The Status of Thermophotovoltaic Energy Conversion Technology at Lockheed Martin Corp.

In a thermophotovoltaic (TPV) energy conversion system, a heated surface radiates in the mid-infrared range onto photodiodes which are sensitive at these energies. Part of the absorbed energy is converted into electric output. Conversion efficiency is maximized by reducing the absorption of non-convertible energy with some form of spectral control. In a TPV system, many technology options exist. The development efforts have concentrated on flat-plate geometries with greybody radiators, low bandgap quaternary diodes, front surface tandem filters and a multi-chip module (MCM) approach that allows selective fabrication processes to match diode performance. Recently, the authors achieved conversion efficiencies of about 20% (radiator 950 C, diodes 22 C) for a module in a prototypic cavity test environment. These tests employed InGaAsSb diodes with 0.52 eV bandgap and front surface filters for spectral control. This paper provides details of the individual system components and describes the measurement technique used to record these efficiencies