Thermoelectric power

Discussion in 'The Projects Forum' started by jpanhalt, Jan 31, 2010.

  1. jpanhalt

    Thread Starter AAC Fanatic!

    Jan 18, 2008
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    I have just acquired a vacation home that has hot water heating and can use either or both propane or an outside wood burner for a heat source. There is plenty of waste wood to burn (it is in the middle of a large area of woods). However, either source requires electricity to run a circulating pump. The required pump is not terribly big. A 1/12 HP might work. The standard is 1/6 to 1/4 HP.

    Has anyone looked at using a thermo electric generator to charge a battery/inverter system, so the entire system could be independent, if needed, except for the wood? Typical water temperatures in the heating system ranges from 60°C to 82°C. It is a low pressure system so steam is probably out of the question.

    I was pleased to find this device: http://customthermoelectric.com/tecs/pdf/12711-5L31-09CQ_spec_sht.pdf

    It would not take many of them to run a 1/4 HP motor.

    John
     
  2. retched

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    Dec 5, 2009
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    How about a thermal loop rather than a pump? That should be even more efficient.

    A lot of homes that use solar water heaters use a loop rather than a circulating pump.

    Easiest way, insulate everything except the last 15ft of line. That 15ft of cooling will allow the water to cool enough to start and continue a current. As long as the incoming cool water is at the bottom of the storage tank.
     
    Last edited: Feb 1, 2010
  3. 3ldon

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    Jan 9, 2010
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    You might get 2 watts out of those things when you run them backwards.
    If you have a lathe I'd build a sterling engine.
     
  4. jpanhalt

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    Jan 18, 2008
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    Good point, I grabbed the wrong link. It seemed too good to be true and was. I have more than a little problem reading. Here is the correct link:http://customthermoelectric.com/powergen/pdf/1261G-7L31-10CX1_spec_sht.pdf

    As for a Stirling engine, from further reading, a low temperature differential version would have to be quite large for even that low a power output.

    I guess I am stuck with a small diesel generator.

    John

    Edit: Right now, it is just a second home. Once I am there most of the time, I may experiment with using pentane or ethanol as the working fluid in a closed system. Their vaporization and condensation temps seem about right for a system that is limited to 180°C for the hot side. The whole concept of being completely independent from outside energy sources, except wood, is just too appealing to resist. jpa
     
    Last edited: Feb 2, 2010
  5. 3ldon

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    Jan 9, 2010
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    its not too good to be true because you posted to the wrong link, its too good to be true because those things are so in efficiant.
    why is the hot side limited to 180C?


    That it what I would do, except I would use isobutane/propane, not pentane
    If you can manage to get the rotor to float on an "air" bearing, then you can completly enclose the radial inflow turbine and use a direct drive air core alternator.
     
  6. jpanhalt

    Thread Starter AAC Fanatic!

    Jan 18, 2008
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    In my first post, I converted to Celsius, but screwed up here. Actually, the hot side is limited to 180°F, another error. I have had some severe lower back spasms being treated with pain killers (day 6). I am not quite sober. Sorry for all of my recent slips.

    In any event, it is a hot water system, not steam. The control valves are set with an 82°C limit.

    Your idea for a wetted alternator is appealing (wetted with the working fluid). One of the circulating pumps for the water is constructed that way. I joined the "hot air" forum, but it seems mostly related to solar and is not very active.

    Do you have any leads at all to a design of an alternator like we are discussing?

    John
     
  7. 3ldon

    Active Member

    Jan 9, 2010
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    Due to the low temperature I would look into purchasing a geothermal heat engine off the shelf.

    I do know of a few commertial products that basically run an off the shelf scroll compressor backwards, (lost the links a year or so back), this is also a home brew solution if you have 15KW of heat available to run a 3 kw compressor, i don't know if you can get anything smaller.(basically remove the check valve and that's all there is to it)
     
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