Covert military operations and space shuttle missions are both burdened by the fact that they rely on an inefficient, energy-wasting machine: the human body. Considering one of the biggest logistical problems planners face is getting power to equipment in remote places like Afghanistan or the moon, researchers are devoting their efforts to cut some of those losses through "energy harvesting" from the human body.

Broken into usable terms, waiting to be harvested are 81 watts from a sleeping person, 128 from a soldier standing at ease, 163 from a walking person, 407 from a briskly walking person, 1,048 from a long-distance runner, and 1,630 from a sprinter, according to the center. But of course there’s not 100% capture. Body heat, for example, can only be converted with 3% efficiency with current thermoelectric materials.

Advances in nanotechnology and materials science are causing energy needs to drop at the same time production and transfer of it is increasing. The military applications are humble still, though, aimed at small gear like personal battery chargers, medical sensors, displays, gun sights, and range finders. Boots that turn the compression of a compound into voltage have already powered a radio, according to the Defense Advanced Research Projects Agency. NASA is hoping to feed a range of body monitors, electronics and mission-specific devices. In the commercial sphere, companies are racing to power simple things like watches for now, with an eye to scaling up to handheld PDAs in the future.

Some of the most promising mechanisms for passively converting human body functions into electricity are:

Urine-based fuel cell: Yes, you can turn pee into power and not just by turning a turbine after a few beers. First subject urea to enzymatic hydrolysis to make carbon dioxide and ammonia, and then oxidize the ammonia to nitrogen and water. But the center notes that "one problem with the system is the need for alkaline conditions that may require transport of sodium hydroxide, a hazardous compound. Also, to achieve power generation in the range of 0.5 - 1W, a system to concentrate the breakdown products of urea, such as reverse osmosis, will be necessary." But for astronauts and soldiers on the run, "one attractive feature of this fuel cell concept is the production of water as a by-product of the system."

Inertial energy scavenging: You can own a piece of this technology already – some Seiko watches are powered by a weight that swings as you move, driving a tiny generator. No one expects to generate much electricity from these systems, but deployed in each element needing electricity they could do the trick in concert. Also, while gravity is absent in space, inertia is not.