Geothermal heating
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Geothermal heating is a method of heating and cooling a building. It takes advantage of the natural stable warmth stored in the earth. Normally the earth temperature is around 12.8 ºC (55 °F) at depths of 3 m (10 ft). In climates warmer than 12.8 ºC, this can be used to cool a building, and in colder climates it can be used for warmth. This is accomplished by one of a number of methods. A heat pump uses the extracted water or transfer fluid as a heat source in winter and a heat sink in summer. Some heat pumps provide heating and cooling via forced air distribution, and others through the heating (or chilling) of water for radiant type systems. Some systems are used to heat domestic hot water.
Types of geothermal systems:
- Closed Loop. Loops of pipe are buried at a depth of 2 m (6 ft) or greater in the ground. Pipes are placed horizontally (buried in trenches) or buried in deep, vertically-drilled holes, often 60 m (200 ft) or greater below ground level. Water and antifreeze (or other transfer fluid) are circulated through the heat exchanger (heat pump) and back out through the loops continuously. Some closed loop systems bypass a portion of their working fluid with a thermostat to keep the source temperature stable.
- Open Loop. Pipes draw water from a nearby water well or a shallow body of water. Once this water passes through the heat pump, it is released back to its source, generally as far from the intake as possible.
Geothermal heating is one of the most efficient ways to heat a building, but it can have high initial costs. If you have sufficient area, the initial cost can be minimized by using a horizontal loop system. If you have limited space, than the cost rises as you need to drill wells deep enough into the earth to take advantage of the earth's temperature. It also has ongoing costs for the electricity to power the fluid circulation pump and the heat pump compressor. Geothermal heating is much more efficient than air heat pumps and other supplemental electric heat used in warmer climates. It has the added benefit that it requires no burning of fossil fuels at the heating site, as opposed to systems that use natural gas or heating oil fired furnaces. Although, if coupled with a traditional natural-gas burning heater, the geothermal loop will dramatically reduce the amount of fuel needed to achieve a comfortable building temperature.
Geothermal cooling is much more efficient than traditional air conditioning units since it is only exchanging heat with ground temperatures. The amount of electricity needed to circulate the heat-transfer fluid and also run the air-circulation fan is significantly less than the amount of electricity needed to run the compressor of a traditional air conditioner. Since the ground temperature at a depth of 3 m (10 ft) is about 12.8 °C (55 °F) no additional cooling after the geothermal loop is typically needed to achieve a comfortable building temperature.
CASE is a program at Northside College Prep in Chicago Illinois. They are considering using geothermal energy to heat the school.
