Technology
Thermoelectric Generators for Waste Heat Recovery in Vehicles
Quick fact
Typical automotive TEGs can generate up to 1 kW of electrical power from exhaust heat, which can improve fuel economy by 2-5% depending on driving conditions.
Why this is interesting
Your car's engine wastes about two-thirds of the fuel's energy as heat. What if some of that heat could be turned back into electricity to power your car, saving fuel and reducing emissions?
Read the full explanation
Understanding Thermoelectric Generators for Waste Heat Recovery in Vehicles
Imagine a thermoelectric generator (TEG) as a heat-powered battery. It sits between something hot and something cold—in a car, between the hot exhaust pipe (up to 600°C) and the cooler ambient air. Inside the TEG are special semiconductor materials that exploit the Seebeck effect: when there is a temperature difference across the material, the heat energy causes electrons to flow from the hot side to the cold side, creating a voltage difference and thus an electric current. This is how a TEG converts a temperature difference directly into usable electricity, with no moving parts. In a vehicle, the TEG is installed near the exhaust system, and the generated electricity can be used to charge the battery, power lights, or assist the alternator. By recovering some of the heat that would otherwise be lost, the engine has to work slightly less to produce the same amount of electrical power, improving overall fuel efficiency.
A deeper explanation
The core principle behind TEGs is the Seebeck effect, a thermoelectric phenomenon discovered in 1821 by Thomas Johann Seebeck. When two dissimilar conductors or semiconductors are joined in a circuit and maintained at different temperatures, a voltage develops proportional to the temperature difference. In modern TEGs, this is achieved using semiconductor pairs (p-type and n-type) connected electrically in series and thermally in parallel. The efficiency of a TEG depends on the material's dimensionless figure of merit (ZT), which combines electrical conductivity, thermal conductivity, and Seebeck coefficient. High electrical conductivity and Seebeck coefficient are desired, but low thermal conductivity is also needed to maintain a large temperature gradient. Automotive TEGs face challenges: the exhaust temperature varies with engine load, and the heat exchanger must be efficient without adding excessive pressure drop to the exhaust system. Researchers are exploring materials such as bismuth telluride, lead telluride, and skutterudites, each effective at different temperature ranges. Real-world applications in vehicles are still emerging, but prototypes have shown that TEGs can generate up to 1 kW, improving fuel economy by 2-5% by reducing the alternator load and powering auxiliary systems. This represents a step toward more sustainable transportation by recovering energy that would otherwise be wasted.