I'm buying my first house (1000 sq ft) and it has an old, unused water well. It has a central furnace but no central AC, only window units.
I want to use geothermal to condition the air, but only to cool the house in the summer and supplementing the window units.
Here's my question:
What if I rigged up a geothermal system that simply takes the 55°F well water (open loop system), run it through a car radiator or something, and blow air over it? Won't that give me chilled air?? Now I can blast that air through the existing vents. Right?
Best Answer
The first problem that the heat pump solves is the small differential between the ambient air temp and the temperature you'd expect to get out of such a system.
Let's say your home is at 80 degrees. Let's say (with only wild guesses at actual results) that the air that comes off your radiator is cooled to 65 degrees. (You're unlikely to get anywhere near 55 degrees, your water temperature, with a simple fin-contact radiator.) You now have an air temperature differential of 15 degrees. That's not much, and unless you move massive amounts of air it's not going to give the results you're hoping for. You may drop the room five degrees, or even ten, but that ignores the primary benefit of a true air conditioning system: humidity reduction.
This is the second problem a heat pump solves. By dropping the temperature in the room without a condensation stage, you've now effectively raised the relative humidity. This reduces the sensation of cooling you'll feel, and it could actually cause ugly side effects with respect to your home. Now your windows and walls may start showing condensation because they're cooler than outside, but also wetter.
Basically, if it was that simple, everyone would do it. Unfortunately, it isn't. I'd upgrade your window units or add another one. For the cost and effort you'll come out ahead. (Don't forget that a well uses electricity, too.)