La geothermal energy In just a few years, it has gone from being a niche technology to being at the center of the global energy debate. The heat stored beneath our feet is beginning to be seen as a key element for achieving [a sustainable energy solution]. clean, stable electricity available 24 hours a daySomething that neither solar nor wind power can offer on their own.
While large-scale projects are multiplying in the United States and other regions, Europe and Spain are moving with increasing decisiveness. From pioneering systems of closed-loop geothermal energy From Germany to district heating networks for hotels and homes in the Canary Islands, the European geothermal map is beginning to fill with initiatives that all point to the same goal: to make better use of the subsurface heat to decarbonize the economy without sacrificing security of supply.
A global context that is driving geothermal energy
Geothermal energy currently accounts for less than 1% of global electricity generation, but expectations have changed radically. International Energy Agency It anticipates that, by 2035, the cumulative investment in this technology will have increased. exceed one trillion dollars, driven by the climate emergency and the need for firm energy for increasingly electrified grids.
In countries like United StatesThe shift is already palpable. There, the development of advanced geothermal systems This has led experts from Princeton University to suggest that, by 2050, geothermal energy could generate almost three times the electricity produced by all current US nuclear power plants combinedwhich today cover around a fifth of the country's demand.
This change cannot be understood without the impetus provided by the major energy consumers of the 21st century. Technological giants such as Google o Meta They seek emission-free electricity sources that operate continuously to sustain their mega data centers and artificial intelligence infrastructures, a consumption that is growing at a dizzying pace.
Geothermal energy fits into that gap because it offers clean energy base chargingIt can produce electricity or heat throughout the day, without depending on the sun or wind. Furthermore, modern systems allow the subsoil to be used as well. thermal energy storagesmoothing out peak demand and facilitating the integration of other, more variable renewables.
What exactly is geothermal energy?
The term geothermal itself comes from Greek. geo (land) and thermos (heat). According to the European Geothermal Energy Council (EGEC), It's about the energy stored in the form of heat below the Earth's surfacewhether it is in rocks, soils or groundwater, regardless of its temperature or depth.
It is considered a renewable and low-emission sourceThe Earth's internal heat is practically inexhaustible on a human timescale, and the operation of geothermal plants emits very few greenhouse gases. Furthermore, subsurface temperatures are much more stable than atmospheric conditionsThis allows for high and predictable returns throughout the year.
Depending on the resource and the design of the installation, they differ various types of geothermal energyThere are systems that take advantage of hot groundwater, others that extract heat from dry rocks at great depths, dry steam or natural geyser exploitations, and shallow solutions that use heat exchangers buried a few meters below the surface to air-condition buildings.
Projects are also classified by temperature and useHigh-enthalpy resources (above about 150 °C) are mainly used for generating electricity, while medium- and low-temperature resources are ideal for district heating, domestic hot water, industrial processes or air conditioning of swimming pools and tourist areas.
From conventional geothermal systems to advanced systems
Traditional geothermal energy is based on locating areas where it exists. permeable fractures at depths of less than about 4 kilometers and with temperatures around 150-200 °C. In these natural reservoirs, the water circulates and heats up, rises to the surface, and is used to power turbines and generate electricity.
The technological leap of recent years has come hand in hand with the enhanced geothermal systems (EGS) and closed-loop systems (CLS)The former use techniques from the oil and gas sector, such as fracking and multilateral drilling, to fracture the hot rock and create an artificial reservoir where none existed before.
In EGS, companies drill a deep well Almost vertical, they divert it horizontally at a certain depth and open a second parallel shaft. Then they fracture the rocks between the two to create a tailor-made depositCold water is pumped from the surface through one of the wells; the fluid is heated as it passes through the fractures and returns through the other to transfer the heat to a secondary circuit that activates a turbine.
CLS, for their part, do without hydraulic fracturing. Instead, a closed network of pipes A fluid circulates through this system, heating up upon contact with the hot subsurface rock and returning to the surface without mixing with the surrounding environment. This approach reduces the risk of leaks and simplifies system control, as it only requires... high-temperature rock between 4 and 5 kilometers deepwithout depending on naturally fractured zones.
Looking further ahead, drilling towards “Superhot” zones between 8 and 20 kilometerswhere temperatures approach 400 °C and water enters a supercritical state, a phase that is neither liquid nor gaseous it can carry much more energy down to the surface. If these developments mature, the potential of geothermal energy would expand considerably.
Europe is moving: the closed-loop geothermal plant in Germany
In the European context, one of the most striking recent milestones is the geothermal project of Geretsried (Germany)Developed by Eavor Technologies, this facility has become the first commercial application of its Eavor-Loop technology, a closed-loop geothermal system designed to operate in areas without conventional hydrothermal reservoirs.
The plant has already begun supplying electricity to the grid, marking an important step for the Advanced geothermal energy in EuropeDuring commissioning, the so-called thermosiphon effectwhich allows the fluid to circulate through the geothermal circuit without the need for pumps once the system is started.
In Geretsried, the start-up was carried out with a compact pump with a capacity of about 3 kg/s flow rateThe thermosiphon stabilized in less than half an hour. After that initial period, the pump was no longer needed, demonstrating that the temperature difference between the surface and the subsoil is sufficient to maintain fluid circulation in the closed loop.
The project has also shown that the plant can resume operation after a shutdown without requiring external power to restart the flow, and it is capable of remaining operational for months even under low load conditions. This flexibility is especially interesting for electrical systems that integrate high levels of variable renewables.
According to the design objectives, the Geretsried site aims to achieve around 64 MW of thermal power and some 8,2 MW of electrical powerThis would prevent the emission of approximately 44.000 tons of CO2 equivalent each year. The company plans to use this project as a model to expand the technology to other parts of Europe, with future developments already underway. Hanover and Neu-Ulm.
Drilling innovations that lower costs
Beyond the concept of a closed circuit itself, the experience in Geretsried has served to validate a set of advanced drilling technologies which are critical in high-temperature environments. The company has reported significant improvements in both the total drilling time such as in the usable length of the drill bits.
Among the tools used, the following stand out: insulated drill pipe (IDP)which helps to limit heat loss during operations; the Active magnetic measurement (AMR), which improves well trajectory control; and the sealant known as Rock-Pipedesigned to stabilize the drilled sections and extend the reach in extreme conditions.
The combination of these solutions not only allows you to go further and deeper, but also contributes to reduce development costsThis is a particularly sensitive point in any geothermal project. A large part of the investment is concentrated in the drilling phase, so efficiency improvements in this area directly impact economic viability.
Eavor's management team has presented Geretsried as a technological and commercial success story which will serve as a reference for wider implementation in Europe and other continents. In its communications, the company emphasizes that its system is designed to adapt to very varied regionsThis would allow geothermal energy to be brought to territories without large volcanoes or classic hydrothermal resources.
In a continent where the pressure to achieve energy security, emissions reduction and efficient use of land and water As demand grows, this type of modular and replicable solution fits well with national and community energy transition strategies.
Canary Islands: geothermal energy at the service of tourism
In Spain, although the electrical deployment of other countries has not yet been achieved, geothermal projects are beginning to consolidate. direct thermal use that can pave the way. One of the most unique is ConnectHeat Costa Canaria, promoted by the Federation of Hospitality and Tourism Businesses of Las Palmas (FEHT) and the Technological Institute of the Canary Islands (ITC).
This is the first energy community in Europe specifically focused on the tourism sectorThe initiative focuses on improving the climate control of swimming pools and thermal systems in accommodation complexes using geothermal energy. It begins in the area of English beach, in the south of Gran Canaria, in a block between Avenida Estados Unidos, Calle Luna and Paseo Costa Canaria.
In that environment they coexist 15 non-hotel establishments between one and four stars, totaling about 1.090 places, as well as eight residential buildings with 149 homes, a shopping center and five hotels with approximately 1.573 additional places. It is, in short, a mature and densely urbanized tourist center, representative of many destinations in the archipelago.
The project proposes to implement a renewable heat network For heating and cooling based on water-to-water heat pumps supported by a geothermal system. This aims to significantly reduce energy consumption associated with pool heating and other thermal uses, without requiring large areas for solar panels.
ITC studies suggest that this network could reach 86% renewable coverage of the area's thermal demand, cutting more than half of the current emissions linked to these uses. Furthermore, it is estimated that The energy cost for users will be equal to or less than that of conventional systems, a key factor for the acceptance of the model among hotels, apartments and homeowners' associations.
Cooperative model and European funding
ConnectHeat Costa Canaria has been structured as non-profit cooperativeIt comprises tourism SMEs, homeowners' associations, accommodation establishments, residential buildings, and FEHT itself as the coordinating entity. This legal structure allows for the joint participation of multiple stakeholders. similar energy interests, something essential in complex urban environments.
The total planned investment is around 1,58 millones de euros, with an estimated return period close to nine yearsThe financial burden is eased by the incentives of the European state program. CE Implementswhich will cover around 60% of the budget, making it easier for the energy community to start with a more solid financial foundation.
The FEHT is confident that the project will not remain an isolated experience, but that it can to be replicated in other tourist centers of the archipelagoThe idea is that ConnectHeat Costa Canaria will serve as a demonstrator showing that a well-designed geothermal heating network can improve energy efficiency, cut emissions and maintain competitive costs for the accommodation sector.
The head of renewable energy at the ITC highlighted the character innovative and integrative of the initiative, especially useful in highly consolidated urban areas, where the road network and buildings leave little room to install conventional photovoltaic generationIn these contexts, harnessing the subsoil as a source of heat and cold can be a practical way to advance decarbonization without the need for major surface changes.
Meanwhile, the surge in tourism in the Canary Islands—with levels of Winter occupancy close to 85%— reinforces the need to ensure efficient and stable energy systems. For a destination so dependent on a mild climate and comfortable accommodations, reducing energy costs with renewable solutions becomes both an environmental and a competitive issue.
The emerging picture, from closed-loop geothermal systems beginning to operate in Germany to cooperative heating networks in Gran Canaria, indicates that the Geothermal heat is ceasing to be an underutilized resource In Europe, the combination of new drilling technologies, shared business models, and institutional support positions geothermal energy as an increasingly solid option for providing clean and constant energy, both in the form of electricity and district heating, and all indications are that its weight in the European energy mix will increase in the coming years.
