The Future of Geothermal Energy
Geothermal energy has the potential to play a significant role in moving the United States (and other regions of the world) toward a cleaner, more sustainable energy system. It is one of the few renewable energy technologies that — like fossil fuels — can supply continuous, base load power. The costs for electricity from geothermal facilities are also declining. Some geothermal facilities have realized at least 50 percent reductions in the price of electricity since 1980. New facilities can produce electricity for between 4.5 and 7.3 cents per kilowatt-hour, making it competitive with new conventional fossil fuel-fired power plants.

Over the next decade, new geothermal projects are expected to come online to increase U.S. capacity to between 8,000 and 15,000 MW. As hot dry rock technologies improve and become competitive, even more of the largely untapped geothermal resource could be developed. In addition to electric power generation, which is focused primarily in the western United States, there is a bright future for the direct use of geothermal resources as a heating source for homes and businesses everywhere.

Additionally, most states provide rebates, tax incentives, or various combinations of the two for installing geothermal heating and cooling systems. To see what your state has to offer click the horizontal button above that states "Policies & Incentives by State."

How Geothermal Heating Systems Work

The heating process involves the extraction of heat energy from the ground, and moving it into the building. Transferring the heat from the earth to the building involves a cycle of evaporation, compression, condensation and expansion.

A refrigerant is used as the heat transfer medium. The heating cycle starts as cold, liquid refrigerant passes through a water-to-refrigerant heat exchanger and absorbs heat from the low temperature source (earth loop fluid or well water). The refrigerant evaporates into a gas as heat is absorbed.

The gaseous refrigerant passes through a compressor where the refrigerant is pressurized, raising its temperature to over 180 degrees F. The hot gas then circulates through a refrigerant-to-air heat exchanger where heat is removed as the cooler return air passes over it. Now heated, this warm air is delivered into the building by way of the blower and the duct system. Upon releasing its heat energy into the air, the refrigerant returns to the water-to-refrigerant heat exchanger where the process is repeated continuously during the heating process.

A by-product of the heating function is the production of hot water that is delivered to the water heater by way of a small pump. 

How Geothermal Cooling Systems Work

The cooling process involves the extraction of heat energy from the air in the building, and moving it into the earth.

Transferring the heat from the air in the building to the earth involves a cycle of expansion, condensation, compression, condensation and evaporation. A refrigerant is used as the heat transfer medium.

The cooling cycle starts as the compressor delivers refrigerant to the water-to-refrigerant heat exchanger. Heat from the refrigerant is absorbed by (rejected into) the low temperature source (earth loop fluid or well water) resulting in the refrigerant turning cold. The cold refrigerant passes through a refrigerant-to-air heat exchanger. As warm, humid air from the return air duct system is passed over the cold air coil, the air is cooled and dehumidified the returned into the building, cooling the space. The heat from the warm air that returns to the unit is absorbed by the cold refrigerant, turning the refrigerant into a hot gas. The hot refrigerant is returned to the compressor where the process is repeated continuously during the cooling process. A portion of the heat returning to the compressor (from the hot return air) is diverted to another refrigerant circuit that generates hot water and delivers it to the water heater by way of a small pump.


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