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People Power: Capturing The Body's Energy For Work On and Off Earth (cont.)
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Electromagnetic generator: Large muscular groups (especially legs) can generate electricity by simple motions against gravity and small direct current permanent magnet motors. But the center cautions, "there is little or no efforts within the scientific community to design efficient small generators of the type needed for harvesting of human energy."
Thermoelectric materials: These materials convert body heat into electricity by using combinations of materials (metals or today, new ceramics) that are poor thermal conductors and good electrical conductors. When two of them at different temperatures come into contact, electrons migrate, charging a battery or creating usable current through something called the Seebeck Effect. The trouble is that you need great temperature differences to get significant energy, and "on Earth most places are pretty close to body temperature," notes Dr. Henry Brandhurst, director of the center. And what about in the cold depths of space? For the inner solar system at least, photovoltaic panels seem like a better bet, he says.
 | | TECH WEDNESDAY | | | | | | |  | Images |
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| A simple version of a piezoelectric, energy-harvesting device, these sneakers broadcast a location signal while the wearer walks. Image courtesy the IEEE. Click to enlarge.
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But that skepticism hasn’t slowed down efforts at NASA to improve the technology, and one company is already pushing it as an off-the-shelf product. Applied Digital Solutions is unveiling "Thermo Life." The company is "working closely with a watch manufacturer," says Keith Bolton, the chief technology officer. Already the technology has proven itself capable of keeping analog watches ticking, he reports.
And Dr. Rama Venkatasubramanian of the Research Triangle Institute reported in Nature this month a breakthrough in new materials that could double or triple the output of thermoelectric generators.
Electrostrictive polymers: These materials create charge when stretched after voltage is induced through them. No prototype has been made, and there are concerns about how quickly this material might wear out. But it does dovetail nicely with NASA’s conception of the spacesuit of the future, which will be skin tight to maintain mechanical pressure on blood systems in place of the ambient Earth air pressure replicated in "puffy" suits today.
Electrostatic force arrays: (Also called Integrated Force Arrays) A cousin of electrostrictive polymers, this is a new technology. It’s expensive and untested in power generating applications, or for simple durability.
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