How Is Human Energy Harvesting Done?

The human body is a natural energy generator. From chemical and thermal processes produced from our eating, kinetic energy produced from our movements, electrical activity produced from our brain, biomass waste produced from our bodies, and fluid flow engendered by our respiration, we are prolific energy producing factories.

Energy harvesting uses natural processes such as wind and tidal waves to capture and store energy. This energy is transformed into a different form, such as electricity, to power devices. The goal of human energy harvesting is the same. Human beings store energy in various ways, and one of them is in the fat you produce when you nosh on your favorite cookies, for example.

The idea of using human motion to produce electricity is not new. Hand-cranks power radios, blenders, ipods, and many other electrical devices. In the search for "clean" sources of energy, scientists and engineers are now studying ways to make the process more ubiquitous and efficient. The stakes are huge, with projections in the range of billions of dollars.

Also, humans make good power sources. The energy would be basically always available, has a small thermal footprint, and does not require any special fuel. Using human energy that would normally go to waste would be an ultimate achievement in recycling.

The average human who has 15% body fat can produce 11 kilowatt hours of energy. The average human also eats about 3.3 kilowatt hours per day. The first law of thermodynamics prevents total energy capture, but you are of interest for harvesting because you have available approximately 128 watts when you stand, 163 watts when you walk normally, and 407 watts when you walk quickly. If you are a sprinter, over 1.6 kilowatts is available, and if you are a long distance runner, you have about 1 kilowatt available. Being asleep you are still useful; then you contribute 81 watts of power.

Of course the available energy production varies according to age, weight, metabolism, gender, and health.

One technology is

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Urine is of interest because it can be used to make fuel cells. It can be hydrolized to make carbon dioxide and ammonia, and then the ammonia can be oxidized to produce nitrogen and water. This technology still has difficulties, because sodium hydroxide is required to make it, and this is a hazardous substance to transport. Also, a technique such as reverse osmosis is required to produce a yield of 0.5 to 1 watt of power.

SEIKO Watch Corporation uses inertia and nanontechnology to create self-winding wristwatches that generate electrical power by using a weight that swings when you move. They are reliable and accurate. For more information, you can read about their Kinetic Brand on their website, and IEEE Spectrum has a good article on inventor Kunio Koike.