The human battery: turning body heat into electric power
August 6, 2007 Previously ignored energy sources are being revisited as both the global will to conserve energy and the technological means to generate it radically improve. Electromagnetic radiation from our cities, acoustic noise and stray radio waves are now being re-classified as potential power sources and the human body itself is being re-examined as a battery thanks to advances enabling the energy from body heat, motion and even blood pressure to be harnessed. A new thermoelectric system created by researchers from the Fraunhofer Institute is at the forefront of these developments - running on a miniscule 200 millivolts the device is able to create an electrical charge from body heat and could lend itself to an endless array of applications that go way beyond powering your own mobile phone.
A thermoelectric generator ((TEG)) draws electrical energy from differences in temperature. The generators previously required a difference of several tens of degrees to be effective, but thanks to a circuitry system created by the Fraunhofer Institute that runs on a miniscule 200 millivolts, TEGs are now able to create an electrical charge from body heat.
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Peter Spies, a manager of the project believes the circuit can be made even more efficient, possibly reaching the stage when a temperature difference of only 0.5 degrees will be sufficient to generate electricity. The number of devices that could be assisted by this development is huge. Not only will consumer electronics such as iPods and mobile phones experience a surge in battery life, but situations in which a person is subjected to an array of more extraordinary gizmos could be greatly simplified, and possibly even revolutionized. A soldier who needs to carry several vitally important electrical items would be not be restricted by an invisible leash tying him to the nearest electrical recharging point. A hospital would be able to move patients with greater ease, and cut electrical cost, by running a patient’s numerous health monitors off their own body.
Wrist watches using kinetic energy as a power source have been on the market for a while – but scientists envision a grander future for the method, as the generators are scaled up in efficiency and size. Kinetic energy is created from movement, and with so many modern products creating near constant vibrations, it’s another example of how ambient energy could be quite easily garnered from a modern working environment. A kinetic generator affixed parasitically to vibrating machines in a factory could create the energy required to power the lights. As with TEGs, scaling the generators down in size once they have reached optimum efficiency may also have benefits. Devices could be powered by the process of breathing, or even by the flow of blood.
Just because ambient energy is about harnessing relatively small forces does not mean that it need be restricted to powering small things. Piezoelectricity is the charge generated by certain materials when placed under stress, for example the energy generated by footsteps. Previously tried and dismissed by the US army, which attempted to apply it on an individual level, the concept is seeing real success in larger scenarios. Japanese train stations are collecting the piezoelectric energy of commuters walking through the gates, and MIT is working on a “crowd farm” which would use a special floor to harness the energy created by the circulation of a large amount of people.
Ambient energy is driven predominantly by researchers seeking more eco-friendly solutions, and by corporations who wish to cut costs. But, true to its nature, it is more than likely it will have the lucky side-effect of powering many exciting and unforeseen technological innovations in the process.