Car exhaust heat could be turned into electricity, experimental study reveals

Could exhaust heat from high-speed vehicles be converted into electricity to provide a sustainable energy source? A team of researchers from the Pennsylvania State University, USA has developed a prototype thermoelectric generator system to efficiently convert exhaust waste heat from high-speed vehicles such as cars, helicopters and unmanned aerial vehicles into energy.

Vehicles that run on fossil fuels have combustion engines that only use 25% of the fuel’s potential energy, with the rest lost as heat through exhaust. This fuel inefficiency also contributes to greenhouse gas emissions.

A study published in ACS Applied Materials & Interfaces, titled ‘Thermoelectric Energy Harvesting for Exhaust Waste Heat Recovery: A System Design’ reveals that exhaust heat can be converted into electricity using the prototype thermoelectric generator system, thereby, potentially reducing fuel consumption as well as carbon dioxide emissions.

According to the researchers, thermal energy harvesting in high-speed moving objects is particularly promising for providing an efficient and sustainable energy source to enhance operational capabilities and endurance. By exploiting temperature differences between a heat source and ambient temperature, thermoelectric technology can provide a continuous power supply to such systems, reducing the reliance on conventional batteries and extending operation times. However, many existing thermoelectric devices have a heavy and complex design, requiring additional cooling water to maintain the necessary temperature difference.

The researchers led by Wenjie Li and Bed Poudel from the Department of Materials Science and Engineering at Pennsylvania State University have developed a compact thermoelectric generator system to efficiently convert exhaust waste heat into energy. The new thermoelectric generator incorporates a semiconductor made of bismuth-telluride and uses heat exchangers (similar to those used in air conditioners) to capture heat from vehicle exhaust pipelines. The prototype system also includes a heatsink to significantly increase the temperature difference and directly influence the electrical output. 

This prototype achieved an output power of 40W, just about enough to power a lightbulb. The study also revealed that high airflow conditions, such as those found in exhaust pipes, enhance efficiency, thereby increasing the system’s electrical output. In the simulation conducted to demonstrate the waste heat recovery system’s feasibility under high-speed moving vehicle conditions, the system produced up to 56W for car-like exhaust speeds and 146W for helicopter-like exhaust speeds, equivalent to five and 12 lithium-ion 18650 batteries, respectively. 

According to the researchers, this system can be integrated directly into existing exhaust outlets without the need for additional cooling systems. With the increasing demand for clean energy solutions, this study could pave the way towards practical integration of thermoelectric devices into high-speed vehicles.

Image: Researchers design and test a waste heat recovery system that attaches to a car tailpipe and converts heat from exhaust into energy. The fanned grooves on the outside of the pipe are the cold side of the device’s heatsink and the triangular components inside the pipe are plate-fin heat exchangers. (Source: ACS Applied Materials & Interfaces 2025, DOI: 10.1021/acsami.4c18023)