- Human-powered equipment
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A mechanically powered flashlight. This uses a linear generator and is charged by shaking along its long axis.
Human-powered equipment describes electrical appliances which can be powered by electricity generated by human muscle power as an alternative to conventional sources of electricity such as primary batteries and the power grid.
Such devices contain electrical generators or an induction system to recharge their batteries. Separate crank-operated generators are now available to recharge battery-powered portable electronic devices such as cell phones. Others, such as mechanically powered flashlights, have the generator integrated within the device itself. A promising alternative to rechargeable batteries for electricity storage is supercapacitors, now being used in some devices such as the mechanically powered flashlight shown here.
Other devices store the energy mechanically, instead of in batteries. Clockwork radios have a mainspring which is wound up by a crank, and then turns a generator to power the radio.
Contents
Uses
An early example of regular use of human-powered electrical equipment is in early telephone systems; current to ring the remote bell was provided by a subscriber cranking a handle on the telephone set, which turned a small magneto generator. The World War II-era Gibson girl survival radio used a hand-cranked generator to provide power; this avoided the unreliable performance of dry-cell batteries that might be stored for months before they were needed, although it had the drawback that the survivor had to be fit enough to turn the crank.
Human-powered devices are useful as emergency equipment, when natural disaster, war, or civil disturbance make regular power supplies unavailable. They have also been seen as economical for use in poor countries, where batteries may be expensive and mains power unreliable or unavailable. They are also an environmentally preferable alternative to the use of disposable batteries, which are wasteful source of energy and may introduce heavy metals into the environment.
Available power
A trained cyclist can produce about 400 watts of mechanical power for an hour or more, but adults of good average fitness average between 50 and 150 watts for an hour of vigorous exercise. While some exercise equipment has been fitted with generators, the amount of energy collected is of low value compared to the cost of the conversion equipment.[1] A healthy well-fed laborer over the course of an 8-hour day can sustain an average output of about 75 watts.[2]
Examples
See also
References
- ^ Tom Gibson, Turning sweat into watts, IEEE Spectrum Volume 48 Number 7 July 2011, pp. 50-55
- ^ Eugene A. Avallone et. al, (ed), Marks' Standard Handbook for Mechanical Engineers 11th Edition , Mc-Graw Hill, New York 2007 ISBN 0-07-142867-4 page 9-4
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