Geothermal energy: find out what it is and how it works

What is geothermal energy?

Geothermal energy takes advantage of the heat from inside the earth and uses it to sustainably power air conditioning systems and generate renewable electricity. 

The origin of the name geothermal energy comes from the Greek words geo (earth) and thermos (heat).  In other words, the energy that comes from the heat of the Earth. It is clean, renewable energy that, if well used, is never-ending. As such, we have yet another alternative with which to achieve a green and sustainable energy supply.

The birth of geothermal energy

Although the thermal force of nature has been known since ancient times with the dreaded volcanic eruptions, the ability to take advantage of that heat from the Earth's interior and transform it into geothermal energy began in the nineteenth century.

In 1818, Francesco Giacomo Larderel decided to use steam from the nearby geothermal waters of Montecerboli (Italy) to heat the boilers in a chemical factory producing boric acid and managed to increase both productivity and energy savings.

It had such an important financial impact on the area that, as a tribute to Larderel, the town that was built around the factory was named Larderello. Currently, a very interesting place to visit and that we recommend in the post on energy tourism.

About 100 years later, 1904 can be considered as the year of the birth of geothermal power plants for the production of electricity. Based on Larderel's ingenuity, a power station was built that lit up five light bulbs.

Geothermal energy had proven its usefulness, and that plant was followed by many others. In 1913, Larderello 1 came into operation which, thanks to the geothermal energy of the hot springs, was able to generate more than 2,700 kW of electricity, used for the railway and the electricity consumption of the villages in the area.

Italy is currently the sixth largest producer of electricity from geothermal energy in the world, with 34 plants belonging to Enel Green Power. Another interesting case is that of Reykjavik (capital of Iceland) which has the largest geothermal energy heating system in the world and has made it possible to considerably reduce polluting emissions.

Geothermal energy in Spain

Geothermal energy is not widespread in production plants in Spain, with wind energy being more commonly used or solar energy.

However, this has not prevented geothermal energy from being used in climate control systems in many modern constructions of homes and buildings in our country.

A few meters down, the temperature of the earth has a much more constant temperature than on the surface, with average temperatures of around 15-20 °C. This stable temperature can be used to exchange the heat from the building, helping to cool it in summer and heat it in winter. This makes it possible to reduce the electricity and gas consumption needs of the entire installation.

How does geothermal power work?

1. Drilling: before putting any geothermal energy system into operation, it is necessary to locate and drill the appropriate area. To do so, geological and mining studies are required, as well as adequate technological equipment and highly qualified personnel.
2. Installation. After drilling it is necessary to introduce one or more geothermal probes. Sealed pipe-shaped probes, made of polyurethane and filled with water or antifreeze liquid. Their function is to perform the heat exchange, and once they are introduced into the deepest area, they rise back to high temperatures and the heat is collected on the surface.
3. Production: to obtain electricity, there must be a geothermal plant that collects steam and converts it into mechanical energy using a turbine. Geothermal energy can even be supplied directly to homes, directly connecting the heat obtained with a district network that directly heats buildings. Using a converter, it is also possible to generate the opposite effect and offer cold air in summer.

Types of geothermal energy

There are several types of geothermal energy. The difference will depend on the drilling depth. According to this classification, three are three different types of geothermal energy.

1. Surface geothermal energy

This is just a few meters from the earth's crust, found by drilling just 150 or 200 metres. In this case, the temperatures reached by water in the thermodynamic cycles are between 50 and 70 °C. It is the type of geothermal energy most used to obtain energy for domestic use.

2. Deep geothermal energy

In this case, the level of drilling reaches between 1 and 4 km deep. This provides temperature values of between 70 and 150 °C. In this case, geothermal energy can now be used to produce electricity with the help of steam turbines.

3. Geothermal energy from great depths

To use this renewable energy source it is necessary to deepen the drilling up to 4 or 6 km. This is where the highest temperatures can be found, which can vary between 150 ºC and 400 ºC. 

Geothermal energy found at great depths makes it possible to produce electricity on a larger scale. In this case, the infrastructure of the power plant is much more complex and very similar techniques are used to those seen during oil extraction.

We should also mention that geothermal energy can be extracted from hot rocks that can be found in dry deposits between five and eight kilometres underground.

Advantages and disadvantages

Advantages of geothermal energy

Among the many advantages of geothermal energy, three in particular stand out:

1. It is clean energy. An essential alternative to take on the energy sustainability and decarbonisation challenges.
2. It minimises the use of fossil fuels by achieving plants that minimise their operating carbon footprint.
3. It generates hardly any waste or harmful gases, so the environmental impact and environmental protection are guaranteed with the use of geothermal energy.
   

Disadvantages of geothermal energy

The main disadvantage of geothermal energy is that it requires very specific geological conditions in order to be implemented effectively.

In Spain, there are studies carried out in the areas of Andalusia, Murcia, Catalonia and the Canary Islands as possible places for the use of geothermal energy to generate electricity, although it is currently difficult to develop.

The negligible emission of greenhouse gases mitigates any possible thermal pollution. The noise generated in the construction of the facilities disappears when the production of energy starts.

In short, although geothermal energy is more unknown to part of the population, it offers many benefits and possibilities to advance to a more sustainable energy production system. At Endesa, we are committed to this change, which is why we already offer our customers the possibility of consuming only renewable energies with Endesa Única.