The abandoned mine shafts in Asturias don’t appear to be energy resources on a gloomy morning. They appear to be artifacts. headframes with rust. conveyor belts that are quiet. Decades of rain have left streaks on concrete buildings. For many generations, Spain’s industrial growth was fueled by the coal that these pits extracted from deep underground. They are now being asked to do something completely different—keep homes warm—while they are silent and flooded.
Beginning in the north, where coal used to define entire towns, Spain is transforming defunct coal mines into geothermal energy parks. The concept is surprisingly straightforward. After mining ceased, massive reservoirs were created as groundwater gradually filled the huge underground spaces. That rock-insulated water maintains a constant temperature of between 20 and 23 degrees Celsius. Warm enough to make a difference. It’s cool enough to handle.
It’s possible that the empty space left behind was the mines’ greatest asset rather than the coal itself.
For years, engineers have been silently pumping mine water through heat exchangers at Pozo Barredo, one of the first projects associated with Grupo Hunosa. A hospital is among the first buildings to benefit from the transfer of the water’s heat to a secondary clean-water circuit, where it is amplified by heat pumps. There is an odd sense of continuity as you stand close to the location and observe the thick polyethylene pipes that emerge from the former mining compound. The ground is still a source of energy. It simply shows up smoke-free.
| Category | Details |
|---|---|
| Region | Asturias, Northern Spain |
| Key Operator | Grupo Hunosa |
| Academic Partner | Universidad de Oviedo |
| Flagship Sites | Pozo Barredo, Pozo Fondón (Langreo) |
| Average Mine Water Temperature | ~20–23°C |
| Estimated Thermal Capacity | Up to 20 MW (selected sites) |
| CO₂ Reduction (10 MW plant) | ~5,900 tons/year (est.) |
| Technology | Open- and closed-loop geothermal heat pump systems |
| EU Policy Context | Coal phase-out under European closure directives |
| Reference 1 | European Commission Energy Portal: https://energy.ec.europa.eu |
| Reference 2 | Red Eléctrica de España (REE): https://www.ree.es |
The figures are not insignificant. According to studies related to Universidad de Oviedo, under ideal circumstances, three connected mines in the Asturian basin could produce about 20 megawatts of thermal power. Thousands of homes could be heated with that amount. Given the volatility of gas prices and Europe’s ongoing reduction in its reliance on fossil fuels, investors appear cautiously interested.
However, geothermal energy is not inexpensive. It costs a lot of money up front to install circulation systems, heat pumps, and kilometers of insulated pipework. Boilers that run on natural gas are easier. less expensive. Well-known. Whether or not every former mining town will accept the conversion is still up in the air, particularly in areas where the economic wounds from mine closures are still evident.
However, beneath the spreadsheets lies another reality. Continuous pumping is necessary in many of these mines to avoid surface flooding and groundwater rebound. In any case, that pumping is expensive. A small asset can be created by rerouting the warm water through a heat recovery system. It’s difficult to ignore how elegant that is.
The streets of Langreo, close to the Fondón well, exude a calm industrial dignity. Former miners congregate in cafés to talk politics and football. There are skeptics. In contrast to the concrete grime of coal, geothermal parks seem abstract. Others, especially the younger residents, see it as a redeeming thing—work without blackened lungs, energy without dust.
The climate equation is another. When compared to traditional fossil-fuel heating, a 10-megawatt geothermal installation could cut CO2 emissions by about 5,900 tons per year. That decrease is significant in a nation where renewable energy sources already generate a growing portion of the nation’s electricity. Not in a big way. Not in a valiant manner. However, gradually and gradually — which is frequently how changes truly take place.
In technical terms, the systems depend on high-efficiency heat pumps running in mixed-loop or open-loop configurations. Through exchangers, mine water transfers heat before being released or recycled. In person, the procedure feels almost natural, like tapping into a slow, subterranean pulse, even though it sounds clinical on paper. In contrast to air-source systems that struggle in the winter cold, the temperature hardly changes seasonally.
Still, there are unanswered questions. What occurs when a drought lasts a long time? How long-lasting are the hydrochemical characteristics? As infrastructure ages, will maintenance costs gradually increase? Optimism should be measured, according to the history of industrial transformations.
Regional planners have proposed subterranean farming and even energy storage in these enormous spaces, in addition to heating. It’s ambitious—maybe too ambitious. However, Asturias has previously had to reinvent itself. In the past, coal also appeared to be permanent.
All of this has a larger European context. By the end of 2018, the majority of coal production facilities had been phased out in accordance with EU closure directives. There were economic cliffs in places like Asturias. In some ways, turning mines into geothermal parks seems like a narrative correction, demonstrating that decarbonization need not equate to desertion.
There’s a sense that something subtle is changing as you watch the gradual retrofitting of pipes and pumps where coal wagons once rattled. Not a lot of green change. Not a breakthrough that would make headlines. It’s more like a silent industrial afterthought finding its way.
Spain may not be able to meet all of its heating needs with its plan to turn abandoned mines into geothermal energy parks. It won’t take the place of massive solar arrays shimmering across the plains or offshore wind farms. However, there is heat waiting to be used deep underground in chambers filled with water that were carved by the aspirations of a century ago.
