Peak oil, energy, and society/Frederick's page

Geothermal systems can heat and cool buildings by connecting them to the stable temperature of the earth. The technology found in the compressor of home refrigerators --in this application, called a "heat pump"-- is necessary for most geothermal systems. Refrigerators actually work by pumping heat out of the food compartment of the fridge; the heat is vented into the room, and the food cools down. A geothermal system drills a well deep into the earth, perhaps 100' down, perhaps 500'; at these levels, the temperature is always around 45 or 50 degrees. Some systems draw water from this deep well; other systems circulate water from the surface through closed pipes into the well and back out, allowing the water to become the same temperature as the earth. Either way, the water brought to the surface is sent to the heat pump. If the building needs to be heated, heat is pumped out of the water into the building; if the building needs to be cooled, heat is pumped out of the building into the water. The water is then recirculated back into the well where its temperature equalizes back to 45-50 degrees.

The Massachusetts Innovation Center in Fitchburg is currently heating an entire mill complex using geothermal systems of various sizes. You can view the proposal explaining the economic payoff of the installation here.

Another major geothermal installation in the Boston area will be at a retirement community in Dedham called NewBridge on the Charles. They plan to drill more than 400 wells, each 500 feet deep, using closed-loop piping. (Dedham Times, March 28, 2008, p. 14) See this TV news story about their plans.