Hidden geothermal energy under six Tarragona municipalities could power a new phase of the energy transition
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Image : A Geothermal Power Plant gushing steam to power a grid
A renewable resource beneath the ground
A new study in Tarragona has revealed that geothermal energy could become a major local source of heat and cooling for six municipalities: Ascó, Mont-roig del Camp, Montbrió del Camp, Flix, Ulldemolins, and El Perelló . The research suggests that shallow geothermal systems could supply hundreds of buildings and public facilities with a steady, renewable, and locally available energy source .
The idea is compelling because it combines climate action with territorial resilience. Instead of depending entirely on imported energy or weather-dependent renewables, these towns could tap into the stable temperature of the subsoil to produce heating, cooling, and domestic hot water . For a region that is already managing the transition away from nuclear dependence, this could become a valuable tool for the next stage of energy planning .
What shallow geothermal energy is
Shallow geothermal energy uses the first 200 meters of the ground to capture stable underground temperatures . Through boreholes and a network of pipes, heat is transferred to a heat pump, which then turns that energy into heating, cooling, or hot water for buildings [1].
This is not a futuristic concept. It is a well-established technology that works especially well in places where municipalities want to reduce emissions without sacrificing comfort or reliability . Because the underground temperature remains relatively constant throughout the year, shallow geothermal systems can provide an efficient backbone for district heating and cooling networks .
Why Tarragona stands out
The Tarragona study is notable because it was not limited to a single site. It explored six municipalities and found encouraging conditions in all of them, with different levels of potential depending on local geology, demand, and budget . The work was carried out by the Institut Cartogràfic i Geològic de Catalunya, under the Department of Territory, Housing and Ecological Transition, and the results were delivered as a preliminary project to local councils and the Department of Enterprise .
The study was financed through the Nuclear Transition Funds, a mechanism designed to support areas affected by the future shutdown of the Ascó and Vandellòs nuclear plants. That context matters because it shows how a fund linked to nuclear transition can help generate a different kind of energy future, one based on local renewables and municipal infrastructure
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Ulldemolins: the clearest plan
Ulldemolins appears to have one of the most defined proposals. According to the study, around 90 wells could connect 135 buildings and 285 public and private facilities, covering roughly one third of the municipality [1]. The local government sees the project as technically viable and strategically attractive [1].
Still, the financial challenge is serious. The initial investment is estimated at about two million euros, while the municipality’s annual budget is only around 1.5 million [1]. That gap shows the central dilemma facing many small towns: the technology may be feasible, but the capital required to launch it is often beyond local reach .
Flix: energy resilience and local confidence
Flix is another municipality where the idea has gained traction. Mayor Francesc Barbero said the town is excited to explore these renewable energy options and sees geothermal power as a stabilizing factor in a place with strong seasonal temperature swings . That makes sense in a town where reliable, affordable energy can improve both comfort and long-term planning.
The project in Flix is still considered medium-term, and subsidies will be essential to move it forward . The estimated cost is around four million euros, which means the municipality will likely need a blend of public funding and institutional support before construction can begin . Even so, the interest shown by the local leadership suggests that geothermal energy has moved from theory to serious consideration .
Montbrió del Camp and the thermal anomaly
Montbrió del Camp sits in a particularly interesting geological setting, in the triangle formed with Botarell and Riudecanyes, within the Camp Fault zone . The article notes the presence of thermal waters that rise to the surface in the form of spa activity, which points to a much deeper geothermal potential below ground.
At a surface level, Mayor Carmina Blay said a geothermal network would be technically viable, although economically difficult, with costs estimated at 2.8 million euros against a municipal budget of three million . The preliminary design would require 152 wells to supply 99 blocks and 217 heated facilities [1]. That is a substantial infrastructure footprint, and it highlights how geothermal systems can be scaled to match dense local demand.
Ascó and the post-nuclear transition
Ascó offers a powerful symbolic case because it is already deeply associated with nuclear energy and is now looking at a different kind of local energy future [1][3]. The study suggests that 84 wells at a depth of 120 meters could cover about one third of the municipality .
Mayor Miquel Àngel Ribes described the opportunity as both a privilege and a chance to make use of an energy source that contributes to environmental goals . The estimated cost is about 1.5 million euros, and the municipality is exploring financing options . In that sense, Ascó illustrates how energy transition is not only about replacing one system with another, but about reshaping the identity of a territory that has long depended on a single energy model
Mont-roig del Camp and urban efficiency
Mont-roig del Camp is focusing on La Florida, in Miami Platja, as the most promising area for geothermal deployment . The municipal view is that this district contains a high concentration of public facilities and municipal buildings, making it well suited to a shared thermal network .
That is a smart approach because geothermal district heating works best where demand is concentrated and can be efficiently shared. The municipality is now awaiting the possibility of applying for support from IDAE, Spain’s Institute for Energy Diversification and Saving . If funding is secured, Mont-roig could become a strong example of how urban planning and energy policy can work together in a practical way .
El Perelló and the value of waiting
El Perelló is still awaiting the final results, but the tone from the municipality is positive Mayor Samuel Ferré welcomed the possibility of benefiting from this model and confirmed that the town sees real value in the technology .
The system under discussion is a fifth-generation smart climate network based on low temperatures and high efficiency . That matters because it shows the project is not just about extracting underground heat, but about building a smarter energy distribution model for the future. For smaller municipalities, the appeal lies in its ability to reduce emissions while improving long-term energy control .
The funding challenge
Across all six municipalities, the biggest obstacle is not technical feasibility but upfront cost . Geothermal networks require a substantial initial investment, and that can be difficult for towns with limited annual budgets
This is why access to public support is so important.
The Nuclear Transition Funds are playing a central role here, but additional support may also be needed from regional, national, or European programs . Without that financing layer, many promising projects risk remaining on paper. With it, they could become durable public infrastructure that reduces emissions, supports local jobs, and lowers energy costs over time .
Why this matters now
The timing is significant because energy transition in Tarragona is entering a more practical phase . The region is already managing the economic and social implications of nuclear decline, and geothermal energy offers a way to turn underground assets into local resilience . That makes the study more than a technical report; it is a roadmap for adaptation.
It also broadens the conversation about renewable energy. Solar and wind remain essential, but they are not always enough to serve heating and cooling needs at the municipal level . Geothermal energy can fill that gap with a stable, local, and low-carbon solution . For city councils and rural towns alike, that is a powerful proposition.
A territorial opportunity
The six municipalities in this study each have different circumstances, but they share a common opportunity: to transform part of their energy demand through a local renewable resource. Some are ready to move faster than others, and some face steeper budget barriers, but all of them now have a clearer picture of what is possible .
That is why this story matters beyond Tarragona. It shows how a region can use geological knowledge, public funding, and local governance to unlock a clean-energy option that had previously been underused . In a time when energy systems are under pressure, that kind of practical innovation is exactly what many territories need .
A future built underground
What lies beneath Tarragona is not just warm rock or water; it is strategic potential . The study shows that geothermal energy could help supply hundreds of buildings, reduce emissions, and strengthen local autonomy in six municipalities with very different profiles [1]. For residents, that could mean better comfort and lower carbon impact. For councils, it could mean a smarter way to plan the next decade of energy investment.
The real story here is not that the resource exists. It is that the region is beginning to see it clearly, measure it carefully, and plan around it . That is how an underground resource becomes a public opportunity.
Source : diaridetarragona
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