I wanted to see how cheap I could build a working geothermal system. I had heard a lot about how expensive these systems could be, so I did some research into how these systems work and decided to give it a try.
You can find lots of information about geothermal systems by searching the web. I found an instructable where someone used the temperature of their well water to cool their house. It made me think " If I could tap into this temperature difference in a closed loop system it could be useful " so I started digging.
Step 1: Digging your hole
Digging a hole like this can be very dangerous. People die in small hole collapses everyday. Even if you have been trained to dig holes like this bad things can happen. Do not dig a hole like this, in most places a four foot trench would be fine.
To get the full benefit from geothermal properties do some research on your area to find the best depth for your zone. Four feet would have been fine for my area, but I wanted to try out a theory I had and by the time I got to eight feet , I had two feet of cool water in the bottom of my hole. Water makes a pretty good heat exchanger and because I live on an island I hit water pretty quick. This lead me to the decision of setting my loop in such an unconventional manner.
Do not try this at home.
Step 2: Your Loop
For my loop I wanted to use the cheapest pipe I could find. It turns out, you can find this type of pipe at any home improvement store for only 10 cents a foot. Plastic may not be the best heat exchanger but with a slow enough pump 200 feet of it should do nicely. If I had some help digging or a backhoe I would have probably gone with 2000 feet, but it's just me and this is just an experiment.