Thermo-photovoltaic

Thermophotovoltaic (TPV) energy conversion is a direct conversion process from heat to electricity via photons. A basic thermophotovoltaic system consists of a thermal emitter and a photovoltaic diode cell.

The temperature of the thermal emitter varies between different systems from about 900 °C to about 1300 °C, although in principle TPV devices can extract energy from any emitter with temperature elevated above that of the photovoltaic device (forming an optical heat engine). The emitter can be a piece of solid material or a specially engineered structure.Thermal emission is the spontaneous emission of photons due to thermal motion of charges in the material. For these TPV temperatures, this radiation is mostly at near infrared and infrared frequencies. The photovoltaic diodes absorbs some of these radiated photons and converts them into electricity.

Thermophotovoltaic systems have few to no moving parts and are therefore quiet and require little maintenance. These properties make thermophotovoltaic systems suitable for remote-site and portable electricity-generating applications. Their efficiency-cost properties, however, are often poor compared to other electricity-generating technologies. Current research in the area aims at increasing system efficiencies while keeping the system cost low.

TPV systems usually attempt to match the optical properties of thermal emission (wavelength, polarization, direction) with the most efficient absorption characteristics of the photovoltaic cell, since unconverted thermal emission is a major source of inefficiency. Most groups focus on gallium antimonide (GaSb) cells. Germanium (Ge) is also suitable. Much research and development concerns methods for controlling the emitter's properties.

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