1. Small-Scale Solar Power Solar Power Rangers

2. Project Definition Small Scale, non-photovoltaic, 20 Watts at 12 V continuous. Small Scale, non-photovoltaic, 20 Watts at 12 V continuous. Competition: Photovoltaic Competition: Photovoltaic Applications: 3 rd world countries, disaster relief Applications: 3 rd world countries, disaster relief

3. Our Approach Collection Conversion Storage

4. Design vs Prototype Design for the final product Design for the final product Prototype key components of the design to assess concept feasibility Prototype key components of the design to assess concept feasibility Final Result: two distinct products Final Result: two distinct products

5. Final Product

6. Parabolic Trough Features Features –Why? –End-plates –Reflecting Material –Heat Transfer Mechanism

7. Why a Trough? Trough Trough –Mature technology –Ease of construction –ONE degree of freedom/tracking Set once per day according to date and global position Set once per day according to date and global position Dish Dish –Relatively young technology –More difficulty in physical realization –TWO degrees of freedom/tracking

8. End-plates Features Features –Parabolic –Open-ended

9. Alignment

10. Reflective Film Southwall/ReflecTech Southwall/ReflecTech – Southwall film is enhanced with environmental inhibitors to protect the silver from oxidation and PSA for easy application –Nominal reflectance = 94% *Courtesy Southwall Technologies

11. Evacuated Glass Solar Tube Apricus Tubes Apricus Tubes –Dewar’s flask configuration –Al-N/Al coating –Absorptance > 92% –Non-wicking heat pipe 30° Elevation

12. Trough Recap Provides heat focusing method Provides heat focusing method Utilizes developed and proprietary products Utilizes developed and proprietary products Nominal efficiency expectancy Nominal efficiency expectancy –94% reflectance x 92% absorptance = 86.5% efficient –Results of tests in conclusion

13. Stirling Engine: Rationale No phase change required No phase change required Effective over wide range of energy inputs Effective over wide range of energy inputs

14. Stirling Engine: Virtual Model

15. Stirling Engine: Virtual Demonstration

16. Stirling Cycle Assuming Q in = 267 W, achieve W out = 67 W –This means 40 W electrical Minimize  T across heat sink –Proper choice of fin dimensions Maximize power delivered to flywheel –Proper sizing of linkages Maximize efficiency of cycle –Appropriate engine sizing T∞T∞ TbTb

17. Heat Sink Number of fins N Number of fins N and thickness t Expected  T = 13 o C Expected  T = 13 o C

18. Cylinder Dimensions D, L, S Dimensions D, L, S

19. S = 0.833 L

20. L = 12 in D = 5 in

21. Links Link lengths r 2, r 3 Link lengths r 2, r 3 r 2 = 6 in r 3 = 8 in T avg = 65.2 N-m,  = 9rpm P = 61.4 W

22. Stirling Engine: Feasibility Nominal Case Nominal Case –  = 26% –Qin = 267 W >> Wout = 69.5 W

23. Prototype

24. Calorimeter Measures thermal power output Measures thermal power output Ideal calorimeter has zero heat loss Ideal calorimeter has zero heat loss –Insulated thermos with lid Convection inside calorimeter Convection inside calorimeter –Measure T after stirring water

25. Stirling Engine Bought versus build yourself Bought versus build yourself Engine Issues Engine Issues –Tolerances –Seals –Thermal Expansion

26. Embedded Intelligence Logic Engine Rotating? ΔT ≥ 20 °C Light LED

27. Lessons Learned Solar Collection Test Results Solar Collection Test Results Desired Power ≥ 175 W/m 2 Desired Power ≥ 175 W/m 2 Average efficiency of 78% Average efficiency of 78% Trough vs. Dish, revisited Trough vs. Dish, revisited DateConditionsPower (W)Power per Area (W/m 2 ) 11 AprilPartly Cloudy48.16147.24 14 AprilClear62.67191.60 14 AprilClear60.81185.91 Average57.21174.91

28. Lessons Learned, cont. Engine configuration Engine configuration –Binding due to moments –Alternatives? Image from Wikipedia Rhombic Drive Basic Crank-Slider

29. Conclusions Feasible Feasible –Will be able to meet power requirements Continuing Development Continuing Development Not competitive for small scale applications Not competitive for small scale applications –High manufacturing cost –System placement –System complexity

30. Questions The Solar Power Rangers are: Phillip Hicks, Kevin Kastenholz, Derek Lipp, Paul Nistler, and Rachel Paietta and Rachel Paietta