The standard chilled water systems use water cooled to about 45 degrees going into the heat exchanger and a 10 degree rise in water temperature in the heat exchanger. I am not sure what the temperature of the air leaving the heat exchanger, but expect it would be about 58 to 60 degrees.
What I am contemplating doing is using water circulated through geothermal lines instead of the chilled water. This water would be about 57 to 60 degrees. If it rises 10 degrees , it would require about 285 gallons of water per hour for 2 tons of cooling. The air coming out of the heat exchanger would be about 73 to 75 degrees. There would not be much, if any dehumidifying. And the house would likely be about 80 to 85.
I see this as something to do when one was not home. It should reduce the time for the air conditioner to get the house comfortable. It would require the addition of a heat exchanger and probably some way to duct the air either through the regular evaporator or the added heat exchanger. Maybe the smarter thing would be to have the air conditioner / heat pump chill or heat water. And not have both an evaporator and heat exchanger to deal with.
Has anyone seen such a lashup? And are my numbers reasonable? Does anyone think it would save money over just using a standard geothermal heat pump with a timer to turn on the air conditioning before one expects to arrive home?
Note I am not asking for a design. Just wanting the opinions of practical people with experience. There is likely to be some thing obvious to you all, that I do not see.
Dan