By AR Sajid

Recently researchers at the Public University of North Carolina (USA) developed a new method to convert body heat into electricity. The new system is more efficient than the ones used so far, and also meets the requirement of being comfortable to wear. It is small, lightweight and flexible and measures only one square centimeter and two millimeters thick. According to the researchers it produces up to 20 micro-Watts per square centimeter.

There is a patch which converts body heat into electricity

The design is based on a layer of conductive material that is in contact with the skin and collects body heat, concentrating it in the thermoelectric generator. An exterior polymer reduces the amount of body heat that dispels before bypassing the generator. For the generator to produce electricity the heat must pass through the generator, in a path that goes from the human body to the outside.

A thermoelectric generator is a device that converts heat into electricity. When there is a temperature difference between two metals or two semiconductors, a flow of electrons, an electric current is produced between them. The direct conversion of the temperature difference into electricity is known as the Seebeck effect which is usually limited to a few microVolts for each Kelvin difference.

It produces up to 20 microWatts per square centimetre

Thermoelectric generation has been used for some time. It has also been used in space vehicles wherein voyager probes employ thermoelectric generators of radioisotopes that produce electricity from the heat generated by the radioactive decay of a nuclear fuel, such as Plutonium-238. In this way, the probes remain operational and exist for decades, even when they are too far from the Sun to use solar panels. Radioisotope thermoelectric generators have also been used to supply electrical power to remote installations, such as navigation lights installed at Russian Arctic.

The human body also produces and dispels heat, so it is susceptible to take advantage of the Seebeck effect to produce electricity. However, the amount of heat produced by a person results in low little electric current. Further, the thermoelectric generators have to be worn so it is essential that they should be small, lightweight and flexible, which further reduces their efficiency and capacity to generate power.