Closed loop Air to Air Geothermal idea??

Discussion in 'Geothermal Heat Pump Applications' started by Avro, Aug 28, 2017.

  1. Avro

    Avro New Member

    Hi guys, I would like to get to opinions on a idea. I have a air to air heat pump and was wondering if I layed out about 800 feet of big-O drainage pipe 8 feet below surface and funneled the air closed loop to the outside coil of the heat pump. So the unit would only use the air coming from the ground. Now this concept kind of works with the poor mans geothermal but I would step it up with the air to air heat pump. To my knowledge the pump wouldn't need much stepping up on a cold day since the ground air is much warmer. So am guessing the pump wouldn't need to work very hard to maintain the room temperature. The application would be to heat a large workshop area. Please comment if this would work? mainly I have a limited budget and can see this being a possibility
  2. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    What is the diameter and air flow friction loss of "big-O drainage pipe"? I don't know what that consists of.

    It seems theoretically possible to use air circulating through a buried pipe (let's call it a buried duct) to gather ground heat for use in an air source heat pump. However, my guess is that you'd have your lunch eaten by either the cost of the large diameter pipe (duct) needed to carry the required amount of air or the prodigious blower power needed to push the air through the long and corrugated pipe / duct.

    Keep in mind that a typical high efficiency air source heat pump moves at least 2 cubic feet of air through the outdoor heat pump for every 1 cubic foot of air through the indoor air handler. For example, a nominal 3 ton heat pump flows 1100 - 1200 CFM through the air handler while also blowing twice that amount or more through the outdoor heat pump.

    Continuing my 3 ton example, pushing 2000 - 2500 CFM through a multi hundred foot buried pipe / duct likely requires a heckuva lot more power than that saved by giving an air source heat pump a somewhat warmer source of air...
  3. Avro

    Avro New Member

    The loop would consist of four or five 4" pipes to allow enough air flow. Now if the outdoor heat pump fans had to work harder to move the air what could happen? would it freeze up? or would efficiency would go down?

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