Tests show how trucks can reuse engine heat for power

The TEG system operates on the principle of the thermoelectric effect, by which differences in temperature are converted into voltage — a phenomenon discovered in 1821 by German physicist Thomas Johann Seebeck, and often referred to as the "Seebeck effect".

"Most fuel energy is not used to drive a truck forward," Risseh says. "Some 30% of this unused energy is lost as heat from the exhaust pipes."

A truck that generates 440kW would see about 132kW of energy disappear in the form of heat coming out of the exhaust pipes, he says. "That's enough to power a typical passenger vehicle."

Capturing this excess energy takes a load off the truck's generator, and in turn, the engine, Risseh says. That means better fuel efficiency and lower emissions.

The Seebeck effect requires a temperature differential — cool on one end of the circuit and hot on the other, which means a truck must rely on a coolant in order to stimulate the voltage.

Cooling the circuit is easier with natural alternatives, such as seawater for a ship's engines. Ships also make good candidates for TEG because their buoyancy offsets the constraints of weight and volume that road vehicles face, he says.

TEG is also regarded as a potential energy saver in data centres that are located in cold climates. Near the Arctic circle in northern Sweden, a data centre that uses 1 Terawatt hour per year could potentially recover 1 Gigawatt per year — a savings of some EUR 100,000, he says.

The research project, which is funded by the Swedish Energy Agency, also includes partners Eberspächer, TitanX and Swerea IVF.