Body Heat

German scientists from the Fraunhofer Institute for Integrated Circuits have found that there is a way to channel a person's body heat to generate electricity.

The method uses the difference between a body's surface temperature and the temperature of the surrounding environment. The system works through thermoelectric generators, which are semiconductors that produce electrical energy from the temperature difference between a hot and cold environment.

Large temperature difference needed

To generate one or two volts of power, needed to drive most electronic devices, the difference between the body surface and the environment needs to be 20 degrees or more. On average, the divergence is only a few degrees.

"Only low voltages can be produced from differences like these," said project leader Peter Spies.

Standard thermoelectric generators supply roughly 200 millivolts, so researchers experimented with components to create circuits that can operate on voltages that low.

Body batteries

"This has enabled us to build entire electronic systems that do not require an internal battery, but draw their energy from body heat alone," Spies said, adding that with improvements to the system, a temperature difference of only 0.5 degrees will be enough to produce electricity.

"Electricity can be generated from heat at any place where a temperature difference occurs," he said. In the future, he added, it might be possible to make a call from a cell phone with no battery, using just the warmth of one's hand.