Guide to geothermal heat pumps

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Guide to Geothermal Heat Pumps
Geothermal heat pumps are among the most efficient and comfortable heating and cooling technologies available because they use the earth’s natural heat to provide heating, cooling, and often, water heating.

About Geothermal Heat Pumps
While many parts of the country experience seasonal temperature extremes – from scorching heat in the summer to sub-zero coldin the winter – a few feet below the earth’s surface the ground remains a relatively constant temperature. The natural ground temperature is cooler than the natural air temperature in summer, and warmer than the natural air temperature in winter. While the margin of variation is small, seasonal changes in ground temperature give geothermal heat pumps a dependable and permanent wintertime heatsource and summertime heat sink. Geothermal heat pumps, also known as ground source heat pumps, geoexchange, water-source, earth-coupled, and earth energy heat pumps, take advantage of this resource and represent one of the most efficient and durable options on the market to heat and cool your home. Many heating, ventilation, and air conditioning systems use some sort of heat pump for heating andcooling.

Geothermal heat pump systems, consisting of the heat exchanger (left) and the heat pump (right), heat and cool a home by transferring heat to and from the earth.

How Geothermal Heat Pumps Work
Using a heat exchanger, a geothermal heat pump can move heat from one space to another. In summer, the geothermal heat pump extracts heat from a building and transfers it to the ground forcooling. In winter, the geothermal heat pump takes natural heat from the ground and transfers it to the home or building for heating. Installing a geothermal heat pump system can be the most cost-effective and energy-efficient home heating and cooling option. Geothermal heat pumps are a particularly good option if you are building a new home or planning a major renovation to an existing home byreplacing, for example, an HVAC system.

Geothermal vs. Air-Source Heat Pumps
While geothermal heat pumps operate similarly to the far more common air-source heat pump (ASHP), geothermal heat pumps are substantially more energy-efficient than even ASHPs because they take advantage of the relatively consistent ground temperatures, which are far more uniform than air temperatures. Geothermal systemscan reduce energy consumption by approximately 25% to 50% compared to air source heat pump systems. Geothermal heat pumps reach high efficiencies (300%-600%) on the coldest of winter nights. As with any heat pump, geothermal heat pumps are able to heat, cool, and, if so equipped, supply the house with hot water. Some models of geothermal systems are available with two-speed compressors andvariable fans for more comfort and energy savings. Relative to ASHPs, they are quieter, last longer, need little maintenance, and do not depend on the temperature of the outside air.
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A dual-source heat pump combines an ASHP with a geothermal heat pump. These appliances simultaneously provide the consumer with a more efficient alternative to theASHP, and a more affordable alternative to the geothermal heat pump. Dual-source heat pumps have higher efficiency ratings than air-source units, but are not as efficient as geothermal units. The main advantage of dual-source systems is that they cost much less to install than a single geothermal unit, and work almost as well.

systems can be more expensive, but they use less land and alsominimize disturbance to the existing landscape.
• Pond/Lake: If the site has an

adequate water body, this may be the least expensive option. A supply line pipe runs underground from the building to the water and coils into circles at least eight feet under the surface to prevent freezing. The coils should only be placed in a water source that meets minimum volume, depth, and quality criteria....
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