Geothermal energy: history, exploitation and future

  • Geothermal energy has been exploited for more than 2.000 years.
  • There are three main types of geothermal reservoirs: high temperature, low temperature and dry rock.
  • Geothermal energy is a renewable and efficient option for heating and electricity generation.

Marine geothermal energy and its potential

You probably know what geothermal energy is in general terms, but Do you know all the basics about this energy? Generally speaking, we say that geothermal energy is heat energy from inside the Earth. In other words, geothermal energy is the only renewable energy resource that does not derive from the Sun. Furthermore, we can say that this energy is not a renewable energy as such, since its renewal is not infinite, although it remains inexhaustible on a human scale, so it is considered renewable for practical purposes.

Origin of heat inside the Earth

Origins of geothermal energy

The heat inside the Earth originates mainly from the decay of radioactive elements such as Uranium 238, Thorium 232 and Potassium 40. These elements are constantly disintegrating, releasing thermal energy in the process. Another important factor is the collisions of tectonic plates, which release heat due to movement and friction. In certain regions, geothermal heat is more concentrated, as is the case in areas near volcanoes, magma flows, geysers and hot springs. This allows for greater ease in its energy use.

Use of geothermal energy

Geothermal energy has been used for over 2.000 years, with the Romans pioneering the use of hot springs for thermal baths and heatingIn more recent times, it is used for heating buildings, greenhouses and electricity generationThere are three types of deposits from which geothermal energy can be obtained:

  • High temperature reservoirs
  • Low temperature reservoirs
  • Dry hot rock reservoirs

High temperature reservoirs

It is considered a deposit of high temperature when the groundwater in the deposit reaches temperatures above 100°C due to the proximity of an active heat source. In order to extract heat from the subsoil, the geological conditions must allow the existence of a geothermal reservoir, which works in a similar way to oil or natural gas reservoirs.The heated water through these rocks it tends to rise towards the surface until it reaches a geothermal reservoir trapped by an impermeable layer. However, if there are cracks in this impermeable layer, steam or hot water can rise and They appear on the surface in the form of hot springs or geysersThese heat sources have been exploited since ancient times, and today they are used for heating and industrial processes.

Low temperature reservoirs

A low temperature reservoir is one where The water reaches between 60 and 100ºCIn these cases, the heat flow is normal, so it is not necessary to have an active heat source or the presence of a waterproof layer. Low temperature deposit

The key here is to have a water reservoir at depths that allow temperatures high enough to make its exploitation economically viable.

Dry hot rock reservoirs

The deposits of dry hot rocks They have even more potential, as they are among the 250-300ºC and at depths of between 2.000 and 3.000 meters. To extract heat from these rocks, it is necessary fracture them to make them porous. Dry hot rock

In this system, cold water is injected from the surface, passing through hot, porous rocks, heating up in the process, and then extracted as steam to generate electricity. However, these fields are difficult to exploit due to the fracturing and drilling techniques required for their exploitation.

Very low temperature geothermal energy

We can also consider the subsoil as a heat source at 15ºC, completely renewable and inexhaustible. With an appropriate capture system and a heat pump, it is possible to transfer this heat to a heating system that can reach up to 50ºC, providing heating and hot water. Geothermal capture systems

This system can also be used in summer, storing heat at 40ºC underground. The main disadvantage is that a large surface area is needed to bury the external circuit, but its main advantage is the energy saving and versatility can be used for both heating and cooling.

The geothermal heat pump

The essential element in this type of system is the bomba de calorThis thermodynamic machine bases its operation on the Carnot cycle, taken from a gas that acts as a heat carrier between two sources, one at low temperature and the other at high. Heat pump diagram

This pump can extract heat from the ground at 15ºC and raise its temperature to heat the air in an internal circuit, achieving much greater performance than conventional air conditioning systems.

Exchange circuits with the Earth

We can distinguish between exchange systems with surface water, which are cheaper but are geographically limited, and the exchange with the ground, which can be direct or through an auxiliary circuit.

  • Direct exchange: simpler and cheaper, but with risk of leaks and freezing.
  • Auxiliary circuit: more expensive, but avoids large temperature fluctuations.

It should be noted that, by absorbing heat from a stable temperature source such as the subsoil, these systems offer constant and efficient performance throughout the year, regardless of atmospheric conditions.

Performance of air conditioning systems

La Energy Efficiency of geothermal air conditioning systems is outstanding: they can achieve efficiencies of up to 500% in cooling and 400% in heating. This means that for each unit of energy used, up to 5 units of thermal energy can be generated in the case of cooling. Geothermal performance diagram

Apart from its high efficiency, this system has the advantage of not depending on fluctuations in solar or wind energy, since the Earth provides a constant source of heat.

Geothermal energy distribution

Geothermal energy distribution map

Geothermal energy is distributed throughout the planet, but with a higher concentration in volcanic and fault zones. Areas such as the Pacific coast in America and Indonesia have high potential. However, its exploitation can be extended to other areas with modern drilling technologies.

Advantages and disadvantages of geothermal energy

Advantages:

  • Availability worldwide.
  • Inexhaustible on a human scale.
  • The cheapest energy known.

Disadvantages:

  • Possible release of sulfurous gases.
  • Heat transmission over long distances is not feasible.
  • High initial installation costs.

The future of geothermal energy

The planet's geothermal potential is enormous, with enough energy stored underground to supply the world's energy needs for millions of years. As drilling techniques advance, the use of geothermal energy is expected to become more widespread in industrial processes, heating buildings and generating electricity.Future geothermal energy

With the development of new technologies such as bladeless turbines capable of generating electricity at lower temperatures, geothermal energy has a promising future to become an essential part of the global energy supply.

Geothermal energy thus not only offers a clean and abundant alternative, but can help us move towards greater energy independence while reducing our carbon footprint.


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