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Heat pump electricity production

  1. Nov 1, 2014 #1


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    Greetings. I just want to understand heat pumps. As far as I know - they keep a house warmer than it could be using a regular electric radiator, using the same amount of energy.
    I am wondering - if a heat pump outputs, say, 3 kW of heat energy from 1 kW of input electric energy from the grid (or somewhere), making the air (or ground) source colder, of course, it would take only ("only" as in - it is doable) ~40% efficient thermo-electric generator to gain 1.2 kW from that heat, from which 1 kW could be run back in to the pump and have a surplus of 0.2 kW
    Please, don't sink this thread, as I am not talking about perpetual motion here. (although, perpetual motion is a must in a perfectly sealed system, in a not expanding universe, isn't it? Of course, the Earth isn't a perfect system, but it gains energy from the Sun as it looses energy in space ..)
    I would like to mess around with some refrigerator parts and Stirling engines, but both my hands are left, so to say, and I just don't have the resources
    Last edited: Nov 1, 2014
  2. jcsd
  3. Nov 1, 2014 #2


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    Staff: Mentor

    What do you mean by saying that a "heat pump outputs 3kW from 1kW input electric energy"? Do you have a reference for that?
  4. Nov 1, 2014 #3


    Staff: Mentor

    Yes, you are, this is a PMM of the second kind. Discussions of PMM's are against the rules.

    What you describe is not "doable". To confirm you should fix the temperature of your cold reservoir and calculate the hot reservoir temperature required to get an ideal heat pump with a COP of 3. Then calculate the efficiency of an ideal heat engine between those same two temperatures.
    Last edited: Nov 1, 2014
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