Low Bandgap Thermo-photovoltaic cells for Clean Energy Generation from Waste Heat

TSB project with QinetiQ, Wafer Technology, Pilkington and RWE npower

We are developing Thermo-photovoltaic (TPV) cells for electricity generation from radiant waste heat to provide major energy savings and reduction in CO2 emissions. TPV cells are solid-state p-n junction semiconductor devices that directly convert heat into electric power. More specifically, TPV cells absorb the predominantly infrared radiation emitted by a flame or heated element and produce electric power by way of the photovoltaic effect. Typically, the voltage generated by each TPV cell is roughly 0.5 V and the current density is 1-3 Acm^-2, producing a power density of ~1 Wcm^-2.

Fig.1 A schematic of a TPV system

Modelling shows that for 1200-2500 K blackbody sources, maximum efficiency and maximum power density would be achieved with TPV cell bandgaps in the range of 0.2-0.5 eV, which is considerably lower than conventional TPV cells. We are using InAsSb and GaInNSb to produce low bandgap TPV cells with improved spectral matching. Such cells will have a significantly higher efficiency with applications for waste heat recovery in the glass and steel industry, also for combined heat-power and remote/silent power generation.

Fig. 2 Prototype designs for a TPV generator with an electric output of 1.5 kW and a heat output of 12 kW (thermal), using a radiant tube burner with a SiC tube, (after Fraas et al, SST, 18 (2003) S247 - S253).

Fig. 3 A multi-kW TPV tube generator concept for industrial or building heating applications. The water-cooled array is surrounded by an infrared emitter and a closed tube that is inserted into a hot zone. (after Mahorter & Wernsman, SST. 18 (2003) S232 - S238)