Thermoelectric power generators based on carbon nanotube networks

Carbon nanotubes are either metallic or semiconducting, depending on their chirality. Metallic nanotubes have very high electrical conductivity, and both types of nanotubes have high thermal conductivity. Nanotube networks, composed of semiconducting and metallic nanotubes, either free standing films (buckypaper) or nanotube-filled polymers, still show a high electrical conductivity, but the thermal conductivity is low due to blocked heat flow accross nanotube-nanotube junctions. In addition, nanotube networks exhibit a reasonably large thermoelectric power, so that the thermoelectric figure of merit ZT reaches values of about 0.02. Nanocomposite layers can be stacked so that the thermopower adds, and 51 mV output has been reached for a 72 layer fabric and a temperature difference of 95 K. Further, the electrical properties of nanotubes can be modified by chemical treatment to improve the thermoelectric performance of the nanotube networks.