KENSFARM, If your deep earth temp is low enough (temp of well water fresh out of ground not from tank) you can cool with it. A consideration is that since the delta T is less than with a mechanical unit, you need a larger heat exchanger. Nevertheless it can be done.
There are capillary tube systems used for hydronic cooling applications. These are popular in Europe but now available in the US. A mesh of these fine tubes would be plastered into a ceiling or similar applcation and cool water (about 62F) is circulated through. This lowers the radiant temperature of the ceiling and tends to put your body in a radiant heat debt situation. It makes you sense the room as cool. You are radiating infra-red energy out in all directions and similarly receiving radiant energy from your environment. If the net effect is a heat loss you are cooled.
Consider how it feels to be in a warm room in the winter time and walk up close to a large window. You feel a sudden chill. It is not neccessarily a cold draft or leaky window. The energy your body radiates toward the window goes outside and a lot less comes back from the cold outdoor environment so you have a net loss and feel cold.
By lowering the temp of large surfaces (ceiling is usually the best) you lower the intensity of your radiant environment and you give up radiant heat to the cool surface. There are limits to this radiant cooling. If you try to make it too cool you get condensation on the cooled surface. Some supplemental dehumidification (undersized A/C unit running hard and not keeping up is real good one) helps a lot.
This sort of cooling is a good match to your situation as its "design temp" is within the range of what your water will supply with no additional mechanical cooling. The cost of circulating your cold water is way less than running a big heat pump. Too many variables to guestimate payback but there are definite possibilities worth exploring. Unfortunately VERY FEW HVAC guys are HVAC design engineers and few HVAC engineers (in the US) are experienced with hydronic cooling. It is not particularly difficult. It is a fairly straight forward physics application.
If your water is cold enough you may be able to run some through a water to air heat exchanger with slow air movement and get a decent rate of dehumidification. I could mock that up with an old truck radiator. Circulate the cold water slowly through the radiator and turn the radiator horizontal and mount high near the ceiling.
Warm moist ceiling air will be cooled and moisture will condense out (you'll need a drip pan/condensate collection/disposal arrangement.) As the warm air by the ceiling is cooled it will become heavier and will subside, falling through the radiator, whuch sucks more warm air into contact with the radiator. No air handler should be required for this demo system. The colder the water the better (above freezing of course). Mounting it high up near the ceiling will improve performance. The larger the radiator the better.
If you were to try to scale this up to handle your whole house, you have to choose betwen a centralized versus a distributed system. A distributed system could be installed in "troffers" and look sort of like recessed ceiling mounted fluorescent light fixtures. You could use the plastic open diffusers like some office lighting has to dress it up.
A centralized system would require more careful engineering to optimize air volume, flow rates, heat exchanger areas and such. It would be a whole lot easier for a DIY project to go with a distributed system. No duct work and no fans, just a little circulaltion pump. if you fed your house plumbing through this cooling system then whatever water you used in the household would be that much water you wouldn't have to pay to circulate.
The system I describe would dehumidify and do some cooling. There are commercial systems where pipes with chilled water are run in the air near the ceiling with troughs to catch condensate below them. Theaters and large meeting rooms have been done this way. The warm moist air rises and is cooled by the pipes. Some moisture is condensed out and falls into the drain trough below the pipe. Cooled air is heavier and falls back down toward the occupants. As the convection currents are weak and distributed there is no pwerception of a strong cold draft.
This sort of approach will help dehumidify and cool a residence but by itself will probably not satisfy some of the unabashed "polar bears" who have commented in this thread.
Hope you took notes as this material may be on the mid term exam.
Pat /forums/images/graemlins/smile.gif
