Geothermal Heat Pumps
http://www.toolbase.org/Technology-Inve ... heat-pumps
Use the natural heat storage capacity of the earth or ground water to provide energy efficient heating and cooling
Drawing shows how a geothermal heat pump draws warm air out of the house and disperses it beneath the ground.
Geothermal heat pumps (GHPs) are a relatively new technology that can save homeowners money. These ground-source heat pumps use the natural heat storage capacity of the earth or ground water to provide energy efficient heating and cooling. GHPs should not be confused with air-source heat pumps that rely on heated air.
Geothermal heat pumps use the relatively constant temperature of the ground or water several feet below the earth's surface as source of heating and cooling. Geothermal heat pumps are appropriate for retrofit or new homes, where both heating and cooling are desired. In addition to heating and cooling, geothermal heat pumps can provide domestic hot water. They can be used for virtually any size home or lot in any region of the U.S.
A geothermal heat pump system consists of indoor heat pump equipment, a ground loop, and a flow center to connect the indoor and outdoor equipment. The heat pump equipment works like a reversible refrigerator by removing heat from one location and depositing it in another location. The ground loop, which is invisible after installation, allows the exchange of heat between the earth and the heat pump.
Geothermal heat pumps can be open- or closed-loop. Open-loop systems draw well water for use as the heat source or heat sink, and after use, return the well water to a drainage field or another well. Closed-loop or earth-coupled systems use a water and antifreeze solution, circulated in a ground loop of pipe to extract heat from the earth.
Ground loops can be installed in a vertical well or a horizontal loop. Vertical wells are usually more expensive and used where space is limited. The length of loop pipe required will vary with soil type, loop configuration, and system capacity. Loop length can range from 250 to 1,000 feet per ton of capacity.
Special heat pump features can include variable speed blowers and multiple-speed compressors. These features can improve comfort and efficiency in areas where heating and cooling loads are quite different. Add-on features include the capability to produce hot water.
Desuperheaters can be added to supplement the production of domestic hot water when there is a demand for space heating or cooling. These devices make use of excess heat during the cooling cycle and use some of the heat during the heating cycle to supplement hot water production. Dedicated water heaters can be added which operate whenever there is a demand for hot water.
Geothermal heating can be more efficient than electric resistance heating. These systems are also typically more efficient than gas or oil-fired heating systems. They are more energy efficient than air-source heat pumps because they draw heat from, or release heat to, the earth, which has moderate temperatures year round, rather than to the air (which is generally colder in winter and warmer in summer than the earth, resulting in less effective heat transfer).
Geothermal heat pumps have demonstrated energy savings over air heat pumps because they extract energy from the constant temperature of the earth (via a water pipe buried in the earth) to condition the air in a home. In a sense, geothermal is a partially-renewable form of energy.
Ease of Implementation
Kind of difficult
Geothermal heating and cooling equipment is readily available in the marketplace and can be installed by any qualified HVAC contractor. The process is two-fold in that it involves installing the indoor unit and method of delivery, whether forced hot air or hydronic, and the outside pipe loop. Loop installation can be planned concurrently with other construction activities, so the overall construction schedule should not be affected by choice of system. Some loops will require an additional permit. Geothermal equipment can be installed with equal ease in both new construction and remodeling projects.
Initial Cost Greater than comparable products
The initial cost of a geothermal heat pump system varies greatly according to local labor rates, lot geology and size, type of system installed, and equipment selected. So, GHP systems are more costly to install than air source heat pumps. For either system, the cost of installed ducts should be identical. Equipment costs can be 50-100% more expensive for a geothermal heat pump system when the circulating pump, indoor tubing, and water source heat pump are considered. This 50-100% premium translates to $1,000 - $2,000 for the equipment that supplies a 3-ton system.
The ground loop is generally the most expensive component of a geothermal heat pump system and is highly dependent on local labor rates and drilling conditions. An installed ground loop stubbed out in a home can cost between $1,000 and $3,000 per installed ton. Overall, one could expect to pay between $4,000 and $11,000 more for a 3-ton GHP system than for an air source heat pump system.
Operational Cost Less than comparable products
Geothermal heat pumps offer high efficiency and low operating cost. According to the EPA, geothermal heat pumps can save homeowners 30 to 70 percent on heating and 20 to 50 percent on cooling costs over conventional systems. Reports by builders who monitor their in-place systems indicate heating and cooling savings between $358 and $1,475 annually.
Codes for well drilling apply to vertical ground loop installation. Local codes may restrict the type of antifreeze that can be used in the ground loop.
Carl Franklin Homes: The Vista at Kensington Park, Dallas, Texas
Keith Swilley House, Panama City, FL
Bob Schmitt Homes, Ohio
Geothermal heat pump manufacturers should be contacted to obtain qualified installers who have been trained on installation procedures.
Geothermal equipment carry warranties similar to its heat pump counterparts – 2 - 5 years on the equipment and lifetime on the heat exchanger. Exceptions are made for especially corrosive water or inadequate anti-freeze levels, so regular maintenance is required. The ground loop should not require replacement for the life of the home.
Geothermal heat pumps offer high efficiency and low operating cost. According to the EPA, GHPs can save homeowners 30 to 70 percent on heating and 20 to 50 percent on cooling costs over conventional systems. GHPs provide a high level of occupant comfort. There is a potential for utility bill savings, and many local utility companies provide incentives for investing in GHPs.
The initial cost of a geothermal heat pump system varies greatly according to local labor rates, geological profile, type of system installed, and equipment selected. The initial cost of GHP systems does come at a premium when compared to air source heat pump systems. For either system, the cost of installed ducts should be identical. Equipment costs can be 50-100% more expensive for a GHP system when the circulating pump, indoor tubing, and water source heat pump are considered. This 50-100% premium translates to $1000 - $2000 for a 3-ton system.
The ground loop is generally the most expensive component of a geothermal heat pump system and is highly dependent on local labor rates and drilling conditions. An installed ground loop stubbed out in a home can run betwee $1000 and $3000 per installed ton. Overall, one could expect to pay between $4000 and $11000 more for a turnkey 3 ton GHP system than for an air source heat pump system. Many consumers justify this initial investment with the savings they expect to realize on their heating and cooling bills over time.
Disclaimer: The information on the system, product or material presented herein is provided for informational purposes only. The technical descriptions, details, requirements, and limitations expressed do not constitute an endorsement, approval, or acceptance of the subject matter by the NAHB Research Center. There are no warranties, either expressed or implied, regarding the accuracy or completeness of this information. Full reproduction, without modification, is permissible.
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