Geothermal heating and cooling systems rely on the fact that the earth’s temperature just below the surface remains relatively constant independent of the air temperature above the surface. This means that during the winter the earth’s temperature is warmer than the air temperature and during the summer it is cooler. This is a type of renewable energy and so is more sustainable than burning fossil fuels for heating or cooling. However, a geothermal system requires electricity to run, so, although more energy efficient, the system itself is not completely sustainable.
The Geothermal system uses a fluid, like water, to help with heat exchange. The water flows from the building through pipes into the ground, where the heat exchange occurs and then flows back into the building. When the building needs cooled, the water is already warm from the building’s temperature; it flows into the ground where the heat from the water is lost to the cooler surrounding surfaces. The water flows back into the building where the mechanical part of the system uses the temperature from the cooler water and using an air circulating system cools the building. During cooler months, the water is cooler and pulls heat from the surrounding warmer surfaces as it is pumped through the ground and back into the building. The warmer water is then used to heat the building with the air circulation system.
Since the mid-1990s, for example, Mercyhurst has been a regional pioneer in demonstrating the environmental and financial benefits of geothermal heating and cooling, which uses the constant temperature of the earth as a renewable energy source and then uses electricity to distribute the temperature by air throughout a building to either heat or cool. This form of geothermal heat exchange produces an average of 50-70% fewer carbon emissions.