LONDON Researchers in Germany are working on a thermoelectric generator that converts the heat from car exhaust fumes into electricity. The module feeds the energy into the car’s electronic systems to cuts fuel consumption and help reduce the CO2 emissions from motor vehicles.
In automobiles two-thirds of the fuel is emitted unused in the form of heat. About 30 percent is lost through the engine block, and a further 30 to 35 percent as exhaust fumes.
Thermoelectric generators (TEGs) devices convert heat into electrical energy by making use of a temperature gradient. The greater the temperature difference, the more current TEGs can produce.
Researchers at the Fraunhofer Institute for Physical Measurement Techniques IPM (Freiburg, Germany) are developing thermoelectric materials, modules and systems to harness the residual heat in automobiles.
“The temperatures in the exhaust pipe can reach 700 degrees Celsius or more,” said Dr. Harald Böttner, head of the Thermoelectric Systems department. “The temperature difference between the exhaust pipe and a pipe carrying engine cooling fluid can thus be several hundred degrees Celsius.”
The thermoelectric converter makes use of this huge differential: Driven by the flow of heat between the hot exhaust fumes and the cold side of a coolant pipe, the charge carriers pass through special semiconductors, thus producing an electric current similar to a battery. The long-term objective is to make the alternator superfluous and to supply energy to the constantly rising number of power consumers in the car. TEGs could cover a significant proportion of a car’s power requirements. “This would make it possible to cut gas consumption by between five and seven percent,” said Böttner.