Thermoradiative induced absorber-emitter to enhance solar thermoelectric conversion

Abstract

Solar thermoelectric power, is promising for use in small-scale CSP system due to its flexible architecture and silent operation. However, the conversion performance of standalone solar thermoelectrics is still far from ideal at lower concentration ratio. This paper tends to introduce a self-powered thermoradiative absorber-emitter at the top to enhance the overall solar thermoelectric power generation. Thermodynamic model based on energy balance has been established, and the implications of critical factors on the conversion performance of the thermoradiative-thermoelectric (TR-TE) combined system have been thoroughly examined. The findings show that an optimal ratio of absorber/emitter surface area of 1 is favored due to a tradeoff between thermal radiation loss from the absorber to the ambient and thermoradiative emission dissipation, as well as the thermoradiatives with a low bandgap and a high output voltage. The overall conversion efficiency of the solar TR-TE combined system approaches to 27.86 % at a cold junction temperature of 300 K and a concentration ratio of 50. Accordingly, the maximum efficiency of the combined system is 6.51 times that of independent solar thermoelectrics and is ∼13.67 % higher than independent solar thermoradiatives. In the TR-TE combined system, thermal radiation from the absorber to the environment accounts for 3.83 % of the solar radiation input as compared to 2.47 % in the independent solar TE generator. While the heat dissipated at the cold junction of a solar TR-TE system is 43.66 %, considerably less than that of 84.6 % for independent solar thermoelectrics.