Generate power from waste heat?

2twisty
2twisty Solar Expert Posts: 199 ✭✭✭
in Off Grid Solar & Battery Systems #1
I'm considering building a Thermal Mass Rocket Stove to heat my house in the winter time when I go off grid. Even though it's in the desert, It can get quite cold during the winter months, and having a heat source is a good plan. For those who are interested, I'm thinking of doing something like this:

http://www.permies.com/t/18515/stoves/Burning-Pellets-Rocket-Mass-Heater


Anyway, on that forum, the topic of using piezoelectric devices came up, and I thought "hey, why not use them for battery charging!"

I found this unit after a quick search.

http://tegpower.com/pro3.htm

Kinda expensive at $5/watt, but I bet there are larger/cheaper units out there.

What do you think?
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Comments

  • solarix
    solarix Solar Expert Posts: 713 ✭✭
    #2
    Re: Generate power from waste heat?

    Sorry, piezoelectric devices are just plain expensive and converting low quality waste heat into high quality electricity is an uphill battle and not cheap either.
    Recommend using new larger/cheaper PV units outside to catch the waste photons coming of that fire thing overhead 93,000,000 miles away.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #3
    Re: Generate power from waste heat?

    To be clear, what you are citing is a. THERMAL ELECTRIC DEVICE, not a Piezo device. TEDs are not really very useful sources of power in an off grid sense. I have tried building remote fans, small chargers etc, all with no real success. In addition to heat, you need cool to make them work, since they work by Delta T. The eco stove top fans work, because they have a large heat sink on the hot side, as well as in the cold side. The fan itself drawing air over the cold side to create the Delta.

    Years ago, I wante to try to power a computer fan on the ceiling with such a device. I wired a bunch of these together in series, mounted a finned aluminum heat sink on the cold side, and set it on the stove. The only way I could et it to work,, at all, was to add Alice block on the cold side! Of course, with the ice sitting on the stove, that didn't last too long.

    It seems tht TEDs are better suited as heaters or coolers rather than generators.

    Tony
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,646 admin
    #4
    Re: Generate power from waste heat?

    Or direct flame heating... And with wood stoves, that could also have the draw backs of cooling the combustion air enough that you get water condensation and soot/creosote buildups on the "cool parts" the TEG.

    They do work and are used with propane tanks in remote outposts where reliability is key... But they are not that efficient otherwise (the lower the temperature between the "hot" and the "cold" (steam engines, piston engines, etc.), the less efficient they have to be according to the laws of thermal dynamics.

    But not to say that it cannot be done for smaller amounts of power:

    Warm Up, Cook, Recharge: A Smart Tool Born of Hurricane Sandy
    The BioLite CampStove is about the size of a coffee urn. Developed as the hot new toy for hikers, the stove houses a small fire that burns from hunter-gatherer fuel sources—dry twigs, pinecones—and, in addition to warmth, generates electricity for users to charge mobile devices. You can cook on it, too. But with hundreds of thousands of people without power for days following the wrath of Sandy, and many in the New York region still in the dark, a serendipitous new function of the CampStove—disaster relief—has come to light.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • solarix
    solarix Solar Expert Posts: 713 ✭✭
    #5
    Re: Generate power from waste heat?

    My bad, you are correct - not piezo, peltier.
    The piezo effect is the relationship between electricity and mechanical stress.
    The peltier effect converts heat differential into electric potential. Some kind of magic at the atomic level.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,646 admin
    #6
    Re: Generate power from waste heat?

    Just to see how much (or how little) power:

    Fuel Renewable biomass (twigs, pinecones, wood pellets, etc.)

    Fire Power Output Peak: 3.4 kW (LO), 5.5 kW (HI)

    USB Power Output Max continuous: 2W @5V, Peak: 4W @5V

    My pretty small folding solar panel will output 7 watts--Of course, that is 7 watts over 2-7 hours a day (14-49 WH per day) vs how ever long you can feed the stove (48 WH per day)--for roughly the same price.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #7
    Re: Generate power from waste heat?
    solarix wrote: »
    My bad, you are correct - not piezo, peltier.
    The piezo effect is the relationship between electricity and mechanical stress.
    The peltier effect converts heat differential into electric potential. Some kind of magic at the atomic level.

    Actually, I just recently learned that it's not peltier.
    From a recent thread:
    inetdog wrote: »
    Small quibble, but as a physicist I could not let it go:
    The Peltier effect, as originally discovered lets you directly use electrical energy to pump heat.
    The Seebeck effect, as originally discovered, lets you transfer heat to get electrical energy.
    Since both Peltier and Seebeck are long dead, they probably don't care anymore.

    To complicate matters, both the Peltier and the Seebeck effect are thermodynamically reversible, so one can reasonably argue that they are in fact exactly the same thing, the Peltier-Seebeck effect.

    But for convenience, you normally see the name Peltier for the thermoelectric heating/cooling application and the term Seebeck for the power generation application.

    inetdog wrote:
    FWIW, the ECOfan site says that they use the Seebeck effect and I just did not want anyone to get confused. (Wikipedia does not help much. )

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • boochar
    boochar Registered Users Posts: 2
    #8
    Re: Generate power from waste heat?

    I registered on this forum just so I could warn people about the Tegpower scam.

    About 8 weeks ago I ordered a TEG chip from Tegpower.com. The initial email I got from them advised there might be 3 to 4 weeks waiting list. It has been longer than that now and I have sent them a couple of emails asking when I could expect to receive my order and I have had absolutely no reply. I would like to warn everyone here that this company is a fraud so DO NOT BUY ANYTHING OFF The TEGPOWER SITE. 2 others have contacted me and have also not received their orders. The website domain owners are “Contact Privacy Inc. Customer 0117997669” the street address appears to be a parking lot. This scam is supported by PayPal, TTUCOWS DOMAINS INC & Contact Privacy Inc.

    Is there anyone in this groups who lives in WV and could check the street address? I just hate getting ripped off!

    Regards from Downunder
    Hans
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,646 admin
    #9
    Re: Generate power from waste heat?

    Sorry to hear about your problems with Tegpower.

    Their address is just a UPS (United Parcel Service) PO Box (private company hosted PO Box):

    http://www.theupsstorelocal.com/1421/

    TEG Power 364 Patteson Drive #316 Morgantown, WV 26505-3202

    (Drop the Teg Power and #316 from the searches).

    That is why they don't want anyone showing up to their "place of business":

    http://tegpower.com/contact.html
    Sorry, no walk-ins or phone calls please.

    and, for what it is worth--An "F" rating from BBB:

    http://www.bbb.org/canton/business-reviews/electrical-discharge-machining/teg-power-in-morgantown-wv-92003109/
    (304) 285-8408 (phone number from BBB)

    • BBB does not have sufficient information to determine how long this business has been operating
    • 7 complaints filed against business
    • Failure to respond to 4 complaints filed against business
    • 5 serious complaints filed against business
    • BBB does not have sufficient background information on this business
    • Business has failed to resolve underlying cause(s) of a pattern of complaints

    Who ever they are--There is not much about the company besides their website that I could see...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • boochar
    boochar Registered Users Posts: 2
    #10
    Re: Generate power from waste heat?

    Thanks for the extra information on Tegpower Bill.
    It is amazing that someone can get away with this for so long, and in the USA not Russia or Nigeria. Lets hope it is not a business plan too many others pick up on.
    Hans
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  • texneus
    texneus Registered Users Posts: 5 ✭
    #11
    Re: Generate power from waste heat?

    Sounds like an ideal application for sterling engine to me. I don't have any idea though how available or how expensive something large scale would run though. Might have a look here and see where the links go. http://peswiki.com/index.php/Directory:Stirling_Engines
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #12
    Re: Generate power from waste heat?
    texneus wrote: »
    Sounds like an ideal application for sterling engine to me. I don't have any idea though how available or how expensive something large scale would run though. Might have a look here and see where the links go. http://peswiki.com/index.php/Directory:Stirling_Engines

    Except for very specialized situations (like thermal power to electric conversion on a satellite, for example) Stirling engines just have not lived up to their hype.
    To my mind their greatest single useful application is that their output can easily be calculated as a homework problem in a thermodynamics class.
    SMA SB 3000, old BP panels.
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