I beleive I understand the process for Geothermal heating, where the compressor extracts heat from the water/feon which in turn heats up a coil enough so when a blower forces air passed it, the hot coil it heats up the air and that air is distrubuted to the house. Now the process works in reverse in the summer, where the compressor extracts cold from the water/feon to cool down a coil so when air passes over it, it cools it down. My question is, is this even nessessary? If the water/feon source is already in the 50's, couldn't the system bypass the compressor all together in the summer and have the water/feon source pumped thru a seperate coil where the air get cooled directly by the source? In a typical system how much power is used for the Pump, Compressor and the Blower? Would shutting down the compresor save all that much energy?
     

I have wondered the same thing as have other people on this forum. It seems to me that you would get some cooling effect by doing this. When my unit is cooling, I get 45° off the top of my heat pump.

If you were running 75° air through a coil with 55° water you might get 60° air. Obviously 45 is better than 60. This might work if your house had very little heat gain.

The energy savings would be significant since the compressor is by far the biggest energy use. If this idea was viable, I would think that we would see it in wide spread use by now.

Also the dehumidification would be greatly reduced in a system of this type.

I wonder if it has to do with the increased heat transfer due to latent heat of vaporization by the freon vs. just raising temp of water. When freon changes from liquid to gas (and vice versa) the amount of heat transferred is MUCH greater than when the temp of water is just raised a few degrees. At least that's the case when changing water to steam.

You are right on.

The phase change ( liquid to vapor ) that the refrigerant undergoes in the evaporator part of the heat pump is how heat pumps can absorb large quantities of heat.

In the winter, the water from the ground is what gives up the heat and vaporizes the refrigerant. 

In summer the air from the house is what gives up the heat and vaporizes the refrigerant. 

It would take a considerably larger amount of loop and water coil surface area to effectively cool a house this way. But, it could be done. The problem is that the cost of doing such a large loop would never be justified by any type of savings. Also, the air flow and water coil would have to be sized to be able to get the type and amount of heat exchange necessary. This probably wouldn't work with normal/standard sized duct.