Zone Heating and Cooling: These systems provide excellent "zone" space conditioning. With this, different areas of the building can be heated or cooled to different temperatures simultaneously. For example, Geothermal Heat Pump systems can easily move heat from computer rooms (which need constant cooling) to the perimeter walls for winter heating in commercial buildings. School officials like the flexibility of heating or cooling just auditoriums or gymnasiums for special events-rather than the entire school.
Durability: Because Geothermal Heat Pump systems have relatively few moving parts, and because those parts are sheltered inside a building, they are durable and highly reliable. The underground piping often carries warranties of 25 to 50 years, and the GHPs often last 20 years or more.
Reduced Vandalism: Geothermal Heat Pumps usually have no outdoor compressors or cooling towers, so the potential for vandalism is eliminated.
Installation: Because of the technical knowledge and equipment needed to properly install the piping, Geothermal Heat Pump system installations are not a do-it-yourself project. To find a qualified installer, call your local utility company, the International Ground Source Heat Pump Association, or the Geothermal Heat Pump Consortium for their listing of qualified installers in your area. Installers should be certified and experienced. Ask for references, especially for owners of systems that are several years old, and check them.
How GHPs Are Labeled: Geothermal Heat Pump efficiency is rated in two ways. The Coefficient of Performance, or COP, and Energy Efficiency Rating, or EER, are measures of heating and cooling efficiency, respectively.
Manufacturers of high-efficiency geothermal heat pumps voluntarily use the EPA ENERGY STAR® label on qualifying equipment and related product literature. If you are purchasing a geothermal heat pump and uncertain whether it meets ENERGY STAR® qualifications, ask for an efficiency rating of at least 2.8 COP or 13 EER.
Financing a Geothermal Heat Pump System: Many geothermal heat pump systems carry the U.S. Department of Energy (DOE) and EPA ENERGY STAR® label. ENERGY STAR®-labeled equipment can now be financed with special ENERGY STAR® loans from banks and other financial institutions. The goal of the loan program is to make ENERGY STAR® equipment easier to purchase, so ENERGY STAR® loans were created with attractive terms. Some loans have lower interest rates, longer repayment periods, or both. Ask your contractor about ENERGY STAR® loans.
Homeowners should check with their utility and ask if they offer any rebates, financing, or special electric rate programs. Another way to help finance the purchase of a GHP system is to roll the cost into an "energy efficient mortgage" that would cover this and other energy-saving improvements to the home. Banks and mortgage companies can provide more information on these loans. These mortgages can create positive cash flow from the start. Say that installing a geothermal heat pump system adds $25 per month to the mortgage. However, because a Geothermal Heat Pump system is so efficient, it will save more than $30 per month in energy costs.
Install a Geothermal Heat Pump and Forget about High Energy Bills: With a geothermal heat pump system, you'll experience greater indoor comfort, lower energy bills, and a system that provides heating, cooling, and hot water for many trouble-free years to come.
How Does a Geothermal Heat Pump System Work?: The ground heat exchanger in a Geothermal Heat Pump system is made up of a closed or open loop pipe system. Most common is the closed loop, in which high density polyethylene pipe is buried horizontally at 4-6 feet deep or vertically at 100 to 400 feet deep. These pipes are filled with an environmentally friendly antifreeze/water solution that acts as a heat exchanger. In the winter, the fluid in the pipes extracts heat from the earth and carries it into the building. In the summer, the system reverses and takes heat from the building and deposits it to the cooler ground.
The air delivery ductwork distributes the heated or cooled air through the house's duct work, just like conventional systems. The box that contains the indoor coil and fan is sometimes called the air handler because it moves house air through the heat pump for heating or cooling. The air handler contains a large blower and a filter just like conventional air-conditioners.
Installation Options: The installation of a Geothermal Heat Pump system is not for the do-it-yourselfer. Contact local utilities, IGSHPA, and the GHPC for references on licensed and experienced installers. In addition, many states have Heat Pump Councils which may provide additional referrals.
There are four basic types of ground loop systems. Three of these-horizontal, vertical, and pond/lake-are closed-loop systems. The fourth type of system is the open-loop option. Which one of these is best depends on the climate, soil conditions, available land, and local installation costs at the site. All of these approaches can be used for residential and commercial building applications.
Horizontal: This type of installation is generally most cost-effective for residential installations, particularly for new construction where sufficient land is available. It requires trenches at least four feet deep. The most common layouts either use two pipes, one buried at six feet, and the other at four feet, or two pipes placed side-by-side at five feet in the ground in a two-foot wide trench. Or, the Slinky method of looping pipe allows more pipe in a shorter trench, which cuts down on installation costs and makes horizontal installation possible in areas it would not be with conventional horizontal applications.
Figure 33: Horizontal GHP
Vertical: Large commercial buildings and schools often use vertical systems because the land area required for horizontal loops would be prohibitive. Vertical loops are also used where the soil is too shallow for trenching, and they minimize the disturbance to existing landscaping. For a vertical system, holes (approximately four inches in diameter) are drilled about 20 feet apart and 100 to 400 feet deep. Into these holes go two pipes that are connected at the bottom with a U-bend to form a loop. The vertical loops are connected with horizontal pipe (i.e., manifold) placed in trenches, and connected to the heat pump in the building.
Figure 34: Vertical GHP System
Pond/Lake: If the site has an adequate water body, this may be the lowest cost option. A supply line pipe is run underground from the building to the water and coiled 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.
Figure 35: Pond/Lake GHP System
Open-Loop Systems: This type of system uses well(s) or surface body water as the heat exchange fluid that circulates directly through the GHP system. Once it has circulated through the system, the water returns to the ground through the well, a recharge well, or surface discharge. This option is obviously practical only where there is an adequate supply of relatively clean water, and all local codes and regulations regarding groundwater discharge are met.
Figure 36: Open-Loop GHP System
Lincoln Public Schools: In Lincoln, Nebraska, not only is the school district benefiting from the savings of GHP systems, but the taxpayers are, too. With cooperation from Lincoln Electric Systems and Lincoln Public Schools, four elementary schools recently installed Geothermal Heat Pump systems. The heating and cooling costs are about $144,000 a year less (for 1996-1997) than they would have been if those schools installed more traditional heating and cooling systems. These savings will reach about $3.8 million over just 20 years, allowing for other capital improvements to be realized. Compared to natural gas HVAC systems (air-cooled, variable air volume systems) that were installed in two other schools at the same time, the schools had a total energy cost savings of 57%. There were also 42% and 20% reductions in electrical demand and electrical energy consumption, respectively. Not only will the school district taxpayers save about $3.8 million over the next 20 years, but the GHPs also help reduce peak demand for electricity compared to alternative systems.