Geothermal and geopressure as sources of energy
Geothermal energy is heat from the earth it provides a clean and renewable source of energy. Heat flowing from the earth’s interior is estimated to be equivalent to more than 40 million megawatts of power, and is considered renewable as the interior of the earth is expected to remain extremely hot for billions of years to come.
Once extracted, geothermal energy can be used directly, through heat pumps, to provide heating for homes and businesses or for industrial processes. It can also be used generate electricity, using a geothermal power plant. There are two main types of power plant; steam and binary.
Steam power plants
These plants use very hot steam and water resources. The steam is used to turn turbines which drive generators to produce electricity. Steam is the only significant emission from these plants. Whilst very small amounts of carbon dioxide, nitric oxide and sulfur are also emitted this is 50 times less than are emitted by traditional fossil-fuel power plants.
These plants use lower-temperature hot water resources. Hot water is passed through a heat exchanger as the same time as a secondary fluid with a lower boiling point. This secondary fluid vaporizes, turning turbines which drive generators. The geothermal water is returned to the reservoir. Binary plants do not emit anything as their cycle is self-contained.
Geopressured geothermal resources
Another source of energy that can be extracted from the earth is found in geopressure. Geopressured-geothermal resources are gas saturated brines contained in sandstone reservoirs. They are under higher than normal pressure and temperature.
As well as chemical energy contained in the natural gas, and thermal energy which can be used to generate electricity, geopressured resources also contain mechanical energy generated by high flow rates, which can be used to drive turbines and generate electricity.