A solar cavity-receiver packed with an array of thermoelectric converter modules

We report on the design of a solar cavity-receiver packed with an array of thermoelectric converter (TEC) modules, which enables efficient capture of concentrated solar radiation entering through a small aperture. A 1 kW demonstrator (proof-of-concept) containing 18 TEC modules, each consisting of Al2O3 absorber/cooler plates, and p-type La1.98Sr0.02CuO4 and n-type CaMn0.98Nb0.02O3 thermo-elements, was subjected to peak solar concentration ratios exceeding 600 suns over its aperture. The TEC modules were operated at 900 K on the hot side and 300 K on the cold side. The measured solar-to-electrical energy conversion efficiency was twice that of a directly irradiated TEC module. A heat transfer model was formulated to simulate the solar cavity-receiver system and experimentally validated in terms of open-circuit voltages measured as a function of the mean solar concentration ratio. Vis-a-vis a directly irradiated TEC module, the cavity configuration enabled a reduction of the re-radiation losses from 60% to 4% of the solar radiative power input. Theoretical considerations for TEC with figure-of-merit higher than I indicate the potential of reaching solar-to-electrical energy conversion efficiencies exceeding 11%. (C) 2011 Elsevier Ltd. All rights reserved.