Human power

The average level of human power that can be maintained over a certain duration of time⁠ is interesting to engineers designing work operations in industry.

[clarification needed] Over an 8-hour work shift, an average, healthy, well-fed and motivated manual laborer may sustain an output of around 75 watts of power.

[5] The amount of energy generated is so small compared to industrial power sources that the cost of conversion equipment makes it financially impractical.

[5] For example, supplying an average United States home solely with electricity generated from exercise equipment for one day would require more than a hundred people to ride stationary bicycles for all of it.

In 2007, Jason Lewis of Expedition 360 became the first person to circumnavigate the globe at non-polar latitudes using only human power—walking, biking, and rollerblading across the landmasses; and swimming, kayaking, rowing, and using a 26-foot-long pedal-powered boat to cross the oceans.

Human-powered devices are useful as emergency equipment, when natural disaster, war, or civil disturbance make regular power supplies unavailable.

They are also an environmentally preferable alternative to the use of disposable batteries, which are a wasteful source of energy and may introduce heavy metals into the environment.

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.

[9] The SCR-578 (and the similar post-war AN/CRT-3) survival radio transmitters carried by aircraft on over-water operations were given the nickname "Gibson Girl" because of their "hourglass" shape, which allowed them to be held stationary between the legs while the generator handle was turned.

In 1994, British accountant Chris Staines and his South African partner, Rory Stear, secured the worldwide license to the invention and cofounded Baygen Power Industries (now Freeplay Energy Ltd), which produced the first commercial model.

Like other self-powered equipment, windup radios were intended for camping, emergencies and for areas where there is no electrical grid and replacement batteries are hard to obtain, such as in developing countries or remote settlements.

They also may include multiple alternate power sources, such as disposable or rechargeable batteries, cigarette lighter receptacles, and solar cells.