Geothermal energy is a renewable energy source that is extracted from the Earth’s core. Under the earth’s surface, at an enormous distance, there are reservoirs of water heated by molten rock, or magma.
These deposits serve as geothermal reserves that can be used by humans to drive many of their daily activities, both industrially and at home.
Geothermal energy is found almost anywhere, and best of all, it it is affordable and reduces dependence on fossil fuels that contribute to global warming and generate risks to people’s health.
Although the production process of this type of energy releases carbon dioxide and methane (greenhouse gases), its environmental impact does not come close to that generated by burning coal, oil or natural gas.
The most exploitable regions in terms of large-scale geothermal energy are those that have greater volcanic activity or have geological faults (seismically active), as well as areas where hot springs abound.
When used correctly, this energy source offers a constant supply and independent of the use of batteries, as is the case with wind and solar energy.
How is electrical and thermal energy generated with geothermal energy?
To extract heat from underground geothermal reservoirs, a water pumping system based on an injection well. Subsequently, the water filters through cracks in rocks exposed to high temperatures, to finally return as vapor through a recovery well that is under pressure. Finally, steam is captured and used for electricity generation.
There are three techniques that facilitate the use of geothermal reservoirs:
Direct geothermal energy generating electricity
This technology is used in regions with geothermal reservoirs close to the earth’s surface, and allows pump hot water directly to buildings and homes to be used as heating. It works in the following way:
- The vents are drilled down to the geothermal reservoir.
- A heat exchanger is used to pump the hot water and send it to the domestic heating system.
- The used water returns to the geothermal reservoir, where it will be reheated to start the cycle again.
Operation of a geothermal plant or power station
These types of facilities use the heat that exists under the earth’s crust to produce electrical energy. There are three techniques to do so:
- dry steam : Steam from geothermal reservoirs is transmitted to a geothermal power plant. Over there, heat activates the blades of a turbine and makes it spin, which in turn activates a generator that produces electricity.
- flash steam : A series of perforated pipes sucks water directly from the geothermal reservoir. The water, which must have a temperature between 148°C and 371°C, turns into steam and is transmitted directly to the turbines, which activate the electric generator. Subsequently, the steam cools and transforms into water. The water returns to the reservoir to start the cycle again..
- binary cycle : The water used by this system must have a temperature between 120°C and 180°C. During the process, a heat exchanger is used that transfers the temperature of the water to a second liquid, whose boiling point is less than that of water. This liquid, which can be pentane or isobutane, is heated to generate the steam that will drive the turbine. Again, the turbine is connected to a generator that produces electrical power.
Operation of a geothermal heat pump
It is a heating and cooling system that aims to transfer heat to the ground and land surface. To do this, it takes advantage of the underground heat during the winter and, in the summer, it uses it to dissipate the heat. Its operation is similar to that of a conventional heat pump., and is based on the following principles:
- A high pressure coolant takes advantage of the heat and transfers it inside and outside a building or housing. To do this, it uses extensive loops of pipes filled with liquid lodged underground.
- The building has a heat exchanger and an electric compressor that sucks heat from the pipes and transmits it to the entire structure through ducts. In summer, the geothermal pump works in the opposite way, since the pipes suck the heat from the building and send it to the ground for storage.
Its main application in this case is to provide electricity and heating to isolated homes.