Become a fan of Slashdot on Facebook


Forgot your password?
Power Science

Creating Power From Wasted Heat 186

Roland Piquepaille writes "Today, about 90 percent of the world's electricity is created through an indirect and inefficient conversion of heat. It is estimated that two thirds of the heat used by thermoelectric converters are wasted and released. But now, researchers from the University of California at Berkeley have found a new way to convert this wasted heat into electricity by trapping organic molecules between metal nanoparticles. So far, this method of creating electricity creation is in its very early stage, but if it can scale up to mass production it may lead to a new and inexpensive source of energy."
This discussion has been archived. No new comments can be posted.

Creating Power From Wasted Heat

Comments Filter:
  • by Fordiman ( 689627 ) <> on Saturday February 17, 2007 @08:50PM (#18056030) Homepage Journal
    You're exactly right. But the common man doesn't understand 'efficiency gains' as something significant. Perceptually, people don't get how much energy is lost to waste heat.

    I mean, hell. If this works well, it could be used as a component in hybrid vehicles; they only have 25% efficiency on the gasoline engine, and if they're parallel types, the heat generated by the gasoline engine could be used to keep the electrical engine in juice.

    It might even be possible to recapture a bit of energy off the moderate heat generated in the electrical motor.

    Of course, there will be the thermodynamical morons in here, trying to say that this little device is next in the step towards the latest self-powering promise, drawing energy from the zero point or whatever other perpetual motion bollocks is being flouted these days.

    Here's a hint guys: you can't win and you can't break even. You can only take your income (solar energy) and savings (batteries, fuels, and nuclear fuels) and spend it (burning fuel or running electrical equipment). If you can boost your output per unit input, great stuff - but please don't assume it means you've hit a lotto (perpetual motion) that doesn't exist.
  • 2nd Law (Score:2, Interesting)

    by some_hoser ( 656003 ) on Saturday February 17, 2007 @08:56PM (#18056080)
    I hope no one here will forget about the 2nd law of thermodynamics...
  • TEC? (Score:1, Interesting)

    by Anonymous Coward on Saturday February 17, 2007 @09:10PM (#18056196)
    "However, such thermoelectric generators operate at a paltry 7 percent efficiency, compared with the 20 percent efficiency rate for traditional heat engines. Moreover, such converters are made up of exotic, expensive metal alloys, such as bismuth and tellurium, making them too costly and impractical for widespread use."

    Its an organic peltier... nifty. Wonder if it works as well as a heat pump.
  • Re:What? (Score:4, Interesting)

    by anagama ( 611277 ) <> on Saturday February 17, 2007 @09:12PM (#18056208) Homepage
    It's pretty easy to generate electricity from heat. I have a pottery kiln and one method of monitoring temperature is to use a thermocouple hooked up to a "pyrometer". A thermocouple is just two different kinds of metals connected. Somehow, when you apply heat, a voltage develops (I won't pretend to understand how). Now, I'm a cheapskate and because a pyrometer is nothing but voltmeter scaled for temperature, I just use a couple digital multimeters to monitor kiln temps (in the type of firing I do, the measured temperature isn't really relevant -- I'm more concerned with whether the temperature is rising or falling). I typically get 35 - 40 millivolts at my peak temperature (somewhere in excess of 2400 degrees F if I'm doing things right). The cheapo type-K thermocouples I use lose their accuracy as I approach peak temps, but no way am I spending over $200 each for platinum thermocouples.

    Anyway, my point, after reading TFA, it became pretty obvious that this stuff would work like a thermocouple, but you could fit many of them over a large area. It's isn't so much "nano-magic", as it would be a miniaturization of an idea that sees daily application. It sure would be cool if they get it functional.
  • And yet... (Score:3, Interesting)

    by belg4mit ( 152620 ) on Saturday February 17, 2007 @10:00PM (#18056466) Homepage
    Cogeneration only wastes about 1/3 of the energy. That's not too far off from
    the Carnot efficiency of 86% for a combustion temperature of 2000 centigrade.
    And even the reamining "waste" heat could be used if better planning happened:
    district steam, drying and other industrial uses.
  • by TubeSteak ( 669689 ) on Saturday February 17, 2007 @10:02PM (#18056486) Journal

    . The article mentions your car's radiator as an example of wasted heat - no doubt - but to use that heat you need to provide, and maintain a heat differential across your 'recapture device'. Likely the device will just act as an insulator, and your radiator will no longer function. If not you will find that you need some huge fan to blow even more air past the radiator, and now the amount of energy you recover is less than that needed to drive your fan. I also think that the 30% efficiency mentioned for electricity generation is a bit on the low side. Don't hold your breath.
    Why do you have to use the radiator?

    How about sticking this thermocouple directly on the engine block/exhaust pipe/other and just add another radiator somewhere else? You know, like what they do for turbochargers or transmissions.

    It'd be nice if it helped your main radiator, but is doesn't have to. If you don't assume that, then you don't have to worry about a fan or insulation & the rest of your objections vanish.

    But in the end, I'm not sure what you'd do with the extra electricity in a car, unless we're talking electric motors.
  • Re:What? (Score:3, Interesting)

    by fabs64 ( 657132 ) <beaufabry+slashdot,org&gmail,com> on Saturday February 17, 2007 @11:13PM (#18056810)
    Also, from what I read this technology still functions at very low differentials, ie 30 degrees celsius, as opposed to the hundreds that just using two metals requires.
  • by pudro ( 983817 ) on Sunday February 18, 2007 @12:54AM (#18057236)
    Nine times out of ten, the "thermodynamical morons" are the ones shouting down the proponents of the "free" power source. The claims are not about whether perpetual motion is possible (it isn't), but whether or not we can get out more energy than we put in by tapping other power sources (anything from naturally occurring temperature differences to some sort of unknown cosmic energy).

    The people who always bring up the impossibility of perpetual motion lose the argument before it even begins, since they fail to realize that it is not a closed system (and therefore not a claim of perpetual motion). But they yell louder than anyone else, so the general populace goes on believing that the Earth is the center of the solar system.
  • Environmentalists? (Score:4, Interesting)

    by wytcld ( 179112 ) on Sunday February 18, 2007 @01:11AM (#18057326) Homepage
    What's your sample to say what "oh environmentalists" are concerned with? Consider Portland, OR, where environmentalists put in zoning to pack housing into the center of town and prohibit it from sprawling farther out. (True, the anti-environmentalists lately threw a wrench into that with a misleading statewide referendum.) Or on the other side of the country, environmentalists in Vermont are also encouraging more housing in and close to traditional town centers rather than sprawling across the countryside. What is your sample set of "environmentalists" who prefer that we'd all live in suburbs in giant houses? I'd suggest that whoever you can find fitting that description just flies a flag of convenience - the evil often cloak themselves in the names of the good.
  • The analogy that helped me understand the 2nd Law of Thermodynamics was the hydroelectric dam.

    In a hydroelectric dam, you can convert a portion of the potential energy of water flowing downhill into work. You can only convert the energy when the water is flowing downhill and you cannot convert all of the energy because that would stop the water from flowing. The maximum efficiency is the head difference (high and low water points). Unless the low point of the dam is at sea level, you are not getting all of the potential energy out of the water.

    The 2nd Law of Thermodynamics and Carnot Efficiency have the same major points. You can only convert some of the heat to other work while it is moving from hot to cold and the maximum efficiency is the difference in the high and low temperatures relative to absolute zero.

    As the parent post pointed out, power stations attempt to exhaust condensation heat as close as possible to ambient temperatures and there isn't much "waste" heat to recover. If there was an efficient thermocouple device like the article, its use would be in all the industrial waste heat from sources that are currently too small to justify existing heat recovery systems.

Any sufficiently advanced technology is indistinguishable from a rigged demo.