How Geothermal Works
Geothermal heating and cooling systems are the most efficient and environmentally friendly systems on the market today. These systems work differently than conventional systems by taking advantage of the sun’s solar energy that is absorbed and stored by the earth. At a depth of 20 feet the ground maintains a fairly constant temperature of ranging from 45 to 77 degrees F depending on your region of the United States.
Pipes in the ground circulate a water solution and carry energy to the heat pump in the winter for heating and remove heat from the building into the ground in the summer. Forced air or low temperature hydronic systems distribute geothermal heating and air conditioning. Most systems use electric heat pumps capable of increasing the ground’s thermal energy in the winter and concentrating and depositing the a building’s thermal energy into the relatively cool ground in the summer when air conditioning.
The Heart of the System: Geothermal Earth Loops
A vertical loop is used mainly when land area is limited, bedrock is close to grade, or in many retrofit applications of existing homes. A drilling rig is used to bore holes to a depth of 150 to 450 feet. A long U-shaped coil of geothermal HDPE pipe is inserted into the bore holes. The holes are then grouted to help with thermal conductivity and to prevent mixing of aquifers.
A pond loop is an option if a large body of water is available within approximately 100 feet of the home. A minimum of 1/2 acre of surface area and a 10 to 12 foot deep pond or lake is usually adequate to support the average home. The system uses a series of geothermal HDPE pipe coils typically 300 to 500 feet in length. The coils are placed in and anchored at the bottom of the pond or lake.