Geothermal energy is a type of renewable energy that is obtained from the heat inside the Earth. This thermal energy can be obtained without the combustion of any material. It is a form of clean energy without carbon dioxide emissions.
The temperature in the inner layers of the Earth remains constant during the different seasons of the year. The inner layers of the Earth's crust are warmer than the surface in winter and colder in summer.
Sometimes this energy is linked to other geological phenomena such as the presence of geysers, volcanoes or hot springs. These phenomena greatly facilitate the possibility of extracting thermal energy in facilities near these areas.
To take advantage of the heat of the earth, a fluid is passed through the hot area. In this way, thermal energy can be transported to the surface. The heat can then be used directly or converted into electrical energy.
Geothermal energy process and production
The geothermal energy production system is based on the temperature difference between the subsoil and the surface. The energy is exchanged in the form of heat through two closed water circuits that connect them.
In a home or building
One of the advantages of geothermal energy is that it can be used for heating in winter and cooling in summer with high energy efficiency.
To obtain heat in winter, the water within the geothermal collector circuit travels through the subsoil until it is heated. The geothermal collector heats the water in the radiant emitter circuit with a heat exchanger. The emitter circuit is a closed circuit that releases heat in the building.
In summer the heat moves in the opposite direction. The efficiency of geothermal energy is greater the deeper the subsoil circuit is.
Another option for a home is to obtain domestic hot water or heating systems.
In any case, heat pumps are used to optimize thermal performance.
In a power plant
A geothermal power plant produces electricity.
Hot water can also be used to generate steam and drive a steam turbine. In this way, geothermal energy is transformed into mechanical energy (kinetic energy).
Mechanical energy can be used to move machines, or to transform it into electrical energy: electricity.
Types of geothermal sources
These renewable energy sources are obtained through the extraction of the Earth's internal heat through geothermal wells. There are several areas with hot springs.
These thermal waters can be those used in spas or other centers. These waters are heated by the temperature of the Earth's interior.
Hot water with high internal energy can flow naturally by the impulses of water and steam flows or by pumping. The method to be used must be selected based on the method that is most economically profitable.
There is no single method when it comes to harnessing this type of energy. There have been projects that in some countries have had to be rejected due to their economic unviability.
Magma (molten rocks) is a great source of geothermal energy, since rocks are only found in a liquid state at extremely high temperatures. Despite this, with the technology that is available it is economically unfeasible.
Exploitations to extract hot water usually have an even number of geothermal wells. Through one, hot water is extracted and through the other, water is injected back into the aquifer, when it is already cooled.
Types of geothermal deposits
The different types of geothermal energy reservoirs are classified according to the temperature of their thermodynamic source. In this way we have high temperature geothermal energy, medium temperature geothermal energy and low and very low temperature geothermal energy.
High temperature geothermal energy
This type of clean energy is found in areas where the Earth's crust layer is still active. Here, the temperature ranges from 150°C to 400 degrees Celsius. In these cases the steam comes to the surface through a steam turbine that generates electricity.
The drilling that must be done to extract hot water is almost the same as that done to extract oil from wells.
Medium temperature geothermal energy
In medium temperature geothermal energy facilities temperatures range between 70 ° C and 150 degrees Celsius. The energy yield of steam-electricity conversion is much lower, in this case a volatile component must be added.
This type of geothermal energy can be transformed into small power plants. However, it is in distribution through the urban network where its use is maximum. It is used for heating and cooling systems, with absorption machines.
For the production of electricity, it is necessary that the fluid be between 120 ° C and 180 ° C.
Low temperature geothermal energy
It is used in large areas, in areas larger than those that work at high or medium temperatures. It can be found in sedimentary basins, the fluid in these basins is at a temperature between 50 ° C and 70 ° C.
Very low temperature geothermal energy
It is used to serve domestic, urban and agricultural needs. The fluids that can be found are at temperatures between 20° C and 50°C.
Both low temperature and very low temperature geothermal energy are very useful for district heating systems. These systems are carried out through closed circuits.
Examples of uses and applications
The uses of geothermal energy are based on the use of heat energy and the generation of electricity. On a more concrete level, some of the applications of this renewable energy are the following:
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Air conditioning in summer. In a home with underfloor heating, the heating fluid can be circulated through the subfloor.
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Heating in winter.
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Domestic hot water. Used in the daily life of a house.
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Electricity. Electricity is obtained in power plants. This type of thermoelectric plant makes it possible to reduce energy dependence on fossil fuels and nuclear energy.
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Heat production. This heat can be applied to industrial processes. For example heating, drying, evaporation, distillation, sterilization, thawing, washing and salt extraction processes.
