Small-Scale Solar Power Solar Power Rangers

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

Our Approach Collection Conversion Storage

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

Final Product

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

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

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

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

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

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

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

Stirling Engine: Virtual Model

Stirling Engine: Operation

Stirling Engine: Virtual Demonstration

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

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

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

.0044 kg 9 rpm

S = L

L = 12 in D = 5 in

r 2 = 6 in r 3 = 8 in

Stirling Engine: Final Design

Prototype

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

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

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

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 Cloudy AprilClear AprilClear Average

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

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

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