C:\WINDOWS\Desktop\Solar Calculator\Solar
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1. Cells This program assumes the installation of standard silicon wafers to generate electric current and an inverter to convert it to AC Alternating Current The conversion of solar energy to electricity is assumed to be around 7 efficient with this technology while its conversion to AC is assumed to be around 90 efficient If you know the collection and conversion efficiencies of the proposed equipment multiply them together for example 0 07 for wafers X 0 9 for inverter 0 063 then enter the product where indicated If you do not know leave blank and the program will use a default Enter the total square footage for Southerly facing panels Multiply the number of panels times their size in square feet 144 inches in a square foot Enter the answer in the box as indicated If installing an old system with round wafers adjust the square footage downward Enter the per kWh cost of electricity As of July 2007 if you live in Leverett it s about 0 17 per kWh This value can be obtained from your electric bill it s called the energy charge Take care to omit transmission charges when calculating electricity costs 6 The last data box is only to be used if you have specific information about the component energy performances of the proposed system If you do multiply the conversion efficiency times the inverter efficiency If you will not be converting to AC you don t need to include the inverter but you may need2. East November April facing windows have full sun from Nov May amp October through Apr 90 for May and Oct and 70 from Jun through Sep June September Surface Area This applies to the total square footage of glass facing a given direction For example if you have 8 south facing windows that are six square feet each you would enter 48 in the box under the word South Any data entry in this table should have information in the previous table Shade Free Area Factor for Windows for windows facing the same direction For example if you input 48 under South in this table then the Shade Free Area Factor for Windows table above should have shade free data under South as well To convert from square inches to square feet If necessary measure the dimensions in inches multiply the width times the height then divide that answer product by 144 to get square feet There are 144 square inches in a square foot Space Heating Information Enter the temperature you would ordinarily heat the space between 3 00 P M and 9 00 A M during the heating season This information is used to calculate heat loss through glass during periods with little or no solar gain It is also used for night time window insulation savings estimates Take a moment to look over the Heating Systems section information entered here effects fuel use and CO2 emission reductions Most should know what type of heating syste
3. certainly lead to increasing its air conditioning AC load in summer However on balance at least if you live in the northern U S it should be a positive trade off The sun is higher in the sky during summer so at least for walls the heat is less efficiently transmitted through glass this is not the case for direct gain solar roof applications though there are far more heating than cooling hours window shades or curtains can greatly diminish solar gain and well placed deciduas leafy trees can also help if necessary For the most part the farther south one goes the more closely this trade off needs to be examined An AC load analysis is presently beyond the scope of this tool The perception of warmth Probably one of the least appreciated aspects of energy conservation is how we perceive warmth For example imagine you are sitting in a swimsuit in aroom that is 72 degrees F Now imagine the walls are ice Didn t your mind tell you it suddenly got colder The same is true if we have an uncovered window on a winter s evening Part of how we perceive warmth has to do with how fast our bodys lose radiant heat So there will be unexpected advantages to covering those windows at night Another albeit less important factor is color Blues make us feel cooler while browns help us feel warmer To an even lesser degree textured surfaces are perceived as warmer than smooth ones etc
4. Solar Energy Analysis Tool User s Guide Copyright c RCS Energy Services 2007 resourcetechnology org General Information Understanding what is provided The is a free tool It provides reasonably good site specific solar savings information that a non technically orientated home owner can use Since its creation was pro bono it is a fairly bare bones utility Understanding this should help calibrate expectations with respect to the plainness of the interface and absence of input flexibility in some areas Nevertheless what makes this tool especially useful is it calculates heat losses through windows with or without insulation Thus it provides a net savings estimate It also provides estimated reductions in CO2 emissions based on fuel savings It is almost impossible to make precise predications when working with these kinds of solar calculations Nevertheless over 20 years experience went into this tool s creation its results are in sync with my 19 year old passive solar home It should provide information sufficient for ballpark savings estimates for residential direct gain solar hot water and photovoltaic projects Understanding what is required Solar calculations have many variables such as latitude declination from solar south seasonal variations in clear sky conditions monthly variations in solar angles glazed surface area number of layers of glass tree shading heat losses through glass during times of non solar
5. enson nesar Page 3 Space Heating Information sssssssssso0s00000 Page 3 Building a Greenhouse ccsccccsrrecesrscseees Page 4 Using Your Roof to Capture Solar Energy Page 5 Direct Space Heating Under Roof Page 5 Solar Hot Water cccccccrsssscsscsscscssocsseses Page 6 Solar Cells Photovoltaics ssccescesecscesees Page 6 Section II Results amp Other Information What the Results Mean Understanding the Results scsesceseee Page 7 What Heat Loss MEANS sscccssecsessseseees Page 8 Wood Heat and CO2 Production 00 Page 8 Solar Gain and Air Conditioning Page 8 The Perception of Warmth scsccsccseseees Page 8 Both the tool and this text are narrow so they can be loaded and viewed side by side Email questions etc to info at resourcetechnology org Data Input Information about DATA INPUT Scroll down to continue data input Look over the input screens then only fill in data that apply to measures you d like estimates for Clear Day Weather Data These codes are indexed to weather tables and latitude data to refine calculations The more clear days and more direct the angle of the suns rays the more solar energy penetrates the glass The input is also indexed to Degree Day information which helps determine how much warmth will leave the space at night This box must contain a code Location Adjustments Accuracy will diminish as one goes b
6. eyond Massachusetts Results for areas of NY CT RI NH and VT within 35 miles of MA should be reasonable check which county in MA is closest If you wish to use this tool for areas outside this range please forward local or regional weather data including seasonal sky cover data monthly solar heat gain data for a south facing vertical surface and Degree Day data to the resourcetechnology org website Once you are there E mail the information via the e mail link to info Adjustment factors will be estimated and forwarded as time allows The requested weather data really isn t that hard to get Glazing windows These codes are indexed to the insulating value of the windows glazing and their resistance to solar energy The more layers of glass the more insulation and impedance to the suns rays In order to keep data input easy while still meeting most needs only one selection is allowed If the space has both single and double paned windows run the program once for each then add the results Estimates are based on October through April solar gains The results for single glazing will provide a scientifically defendable value Although cloudy day and evening heat losses are subtracted from savings estimates heat gains for single glazing would still be considerable However in practice a fair amount of the heat gained will be lost through conduction infiltration and some even re radiated back to the outside unless wi
7. gain and potentially night insulation When fuel savings are added one must include the heating and hot water systems overall efficiencies energy content of fuels and their cost In short a certain minimal amount of information needs to be provided before reasonable site specific estimations can be generated Use Agreement This tool is essentially share ware You are welcome to copy it as often as you like and give it to friends enemies and relatives However it is not public property and it is an infringement of copyright RCS Energy Services c 2007 to incorporate it into a program or use it commercially This tool only provides the results of energy calculations The results are not recommendations as such We also have no control over project installation Therefore users must agree to hold harmless both RCS Energy Services and the Town of Leverett for damages that could be associated with the use of this tool including but not limited to failure of a measure to realize estimated savings Use of this tool confirms agreement to these terms Table of Contents Section I Data Input Information About Data Input Clear Day Weather Day input s s00008 Page 1 Location AdjustMents scccrscccccsrsccessceees Page 1 GIANG ss scuivcaseaessteasieieieiatesssianeavietensstanstete Page 1 Shade Free Area Factor for Windows Page 2 Window INSUlAtionn ccccccrrccersccsessccseeecees Page 2 Surface Ar
8. ing much of what you ve gained is to apply this simple rule of thumb the south facing glass for walls should not exceed 12 percent of the room floor space unless thermal storage will be used There are many books available covering solar design and thermal storage that can provide more about this Solar hot water and solar cell photovoltaics estimates are more true to life since these sorts of issues are far less pronounced What does heat loss mean For this tool heat loss means the energy lost through the glass between 3 00 P M and 9 00 A M during the heating season and during times of estimated cloud cover If you entered a value in the box Enter R value here for window coverings that value has been factored into the heat loss estimates Do not include an R value for window air films the program does that automatically or if insulation is used it assumes a certain amount of air movement between the glass and insulation thus negating the air film s effect which in practice is what usually eventually happens Wood heat and CO2 production Many consider CO2 production via wood burning stoves environmentally neutral However in the short term it contributes to atmospheric CO2 levels the same way as fossil fuels There are many pluses and minuses to burning wood for heat most of which go beyond the scope of this user s manual Solar gain and air conditioning Increasing your home s solar gain in winter can
9. m they have and what fuel provides space heat see Heating System Codes and Fuel Codes on the data input screen Heating System Information Heating System 1 and Heating System 2 Enter the Heating System Codes and Fuel Codes as indicated on the screen If you only have one heating system then only enter data for the system on the left Heating System 1 Enter the contribution of each here If you only have one heating system enter 1 in the left column If more than one enter a best guess contribution in terms of heat provided by not annual fuel cost of each system For example if you heat more with oil than wood then System 1 might be 0 6 and System 2 might be 0 4 The values must be entered as decimals and when added together equal 1 Enter fuel cost per unit here What does it cost in dollars and cents for each unit of fuel you buy For example 2 00 per gallon of heating oil or 0 168 per kilowatt hour kWh of electricity take care to omit transmission charges when figuring electricity costs Building a Greenhouse Putting a 1 in the box tilts the southerly glass to 60 degrees from horizontal as opposed to 90 for a standard wall Thus the space will get more solar gain Be sure to input the code that most closely represents the variance declination of the southerly wall from solar south Solar south in Leverett is about 13 degrees west of magnetic compass
10. ndow covers are used Single glazing is not recommended for living spaces unless significant steps would be taken to retain and store solar heat Solar south in Leverett is about 13 degrees west of magnetic compass south Not all scenarios will result in net savings For example even southwest facing windows with minimal shading can be net energy losers if curtains or some form of night insulation aren t used Window Insulation This may require some additional information The R value of a material is its ability to impede heat flow The higher the R value the less heat we lose For example the punky fibrous rigid insulation with the shiny foiled surface has an R value ranging from 7 1 to 7 7 per inch of thickness this type of insulation should probably not be used indoors Blue board has an R value around 4 5 Blanket type inside insulations can also vary widely ranging in R values from say 3 to 6 depending on composition Regular curtains can range from probably 1 0 to 3 0 and even shades can provide some help Rigid panel window coverings can offer R values ranging from 4 to 7 but can be either more cumbersome to handle or mechanically challenging to install Although blanket style inside window insulation can be the most expensive and technically the least effective their aesthetics and ease of use usually render them the system of choice Also note that most of the savings come from the first few R s The rea
11. son for this would take yet another paragraph to explain It should not be difficult to obtain the specific R value of a system once it has been selected either by asking the seller or by checking the manufacturers literature Whatever inside system is installed care should be taken to restrict air movement between the glass and insulation Glass surface heat loss calculations include air films along with evening and cloudy day losses Shade Free Area Factor for Windows This question is important and requires some thought You are asked to estimate what proportion of a surface is exposed to direct sunlight You don t have to supply information about all windows and walls only those which pertain to your solar project In many cases you ll have to average across many windows That s OK just do your best but remember the estimates you get can only be as good as the information provided Inexpensive tools are available to help with this assessment the Solar Pathfinder and Solar Site Selector are just two examples both can be Googled found on the web As a very course rule of thumb a single deciduas leafy tree will let about twice as much solar energy through in the winter as summer It is important to remember that you are inputting a decimal value that represents the portion of the surface exposed to the sun not the square footage nor the amount shaded Example of data input The box at the left indicates that the
12. south This section relies on the above window data do not include any house data if evaluating a greenhouse Greenhouses vary greatly in composition and structure and sometimes even function Accommodating those variables would require a larger tool than can be offered at this time What can be provided is a rough idea of gains and losses through glass surfaces If you wish to use plastic the materials seller should be able to provide a conversion value to adjust savings and losses from glass to plastic there are many different types of plastics used For this tool to provide a greenhouse estimate If the easterly and westerly walls will be glass include them in the window sections above otherwise omit that data If the roof will be glass and is about 45 degrees from horizontal put that information in the Using Your Roof to Capture Solar Energy Direct Space Heating section If window insulation has been recommended it will be applied to the glass walls and glass roof Although the solar gains and losses estimated through southerly glass are calculation based easterly and westerly windows are assumed to balance out up to around a 20 degree declination from east and west one end of the greenhouse being more southerly the other more northerly After about 20 degrees the end wall glazing estimates are no longer valid In most cases this should not be a problem since home attached greenhouses usually do not have glass end walls E
13. stimates are based on October through April solar gains Using Your Roof to Capture Solar Energy Put a 1 in the box at the right if you wish to utilize roof solar energy for space heating hot water and or solar cells photovoltaics The following calculations are based on a southerly facing roof slope of about 45 degrees Shade Free Area Factor Enter the data for the most southerly facing roof slope as described in Shade Free Area Factor for Windows above Roof Area Declination from Solar South At 25 degrees off solar south 91 of the sun s heat rays can still be captured at 30 degrees it drops to 85 by 45 degrees it s down to 71 The Savings potential drops off rapidly after 45 degrees You will either need a magnetic compass or accurate house plot plan to determine solar south Solar south in Leverett is about 13 degrees west of magnetic compass south Input the code number that represents the declination variance of your roof from solar south For example if it s 21 to 25 degrees off enter code number 2 As indicated above you will be able to get most of the available energy until the declination exceeds about 38 degrees Direct Space Heating Enter the square footage for Southerly facing roof glazing This is for direct gain for space heating ie the upstairs bedroom of a cape or a cathedral ceiling Enter the distance in feet from the floor to the bottom of the window Do not en
14. ter a number smaller than 3 The air around high windows and the like is warmer than air at shoulder level so night time heat loss will be greater for high windows Estimates are based on October through April solar gains Be mindful that heat gain during the summer months may be enormous and you ll need a way to get snow off the glass hopefully without breaking it in winter Although analysis will show this is the most cost effective way to get heat into a living space it requires forethought skilled workmanship and an appreciation for just how much heat and potentially fabric and wood damaging light would enter the space During warmer weather if window insulation is used and the window can t be isn t opened the buildup of heat between the glass and insulation can cause serious problems Solar Hot Water Enter the total square footage for Southerly facing panels Multiply the number of panels times their size in square feet 144 inches in a square foot Enter the answer in the box as directed Enter the code number that best matches your current hot water heating system Look at the table then enter the number that best describes what heats your domestic hot water Estimates are based on year round solar gains Enter the per unit fuel cost to heat hot water How much do you pay per gallon CCF or kWh to heat domestic hot water For example if propane enter the cost of one gallon of propane Photovoltaics Solar
15. to account for battery losses and energy loss over wires Estimates are based on year round solar gains Results amp Other Information What the Results Mean Understanding the Results Accurately estimating solar heat savings in dwellings is tricky at best The straight forward part is presented in the Results where the amount of solar energy entering the space is converted to units of heat called BTUs British Thermal Units for those who have to know This value is indexed to the fuel energy content and heating system inefficiencies to provide savings ie 200 gallons of propane and 400 This is exactly and only what the space heating results mean To explain further If the sun heats the space to 80 degrees F and the results say you would save 200 gallons of propane or whatever are you really saving that much if you would have only heated the space to 68 F Obviously not some of that extra heat is being lost through the windows roof and walls and some is lost through infiltration The greater the difference the temperature the faster the heat movement Nevertheless it s not all wasted Much of the extra heat is absorbed by floors walls furniture and the like and will be re radiated into the living space after sun down All this can be determined mathematically but the amount of data entry and calculating required would be considerable A way to avoid an over heating problem without wast
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