Electric power generation using InGaAsSb and GaSb thermophotovoltaic (TPV) cells was investigated in a gas-fired heating furnace. Electric output characteristics of the TPV cells in the combustion-driven radiant sources are presented. For the InGaAsSb cells, open circuit voltage was higher than 300 mV at a short circuit current density above 1 A/cm(2). The short circuit current of the InGaAsSb cells increased more rapidly than that of the GaSb cells in radiator temperature range 930-1215 degrees C. A mathematical model for the TPV devices was developed to describe the effect of cell bandgap and radiator temperature on electric power output and cell efficiency. Also, the design aspects of the combustion-driven TPV systems are discussed. (C) 2005 Elsevier B.V. All rights reserved.