Flat Plate Thermoelectric Solar Cells: Manufacturing Process and Life Testing

The theory, fabrication, and performance of Bi2Te3 alloy-based flat plate thermoelectric generator for near-earth orbits have been previously described.1 A power output of 3. 1 watts/ft2 to a matched load at a solar flux of 130 watts/ft2 and 30 watts/lb at the unit cell stage is achieved. This paper presents changes in process and manufacturing procedures suitable for a production rate of 25 unit solar cells per day and providing considerably longer lifetime. The cells are to be used for the fabrication of panels of 6 ft2 area. Previous results of cyclic life test have shown a lifetime up to 2000 cycles, approximately simulating the conditions of an earth orbit. The process changes described enable a lifetime of 20,000 cycles as indicated by less than 10% degradation in ac resistance and a decrease in power output of 20%. In order to achieve accelerated life testing, a cycle time of 10 minutes was used. The absorber plate was maintained at 250°C for 7 minutes with 1 minute being used to change from 72°C and 2 minutes to cool to 72°C. The radiator plate was maintained at approximately 73°C. These conditions simulate very severe flat plate operating conditions.