What is Geothermal?

There are three very different technologies – GeothermalGeoexchange and Air Exchange – that are often mistakenly lumped together under the term “Geothermal”. There is a great deal of difference between these technologies in terms of costs and performance.

GEOTHERMAL– Heat from the Core of the Earth

Heat from the Core of the Earth

Heat from the Ground

The term “GEOTHERMAL” translates into “heat from the ground”. But there are two very different sources of heat from the ground.

The term “geothermal” describes the specific technology that taps into the heat from the core of the earth. When the heat from the core rises to, or near the surface, it can be utilized to generate electricity. In this application the geothermal heat is generally used to power large generators to produce electricity.

“Geothermal” technology achieves an efficiency of about 75% and is impractical for heating and cooling residential or commercial buildings. So it is important not to confuse the limitations of “Geothermal” with the Geoexchange technology used for heating and cooling residential and commercial buildings.

GEOEXCHANGE – Heat from the Sun that is stored in the ground

The term “Geoexchange” is used to describe a system that taps into the heat from the sun that is stored in the ground.

The sun creates an average ground temperature of around 47 degrees in Minnesota. The earth absorbs 47% of the sun’s energy which provides over 500 times more energy than you could ever use to heat and cool a residential or commercial building.

In the winter a geoexchange loop field absorbs the heat from the ground and brings it into the house where it is distributed throughout the building. In the summer the heat is absorbed from the building and deposited into the loop field where it is absorbed by the ground. It is this exchange of energy between the building and the ground that gives Geoexchange its name.

By tapping into the stored energy of the sun, geoexchange achieves efficiencies of 400 to 600 percent. A geoexchange system can replace a fossil fuel system and is capable of meeting all of the heating and cooling needs of a home or commercial building.

AIR SOURCE HEAT PUMP (ASHP) – Heat from the Sun stored in the Air

heatpump_illustration Using air

Air Source Heat Pump

Another technology, Air Source Heat Pumps (ASHP), is not geothermal at all. It’s source of energy is the heat of the sun that is stored in the air in our atmosphere.

Because of the limited amount of heat in the air, an ASHP cannot replace a fossil fuel system. Therefore this technology is a way of supplementing your current heating and cooling system to reduce your costs.

In the winter, the ASHP draws heat from the outside air to provide heating. But since the amount of heat in the air rapidly depletes as temperatures drop, the ASHP is only capable of providing heat to around 25 degrees. Once it gets colder than that the ASHP will shut off and a fossil fuel system takes over.

In the summer time, the ASHP will draw air out of the house and dump it into the outside air. But as the outside air gets hotter, it becomes more resistant to absorbing the heat from the house. Therefore, during peak cooling times the unit is at its lowest efficiency.