Design and development of a 300-watt solar photovoltaic concentrator. Final report, May 17, 1976--November 30, 1977
The design, fabrication and performance of high level concentration (300X) with refractive lenses on small silicon solar cells approx. (0.4 cm/sup 2/) with passive cooling are described. Four systems were fabricated using polar axis (2-axis) tracking. Two systems were rated at 100 W peak, and two were rated at 300 W peak. The maximum power measured on the 300-W unit was 236 W at 93 mW/cm/sup 2/ direct insolation. Solar cells were designed and fabricated using bulk high resistivity n-type silicon which showed a maximum efficiency of 17.5% independent of concentration level from 50 to 400X. At 1000X, the efficiency dropped to 14%. Lens arrays made from vacuum formed shells and epoxy filled showed good performance on a selected basis but nonuniformity and uv degradation dictated a change to Fresnel lenses. The Fresnel lens arrays are approximately 83% efficient but the imaging was quite nonuniform causing degradation in cell fill factor and collection efficiency. Heat transfer calculations and simulations show that the cell temperature is about 25 to 35/sup 0/C above ambient temperature. Thermal spreading of the heat from the cell area to an area equivalent to the lens area is the most important function of the heat sink. The addition of fins do not significantly reduce cell operating temperature. An optimization analysis was performed on passively cooled photovoltaic concentrators showing the various tradeoffs that exist with lens size and concentration level. The conclusions are that minimum manufacturing costs of $0.70/peak watt can be obtained at an optimum lens size of approximately 100 cm/sup 2/ and concentration level of 100 suns. Deviation from this optimum either degrades performance, increases cost, or both.
- Research Organization:
- RCA Labs., Princeton, NJ (USA)
- DOE Contract Number:
- EY-76-C-04-0789
- OSTI ID:
- 6081466
- Report Number(s):
- SAND-78-7027
- Country of Publication:
- United States
- Language:
- English
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