TEGs Could Cool Gas Use

Thermoelectric materials, modules and systems to harness the residual heat in automobiles and increase their efficiency -- by as much as 7 percent -- are being developed at Fraunhofer Institute for Physical Measurement Techniques (IPM) of Freiburg, Germany.

Thermoelectric generators, or TEGs, convert heat into electrical energy by making use of a temperature gradient. The greater the temperature difference, the more current TEGs can produce.

"The temperatures in the exhaust pipe can reach 700 ° C or more," said Harald Böttner, head of the thermoelectric systems department at IPM. "The temperature difference between the exhaust pipe and a pipe carrying engine cooling fluid can thus be several hundred degrees Celsius."

A 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, 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. to the constantly rising number of power consumers in the car. TEGs could cover a significant proportion of a car's power requirements.

A simple calculation illustrates how important it is to increase the energy efficiency of cars, the institute said in a statement: "There are about 50 million licensed motor vehicles in Germany, each of which is on the road for an average of 200 hours a year. If their waste heat was utilized by TEGs during that time, with an output of one kw sufficient to power parts of vehicle electronics, this would add up to 10 terawatt hours of energy per annum -- a significant contribution."

The researchers said they plan to build prototypes soon.

For more information, visit: www.ipm.fraunhofer.de