Geothermal efficiency

tonyzzztonyAugust 23, 2007

I received a quote from the geothermal installer saying I need a 4 ton unit, 4 vertical wells (200 ft each), 2 circulator pumps @ 400 W each etc. So both pumps would be using 800 W while the geothermal unit would be using 2400W.

I asked the installer if it is possible to drill 8 wells @ 100 feet each which should require much less pumping power.

He said its hard to balance 8 wells connected in parallel.

If the loops are the same length I don't see a problem with balancing.

Another question, regarding the COP. Is there any theoretical limit for COP and how close are the manufacturers to reaching that limit? That is another important factor to consider . In the last 10 years COP have doubled. If they could double them in the next 10 years geothermal definitely will be much better than the natural gas or oil

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I'm no expert on this, but that energy usage for pumping seems excessive. Have you looked into a closed loop system?

I have no clue where the COP will go in the future, but I'm pretty certain that gas and oil costs will continue to rise - and probably at an accelerating rate. I expect that in a decade GSHPs will beat gas and oil for cost, even if their COP stays the same.

    Bookmark   August 24, 2007 at 3:52AM
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WeÂre obviously talking closed loop here. Pumping power may be a little high. 2400W for a 4 ton GSHP system is definitely too low! 4 deeper boreholes would be preferred due to ease of installation compared to 8 shallower boreholes. 200ft. per borehole is perhaps conservative but DEFINITELY OK.
I wouldnÂt worry about theoretical future COP Â just get it in the ground now!

    Bookmark   August 24, 2007 at 8:41PM
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