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from heat to electricity

Discussion in 'Home Power and Microgeneration' started by random, Jul 14, 2003.

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  1. random

    random Guest

    We almost always have a wood fire going, either for cooking or just
    cleanup. Lots of heat going to waste. Is there a good, economical,
    reliable method of turning some of that heat into kilowatts?

    Also what's the consensus on the best type of battery bank, golf cart
    motors? I'm finding battery banks to be of marginal value, good for
    smoothing (reservoir) but not much else. Is that your experience too?
  2. garytulie

    garytulie Guest

    I believe there is a device available working on the reverse Peltier
    principle and capable of generating around 100w from a wood burning stove.
    Alternatively you could use a small steam engine to drive a shaft.
  3. random

    random Guest

    Are these devices available cheaply in quantity? Takes quite a few
    100w's to get into the useful category methinks. I'll see what I can
    learn about the Peltier principle, maybe therein lies the clue.
  4. random

    random Guest

    Thought about that one. Don't claim to be an expert on Stirling.
    Seems it's the temperature difference that determines available
    energy, and the whole general area is hotter'n heck. Got to think
    about it some more. Stirling would be great for a fire next to a cold
    stream, but I'm talking more about just plain heat... fire in a desert
    as it were.
    I'll take a look... the name sounds expensive. Thanks.

  5. [pedantry=on]

    Temperature and heat are not the same thing. Heat is an amount of
    energy. Temperature is an amount of energy *per atom*. The ocean is
    only about body temperature, but it has an enormous of amount of heat.
    A pot on the stove can be boiling hot (temperature), but has a lot less
  6. daestrom

    daestrom Guest

    Actually, temperature is not the amount of energy *per atom*. Witness your
    pot of boiling water, the water and steam are at the same temperature, yet
    the steam atoms have much more energy than the water atoms. But you're
    right that heat is an amount of energy. Two similar terms of heat are often
    confused, the total heat in a body of fluid and the specific heat of the
    fluid. Specific heat is defined as simply the heat per unit of mass. The
    ocean has a relatively low specific heat, but if you multiply that by the
    total mass (measured in the same units as the denomonator of the specific
    heat), you get the enormous number you spoke of.

    But temperature *does* play a part in how much of the heat energy can be
    converted to mechanical energy. With only mild temperature differences,
    even the 'enormous' amount of heat in the ocean is not very useful.

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