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Turning Heat Into Sound Into Electricity

Posted by ScuttleMonkey on from the sounds-like-a-hot-idea dept.

WrongSizeGlass writes "Science Daily is reporting on work by physicists at the University of Utah who have developed small devices that turn heat into sound and then into electricity. 'We are converting waste heat to electricity in an efficient, simple way by using sound [...] It is a new source of renewable energy from waste heat.' They report that technology holds promise for changing waste heat into electricity, harnessing solar energy and cooling computers and radars."

7 of 257 comments (clear)

  1. But.... by a.phoenicis · · Score: 5, Funny

    But does it change waste heat into electricity? I'm not quite sure based on that write-up...

  2. Sound to electricity. by snowraver1 · · Score: 5, Funny

    Now they need to refine this to 100% effiecency and attach one to my wife.

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  3. Efficiency as opposed to thermoelectric? by Anonymous Coward · · Score: 5, Interesting

    I just skimmed the article, but I didn't see mention of the efficiency of this process. What are the advantages to converting the heat to sound first, rather than directly to electricity via thermoelectric processes?

  4. Maxwell's Daemon Rides Again? by overshoot · · Score: 5, Informative
    Unless they're claiming to have found a way around the Second Law, the efficiency of any such conversion is going to utterly suck. My CPUs run less than 10C above ambient, so the absolute Carnot limit on any converter recovering that heat is going to be about 3%.

    Why bother?

    [1] Thermodynamics, not Robotics

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  5. Heat to Sound to electricity. by malvidin · · Score: 5, Funny

    Well, luckily my wife doesn't need to be loud. She's that hot.

    1. Re:Heat to Sound to electricity. by pan_piper · · Score: 5, Funny

      Well, luckily my wife doesn't need to be hot. She's shocking.

  6. Just a little prob with the numbers.... by Ancient_Hacker · · Score: 5, Insightful
    Nothing to see here. It's just a Prof that's spent $2 million on a wild goose chase. Now with the great smell of fish! The rub is multi-fold:
    • Good old Carnot's law. The efficiency is limited by the temperature drop across the device compared to the absolute temperature. Now take two thermometers, stick one up your butt and fart. compute the temperature difference. Divide by 483. That's your efficiency in converting heated gas into sound. Prolly about 0.005% as a rough approx.
    • For a less gross example, pucker your lips and blow. Do this for five minutes or until you pass out. You probably feel warm-- that's the heat. How much acoustic power did you generate? Well a loud whistle is about 100dbA, about a hundredth of a watt. Efficiency, 0.004% at best.
    • Piezoelectic efficiency. Well, it's really high-- for an acoustic transducer. The Interwebs seem to reveal no figures for this, and in general a high level of coyness is a way of hiding embarrasing numbers. Let's assume a best-case number of say 40%.
    • The impedances. Crystals are very high impedance devices, putting out LOTS of volts at vanishingly small amps, which is bad news for us, as most of our power sinks are low impedance. Getting a few milliamps at 40KV is not very compatible with powering your laptop, which is about a million times lower in impedance. It's particularly inconcvenient converting tens of kilovolts downwards with economy and efficiency.
    So sorry, probably much less than nothing to see here, just another bundle of our taxpayer's money spent on a totally pointless technical exercise.