Improving the performance of solar thermophotovoltaic (STPV) cells with spectral selected absorbers and small apertured radiation shields

Abstract

An integrated analysis considering radiative energy transport among each component and carrier generation in the photovoltaic (PV) material is established for solar thermophotovoltaic (STPV) devices. STPV has been estimated with previous thermodynamics analysis to provide up to ∼85% solar energy conversion efficiency (ECE) because of its capability to convert broadband solar radiation to narrowband thermal radiation that can be fully used with PV materials. However, in previous demonstrations, the ECE of STPVs is less than 10%, even with ∼200 solar radiation concentrations. Based on our analysis, the maximum ECE of STPV without any radiation heat loss control is nearly zero when the solar concentration ratio is 1 and is ∼18.78% when the solar concentration ratio is 1000. Maximum ECE of STPV with spectral selected absorber optimized for 1000 K level temperature, which has been proposed in recent STPV studies, can be ∼9.56% when the solar concentration is 1 and can be ∼31.72% when the solar concentration ratio is 1000. Maximum ECE of STPV with our proposed multi-layered radiation shield to prevent radiative heat loss from the STPV to the ambient can provide ECE up to ∼9.53% and ∼57.02%, when the solar concentration ratio is 1 and 1000, respectively. When we combine both the spectral selected absorber and our designed radiation shield, the ECE value of STPV can be up to ∼20.65% and ∼59.23% when the solar concentration ratio is 1 and 1000, respectively. It is also observed that a ∼1 µm level bandwidth of photonic crystal (PhC), a device that can control the emission bandwidth, is required for STPV to achieve high ECE under each solar concentration ratio with difference radiative heat loss control.