Approach proposed by John Robb:
"More than half of all energy usage (not cars and not electricity) is dedicated to heating and cooling of structures (homes and businesses). This expense can be radically reduced by using geothermal heat (50-70 percent).
Here's how it works:
The ground below ~6 feet stays at a relatively constant temperature between 40 degrees and 60 degrees F, depending on the area in which you live.
If you drill a well (the most efficient method to tap geothermal), you can insert a plastic pipe that allows you to pump anti-freeze fluid into the hole. This system, which costs VERY little to operate, uses the earth's energy to either heat or cool the fluid to the geographies standard temperature. The system is nearly maintenance free.
Warmed water from the geothermal system can be used to make heat-pumps very efficient. Cooled water from the system can be used, with a forced air fan, to cool a home.
How it works
The biggest expense in any geothermal system is drilling the wells. Costs are excessive (and can run to $10,000 a home). Fortunately, a volunteer effort very much like a local fire department can accomplish this at a small fraction of this cost.
Drilling rig. Excellent used drilling trucks sell between $50-100 thousand. Leases are much less. There are open source alternatives that can cost MUCH less in the works.
Training. For most communities, the level of training necessary to run drilling equipment fast and efficiently isn't difficult.
Financing of in-house heating/cooling equipment to connect to ground loop stub. Relatively low cost. Community discounts possible. Payback in measured in a handful of years.
Where to start?
The best place to start with a community geothermal effort is with a community property, most likely K-12 schools. This focus would allow the community to generate the funds required to purchase the equipment and train the volunteers as well as pay back the expense quickly. After that common effort is accomplished, volunteer properties (with requirements for contribution) would be the first beneficiaries of drilling efforts, the follow-ons would be based on lottery and so on until all participatory homes/buildings are brought online. Small ongoing contributions from participatory homes, with volunteers exempt, would pay ongoing expenses.