What is geothermal energy and what are the possibilities for its use in Spain?

Geothermal heat pumps are the equipment that allow us to take advantage of the energy extracted from the ground to bring it to our homes or businesses. In summer it extracts the heat from the interior and expels it towards the geothermal wells to cool, while in winter it uses the heat extracted from the geothermal wells to heat the interior. A very efficient and renewable method which we analyze in the following lines.

What is geothermal energy

The term “geothermal” comes from the combination of the Greek terms “geo” and “thermos”.

While the former means earth, the latter refers to heat, being the form in which energy is generated and stored inside the planet.

But what makes this energy so interesting and how can we harness it? That’s what we look at in this article.

As I mentioned above, geothermal energy is, in essence, heat stored beneath the earth’s surface.

A heat that has its origin in the natural radioactivity of materials present in the Earth’s mantle and, in key locations, is also generated as residual heat from the formation of our planet.

Geothermal energy is essentially the heat stored beneath the earth’s surface.

As a source of energy from the Earth’s interior, it is practically inexhaustible on a human scale and can be captured in two different ways:

• Low-temperature geothermal: Used for direct heating or to heat water in spas. For example, in some single-family houses, geothermal heat pumps are used to take advantage of the constant temperature of the subsoil and heat or cool spaces.

• High-temperature geothermal energy: This is found at greater depths and is mainly used for electricity generation. Through geothermal plants, steam from these deposits is used to drive turbines and generate electricity.

All this makes it a clean and sustainable source of energy that does not emit greenhouse gases. You will learn how geothermal energy takes advantage of this temperature.

Moreover, being a continuous energy source, it does not depend on factors such as sunlight or wind, which makes it more reliable compared to other renewable sources.

How geothermal energy works

Although it is one of the least known renewable energy sources, its potential, which is influenced by weather conditions, is immense and its operation fascinating.

The Origin of Heat

Before understanding how it works, it is vital to know where this heat comes from.

The Earth’s core is extremely hot, thanks to radioactive decay and retained heat from the formation of our planet.

This temperature decreases as we get closer to the Earth’s crust, but in some areas, the heat is close enough to the surface to be harnessed.

This means that, although we still cannot descend very far, we do have the possibility of using this residual heat to our advantage.

Geothermal Reserves

Unfortunately, geothermal energy is not equally available in all parts of the world.

There are what are known as geothermal reservoirs.

These are areas where the earth’s heat is closer to the surface due to geological phenomena, such as volcanoes or tectonic plates.

At these points, groundwater can heat up and form steam or hot water reservoirs.

And that is what we use to generate energy.

Capture and Conversion

The process to transform this heat into energy varies according to the temperature and nature of the reservoir:

• Dry Steam Plants: These are the oldest and most direct. They extract steam directly from the earth and use it to drive the turbines that generate electricity.
• Flash Steam Plants: Here, high temperature water is converted into steam by lowering its pressure. This steam is then used to turn a turbine.
• Binary Cycle Plants: These are the most common today. Hot geothermal water is used to heat a secondary liquid with a lower boiling point than water. When this liquid vaporizes, its steam drives the turbines.
• Direct Heating: In areas where the heat is not intense enough to produce electricity, it can be used directly to heat buildings, greenhouses, swimming pools and more.

Cooling and Recirculation

After passing through the plant, the liquid is cooled and reinjected underground.

This allows the pressure and temperature of the geothermal reservoir to be maintained, making the process sustainable over time

Types of geothermal installations

Geothermal energy, being a source of different types of geothermal energy that take advantage of the heat stored in the subsoil, offers different ways of capture depending on the characteristics of the site and the needs of the project.

Below we will try to explain it in a simple way so that making a decision is easy.

Closed vertical geothermal system

One of the most efficient ways to capture geothermal energy is through vertical drilling.

In this type of system, one or more boreholes are drilled up to 200 meters deep (or even deeper) into the ground.

Inside these boreholes, U-shaped pipes are inserted through which a cooling fluid circulates.

Thanks to the stable temperature of the subsoil, the constant temperature is used and this fluid is heated or cooled according to the need, to be subsequently taken to a heat pump that extracts or transfers this energy.

Its main advantage is its efficiency in small spaces, since it takes advantage of the depth of the ground.

With a small space, you can generate a large amount of clean and economically efficient energy.

Closed horizontal geothermal installation:

The horizontal option is best suited to sites with a larger area of available land.

In this case, pipes are installed at a depth varying between 1 and 2 meters, distributed horizontally.

The cooling fluid circulates through these pipes, capturing heat energy from the ground in a similar way to the vertical system.

Although it requires a larger area, it is usually less expensive in terms of drilling compared to vertical installation.

Beyond that, what is really important is that it adapts to the needs of each specific case.

Open geothermal energy

This mode is particularly suitable for locations with abundant groundwater sources.

Instead of using a closed circuit with a cooling fluid, the open collector system draws water directly from subway aquifers or lakes.

Once extracted, this water is passed through a heat pump that uses its temperature for heating or cooling.

After this process, the water is returned to the subsoil or to another point, ensuring minimal impact on the subway ecosystem.

It is essential, when opting for this system, to have adequate hydrological studies to ensure the sustainability of the resource.

As you can see, most of the processes have a number of points in common and certain decisions to improve energy efficiency.

Geothermal energy maintenance: Why and how to do it?

Although the different types of geothermal installations are known for their longevity and reliability, they are not exempt from the need for periodic maintenance to ensure their proper operation, efficiency and maximize their long service life.

Why is maintenance important?

Maximize efficiency: Like any system, over time, geothermal installations can face obstructions or wear and tear that reduce their efficiency. Proper maintenance ensures that the system operates at its maximum capacity.

Extending service life: A well-maintained system will last longer. Geothermal heat pumps, for example, can last more than 20 years with proper care, and subway piping even longer.

Prevent major problems: A regular checkup can identify and fix minor problems before they become major failures requiring costly repairs.

Safety: Although geothermal installations are generally safe, maintenance helps prevent problems that could compromise the safety of equipment or people.

What aspects should be considered in maintenance?

Inspection of the fluid circuit: It is essential to check that there are no leaks in the circuit, both in closed and open systems, and to make sure that the fluid is in good condition. In closed systems, the antifreeze fluid may need to be replaced or topped up.

Heat pump cleaning and inspection: Heat pumps should be inspected and cleaned to ensure that they are operating properly. This includes checking electrical components, connections and the heat exchanger.

Flow and pressure monitoring: It is vital to monitor fluid flow and pressure to ensure that the system is operating at optimum parameters.

Verification of valves and thermostats: These components should be checked to ensure proper operation and calibration.

In open catchment systems: It is crucial to monitor groundwater quality to avoid the accumulation of sediments or minerals that could clog the system.

Visual inspection: Piping, connections, and other visible components should be checked for signs of wear or damage..

Geothermal energy: Advantages and disadvantages of its use

But if you are reading this article, it is probably because you are wondering whether or not to opt for this type of energy.

So now we would love to tell you about the great advantages (and also the negative points).

Energy savings:

A geothermal installation is efficient and can generate significant energy savings compared to other cooling, heating and hot water systems.

Energy efficiency is maximized when combined with underfloor heating. It is a bet against climate change.

Consistency: Geothermal provides a constant heat source, as subway temperatures remain stable throughout the year, regardless of weather conditions at the surface.

High COP: The Coefficient of Performance (COP) of geothermal systems is remarkably high, producing more energy than it consumes.

Optimization: By designing and installing the geothermal system correctly, performance is optimized, maximizing savings in terms of energy consumption and costs.

Low maintenance cost:

Geothermal installations are noted for their remarkable durability and reliability, factors that directly contribute to low maintenance costs.

The lifespan of a geothermal heat pump can range from 20 to 25 years, while subway infrastructure, also known as a geothermal loop, has the capacity to provide service for more than 50 years.

The robustness and longevity of these systems is supported by the fact that they have few moving parts, which translates into less wear and tear and, consequently, lower repair needs throughout their operational life.

Moreover, a crucial aspect that supports the low maintenance of geothermal systems is the subway location of most of their components.

This feature shields them from inclement weather and extreme climatic variations, minimizing weather-related wear and tear.

In addition, this environmental protection not only enhances the durability of the system, but also ensures smooth and efficient operation throughout the year, unaffected by the seasons.

From the user’s perspective, geothermal systems offer remarkably quiet operation and freedom from annoying vibrations, aspects that not only provide a comfortable and quiet environment but also indicate that system components experience reduced mechanical stress.

This smooth operation, inherent to geothermal, ensures that internal components, such as pumps and heat exchangers, maintain their structural integrity over time, requiring sporadic and basic maintenance interventions.

Finally, although the initial investment in a geothermal system may be higher than that of other HVAC systems, the savings derived from its energy efficiency and low maintenance costs result in an attractive payback period.

The price of installation is high, but in the long run, it is much cheaper because of the savings on heating bills. Spain is the country in the European Union that spends the most on electricity and gas, therefore, this air conditioning alternative will reduce the cost of this service, which will favorably affect the pocket of the Spaniards.

In fact, saving money is even more important now because, due to the pandemic, many people have lost their jobs or have seen their working hours reduced, negatively influencing the monetary resources coming into the household. So what better than choosing a high-efficiency system to meet one of your basic needs?

With significantly lower energy consumption than its conventional counterparts and reduced operating and maintenance costs, geothermal is establishing itself as a financially viable and environmentally responsible option for the long term.

Installation possibilities in Spain

In Spain, the installation of geothermal heat pumps is being slow and gradual. It has more and more followers, but it is true that we are still behind Europe. Even so, both the Spanish government and the autonomous communities have published laws in recent years with measures to promote renewable energies such as geothermal energy. As an example, there is the Royal Decree-Law of June 2020, approved by the Council of Ministers, at the proposal of the Ministry for Ecological Transition and Demographic Challenge (MITECO) to boost the use of green energies and favor economic reactivation in the context of the COVID-19 pandemic.

In addition, there are investment aids in renewable energies from the Institute for Energy Diversification and Saving (IDAE) of the MITECO, which have been co-financed with European Union funds. There are also subsidies from some autonomous communities that promote the installation of systems that make use of renewable energies such as geothermal energy.

Long service life:

With proper energy use and maintenance, geothermal energy has a long service life, longer than many other home air conditioning systems.

Cooling and heating with a single consumption:

A single geothermal system can provide both heating and air conditioning, optimizing energy consumption and reducing CO2 emissions.

Passive cold:

It harnesses the temperature of the subsoil to provide cooling without the need for additional energy.

It does not require the use of solar panels:

While various forms of renewable energy, such as solar, depend on specific climatic conditions to be efficient, geothermal operates remarkably autonomously, taking advantage of the inherent thermal stability of the earth’s subsurface.

This uniqueness allows geothermal systems not to depend on the installation of solar panels for their operation, which is a distinctive feature and an advantage compared to other renewable sources.

The subsurface temperature, at a certain depth, remains relatively constant throughout the year, regardless of surface weather conditions.

Therefore, unlike systems using photovoltaic solar energy, geothermal energy is not subject to the variability of the seasons or the intermittency of the sun.

This characteristic makes geothermal energy a constant and reliable energy solution that can generate heat and cold in a continuous and stable manner.

Additionally, this independence from solar panels means that geothermal can be an especially viable option in locations where space for solar panels is limited or where solar conditions are not optimal. 

Similarly, this system can be a relevant energy solution in regions where building density is high or in natural environments where the installation of solar panels could affect the aesthetics of the landscape or interfere with local flora and fauna.

In terms of implementation in diverse locations, geothermal stands as a versatile alternative, offering a renewable energy source that does not compete for airspace or depend on sunlight.

Therefore, it is a viable alternative in places where other renewable sources may not be as effective or applicable, thus ensuring a more universal and accessible option for obtaining clean and sustainable energy.

Reduces noise pollution:

Unlike other systems that can generate noise, such as external air conditioning units, geothermal is remarkably quiet. This contributes to a quieter environment, especially in residential areas.

Perpetual and inexhaustible energy:

Geothermal energy is a renewable energy that eliminates dependence on fossil fuels.

As long as the planet exists, we will have access to underground heat, which makes geothermal energy an inexhaustible energy source

Subsidies, allowances and deductions available:

In Spain, the drive towards renewable energies has generated a series of government incentives for those who opt for geothermal energy.

These can include subsidies, tax deductions and rebates, which improve the payback period and return on investment.

Combination with photovoltaic:

Geothermal, being an effective and consistent energy source in its own right, can, when combined with solar PV, form a truly powerful and sustainable energy tandem.

This combination takes advantage of the best of both worlds: the constancy of geothermal and the ability of photovoltaic systems to generate electricity in an environmentally friendly and renewable manner.

Geothermal energy guarantees a constant source for heating and cooling, utilizing the stable temperature of the subsurface to provide year-round climate solutions.

Solar photovoltaics, on the other hand, converts direct sunlight into electricity, which can be particularly useful for meeting the electrical demands of a home or building.

Together, these two renewable energy sources can create a comprehensive system that supplies a wide range of a property’s energy needs, from weatherization to general power supply.

When implemented together, geothermal and photovoltaics can feed into each other to optimize energy savings and efficiency.

Electricity generated through solar panels can be used to power geothermal heat pumps, creating a closed, sustainable energy cycle that minimizes dependence on the conventional power grid and reduces carbon emissions.

It is necessary to have land for the catchment:

One of the main challenges of geothermal energy is the need for a suitable ground for collection, either for horizontal installations or vertical wells.

This may limit its application in certain urban areas or homes without access to suitable underground space.

The installation of geothermal energy is more expensive than conventional energy:

The adoption of geothermal energy systems, despite their efficiency and environmental friendliness, is accompanied by an initial investment that can be significantly higher compared to more traditional or conventional energy systems, such as those based on natural gas or electricity.

This initial investment is largely directed towards the installation of the underground geothermal loop and the purchase of specialised geothermal heat pumps, among other systemic components.

However, it is imperative to view this investment from a long-term perspective, given the durable and economically efficient nature of geothermal systems.

The energy efficiency of these systems, which is significantly higher compared to conventional alternatives, results in significant monthly savings on energy bills.

Therefore, although the initial investment is high, the return on investment is seen through the continuous and sustained reduction in operating costs.

In addition, the availability of subsidies, tax credits, and other financial incentives offered by various government entities and institutions dedicated to the promotion of renewable energy can significantly mitigate the initial financial burden associated with the implementation of geothermal energy.

These incentives, which aim to promote the adoption of cleaner and more sustainable technologies, can significantly shorten the payback period of the initial investment, making geothermal a more affordable and economically attractive option for a wide range of consumers and businesses.

The aspect of maintenance costs also plays a crucial role when analysing the financial viability of geothermal.

With significantly lower maintenance requirements compared to conventional heating and cooling systems, the costs associated with repairs, replacements and regular operations are significantly reduced over the lifetime of the geothermal system.

This factor, together with the savings in energy consumption and potential subsidies, make geothermal as affordable, if not more so, than its more traditional counterparts in a long-term financial analysis.

Conclusion

Geothermal energy represents a sustainable and highly efficient option for air-conditioning buildings and obtaining domestic hot water.

Its ability to take advantage of the constant temperature of the subsoil and function, despite knowing how weather conditions influence it, makes it one of the most promising alternatives to other systems.

In Spain, the possibilities for its use continue to expand, and as more people and companies adopt this technology, the benefits in terms of energy savings, reduction of CO2 emissions and sustainability will become even more evident.

Therefore, they are encouraging the installation of air-conditioning systems such as heat pumps, in order to have efficient buildings, with cost-saving equipment and less negative consequences for the earth.

For all these reasons, we recommend that you install geothermal heat pumps and leave conventional systems to one side. If you decide to install them in your home or office, pay attention to the information we are going to give you about the possibilities you have to install them in Spain.

We also have to make sure that we meet the technical requirements necessary to start the installation. Therefore, it is necessary to explore the land, see the available space, apply for authorisation to drill the ground. At Ecoforest, we can help you with all this, you can consult us whenever you want.

As you can see, it is relatively easy to install this air conditioning system anywhere in Spain, as our soils are a great source of renewable energy. Therefore, we encourage you to contact us and we will advise you, so that you can benefit from the qualities of geothermal heat pumps as soon as possible.