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What is Geothermal Energy?


Human beings have used geothermal energy in North America for at least 10,000 years. Specifically in the United States, geothermal energy began to heat structures in the late 1800s (U.S. Department of Energy). In 1948 an Ohio State professor developed the first geothermal heat pump (GHP) for use in a residence. In 1978 the first modern GHP home in Oklahoma was created, and in 1982 the first commercial closed-loop system was created.


Geothermal energy is simply energy derived from heat in the interior of the earth. Just a few feet underground, the temperature stays around 50° to 70° degrees all year-round. During the winter, a geothermal energy system absorbs this extra heat from the earth and transfers it into your home or office. During the summer, the system takes heat from the indoors and moves it back underground.

How It Works

Geothermal systems get most of their energy from the consistent temperature of the earth. In our northern climate, the earth remains a constant 50 to 60 degrees year round.
In the winter time, this heat is absorbed by the loop system and carried into the geothermal furnace where it is compressed to a higher temperature. The result is a warm and comfortable home.
In the summer time, the process is reversed. The warmth of the air in the home is absorbed by the geothermal furnace and deposited into the cooler earth through the loop system. The result is a cool, dehumidified, comfortable home.
While heating and cooling the home, some geothermal furnaces can capture excess heat and use it to heat hot water for your domestic use.
Geothermal systems includes three principal components:

  • Geothermal earth connection
  • Geothermal heat pump
  • Geothermal heat distribution

Geothermal Earth Connection

A series of pipes, commonly called a “loop,” are buried in the ground near your home, either vertically or horizontally. This loop circulates fluid (water, or a mixture of water and antifreeze) that absorbs heat from, or exudes heat to, the soil, depending on whether the immediately surrounding air is colder or warmer than the soil.

Geothermal Heat Pump

In heating mode, heat is extracted from the fluid in the earth connection by the geothermal heat pump and distributed to the home – typically through a system of air ducts. Cooler air from the building is returned to the geothermal heat pump, where it cools the fluid flowing to the earth connection. The fluid is then re-warmed as it flows through the earth connection.
In cooling mode, the process is reversed. The relatively cool fluid from the earth connection absorbs heat from the building and transfers it to the ground.

Geothermal Heat Distribution

Most residential geothermal systems use conventional ductwork to distribute hot or cold air and to provide humidity control.