TEGs

Thermoelectric generators (TEGs) are devices that convert heat directly into electricity using the Seebeck effect. They are solid-state assemblies composed of thermoelectric modules containing p-type and n-type semiconductor elements connected electrically in series and thermally in parallel between a hot source and a cold sink. Because they have no moving parts, TEGs operate quietly and with high reliability, provided there is a sustained temperature difference.

Performance depends on the temperature difference and the thermoelectric properties of the materials, commonly characterized by the figure of merit ZT. In practical devices, efficiency is typically in the single digits and improves with larger temperature gradients and better materials. While the Carnot efficiency sets the theoretical limit, internal electrical and thermal losses keep real devices below that bound. Recent materials research has achieved higher ZT values in certain temperature ranges, but widespread, high-efficiency TEGs remain an active area of development.

Material systems used in TEGs span bismuth telluride for near-room temperatures and lead telluride, silicon–germanium, or related alloys for higher temperatures. More recent research explores skutterudites, clathrates, and other complex materials, including nanostructured composites, to improve ZT. TEG modules typically interconnect multiple p-type and n-type legs to form a complete generator, with effective heat transfer minimized by careful thermal interfaces.

Applications include waste heat recovery in automotive exhausts and industrial processes, small-scale power generation for remote sensors and space missions, and spacecraft power where reliability is crucial. Advantages include solid-state operation, absence of moving parts, and scalability to various power levels; limitations include modest efficiencies, material cost, and the need for adequate temperature gradients and heat-sinking. Ongoing research focuses on discovering materials with higher ZT, improving thermal design, and reducing costs.