Geothermal for cooling only

Discussion in 'Geothermal Heat Pump Applications' started by chiraldude, Mar 11, 2017.

  1. chiraldude

    chiraldude New Member

    I have been thinking about geothermal for a few years but last year the gas company put in a gas main on my street. Running the numbers I find that there is no way geothermal can compete with natural gas for heating purposes. However, I am left wondering if it could make sense to use geothermal for cooling only?
    Specifically I want to compare costs of open loop geothermal to a high SEER conventional AC system.
    I did a crude water quality test/calculation that showed neutral to mild scaling potential so I think I am good for open loop.
    My ground water temperature is about 55 degF so the compressor sizing should be on the small side since it won't have to do that much work.
    Anyone have experience with open loop for cooling only?
     
  2. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Just look at passive cooling then.
     
  3. chiraldude

    chiraldude New Member

    If by "Passive" you mean direct heat exchange between ground water and indoor air, this would require 20-30 gallons per minute and the cost of pumping the water would probably be a deal breaker. Also would require a custom heat exchanger.
    A big question I have is how does geothermal affect the Manual-J calculation? For example, I found a rough online AC calculator that says I need 2-2.5 tons for a standard outdoor air heat exchanger. Would that mean that ground water heat exchange would make 2 tons more than enough?
     
  4. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    No, it wouldn't require that much at all. Passive cooling through a hydronic fan coil is no different in design spec's than radiant cooling through a hydronic fan coil.

    But to answer your question, geo has no effect on Manual - J except for possibly removing setback (10%) sizing.
     
  5. chiraldude

    chiraldude New Member

    Interesting idea to use hydronic coil but there are issues. How to integrate into existing furnace ductwork? Next, I don't think I want to loose the dehumidification. Ground water is 55 and assuming 5 deg rise I get output air temp of 60 degrees. That means the dewpoint will not drop below 60.
    I think I want to stick with a standard freon evap coil. Freon temp is 35 degrees with outflow air temp 40-45 with lots of humidity condensing on the coils.
    What I am looking for: Cost ratio between an open loop water cooled condenser and a high SEER air cooled unit. Then I would need the difference in long term operational costs between the two.
     

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