75% of the energy in an internal combustion engine literally goes up the drain or is dissipated as heat. It would be tempting to harness that energy for useful work, such as generating electricity — recharging batteries in hybrid cars while they’re moving or charging mobile devices. The problem has intrigued scientists at Penn State University so much that they’ve come up with a simple tailpipe attachment to generate electricity from emissions.
Image source: ACS Applied Materials & Interfaces 2025
The researchers developed and tested a radiator system that created a significant temperature difference without additional cooling (such as water). The greater the temperature gradient, the more efficient the thermoelectric generator, since electrons flow more actively from the heated zone to the cooled one. The system of overhead radiators proposed by the scientists turned out to be quite effective and universal, which allows its installation on the exhaust pipe of any vehicle with an internal combustion engine.
To convert the exhaust heat into electricity, the scientists used a semiconductor material — bismuth telluride. The nozzle, installed on the exhaust pipe of the car, allowed to generate 56 W of electricity when simulating movement at maximum speed. The calculated power of the generator under standard conditions was 40 W — this is enough to charge a smartphone or laptop for free. Probably, the system will also help hybrid cars to move longer on electric traction, recharging the batteries on the go while the internal combustion engine is running.
Installing the same thermoelectric generator on the helicopter’s exhaust pipe allowed it to generate 146 watts of electricity – three times more than a car. Of course, for the helicopter’s onboard systems, this is a drop in the ocean, but without the generator, this energy would simply dissipate in the air. Now it makes ICE transport slightly more efficient and less harmful to the environment. Perhaps such developments will be a step towards improving internal combustion engines before they give way to environmentally friendly types of transport.