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Researchers have found a way to create electricity using only body heat. Future applications could include cell phones with no battery, powered by the heat from your hand…


New circuits transform body heat – such as that of a hand – into electrical energy simply from the temperature difference between a hot and a cold environment. The technology could result in wireless health monitoring systems that are powered by your body heat alone.
Picture a hospital’s Intensive Care Unit: Numerous items of medical equipment are attached to the body of a patient. They monitor his heart rate, blood pressure, body temperature, pulse and breathing rate. Now also picture the jumble of power cables in that room. All these devices require their own electricity supply, after all.

But if certain German scientists have their way, medical sensors – in the near future – may be able to function without power from a wall socket.

Instead, they will draw all the power they need from the warmth of the human body. And the respective data will be sent by a radio signal to the central monitoring station.

Scientists at the Fraunhofer Institute for Integrated Circuits – in collaboration with colleagues from the Physical Measurement Techniques section and the Manufacturing Engineering and Applied Materials Research team – have developed a way to harness natural body heat to generate electricity.

The new system works on the principle of thermoelectric generators (TEG), made from semiconductor elements.

The TEGs extract electrical energy simply from the temperature difference between a hot and a cold environment.

Normally, a difference of several tens of degrees would be required in order to generate enough power, but 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,” explains Peter Spies, a manager with this project. A conventional TEG delivers roughly 200 millivolts, but electronic devices require at least one or two volts.

The engineers have come up with a solution to this problem.

“We combined a number of components in a completely new way to create circuits that can operate on 200 millivolts,” says Spies. “This has enabled us to build entire electronic systems that do not require an internal battery, but draw their energy from body heat alone.”

The scientists are making further improvements to this system: Circuits that are “excited” at 50 millivolts already exist. Spies believes that in future, when further improvements have been made, a temperature difference of only 0.5 degrees will be sufficient to generate electricity.

The scientists have set their eyes on a wide range of possible applications.

“Electricity can be generated from heat, any place where a temperature difference occurs,” claims 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.”