Theoretical performance limits of nonreciprocal thermophotovoltaic power generation for deep-space applications

Abstract

Thermophotovoltaic (TPV) systems exhibit potential for generating electrical power in environments where sunlight is unavailable, such as in deep-space missions. However, the performance of conventional TPV systems that use reciprocal emitters and photovoltaic (PV) cells is limited by Kirchhoff’s law, which constrains the radiative exchange between the emitter and absorber. Nonreciprocal materials, which break the symmetry between absorption and emission, have recently been proposed to overcome this limitation and enhance energy transfer efficiency. In this study, we theoretically investigated the performance limits of a nonreciprocal TPV power generation system operating under cryogenic conditions in space environments. Our model comprised a two-layer thermoradiative (TR) emitter at high temperatures and two-layer PV cell at low temperatures, both employing idealized nonreciprocal materials. We derived the optimal operating conditions based on the generalized Planck’s law and calculated the maximum achievable power density and conversion efficiency for both reciprocal and nonreciprocal configurations. The results indicate that introducing nonreciprocity significantly improves the energy transfer between layers and increases the power output, particularly under large temperature differentials. Additionally, we evaluated the effect of multiple-cell stacking and demonstrated that nonreciprocal systems exhibited broader optimal bandgap distributions than their reciprocal counterparts. These findings suggest that nonreciprocal TPV systems offer a viable pathway for efficient power generation in deep-space missions.