LONDON — Researchers have used thermoelectric generators to harness natural body heat to generate electricity and power electronic systems, according to the Fraunhofer Institute for Integrated Circuits IIS (Erlangen, Germany).

This opens up the prospect of mobile phones powered by body heat or medical electronics and sensor systems powered by the patient's body heat.

Researchers there worked with colleagues from the Fraunhofer Institute for Physical Measurement Techniques IPM and the Fraunhofer Institute for Manufacturing Engineering and Applied Materials Research IFAM.

Thermoelectric generators extract electrical energy from the temperature difference between a hot and a cold environment. However, the differences between the body’s surface temperature and that of its environment are only a few degrees.

"Only low voltages can be produced from differences like these," said Peter Spies, manager of this sub-project at the IIS, in a statement. A conventional TEG delivers roughly 200 millivolts, but electronic devices require at least one or two volts, Fraunhofer said.

Spies claimed that Fraunhofer had built entire electronic systems that do not require an internal battery, but draw their energy from body heat alone.

Voltage multiplier circuits are well known but Fraunhofer did not say if that is what the used to allow electronic systems to operate from a 200-mV primary or what sort of electronics systems it had built,

Spies said that when further improvements have been made to the switching systems, a temperature difference of only 0.5 degrees would be sufficient to generate electricity.

"Electricity can be generated from heat any place where a temperature difference occurs," said Spies. "That could be on the body, on radiators to meter the heating costs, when monitoring the cooling chain during the transport of refrigerated goods, or in air conditioning systems."