If you’ve got a water well full of cool water, you can take advantage of that coolness to build a heat exchanger to air condition your home. DIY site Instructables details how to turn some copper pipe, aluminum fins, and a box fan into a very successful, well-powered air conditioner.
I noticed that the water from our well is really cold, under 10 degrees. I built this heat exchanger to take advantage of that cold source for use in the house in the summer…the only actual cost is the power to run the box fan that moves the air through the copper piping.
How well does it work? We hit a high temperature in summer of 44C, hottest that I can remember. The temperature inside was 24C with the cooler running all the time.
This really won’t work unless you’ve got a cool water well, and it can be a little messy (hint: it sweats), but the extremely cheap air conditioning should help you deal.