Technology
Thermoelectric Generators for Waste Heat Recovery
Quick fact
A thermoelectric generator can power small devices using just the warmth of your skin—some watches and sensors use body heat to generate electricity!
Why this is interesting
Imagine the heat coming off your car engine or laptop—what if that wasted heat could power something? Thermoelectric generators can convert that heat directly into electricity, with no moving parts.
Read the full explanation
Understanding Thermoelectric Generators for Waste Heat Recovery
Thermoelectric generators (TEGs) are solid-state devices that turn a temperature difference into electrical voltage. They work because of the Seebeck effect: when two different materials are joined and one junction is hot while the other is cold, electrons (or holes) move from the hot side to the cold side, creating an electric current. Think of it like a heat engine, but instead of using a piston or turbine, it uses the flow of charge carriers. The simplest TEG is made of two types of semiconductor materials—p-type (positive charge carriers) and n-type (negative charge carriers)—connected in a 'thermocouple.' By arranging many thermocouples in series, you can build up a useful voltage. This is why TEGs are used in remote locations, space probes (like the Voyager missions), and increasingly in waste heat recovery systems.
A deeper explanation
The core principle is the Seebeck effect, described by the equation V = αΔT, where V is voltage, α is the Seebeck coefficient, and ΔT is the temperature difference. The efficiency of a TEG depends on the material's 'figure of merit' (ZT), which combines electrical conductivity, Seebeck coefficient, and thermal conductivity. High ZT means better conversion of heat to electricity. However, thermoelectric materials are often poor at converting heat—the best achieve only about 10–15% efficiency—so TEGs are most useful where the heat is otherwise wasted and reliability outweighs efficiency, such as in remote sensors, wearable devices, or industrial exhaust systems. In waste heat recovery, TEGs can be placed on hot surfaces (like exhaust pipes) to generate auxiliary power, reducing fuel consumption. The challenge is to create a temperature gradient across the module, often requiring heat sinks on the cold side. While TEGs are not a replacement for large-scale power generation, they offer a clean, silent, and long-lasting solution for scavenging energy from ambient heat sources.