Geothermal energy has gone from being a niche technology to a central focus of the global energy debate in just a few years. The heat stored beneath our feet is beginning to be seen as a key element for obtaining clean, stable, and 24/7 electricity —something that neither solar nor wind power can offer on its own.
While large-scale projects are multiplying in the United States and other regions, Europe and Spain are moving with increasing determination. From pioneering closed-loop geothermal systems in Germany to district heating networks for hotels and homes in the Canary Islands, the European geothermal landscape is beginning to fill with initiatives that all point to the same goal: to make better use of geothermal heat to decarbonize the economy without compromising 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 dramatically. The International Energy Agency forecasts that, by 2035, cumulative investment in this technology will exceed one trillion dollars , driven by the climate emergency and the need for reliable energy for increasingly electrified grids.
In countries like the United States , the shift is already evident. There, the development of advanced geothermal systems has led experts from Princeton University to suggest that, by 2050, geothermal energy could generate almost three times as much electricity as all current US nuclear power plants , which today cover about a fifth of the country's demand.
This shift cannot be understood without considering the impetus provided by the major energy consumers of the 21st century. Tech giants like Google and Meta are seeking emission-free electricity sources that operate continuously to power their mega data centers and artificial intelligence infrastructures —a consumption that is growing at a breakneck pace.
Geothermal energy fills this gap because it offers clean baseload power : it can produce electricity or heat around the clock, without relying on the sun or wind. Furthermore, modern systems allow the subsoil to be used as a thermal energy storage system , smoothing out peak demand and facilitating the integration of other, more variable renewable energy sources.
What exactly is geothermal energy?
The term geothermal energy itself comes from the Greek words geō (earth) and thermós (heat). According to the European Geothermal Energy Council (EGEC) , it refers to energy stored as heat below the Earth's surface , whether in rocks, soil, or groundwater, regardless of its temperature or depth.
It is considered a renewable and low-emission energy source : the Earth's internal heat is virtually 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 conditions , allowing for high and predictable yields year-round.
Depending on the resource and the design of the installation, several types of geothermal energy are distinguished . There are systems that utilize hot underground water, others that extract heat from dry rocks at great depths, dry steam or natural geyser systems, and shallow solutions that use heat exchangers buried a few meters below the surface to heat and cool buildings.
Projects are also classified by temperature and use . High-enthalpy resources (above approximately 150 °C) are primarily used for electricity generation, while medium- and low-temperature resources are ideal for district heating, domestic hot water, industrial processes, or heating swimming pools and tourist facilities.
From conventional geothermal systems to advanced systems
Traditional geothermal energy relies on locating areas with permeable fractures at depths of less than 4 kilometers and temperatures around 150-200 °C. In these natural reservoirs, 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 from enhanced geothermal systems (EGS) and closed-loop systems (CLS) . The former use techniques from the oil and gas sector, such as fracking and multi-sided drilling, to fracture hot rock and create an artificial reservoir where none existed before.
In EGS (Extended Geothermal Systems), companies drill a deep, nearly vertical well , deviate it horizontally at a certain depth, and drill a second, parallel well. The rocks between the two wells are then fractured to create a custom-made reservoir . Cold 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 well to transfer the heat to a secondary circuit that powers a turbine.
CLS systems, on the other hand, do not use hydraulic fracturing. Instead, a closed network of pipes is installed through which a fluid circulates. This fluid is heated upon contact with the hot rock below the surface and returns 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 deep , without relying on naturally fractured zones.
Looking further afield, researchers are investigating drilling into "superheated" zones between 8 and 20 kilometers deep , where temperatures approach 400°C and water enters a supercritical state—a phase neither liquid nor gaseous that can transport significantly more energy to the surface. If these developments come to fruition, 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 Geretsried geothermal project (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 a significant step for advanced geothermal energy in Europe . During commissioning, the thermosiphon effect was successfully verified , allowing the fluid to circulate through the geothermal circuit without the need for pumps once the system is operational.
In Geretsried, the system was started using a compact pump with a flow rate of approximately 3 kg/s , and the thermosiphon stabilized in less than half an hour. After this 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 that it can remain operational for months even under low-load conditions. This flexibility is particularly valuable for electrical systems that integrate high levels of variable renewable energy.
According to the design objectives, the Geretsried site aims to achieve approximately 64 MW of thermal power and 8,2 MW of electrical power , which would prevent the emission of around 44.000 tons of CO2 equivalent each year. The company plans to use this project as a model to expand the technology to other locations in Europe, with future developments already underway in Hanover and Neu-Ulm.
Drilling innovations that lower costs
Beyond the closed-loop concept itself, the experience in Geretsried has served to validate a set of advanced drilling technologies that are critical in high-temperature environments. The company has reported significant improvements in both total drilling time and usable drill bit length.
Among the tools used are the insulated drill pipe (IDP) , which helps to limit thermal losses during operations; active magnetic measurement (AMR) , which improves the control of the well trajectory; and the sealant known as Rock-Pipe , designed to stabilize the drilled sections and extend the reach in extreme conditions.
The combination of these solutions not only allows drilling further and deeper, but also helps reduce development costs , a particularly sensitive point in any geothermal project. A significant portion 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 that will serve as a benchmark for wider implementation in Europe and other continents. In its communications, the company emphasizes that its system is designed to adapt to a wide variety of regions , making it possible to bring geothermal energy to territories without large volcanoes or traditional hydrothermal resources.
In a continent where the pressure to achieve energy security, reduce emissions and make efficient use of land and water is increasing, 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 grid deployment seen in other countries has not yet been achieved, geothermal projects for direct thermal use are beginning to take hold and could pave the way forward. One of the most unique is ConnectHeat Costa Canaria , promoted by the Las Palmas Federation of Hospitality and Tourism Businesses (FEHT) and the Canary Islands Technological Institute (ITC).
This is the first energy community in Europe specifically geared towards the tourism sector , focusing on improving the heating and cooling of swimming pools and thermal systems in accommodation complexes using geothermal energy. The initiative begins in the Playa del Inglés area , in southern Gran Canaria, on a block bordered by Avenida Estados Unidos, Calle Luna, and Paseo Costa Canaria.
Within this area are 15 non-hotel establishments ranging from one to four stars, offering approximately 1.090 beds, as well as eight residential buildings with 149 apartments, a shopping center, and five hotels with nearly 1.573 additional beds. It is, in short, a mature and densely urbanized tourist hub, representative of many destinations in the archipelago.
The project proposes implementing a renewable heating and cooling network 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.
Studies by the ITC indicate that this network could achieve renewable energy coverage of 86% of the area's heating demand, cutting more than half of current emissions associated with these uses. Furthermore, it is estimated that the energy cost for users will be equal to or lower than that of conventional systems , a key factor for the model's acceptance among hotels, apartments, and homeowners' associations.
Cooperative model and European funding
ConnectHeat Costa Canaria is structured as a non-profit cooperative , comprised of 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 with similar energy interests , something essential in complex urban environments.
The total planned investment is around €1,58 million , with an estimated payback period of approximately nine years . The financial burden is eased by incentives from the European Union's CE Implementa program , which will cover around 60% of the budget, thus enabling the energy community to start with a more solid financial foundation.
The FEHT (Federation of Hospitality and Tourism Businesses of the Canary Islands) is confident that the project will not remain an isolated initiative, but rather can be replicated in other tourist areas of the archipelago . The idea is for ConnectHeat Costa Canaria to serve as a demonstration that a well-designed geothermal heating network can improve energy efficiency, reduce emissions, and maintain competitive costs for the accommodation sector.
The ITC's head of renewable energy highlighted the innovative and inclusive nature of the initiative, which is especially useful in highly developed urban areas where the road network and buildings leave little room for installing conventional photovoltaic generation . In these contexts, harnessing the subsoil as a source of heat and cooling can be a practical way to advance decarbonization without requiring major surface-level changes.
Meanwhile, the surge in tourism in the Canary Islands—with winter occupancy rates nearing 85% —reinforces the need to ensure efficient and stable energy systems. For a destination so dependent on its mild climate and comfortable accommodations, reducing energy costs with renewable solutions becomes both an environmental and a competitive advantage.
The emerging landscape, from closed-loop geothermal systems beginning operations in Germany to cooperative heating networks in Gran Canaria, indicates that geothermal energy 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 viable option for providing clean and consistent energy, both in the form of electricity and district heating, and all signs point to its increasing share of the European energy mix in the coming years.
