GHP systems take advantage of the stable temperature beneath the surface of the earth by building a heat exchanger made of bore holes 200 to 500 feet deep, and connected by HDPE pipe. Water flows through these pipes to a heat pump inside the building, picking up heat from the ground in the winter and dumping heat into the ground during the summer. Heat pumps are similar to typical air conditioners but are more efficient and can both heat and cool. The heat pump then heats or cools the air and sends it through the duct system inside the building. A GHP system can also be designed to provide hot water.

According to the US Department of Energy, GHP systems can be between 300 percent and 600 percent efficient. A GHP system uses the constant temperature of the earth to heat and cool, while other technologies must use fossil fuel or electric power. This enables the heat pump to do up to six units of work for every unit of energy supplied. The bottom line: GHP will use 25-50% less energy than conventional systems. And lower your electric and natural gas bills.

The lifecycle costs of a GHP system will be significantly lower even though the upfront costs are sometimes higher. Because of the significantly reduced cost to operate and maintain a GHP system, it can provide a payback period of two to five years. There are also a variety of federal and state tax breaks, and utility incentive programs that can further reduce the cost of your GHP system.

GHP systems have been around for more than half a century and all of the technology used is very well understood; inputs and out puts are very predictable. Conventional systems are also well known, which means calculating the energy and operational savings of GHP is a simple matter of doing the math. EnLink will work with the architects and engineers designing your building to understand the advantages of GHP.

GHPs are many times more efficient than conventional, using 40 to 70 percent less energy to power the system. If your GHP system is powered by the local utility, you will dramatically reduce the amount of grid-based electricity you use. That reduces greenhouse gas emissions from power plants that supply your utility. Using renewable power from solar PV, wind or other sources completely eliminates greenhouse gases. For systems that make hot water, we usually replace a gas-fired boiler, further reducing greenhouse gas emissions, and eliminating of local source of air pollution. GHP systems can also make significant reductions in water use by eliminating the need for the cooling towers used by some HVAC system

The underground heat exchanger sometimes needs to spread out over a large area of land, depending on how much cooling and heating capacity is required by the building. Often it can be built under a parking lot, a landscaped area or a playground area, as in the case of schools. We have even built systems that go under the footprint of the building itself. And all of the heat exchanger and the piping that leads to the building are underground, out of sight and out of the way.

The heat exchanger is made of high density poly-ethylene piping, which usually carries a 50 year warranty (It can often outlast the building itself). There are only a few mechanical components to system, all of which are located underground or inside, away from effects of weather or vandalism, resulting in a longer life span.

The heat pump itself is small relative to other technologies, so it takes up less space in the mechanical room inside the building. GHP systems are relatively quiet, and add little or no noise to the system.

Heat pumps can deliver higher volumes of hot or cold air than conventional systems, which helps eliminate uneven air distribution. Larger systems use multiple heat pumps, allowing localized temperature control within the building. Simultaneous heating and cooling are also possible. The distribution system of a GHP system is the same as a conventional HVAC.

Virtually any type of building can use GHP. However, there must be enough ground area including the building footprint, to build the proper size heat exchanger. GHP has been used in moderate high rise buildings, schools, office buildings, single family homes, apartments and condos, museums, prisons, military facilities and many other types of buildings. In many cases, GHP can also be used in retrofit projects.

No. GHP systems will not affect trees, grass or bushes. They are deep enough underground so that they are well out of the way. In designing the heat exchanger, care must be taken to avoid underground utilities, pipelines and other buried systems, but this is standard construction practice.

Below is a list of questions that should be asked when considering a geothermal heat pump system:

The answers to these questions will inform you on installation costs and system savings, the level of difficulty for installation, and the strength of your motivation behind the green technologies installation. All these questions will allow you to make an informed decision whether a GHP system is the right choice for you.

There are four classifications of GHP systems; vertical ground source, horizontal ground source, surface water source, and ground water (well) source. The ground water source system is an open loop system, and the others are all closed loop systems. The ground source systems involve either vertically or horizontally buried piping. The surface water source involves coiled piping placed over eight feet deep in lakes or ponds. The ground water source systems use well or surface waters that run directly through the system.

Choosing the best system for you will depend on a number of factors:

• The climate of the region – How much heating and cooling power will you need?
• The type of building – Is it a single family home, a school, an office building? Each use has different code requirements and special issues to deal with.
• The amount of land available – GHP systems do need a significant ground area for the heat exchanger.
• The geological properties of the land – How much heat can the soil or rock absorb and give off. This can differ by region and type of geology.
• The proximity of waters – If you want to do a water-based system, you need to have water nearby.
• Local installation costs – Local labor and materials costs can have a significant impact on the cost.

In general the most efficient and cost effective system (over the full lifecycle) will be a vertical loop GHP system. The majority of GHP systems in the United States are vertical-loop GHP.