1. SPANDEX FRR

2. Mission Goal We aim to measure solar panel efficiency as a function of altitude. We would like to determine if the lower temperature and thinner air of the upper atmosphere have an effect on the efficiency and power output of a PV cell. Science Objectives We seek to determine the efficiency of the solar cell, discover what effect varying temperatures have on the efficiency, and to discover if the Sun’s radiation in the upper atmosphere has a different effect from the radiation in the lower atmosphere. Technical Objectives We will construct a well-insulated box, voltmeter, and MPP (maximum power point) tracker. We also want to keep the payload level at all times.

3. Background and Requirements

5. P out = V^2 / R Efficiency = P out / P in Area of cell = 106.25 cm^2 The solar cell data sheet claims that the cell should put out 1.55 watts at 25 degrees Celsius with an irradiance of 1000 W/m^2 shining directly on it We expect a max of 1.84 W at -60 degrees Celsius with the sun at 21 degrees from its normal with an irradiance measurement of 1000 W/m^2. We expect a min of 0.08 W at 80 degrees Celsius with an irradiance measurement of 625 W/m2 with the sun at 64.8 degrees from the normal on a cloudy day.

6. Mechanical Structure

8. Electronics

9. Flight Software

10. Ground Software

11. Thermistors

12. Testing

13. Results

20. Analysis Error for the power: 8.5% Based on the cell’s spectral response, we predicted that the ratio of efficiency below the clouds to efficiency beneath the clouds would be 4/5. We found that the actual ratio of average efficiencies is 6.997 to 7.793 (11 % difference).

21. Conclusion The max efficiency was 11.1 % and occurred at 11.12215 km Because this max occurred near the tropopause where both the external and operating temperatures reached a min, and because we found no correlation between power in and efficiency, we conclude that efficiency increases as temperature decreases, but not necessarily as irradiance increases We could improve our experiment by using solar panels that produce higher voltages and by attaching our own pyranometer to our payload instead of relying on outside data

22. Special Thanks Instructors Dr. Greg Guzik Mr. Brad Ellison Mr. Jim Giammanco Dr. John Wefel Absent Teammates Joe Thompson Bob Thompson Other Help Thomas Stoffel (NREL) CSBF Jeff the engineer