Efficiency and power density potential of combustion-driven thermophotovoltaic systems using GaSb photovoltaic cells

The renewed interest in thermophotovoltaic (TPV) energy conversion, based on recent progress in materials and photovoltaic (PV) cell technology, requires a new evaluation of the TPV efficiency and power density potential. In this paper, we address some important points in TPV system design. We proceed in three steps, analyzing 1) the thermodynamic limit, 2) an idealized, and 3) a realistic model, based on an extrapolation of the current state of technology. In a TPV system, the radiation converted to electricity is adapted to the spectral response of the PV cell. This can be achieved by different means, which are examined in detail. Broadband and selective radiators, and optical filters are considered. We focus on combustion driven systems using low bandgap GaSb PV cells. For a system containing GaSb cells and a radiator at 1500 K, we find a thermodynamic limit efficiency of 60.5% and an output power density of 3 W/cm(2). For an idealized system model, an efficiency of 34% and a power density of 2.2 W/cm(2) are determined. For a realistic system with a broadband radiator and a filter, 9% and 1.2 W/cm(2) are estimated; using a selective radiator without filter, 16% and 1 W/cm(2) are expected. Performance values of this order should be achievable with a sufficient development effort.