Internal combustion engines used in gas-powered vehicles consume only a quarter of the potential energy of the fuel, with the rest being lost as heat through exhaust gases. However, a new study published in ACS Applied Materials & Interfaces demonstrates a method for converting waste heat into electricity. The researchers presented a prototype of a thermoelectric generator system that could reduce fuel consumption and cut carbon dioxide emissions, promoting the development of sustainable energy initiatives in a rapidly changing world.
Inefficient fuel usage contributes to greenhouse gas emissions and underscores the need for new waste heat recovery systems. These systems, known as thermoelectric, use semiconductor materials to convert heat into electricity via temperature differences. However, many current thermoelectric device designs are bulky and complex, requiring additional cooling water to maintain the necessary temperature difference.
A team of researchers led by Wenjie Li and Beda Pudel has developed a compact thermoelectric generator system that effectively converts the exhaust heat from high-speed vehicles such as cars, helicopters, and drones into electricity.
The new thermoelectric generator contains a bismuth telluride semiconductor and uses heat exchangers similar to those used in air conditioners to capture heat from vehicle exhaust pipes. Additionally, the system is equipped with a radiator that significantly increases the temperature difference, directly affecting the device's output power.
The prototype generator achieved an output power of 40 watts — roughly enough to power a standard light bulb. The study also showed that high airflow speeds, characteristic of exhaust pipes, enhance efficiency and increase the electrical power of the system.
In simulations that mimicked high-speed conditions, the thermoelectric generator system demonstrated high efficiency: it generated up to 56 watts from a car exhaust and 146 watts from a helicopter exhaust. This is equivalent to the power of five and 12 lithium-ion 18650 batteries, respectively.
The researchers note that their system can be integrated directly into exhaust systems without the need for additional cooling devices. They add that with the growing demand for clean energy, this technology could pave the way for the widespread deployment of thermoelectric devices in the transportation sector.