I have been looking into geo thermal heat pumps and the options with vertical vs horrizontal loops.  If the ground is always 55 degrees F, then in theory you have 55 degree water coming in from the ground, and 68-80 degree water coming from inside the house, depending on how warm it is..   Assuming that you size the loop to have enough heat transfer with the ground to actually cool the water to 55 degrees F, it should work, right?

So,
1. would it be possible to put in several bore holes, or some long horrizontal loops in the ground.
2. Run High Density Poly Eurathane tubing in them. 
3. Add grout, or don't add grout..
4. Cascase the loops together back near the forced air gas furnace into one big loop.
5. Construct or modify an evaporator heat exchanger for the forced air system so that it circulates not refridgent, but just water with antifreeze in the geo loops.
6. Put a pump in the middle.

So now you have a cooling only Geothermal system that only costs the ammount of energy to run the pump.

Seems like it would work just fine?

What are your thoughts?

In a typical geothermal system, I've been seeing 1 - 150-200 foot bore hole per Ton of cooling. A 2.5 ton system like my house would require might take 3 bore holes 150 feet each if I was using a compressor system.

In a compressor system, what is the temperature of the water going into the ground measured right after the compressor, and what is the temperature coming out of the ground after going through the geo loop? I assume it doesn't get all the way down to 55 degrees F..


I assume in my method, I might need twice the bore holes to get the same performance of cooling, but even still, it should be more efficient, because you're not running a compressor..

-Jeff

Sorry but this won't work. There is no enough of a temperature differential. Blowing 75° air over 55° water might give you 65° air which will not cool your house. Nice idea though.

Jeff - Geodean brought up a great point.  Your typical cooling system (that uses an outdoor AC unit) creates an evaporator (indoor air heat exchanger) temperature of about 40-45 degrees.  This is just enough to cool the air efficiently and remove dehumidification.

There are some patented products that you can get that have both geothermal heat pumps (for heating) and ground water (for cooling) integrated into one system.  The problem is that you need that 45 or 40 degree ground water temp.  Certain parts of the country (MI, MN, ND) may have colder ground water temps during the summer time.

While the soil temperature may be 55 degrees and inadequate for the cooling, ground water from deeper down may be on the order of 45 degrees, and may be adequate for cooling.

The closer to the surface you go, the warmer the water will be in the summer-time, so you need the deep down water as the source for cold water.

Good luck -

It's more feasible with open loop geo and large radiators (like a floor slab).

In most climates main issue is adequate response to latent load...in other words, dehumidification. While it may seem reasonable, prima facia, to expect a 60*F heat sink be able to create / maintain a 75*F interior temperature, dehu requires taking air down into the low-mid 50s to wring out water. That in turn requires a heat exchanger operating in the 40s. Groundwater that cold is available only in far northern states and Canada.

Heat pump manufacturers offer water only coils in may cases. For it to work with closed loop I think you would find the length of the loop needed to be extrodinary. Slow transfer of heat through soil and hdpe walls might require miles of pipe to keep your EWT from climbing to ambient fairly quickly.
Without the aide of a compressoryou can't limit loop.
j