What Is Geothermal Heatng?
Geothermal heating is a system that moves heat into or out of the ground and/or groundwater to heat or cool a residence or commercial building. This heating system reduces the need for fossil fuels such as oil and gas and is therefore environmentally friendly. Geothermal energy is becoming a popular heating and cooling alternative.
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Earth-Energy Systems
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In a system that harvests geothermal energy, heat is removed from the ground through a liquid such as groundwater or an antifreeze solution, is upgraded by a heat pump and then transferred to indoor air. During the summer, heat is extracted from indoor air and transferred to the earth through the groundwater or antifreeze solution. A direct-expansion (DX) earth-energy system uses refrigerant in the exchanger rather than groundwater or antifreeze. Earth-energy systems can be designed for heating only or for heating with active or passive cooling.
The Components
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All earth-energy systems are composed of a circuit of underground piping outside the building and a heat pump inside. The outdoor piping system may be open or closed. An open system draws warm water from a deep well. The heat is extracted by the heat exchanger and the cooled water is then discharged into a stream or pond or back to the underground water body through a separate well.
Closed loop systems collect heat from the ground through a continuous loop of piping buried well below the frost line. Chilled antifreeze or refrigerant circulates through the piping and absorbs heat from the surrounding soil.
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Heating
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Heat picked up from the soil is brought back to the heat pump inside. A heat exchanger transfers the heat to a refrigerant that boils to become a low-temperature vapor. A reversing valve sends the vapor to a compressor that compresses the vapor, causing it to heat up. The reversing valve then sends the heated air to the condenser coil. Air is blown across the coil and forced through the building's ducting system to heat the structure. The now cooled refrigerant is returned to the heat exchanger and finally to the ground for process repetition.
Cooling
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In the cooling cycle, the refrigerant picks up heat from the house air and transfers it to the ground water or antifreeze mixture. The heat is then pumped into a body of water or return well (open system) or into the underground closed loop piping array. Earth-energy systems rely upon the stable air temperatures underground and the heat pump system located inside to provide continuous heat exchange regardless of the air temperature outside.
Installation
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In an open system, water must be above 40 degrees F year round to avoid freeze up of the heat exchanger. Water must be tested for particulate matter, acidity, iron content and hardness in order to avoid clogging.
The closed loop system may be installed horizontally or vertically, depending on lot size. DX systems require refrigeration-grade copper tubing, while all systems for antifreeze solutions require at least series 100 polyethylene or polybutylene piping with fused joints.
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References
- Photo Credit security and heating system image by Canakris from Fotolia.com
