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GEOTHERMAL - How It Works
Portions of technical content courtesy of WaterFurnace International
Geothermal Vertical Loop Diagram Vertical Closed Loop:
This system is used when yard space is limited, the Earth is rocky close to the surface and when retrofitting applications where the need for minimum disruption to landscape is desired.  A pair of pipes with a special U-bend assembly at the bottom is placed into bore holes from 100 to 400 feet deep.
Geothermal Open Loop diagram
Ground Water Open-Loop:
Well water from an underground aquifer is pumped through the geothermal heat pump and then returned to the aquifer or discharged to the surface.
Geothermal Horizontal loop diagramHorizontal Closed-Loop:
A piping array is installed in trenches cut 3 to 5 feet deep and hundreds of feet in length.  A typical horizontal loop is 400-600' long per ton of heating and cooling capacity.  This system is the easiest to install while the home or building is under construction.
A closed loop system can be installed vertically, horizontally or in a pond or lake. The fluid in the loop that carries the heat or expels the cold can be water or an environmentally friendly anti-freeze. The loop is in the ground out of site and is made of a high-density polyethylene (tough plastic) material that allows for heat to pass through efficiently. (Loops should be installed by an IGSHPA certified or a professional who follows procedures established by IGSHPA).
Geothermal Pond Loop diagramSurface Water Closed-Loop:
This is the most economical system if a body of surface water is nearby.  Fluid circulates through a piping array that is submerged under the surface.  This system is recommended only if the body of water never goes below 6-8' at its lowest level.  There is no impact on the aquatic system.
Geothermal heating and cooling is an exchange of heat with the earth.  The ground under the typical building site has a tremendous ability to store and release heat.  A geothermal system is a machine designed to use this ability.  There is a basic law of physics that states that it is more efficient to move heat that already exists than to make new heat from another form of energy.  Geothermal is a concept that puts this basic law to work for the advantage of property owners everywhere.

There are several ways to extract the heat from the earth.  The transfer of the Earth's energy (heat) is achieved by way of liquid (water or environmentally friendly anti-freeze), pipe (loop), heat exchanger and in most applications a well or multiple wells.










 











 

 

In the winter the Earth's heat is collected through a series of pipes, called a loop.  The loop is either installed below the surface of the ground or in a pond or lake. Fluid in the loop carries the heat to the building and into a heat exchanger.  The heat exchanger concentrates the energy and releases it into the building at a higher temperature.  In the summer the process is reversed; the excess heat is drawn from the home or building and expelled into the loop and absorbed by the Earth.  This process is very similar to the way a refrigerator works, wherein cooling is achieved by drawing heat from the interior of the refrigerator not by injecting cold air.

Open Loop System:

An open loop system takes ground water from an aquifer and is piped directly from the well into the home or building. The water is then pumped back into the aquifer via the same well or into a second well called a discharge well. This type of system is the easiest to install and most common in New England. Water carries the heat or expels the cold in this application; therefore an environmentally friendly anti-freeze is not necessary.

Standing Column System:

This system operates very similar to an open loop system. Water from the bottom of the well is circulated through the heat exchange unit in the home and returned to the top of the water column into the same well. Ground water must be plentiful for this application to work. If the water table is too deep, operating costs are high. Just like the open loop system water is the conductor of energy not anti-freeze.

Hot Water:

In addition to heating and cooling your home, Geothermal Exchange Technology also provides a home or building with hot water. A desuperheater, which is a small auxiliary heat exchanger that uses super heated gases from the heat pumps compressor to heat the water, is installed.

In the summer, when the exchange system is in the cooling mode, the desuperheater uses excess heat that would otherwise be expelled back into the loop. When running frequently in the summer hot water is obtained virtually free and in the winter months there is a substantial savings.


Geothermal systems are based on the nearly constant year-round ground temperature (approximately 50 degrees) of the earth.  Water is used to convey the energy from the earth into the piping.

Heating:

During the heating cycle, a geothermal system uses the earth loop to extract heat from the ground. As the system pulls heat from the loop it distributes it through either a conventional duct system as warm air or pipes and baseboard as hydronic heat. The same heat energy can also be used for a radiant floor system or domestic hot water heating.

Cooling:

In the cooling mode, a geothermal system air conditions the building by reversing the heating process. Instead of extracting heat from the ground, it is extracted from the building and either moved back into the earth loop, or used to preheat the water in a hot water tank. Once the heat is removed from the air, it is distributed through the duct system or piping in the building.