Energy

Geothermal energy

Definition:

Geothermal energy is a renewable energy that uses the heat of the subsoil to acclimatize and obtain sanitary hot water in an ecological way. Although it is one of the lesser known renewable energy sources, its effects are spectacular to admire in nature. 

Advantages of geothermal energy

  1. It is a source that reduces energy dependence on fossil fuels and other non-renewable resources.
  2. The waste produced is minimal and causes less environmental impact than that caused by oil and coal.
  3. Great economy system, both economic and energetic.
  4. It does not generate external noise.
  5. Geothermal resources are practically inexhaustible on a human scale.
  6. It is not subject to international prices, but can always be upgraded to national or local prices.
  7. The land area required by geothermal plants per megawatt is less than that of other types of plants. It does not require the construction of dams or the clearing of forests.
  8. CO2 emissions, the greenhouse effect, are lower than those that would be emitted by the same energy by combustion, and can be zero when the water is reinjected, circulated, closed, making the external circuit.

Disadvantages of geothermal energy

  1. In dry deposits, microorganisms have sometimes been produced as a result of the sudden cooling of hot stones and their subsequent cracking.
  2. The following disadvantages refer exclusively to geothermal energy that is not used with reinjection and that is not of low domestic enthalpy (geothermal conditioning).
  3. In some cases, the emission of hydrogen sulfide is detected by its rotten egg odor, but in large quantities it is not perceived and is lethal.
  4. Pollution of nearby waters with substances such as arsenic, ammonia, etc.
  5. Thermal pollution
  6. Deterioration of the landscape.
  7. It cannot be transported (as primary energy) unless it is done with a heat exchanger other than the aquifer water.
  8. It is only available in certain places, except for the geothermal air conditioning pump, which can be used anywhere on Earth.

Geothermal energy applications

Geothermal energy applications are based on the use of thermal energy and the generation of electricity. On a more concrete level, some of the applications of this renewable energy are as follows:

  1. Air conditioning in summer: In a house with underfloor heating, the heating fluid can be circulated through the subfloor. This water will acquire approximately a temperature of 15ºC that will facilitate the cooling of the house.
  2. Heating in winter: For the same reason as in the case of air conditioning. In this case, we will use a heat pump to go from 15ºC to 19 or 20ºC where we want to put the heating. This model is also applicable to greenhouses, animal farms, etc.
  3. Production of sanitary hot water for bathing, washing clothes, dishes, etc.
  4. Production of electricity in power plants.
  5. Production of heat that can be applied to industrial processes such as heating, drying, evaporation, distillation, sterilization, thawing, washing and salt extraction.

Geothermal energy production

The geothermal energy production system is based on the temperature difference between the subsoil and the surface. Energy is exchanged in the form of heat – thermal energy – through two closed circuits of water that connect them. For winter heat, the water within the geothermal energy sensor circuit, which is a plastic circuit, arranged in vertical holes that reach between 80 and 200 meters deep, is driven by a subsoil pump to heat, the water heats the circuit that emits radiation, a closed circuit that provides heat to the building. In summer, the operation is analogous, but the heat moves in the opposite direction. The efficiency of geothermal energy is higher the deeper the underground circuit, since the temperature difference is greater.

To obtain hot water, the collector circuit heats the hot water from an open circuit, which comes from the water network and can be stored in one or more tanks. Hot water can also be used to drive a turbine, thus transforming geothermal energy into mechanical energy, in this case kinetic energy. Mechanical energy can be used to move machines or convert them into electrical energy: electricity.

For small renewable energies (production up to 30 kilowatts (KW) and you can have horizontal and surface heat collector Dialects water pipes, that is, between one and five meters, usually between one and a half and two, for example, under a garden The heat pump is the size of a refrigerator, but is very quiet and can be placed in the garage, for example.

Types of geothermal sources

Geothermal energy is obtained by extracting the internal heat of the Earth. There are several areas with hot springs. These hot springs can be those used in spas or other centers. These waters are heated by the temperature inside the Earth. In areas where the hot springs are very hot, surface drilling is done through natural fractures.

Hot water and / or steam, which have a certain amount of internal energy, can flow naturally, through the impulses of water and steam, but also through pumping. You have to select the method to use depending on the method that is most economically profitable. There is no single method to exploit this energy, as there are projects in some countries that have had to be rejected due to their economic impracticality.

Magma – geothermal energy:

Magma (molten rock) is an important source of geothermal energy, since rocks are only in a liquid state at extremely high temperatures. However, with the technology available today, it is not possible to take advantage of this type of renewable energy sources, it is economically unviable. The farm to extract hot water, usually has an even number of wells, such as for one hot water extract and the other one re-injects the water into the aquifer, and when it cools. This system has several advantages:

There is little chance that the water in the reservoir will run out, as by continuously injecting the volume remains constant. There are no emissions of dissolved gases, since the water circuit is closed, which avoids possible contamination from the outside.

High temperature geothermal energy:

This type of renewable energy is found in areas where the crust layer is still active and the temperature ranges between 150 ° C and 400 ° C. In these cases, the steam reaches the surface through a turbine that generates electricity when moved by the force of the steam. To find an area from which to extract hot water, a geothermal area, you have to find an upper layer composed of:

  1. Coating of waterproof rocks, which allow the filtration of water.
  2. High permeability aquifer or reservoir, between 300m and 2 km deep.
  3. Fractured soil, allows the circulation of fluids by convection, so that the heat transfer reaches the surface.
  4. Source of magmatic heat, at a depth between 3 and 15 km and at a temperature between 500 ° C and 600 ° C.
  5. The holes that must be made to extract the hot water are almost the same as those that must be carried out to extract the oil from the wells.

Average temperature of geothermal energy:

In medium temperature geothermal energy installations, the temperature of the aquifer fluids is at significantly lower temperatures, at temperatures ranging between 70 ° C and 150 ° C, for which the efficiency of conversion of electricity into steam is much lower, in this case you have to add a volatile component. This type of geothermal energy can be transformed into small plants, but it is in the distribution through the urban network where the use is maximum, it is used for heating and cooling, with absorption machines. This is used for the production of electricity, it is necessary that the fluid is between 120 ° C and 180 ° C.

Low temperature geothermal energy:

It is used in large areas, in larger areas than those that work at high or medium temperatures. It is found in sedimentary basins, the fluid in these basins is at a temperature between 50 ° C and 70 ° C.

Geothermal energy at very low temperature:

It is used to satisfy domestic, urban and agricultural needs. The fluids that can be found are at temperatures between 20 ° C and 50 ° C. Both low temperature geothermal energy and very low temperature geothermal energy are very useful for district heating systems, through closed circuits.

Geothermal power plants:

Geothermal power plants have the function of generating electricity from the thermal energy inside the Earth. For this, they have heat exchangers in order to generate steam. With the pressure of steam, a turbine is activated, obtaining mechanical energy. The mechanical energy obtained by the turbine can easily be converted into electrical energy by means of an electrical generator.

  • Geothermal gradient:

Ratio in which, at a certain distance from the surface at sea level, towards the interior, it increases 1ºC.

  • Radiogenic heat:

Relative to the internal energy of matter, generating heat through the decomposition of different isotopes.

Geothermal reservoirs:

They are points on the map where we find a higher temperature, for absolutely natural reasons. Can they be areas of cracks or breaks in tectonic plates, or areas with activity that cause earthquakes, eruptions? There are four types of deposits:

  • High temperature tanks: There is a heat source, where the fluid is stored at about 100ºC. The focus is surrounded by permeable rock, which in turn is surrounded by a layer of rock that has cracks.
  • Low temperature deposits: The temperature ranges between 100 and 60ºC.
  • Very low temperature deposits: Above 15ºC.
  • Hot rock deposits: rocks that are between 5 and 8 kilometers underground.

Countries where geothermal energy is used

In a world where the search for ways to reduce dependence on oil and greenhouse gas emissions is expanding, the use of clean and sustainable energy seeks eruptions in the economies that need it most. The exploitation of this type of energy began in Larderello (Italy) in 1904, but today it is present in many countries with volcanic activity such as Iceland, New Zealand, Japan, the Philippines and the western United States.

Iceland is the country with the largest geothermal activity in the world, and 99% of homes are heated by this energy. Worldwide, its use for heating reaches 33%. The state of California has more than 30 geometric power plants, responsible for producing 90% of the geometric energy consumed by the United States. In turn, we know that the world’s first solar and geothermal hydroelectric plant will be built in the state of Nevada.

Developing countries know that geothermal energy can be the cornerstone that recovers the wealth of their agriculture, facilitating the quality and maintenance of food. This would be a great advance in the places that surround the so-called “Pacific Ring of Fire”, such as Mexico, Indonesia, Colombia or Ecuador.

This would also be the case for countries that converge in the Great African Rift Valley, such as Ethiopia and Kenya. Already in Europe, countries like Romania, Bulgaria and Macedonia have the hand to rethink a more sustainable future thanks to geothermal energy resources.

In Spain, geothermal energy is used to produce heat in spas and greenhouses in Ourense and Murcia. The latest news leads us to affirm that Galicia can become one of the pioneer cities in the use of geothermal energy for heating, air conditioning and hot water in buildings. He even came to talk about the first company that made heat pumps.

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