Tuesday, December 22, 2009

Body Heat Power Source

Imagine portable electronics that run on a free, reliable energy source. No chargers to worry about, no dropped calls because you played too much Tetris on your Droid, and an endless playlist on your iPod that's truly endless, at least until they pry it from your (literally) cold dead hand. Well, you may not have to imagine for long.

Vladimir Leonov and Ruud Vullers of the Interuniversity Microelectronics Center have developed power supplies that can run off of your body heat. All you have to do is strap on the blingtastic headband you see here, and you're ready to go.

OK . . . the technology is not quite ready for prime time, but it's much more promising than lots of other proposals for systems known as "energy harvesters" that gather power that would otherwise go to waste. Consider, for example, the wasted energy in the jiggling of your own waist (assuming you have a little extra there like I do.) As you go about your day and your spare tire bounces around, all that motion represents energy that could be put to good use. It's truly wasted waist power.

Lots of people have proposed capturing the energy in body motion through complex mechanical contraptions or piezoelectric material. Some systems consist of energy generators in the soles of your shoes. Another one would be incorporated into soldiers' backpacks. It creates electricity as the soldier moves up and down with each step.

It's not a new idea. There have been self-winding watches around for centuries that rely on the random motions of your arm to keep running. The problem with most of them is that the energy has to come from somewhere. It's not a big deal if all you want to do is check the time, but as soon as you try to run something as power hungry as a cell phone, you get into trouble.

Consider the military backpack power supply. Every watt of power it produces is coming from the soldier, which means there's less power available to do everything else a soldier needs to do. Besides wearing a grunt down faster, it will mean he or she will have to eat more to keep going. In effect, you're replacing conventional batteries and power sources with a really inefficient generator (the soldier) that runs on k-rations.

Leonov and Vullers have a much better idea. You produce lots of waste heat, even when you're sitting still. In fact, we have pretty sophisticated mechanisms in our bodies to make sure that extra heat escapes, and your insides stay at a very constant temperature. But that means your body is throwing away energy that could be put to good use. As long as there's a difference between the temperature of your skin and the surrounding environment, then things know as thermopiles can convert the temperature difference to electricity. Using the electricity to run something like this chic electrocardiogram (ECG) shirt can actually help cool you down while keeping tabs on your vitals.

The temperature difference between your skin and the air is too small to generate much electricity, so Leonov and Vullers are working to develop ultra low power devices to go with their thermal energy harvesters. It's a bit of a paradox though, because if you make the power requirements low enough, then why not just carry around a tiny battery?
Well, I'll tell you why. It's because you get to choose between a plain old, boring, run-of-the-mill battery . . . or something like this far out blood monitoring bracelet! I'm not digging the headband energy harvester, but I would totally wear the pulse oximeter. It would go great with the ECG shirt. (Are you getting all this ThinkGeek?)

You can read more about the research by checking out the paper that recently appeared in the Journal of Renewable and Sustainable Energy.

16 comments:

  1. Wow, those are fantastic ideas. I do hope they are able to go somewhere, any amount of energy will become quite valuable eventually. Beside, while as a solitary unit it may not generate much power, with enough people using them when/if they become normal, that will be a hell of a lot of power.
    Great article

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  2. Turning people in to batteries...wasn't there a movie about this.

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  3. Military funding will be all over this (if it is not already)

    Picture a spec ops suit that not only powers itself and all the soldiers modern gear via waste heat, but also reduces his thermal signature enough to perhaps make him FAR less visible to the sort of IR goggles that are quite normal these days..

    or if as predicted the next century is dominated by military action in hostile HOT enviroments having the soldiers uniforms keeping them cool (perhaps uncomfortably cool LOL) while powering their gear as well?

    Of course i predict that as soon as these are comercialized, we will see infomercials for headbands by marie .. under the Gem Keep it cool during menopause brandname!

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  4. Just try wearing at the Airport LOL... They'll shoot you for being a green bomb LOL

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  5. inefficient soldiers? humans are some of the most efficient uses of power that exist.

    compare a human's daily caloric intake (2,000 kcal) to what a gallon of gasoline is (31,000 kcal) , look at animals that eat their body weight in food each day (significantly higher kcal).

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  6. We're efficient at using energy to run ourselves, but using calories to run a generator is very inefficient. That's because most of the calories we use are dedicated to keeping us alive, not moving us around. You could get a lot more useful work from a candy bar by burning it than by eating it and then running on a treadmill to produce electricity.

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  7. Definitely workable for low-power devices, but I call BS on the statement that this helps cool you down.

    Any heat harvesting system relies on a temperature differential - in this case, the temperature difference between your body and the air. If the device were a perfect conductor of heat, a) it would generate no power at all (because there is no temperature differential) and b) this would be pretty much identical to not wearing the device at all.

    In reality, all such devices must be imperfect heat conductors (i.e. they insulate heat), and as such your skin temperature will always be higher than it would be if you were not wearing one of these.

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  8. I believe the above comment about cooling not possible is very incorrect. If this device conducts heat energy better then the surrounding air, then it will feel cool relative to the ambient air. To assume that the surrounding air is a perfect conductor is not correct. the air is far from an efficiant thermal conductor

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  9. Bulova produced a watch called the Thermatron, which worked this way. www.retro-watches.co.uk/watches/A-E/Bulova-Thermatron-Ref-JUN0757.htm

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  10. Call BS that it helps cool you down? Ever sat on an aluminum stadium seat? Notice how your ass is always cooler than if you had just stood around? Yeah that's because air isn't a good conductor of heat.

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  11. On cooling your body: The energy to create the electricity comes from the heat of your body (and the temperature differential). However the devices MUST absorb some of that heat to create electricity, or they'd be totally ineffective as generators. Ergo, they feel cool/cold.

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  12. Since it works from a heat differential, using in a hot environment will actually heat the wearer...

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  13. Citizen already uses that kind of technology for some models of their ECO Drive wristwatches...

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  14. Body heat control many biological function that include gene expression and activity of enzymes. More research on this topic will help scientist to find remedy for genetic disorder through heat stroke.

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  15. I propose building power plants composed completely of Kenyans on treadmills....

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  16. That was a brilliant idea. I never thought that ever since!

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