There are basically four types of GHPs (click on the thumbnails to view larger):

• Horizontal
• Vertical
• Pond/lake (these three are closed-loop systems)
• and open-loop systems

Horizontal: This is generally most effective for new-construction, residential installations. The most common layouts use either two pipes with one buried at six feet and one at four feet or two pipes buried side-by-side at five feet

Vertical: This is often used by comercial buildings when the land area that is required for horizontal GHPs isn’t feasible, and when the soil is too shallow for trenching. Four inch holes are drilled twenty feet apart and one hundred to four hundred feet deep; pipes that are connected to horizontal pipes are dropped into these holes. The horizontal pipes are connected to the heat pump in the building. This type of GHP minimizes disturbance on existing landscaping.

Pond or Lake: Of course this type of GHP is used only when there is an adequate body of water nearby. If that is the case, this can be the cheapest option. The pipes are coiled at least eight feet under the surface of the water to prevent them from freezing. The volume, depth, and quality of the body of water are all factors you have to consider when looking at this type of heat pump.

Open-loop System: This uses a well or surface body water as the heat exchange fluid that circulates through the pump system. After it has circulated the water is returned to the ground through another well. This option is only possible when there is relatively clean water in the area and local regulations are met.

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Geothermal heat pumps (GHPs), also know as GeoExchange, ground-source, earth-coupled, or water-source heat pumps, have been used since the late 1940’s. This kind of heat pump uses the constant temperature of the earth as the exchange medium. GHPs are more efficient in colder climates than air-source heat pumps. They have a much higher efficiency than air-source heat pumps too, and can, if properly equipped, supply the house’s hot water. Because they are underground they are not susceptible to vandalism, and they are extremely quiet. GHPs control indoor humidity making them very effective in humid climates.

The main reason GHPs are not more widely used than other heat pumps is the high cost. They are quite expensive, but mainly because they are so difficult to install. The average cost is about $2500 per ton. However, GHPs are gaining popularity; approximately 40,000 GHPs are installed in the US every year. Typical anual energy savings are 30-60% which means that it is possible to recoup the initial investment in 2-10 years just through lower utility bills!

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