Geothermal Heat Pumps

A geothermal heat pump or ground source heat pump (GSHP) is a central heating and/or cooling system that transfers heat to or from the ground. It uses the earth as a heat source (in the winter) or a heat sink (in the summer). This design takes advantage of the moderate temperatures in the ground to boost efficiency and reduce the operational costs of heating and cooling systems. The temperature beneath the upper 6 meters (20 feet) of earth’s surface maintains a nearly constant temperature between 10 and 16°C (50 and 60°F). A ground source heat pump exchanges heat with the ground. This is much more energy-efficient because underground temperatures are more stable than air temperatures through the year.

What is a geothermal heat pump?

closedloopsystemGeothermal heating and cooling is a wonderful concept. Geothermal heating systems work in a very unique way to naturally provide a heat or cooling source to your home. A geothermal or ground source heat pump is an electrically powered device that uses the natural heat storage ability of the earth and/or the earth’s groundwater to heat and cool your home.

Geothermal heating involves a larger startup cost than most home heating remedies; however, based on its environmental friendliness and its lack of fossil fuel usage, it ends up being more efficient in comparison to the air source heat pump in the long run.

GHP use the earth as a heat sink in the summer and a heat source in the winter, and therefore, rely on the relative warmth of the earth for their heating and cooling production. Through a system of underground pipes, they transfer heat from the warmer earth or water source to your home in the winter, and take the heat from your home in the summer and discharge it into the cooler ground. Therefore, GHPs don’t create heat—they move it from one area to another.

How does a geothermal heat pump work?

ground-source-heat-pumpThe ground source heat pump system is made up of a closed-loop or open-loop pipe system. It works on a simple premise: the earth below the frost line (usually about four feet down) is a constant temperature of about 50 degrees year-round. Heat can be taken from the ground and transferred through a heat pump to the air in your home during the winter. Heat can also be transferred back into the ground during the summer to cool your home.

Installation Options

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Closed-Loop System

The loops of plastic piping can be installed either vertically or horizontally, depending on the size and shape of your yard and the amount of existing landscaping and soil conditions. The amount of piping needed depends on the size of your home and the loop configuration.

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Horizontal System

This type of installation is generally most cost-effective for residential installation, particularly for new construction where sufficient land is available. This system requires trenches at least four to six feet deep. There are a variety of techniques for placing the piping in the ground. One method is to utilize “slinky-style” techniques by tying the coils together. An alternative option might be to loop the pipe back over itself, covering each length with soil.

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Vertical System

This type of installation is more common with commercial buildings and schools due to the limited amount of land that is available. Vertical loops are also used where the soil is too shallow for trenching. If you have limited space or soil issues, this may be the solution for you. Installation of a vertical loop system requires a borehole about 4 to 10 inches in diameter. This is drilled near your home. The depth of the hole is between 50 and 400 feet, depending on what is encountered during the drill. The size of the system you require will determine how many holes will need to be drilled. All of the holes must be about 8 to 20 feet apart. Two pipes are then inserted and connected at the bottom with a U-bend to form the loop. This is then connected with a horizontal pipe, which connects to the heat pump in your home. The hole is filled with a special grout or sealing material and is capped.

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Pond/Lake System

If the home has an adequate body of water, this system may be the one system with the lowest cost of all the options. A water supply line is run underground from the house 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 the minimum volume, depth, and quality criteria. The water resource must be a relatively clean water supply.

The basic elements of the system include:

  • Buried loops of piping (the ground loop).
  • Biodegradable liquid antifreeze.
  • A pump module to circulate the antifreeze.
  • A heat pump.

The most common system is the closed-loop system, in which high density polyethylene pipe is buried horizontally at 4 to 6 feet deep or vertically at 50 to 400 feet deep. These pipes are filled with an environmentally friendly antifreeze/water solution that acts as a heat exchanger. The pipes are connected to the circulating pump inside your home. The pump module circulates the mixture of the water and biodegradable antifreeze through the buried loops, and the liquid mixture absorbs heat from the ground as it flows thru the loop. The heat pump takes heat from the liquid mixture and transfers it to the air, which is circulated in your home. To cool your home in the summertime, the system simply works in reverse.

BENEFITS OF A GEOTHERMAL SYSTEM

Green Technology: It reduces pollution. Today there are more than 1,000,000 geothermal heat pump installations in the United States. The impact of the current use of ground source heat pumps is equivalent to: taking close to 1,295,000 cars off the road, planting more than 385 million trees, and reducing U.S. reliance on imported fuels by 21.5 million barrels of crude oil.

Safe: There are no flames or gases. Ground source heat pump systems are safe and protected. With no exposed equipment outdoors, children and pets cannot injure themselves or damage exterior units. Ground heat pumps have no open flame, flammable fuel, or potentially dangerous fuel storage tanks. Because ground heat pumps don’t burn gases, dangerous carbon monoxide in your home is no longer a worry.

More Efficient: The biggest benefit of GHPs is that they use 25 to 50% less electricity than conventional heating or cooling systems.

Low Operating and Maintenance Costs: Geothermal systems have one of the lowest relative operating and maintenance costs of any HVAC system available. Their annual operating costs are often lower than conventional systems, such as built-up air handlers, rooftop units, or VAV applications. Maintenance and service of these systems are easy and do not require specialized training. This gives owners more options for maintaining and servicing their equipment.

Environmentally Responsible: The Department of Energy (DOE) applauds geothermal systems as being among the most environmentally responsible heating/cooling systems available today. The ground loop is completely sealed to eliminate the risk of soil and aquifer contamination. In addition, some available units use HFC-410A or HFC-407C refrigerants with no ozone depletion potential. This supports the Montreal Protocol and the elimination of ozone depleting substances. The high efficiency of geothermal systems helps reduce the requirement for utilities to burn fossil fuels, which in turn decreases CO2 emissions to the environment. Rebate programs, available through many utilities and government agencies, are a testament to the outstanding efficiency of geothermal systems.

Residential Installation: A GSHP (ground source heat pump) system can be installed in a residential structure of any size anywhere, whether it is a single-family or multi-family residence. GSHPs can be installed on almost any size lot—under lawns, landscaped areas, driveways, or even the house itself—and in new construction or existing home retrofits.

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