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Final Design Report

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1. 5 0 2 4 6 8 10 12 14 16 Velocity m s 0 M Figure G 2 An example distribution of wind velocities shows a low average wind velocity Figure G 3 When the power density and wind resource curves are combined the power available at a given wind speed over long periods of time becomes apparent 27 Now that the reasoning behind the specified outputs is understood it is important to investigate the capabilities of the blades selected In order to accurately calculate the torque output radial forces and angular velocities of the blades without testing it would be necessary to perform some sort of computational fluid dynamics for the distinct blade profile However performing such an analysis is beyond the scope of this design and would require access to the original design of the blades Therefore a back door approach was taken to calculating those attributes The angular velocity of the blades is the most important attribute of the blades relative to the generator and Table G 1 The RPM of the blades for the requirement specification The tip to speed ratio mentioned in Various wind speeds calculated using an assumed tip to speed ratio of 5 5 Wind Speed Tip Speed RPM m s m s speed ratios for three bladed turbines are said to range from 5 to 6 for good designs this is consistent with figure E 2 in the efficiency discussion If a value of 5 5 is chosen for A and the diameter of 1 57 m for the blades
2. Efficiency 5 Blades 0 33 The values for all of the subsystem efficiencies with the Gears and 0 95 exception of the blades and the alternator shown in table E 1 were Shafts estimated by internet searches for typical values for those ARE 0 64 components The efficiency of the alternator was found at 1160 Wiring 1 RPM from the specification of the alternator that was selected Charge 0 8 more information on that is available in the alternator selection section of this report and the efficiency of the blades was back Battery 0 66 calculated from that value using eq E 7 with generator 0 2 EDU 0 9 Thus from table E 1 and figure E 2 the calculated value for Cp is at the lower end of the typical range of 3 bladed wind turbines Also the overall estimated efficiency of the system can be found from eq E 6 to be E 9 Nsystem 0 33 0 95 0 64 1 0 8 0 66 0 9 0 0950 9 5 E 10 Outputsystem Nsystem 5 eS Vi p OutpUtgenerator 1 2 S Vi Even though system may appear to be quite low the outputs outlined by the requirements specification are still met First of all as was already mentioned at the beginning of this section the outputs specified were for the power coming directly out of the generator not out of the outlet In order to determine if BEAST meets the specifications Excel was used to generate a table of outputs at various wind velocities Tab
3. User Intervention 21 0 Percent Charged Indicator tL Functional Description of Blocks Stand Raises the wind turbine up to more productive winds and keeps the lowest blades at least 2 13 meters off of the ground The stand provides support in winds up to 20 m s Furling Controller Limits the effective wind speed acting on the blades by turning the blades out of the wind up to 90 This mechanical controller acts as protection against large wind force and keeps the turbine operating at a safe speed Inputs Wind speed 0 20 m s and direction Outputs Effective wind speed from 0 15 m s Blades Mounted on the input shaft the blades convert the effective wind speed into a usable torque Inputs Effective wind speed from 0 15 m s Outputs 0 1000 RPM Alternator A permanent magnet DC alternator which converts the mechanical energy of the blades into electrical energy Inputs 0 1000 RPM Outputs DC power 0 74V 0 11 A Water Resistant Electronics Housing Provides water resistance to the electronic circuitry Charge Controller Converts and regulates the power coming from the generator into a proper power for charging the battery It also prevents charge backflow and calculates the battery charging rate Inputs DC power 0 74 V 0 11 A Outputs DC power 13 5 18 V 0 3 0 A Battery A battery which stores at least 200 Wh of energy Inputs DC power 13 5 18 V 0 3 0 A Outputs DC power 12 V 0 20 A
4. Npower and Voltec both received a higher produce a modified sine wave most laptops use a modified sine wave unless otherwise specified and power output of approximately 200W The Samlex and Npower inverters are approximately 25 while the Npower inverter is 19 95 The Samlex inverter has a maximum efficiency of 9096 compared to the Voltec and NPower inverters which are 8596 efficient The three inverters are all very good but because weight and price are big items in the design the Voltec seems to be a better option based on the decision matrix The Voltec is displayed in figure 1 2 along with the features specified by the manufacturer table 1 2 on the following page Figure 1 2 The Voltec 200 meets and exceed all the design requirements 200 watts continuous power 500 watts peak power USB Outlet Includes 36 cigarette lighter adapter and DC cables for direct battery connection High voltage protection Low voltage protection Overload protection Low battery alarm Low battery shutdown Table 1 2 The manufacturer specified features of the Voltec 200 Deliverables Attributes Overload shutdown Yes Thermal shutdown Yes Short Circuit shutdown Yes Product dimensions 6 5 x 4 125 x 2 59 Project Management Budget Analysis The overall budget is nearly 200 larger than was originally forecasted in the preliminary design presentation This was due primarily to the purchase of a higher quality and pricier alter
5. A value of L 4 for L D 2 and Larm 5 are chosen for the directional fin because they meet the criterion while still maintaining a good factor of safety 40m along with lower overall weight and size than any larger values of L The fin will be constructed out of Plexiglas because it provides a low weight high strength and low cost solution The arm will be constructed out of aluminum to stay consistent with the rest of the system design coupled with many of same reasons it is used in the rest of the design namely a high strength to weight ratio Bending 50 calculations were performed on a 5 m long aluminum Figure F 10 A summary of the dimensions of the rod with a diameter of 1 in and a thickness of 065 in directional fin and for a velocity of 20 m s a factor of safety of 2 22 is still evident for a yield stress of 110 MPa The last column in table F 6 displays the location of the center of mass of the shape This location must be the location at which the fin is attached to the rod in order for the moment calculations to be valid therefore the end of the aluminum rod must line up with 21 m from the front rounded edge of the Plexiglas directional fin figure F 10 An overall drawing of the furling mechanism and directional fin is available on the next page while details on the individual components can be found in the appendices 38 Figure F 11 The complete furling and directional fin subsystem b7
6. Stand Design The stand for BEAST Fig SD 1 amp SD 2 is designed to elevate and support the turbine be a steady platform for its operation be lightweight and be easily assembled and disassembled To meet all of these criteria two designs were considered A set of three tubes of the same diameter with flared ends that stack was considered but not selected because when the tubes are stored they take up too much volume A tubular telescoping design with the largest tube at the bottom and two upper sections consecutively smaller supported by anchored tethers was considered and chosen for the upright sections Three sections of approximately one meter each are used to achieve the required height of the fan The lowest point that the fan blades my turn is 2 13m as a safety precaution to keep them above average American head height of 1 76 m www cdc gov Since the uppermost section is the smallest it was analyzed in a buckling load analysis and the results are shown in Table SD 1 The critical buckling load was calculated using n EI I Eq SD 1 where is end condition factor E is the elastic modulus of the material I is the area moment of inertia and L is the length of the section being analyzed in meters It was found that a 0 0127M outer diameter 0 011m inner diameter aluminum 6061 T6 tube would sufficiently support the estimated load of 67N with a factor of safety of 27 for a single section A tube of full length o
7. System Overview SO Efficiency Discussion E Alternator Selection A Blade Selection and Hub Design BL Gearing G Furling and Directional Vane Housings H Battery Selection BA Electrical System Overview ES DC DC Convertor Selection DC Voltage Monitor VM State of Charge Indicator SC Power Inverter Requirements Specification Backpackable Easily Assembled Sustainable Turbine BEAST Requirements Specification Sean Smith Josh Gibb Moses Rotich Yixiao Zhang Overview Many of us are dependent upon our small electronics ranging from cell phones to laptops for functions varying from information gathering to long distance communication Unfortunately all of these devices are dependent upon electricity in the form of rechargeable batteries which only last for a set period of usage time and then depend on a steady source of electricity for recharging On extended stays in areas which do not offer an electricity source an environmentally friendly sustainable and easily implemented power source is needed The BEAST will be a solution to that problem intended specifically for long term trips into remote areas and visits to developing nations where a base camp is required Military applications and disaster relief efforts are also key markets The device will consist of a wind turbine that can fit within or on a hikers backpack at a reasonable weight be easily assembled in the field with little technical prowess and supply
8. 9 00 Y N 28 95 Power meter 1 18 99 18 99 glensoutdoors com 5 99 Y N 18 99 LM5118 1 50 00 S0 00 Digikey com sample free Y N 50 00 LED Indicator 2 0 00 0 00 Digikey com sample free Y Y 0 00 MAX5033 il 50 00 50 00 maxim ic com sample free Y Y 0 00 Resistors 20 0 00 0 00 tubedepot om sample free Y N 0 00 Diodes 8 0 00 0 00 aalltronics com sample free Y Y 0 00 MAX6458 1 50 00 50 00 maxim ic com sample free Y Y 0 00 Capacitors 5 0 00 0 00 Digikey com sample free Y N 0 00 Total parts 43 236 94 Total Shipping 24 99 Overall Total 261 93 Total Spent 205 94 Work Breakdown and Schedule Analysis The original work breakdown structures for BEAST are shown on the following pages They were very useful for defining the roles of the individual engineers working on the project Responsibilities were held to rather tightly but when one of the team s engineers finished a pivotal segment they would often jump over and assist on another section to move the design along Specifically Sean took nearly full responsibility for the furling design even though Josh is shown as being a co designer on that portion Also once the blades were selected Josh took full responsibility for explaining the design decision On the electrical side Yixiao and Moses worked very closely on every aspect of the charge controller while they each finished the other components they were assigned to work on individually Items tha
9. 3 47 58 mm Figure 1 Two of the 12 V 120 Wh battery packs shown above will be connected in parallel to meet the requirement of at least 200 Wh of storage Each pack weighs 3 35 Ib 1 52 kg sa L DC DC Converter The DC DC converter is essential for the overall electrical design because it protects the rest of the circuitry from the unstable power fluctuations of the alternator s output DC DC converters essentially smooth out their inputs and then output a desired range of voltage and current It is especially desirable for the purposes of BEAST s design for the DC DC converter to accept a very wide range of voltages as its input This design requirement is driven by the large range of voltages produced by the alternator for the designed generation RPMs figure A 2 in the alternator selection section A decision on the DC DC converter was made by generating a decision matrix table DC 1 with values ranging from 1 worst to 5 best The LM 5118 a wide voltage range buck boost controller was chosen because it possessed the largest voltage input range available which is the most important design criterion as evidenced by the decision matrix Table DC 1 Decision matrix for DC DC converter Criteria Weight MAX5093 MAX 1703 lon LM5118 High range of voltage input ost ize Weight otal Appropraite current output Because of the high cost for an LM 5118 evaluation board it was decided to purchase all the individ
10. Percent Charged Indicator Indicates the percent charge available in the battery Inputs Voltage 0 12 V Outputs Visualization of the percent charge available in the battery On Off Switch Determines if the energy available in the battery is to be converted to Inputs DC power 0 12 V 0 20 0 A and human intervention Outputs If the switch is on then 12 V DC will be allowed through otherwise no current will be allowed past this point Power Inverter Converts the DC into a usable 115 V AC which is supplied to the user via a standard outlet Inputs DC power 12 V 0 20 A Outputs AC power 115 V AC 0 1 74 A Subsystem Design Efficiency Discussion The efficiency of a power generation system is a key factor for the overall effectiveness and viability of that system The BEAST is no exception which is why this design emphasizes efficiency for key components The efficiency of the power generating components namely the blades and the alternator were assumed to be competitive when specifying the system s capabilities The output of the generator stated in the requirements specification specifically a 15 W output given a 6 m s wind velocity and 130 W given a 12m s velocity were chosen with an assumed 2096 efficiency for the output of the generator This means that the amount of power leaving the generator and entering the charge controller ought to be at least 2096 of the overall power available in the wind In order to unde
11. SJ SJ SJ M Y J M Y MJ S J M Y S J M Y 64 Work Breakdown Structure Spring 2010 51 00 52 00 53 00 53 10 53 11 53 12 53 13 53 14 53 20 53 21 53 22 53 23 53 24 53 25 54 00 55 00 56 00 57 00 58 00 59 00 510 00 511 00 Project Management Documentation Parts Assembly Testing Mechanical Systems Alternator Testing Blade Mounting Furling Stand Electrical Systems Charge Controller Power Inverter User Interface Battery Testing Encasement Project Status Report Formal Presentation System Integration System Testing and Modification Acceptance Tests Complete User s Manual Final Report Final Project Formal Presentation Engineering Showcase Ensure that the team is on schedule and under budget Keep records of all design work research and tests Assembling of components Assembly of mechanical components Test the alternator s output for given RPM s Construct the blade mount and mount the blades Construct the mechanical controller Construct the stand Assemble the electrical components Construct and ensure that the charge controller outputs steady DC Construct and test the conversion from 12 V DCto 125 V AC Test the indicators switches and outlet Perform a runtime test on the battery to ensure capacity Construct weather resistant encasement and test Present th
12. force from the motion of the blades To find the max stress on a single bolt hole use Eq BL 3 where the area is the diameter of the hole 6mm times the thickness of the plate 4 76 mm The max stress turns out to be 64 2 MPa and the yield stress of Aluminum 3003 H14 is 145 Mpa which yields a factor of safety of 2 26 Having a factor of safety this high is not needed but the cost of material is such that purchasing a thinner sheet of aluminum would actually be more expensive The aluminum tubing is being purchased in a single order and the plate for the hub is being purchased from the same supplier to save on shipping Technical drawings of the hub can be found in the appendices Gearing Gearing was originally thought to be a part of the system design acting as a means of increasing the RPM of the input shaft attached to the blades to an RPM suitable for the alternator However gearing produces losses adds weight and reduces the torque applied to the alternator This section is not about gearing selection but rather it is here to provide the justification for a direct drive gearless design This justification involves a balance between 1 the specified outputs of the generator 2 the capabilities and angular velocities of the blades and 3 the output capability of the generator First of all the requirement specification states three distinct design point for output output must begin given a 4 m s wind speed produce at least 15 watts given a
13. generated power into power suitable for charging the battery Converts the DC power in the battery into 125 V AC for the user Outlet On Off Switch Charge Rate Indicator Charge Amount Indicator Design a box to protect the electronic components from weather Final system and subsystem design Presentation of final design Constraints and specifications met Documents Engineering Notebooks Verbal confirmation with professors Document Document Presentation Detailed design of subcomponents Detailed design of mechanical components Product number reasoning specifications Detailed design CAD drawing Detailed design CAD drawing Detailed design CAD drawing Detailed design CAD drawing Detailed design CAD drawing Detailed design of electrical system components Detailed design product number and specifications Detailed design schematics Detailed design schematics Detailed design schematics Detailed design CAD drawing Document Presentation S Sean J Josh M Moses Y Yixiao Aug 23 Dec 10 Aug 23 Dec 10 Aug 23 Sept 7 Sept 8 Sept 28 Sept 29 Oct 12 Oct 14 Sept 29 Nov 30 Sept 29 Nov 30 Sept 29 Oct 12 Oct 13 Nov 2 Nov 3 Nov 16 Nov 17 Nov 30 Oct 13 Nov 16 Nov 3 Nov 30 Sept 29 Nov 23 Sept 29 Oct 12 Sept 29 Oct 26 Sept 29 Oct 19 Oct 27 Nov 9 Nov 10 Nov 23 Nov 9 Dec 7 Dec 10 S S S J M Y S J M Y S J M Y S J M Y S J M Y
14. include a counterweight mechanical controller a spring mechanism and computer controller braking Table F 1 Decision matrix for the means of furling The counterweight makes use of an AA angled hinge and the same principle that Weight 1 3 3 B causes a refrigerator door or any door for Price 0 3 that matter to move when hung off center Reliability 0 15 This mechanism is relatively inexpensive Simplicity 0 15 fairly precise and reliable However it is by far the heaviest of the three options whichis a high weighted criterion due to the Total 1 9 7 9 portable nature of BEAST Weighted Total 1 45 2 25 1 65 The spring controlled mechanism uses preloading of a linear torsion spring to resist Tail Vane the wind force until the furl velocity is reached then begins furling It is lightweight inexpensive and simple yet is deficient in precision and reliability Turbine Axis The lack of precision and reliability is the reason this is the least common method used for small wind Offset 0 turbines However furling is a last resort that should i have a factor of safety for the velocity of furling Alternator anyway thus leaving room for lack of precision and exacting performance A computer controlled mechanism makes use of an anemometer and a microprocessor to track the wind speed and apply a mechanical brake once that velocity is reached The computer controlled Wind F
15. power that you 12 20Ah 1 74A 60 Hz can use to charge a laptop or cell phone figure 1 1 _ BEAST s inverter draws its power from the two NiMH batteries 12V 10Ah each wired in parallel as described Figure 1 1 The role of the power inverter is to convert the DC power in the battery in to usable AC power in the battery selection section of this report It then outputs 115 VAC to the user note that 125 VAC was stated at the output in the requirement specification but upon further research it was discovered that most inverters output a still acceptable 115 VAC Table 1 1 DC AC inverter selection decision matrix BEAST s inverter s primary application ER z Criteria Weights Npower Samlex Voltec is for cell phone and laptop charging Because the inverter technology is well established and Input Voltage in Its constructing one in house After analyzing Power Output several power inverters the NPower Samlex Watts 0 3 2 2 2 atts and Voltec inverters were found to meet our needs A decision matrix for selecting a specific inverter table 1 1 was generated based on a 0 Npower was heavier at 907 kg while the Voltec Lo Weighted Toti 21 22 24 score on other because they both have a cover on the output receptacle The three inverters all easily available as a reasonable price it was decided to purchase an inverter instead of and Samlex had similar weights around 39 kg
16. selected is used then Eq E 5 can be rearranged to solve for the angular velocity of the blades at different wind speeds qo 736 803 870 937 the efficiency discussion earlier in this report was used to estimate the angular velocity of the blades in Excel table G 1 Typical tip to G2 RPM The blade manufacturer states that the blades can spin up to 1500 RPM without harm From table G 1 this falls outside of the range of reasonable wind speeds 15 00 82 50 1004 16 00 88 00 1070 Finally relating the capabilities of the alternator to those of 17 00 93 50 1137 the blades shows that BEAST can produce the specified power at all 18 00 99 00 1204 three design points without gearing of this justification is taken 19 00 104 50 1271 from the specification sheets supplied by the manufacturer which 20 00 110 00 1338 are available in the appendices The alternator produces 12 V enough to start battery charging with an input RPM of less than 209 which is less than the 268 RPM supplied at 4 m s thus meeting the first point At the second design point of 6 m s the RPM is calculated to be 401 at which point 15 W ought to be produced from the alternator specification sheet up to 46 W are produced at a lesser RPM of 365 thus meeting this requirement The third design point of 130 W at 12 m s has a calculated RPM of 803 while the alternator is rated to produce up to 129 W at 650 RPM and up to 206 W at 870 RPM t
17. 200 preload angle figure F 6 and d 3 175 mm table F 4 D 44 45 mm 1 1016 mm Free Body Length 152 4 mm length of wire 558 8 mm K 14 93 N mm degree Furling for lt 01493 N m degree 90 80 70 60 50 40 Theta Degrees 30 20 10 0 5 10 15 20 Wind Velocity m s Figure F 6 The furling response for the designed k Unfortunately spring manufacturers do not commonly sell springs with that many coils It is possible to have one custom manufactured but that is falls outside of our budget a manufacturer of springs was contacted for a quote on custom springs and the price of 160 was given Given that a spring which meets the requirements cannot be readily purchased at this point there are two options either change designs or find a way to manufacture the spring in house After a quick internet search the actual manufacture of the spring would not be too difficult so that is the route chosen Music wire with a diameter of 125 in can be purchased in a 24 ft roll for a reasonable price This wire will then be rolled around a rod of appropriate diameter while being heated by a torch The final spring will be quenched in vegetable oil and then subjected to 3 rounds of heat treatment in an oven The final spring design is shown in figure F 7 35 __101 600 JA 44 450 Figure F 7 The final spring design was drawn using Solidworks Directional Vane The d
18. 4 62 www metalsdepot com 1 x1 x0 25 0 00 Y N 14 62 Bearing P y N N Furling Pivot 2 11 40 22 80 www mcmaster com 0 00 Bearing PN 60715 15 N N stand hub 1 18 55 18 55 www mcmaster com PN 6655K22 6 08 0 00 Stand Tubing 0 065 in t 1 5 OD 0 00 M N Bottom 1 16 88 16 88 www metalsdepot com 1 37 ID 16 88 Stand Pins 6 2 49 14 94 Tractor Supply Co 1 4 x 1 3 4 NA N 0 00 Stand Tubing 0 065 in t 1 25 OD 5 50 00 M N Middle 1 513 68 13 68 www metalsdepot com 1 12 ID 13 68 Stand Tubing 50 00 Y N Top 1 10 76 10 76 www metalsdepot com 0 065 in t 1 in OD 10 76 Tail Rod Aluminum 1 55 38 55 38 www metalsdepot com 0 065 int 1in OD 5 71 5 38 Housing Electronics 10 x8 Optix N N Plexiglas 5 1 98 9 90 Lowes 5pcs NA 0 00 Stand Tethers 1 7 30 7 30 www campingsurvival com 150 ft 4 49 N N 0 00 Torsion Spring N N Furling 1 6 05 6 05 www mcmaster com PN 9271K136 0 00 Tail Spade Plexiglas T 1 98 1 98 Lowes 10 x8 0 08 int 0 00 Total Parts 27 523 28 Total Shipping 10 20 Overall Total 533 48 Total Spent 441 76 Electrical Budget Descripton Quantity Price per unit Price total Vendor Further details Shipping Ordered Received Spent Battery 2 74 00 148 00 allbattery com 10 Y Y 158 00 Professional Circuit Board 1 50 00 50 00 pcbexpress com N N 0 00 Inverter 1 19 95 19 95 donroe com
19. 6 m s breeze and at least 130 watts given a 12 m s wind speed Given that 12 m s is a very fast wind velocity that rarely occurs one might ask why it is included at all as a design point The reasoning involves industry standards which are based on the total power availability for given wind speeds From Eq E 1 it is apparent that the power Wind Power Density available has a cubic relationship with the wind S velocity figure G 1 However the average wind speed tends to be relatively low and have a low d power density figure G 2 It is useful then to design ies a wind turbine to be most efficient at the speed at c D which the most power is available which can be E 20 found by combing the wind power density and wind 600 resource plots into a total power availability curve a 300 figure G 3 From this curve it is apparent that rating 0 AL __ 1 3 5 9 11 13 15 Wind Speed m s a wind turbine for 12 m s is appropriate Rating a turbine at higher speeds also has marketing benefits it sounds much better to a customer to promote a 130 W Figure G 1 The power available in wind increases at turbine than a 15 W turbine a cubic rate with respect to the velocity The Wind Resource Power Availability d 7 36 m s 80 20 70 5 T 60 50 15 40 Weibull gt 50 20 n Distribution 10 1
20. A 1 Table BA 1 Properties of various battery types NiCd Lead Acid NiMH Li ion Overcharge Tolerance Moderate High Low Very Low Cost Moderate Inexpensive Moderate High Cycle Life 1500 200 300 300 500 500 1000 Efficiency 7096 9096 7096 9296 6696 8096 9096 Environmental Friendliness Moderate Low High Low Maintenance Not Requirement 30 60 Days 3 6Months 60 90 Days required Energy Density Wh kg 45 80 30 50 60 120 110 160 A decision on battery type was made by generating a decision matrix table BA 2 with values ranging from 1 worst to 5 best Because of their high energy density and relatively low price batteries seem to fit BEAST the best Two 12 V 10Ah NIMH battery packs figure BA 1 were selected at a reasonable price They are to be connected in parallel to produce a 12 V battery pack with a total capacity of 240 Wh thus exceeding the requirements Other higher voltage battery packs were considered because of lower price for the same amount of storage capability However 12 V was selected because the alternator produces a 12 V output at much lower wind speeds thus allowing for a wider range of generation wind velocities Table BA 2 Decision matrix for battery type Criteria Weight Cost Over Charge Tolerance Cycle Life Battery Capacity Environmental Friendly Wieghted Total Weight NIMH Li lon Lead Acid 0 2 4 5 1 0 2 4 1 0 2 1 0 05 2 5 0 3 5 5 1 0 05 5 5
21. Apr 20 May 3 Apr 13 May 3 5 May 8 May S 5 M Y S J M Y SJ 5 S J J M M J S J M Y S J M Y S J M Y S J M Y S J M Y S J M Y S J M Y S J M Y 65 Met 0102 92 1 OLOZ 6L LL 00 01 4 uonejuesaJg OLOZ G ZK 0102 6 2 een SE OLOS Z ZL oroz e Lr ubiseq Ieu 00 84 soiuoJ4129 3 OLOZ EZ LL OLOZ OL LL 14 00 ubisag o OLOZ Z Zt pues luas OL0Z 9L LL OLOZ EL OL ubiseq EWO 7 E MQ 0102 01 21 OLOZ EC 8 jueujeDeuey 12 007 L3 1172 0112 OL Z 0121 01701 ore 6 92 6 61 6 5 8 62 8 22 us ues dl OLOZ HEYI LLOZ Oc LLOZ ZL E Buuds 00 215 1102 8 8 1102 8 8 00 11 3 6 L LOZ S S uonejuosalg 4 129 014 IEU 00 015 LLOZ E V V 00 68 LLOZ SZ V sisa 00 25 110 9 9 LLOC E S 5 LLOZ E S LLOZ 8c V LLOZ Z2 v LLOZ LL E uoneoyipoiv pue 1 ueis S 00 98 3 6 LEOZ OL
22. B E A S T Backpackable Easily Assembled Sustainable Turbine Final Design Report December 7 2010 Sean Smith Mechanical Engineer Project Manager Joshua Gibb Mechanical Engineer Moses Rotich Electrical Engineer Yixiao Zhang Electrical Engineer us Table of Contents Requirements Specificatioii 5 ierit Leon tid cer reat erani Pe nk e dea cL de nee Pas dee denk eren aude ded 4 System T 8 System OVERVIEW Re 9 Block DI 10 Functional Description on Blocks 10111111 1a 11 SubsystemiDesiBli 5 ipio adan Dn 13 Efficiency DISCUSSION n 14 Weight hana ANAN etes 18 Alternator Selection ui WA aa awa daaa zaweza 19 Mechanical Design LE 22 Blade Selection and HUD i iiec rette E E E S 23 mha NG 27 Furling and Directional Vane sesenta nns 30 Seno V 40 HOUSING a ana tae cde teet cerei 42 Electrical 44 Electrical System OVervieW 3 E STA 45 Battery Selectiori c 47 WA CONVG rR EE 49 Voltage Monitor Circuits a 52 State of Char
23. F 9 Aeffective a cos 1 00 _ L T L LR 80 Se J 60 7 50 S 96 of Original Area 30 10 E 0 0 10 20 30 40 50 60 70 80 90 Theta Figure F 3 The effective area becomes an ellipse and follows the curve of cos 0 Figure F 3 describes the effective area with respect to furling angle However 6 itself is a function of Frurtea For a torsion of spring of constant k and an offset of O Moment Ffurlea 0 F 10 0 k k Thus producing Fruriea as a function of Fe rea F 11 Frurtea D cos aree T However for the sake of this design the area will be approximated as constant for force calculations This means that the final velocity of furl will be higher than that specified for a constant area Let us explore the ideal furling conditions if a good design is implemented to give target for BEAST s design If the velocity of furling is chosen to be 15 m s as suggested by the requirements specification and a target for a completely furled state is chosen to be 18 m s then a spring can be designed and selected with a spring rate suitable for furling between those two states and for resisting furl before 15 m s is reached Figure F 3 demonstrates ideal furling for such a case Furling for k 0 024 N m degree Theta Degrees 5 10 15 20 Wind Velocity m s Figure F 4 The value of k was c
24. F7 21 7 22 7 23 F7 24 F7 25 Mechanical Design Generator Selection Blade Design Gear Design Housing Design Furling Design Stand Design Electrical System Design Battery Selection Charge Controller Power Inverter User Interface Electronics Housing F8 00 Final Design Report F9 00 Final Design Formal Presentation Ensure that the team is on schedule and under budget Keep records of all design work research and tests Make a final choice of which project to pursue Technical description of the project s goals Technical Description of the systems operation project plan and budget Technical Description of the systems operation project plan and budget Design the subcomponents Design of Mechanical Systems Select a suitable generator for wind generation Design or find blades suitable for the generator Design a gearing system to bring increase the RPM s to the rated RPM of the generator Design a housing for the gears and generator to sit atop the stand Design a mechanical controller to limit the maximum wind speed of generation Design a stand which will raise the wind turbine up to better winds and keep the lowest blades from passing within 2 13 meters of the ground Design the electrical system which stores and supplies the generated power to the user Select a light wieght durable battery capable of storing 200 Wh of energy Regulates and converts the
25. V LLOZ Lo uoneDeju wa sAs 00 86 z o LLOZ OL E SNES 1 00 75 LLOZ v L Z bunso Kieneg veces LLOZ 8V L 12 LLOZ OL E LLOZ LL E 6 L LOZ Z Z LLOZ LZ Z LLOZ 8L L suiejs S 29119913 65 LLOZ L Z akes L LOZ 8 L L 10eu1 y LEES i LEOZ LL E 5 LLOZ LZ Z LLOZ LE L LLOZ 8L L OLES 292 LLOZ LL E LLOZ 8L L Bunse j Ajquiessy sued 00 68 LLOZ 8 L L Juawabeuew 00 L 292 M98 GL 1102 8 8 98 91 PILL we soz oer 2 12 2 02 2 61 2 9 1 62 91 ysiul4 pueg L 102 8 S oa oe NEN References http www fao org docrep 010 ah810e AH810E10 htm http www clemson edu scies wind Poster Schmidt pdf http www windynation com web tip speed ratio tsr wind turbine blades how calculate and apply tsr blade selection Fluid Mechanics Fundamentals and Applications Yunus A Cengel John M Cimbala pg 243 http para maxim ic com en search mvp fam super1 amp tree master
26. ape shown in figure F 9 was chosen due to its ability to be streamlined when aligned with the wind lt gt yet still maintain a large surface area for direction change when necessary The drag coefficient for wind hitting the Y 5 qua D broad side of such a shape can be estimated from similar lt gt shapes to be slightly above 1 For the sake of any further calculations Cp 1 for the broad side thus introducing a small factor of safety when F 18 is used to determine a Figure F 9 The semicircle in front causes this shape desirable area The area of the chosen geometry is given in to be more streamlined while still maintaining a large surface area eq F 19 to be D A spreadsheet was generated in Excel to calculate the values of L and D necessary to meet the specified criteria table F 6 37 Table F 6 The green highlight in the cells indicates that the cell meets the criteria Vane Area Calculation L d Larm Cd Ablades Offset Nth m m si m 2 0 5 1 1 935928 0 04 0 33 Minimum Vane Area 0 051108497 L d Factor of Safety Xlocation COM m m m m m 0 3 0 15 0 225 0 043 0 833 0 158 0 31 0 155 0 2325 0 045 0 890 0 163 0 32 0 16 0 24 0 048 0 948 0 168 0 165 0 2475 0 052 1 008 0 173 0 17 0 255 0 055 1 070 0 179 0 175 0 2625 0 058 1 134 0 184 0 18 0 27 0 061 1 200 0 189 0 185 0 2775 0 065 1 267 0 194 0 19 0 285 0 068 1 337 0 200 0 195 0 2925 0 072 1 408 0 205 0 2 0 3 0 076 1 481 0 210
27. asonic ERJ 6ENF1001V 1 0 01 Resistance 805 Rfb2 Panasonic ERJ 6ENF1052V 1 0 01 Resistance 805 Rsense Susumu Co Ltd PRL1632 RO13 F T1 1 0 21 Resistance 1206 Rt Panasonic ERJ 6ENF6192V 1 0 01 Resistance 805 Ruv1 Panasonic ERJ 6ENF8062V 1 0 01 Resistance 805 Ruv2 Panasonic ERJ 6ENF1782V 1 0 01 Resistance 805 U1 National Semiconductor LM5118MH 1 2 8 MXA20A Voltage Monitor Circuits Voltagemonitor1 Voltagemonitor1 figure ES 2 in the charge controller section of this report is responsible for detecting the voltage input of the DC AC inverter and then indicating via an LED whether or not it is safe to use the outlet The MAX 6458 was chosen as a voltagemonitor1 because of its high supply voltage it can operate over a 4 to 28V supply voltage range The MAX6458 includes two comparators one overvoltage and one under voltage for window detection and a single output to indicate if the monitored input is within an adjustable voltage window A presentation of the application circuit of MAX 6458 is shown in figure VM 1 Vcc is the input voltage VCC X1 POTENTIOMETER R3 10 5kO Figure VM 1 Application circuit of 6458 The presentation of the equivalent circuit for MAX 6458 figure VM 2 was developed because there s no SPICE model of MAX 6458 in the Multisim 52 vcc OUT AX907CPA MAX907CPA GND Figure VM 2 Presentation of the equivalent circuit of MAX 6458 In figure VM 1 Ry R2 Ac
28. ave Cp values ranging from 0 3 to 0 45 From this information it may appear that the design point of 0 2 for BEAST was set well below these values for Cp however it was not Cp that was used as the design point but rather the efficiency of the entire generator the blades any gearing and the alternator Figure E 3 shows the systems of BEAST which will contribute to most of the power losses Cp SS p DEI E FE Rotors Savonius Chinese panamone A B American multiblade VU C Cretan sail rotor D Four bladed curved steel plate E Three bladed airfoil F Two bladed airfoil 8E 1 Figure E 2 The Cp s for various rotors as a function of the tip to speed ratio A Power to outlet Inverter Power inwind gt Blades gt nasan Alternator Wiring Charge Battery shatt Controller ON Losses due to Losses due to t d Losses due to Losses due to Losses due to Losses due to wire resistance resistance resistance resistance areodynamics friction fiction j Ly N d N system j Figure E 3 All of the subsystems shown contribute to the overall efficiency of the system 15 6 Nsystem Np Ng Na Nw Nc Nb T Table E 1 The estimated efficiencies of the subsystems of BEAST E 7 1 Ng Estimated Component p E 8
29. cation of the gearbox and generator nearer the Figure BL 2 The lift force causes a resultant B force in the direction of rotation by using speed and the wow factor of an exotic aerodynamic principles ground less noise lower start up wind design Despite those advantages the horizontal axis was chosen for BEAST because it offers more efficiency smaller Figure BLI 3 HAWT A are more efficient than overall blade size and weight and better ease of assembly and dis assembly thus VAWT B lending itself to the portable needs of the design 2 3 Number of Blades An important check for the quality and efficiency of blades are their tip to speed ratio ratio of the velocity tip of the blade to that of the incoming wind This concept is further discussed in the efficiency portion of this report In figure E 2 in the efficiency discussion the efficiency of various blade configurations was compared for varied tip to speed ratios According to that figure three bladed designs have the greatest potential for high efficiencies Two bladed designs are also rather efficient and offer the advantage of less weight and higher RPMs however they do not provide as much torque as a three blades Because of its potential for higher efficiencies and the balance it provides between torque and RPMs a three bladed design will be used for BEAST Length of the Blades The length of blades determines the total diameter of the turb
30. controller A proper charge controller design needs to take many different factors into consideration In this particular project the amount of power generated by the alternator was considered along with how this power could be manipulated to output a desirable voltage in order to charge the battery bank The charge controller utilizes several electronic components to protect the battery from overcharge and undercharge Figure ES 1 is a representation of the entire electrical system all of the subsystems will be expounded upon later in the document DCDCconverter DCtoACinverter Figure ES 1 Presentation of the entire electrical system The charge controller is composed of four primary parts a DC DC converter two voltage monitors a battery bank and the user indicators The block diagram for the whole electrical system is shown in the next page figure ES 2 Some values of the inputs and outputs in figure ES 2 are different from the overall system block diagram shown in the system design portion of this report This is due to a more refined electrical design that has been limited and driven by component availability and specifications of those specific parts First the DC DC converter handles a voltage range of 8V to 74V produced by the alternator and provides a 14V 3A output The power output from the converter then charges the battery and supplies the DC AC inverter simultaneously When the battery is fully charged the voltage moni
31. cording to page 11 of the datasheet of MAX 6458 included in the appendices the following steps were used to determine the values for R4 and 1 Choose a value for the sum of and Because the MAX6458 has a very high input impedance go as high as 5M 2 Calculate R3 based on and the desired upper trip point _ Vrus X Reotal _ VTRIPHIGH 3 Calculate R gt based and the desired lower trip point _ Vra X _ R3 VrripLow 4 Calculate based on and Ry Reotai 53 Since the MAX6458U D type was selected our threshold voltage hysteresis is 5 Therefore 1 228V VrRIPLOW 1 167V Since the input range is 11V to 14 5V set Rtota 10 0 so the 8 468KQ 10 609 0 80 923KQ A model of the application circuit was developed on a breadboard figure VM 3 yhe 5 Figure VM 3 Simulation circuit the bread board for MAX 6458 The potentiometer was replaced with a 10 resistor to produce much clearer results The real resistors were not exactly the same as the resistor values shown in figure VM 1 Howver the values were still reasonably close 81 0 R 10 680KQ R4 amp 4KQ The test results are slightly different from desired results As seen in figure VM 4 the output stays app
32. ded shaft of the alternator The hub is circular because it is a rotational hub and the blades are evenly spaced around the circle of the hub to balance the fan Fig BL 6 25 Holes Figure BL 6 Hub for Mounting Blades to Alternator The threaded shaft of the alternator is 0 875in standard thread and the hub is drilled in the center so that it fits over the shaft and is secured by a nut and lock washer To disassemble the fan the bolts that hold the blades on the hub must be removed The hub may remain attached to the alternator The hub design considers not only blade spacing but also the stress applied to the hub material as the blades spin and their inertia attempts to pull them away from the center of the hub The stress is applied to two 6mm bolts The stress applied to the material is found from Force BL 3 Stress Area where the area is the diameter of the hole multiplied by the thickness of the material The force from each blade is found from BL 4 Force mass mass w radius where w is the angular speed in rad s To find the maximum force that can be achieved the maximum rotational speed of 157 rad s 1500 rpm that the blades can withstand according to the manufacturer is used The radius of the center of mass was found from a balancing test to be 0 248m and the mass is 0 3 kg from the manufacturer This yields a force of 1834N The force on each hole is half of the total
33. e status of the project Combine the components Test system for technical specifications modify as needed Prove that the device meets specifications Describes how to use the device along with any special considerations Final report on the prototype Presentation about the prototype Constraints and specifications met Documents Engineering Notebooks Working components meet specifications documented Working components meet specifications documented Working components meet specifications documented Working components meet specifications documented Working components meet specifications documented Working component meets specifications Working components meet specifications documented Working components meet specifications documented Working components meet specifications documented Working components meet specifications documented Working components meet specifications documented Working components meet specifications documented Presentation Complete system Fully functioning prototype Monitored testing Document Document Presentation Combined presentation of prototypes Presentation S Sean J Josh M Moses Y Yixiao Jan 18 May 8 Jan 18 May 8 Jan 18 Mar 11 Jan 18 Mar 11 Jan 18 Jan 31 Feb 1 Feb 14 Jan 18 Feb 21 Feb 12 Mar 11 Jan 18 Mar 11 Jan 18 Feb 21 Jan 18 Feb 7 Feb 8 Feb 28 Feb 14 Feb 28 Mar 1 Mar 11 Mar 10 Mar 14 Apr 10 Apr 11 Apr 28 Apr 28
34. ength of blades and material was important to get the output specified Lift or Drag Wind turbine blades can be drag based figure BL 1 and catch the air thus using the direct force on the face of the blade to turn the turbine or they can be a lift based design like an airplane wing and actually create lift to pull the blades into the wind figure BL 2 A key Figure 1 1 anemometer difference in the two designs it that a drag based design cannot travel measures the wind velocity it is both a vertical axis and drag based design faster than the wind which is what allows the anemometer in figure BL 1 to measure wind speed while a lift based design can COMPARISON OF indeed allow the tip of the blade to travel faster than the wind FORCES ON BLADE itself Due to this property lift based designs are much better suited for supplying the high RPMs required for electricity generation at a high efficiency The blades in BEAST will be a lift based design because of it is lighter weight and more efficient HAWT or VAWT Incident wind Horizontal axis wind turbines HAWT in figure BL 3 A are much more common in industry than their alien looking cousins the vertical axis wind turbines VAWT in figure BL 3 B The HAWT technology is better explored and represented because it tends to be more efficient durable and lightweight However a vertical axis approach was considered because it offers several advantages including the lo
35. enough power to efficiently charge cell phone and laptop batteries The Deliverables 1 Working Wind Turbine 2 System Specifications 1 Code and electric schematics MULTISIM 2 CAD drawing 3 Testing Report 4 Users Manual 5 Final Report Principles of Operation The user will assemble the turbine onto a tripod and securely fasten it to the surroundings The blades of the windmill will capture energy from available wind and use it to turn an electric generator An energy storage device will capture the generated electricity allowing the captured energy to be used at the convenience of the user A standard United States NEMA type B AC outlet the type typically used in household applications will be attached to the energy storage device The charge amount and generation rate will be displayed to the user The user can then choose to detach the energy storage device from the turbine and use it off site or charge their device while the storage device is still attached to the turbine Input The input will be whatever wind energy is available The system will start generating given at least a 4 m s breeze and be able to handle wind gusts up to 20 m s and then stop generation in order to protect the internals of the device Output The turbine will be rated to produce at least 15 W given a 6 m s wind speed at sea level The energy storage device will contain at least 200 Wh of energy enough to charge about 3 typical laptops and an
36. f the stand and the same diameters as the uppermost section was analyzed for critical buckling load and a factor of safety of 11 was found Although the factors of safety are large a smaller diameter will not be analyzed because the wires from the alternator to the rest of the system will be run through the tubing Table SD 1 Buckling Load Calculations Buckling Load Calculations Pcr N C E N m 2 1 m44 L m Ri m FOS 1 048 04 1 6 90 10 8 933 09 0 762 0 0127 0 011 156 2 619E 03 1 4 6 90E 10 8 933E 09 0 762 0 0127 0 011 39 7 282E 03 1 6 90E 10 8 933E 09 0 914 0 0127 0 011 109 1 820E 03 1 4 6 90E 10 8 933E 09 0 914 0 0127 0 011 27 7 253E 02 1 6 90E 10 8 933E 09 2 896 0 0127 0 011 11 The upper section has a 0 0254 OD outer diameter the middle section has a 0 03175m OD and the bottom section has a 0 038m OD and all three sections have a 1 65mm wall thickness The fan alternator and furling device will be pinned to the top of the stand but will be free to rotate so that the fan can turn into the wind To steady the stand during assembly disassembly a tripod base was chosen Three legs are pinned to the lowest vertical section to help steady the device until the tethers are secured 550 is being used for the tethers It is lightweight strong able to hold up to 2 45KN durable and inexpensive per unit length and is therefore a good selection for the tethering material The Para cord does have a drawback
37. ge INdicatOr 57 DC AC Pu 58 Project Management nee Ree Eva 60 Budget Analysis deti aede t eue Ope beet dde d 61 Work Breakdown and Schedule AnallySis cccccssesscecccecessesseaeceeecssecseaeseceeecessesssaeseeeeseessessaaeess 63 Referentes 68 Appendix A Blade and HUD AANI TRA AA RN ege bx ERE e XN Appendix B Furling and Directional Appendix Stand aaa aa aaa a a an Appendix D HOUSINGS AA NAKANGITING KAINAN N Appendix E DE DE lriverter ete teer et enti eene PAANAN Appendix Voltage Monitor 1 Appendix G Voltage Monitor 2 e deret teet ette tenuate ae eee aee dr eee deae aen Appendix State of Charge Indicator All figures tables and equations will be labeled according section the below letter code Section Letter Code
38. ge at a very low RPM and was designed specifically for low wind generation It is the heaviest of the designs but its increased efficiency and quality offsets this negative attribute The DC 540 also had more manufacturer specifications available than any of the other options The efficiency output and dimension data as supplied by the manufacturer are shown in the figures A 2 through A 4 19 Model DC 540 PMA Output 8 50 80 70 60 5 2 9 4 30 20 o 65 Se i 1000 1250 1500 1750 2000 RPM Figure A 2 Outputs of the alternator from the manufacturer s specifications 0 70 49 rpm zA 117 rpm 0 60 9 M ni sat t A 209 rpm 9275 rpm 0 50 X365 rpm 0490 650 0 40 p 5 870 rpm 01160 rpm 0 30 mn o i 50 20 o 0 5 10 15 20 25 30 35 40 Electrical Resistance Setting R O Figure A 3 Efficiency of the DC 540 for different resistive values and RPMs according to the manufacturer Ll 12 24 6 16 18Th d M6 x 1mm M8 x 1 25 mm 5 16 18Th d M8 x 1 25 mm 10 15 mm Min Max E AA 1 995 2 000 ppa 72 36 mm 50 67 50 8 mm Figure A 4 Dimensions of the DC 540 Mechanical Design Blade Selection and Hub Design Blade design is a critical part of the wind turbine especially when a small blade diameter with a high output is desired Finding the right type orientation number l
39. gure ES 1 According to page 12 of the datasheet of LM 5118 included in the appendices the lowest voltage for the enable pin that can operate the DC DC converter normally is 3V Therefore the low signal sent to the LM5118 will make the DC DC converter enter shutdown mode thus drawing less than 10 pA from the Vin pin The circuit will therefore open to protect the battery Figure VM 5 Presentation of the application circuit of MAX8212 56 State of Charge Indicator It was decided that the battery status indicator should be purchased because the monetary costs to build and to purchase one were very similar and the time cost of constructing one in house was simply too great The Vexilar digital battery status indicator D 130 figure SC 1 was selected as the charge indicator because this was the only digital gauge that could be found It is desirable to give users a direct visual display of how much energy is in the battery The D 130 is a unique battery fuel gauge that recognizes both the discharge and charge cycle of your battery It senses the current charge condition of the battery and displays the percentage of remaining capacity and displays a charge trend arrow Figure SC 1 This battery gauge compares the actual voltage in the battery to the voltage at the fully charged state and displays the state of charge 57 Inverter A DC AC power inverter changes DC power 115 VAC from a battery into conventional AC
40. hosen iteratively by varying it in an Excel spreadsheet until the desired conditions were met The slope of the line between 0 and 90 degrees is k Now that the ideal conditions and goals are understood the primary design considerations are the offset chosen and the spring constant The major limiting factor is the availability of springs with low enough spring EN constants to furl quickly along with high enough tensile strength the withstand the high moment to which they subjected The spring constant k of a torsion spring from Shigley s Mechanical Engineering Design is given to be are M F 11 k df x 10 2 D Nq a LENGTH F 12 1 E 1 l Figure F 5 A torsion spring s linear constant F 13 Ng Np value is determined by many of the properties shown above where d is the diameter of spring wire E is the modulus of 33 elasticity of the spring material 10 2 is an empirical value D is the average diameter of the spring and Ng is the effective number of spring coils N is the number of turns in the spring body M is the applied moment and a is the angle of rotation from the free position figure F 5 An Excel spreadsheet was developed that calculates the k value for a spring given a varied value of The values of k were then used in another spreadsheet which calculated the values at which furling would begin and end given a specified k and preload angle A value of k that mee
41. hus the third criteria is also most likely met A summary of these results is shown in table G 2 Table 6 2 Summary of results of design points and alternator outputs Design Point Design Point Design point Alternator Rated Requirement Velocity m s RPM output RPM Output Met 4 268 12V 209 15V Yes 6 401 15W 365 46W Yes 12 803 130W 870 206 Yes From the previous discussion it is apparent that all of the design requirements are met with only the direct RPM of the generator being supplied to the alternator Gearing could still be added in order to increase the input RPM at lower velocities but due to the portable nature of this design as well as the loss in efficiency added monetary cost and time resource cost associated with adding gearing the BEAST will be a direct drive design Furling and Directional Vane Furling Mechanism This section explores the design of the furling mechanism as well as the directional vane which keeps the wind turbine facing into the wind A furling mechanism is any device which protects the turbine from exceptionally high wind speed Such a device is necessary to prevent the wind turbine from damage due to the reaction forces at the hub caused by the rotation of the blades overheating and demagnetizing the alternator and to prevent excess forces on the stand There are many different means to accomplish this with some of the most common for small wind turbines considered in table F 1 The different means
42. ieve a height which causes the blades to be at least 2 13 m 7 ft off of the ground Each section will have attachment points for tethers that can be attached to the surroundings for stability The wind turbine and all of its components will be able to be collapsed into a space no greater than 85 liters figure SO 1 and weigh no more than 23 kg During high winds the furling mechanism of the wind turbine will automatically turn it out of the 85 cm wind so that over speed of the generator does not occur Since it may be desirable to disassemble the wind turbine when the wind is blowing a hole will be placed in the tail fin allowing for a hook on a pole to be used to manually furl the turbine The turbine will be a complete assembly 35 me Figure SO 1 An Osprey Argon 85 L hiking backpack will be able to hold BEAST It is rated to hold up to 30 kg comfortably of the turbine blades stand tethers battery 38 pack and circuitry System Block Diagram Stand b Feming EE 0 1000 Alternator Wind _ Controller 0 15 V LL 0 A 72 0 OG Outlet Power DC power On Off DC power Batte DC power Charge 115 V AC 0 1 74A Inverter 0 12 V 0 20 A Switch 0 12 V 0 20 A y 13 5 18 V 0 3 0A Controller
43. ine and thus the swept ares which in turn determines the total amount of power that can be extracted from the wind equation BL 1 More information on the development of eq BL 1 is available in the efficiency section of this document 1 BL 1 P 5 p 3 BL 2 Output enerator 1 generator 2 S Vi where C is the efficiency of the blades p is the density of air in kg m S is the area swept by the turbine blades m V is the velocity of the wind in m s and generator 5 the efficiency of the generator as outlined in the efficiency discussion The requirement specifications were estimated by using a total blade diameter of 1 m which seemed to be reasonable for a portable design and the k efficiency of generator to a conservative 20 and p to 1 2 E the density of air at sea level It can therefore be reasoned that if the blades are 1 m or slightly greater in diameter than the power output ought to meet the requirements without being too heavy Material Ideal materials for turbine blades are lightweight strong durable and easily shaped to specific profiles Historically blades have been made out of wood thin strips of aluminum fiberglass and plastic composites It was determined that the best material for BEAST would either be fiberglass or a plastic composite due to their especially lightweight designs that typically involve efficient profiles due to their mold ability Blades Selected Designi
44. inverter will be used to supply 125 VAC 60Hz through a NEMA Type B outlet Technical Requirements 1 Power Generation The generator should produce at least 15 W given a 6 m s wind typical ground level wind speed and 130 W at 12 m s the typical wind speed used to rate wind turbines 2 Energy Storage At least 200 Wh will be stored in a durable and safe energy storage device This will provide enough energy to charge 3 typical 6 cell laptop batteries The storage device will be detachable and portable for use away from the turbine 3 Electrical Safety When the storage device is full electricity will cease being supplied to the storage device All wires and circuitry will be able to handle the maximum amount of current produced by the turbine 4 Mechanical Safety The mechanical parts will be stable and able to withstand the high shear and bending stresses placed upon them A housing will cover the gearing and the turbine in order to protect the user The lowest point at which the blades spin will be at least 2 13 m off of the ground 5 Portability The turbine and all of its components should fit within a large backpacking backpack 85 liter and weigh less than 23 kg It should be easily assembled within an hour after one practice trial by two individuals who have read the user manual using only basic tools screwdriver wrench etc 6 Durability The system will be able to withstand frequent assembly and dis assembly and still be opera
45. irection of wind flow although at a slower rate than if they were perpendicular to the flow However it does convey the theory behind this mode of protection The calculations involved for furling require an even further understanding of the mass balance across the blades than previously discussed The first element that must be discussed is the value of the axial force acting on the blades as the wind passes through them F 3 2 5 V 05 where is the axial force is the mass of the air is the acceleration of the air is the time rate of change of the mass of air V is the velocity of the air p is the air density S is the swept area of the blades V4is the velocity of the air entering the blades and is the velocity of the air leaving the blades If the average is velocity of the air is assumed to be 1 F 4 Vovg 2 V5 Then substituting eq F 4 into eq F 3 produces F 5 5 2 If np is the efficiency of the blades as described in the efficiency discussion it can be shown that 31 F 6 V 1 Then finally from 5 and eq F 6 the axial force is F 7 F 2 D n V However it ought to be noted that eq 7 is not entirely accurate for a furled state due to the decreased area From figure F 2 and eq F 7 it is apparent that a more accurate equation is given by p F 8 Frurted Aes fective 2
46. irectional vane keeps the wind turbine turned in the direction of the wind by placing a larger amount of area parallel to the flow of the wind in the back of the vane than in the front For the purposes of BEAST it is desirable to construct the vane out of lightweight and durable material with coupled with a short arm length and an aerodynamic design The means in which the fin is actually used to turn the turbine can be seen in figure F 8 if a gust of wind is comes from a new direction a moment is created at the fin that must be greater than the moment at the blades in order for alignment to occur Fein gt Larm Fblades Figure F 8 The moment created by the force on the wind must be more than that created by the blades in order for alignment to occur 36 Recall F 14 Fhiades 2 Aptades P V also the force of the wind acting on the fin is given by F 15 Frin p where is the drag coefficient for that specific geometry Now the moments around the stand by the blades and the fin are given to be 1 F 16 Foiades 5 P V Nin O and Table F 5 The drag i coefficient of the shape 2 me M MEE oe If F 16 and F 17 are compared to each other and solved for the area of the fin then eq F 18 results Ablades Nth O F 18 Afin gt T Before the area is calculated it is wise to determine the shape of the tail fin The sh
47. is 15 24cm x 19 05cm x 34 29cm to accommodate the inverter circuit boards and battery packs Fig H 1 The housing will have a water resistant AC outlet in one end for the user to connect to and a hookup in the other end to attach to the output from the alternator The outlet will be connected to the inverter by a short electrical cord The top of the housing will be removable for access to the components The charge rate and availability indicators will be mounted into the top of the housing for ease of viewing The size of the housing is determined by the size of the individual components They are arranged to achieve the smallest housing size possible AC OUTLET CIRCUIT Figure H 1 Water Resistant Housing Layout The housing will be made of acrylic sheet because it is strong per unit volume easily cut and drilled inexpensive and impervious to water The decision matrix for material selection is shown in Table H 1 Table H 1 Decision Matrix for Material Selection Housing Material Selection Criteria Weight Acrylic Sheet Aluminum Wood Weight of Material 0 2 3 2 2 Price 0 25 3 1 3 Easily Assembled 0 05 1 2 3 Sealability 0 25 2 2 1 Water Resistance 0 25 3 3 0 1 12 10 9 Weighted Total 2 65 2 1 55 Electrical Design Electrical System Overview The purpose of this section is to outline the overall workings of the electrical system The electrical system is essentially a charge
48. le E 2 on the following page was generated using equations E 1 E 4 where Cp Cpgax E 10 and E 11 the results were also plotted as shown in figure E 4 When table 2 is consulted it becomes apparent that the requirements outlined are indeed met both by the generator and by the overall system 16 Table E 2 The outputs of BEAST are compared to the power in the wind and an ideal turbine The requirements for output should be exceeded Power Produced Power Produced Power Output to Wind Velocity Power Available Ideal Cp 593 Turbine BEAST s Generator BEAST s Outlet m s watts watts watts watts 1 1 2 0 7 0 2 0 1 2 9 3 5 5 1 9 0 9 3 31 4 18 6 6 3 3 0 4 74 3 44 1 14 9 7 1 5 145 2 86 1 29 1 13 8 6 250 9 148 8 50 3 23 8 7 398 4 236 3 79 9 37 8 8 594 7 352 7 119 3 56 5 9 846 8 502 1 169 9 80 4 10 1161 6 688 8 233 1 110 3 11 1546 0 916 8 310 2 146 9 12 2007 2 1190 3 402 7 190 7 13 2551 9 1513 3 512 0 242 4 14 3187 3 1890 1 639 5 302 8 15 3920 3 2324 7 786 6 372 4 Power Available Power Produced by and Ideal 593 Turbine Power Produced by 5 Generator Power Output to BEAST s Outlet 4000 3500 4 3000 7 2500 4 4 gt gt o 2000 4 7 8 j 1500 4 7 7 z 1000 m od Pd AR 500 4 a ae ET EE 0 4 T 0 2 4 6 8 10 12 14 Wind Velocity m s Figure E 4 Recall that
49. n of the overall system efficiency and limits the amount of power that can actually be generated by the system The ideal alternator meets several criterions 1 Rated to produce high voltage at low RPM allows for power generation at lower wind speeds 2 Brushless Less friction means less losses 3 Produces direct current DC Allows for battery charging without power inversion Figure A 1 The DC 540 Low Wind Permanent Magnet Many different options were considered including using old Alternator was chosen for its efficiency and quality of DC motors and reversing them but eventually the field was SUNA narrowed down to four options as shown in the table below Table A 1 The DC 540 suits BEAST better than any other alternators that were researched Alternator Attribute Summary Anaheim Manufacturer Ametec Windblue Power Windstream Power Automation DC 540 Low Wind Permanent 443541 Permanent Magnet Magnet Alternator DC Generator Brushless Y Yes No RPM 0 1000 3000 4200 0 2000 0 5000 Criteria Ametec 30 BLY343S 30 No ES Voltage 30 30 0 200 Weight Ib 8 5 7 11 9 2 Price 120 00 217 50 250 00 250 00 Torque 1 386 3 Phase optional Designed for Extras Must buy used direct drive wind generation reaches 12V at 150 RPM The DC 540 low wind permanent magnet alternator figure A 1 was selected because it had top of the line quality a built in rectifier a brushless design reached charging volta
50. nator as well as the design switch to NIMH which were over 100 more expensive then the originally planned lead acid batteries Overall BEAST is still well within budget with plenty of contingency funds should the need arise Overall Budget Table The budget is further broken down on the following pages into mechanical and electrical components It is obvious that the mechanical budget is nearly twice as much as the electrical budget this is primarily due to the inclusion of the alternator in the mechanical budget The contingency funds should absorb any small items that may have been overlooked such as paints bolts and wires Also many of the important items have already been ordered and some such as the blades and the alternator have been in for over a month This provides another indication that the design has made good progress Overall Budget Budgeted Spent 96 Spent Mechanical 5533 48 5441 76 83 Electrical 261 93 205 94 7996 Total 795 41 647 70 8196 Funds 1 000 00 1 000 00 Contingency 204 59 352 30 Mechanical Budget Description Quantity Price per unit Price Total Vendor Further Details Shipping Ordered Received Spent Alternator 1 262 17 5262 17 www WindBlue com Included Y Y 262 17 Blades 3 pcs 1 85 99 85 99 www greenergystar com Free Y Y 85 99 Stand Base Tubing 3 10 76 32 28 www metalsdepot com 0 065 int 1in OD 50 00 32 28 Hub 1 14 62 1
51. ng a complex lightweight blade profile in house would involve computation fluid dynamics beyond the scope of this design and constructing one would be difficult at best Therefore it was decided to purchase the blades A search for turbine blades that met the one meter diameter specification was conducted Only two blades that had a diameter near to 1 m could be found The blades that were eventually selected shown in figure BL 4 were less expensive and also slightly larger than the others a comparison of the two blades was actually found the site where the blades were purchased greenergystar com and is available in the appendices Figure BL 4 The blades selected are molded out of a strong and lightweight nylon carbon fiber composite to exacting specifications The selected blades have a 1 57m diameter when mounted on a 0 101m diameter hub and the total weight of the three blades is 0 9 kg due to the nylon carbon fiber construction The material does bend easily and therefore is designed such that the mounting surface causes the blade to be angled towards the direction of the wind when mounted Fig BL 1 When in operation the force of the wind on the blades causes them to bend back away from the wind and become parallel to the mounting hub b4 4 Wind Horizontal Line Figure BL 5 Forward angled mounting of airfoil blades The hub that holds the blades is designed based on the number of blades and the diameter of the threa
52. orce mechanism is lightweight accurate and precise and Figure F 1 Unfurled wind turbine viewed along the axis would be ideal for a larger budget on a final of the stand from the top commercial unit 30 Due to its relatively simple lightweight and 3 Tail Vane inexpensive design spring furling was chosen as the method of furling This method of furling involves offsetting the alternator and blades a small amount Offset 0 lt gt from the tail vane and the central axis of the stand thus creating a moment caused by the axial force on the blades A torsion spring is then set to resist this moment by preloading the spring to a calculated force given a specified wind velocity When that velocity is reached the wind force will overcome that preload and start to Diameter D turn the blades out of the wind thus reducing their swept area relative to the wind and therefore the available power figures F 1 and F 2 From eq E 1 Deffective D cos 8 2 1 x pV 3 gt 3 p F 2 Pef fective cos V From eq F 2 it appears that the power available would Figure F 2 The turbine as furled an angle of due to even become 0 when the system is fully furled high wind force thus reducing the effective area 0 90 This 15 not entirely accurate because the blades do continue to spin even when they are completely parallel to the d
53. relative humidity increases by less than 2096 relative humidity it passes the test 6 The indicators will be tested before final installation by measuring known values using them A multimeter will be used to verify the outlet s output while a laptop and a cell phone are being charged individually System Design System Overview The finished wind turbine will deliver electricity to a NEMA Type B outlet standard in U S homes by converting wind energy into mechanical rotational energy and then converting that mechanical energy into electrical energy The wind energy will be captured by blades that are attached to a hub that is free to rotate The hub will be elevated on a stand such that the lowest point that the blades spin will be at least 2 13m above the ground The rotation of the hub will turn the shaft of an electricity generator and thus convert wind energy into electricity The produced electricity will then be stored in a battery and the battery will supply electricity to an outlet via an inverter An indicator will tell the user how much power is being produced instantaneously and how much power is available in the battery The battery pack will also be removable for transportation or use away from the turbine For the wind turbine to be used the blades must be attached to the hub and the hub must be attached to the top of a collapsible stand The stand will have sections that are approximately 1m in length and when fastened together ach
54. roximately OV when the input is under 11 5V or above 14 7V According to figure ES 2 when the 54 output of voltagemonitor1 is approximately OV the red LED will turn ON When the input is between 11 5V and 14 7V the output is approximately equal to the input At this time the green LED will turn ON Voltage Input vs Voltage Output for MAX6458 16 14 12 10 Output V Sm 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Input V Figure VM 4 Voltage Input VS Voltage output for MAX 6458 Voltagemonitor2 In order to protect the batteries from overcharge damage as well as charging at very low voltage from the alternator a protection circuit is required The MAX 8212 was chosen as the main component for voltagemonitor2 figure ES 1 because of its simple application circuit and low cost According to page 5 of the datasheet of MAX 8212 included in the appendices resistor values for figure VM 5 were calculated as follows 1 Choose a value for R1 Typical values are in the 10 to 10 range 2 CalculateR Vi 1 15V E Vi VrH _ R gt Rj TIT 55 3 CalculateR Vy Vi 1 15V Set Rj 15 24 13KQ 150 0 Theoretically Max 8212 will give a low signal at the output when the battery is fully charged The output of the Max8212 is connected to the enable pin of the LM 5118 figure VM 5 fi
55. rstand the design point for BEAST and its relation to other wind turbine designs it is important to understand the total amount of power available in the wind as well the means in y which that energy is captured by the turbine Vous y 2 The overall power available in the wind can be derived from a mass balance over the surface of the Figure E 1 Mass balance across a wind turbine s blades blades figure E 1 The result is shown in eq E 1 E 1 Power available in wind 5 S V3 where p is the density of the air S is the swept area of the blades and V is the incoming wind speed velocity However no turbine can capture all of the energy from the wind in fact Albert Betz a German physicist in the early 20 century derived the limit for wind turbine energy capture Betz s limit describes the maximum coefficient of performance of wind turbines E 2 Cp Power Captured Power Available in Wind E 3 CPmax 293 Therefore a corrected form of eq E 1 would be E 4 Power S V3 Figure E 2 describes the coefficient of performance for differing tip to speed ratios E 5 Tip to Speed Ratio w d where o is the angular velocity of the rotor r is the radius and v is the velocity of the wind It can be inferred from figure E 2 that the Cp of wind turbines decreases when additional blades are added and that the most efficient designs tend to use three blades In fact most well designed large commercial turbines h
56. t were eventually taken out of the design such as the gears are left in the fall WBS because of the design work that went into justifying their removal However the spring WBS has been modified to remove those items because they should play no part in the actual construction of the prototype The design is on track according to the schedule developed earlier in the design process The original Gantt chart for the fall has been modified to show which segments have been completed The higher level blocks have not been shown as completed because even though the individual subcomponents have been designed some of their integration design is still ongoing Overall the design schedule was quite useful and was held to reasonably well In fact there were time when the team felt as if it was behind schedule do to impending deadlines but when the Gantt chart was referenced it showed that all was as it should be the deadlines simply made it more real The spring schedule has undergone a few changes and is also attached The schedule was actually made easier by removing the shaft and gear build as well as the mechanical housing Work Breakdown Structure Fall 2010 F1 00 Project Management F2 00 Documentation F3 00 Project Selection F4 00 Project Specification F5 00 System Design Report System Design and F6 00 Project Plan Formal Presentation F7 00 Component Design F7 10 F7 11 F7 12 F7 13 F7 14 F7 15 F7 16 F7 20
57. the power generated is a cubic function of wind velocity Weight Budget Due to the portable nature of this project it was deemed important to keep track of the total amount of weight contributed by the various subsystems as shown below From the weight budget summary it is evident that the design of BEAST is still well under the design point of 23 Kg of total mass By far the heaviest items in the list are the alternator the battery and the stand as a whole however increased weight in those areas is justified by the increased efficiencies associated with their quality craftsmanship Weight Budget Description Quantity Weight per unit Ibs Total Weight Ibs Further Details Total Weight kg Alternator 1 11 11 4 99 Blades 3 pcs 1 2 2 0 91 Housing Electronics 1 1 63 1 63 0 74 Hub 1 0 7 0 7 1 41 6 D 0 32 Stand Base Tubing 3 1 62 4 86 0 73 Stand Pins 6 0 025 0 15 0 01 Stand Tethers 1 1 5 1 5 0 68 Stand Tubing Bottom 1 2 46 2 46 1 12 Stand Tubing Middle 1 2 04 2 04 0 93 Stand Tubing Top 1 1 62 1 62 0 73 Tail Rod Aluminum 1 1 62 1 62 0 73 Tail Spade Plexiglas 1 0 41 0 41 0 19 Battery 2 3 35 6 7 1 52 Inverter 1 0 85 0 85 0 39 Approximate Total Weight 37 54 13 98 Contingency 12 46 9 02 Alternator Selection The alternator was the most pivotal of all of the E E components to select it forms the link between the electrical and mechanical systems dictates a large portio
58. though because it is thin it elongates up to thirty percent at maximum load This is potentially a problem because the stand needs to be as rigid as possible but the maximum forces expected should not cause enough elongation of the Para cord to be a problem Other tether materials were considered but no other materials provided the same strength to weight ratio as the Para cord Figure SD 1 Fully Extended Stand Figure SD 2 Collapsed Stand Housings Upper Housing The requirements specification dictates that a protective housing will enclose the gears and alternator that are mounted on the top of the vertical stand The housing was intended to protect the user from the gears and vice versa The selected alternator however does not require the use of gearing and therefore no gears are being implemented which removes the safety issue of exposed gears The selected alternator is also an all weather design and therefore the upper housing is no longer part of the design Electronics Housing The charging circuit and battery pack need to be kept in a water resistant enclosure to protect the components of the system It is also desirable to be able to remove the battery pack from the turbine to use off site Having all of the electronics contained will allow for this to be easy and efficient The housing is water resistant and durable enough to handle the weight of all the components as well as the movement from location to location It
59. tional The electrical components will be contained in a water resistant housing 7 User Interface The rate at which the energy is being produced and the amount of charge available empty to full in the energy storage device will be indicated A 125 VAC 60Hz NEMA Type B outlet will connect devices to the storage device Testing Plan 1 The wind tunnel in the Ulrey will be used to supply a 6 m s 12 m s and 20 m s wind speed to the turbine The current and voltage going into the battery will be measured at each of those speeds 2 The battery will be fully charged and then drained with a run time test 3 The wind speed will be increased to 20 m s to check for mechanical stability of the blades and hub A force that simulates the maximum force applied under peak operating conditions will be manually applied at the hub while the stand is fully assembled and anchored in order to check for the stability of the stand 4 Theentire device will be weighed disassembled and placed in a backpack Three separate groups of two volunteers will assemble the device with any necessary tools supplied The average of the completion times of the second attempts must be one hour or less 5 The device will be assembled and dis assembled several times to check for durability The water resistant electronics housing will tested while empty by measuring the relative humidity inside then spraying it with water and then measuring the relative humidity again If the
60. tor for the battery voltagemonitor2 outputs a low signal less than 0 5 V to the enable pin of the DC DC converter to open the circuit The enable pin must be raised above 3V for normal operation If the enable pin is pulled below 0 5V the DC DC converter enters shutdown mode drawing less than 10 pA from the Vin pin Then the battery bank continues to supply the DC AC inverter When the battery bank s voltage falls below the appropriate range the voltage monitor voltagemonitor2 will send a 45 high signal to the enable pin of the DC DC converter to close the circuit again and resume charging the battery bank The state of charge indicator displays the amount of charge in the battery Voltage monitor1 detects the voltage input for the DC AC inverter If the input is in the appropriate range the green LED will turn ON otherwise the red LED will turn ON LED indicator Oor11 14 5V Alternator 0 500 mA Voltage 0 5A 4A 8V 74V monitor1 DC DC aaa DC AC inverter converter M 14 5V lt 3V when 14V battery is fully 0 3A 0 charged VO OB Qum d monitor2 bank 0 12V 0 1A Figure ES 2 Block diagram of electrical system Battery Selection The requirements specified at least 200 Wh of energy storage to be available in the battery There are several different types of batteries available on the market that could meet those requirements The properties of the battery types are summarized in table B
61. ts the criterion for furling between two specified values was not difficult to find however the spring material itself can only withstand a certain range of moments table F 2 Unfortunately the actual moments acting on the spring are quite large even for a small offset table F 3 Table F 3 The moment acting on the spring varies with the square of the Table F 2 The diameter of the spring material wind velocity determines the maximum moment that the spring can withstand Values for maximum moment were V M obtained from McMaster s website m s Ibf in N m 1 1 1 Moment Ibf in N m 0 135 3 429 42 86 4 842537 3 28 66757 3 239001 4 33 2476 3 756475 5 9 0 125 3 175 34 29 3 874256 0 106 2 6924 22 5 2 542163 0 095 2 413 17 14 1 936563 The balance between a quick furl and the actually being able to withstand the moments applied 0 1 2 38 16689 4 312279 16 43 42544 4 906416 7 8 0 calls for a low value of k coupled with a large wire diameter d and E Given large wire diameter the only way to vary the value of k is to vary the values of D and N4 Using the Excel spreadsheets mentioned above it was determined that for d 3 175 D 44 45 mm and Na 48 an Table F 4 Summary of the designed spring characteristics N mm IS l acceptable value of k 14 93 mer Spring Characteristics found to furl up to 60 between 12 5 and 14 2 Material Music Wire m s given a
62. ual components and build the circuit in house Figure DC 1 shows the application circuit of the DC DC converter for BEAST the components in the circuit that are going to be purchased displayed in table DC 2 A PL A8 Figure DC 1 DC DC converter 50 Table DC 2 Electrical BOM list Part Manufacturer Part Number Quantity Price Attribute 1 Name Footprint Cboot MuRata GRM219R71C104KA01D 1 0 01 Cap 805 Yageo America CCO805KRX7R9BB152 1 0 01 Cap 805 Ccomp2 MuRata GRM219R71H333KA01D 1 0 01 Cap 805 Cin MuRata GRM32ER72A225KA35L 5 0 49 Cap 1210 Cinx Taiyo Yuden HMK212B7104KG T 1 0 0271 Cap 805 Cout Sanyo 20SVP100M 5 0 Cap SM_RADIAL_8MM Cramp Yageo America CCO805KRX7R9BB152 1 0 01 Cap 805 Css Yageo America CCO805KRX7R9BB183 1 0 01 Cap 805 Cvcc Taiyo Yuden LMK212B7105KD T 1 0 017 Cap 805 Cvccx Kemet C0805C105K4RACTU 1 0 02 Cap 805 D1 Vishay Semiconductor 30CTHO2SPbF 1 O VFatlo DDPAK D2 Vishay Semiconductor 12CWQO3FNPBF 1 0 74 VFatlo DPAK D3 Vishay Semiconductor 30CTHO2SPbF 1 O VFatlo DDPAK 04 Vishay Semiconductor 12CWQO3FNPBF 1 0 74 VFatlo DPAK L1 Bourns PM2120 270K RC 1 AP E PM2120 M1 Infineon Technologies BSC100N10NSF G 1 1 48 VdsMax PG TDSON 8 M2 Renesas RJKO330DPB 1 0 69 VdsMax LFPAK Rcomp Panasonic ERJ 6ENF1782V 1 0 01 Resistance 805 Renable Panasonic ERJ 6ENF1004V 1 0 01 Resistance 805 Rfb1 Pan

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