1. Small-Scale Solar Power Solar Power Rangers

2. Project Definition Small Scale, non-photovoltaic, 20 Watts at 20 V continuous. Small Scale, non-photovoltaic, 20 Watts at 20 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 – –Why? – –End-plates – –Reflecting Material – –Heat Transfer Mechanism

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

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

9. Reflective Film 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

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

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

12. Stirling Engine: Rationale External Combustion External Combustion –Good with solar Working fluid is air Working fluid is air –No phase change required –Effective over wide range of energy inputs

13. Stirling Engine: Virtual Model

14. Stirling Engine: Operation

15. Stirling Engine: Virtual Demonstration

16. Stirling Engine: Trade Studies Heat Sink Heat Sink –Number of fins N and thickness t

17. Stirling Engine: Trade Studies Cylinder Cylinder –Dimensions D, L, S –Air mass m and engine speed in rpm

18. Stirling Engine: Trade Studies Heat Sink Heat Sink –Number of fins N and thickness t Cylinder Cylinder –Dimensions D, L, S –Air mass m and engine speed in rpm Links and Flywheel Links and Flywheel –Link lengths r 2, r 3 –Mass m of flywheel

19. .0044 kg 9 rpm

20. S = 0.833 L

21. L = 12 in D = 5 in

22. r 2 = 6 in r 3 = 8 in

23. Stirling Engine: Final Design

24. Prototype

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

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

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

28. 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

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

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

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