Numerical Study of a Solar Thermophotovoltaic Energy Converter With High Performance 2D Photonic Crystals

Solar thermophotovoltaic (STPV) systems convert solar energy into electricity via thermally radiated photons at tailored wavelength to increase energy conversion efficiency. In this work we report the design and analysis of a STPV using a high-fidelity 2D axisymmetric thermal-electrical hybrid model that includes thermal coupling between the absorber/emitter/PV cell and accounts for non-idealities such as temperature gradients and parasitic thermal losses. The radiative spectra of the absorber and emitter are engineered by using two-dimensional periodic square array of cylindrical holes on a tantalum (Ta) substrate. The optimal solar concentration and resulting temperature are determined by considering the energy losses associated with re-emission at the absorber, low energy (below band gap) emission at the emitter, and carrier thermalization/recombination in the PV cell. The modeling results suggest that the overall efficiency of a realistic planar STPV consisting of Ta PhCs and existing InGaAsSb PV cells with a filter can be as high as ∼8%. The use of high performance PhCs allows us to simplify the system layout and operate STPVs at a significantly lower optical concentration level and operating temperature compared with STPVs using metallic cavity receivers. This work shows the importance of photon engineering for the development of high efficiency STPVs and offers design guidelines for both the PhC absorber/emitter and the overall system.