in Columbus Here are the figures Date Harvest Diff From Dec 21 Diff From 38 Dec 21 22 3 KWH 20 4 Sept 21 amp March 21 24 2 KWH 8 5 6 2 June 21 14 6 KWH 34 6 13 2 Table 10 Seasonal solar harvest comparison panel tilt 60 June is szi the lowest month Even though the 60 tilt boosts June production over the 38 tilt production on the other three dates is lower than the 38 tilt Clearly tilting the panel to favor June helps only a little in summer and hurts in other seasons There is no avoiding the fact a fixed PV array produces less energy in June than in other months Planning A Solar Power System Site Survey Part 2 Page 55 We can conclude that fall winter and spring are best for harvesting solar energy with fixed arrays Production decreases in May drops to its lowest in June and ri
99. harge controller The brackets can hold two charge controllers but we have only one Computer programs Being a computer geek it was natural to use my computer as a tool in planning and monitoring our solar power system I put together a couple of spreadsheets to organize equipment information and help make choices I also wrote two programs first to calculate sun angles and PV production and later to provide a more informative display of system performance than the system controller s Web pages Sun angle program Knowing the sun s azimuth and elevation at specific times on specific dates is vital to finding a location for the solar array and also for predicting power output Plus given the wide range of advice offered online I wanted a way to find the best PV tilt and azimuth The Sun Angle Calculator SAC is the result It displays the sun s position for every hour on a particular date and calculates the solar power the array will produce for each hour It can read a file containing elevations of the local horizon and adjusts the PV power calculations according to where shadows fall Planning A Solar Power System The Dodd Kurylo Solar Power System Page 120 Finally it calculates the best PV tilt and azimuth by running through all combinations and finding the angle that produces the highest power over the year SAC is freely available on my website at http house mdodd com update_solar html SAC Details and a link to
100. he years and understand how stuff works We called in a professional only once and that was because our county s electrical code requires a licensed electrician to make connections to the house wiring Building a solar power system is not rocket science and anyone with a modicum of skill with tools and a willingness to learn new things should be able to do it Disclaimer This document describes a traditional grid tied system with solar panels batteries for energy storage and an inverter It does not discuss other types of systems such as string inverters or solar panels that have micro inverters built into them Our system is only one of several types and brands and what works for us might not suit you I describe several types of equipment but I have personal experience with only one brand Sometimes you ll see a green sidebar with a comment about a choice we made These comments are related to the main text For a description and a photo gallery of our system turn to page 114 Count on doing plenty of research calculating guessing and even head scratching as you read Seek help from solar equipment vendors and manufacturers We found them friendly and helpful Online discussion groups also are good sources of help but be wary of highly opinionated advice e g Dont ever use XYZ batteries they re complete junk Rarely is anything so cut and dried Navigating the document You can read str
101. he cable To install a lug on a cable first remove about 1 to of insulation from the cable and push the bare wire into the terminal s shell Then use a special tool to crimp compress the terminal s shell around the wire making a secure connection Crimping tools can be expensive as a Google search on battery crimping tool reveals Most are pliers like tools that ia 30 homemade TIE CHPIDIRETOO exert tremendous pressure on the terminal shell but there also We bought a 24 bolt cutter for 13 at Wal Mart disassembled it and ground semi circles in the jaws It works well are very inexpensive hammer crimping tools such as this one http www amazon com NOCO D800 Hammer Indent Crimping dp B006VU5WX8 Ask for advice on crimping tools in online discussion groups You might be able to rent or borrow a crimping tool from a local auto shop Large crimped terminals are common in automobile battery and starter wiring An electrician might have a suitable crimping tool you could borrow or rent Some solar vendors will sell you cables cut to your specifications with lugs attached for a price of course Tie points for multiple cables Often multiple cables must connect at one point This usually is accomplished in the battery bank with tie points Figure 32 which are bolts large enough to accommodate several terminal lugs or metal bars with holes for individual cables and screws to clamp the ca
102. he fix was easy I bought some wire and flexible conduit locally and cut them to reach my charge controller Planning A Solar Power System The Dodd Kurylo Solar Power System Page 119 Battery rack The Outback Power integrated battery rack http www altestore com store Deep Cycle Batteries Enclosures for Deep Cycle Batteries Rack Type Battery Enclosures Outback Power 3 Shelf Integrated Battery Rack for 48V Systems p9859 is very nice but costs 1 600 After balancing the cost against the convenience we chose a heavy duty adjustable steel wire shelves from Global Industrial http www globalindustrial com p storage wire shelving chrome 74 h nexel chrome wire shelving 24 w x 24 d for 113 plus shipping The unit comes with four 24 x24 shelves and we bought two more for 27 apiece http www globalindustrial com p storage wire shelving chrome chrome wire shelf 24x24 with clips 2 the vendor photo is of a wider shelf Three 175A Figure 63 Battery rack circuit breakers cost 336 so we had our battery rack for 1 3 the cost of the commercial product Each shelf can support up to 800 pounds We use the lower three shelves for the 12 AGM batteries 1 572 pounds total and the top two for general storage in this our yard equipment room The shelf above the batteries holds the system owner manuals and has space for the generator remote start module that is attached to the extended brackets holding the c
103. he inverter s output to the solar box See Install and use the solar breaker box early on page 99 for more on this Planning A Solar Power System How a Solar Power System Works Page 15 Gettinc SrARTED Estimatinec ELECTRICAL Loaps The first step in planning a solar power system is to estimate the electrical loads for the appliances you want to run from solar power Electrical loads come first because they determine the size of the inverter and also the number of solar panels you ll need Once you have a feel for the system size you can proceed with the site survey starting on page 30 Note See Finding power consumption from appliance nameplates and Measuring power consumption yourself on the following pages to learn how to find each appliance s power consumption To begin you will need a power audit table or computer spreadsheet where you can list the appliances you want to run on solar power along with their power consumption Additional columns show the number of hours per day each appliance is turned on and the appliance s daily power consumption in kilowatt hours See Table 1 for an example You will need two such tables one for solar power and another for grid power See The power audit for detailed instructions But first let s discuss kilowatts Watts to kilowatts Appliance nameplates see page 20 list power consumption in watts W but designing a solar power system quickly cmpels us to think in terms of ki
104. he package along with their equivalent or replacement wattage For instance a 60W replacement CFL draws 13 watts CFLs also have their actual wattage stated with the information printed on the base Figure 4 Figure 4 CFL wattage Planning A Solar Power System Getting Started Estimating Electrical Loads Page 21 Measuring power consumption yourself You can measure the wattage of any appliance that plugs into a standard 120 VAC outlet with an electricity usage monitor such as the KILL A WATT which is manufactured by P3 International This handy device comes in several models and is widely available from Internet vendors For example the P4400 model shown in Figure 5 is available from Amazon for less than 18 00 http www amazon com P3 International P4400 Electricity Monitor dp BOOOO9MDBU ref sr_1_1 ie UTF8 amp qid 137549341 8 amp sr 8 1 amp keywords kill a watts To use the KILL A WATT plug it into a standard 120 VAC receptacle then plug the appliance s power cord into the receptacle on the front and turn on the appliance Figure 5 shows the monitor plugged into a kitchen receptacle with an operating toaster plugged into the monitor The display shows that the toaster is drawing 1 062 watts KILL A WATT slightly more than 1 KW The KILL A WATT has five buttons to display household voltage Volt current Amp power Watt frequency Hz and power consumption over time More about this red
105. her sites make similar claims That claim is wrong Not all grid tied systems shut down when the grid fails only those without batteries do 4 grid tied system with batteries will continue to operate and supply household power when the grid goes down Re read the first sentence in red above It defines a grid tied system as one capable of selling power Just because a system is capable of selling power doesn t mean it is permitted to do so Utilities having a vested interest in the safety of their linemen require verification that a system stop selling Planning A Solar Power System Definitions and Formulas Page 6 solar power the instant the grid goes down The system can continue to supply solar power to the house it just can t send it to the grid So once again and finally In this document a grid tied system is one that is connected to the grid and 1s capable of selling excess solar power to the utility Off grid or off the grid refers refers to a power source or living environment that does not require the use of commercial electric lines Wo Grid down The term used to describe a power outage Also called grid outage grid failure or m power failure Examples 77e grid went down during tbe storm My system bandle a 24 bour grid outage Electrical formulas We can t design a solar power system without using a few simple formulas Ohm s Law Ohm s Law is the basic formula that relate
106. here will you put it The best location for the inverter and by extension the batteries and other equipment is indoors close to the household circuit breakers It should have convenient access and sufficient space on a solid floor to hold hundreds of pounds of batteries Inverters usually hang on a wall so you ll need a wall that can support approximately 100 175 pounds Planning A Solar Power System Choosing an Inverter Page 28 An unheated garage or shed may be suitable but there could be concerns with temperature extremes or humidity Check the environmental specifications in your candidate inverter s data sheet as well as the data sheet for your candidate battery in Choosing Batteries Done Good job You have identified an inverter that will work and you know how much it costs and the vendors who sell it That s all for now File your inverter information and let s start learning about batteries Our choice We chose the Outback Power Radian 8 KW inverter to avoid several issues we saw with an earlier model inverter 1 Capacity Without the Radian s 8 KW capacity we would have needed twa smaller inverters 2 Integrated The Radian requires fewer accessories than the older model Installation involved attaching one wall bracket and hanging the inverter on it instead of mounting multiple components and cabling them together 3 Load center This cabinet is designed expressly for the
107. hing on the cut end One of these two cables connects to a PV positive cable and runs through a bushing to a circuit breaker in the combiner box The other cable connects Routing PV cables Plan to route the cables along the support structure and behind the PV panels Cables must not drape suspended only by the PV junction box and the combiner box Also surprisingly for a solar application the PV cables sbould not be left exposed to direct sunligbt as they will deteriorate from UV light Consequently the cables should be routed behind the panels The cables in Figure 23 are routed along the horizontal wooden support member Cables run through a short length of PVC conduit where they cross a gap between panels circled and inset detail Obviously the cables in this photo are not yet connected to the combiner box on the right Ultimately both cables from each panel will be routed along the structure to the box to a PV negative cable and runs through a bushing to the negative TBB Important If you have multiple rows of Extension cables typically are sold in lengths of 15 30 50 and 100 Careful planning PV panels their cables must be rotected on the run to the is needed because the cables P is cost around 1 00 per foot P rspruep pos Mipu mally means enclosing them in Make a plan before you start 8 conduit for a roof array or in cutting them up Accurately conduit buried i
108. hink of one solar panel as roughly 3 wide by 6 tall Here are actual dimensions of four PV panels in 2013 290 watts 37 x 77 Figure 10 270 watts 37 x 66 200 watts 39 x 56 Figure 11 140 watts 25 x 59 The two drawings on page 46 represent two sizes of PV panels at a scale of 4 1 Figure 10 shows four 290W panels measuring 37 wide by 77 tall and Figure 11 shows four 200W panels measuring 39 wide by 56 tall You can print these and use them to visualize the approximate space you ll need To check your PDF reader and printer print this page and measure the gray areas Those in Figure 10 should be 0 77 x 1 6 Those in Figure 11 should be 0 8 x 1 17 If so then you can use them with a 4 1 scale drawing or photo of your house or property For other panel sizes draw your own to the same scale using the dimensions from the panel s data sheet This gives a rough estimate of the space needed Planning A Solar Power System Site Survey Part 1 Page 45 Figure 10 Four 37 x77 290W panels U Figure 11 Four 39 x56 200W panels EE What if the panels don t fit There are several things you can do if your candidate PV array is too large for the available space 1 Choose higher power panels Recall that the higher a panel s capacity the fewer of them you ll need 2 Choose ower power panels Huh Compare Figure 10 with Figure 11 Say you need 10 of the 290W panels in Fi
109. his Method B Both panels are tilted the same amount but Method A calls the tilt angle 25 and Method B calls it 65 Why the difference I don t know why Method B is used so much maybe it s tradition But Method A directly matches how the sun s elevation is measured and this makes it easier to understand the math to calculate a solar panel s performance as presented earlier in How much solar energy does a panel collect on page 51 The sun s elevation is measured in degrees above the horizon The horizon s elevation is 0 If the sun s current elevation is 65 above the horizon and you want to tilt the PV panel to directly face the sun it makes sense to tilt it backward 65 and say the tilt angle is 65 Using Method B that same panel s tilt angle would be 25 That is the panel is tilted 25 from horizontal toward the sun This might seem like semantics but Method B adds a non intuitive step to calculations As you saw on page 51 we use the cosine of the angular difference between the panel s tilt and the sun s elevation to calculate the amount of solar energy collected by a PV panel With Method A we can simply subtract one angle from the other then take the cosine Method B demands that we first subtract the panel s tilt angle from 90 or else subtract the sun s elevation from 90 then subtract the result from the sun s elevation and then take the cosine of the result Why not use the same frame of referen
110. house plan for a solar power system from the outset Tell your electrician that you want certain branch circuits to run to a special solar breaker box while the remainder of the branches must run to the grid or main box or boxes Install and use the solar breaker box early Whether you are installing a solar breaker box in an existing or a new house it is a good plan to do this a few months Zefore you are ready to hook it up to the actual system Explain to your electrician that the solar power system will be added later and he should wire a branch circuit from the grid breaker box to the main breaker in the solar box The branch grid box circuit should have a breaker rated for current the same as or slightly less than your inverter s maximum output current Read the next three sections to learn why and what you ll do with this setup Calculating inverter output current We need to know the inverter s AC output current when it it producing full power Recall the power formula P Ex I on page 7 A variation of this formula to find current from power and voltage is I P E or current equals the power divided by the voltage If your inverter is rated for 6 000 watts at 240VAC then I 6 000W 240V 25 amps An 8 KW inverter has a maximum current is 33 3A Write the current here then use Table 24 to choose a circuit breaker to feed the solar box from the grid box Inverter s output current at maximum power amps
111. ilestone images in case you decide to have prints made later Nice 4 x6 and even 8 x12 prints can be made from an image with a resolution of 1200x1800 pixels There is no need to make very high resolution images unless you plan to have large prints made Medium resolution image files are smaller and easier to email A date and time imprinted Planning A Solar Power System Final Steps Page 108 on images by the camera is convenient for milestone photos and can be helpful when documenting equipment problems as described below Keep your camera handy to Mark project milestones even minor ones with photos Take photos of a damaged package before opening it so you can file a claim with the carrier Photograph the manufacturer s exterior labels on cartons before discarding them This way if the wrong item is inside you can email the photo to the vendor and let him decide if he shipped you the wrong item or if the manufacturer mislabeled the carton Inventory everything in a carton If anything appears to be missing lay out and photograph the contents so you can show the vendor what you received Take photos of any component that gives you fits during assembly As the saying goes a picture is worth a thousand words Call the support desk describe your confusion and ask if you can email the photo so you both can be looking at and talking about the same thing Planning for heavy objects Make no mistake sola
112. ing when you re finished with the website Planning A Solar Power System Introduction Page 2 DEFINITIONS AND FoRMULAS Electrical definitions These are common electrical terms you ll need to understand and plan a solar power system Voltage is electric potential energy and is measured in volts abbreviated V and represented in formulas by the letter E Example The lamp runs on 120 volts ox the lamp runs on 120V Current is the flow of electrons through a conductor such as copper wire Current is measured in amperes usually abbreviated amps or A and represented in formulas by the letter I Example 77e current is 3 amps or the current is 3A Resistance is anything that impedes the flow of current through a circuit Current flowing through resistance creates heat Resistance is measured in ohms and represented in formulas by the letter R The Greek symbol Q is used to designate the number of ohms of resistance Example In the formula R is 15 ohms or in the formula R is 15Q Energy is the capacity of something to perform work Soar energy falls on PV panels which convert it to electrical energy Electrical energy is stored in batteries Power is the rate of doing work measured in watts W or kilowatts KW and is represented by the letter P A kilowatt is equal to 1 000 watts Example 4 5 000W inverter or a 5 KW inverter Ampere hour or amp hour is the amount of energy stored in a battery that will allow on
113. ingle string can be your battery bank If not use two strings for a bank capacity of 53 2 KWH or three strings for 79 8 KWH Duplicate the entire system You can install a second inverter and a second battery bank to power it plus a second PV array to charge the batteries Ask your vendor if you can stack inverters in this configuration If not you will need two solar breaker boxes one for each inverter and you must split the solar circuits between them Doubling the battery bank doubles the energy storage capacity and by splitting the solar loads might be able to use smaller inverters For instance instead of one 6 KW inverter you d could use two 3 KW inverters Sidebar continues on the next page Planning A Solar Power System Choosing Batteries Page 40 Hitting the target storage capacity continued Buya generator A generator can power your home and charge your batteries at night and when the sun isn t shining It wouldn t need to run continuously a few hours to partially recharge the batteries and run appliances then off for a few hours to run appliances from batteries Lower your target KWH Ask your family what lifestyle changes would be acceptable while running on solar power Think about 1 Reduce the solar load 1 in Table 6 Do you really need to use those appliances Can you cut back anywhere 2 Reduce the desired solar run time 2 in Table 6 Maybe it s okay to have only one d
114. ions post questions on solar power forums and check the manufacturer s warranty period and terms Physical size They have to fit in your available space Cost per watt When you buy PV panels you re really buying energy production and cost per watt is the correct way to evaluate price 226 for panel A seems about the same as 229 for panel B until you discover that A is a 100W panel and costs 2 26 per watt while B is a 235W panel costing 97 per watt Panel B is the best deal if you have space for panels that size All solar vendors include cost per watt in their PV panel listings Most allow you to sort the list by clicking the column header PV output voltage In general choose PV panels with the highest open circuit voltage abbreviated Voc The reasons for this are technical and are explained on page 73 Mounting method Generally PV panels intended for fixed installation can be selected without any consideration of the mounting system But if you plan to install panels on tracking mounts you should get detailed information about the size and number of panels your candidate mount can hold Tracking mounts are expensive so discovering you need to buy another mount to hold two remaining panels is an unpleasant surprise Let s move on to the final site survey then we ll come back to solar panels on page 69 Planning A Solar Power System Choosing Solar Panels Part 1 Page 48 Site Survey Part 2 In Site
115. iring increases voltage Parallel wiring does not increase voltage P group 8 g 8 g So if you have a 12V battery capable of storing 1 2 KWH and you add a second identical battery either in series or in parallel your battery bank has a capacity of 2 4 KWH Add two more identical batteries four total and you re up to 4 8 KWH Figure 6 shows a string of four 12V AGM batteries connected in a string to produce 48V The positive terminal on each battery is on the right and the negative terminal is on the left In this installation short metal bars connect each battery s positive terminal to the adjacent battery s negative terminal On the left side a heavy black cable runs to a common tie ba t Figure 6 String of four AGM batteries Planning A Solar Power System Choosing Batteries Page 32 point to connect with the negative cables from two other identical strings On the right a heavy red cable runs to a 175A circuit breaker and then to a similar tie point Connecting batteries together creates a battery bank Figure 7 shows 12 6V flooded cell batteries wired as a bank of three strings of four batteries ignore the unrelated battery in the lower right corner Each string of four batteries produces 24V Notice how short loops of black cable connect each 1 ifs gt PP CN AK due es ee battery s positive terminal to the adjacent battery s uq y negative terminal instead of the metal bars shown in Fig
116. is voltage is sensed by the measuring equipment System controller The system controller monitors and controls the charge controller and inverter and possibly other components as well It has a display and buttons to allow you to see the state of all system components Figure 39 shows the Outback Power MATE system controller The screen displays current system status as well as other Our choice a factory wired load center Our decision was easy when we discovered that Outback Power offers a factory wired load center for the Radian inverter It bolts directly to the bottom and comes with all circuit breakers and shunts installed along with wires already cut to exact lengths with the insulation on the ends pre cut and ready to strip The factory wiring saved a lot of work and eliminated much confusion The load center was a significant factor in choosing the Radian inverter in addition to the Radian s 8 KW rating Figure 39 System controller component status when one of the buttons is pressed in this photo the bar PV array is producing 3 2 KW top bar and the house is using 1 5 KW bottom bar The right half of the split center bar shows the system selling 0 1 KW 100W to the utility This small amount is barely visible on the bar graph Planning A Solar Power System The Complete System Page 93 The numbers and symbols below the bottom bar are a bit cryptic but they sh
117. is document grid tied means a solar power system that is connected to the electric power grid and is capable of selling excess solar power to the utility Why the emphasis Because grid tied is a term with several meanings depending on where you look What is the term for a system that is connected to the grid but doesn t sell power Sadly there is no standard term to describe such a system Grid connected might sound like a good choice but according to this Wikipedia article http en wikipedia org wiki Grid connected photovoltaic power system a grid connected system can sell power to the utility How is that different from grid tied Systems that are connected to the grid but do not sell power are rare Like a grid tied system these supply grid power to the house when the sun isn t shining When the sun is shining the system supplies solar power If household demand exceeds available solar power the system uses grid power make up the deficit The only way these are different from grid tied systems is they don t sell power This document does not call these systems grid tied and usually clarifies the term not grid tied with not permitted to sell or does not sell nearby It gets worse This website http www naturalnews com 036194 solar system grid tie power grid html shouts Reality check When the power grid goes down all grid tie solar systems will go down with it In other words no system no household power Ot
118. k of it as moving forward with open eyes You have defined the essentials of a solar power system and there is only one more design decision to make the size of the solar array 16 Divide the KWH in 15 by the daily appliance KWH in 1 to get the number of days the batteries will power the appliances This should be close to 2 if you ve done all the math correctly 17 Enter the cost of your candidate battery 18 Multiply 17 and 14 to see the cost of your battery bank excluding any support structure This completes Table 6 You now have a good idea of the batteries needed by your solar power system If you don t like what you see consider the suggestions in the sidebar then search for more suitable batteries and go through Table 6 again There is another method don t use batteries You can buy systems that have PV panels and an inverter but no batteries Here is a 4 2 KW example http www affordable solar com store grid tie kits A ffordable Solar 4 200W String Inverter Kit These systems power the house only while the sun is shining not at night or on cloudy days Revisit your reasons for wanting a solar power system and decide if this would work for you Read the yellow sidebar Hitting the target storage capacity on the next page and adjust your choices in Table 6 if needed When you have have defined a satisfactory battery bank in Table 6 skip to Site Survey Part 1 to start thinking about solar panels Plan
119. l for just those four dates not for the entire year Also the September 21 March 21 value is added wice to the 4 day total because it represents two dates with identical PV production A 12 day total in the bottom row shows the total power produced for the 21 day of each month January through December This was not included in Table 9 because there we were comparing just panel tilt angles Now the total for those 12 days helps us evaluate overall annual performance for each tilt angle Energy Difference From Date Production Dec 21 December 21 29 7 KWH September 21 amp March 21 24 3 KWH 18 June 21 10 1 KWH 66 4 day total 88 4 KWH 12 day total Jan 21 Dec 21 264 6 KWH Table 11 Latitude 40 north 4 KW PV array tilt 20 Energy Difference From Date Production Dec 21 December 21 29 5 KWH September 21 amp March 21 25 KWH 15 June 21 11 KWH 63 4 day total 90 5 KWH 12 day total Jan 21 Dec 21 270 6 KWH Table 12 Latitude 40 north 4 KW PV array tilt 25 Planning A Solar Power System Site Survey Part 2 Page 59 Table 14 Latitude 40 north 4 KW PV array tilt 35 Energy Difference From Date Production Dec 21 December 21 29 1 KWH September 21 amp March 21 25 5 KWH 12 June 21 11 8 KWH 59 4 day total 91 9 KWH 12 day total Jan 21 Dec 21 274 7 K
120. l fuel by truck to aR open ane oe ners ONES a large tank i 5 be sheltered from rain and snow so Generator output capacity we put it inside a plastic doghouse It makes sense to install a generator with approximately the same with ample ventilation output capacity as your inverter because if your inverter can power all A P PA SE i y P It has remote start capability and of your solar appliances then the generator can do the same In reality E ROTER a slightly smaller generator probably would do fine In Choosing an a a a the Inverter you might have sized your inverter as much as 40 larger a tor enin bourses full load from the attached fuel tank longer at reduced load than your actual solar appliance load This capacity probably isn t necessary in normal times let alone during a long term grid outage On the other hand if your generator is larger than your typical average load the system might be able use the extra power to recharge your battery bank Explanation The inverter might have a built in battery charger that operates on AC power and independent of the charge controller connected to the solar array This built in charger can charge batteries from the grid or from an AC generator connected to the inverter This is not possible if the inverter cannot accept a generator s power or does not have a built in AC powered battery charger Recommendation Choose a 240VAC generator with a power output equal
121. lculating the sun s We chose a tilt angle of 42 for our azimuth and elevation for every hour then subtracting those kesom ar E EIE from the panel s azimuth and tilt then multiplying together Interpolating Table 23 between 35 and the cosines of those angles for the factor by which to multiply 40 it looks like 39 or 40 would have the PV output power Again these calculations are performed peen closer to optimal but 42 is close gt for every daylight hour in every day of interest enough for us Whew Let s let a computer do the work This table shows optimal tilt angles for north latitudes between 25 north of Hawaii and 70 northern Alaska using results from my Sun Angle program page 120 The PV array is assumed to be pointing due south azimuth 180 I recommend choosing a tilt angle from this table then doing any additional research you feel is necessary to verify that it is the best angle for your location 4 KW PV array 12 day total production North latitude Optimal panel tilt Jan 21 Dec 21 223 KWH 247 KWH 262 KWH 277 KWH 292 KWH 297 KWH 297 KWH 300 KWH 290 KWH 244 KWH Table 23 Optimal year round fixed panel tilt by latitude Remember that this table assumes non adjustable PV panels pointed due south If you choose adjustable mounts tilt the panels on March 21 approximately 23 higher than the table s optimal tilt angle for summer and on September 21 approximately 23
122. load What happens if the inverter s capacity is exceeded Don t worry it doesn t catch fire or explode It merely shuts down Everything being powered from the inverter stops running Lights go out the TV quits and the computer shuts off You can walk to the inverter or system controller and press a few buttons to start the inverter again and restore power Needless to say you first should turn off the appliance s that caused the overload in the first place Determine an approximate inverter size Look at your total solar power load Let s say it is 4 2 KW as in the example shown on page 17 At minimum your inverter should be large enough to power this load But it also should have some extra capacity above the total solar power load Give serious thought to sizing your inverter 20 to 40 larger than your total solar power load With the 4 2 KW in this example you would want an inverter rated for 5 KW 19 or 6 KW 443 The higher rating could avoid an inverter shutdown from an unexpected heavy load Fine tuning the inverter size It might seem that the inverter is very large Do you really need all that capacity Is there any way to reduce the inverter size Yes This can be tricky and might force you to make some compromises and assumptions that you ll have to live with forever Let s take a look Suppose your power audit includes these high power appliances in addition to lower power appliances like light fixtures TV an
123. lowatts KW You don t tell a vendor you want to buy an inverter rated for 3 864 watts You say I need a 4 KW inverter A kilowatt is 1 000 watts If as is usually the case an appliance s power consumption is stated in watts divide that number by 1 000 to get kilowatts and enter the result into the power audit table Example A microwave oven s label says it draws 1800W Divide by 1 000 move the decimal point three digits to the left and you have 1 8 KW A 60W incandescent lamp draws 0 06 KW and a 13W CFL draws 0 013 KW Planning A Solar Power System Getting Started Estimating Electrical Loads Page 16 The power audit Here is a sample power audit Table 2 and Table 3 are just like it but are empty for you to use You can print those pages or make your own computer spreadsheets to hold the same information Total Hours KW KW On per KWH per Appliance No Load Load Day Day Ceiling light two 13W CFLs apiece 5 0 026 0 13 8 1 04 Desktop computer 1 0 175 0 175 4 0 7 45 LCD television 1 0 22 0 22 5 1 1 Well water pump 1 1 3 1 3 0 2 0 26 Refrigerator 1 0 275 0 275 4 1 1 Microwave 1 1 8 1 8 0 1 1 8 Washing machine 1 0 3 0 3 0 1 0 03 Table 1 Sample power audit Notice the No column This shows how many of that appliance typically are operating a the same time This is important If you have 12 ceiling lights but on average only five are turnedon at on
124. me position in their Negative Feed to Positive Feed to Charge Controller Charge Controller and inverter and inverter strings as are all blue 2 cables and all Breaker 1 2 3 OQ OQ OQ O Battery Battery Battery Battery OQ O OQ O Battery Battery Battery Battery OQ O O Battery Battery Battery Battery Figure 33 Equal cable lengths in battery strings blue 3 cables Notice that the tie points in Figure 33 are drawn as wide bars but Breaker in fact they should be single points such Negative Terminal Tie Point as those in Figure 32 Here is how the Positive Terminal Tie Point Breaker rule is applied looking from left to right in Figure 33 Green Negative cables from all strings to the negative tie point must be equal length Blue Cables in the same string position from a battery s positive terminal to the adjacent battery s negative terminal must be equal length Notice that the 1 2 and 3 cables are not the same length But all 1 cables are the same length as are all 2 cables and all 3 cables There is no requirement that all battery interconnection blue cables be equal length only that the blue cables in the same string position be equal length Red Positive cables from all strings to their circuit breaker musts be equal length Teal Positive cables from all circuit breakers to the positive tie point must be equal len
125. mple Columbus Ohio is at latitude 39 57 north of the equator To convert DMS to decimal degrees divide the number minutes by 60 and add the result to the degrees In decimal form Columbus s latitude is 39 57 60 39 95 north Let s round this to 40 for the remainder of this discussion You can find your latitude online at http www worldatlas com aatlas latitude_and_longitude_finder htm Find it and write it here or in your solar planning notebook Your latitude Planning A Solar Power System Site Survey Part 2 Page 49 Finding true north All sun positions are based on true not magnetic north This section explains how to find true north at your location Use a compass One way to find north is to use a compass But a compass points to the magnetic north pole not the true north pole so you can t use the needle s reading directly To use a compass you need to know the magnetic declination for your location This is easy to find with online calculators such as this one at NOAA http Avww ngdc noaa gov geomag web A westerly declination means the compass needle points to the west of true north and an easterly declination means the compass needle points to the east of true north Locations east of a north south line running roughly through Des Moines and St Louis have westerly declination while locations west of that line have easterly declination Figure 12 shows a compass set for 10 wes
126. much solar power it can accept from the PV array to charge batteries and run appliances See page 91 for details Even if a super sized PV array could produce more power it won t if the charge controller doesn t accept it But this is maximum PV power which occurs only on a few days per year Even if the charge controller can t use the array s maximum power it can use lower off peak power that the array produces most of the year Recommendation Make your array as large as possible to capture as much solar energy as possible within the constraints of your space and budget up to about 150 of the charge controller s capacity You ll lose some peak production but will capture more off peak power during the year Next question How many PV panels do you need and will they fit in your available space To answer this question you must make two initial assumptions Target PV array capacity and PV panel power 1 Target PV array capacity This is a balancing act Refer to your candidate inverter s total KW output from the right column in Table 4 and recall the information about PV size vs charge controller capacity above As a first estimate enter 50 to 100 of the candidate inverter s KW output or 150 of the charge controller s capacity in the Target PV KW column Example With a 5 KW candidate inverter and a 3 KW charge controller choose 5 KW for the PV array size 2 Candidate PV panel power Browse PV panels on vendor website
127. n can ring a bell and you suddenly understand the big picture Follow instructions exactly even if you don t fully comprehend everything they re telling you If something doesn t make sense read that instruction again and positively identify the physical components Make sure you aren t looking for a positive TBB when the instruction said negative TBB Go back to a previous instruction to verify you didn t confuse a component earlier that is leading you astray now Perform carpentry or masonry Building a wooden PV panel support requires basic carpentry skills Cutting 4x4 lumber is a challenge with most portable circular saws so consider using a reciprocating saw Sawzall or a chainsaw for these Use galvanized hardware to avoid rust You might need to bore holes in concrete to bring PV feeder cables inside the house Hire this out if the job is too daunting You probably will need to hang the inverter on a wall so you ll want a stud finder and a drill plus lag bolts and wrenches to tighten them Enlist a helper to hang a heavy inverter Don t hesitate to call in a professional for any task beyond your capabilities Many handymen are willing to come out for even few hours of work usually enough for one or two tasks Take photos There is no requirement to take pictures during the project but they can be valuable now and you might appreciate them in the future Set your digital camera to record medium resolution m
128. n in a trench for measure the distance of PV a ground installation See panels from the combiner box 5 uiu dence Cables from the array to the n system for more information about trenches Be sure to First check if any panels include the extra cable that will are close enough for their be needed to enter and exit the built in cables to reach the trench through conduit and combiner box s circuit breakers service head Figure 25 and and negative TBB Remember add 16 more for a service that you ll need to cut off the loop drip loop at each end connectors on these cables so they can pass through the bushings and connect inside the box For more distant panels measure the length needed to extend each panel cable to the connections inside the combiner box Include extra to go around corners You need to measure each cable Planning A Solar Power System Choosing Solar Panels Part 2 Page 79 because the distance to the combiner box might not be the same if they come out on opposite sides of the PV junction box Allow for a 180 turning loop if a cable exits the PV junction box on the side away from the combiner box Planning to cut the PV extension cables Now for the tricky part How to best cut the costly extension cables to get two cables from each one Each resulting extension cable will have an MC4 connector on one end to attach to a PV cable and a cut end to connect to a circuit breake
129. ncrete footers unless person Earthquake auger shown local code requires them but you will need here is not inexpensive but it is very j Figure 45 Power holes in which to place the support posts useful for many projects around the earth auger Spread a layer of gravel in each hole for the house including vertical tilling for post to rest on and add concrete in the hole new landscaping bushes and trees around the post to secure it Planning A Solar Power System Final Steps Page 107 A commercial mount might probably does require footers for its supports Check with the manufacturer or vendor about footer requirements before choosing a ground mounting system Be sure you have the equipment and stamina to dig them Follow instructions It is imperative that anyone building a solar power system is able and willing to follow instructions Even though installation instructions for equipment and PV panels are written for non professionals they do not include tutorials Furthermore building inspectors expect you to build according to code so you should know what the code requirements mean Seek help if you need it First download and read the installation and owner manuals for every piece of equipment you will buy If you have questions call the manufacturer s customer support staff Don t hesitate to ask your vendor for help Search the Internet for definitions of unfamiliar terms Often a simple definitio
130. nd destroy the solar cells inside Also trees grow leaves which float to the ground in the fall Even if the panels are not directly beneath trees leaves still can land on the panels Panels won t produce any electricity if they are covered with leaves Ideally your panels will be far enough from trees for leaves not to be a concern If leaves fall on panels you should sweep or blow them off Planning A Solar Power System Site Survey Part 1 Page 42 There is not much you can do to prevent snow from falling on solar panels The panels are tilted which helps snow slide off eventually Dry snow might slide off at first but soon starts to build up Wet snow accumulates quickly Figure 9 shows several inches of wet snow on panels tilted 42 at midday following a storm The sky is still overcast but the panels have warmed slightly from UV light through the clouds and the snow is beginning to slide off Warming accelerates as more and more dark solar cells are exposed Figure 9 Snow on solar panels Notice the snow buildup at the bottom of the rightmost panel The lower edge of this panel is only about 9 from the ground so snow sliding down the panel piles up at the bottom Snow sheds more readily from panels with plenty of ground clearance Planning A Solar Power System Site Survey Part 1 Page 43 How many panels do you need The charge controller factor The charge controller has a limit to how
131. ne day or a range of dates In nine months of operation the database has 89 000 records I plan to clear the data each January since there is no real value in storing historical data indefinitely The solar power monitor is not available on our website because it is so complex and requires so much supporting hardware and software I am happy to share the C program code and the database schema if you wish to collect data from your own system Please email me at mike mdodd com Cost This discussion isn t complete without mentioning the cost We paid 21 500 for our system excluding the generator We claimed the 3096 federal tax credit on that amount resulting in an out of pocket system cost of 14 350 plus the cost of the generator The system has lowered our electric bill by about 1 00 per day on average over the nine months of operation At this rate it will take us 39 years to recoup the cost which is longer than the expected life of the PV panels not to mention the batteries Is the system worth the money Clearly not from a monetary perspective but that s not the whole story We could spend far more than 14 000 on a new car yet we don t expect to recoup that money by driving the car We buy a car and reap the benefits of owning it Likewise we don t expect to recoup the cost of the solar power system We use the system daily and appreciate the convenience and other benefits it provides Planning A Solar
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133. ning A Solar Power System Choosing Batteries Page 39 Hitting the target storage capacity A limit on the number of strings is the only thing that prevents your candidate battery bank s capacity from meeting your target storage capacity Without this limit 13 would hold a higher number and you d be good to go Consider these suggestions to hit your target capacity Try to eliminate the restriction Call vendors and battery manufacturers to determine if all of the batteries you listed in Table 5 have the string limit Perhaps a different technology e g flooded cell vs AGM might be okay State the problem a limit on the number of strings Woo producing n volts apiece and ask for advice Choose different batteries Look at Table 7 Suppose you have three strings of four GC15DT 6V 1 38 KWH flooded cell batteries yielding 24V and 5 52 KWH per string and 16 56 KWH for the bank Cost 1 452 You could choose the PVX 3050T AGM battery with 1 83 KWH giving 7 32 KWH per string and 22 KWH for the bank Cost 2 688 This is a 3396 capacity increase just by changing to AGM batteries Does the result hit your target Use lower voltage batteries The number of batteries in a string depends on their voltage The 2 volt L 16 RE 2V battery in Table 7 stores 2 22 KWH and you d need 12 of them per string to get 24V Together those 12 batteries store 26 6 KWH That s 6196 more Cost 1 956 If 26 6 KWH hits your target that s
134. nning to see why the rosy pictures of solar power panels don t tell the entire story You can have a solar power system for backup use as a primary off grid system or to sell power to the utility Do you want to make the investment What compromises are you and your family willing to make Don t accept the solar power mantra at face value Decide for yourself if the benefits of solar power are worth the money and effort Here are some more reasons you might want a solar power system despite the inefficiencies and costs involved Two or more reasons might be related such as green energy and independent living No problem choose the relevant ones and decide if they give you the value you want Reason 2 Backup power Perhaps you live in an area where commercial electrical Our first choice backup power Where we live power often fails during ower is frequently interrupted by storms or other events A R P d y P y storms We primarily wanted a source of solar power system can act like a large uninterruptable power P y 8 P P backup power supply UPS for your house You might not even know when the grid power fails unless you re using a high power appliance at the time Your computer and TV will stay on and the lights might not even flicker How much value do you place on this convenience Planning A Solar Power System Why Do You Want a Solar Power System Page 9 Reason 3 Independent living Do you live
135. o Figure 14 Example sun chart View the chart as if you are looking south in the northern hemisphere Seven blue arcs show the sun s path across the sky for the 21st day in seven months December through June The remaining months use the same curves reading down from June In other words use May s curve for July April for August March for September and so on December is always only December The red lines represent solar time Follow the black lines down and left from the point where a red line crosses a blue line to find the sun s azimuth and elevation for that hour and date For clock time remember to add an hour to the red solar times if Daylight Saving Time is in effect at your location and remember that solar noon varies across a time zone page 5 The azimuth and elevation values represent sun angles exactly as described in How much solar energy does a panel collect on page 51 Use them directly when finding cosines for the solar insolation formulas Planning A Solar Power System Site Survey Part 2 Page 57 Visit http solardat uoregon edu SunChartProgram html to make a sun chart for your location You might want to print it and use a highlighter to color the curves during dates and times when your PV site is shaded Choosing a panel tilt angle No single tilt angle is best for the entire year any fixed angle is a compromise As before if you are planning to install tracking mounts you can skip this se
136. o high choose a larger cable or parallel cables and recalculate until the loss is acceptable Planning A Solar Power System Choosing Solar Panels Part 2 Page 75 More power losses After the solar panels harvesting only 15 of the solar energy falling on them and the power lost to feed cable resistance are there more losses Yes The charge controller becomes warm during operation so power is lost there The inverter M d ULL ti sek F Z Indegting 1 8 KW 10 Figure 20 Power loss illustrated does not convert 100 of DC power to house current so some is lost there too It is difficult to predict how efficient a system will be unless the manufacturer specifies it This screen shot of a solar power monitor program illustrates the situation The PV array is producing 2 3 KW The batteries are receiving 200W 0 2 KW for charging and the inverter is inverting 1 8 KW That totals 2 KW where are the remaining 300W They are lost as heat in the charge controller and inverter a 13 power loss in those two components Bottom line Expect a 8 to 15 power loss in the system components after the power lost in the feed cables from the PV array to the charge controller How will the panels be wired As explained above it is beneficial to connect PV panels in series to raise the voltage Voc fed to the charge controller But almost certainly the number of panels that can be wired in a
137. olar Power System Definitions and Formulas Page 7 Why Do You Want A Sorar Power System The first step in planning a solar power system is to know why you want one Do you want your house to be completely independent from the electrical grid Do you want backup power when the grid goes down due to a storm or other event Do you favor using green energy instead of fossil fuel energy Whatever the reason you should have a clear idea of what you re trying to accomplish because the next question has to do with value How much will the system cost can I afford it and will it be a good value Value is a subjective factor Only you can decide if something is worth the money and effort it requires Example You can buy eight solar powered path lights for 30 bucks at Lowe s You might consider these to be a great value if you need to illuminate a walkway at night but maybe you d change your opinion to a complete waste of my money if they aren t bright enough or if you discover a year later that the rechargeable batteries have died and must be replaced at a cost higher than the original cost of the lights Note the if This example is not intended to belittle solar powered walkway lights Reason 1 The solar energy myth Get free power from the sun Never pay an electric bill again Go solar There is much hullabaloo these days about green energy and solar energy in particular It s easy to imagine a remote cabin with a couple of s
138. olar array the county required us to bury the feed cables in a trench 18 deep We needed 200 of cable after a curve to reach the yard equipment room where the system is installed Initially we planned to use 8 copper wire but its 21 resistance power loss was far too high Larger copper wire was very expensive and hard to find so we chose 2 aluminum wire instead Two runs for the positive cable and two for the negative cable lowered the resistance power loss to a much more reasonable 4 296 Planning A Solar Power System The Dodd Kurylo Solar Power System Page 115 We rented a trenching machine which did the job but gave us fits with the many large granite rocks peppering our soil We were fortunate that the machine dug up most of them without breaking a blade tooth but five or six were so large we had to dig them out with a root chopper and a post hole digger Figure 54 shows the main trench curving to the right with the generator feed trench joining from the left The 800 spool of aluminum cable was heavy so we cut down the plywood rims to fit our tractor s three point hitch then drove the tractor alongside the Figure 54 Feed cable trench trench to unroll the cable After the cable was laid we put a rear blade on the tractor to pull the dirt back into the trench Figure 55 Cable spool on tractor Cabling the PV array The four buried 2 aluminum feed cables to the house from the PV array exit the
139. olar panels and the family happily living off the grid Or perhaps you ve seen a suburban house with its roof covered in solar panels Surely this family enjoys low electrical bills and might even be making money by selling electricity to the utility Set aside the fancy slogans Such scenarios are possible but the cost is high and lifestyle changes might be required Solar technology hasn t yet reached the point where it is competitive with traditional fossil hydro nuclear power generation Here s the inside scoop on solar energy y P 8 P 8y On a sunny day approximately 1 000 watts 1 KW of solar energy strikes each square meter of the earth s surface when the sun is directly overhead In reality the sun is never directly overhead at locations north of the Tropic of Cancer or south of the Tropic of Capricorn so the solar energy will be less than 1 KW but let s stick with 1 KW for this discussion A typical solar panel measures about 38 by 76 20 square feet or 1 86 square meters Wow That single panel receives around 1 86 KW of solar energy at high noon if the panel is pointed directly at the sun Surely three or four of these would power a house Not so fast Solar panels don t convert all of that solar radiation to electricity not by a long shot PV panels in 2013 are only about 15 efficient This means only 279 watts of electrical energy is produced from those 1 860 watts of solar energy falling on the panel Pl
140. on about it producing energy from the sun does not use fossil fuel or emit greenhouse gases But let s be honest a small solar power system reduces these by only an extremely tiny amount This is an excellent case of put your money where your mouth is If you feel strongly that this small reduction is worth the cost of the system then you recognize the inherent green value of a solar power system Reason 6 Lower electric bills Any solar power system will lower your electric bill but a ibe nae uit ial We figured if we re going to spend the grid tied system will lower it more than a non grid tied money for the system why not recoup Deren some of it over time Together 4 and 6 A non grid tied system doesn t sell power to the utility savings average around a dollar per day lowers your electric bill whenever the sun is shining by reducing the amount of power you buy A non grid tied system produces only as much power as your house can use at that instant Even if it could produce more because the sun is shining brightly it won t because that excess energy has nowhere to Planning A Solar Power System Why Do You Want a Solar Power System Page 10 go Your system has capacity you can t always use A grid tied system always has a load the electric grid to take the power so that system always produces as much power as it can at the time Here is an example The PV Olga X Qy 5 LG arra
141. on the winter solstice In the northern hemisphere the noon sun climbs higher in lower latitudes than it does in higher latitudes How high does it climb at your location Let s find out Sun elevations at your location At solar noon on the equinoxes when the sun is directly over the equator it rises to an elevation equal to 90 minus your location s latitude So for Columbus latitude 40 north the sun rises to 90 40 50 Atlanta is at a lower latitude of 33 7 north so the noon sun climbs higher to 56 3 on those same dates Calculate the sun s noon elevation at your location on the equinoxes Subtract the latitude you found on page 49 from 90 and write it here or in your solar planning notebook o Sun s equinox noon elevation at your location The sun s equinox noon elevation is interesting and helps us understand its movement during the year but the really important elevations for planning purposes occur on the summer and winter solstices These tell us the highest and lowest noon sun elevations and we can then decide how much to tilt our PV panels At solar noon on the summer solstice the sun rises to its equinox noon elevation plus 23 4 the tilt of the earth s axis Example On approximately June 21 in Columbus the sun rises to 50 equinox elevation 23 4 tilt 73 4 At solar noon on the winter solstice the sun rises to its equinox noon elevation minus 23 4 Example On approximately De
142. ow from left to right the PV array sun symbol is producing 3 2 KW This 3 2 KW is going to the battery bank at a voltage of 52 6V which is feeding the inverter rectangle with symbol The inverter is producing 2 4 KW The power pole symbol at the far right indicates the grid is up at 248VAC Pressing buttons surrounding the panel brings up other information on the display Not shown in the photo is the lower half of the controller which contains controls to configure the system components The MATE contains a built in Web server and an Ethernet jack A computer connected to the MATE can open a page with a Web browser that shows current system status including PV production battery state inverter output voltage and power and several other items The MATE works only with Outback Power equipment Check with your vendor to learn about other manufacturers system controllers and download their data sheets System protection Safety and equipment protection are vital in any solar power system Battery protection 1 The section on Circuit breakers describes how a 175A circuit breaker in each battery string is both a safety feature and a convenience Once the cables from the battery bank reach the load center or other tie point for the inverter the entire bank must be protected as well Look carefully at the right side of the load center in Figure 37 The heavy red positive cable Why two circuit breakers from the battery b
143. ower probably is a very big deal it s likely you ve already trimmed your electricity usage to the bone so there s nothing left to cut If you re not going off grid perhaps less solar power is nothing more serious than a minor lifestyle adjustment Sorry family well have to cut back the air conditioning if the grid goes down Two hours of AC per day and that s it Planning A Solar Power System Site Survey Part 1 Page 47 CuoosineG Sorar Panets Part 1 You have already taken the first step in Site Survey Part 1 you have identified one or more candidate solar panels you know how many of them you need and you know they will fit in your available space We will choose the actual panels in Choosing Solar Panels Part 2 but now let s narrow the choice a bit A number of factors not all of them obvious come into play when choosing a solar panel Here are the major factors along with why they matter Panel wattage As we saw above the more energy you can get out of a single panel the fewer panels you need to achieve your target total array wattage Conversely smaller lower power panels might fit into a restricted site where larger panels won t Brand reputation It makes sense to buy panels with a good reputation Solar panels are a major investment and operate in extreme environmental conditions so cutting corners on quality to lower cost is not what we want a manufacturer to do Ask vendors for recommendat
144. oxes or raceways to serve a similar purpose Figure 37 shows a completely wired load center installed beneath an Outback Power Radian inverter From left to right are panel with circuit breakers and GFDI internal wiring dual 175A battery circuit breakers center right battery monitor adjacent to breakers with green yellow red label DC input bus bars to inverter upper right above 175A circuit breakers and gray flexible conduit with cabling Fi igure 37 Load center installed Denei inverter from batteries and charge controller lower right Terminal bus bars TBBs metal bars containing holes for cables and screws to secure the cables are mounted on the rear panel of the load center More details are visible in Figure 38 showing the right two thirds of an empty load center Planning A Solar Power System The Complete System Page 92 TBBs are held in plastic brackets on both ends The DC positive connection plate is where the battery positive cable connects as well as other cables from circuit breakers and the GFDI page 72 The inverter DC input bus bars bolt directly to terminals on the bottom of the inverter no cables are needed The shunt near the top is one of three ultimately Figure 38 Empty load center installed Shunts are used to measure high current flow They have a tiny internal resistance so when current flows a tiny voltage develops across the resistance Th
145. p three years later and two elbows were added in a trench from the ground mounted PV array and the generator The feed cables were pulled through and connected to the system without needing further construction work Planning A Solar Power System The Complete System Page 100 Example wiring diagram Figure 43 shows how how we wired our new house Solar Load Center Solar Panels for solar power The house has 400 amp electrical service entering through two 200A main breaker 240V Inverter Output to Solar Load Center boxes s Main Breaker Solar S Branches to Outback Power Radian 8KW In this diagram breaker boxes are labeled load dian SK centers which also is a common term Do not confuse these with the solar power system s load center Inverter discussed on page 92 is Installed Main M1 amp r grid only Batteries The main boxes are wired to high power and other rf Branch Circuit appliances designated for grid only use to Inverter Electrical Service from Grid A third breaker box is used solely for solar powered appliances 200A Main Load The solar power system wasn t even started when roe a 2 st 200A Main Load the house was wired so the electrician wired a cable Center 1 Figure 43 Example house wiring for a solar power system from a branch breaker in one of the main boxes to the d ai 8 i main breaker in the solar box This temporary c
146. power supplied by the batteries into 120 or 240 volts AC at 60Hz and to synchronize its frequency to the electric grid if the system is connected to the grid The batteries are wired to inverter s input through a high current circuit breaker and the inverter s output is wired to a breaker box in the house so it can supply power to designated household appliances If the system is grid tied and is approved to sell power to the utility the inverter performs that function as well To sell power the power must originate with a green energy source such as PV panels or a wind or water turbine In other words to be sold the energy must come through the charge controller and not be needed for charging the batteries or powering household loads System controller The system controller monitors and controls the charge controller and inverter and possibly other components as well It usually has buttons and a display to allow you to see the state of all system components and make configuration settings Load center A load center is a steel cabinet that houses terminal blocks and other connections circuit breakers and assorted other small components It is a central connection location for cables to the PV panels charge controller batteries and inverter A load center may not be available for all systems but wiring a system with one is much easier than wiring a system where the connections are made in multiple locations Gen
147. ppliances you intend to run from solar along with their power consumption Follow the instructions on the previous page Note This table is for solar power only Later you will make a grid power audit table which is explained on page 19 Do not include high power appliances like an electric stove Our choice HVAC We have a geothermal HVAC system that draws just over 3 KW We chose to include oven electric water heater or electric clothes drier These are likely to draw 5 000 or more watts apiece so each alone would exceed the capacity of many solar power systems Heavy du DM A pow y P y UPS it in the solar power audit reasoning that appliances such as these must remain wired to a grid breaker we can cut back the thermostat during a I fi l E high box and are excluded from solar power Enter high power AED E appliances in the grid power audit table Table 3 wood stove for emergency heat in winter Be as accurate as possible You don t want to be surprised after the system is designed and installed to learn that your family uses the microwave oven for two hours per day instead of the six minutes you estimated Planning A Solar Power System Getting Started Estimating Electrical Loads Page 18 Total Hours KW KW On per KWH per Appliance No Load Load Day Day Table 2 Solar power audit Grid
148. r Voc Voc is listed on vendor websites Re read the first sentence in this section The goal is to wire as many panels in series string without their temperature adjusted Voc exceeding the charge controller s input voltage The reduced power loss over the long haul is worth this one time effort Reducing the cable resistance Lower cable resistance means less power lost due to heat You can reduce cable resistance by increasing its diameter gauge or by using two parallel cables to halve the total resistance of that run This Wikipedia page contains a table that includes the resistance value for each gauge copper wire http en wikipedia org wiki American_wire_gauge Tables of AWG_wire_sizes Notice the 0 kFT column This is the number of ohms per thousand feet for that wire size Look again at the discussion on page 73 about calculating power loss from current and wire resistance It also shows how to calculate PV current from the array power and the Voc The wire table is where you find the resistance of the wire you plan to use Note this table is for copper wire only Aluminum wire has higher resistance for the same gauge so a different table is needed for it such as this one http www interfacebus com Aluminum Wire AWG Size html Let s try an example Planning A Solar Power System Choosing Solar Panels Part 2 Page 74 Example Assume you have determined that you can string two PV panels in series for a tempe
149. r or TBB inside the combiner box Refer to your measurements and juggle Figure 23 PV cable routing numbers until you come up with a good solution Keep in mind that one of the cables you get from the original extension cable connects to a PV s positive cable and the other connects to a PV s negative cable These can be any panels not necessarily the same one But one PV cable must be positive and the other must be negative Think in terms of Use this piece for panel 1 positive and use that piece for panel 7 negative Since extension cables are sold in specific lengths you ll need to find a use for what remains after using part of one Look carefully at your measurements to discover a length equal to or slightly less than the leftover cable length Be sure to account for the fact that the leftover piece will connect to a PV panel s opposite polarity cable than the first piece and choose the correct measurement Also remember that extension cables come in several lengths so if one solution doesn t work try a shorter or longer extension cable l he work is tedious but worthwhile to avoid wasting the extension cables This spreadsheet illustrates one way to work toward a solution Orig Length Used Length Remaining 50 1 50 CD Pos 50 2 50 EF Neg 50 3 50 EF Pos 30 1 30 CD Neg 30 2 30 AB Pos 15 1 15 NP Neg 15 2 15 Figure 24 PV cable use calculator
150. r power equipment is heavy PV panels weigh 50 to 60 pounds apiece A battery can weigh 50 to 140 pounds Our Radian inverter weighs 125 pounds without the 38 pound load center Much solar equipment is delivered by motor freight tractor trailer because it exceeds the weight limit of UPS or FedEx Consequently you need to plan where to put the equipment and how you will move it there from the truck Things to think about include Can a tractor trailer make it down your driveway Can it get out again If not the equipment will have to be unloaded on the street at the driveway entrance Freight companies normally expect an unloading dock at the destination You probably don t have one so you will need to request and pay for a truck with a lift gate on the rear to lower the shipment to the ground This is common so your vendor likely knows how to arrange for a lift gate and how much extra it will cost How will you move the heavy shipments from the unloading point to your storage or final location Most equipment comes in corrugated cartons that can t be left in the rain so prompt transfer is important Multiple items like batteries can be unpacked on the spot and moved individually But can you move a dozen or more 130 pound batteries Planning A Solar Power System Final Steps Page 109 PV panels might weigh 1 000 pounds on a pallet making them impossible to move without a pallet jack The PV panels in Figure
151. rator when the battery bank discharges below a set point Our generator uses a 3 wire starting circuit so we needed this electronic module to connect it to the Radian s 2 wire output http atkinsonelectronics com ma nufacturing product pdfs GSCM mini d pdf the solar power audit on page 18 and is fed by the solar inverter Only these appliances and receptacles and light fixtures will be powered by the inverter Other appliances remain wired to a grid breaker box and are powered solely by the utility grid An electrician can add a solar breaker box to an existing house or install one when a new house is built Existing house It has become common to install an additional breaker box in existing homes for solar power or emergency generators Your electrician should know about these Avoid generator transfer boxes These are breaker boxes that accept emergency power and feed it to branch circuits but they may also have relays that switch branch circuits or the entire box over to the emergency power source generator when it starts up While such a box might work for solar it s best to avoid having relays that are energized continuously day after day You need a regular non switched box because the inverter will be feeding it all of the time not a generator feeding it infrequently Planning A Solar Power System The Complete System Page 98 New house If you are building a new
152. rature adjusted Voc of 85V and your charge controller can accept this voltage Your 4 KW array will produce a full sun current of 4 000W 85V 47 amps Next assume the distance between your PV array and the charge controller is 135 feet and you plan to use 2 copper wire The total length of this 2 wire is 270 feet because you ll have wo runs one for the positive side and the other for the negative side Power is lost over the entire length of wire According to the Wikipedia table above 2 wire has a resistance of 0 1563 ohms per thousand feet so your total wire resistance is 0 1563 Q x 270 feet 1000 feet 0 0420 The power lost in 0 0420 with a current of 47A is 0 0420 x 47A 0 0420 x 2209 92 78watts 93 watts represents 2 3 of your PV array s maximum output power As a comparison and without duplicating the math with 4 wire you would lose 148W or 3 796 of the maximum PV power If you went with 0 wire the loss would be only 58 6W or 1 596 Finally stringing two runs of the 2 wire in parallel would halve the total resistance to 0 210 for a power loss of 46 4W or 1 2 half of the original 92 78 watts and 2 3 As you can see from this example larger wire dramatically reduces power loss This isn t obvious until you unknowingly start with a seriously undersize wire For instance with 8 wire would lose 9 4 of your solar power to heat from cable loss What loss is acceptable You decide If the loss is to
153. ray receives the most sunlight Shadows during this peak period can drastically cut your energy harvest If your array site is at ground level you might want to include a stake broad enough to cast an easily seen shadow When you take a photo at solar noon the length of the shadow will help you visualize true north and the sun s highest elevation on that date The longer the shadow the lower the sun Shadows from thin stakes can be hard to see in photos if they fall on grass or uneven terrain One way to make a broad stake is to use a wood 2x4 or 4x4 about 3 long and a 2 length of rebar Drill a hole about 4 deep into one end of the wood post Drive the rebar into the ground leaving 4 protruding then place the post over it Make the post as close to vertical as possible to get an accurate shadow 4 Take photos On a sunny day as close as possible to the designated date each month and at the appointed times 10 00 solar noon and 2 00 take your camera and notebook to the chosen location Set or fasten the camera in the same spot each time so it captures the same area Set the camera s zoom lens to the same setting every time Zoom out wide angle to capture as much of the site as possible Notice in Figure 15 how much extra space is included beyond the ends of the green rectangle Seeing how sunlight falls on this space might open possibilities for slightly shifting the site one way or the other or even expanding it If yo
154. rbed glass mat AGM Volts Enter the battery s nominal voltage such as 2V 4V 6V 12V or 24V AH Enter the battery s charge capacity in amp hours KWH Multiply the battery s voltage by its amp hour rating to get its charge capacity in KWH Price Enter the vendor s stated price Maybe you can catch a price break if you buy the entire system from one vendor but don t count on that now KWH Divide the price by the KWH to get the price per kilowatt hour This is helpful when comparing batteries of different voltages capacities and technologies e g flooded vs AGM Here is another table to fill in below Instructions follow the table Choose a candidate battery as a starting point you might come back and change it later Replicate this table in a computer spreadsheet or print it to preserve your data and make changes without rewriting everything from scratch Let s get started Planning A Solar Power System Choosing Batteries Page 35 No Description Value 1 Daily appliance load from solar power audit KWH day 2 Desired run time from batteries Days 3 Battery bank target capacity 1 x 2 KWH 4 Candidate inverter nominal input voltage VDC 5 Candidate battery part number 6 Candidate battery type 7 Candidate battery voltage VDC 8 Candidate battery stated amp hour capacity AH Candidate battery KWH stated capacity 9 Z7 VDC x 8 AH
155. reaction Often batteries use lead plates and sulfuric acid to create this reaction Battery bank is a set of batteries wired together to store energy and release it as needed Depth of discharge abbreviated DoD is the lowest a battery should be discharged to ensure long life Completely discharging a battery dramatically shortens its life A 50 DoD i e half of full charge is a reasonable design parameter One particular battery specifies a life expectancy of 1 800 charge discharge cycles at 50 DoD but only 425 cycles at 100 DoD quite a difference Some systems let you set a trigger in the system controller to shut off the inverter when battery charge falls below 50 Always assume that you have only half of the stated battery storage capacity Planning A Solar Power System Definitions and Formulas Page 5 Charge controller is an electronic device that adjusts the amount of power being sent to charge a batteries in the system Inverter is an electronic device that converts direct current DC from batteries to alternating current AC for use by household appliances System controller is an electronic device that orchestrates the operation of a solar power system s components such as a charge controller and an inverter Grid is short for power grid electrical grid or utility grid The nationwide interconnected cables that supply electrical power to homes and businesses Grid tied As used in th
156. rge controller is attached to the right side Inverters generate heat so good ventilation Figure 27 Inverter with system controller and charge controller is a must Convenient walk up access is a benefit when you need access to controls on the controllers This inverter in Figure 27 is mounted high enough so the displays on the controllers are at eye level This inverter is adjacent to the battery rack so the battery cables to it are less than 3 long We discuss batteries next because they are important large and heavy Then we ll cover the load center and other components Battery Bank Batteries store energy from the solar panels and feed it to the inverter when needed After Choosing Batteries you should have one or more candidate batteries in mind Talk with vendors one more time if you have any lingering questions because it s time to finalize some design criteria Item 5 Planning A Solar Power System The Complete System Page 84 in Table 6 on page 36 contains your candidate battery part number and 14 contains the number of batteries you will need Naturally you should update Table 6 if you choose a different battery Location The first decision to make is where to place the batteries They should be within 3 or 4 of the inverter to minimize power loss due to cable resistance If flooded cell batteries should be located in a closed room provide a way to periodically exhaust the hydrogen they emi
157. rgy to the charge controller The combiner box Inside a combiner box the PV strings positive cables connect together and their negative cables connect together In other words the combiner box is where strings are connected in parallel Larger cables exit the box to feed power to the charge controller inside the house Extension cables with MC4 connectors extend the PV panels short factory cables to the combiner box More on this below The combiner box should be centrally located near the PV array to keep cable lengths balanced but it is not a problem if this is impossible ia _ lt lt EE Figure 22 Combiner box internal components Inside the combiner box is a bracket that holds multiple circuit breakers The box in Figure 22 has space for 12 and has seven installed Positive cables from the PV panels connect directly to the breakers using the screws visible at the bottom The top screws on the breakers clamp to a metal bus bar which is where the positive cables are actually combined Two heavy cables with red tape carry the combined positive voltage to the charge controller Negative cables from the PV panels are clamped with screws in the silver colored terminal bus bars TBBs on the left and right in the photo As pictured these bus bars are not electrically connected so a short cable must connect them in the final installation Two heavy cables carry the combined negative voltage to the charge controll
158. ries 8 Enter the stated amp hour capacity of the battery 9 Multiply the battery voltage 7 and its stated amp hour capacity 8 to get the battery s KWH capacity Remember to divide by 1 000 for KWH Notice in Table 7 how a battery s amp hour capacity alone doesn t tell you very much You need to know the KWH capacity to compare batteries and to compare relative cost per unit of energy stored Also notice how technology affects the cost per KWH of storage capacity AGM batteries cost more per KWH than flooded cell batteries and the gel cell battery has the highest cost per KWH than either of the other technologies 10 The inverter s nominal voltage from 4 is the target voltage for your battery bank so enter it in 10 Planning A Solar Power System Choosing Batteries Page 37 11 Divide the battery bank voltage 10 by your candidate battery s voltage 7 to get the number of batteries in one string Examples If the inverter s voltage is 48V and you chose a 12V battery you will need 4 batteries in a string If you chose 6V batteries for the same inverter you ll need 8 batteries in a string 12 To calculate now many KWH one battery string can supply in actual use multiply the candidate battery s KWH capacity 9 by the number of batteries in a string 11 then divide by 2 Enter this in 12 The reason for dividing by 2 is to design in the 50 depth of discharge explained in the sidebar on page 31 13 Now we want
159. roller data sheet for absolute limits or recommended maximum wattage statements The maximum power that the charge controller can pass depends on battery bank voltage For example the charge controller in Figure 36 can supply up to 5 KW to a 48VDC system but only 2 5 KW to a 24VDC system Modern charge controllers are of the Maximum Power Point Tracking or MPPT type which seeks out the maximum power available from a PV array and uses it to recharge the batteries This is important since PV output varies as the sun moves across the sky each day and by season Choosing a charge controller When choosing a charge controller look carefully at price A 3 2 KW model of the 5 KW charge controller in Figure 36 36 less capacity is available but at a price only 796 lower Choosing the 5 KW model is a no brainer The charge controller should be designed to work with your system controller and should be compatible with your battery bank s voltage Recommendation choose a charge controller with the highest power limit or recommended maximum wattage you feel comfortable buying Planning A Solar Power System The Complete System Page 91 Load center A load center is a metal cabinet that contains circuit breakers and terminals to connect other system components such as the inverter PV array charge controller batteries grid power and generator Not all systems have a load center Some use bolt on electrical b
160. rs all six strings of solar cells so 4 is not producing power However 3 is unshaded and it can produce full power Panels 4 3 are wired in series as are 14 13 so one would the shaded panels to prevent current from flowing in each pair from However this is not the case bypass diodes allow the unshaded panels current to bypass the shaded panels and contribute to the array s production The entire array in Figure 17 is producing 1 8 KW 72 of its 2 5 KW potential for this date and time This is a testament to bypass diodes because only six of the 14 panels 43 are in unobstructed pairs Without the diodes only those six panels would be producing power Winter In winter with no leaves on the trees trunk and limb shadows can cut diagonally across panels Figure 18 shows this on a sunny mid afternoon in late November Figure 18 Winter shadows on PV panels Planning A Solar Power System Site Survey Part 2 Page 67 Even though panels 4 3 have at least 95 of their surface illuminated the diagonal shadow slicing across all of the series wired cell strings inside completely disables both panels A large shadow crosses panels 7 and 6 and other shadows fall on the other panels in 8 7 and 6 5 so those pairs are likely not producing power Only pairs 2 1 on the front row and 14 13 on the rear row are unobstructed and producing their maximum for this sun position 12 is producing po
161. s You probably are familiar with ground fault circuit interrupter GFCI receptacles in your bathroom or kitchen A GFCI instantly breaks the circuit to the appliance plugged into it when a fault is detected preventing shock or electrocution to anyone touching a metal fixture when the appliance defect occurs A ground fault detector and interrupter GFDI performs the same function but for the DC solar panels instead of 120VAC house current If current were to flow from a solar panel to ground the panel could overheat and cause a fire especially dangerous if the panels are installed on a roof Read more about GFDIs here http solarprofessional com articles operations maintenance pv system ground faults Ask your vendor for a GFDI that meets code and works with other system components you have chosen How far away will the panels be The distance from the solar array to the battery bank is a consideration but often there is only a little you can do about it The main factor is this The closer the panels are to the batteries the less power will be lost due to cable resistance You can do two things to minimize this loss 1 Raise the PV array s output voltage 2 Reducing cable resistance Let s look st these individually Raising PV output voltage This is a bit technical but necessary Briefly higher voltage improves power transmission efficiency You might be able to wire two or more PV panels in series to increase
162. s a complete system yours ultimately could look something like this Solar panels are outdoors but everything else is inside and you need to figure out where it will live and how to wire it together Choosing and installing this equipment requires considerable planning not to mention cost This section describes the equipment you should ask about when talking to vendors and how to plan for it as you design your system Figure 26 shows the components in our system They are Inverter Large rectangular silver eis E n cabinet in the center of the photo The j RS E Figure 26 A complete narrow gray grille marks the bottom of the inverter cabinet Load center Smaller rectangular silver cabinet attached to the inverter below the narrow gray grille System controller Small beige box attached to the left side of the inverter Charge controller Narrow black box attached to the right side of the inverter Gray flexible conduit runs from it to the right side of the load center Batteries Twelve 12V AGM batteries sit on a heavy duty steel shelf unit capable of supporting 800 pounds per shelf The top three shelves are used for general storage Yes the wire shelves do sag a bit under the weight of 524 pounds of batteries capable of supporting doesn t mean they won t sag Communications hub Thin black box attached to the left side of the load center Ethernet like cables from the inverter system controller
163. s 2 volts Thus a battery s voltage is a multiple of 2V such as 6V 12V or 24V You can buy single cell batteries that produce 2V Technically it isn t a battery unless it has more than one cell Batteries may be wired in series to produce higher voltages and in parallel to provide greater energy storage capacity Series wired batteries are called strings A group of batteries wired in series and or parallel is called a bank Batteries wired together in a bank must be identical to allow equal charging and discharging Never mix batteries even with similar specifications unless they are from the same manufacturer and have the same model number But wait A battery should not be completely discharged and then recharged especially on a regular basis Doing so drastically shortens the battery s life Read about depth of discharge or DoD on page 5 As a rule of thumb expect to get only half of a battery s stated amp hour capacity So in this example that 200 AH battery actually can deliver only 100 AH or 1 2 KWH 12V x 100 AH Planning A Solar Power System Choosing Batteries Page 31 Multiple batteries increase capacity One battery that can deliver only 1 2 KWH is useful only in a very small system 1 2 KWH will run a desktop computer and two 13W CFL lamps about 200W total for just six hours What if you need more Batteries may be wired in series positive terminal of one to the negati
164. s Choose several candidates based power output The higher the target panel power the fewer panels you will need Start with panels in the range of 200 to 300 watts Enter each candidate panel s information in Table 8 3 Number of PV panels needed For each candidate panel divide the wattage in the Target PV KW column by the panel s wattage and enter the result into the No needed column Since the target PV KW in stated in kilowatts remember to divide the PV panel watts by 1 000 to convert to KW so both values have the same units 4 Total array power Multiply each panel s power in KW by the number of panels to get the array s total power in KW for that panel Enter this into the Total KW column Repeat steps 1 4 for as many PV panels as you wish to consider Planning A Solar Power System Site Survey Part 1 Page 44 Target Size No Total PV KW PV model and vendor W x H Watts Needed KW Table 8 Candidate PV panels for site survey That s it Now you have identified at least one candidate PV panel and you know how many are needed to produce the power listed in the Target PV KW column Will the panels fit my space Next question Will the PV panels will fit the available space PV panels come in various dimensions depending primarily on wattage but also varying by the type size and number of individual cells used in the panel For planning purposes it helps to t
165. s 1 the factor by which we multiply the sun s energy to find the energy falling on the PV panels That is if the sun is directly in front of the PV panels they will receive 100 of the energy falling on them But the sun will be directly in front of the panels only if they are tilted backward at the same angle as the sun s elevation The paragraph above states that the sun s elevation is 68 If the panels also are tilted 68 the sun is directly in front of them The difference between sun elevation and panel tilt is 0 which has a cosine of 1 so the panels get 100 of the sun s energy But what if the panels are tilted only 40 Now they aren t looking directly at the sun they are facing 28 lower than the sun 68 sun elevation 40 tilt 28 The cosine of 28 is 0 883 Tilted 40 the panels receive 88 396 of the sun s energy at solar noon Notice that we take the cosine of the angular difference between the sun s elevation and the panel s tilt or angular difference between the sun s azimuth and the panel s azimuth That is we take the cosine of the difference between the angles Then we multiply the azimuth and elevation cosines together to get the true insolation factor Here is a similar example that changes the azimuth and elevation An hour later the sun has moved to azimuth 215 and elevation 64 Now the relative angle between the sun s azimuth and the solar panels is 215 180 35 The cosine of
166. s voltage resistance and current It has three forms m E IxR says that the voltage E across the two wires of a circuit is the product of current I flowing through the circuit multiplied by resistance R of the circuit Example If a current of 3A flows through a circuit having a resistance of 25Q the voltage applied to the circuit is 3V x 250 75V m I E R says that the current I flowing through a circuit is found by dividing the voltage E applied to the circuit by the resistance R of the circuit Example If from above a voltage of 75V is applied to a circuit having a resistance of 25Q then a current of 3A will flow 75 25 3 m R E Isays that the resistance of a circuit is found by dividing the voltage E applied to the circuit by the current I flowing through the circuit Example If current of 3A flows through a circuit when a voltage of 75V is applied then the circuit has a resistance R of 25Q 75 3 25 The power formula m P ExlIsays that power in watts is calculated by multiplying the voltage applied to a circuit by the current flowing through that circuit There are variations of this formula that involve circuit resistance but we won t muddle things with those at this point Example When a typical hair dryer is operated from a 120 volt household receptacle a current of 12 5 amperes flows Doing the math 120V x 12 10A 1 500W The hair dryer consumes 1 5 KW of power to produce heat Planning A S
167. scharge So if your solar power audit shows your appliances consume 7 KWH per day and you have the 14 4 KWH battery bank described in the previous section you can expect to operate those appliances from batteries for two days Maybe the sun will come out soon Or perhaps you can alter your living habits during the power outage Turn off lights during the day Cut back on TV Reduce water well pump usage If you can cut your daily power usage by 2 KWH to 5 KWH the batteries will power the house for nearly three days 14 4 KWH 5 KWH 2 9 days Or maybe you need more batteries Identifying candidate batteries Use this table to identify candidate batteries for your system At this point you should have read the sidebar Battery characteristics on page 30 and now you need to identify several candidate batteries Call vendors and ask for information and advice Ask about the pros and cons of the batteries sold by each vendor List candidates in Table 5 below Planning A Solar Power System Choosing Batteries Page 34 Brand amp No Vendor Type Volts AH KWH Price KWH Table 5 Candidate batteries For each candidate enter the brand and part number plus the name of the vendor where you found the information List technical information about the battery n its price Candidate battery calculations Type Typical types are flooded gel and abso
168. ses in July This information is helpful when deciding on how much to tilt your solar panels and when evaluating the shadows that might show up in your site survey Visualizing with a sun chart Wouldn t it be great if there were a way to graph the sun s position in the sky hour by hour and day by day over a year There is Several websites offer online programs to do this Figure 14 shows a nice one from the University of Oregon Solar Radiation Monitoring Laboratory http solardat uoregon edu SunChartProgram html image used with permission Just enter your ZIP code and the program finds your location and creates your chart There are seven steps labeled in blue on the website In Step 1 select the option to look up your location with a ZIP code and enter yours in the field Specify your time zone in Step 2 Steps 3 and 4 can keep their default selections or change them if you wish In Step 4 select Crop azimuth axis to fit plotted data and Crop elevation axis to fit plotted data to minimize unused space on the axes Select whether you want a PDF file or a PNG image in Step 6 then create the chart in Step 7 Planning A Solar Power System Site Survey Part 2 Page 56 12 P fe DPI BTE ETA of Oregon SRML wa Sp Lat 39 96 Long 82 96 Solar time zone 5 le Solar Elevation FSSC CELL LLLI LLLA LE 4E TE T sb 4 2f LL LL Ld al lla p 1 VN N AFAT NLA NB SN A NY Y Yu b
169. sessssessssesserssssesneossssessessens 96 Irc 96 DUIS POO CO d nne Ne oth alt iR EH aao EE 97 B ttery protetti met 97 Why TWo CHOHK Breakers Z diis uiv dui Wevevv PH RHAPDHTMAQU UH EM EAM PEPPEEREMEPVO nanan 97 AC input protection 2 iioii eerie rentre canna c repa ia aus cu arie ele ie eid ip ors anhckkn anne swim Sir Ran D DN RR RAS iocis 97 Our choice mci 98 AC OUtPUtProteCtiO MM P 98 ALI 0 98 to po Ae M 98 d icio See C M 99 Ur choice diesel generato usine irert ts EEEPEEUEEEYOXEYLEMEREEA RR pAPUE FRA NRREMELEKFUEMEI EEERDU KIT PRETI FUR 99 Generator output capacity 11e aaaea res rye Ero EO es pea Eee a 99 Wiring to the SyStOITI a ier e rtu a kae eL eh aen aoa in even eE c dE vae re a vw cea PE EE ET XR 100 Wammel ari M 100 Manual or automatic Stt recorre edipi toit Eo Ero B For ertet redana Eea aria osariike irisa 100 Ec oo Ri A 101 Connecting the system to house wiring 1 ee eeee cree ee en eere n nenne nnne nana nuaans 102 Me DASICS e M N 102 Warning Danger Cac
170. sing a solar power system as a whole home UPS page 9 is that you might not know when the grid has gone down It is good to know this during a storm so you 4 can begin conserving battery power What you need is an easily seen grid monitor Figure 50 shows two night lights plugged into an easily seen grid only outlet example only one light is sufficient A quick glance shows if the grid is up or down If your night light uses a photocell to turn it on only at night paint or tape over the photocell so the light shines all the time Set up network access Some system controllers have an Ethernet port for connection to a home network and Figure 50 Grid monitors serve HTML pages that you can view on your computer with a Web browser Such a feature can be very convenient for checking the current status especially if your system is tucked away in a corner of the basement and you don t feel like hiking all the way down there at the moment Planning A Solar Power System Finishing Touches Page 112 Many homes aren t wired for Ethernet but it is easy to set up a router with a wireless Wi Fi network With Wi Fi you can use a desktop computer a laptop a tablet or even a smart phone to view your system s status You might already have such a router to distribute cable DSL or wireless broadband Internet service to home computers If the router is within 300 of your system you can plug a regular Cat 5 Ethernet ca
171. single string before hitting the charge controller s maximum input voltage is far fewer than you need for your array How do you wire the entire array Just like batteries PV panels can be connected in parallel to increase the current fed to the charge controller Connecting two panels or strings in parallel doubles the current and consequently the power Three strings triples it four strings quadruples it and so on Most likely your PV array will have multiple strings of two or more series wired panels Planning A Solar Power System Choosing Solar Panels Part 2 Page 76 Panel interconnections PV panels come with short 3 or 4 positive and negative cables permanently attached to a junction box that is wired to the internal solar cells Each cable has a polarized industry standard MC4 or compatible connector MC4 connectors are used throughout the solar industry to interconnect PV panels They are polarized male and female so it is possible to connect a positive cable only to a negative cable for series wiring or to a panel mounted positive connector of the opposite gender e g on a combiner box MC4 connectors are weatherproof and have latches to ensure a positive connection that won t pull loose But be alert Some PV panels come with cables having H4 connectors that mate with MC4 connectors but have a slightly different latching mechanism This might make it tricky to latch an H4 connector to an MC4
172. stem Works Househoid BISON CITY sosia e a 12 iistotical N11 30 gt aae Cert pe ben UNE reer ree eee 12 Appliance power CONS UID UGH isiancecaiccsdecssiessicascsaieiataciescseanaiascieessdesstanseuarnienstamieieiansiaaminseese 12 Solar AG sirrane M MES MIS OMNEA MUN DMM M MM AUAM 13 Dome DUX as a DEDE LM LLLI E DE 13 lip m 13 Charee Conto Me AMNEM rer RTT 14 Dil dl PR 14 System UM La Ended ed ura iu dI a N 14 SU CODE oa bc pu uA UTRUM SEDI KUNDE RARE CUR E UE ai arenes ICRI ERAI 14 Des DE acoso DD ERR HR DU EEL UTER E pA QUO ci P OX PUDE DATUM DATE FU CR SUE LR FM Sri EP M RB ID E 14 House CUCU Moto Ae nate 15 Getting Started Estimating Electrical Loads WANS TO i eo I IL PNE 16 i i 514 cp m 17 Solar Dower avdk TOI s vindi ppc aditibub tn qai Re RE ER MONEDA EUH LEM ELA SIM DOMUM 18 Our choice AVAG asn Lt ra o EDEE E Co Ce Le Dc Eos E Eoi CEP Fa eir Da PE LEVE RS E00 18 Ceci d oro reme E NER 19 Our choice heating ADO c cm 19 Finding power consumption from appliance nameplates eee 20 Measuring power consumption VyOUlSelf ntanuerecri nari rapkemenss as tr pb nds esa as Sarum is an ex nenna 22 Total solar power TOGUI ari ses cicin cess ices sersvacasieis I Qao FUsb IRE IU IX P FORD GRE OH DIV IM FU a pP 0 M M DI IM LC tIRE
173. string s negative terminal run to a negative tie point on the left side This bank can supply 14 4 KWH of power before it is discharged to 5096 Planning A Solar Power System Choosing Batteries Page 33 Since AGM batteries don t have to be refilled with water no access to the top is needed These maintenance free batteries rest on heavy duty adjustable steel wire shelves purchased online from Global Industrial http www globalindustrial com p storage wire shelving chrome 74 h nexel chrome wire shelving 24 w x 24 d Each shelf can hold up to 800 pounds This is important since each of the 12 AGM batteries weighs 131 pounds so four together on a shelf weigh 524 pounds The entire battery bank weighs 3 4 of a ton How much battery power do you need Here s where we stand From the solar power audit you know how Figure 8 A bank of 12 AGM batteries much power your solar appliances require and you have chosen a candidate inverter that can supply that power with a comfortable margin above that Also from the solar power audit you know how many KWH of power is consumed per day by your solar appliances It s time to answer the next question How long do you want to run those appliances from batteries Suppose the electrical grid is down and the weather is cloudy Your inverter is running solely on batteries and the batteries are not being recharged by either the sun or the grid Eventually they will di
174. t while charging Some systems have the ability to automatically turn on a small fan while charging the batteries This fan should blow outside AGM and gel cell batteries do not emit hydrogen so they don t need a vent fan Batteries are very heavy so your support should be capable of holding them You can place batteries on the floor as shown in Figure 7 on sturdy homemade shelves made from dimensional lumber or 34 plywood on heavy duty wire shelves such as the unit in Figure 8 and purchased purchased from Global Industrial http www globalindustrial com p storage wire shelving chrome 74 h nexel chrome wire shelving 24 w x 24 d Another albeit costly choice is a commercial cabinet designed expressly for your batteries such as this one from Outback Power http www altestore com store Deep Cycle Batteries Enclosures for Deep Cycle Batteries Rack Type Battery Enclosures Outback Power 3 Shelf Integrated Battery Rack for 48V Systems p9859 Battery bank configuration The DC input voltage of inverter you chose in Choosing an Inverter dictates the voltage your battery bank must supply If the inverter needs 24VDC you ll need one or more strings of 12 2V batteries four 6V batteries or two 12V batteries to get it If the inverter needs 48VDC double the number of batteries in a string You determined the number of batteries in a string in Table 6 11 and the number of strings in 13 so now all that remains is to learn how to
175. terly declination The dial is rotated so its 10 mark aligns with the direction of travel If the declination were easterly the dial would be rotated so the 350 mark aligns with the direction of travel When the compass needle aligns with the arrow printed inside the h TIT n TITRE Ta qni MM Figure 12 Compass showing westerly declination dial the direction of travel arrow points to true north This Boy Scout compass is 60 years old and still works fine Use stakes and a shadow If you don t want to find your magnetic declination and use a compass to find true north you can find it with two stakes and a string on a sunny day Here s how 1 Gather a hammer and some string or surveyor s plastic marking tape and two stakes Home improvement stores sell steel reinforcing bar rebar for X A uat Figure 13 Using stakes to find true north Planning A Solar Power System Site Survey Part 2 Page 50 concrete Two 4 lengths make good stakes for this procedure and 2 lengths are handy for staking out a ground level PV installation 2 Go outdoors to a clear area a few minutes before solar noon page 5 on a sunny day Remember that solar noon is approximately 1 00 PM on the clock if Daylight Saving Time is in effect or approximately 12 00 noon if DST is not in effect We say approximately because solar noon occurs at different times becoming later east
176. tery strings are equal length and the three cables running to the tie block in Figure 32 also are equal length The clear Lexan shield covering the assembly is barely visible in Figure 35 Circuit breakers Planning A Solar Power System The Complete System Page 90 Charge controller The charge controller regulates battery charging from solar energy received from the PV array The DC output from the PV array connects to the charge controller s input and its output connects to the battery Minor note We applied white stickers like those seen bank Al solar energy flows through the charge controller whether it is used to in Figure 36 and Figure 26 to all charge batteries or is sent to the inverter components in our system to inform 8 run appliances or sell to the utility family members and visitors yes you will T As explained in The charge controller have curious visitors of each component s P 8 i ri A factor if your PV array can produce more power than the charge controller is able to pass this excess capacity is not used But this peak potential exists during only a few Charge Controller Beate hours on only a few days per year when the sun is closely aligned with your PV panels Most of the time the PV array can t produce peak power so it would be good if the Figure 36 Charge charge controller will accept whatever power it can produce Look in the charge controller cont
177. the solar power audit table Total Hours KW KW On per KWH per Appliance No Load Load Day Day Table 3 Grid power audit Finding power consumption from appliance nameplates You can find out how much power an appliance consumes by looking at its nameplate Major appliances and even small appliances like toasters and food processors have a nameplate somewhere check the rear or bottom that states the model number serial number line voltage e g 120 VAC and power consumption usually stated in watts Planning A Solar Power System Getting Started Estimating Electrical Loads Page 20 Appliances like cordless telephones radios or small computers might have power adapters bricks or wall warts that plug into an outlet The nameplate is most likely on the adapter such as this one Figure 2 Power adapter wattage on nameplate Appliances with plastic cases often have their nameplates molded into the plastic These can be difficult to see as on this hair dryer handle Look closely under good light and position the appliance to reflect the light off the molded nameplate Sometimes it s simple Incandescent light bulbs are rated Figure 3 Wattage molded into molded plastic nameplate by wattage so a 60W incandescent bulb draws 60 watts Compact fluorescent lamps CFLs have their actual wattage printed on t
178. the total voltage Explanation When current flows through wire the wire s resistance turns some of the current flow into heat watts These watts are lost and the lost power reduces the power available to run appliances Planning A Solar Power System Choosing Solar Panels Part 2 Page 72 Here is what happens Recall the power formula P Ex I on page 7 A variation of this formula to find current from power and voltage is I P E or current equals the power divided by the voltage If the a load e g an inverter is using 4000 watts from 24V solar panels then I 4 000W 24V 167 amps Calculate your PV array s maximum current using the I P E formula and write it here PV array maximum current amps Another variation of the power formula P Rx I calculates power from current and resistance and this is the one we use to find power loss in cable Assume the resistance of the cable between the PV panels and the load is 0 0050 The power lost as heat in the cable is 0 0050 x 167A 0 0050 x 27 889 139 45 watts Nearly 3 5 of the 4 000 watts of solar energy is lost to heat in the cable What happens if you double the PV voltage from 24V to 48V Now the inverter draws half as much current for the same power I 4 000W 48V 83 3 amps The calculation of power lost as cable heat becomes 0 0050 x 83 3A 0 0050 x 6 939 34 69 watts This is only 0 87 of the 4 000 watts of solar energy being sent to the invert
179. the user manual are on that page How well does it work Well Okay to a point The sun angle calculator is accurate and helpful but the power calculator is not very useful with trees on the horizon As explained on page 66 tree shadows cutting across panels drastically cut production But as shown in the photo on page 115 even shaded panels produce some power Furthermore the program calculates for one spot on the ground relative to the horizon but the panel array is 21 wide so the program cannot possibly predict power production for the entire array SAC was helpful for sun angles but not so much for power production Here is a screen shot Angle Cak wisior Horizon Min Ar Heizen Max Az 3 Graph Hosen loaded foc Final PV Location No c PV Pareis OES wans pec Pacet 298 gt Month and Day te Graph qnore yeas Aug v Calculate for hours betamen aB ag PM D Seve Resuts to File 12 day PY KWH e o Show Rents D Resuts in CSV 138 65 Sun on lt lt AUG 27 gt gt with horizon Final PV Location PV azimuth 180 PV tilt 42 Tam Azimuth 92 Elevation 18 PV power potential 0 12KW PV power actual 0 00 KW Sam Azimuth 102 Elevation 29 PV powerpotential O 82KW PV power actual 0 00 KW 9am Azimuth 114 Elevation 40 PV power potential 1 64KW PV power actual 0 00 KW 10am Azimuth 130 Elevation 50 PV power potentiale 2 56KW PV power actual 2 56 KW fiam Azimuth 151 Elevation
180. to know how many strings of batteries should be in the battery bank 3 shows the target battery bank KWH capacity and 12 has has the available KWH per string Divide 3 by 12 and round to the nearest whole number to get the number of strings Example Suppose 3 says we d like 25 KWH capacity and 12 tells us that a string can provide 4 8HWH 25 KWH 4 8 KWH 5 2 strings round down to 5 strings That doesn t sound too bad 5 strings of 4 batteries equals 20 batteries But wait There might be a limit on how many battery strings you may have Read the yellow sidebar below then call the battery manufacturer or vendor and ask how many strings are permitted If the answer is fewer than the number you calculated above enter the smaller number in 13 and make a note saying limit so you ll remember why it s smaller How many battery strings Battery manufacturers say to restrict the number of strings to ensure equal charging and discharging through the whole battery bank Minor differences in cable length or connection resistance can result in unequal battery charging and discharging Standard industry practice seems to be no more than three strings If you need more batteries than can fit into three strings read Hitting the target storage capacity below 14 Now we must calculate the number of candidate batteries in your battery bank Multiply the number of batteries in a string 11 by the number of strings you entere
181. to or slightly less than your inverter s output i e if you have a 6 KW inverter choose a 4 KW to 6 KW generator Planning A Solar Power System The Complete System Page 96 A 240VAC generator can directly power household appliances see below Some generators produce low voltage DC instead of 240VAC but these are highly specialized and require extensive research to determine how one can be used with a traditional solar power system as is the focus of this document Wiring to the system There are two ways to connect a generator to a solar power system 1 Wire it to the inverter Check your inverter s data sheet or installation manual to determine if it can accept a direct connection to a 240VAC or 120VAC generator If so learn how the system operates when the generator is running Ideally the inverter will automatically switch to the generator s power without any interaction from you If not perhaps there is a switch or circuit breaker to throw to use the generator 2 Wire it directly to the house If it is impossible to wire a generator to the inverter your only option might be to bypass the solar power system entirely and wire it to the household solar breaker box so it instead of the inverter powers appliances Ask your electrician to do this wiring see also Warning Danger Connecting a generator in this way Connecting the system to house wiring below before calling the electrician Essentially if
182. to your advantage Tell the installer your reasons for your choices and ask for his opinions or recommendations for alternatives and ask why those alternatives are better Ask about cost too and compare it to your equipment s cost Remember one thing You made your choices based on non trivial measurements calculations and research If the installer suggests alternatives go back and run the numbers again for the new candidates You should feel confident that any different equipment does indeed provide benefits without compromising some other part of the system For example if you need 12 PV panels but the installer recommends 18 with less power will they fit in the allotted space Will they be shaded to the extent that they will never produce full power How will they be wired Is the total Voc acceptable What about cable sizes As you can see a seemingly minor change can have far reaching implications Know what you re getting Planning A Solar Power System Final Steps Page 106 An installer should be responsible for obtaining all necessary permits and passing all inspections You shouldn t have to do any of this Once the project is complete the installer should show you how to configure and operate the system not just hand you a stack of owner manuals Finally ask if the installer is willing to let you hang around during the project Explain that you are interested in the details and would like to take photos but
183. trench in conduit behind the south row of panels The conduit runs directly to the combiner box The 10 cables from the pairs of panels in the south row run along the top support to the combiner box here they loop down and through bushings in the bottom Figure 56 shows the main feeder conduit and the looping panel cables Figure 56 South panel cables to combiner box Planning A Solar Power System The Dodd Kurylo Solar Power System Page 116 The 10 cables from the north panels run along the bottom support because it is closer to the trench to the front row through a service head on buried conduit to the south row then up and out through a service head and into the combiner box through bottom bushings Figure 57 shows the conduit for the main feeder cables running to the combiner box and the row to row conduit with its service head This photo was taken before the panel cables shown in Figure 56 were installed The small conduit visible in both photos behind the combiner box is a physical shield to prevent damage to the grounding wire from the panels to the ground rod Solar panel supports We learned that building our own wooden PV supports costs Figure 57 South row conduit much less than buying commercial metal frames We bolted 2x4 rails to 4x4 posts whose tops had been cut to a 42 angle There were two sets of these in each row of panels The posts were set in 8 holes bored 18 24 deep depending
184. trocution during selling solar power He measured repairs the meter terminals to verify no Outside safety disconnect voltage was present Once verified Another requirement might be he signed a form and we were good to go that you install an outside device to disconnect the inverter from the house wiring when a switch is turned off or a disconnect block is pulled from its socket This is to protect firefighters or others who might expect house power to be off after the meter is pulled This would not be the case if the system were Figure 44 Solar disconnect producing AC from solar power or batteries The disconnect ensures that house power is off Planning A Solar Power System The Complete System Page 102 A clearly labeled weatherproof box Figure 44 is mounted outside the house near the electric meter and houses the switch inset or disconnect block Boxes like this are sold by home improvement stores and electricians can supply them The fade resistant red labels in Figure 44 and many other kinds of warning stickers are sold by solar power vendors One note Inverters sell power by sending it out over the grid input cable so the safety disconnect must be wired between the inverter and the grid to inverter breaker in the solar breaker box This means that when the disconnect is switched off not only is the inverter s output removed from the grid it also is removed from all solar powere
185. ts and thie GEDI 5 itin si esae asi ien cesa ot rad ves Friedr epos eire tru AA FEE ope ER 73 How far away Will the panels DET issiiseasssiaisisessiasssrinenssieessiansissriesrienstamiisriesiierrenine eens 73 Raising PV output VOUS cis aem VER PLU PIU PERI MM IS aNu EIEC eNEAN Ease raK AY EN ERR UUNK 73 Solar panel open circuit voltage VOC cccssscssseeessceeeeseeeesseeeeseeeeeseeeeesseseeseeeeessaseessaeeessaeaseeeess 74 What does all this GAIN i wesc seo os sees esate ense a eade ce eset noe ei reU Due 2d a eens ie ce nba deua Eee evel el 74 Keduecing the cable fesiSt aliBB uss eise ui Rr RU TREES II aa eaan ar arida apoE enn 75 aR A 76 More poWet lOSSGB9 1 0 eves ccecs ones phos i50 HE 123222 inis Le s tiasscevecececnssatcercesteeceentescattecscec ove atch oheviee 77 How will the panels be Wire oviccccsieissssssinscissasininscsansesstosensssssnicissiasssavestatzeaiensdaniosssssesansnaewianie 77 Panel interconnectlolls coercet sies Seek bec shaves m rade ea Ceo ra vba ce cu eruca aeaa a ENEE 77 Wining It Rl RR ene aa esih 79 THE COMMING MDOX sch tee Ett 80 PV extension Cables citet oco pesci ea qus cers Sacce aai aadar ianaeaieo aiian Esaiae 81 itla deci T 81 Lupo cM 81 Planning to cut the PV extension cables 1 11 eerte cete ree eterni nnne nnam nonris 82 How will the
186. upports rear row s lowest point to the front row s highest point You protractor or you can quickly calculate the needed spacing To calculate divide the difference in row heights by the tangent of the sun s elevation at solar noon on the winter solstice Example Suppose the front row highest point is 9 and the rear row s lowest point is 3 for a height difference of 6 Assume too that the sun s winter solstice noon elevation is 27 The tangent calculator TAN function of 27 is 0 510 6 0 510 11 77 The rows must be spaced at least 11 77 apart But it s a bit more involved than just this isn t it always The sun is lower at hours before and after solar noon so the front row will cast shadows on the rear row then Rather than pulling the sun s azimuth into the calculation just use its elevation at those hours and assume it is due south This is not entirely accurate but good enough to avoid shadows Planning A Solar Power System Choosing Solar Panels Part 2 Page 70 Let s extend the example above Assume the sun s elevation at 10 00 and 2 00 on the winter solstice is 21 The tangent of 21 is 0 384 so now the calculation becomes 6 0 384 15 63 To avoid shading the rear panels between 10 00 and 2 00 on the winter solstice the rows must be 15 63 apart You can obtain the sun s elevation on specific dates and times from your sun chart page 56 or from NOAA s online calculator http www esrl no
187. ur camera has adjustable exposure compensation setting it to 1 or 2 EV will darken shadows and make them easier to see in the photo Snap the picture close to the appropriate time It doesn t matter much if you miss the exact time or even the date You re just trying to learn how well your site sees the sun and that won t change in a few minutes or a couple of days Take more than one photo each time to play it safe You can choose the best one and discard the rest It s handy if your camera has a feature that imprints the date and time on the picture If yours has this turn it on and set the camera s clock correctly Planning A Solar Power System Site Survey Part 2 Page 65 Tip If your camera does not have a date stamp feature write the date and time on a slip of paper and take a photo of that before you snap the site photo Do this every time so you know when every site photo was taken This will save you untold grief when you save your photos to the computer You need only one note for each day s photos just scratch out the old time and write the new time Once you have positively identified the date and time of each site image save those images with the date and sun time in the file name If you have Figure 16 Date and time note multiple photos shot at the same time add 1 2 etc to the file name Example PV site 2012 Mar 05 1330 sun 2 jpg Put the year month day near the beginning of the file name so
188. ure 6 On the left side a heavy copper bar is bolted to the negative terminals of the three strings A heavy Figure T A bank of 12 fiooded cell batteries black cable runs from this bus bar to a tie point ultimately connecting to the inverter On the right three red cables run to circuit breakers on the wall and from there to a positive tie point for the inverter Connecting the negative terminals together and the positive terminals together is the parallel wiring that turns the three strings into a battery bank Notice the white plastic sheeting under and surrounding the batteries Since these are flooded cell batteries their electrolyte periodically must be replenished with distilled water The plastic prevents spilled water or possibly sulfuric acid from damaging the floor or plywood walls Water is added to the batteries through top holes uncovered by removing the white caps There are three caps per 6V battery one per 2V cell If these were 12V batteries there would be six filler holes and caps Figure 8 is another example of a battery bank This one contains three of the 48V AGM battery strings shown in Figure 6 As in the flooded cell bank in Figure 7 each string s positive terminal runs through a heavy red cable to a circuit breaker three are partially visible on the right The red cables from these breakers run across the tops of the batteries to a positive tie point on the left side Likewise black cables from each
189. ut voltage Input voltage can affect your system design in several ways so it pays to choose wisely Essentially a higher inverter input voltage makes possible a larger solar array and greater energy storage capacity capacity in the battery bank Typical input voltages are 12V 24V and 48V Your choices as might be limited as you select your candidate inverter below Generally lower power inverters operate on lower input voltages while higher power inverters need higher voltages Recommendation Choose the highest available input voltage available for your candidate inverter unless you have a specific reason to choose a lower voltage Choose a candidate inverter Whew You ve put a lot of time and effort into the project You know how much inverting capacity you will need so now it s time to learn what inverters meet your requirements and how much they cost and to choose a candidate inverter This is not a final decision but it gives you something to plan around You might later choose a completely different inverter but you can take it on faith that if you find an inverter that will power your loads you can buy batteries that will run the new inverter and you can buy solar panels that will charge those batteries Planning A Solar Power System Choosing an Inverter Page 26 That s why choosing a candidate inverter is the first step With that decision made you can move on to choosing the components to feed the invert
190. ve sighted accurately the compass dial will be set to the value of your magnetic declination In the future you can go to any location drive a stake rotate the entire compass to center the arrow under the needle sight across the compass base and have a co worker drive a second stake to establish a north south baseline at that location How much solar energy does a panel collect Basic sun calculations Alert Trigonometry ahead There is no way to discuss insolation exposure to the sun s rays and solar energy collection without using some basic high school trigonometry Scientific calculators with trig functions are readily available such as this Texas Instruments TI 30Xa http www walmart com ip Texas Instruments TI 30Xa Calculator 1043441 for less than 9 00 Of you can use a free online calculator such as http www mathopenref com calculator html or http web2 0calc com Planning A Solar Power System Site Survey Part 2 Page 51 Simply put the amount of energy a solar panel collects is proportional to the cosines of the sun s azimuth and elevation angles of the relative to the front of the panel Example Suppose it is solar noon when the sun is due south azimuth 180 Assume it is at an elevation of 68 above the horizon The PV panels are oriented with their faces pointing due south the same as the sun s 180 azimuth The relative angle between the sun s azimuth and the solar panels is 0 The cosine of 0 i
191. ve terminal of the next to create a string and increase the voltage or in parallel all positive terminals wired together and all negative terminals wired together to increase total amp hour capacity Why would we want to increase the voltage by wiring batteries in series Because some inverters can or must run on a higher voltage and increasing the voltage decreases the current for the same power load Consider In the example above the 12V battery must deliver 15A to satisfy the 180W load But if we wire two 12V batteries in series to get 24V the current would be halved to 7 5A 24V x 7 5A 180W Now if these two batteries together supply 7 5A for 10 hours they have supplied 75AH If the batteries are rated for 300 AH each each now is discharged only 2596 instead of one being discharged 5096 as above You can connect batteries in series to raise the DC voltage to the inverter as long as you don t exceed the inverter s maximum specified input voltage Connecting batteries in parallel also increases the total amp hour capacity but doesn t raise the voltage All batteries in parallel must produce the same voltage and the bank produces this same voltage Current is drawn equally from each battery The total amp hour capacity of the bank is equal to the sum of each battery s amp hour capacity If this seems complicated remember this summary Connecting a battery to other batteries adds its capacity to the group Series w
192. wer which is flowing through the bypass diodes on 11 s shaded cell strings 11 itself might be producing some power from its unshaded cell strings on the right side The entire array in Figure 18 is producing only 450W just 17 of its 2 7 KW potential for this date and time Diagonal shadows definitely take a toll As you do your site survey look for winter Oa chole the Dostovo codd do shadows that might cut solar energy production The site we chose for our PV array is the best These two photos demonstrate that sometimes it is available One site has fewer shadows but it is over impossible to avoid shadows Strive for a location 300 from the house and the PV feed cables would that is shadow free at solar noon and as many hours have to cross an underground utility electric line as possible on both sides of solar noon The array performs surprisingly well despite the Shadows vary in location direction and duration shadows At the end of the day Figure 17 was as seasons change The late August shadows in snapped the array had produced 70 of the power Figure 17 are pretty bad but not so much earlier in it would have produced if there were no shadows summer and there are no shadows at all from 10 30 through 1 30 sun time year round Bottom line Choose the best site you can find but don t fret too much about morning and afternoon shadows A site that is shadow free year round between 10 00 and 2 00 sun tim
193. y is producing 4 KW and the system is inverting 3 KW the remaining 1 KW is GUY wp iy Y l p charging the batteries or lost to 7 Se ae P x A 0 N n e A A lt Not slo imertyg30Kw 1A S PMtemiatsm ne Figure 1 Selling excess solar energy system inefficiencies The house is using only 500 watts so the system is selling 2 5 KW If it were not grid tied that 2 5 KW would not be produced capacity that isn t used Summary solar power always lowers your electric bill Non grid tied You lower your bill by not buying the power being used Grid tied You lower your bill by not buying the power being used and you lower it still more by selling the excess solar energy Reason 7 You can afford it A solar power system likely will cost a pretty penny so you should evaluate your financial situation to determine if you have the money and wish to spend it As you call vendors to inquire about solar equipment it s nice if the prices don t shock you and if the vendor knows you re in a position to buy not a casual shopper Depending of the size of the system you plan think in terms of it costing at least 5 000 and possibly 20 000 or more You might get some of that back In 2013 the Federal Residential Renewable Energy Tax Credit http www dsireusa org incentives incentive cfm Incentive_Code US37F is still in effect This offers a 30 federal tax credit for solar power and other green ener
194. ying the equipIYielit 2 oorr trea tnn tue ane sa eeu aan Aaa EaR aaa aAa VE ANANE NEAS n aee ASENNE 108 How will vow DOV TUE ICR iuis insisi naaus aaia aS iP oi Gne bri inni 108 Let s make a deal Etpe foe tte Sepa e eds Discite reece iPad eos FERES 109 Iri OUI Gasp eii E E E pt etus ed e I Fete cien IE I IL MET 109 EC Eten 109 Building perite oneris eei rii t ttes vaanien aaraa Neon DUE api V Eu PR E aida 110 Ill Gase sodio f asistente i ROI LA oy ener E d UE 110 Hirea Wee Qe gr NTS CN E 110 Bou VOS EIE ess bak as occas eect oH rdac il ua UO Ca dE ANC Nase MIA alan UE M QU MEA ED UR EC UMP VM EUM KE dE 111 WOK OMNE NOOT erma aenea ada TE EM 111 Dig holes Pour CONCH CUS sssri aa e eir R cer EE EEA E niens dee Erra ES 111 Qur choice a Nero E otE D PE 111 Follow InStr ctlOlls ioo c eoe htt reete rte etienne te ebrei opere ra cos clu avari aaa sei oec Osa 112 Perform compentirv or EROSDE a seco dein etant ebur asap qu nt apr TREES sn Teo a LER oi epos lMM a MM M bob EE saires EEU RSS 112 Take bri E P 112 Planning for heavy DBIBOEB uomen oE PERDU ERR RFR VERE METRHENL PRA MER E rIP P REHIS ARR riirii v YER V OPI 113 What We IG Mee eee s 114 Finishing Touches Keep a Clear path to the SYStG I siviccccsiscssscistecccinssiccsstcscssesssadstonstieisecensendeiosesserssoesnsndosensstoste 115 Take advantage of bonus system fEAtUIesS
195. you won t get in the way or impede work Do it yourself Anyone with a basic knowledge of carpentry and nuts and bolts can build a solar power system Although some of the underlying principles are technical and a bit complex building the actual system is little more than drill a hole tighten this bolt attach that wire Here are abilities you ll need to tackle the project yourself Work on the roof If you re planning to install the solar array on a roof you should be comfortable working up there You will need to attach brackets with fasteners through the shingles and into the sheathing Be safe Wear appropriate clothing and shoes Tie a rope around your waist and throw it over the roof to a partner on the ground to secure to a tree so you can t fall off A roof can be hot Stop if you feel overheated or lightheaded Here are other safety tips http www superpages com supertips top 10 roofing safety tips html Dig holes pour concrete A footer footing is a concrete base at the Our choice a power earth auger bottom of a hole sometimes extending up to You can dig footer holes with a post ground level Holes need to be deeper than your hole digger or a shovel but a local frost line typically 18 24 and will likely powered earth auger makes the job bea minimimof indiameter much easier An 8 hole 18 deep can A wooden framework made of 4x4 and 2x4 be bored in about a minute The two lumber doesn t need co
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