Denny Esterline 13:22 2004-10-12:
>The cost per btu for electric is 2.5 - 3 times higher than
>the cost per btu of heating fuel. 

Oh, I was just wondering why US have more then twice fossil fuel use per person than western europe...  Here fossil oil is just slightly cheaper than electric on average i believe.  

OK, so the most economic for you would probably be an diesel engine powered heat pump.  Well, the engine produce 70% of the fuel energy as direct heat, so connect the coolant heat hot water tank, and the heat pump need only pump to low temperature for heating.
...But still not as efficient as electric power, and more expensive installation.
( Probably a gas turbine and steam combi system can reach 60% mechanical power, but only feasable on large plants... )

Speaking about efficiency large heat pumps as used in town central sysems are made more complicated to achieve higher efficiency i have read, like:
1) lubricating oil not in freon circulaiton
2) pressure dropping valve replaced by turbine giving back some mechanical/electrc power

Some small heat pumps have frequency controlled compressor so instead of going on/off, it go continuously with reduced power, thus lower temperature drop in heat exchanger, thus lower pressure needed from compressor, thus lower input energy per output.  

I suggested that for my own system, but the manufacturer was afraid the lobricating oil might not circulate reliable with the freon when the flowrate of freon got reduced.  Better safe than sorry.

/Morgan
--
Morgan Olsson, Kivik, Sweden

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