Turning coal mines in the region of Asturias in Spain to sources of geothermal heating and cooling

Llanes, Principado de Asturias, Spain (source: flickr/ asturzephyra, creative commons)
Alexander Richter 16 Sep 2020

New facilities at abandoned coal mines in the region of Asturias in Northwestern Spain are to bring geothermal heating and cooling to a hospital and research building of a university.

The Hunosa Group has managed to face the challenge of transforming an eminently mining company into a company that is committed to sustainable energy generation, where local renewable energies play a fundamental role, so a recent article in El Economista from Spain. Currently, it can boast of being the architect of the largest geothermal complex in Spain based on the use of mine waters for the air conditioning of various buildings located in the Asturian town of Mieres, which, due to its characteristics in terms of flow, temperature and quality , makes them susceptible for this type of use.  [Austurias is an autonomous community in the Northwest of Spain.]

The Pozo Barredo geothermal project began its journey 14 years ago to solve the very high economic costs derived from the maintenance of water pumping activities in non-active wells, after different studies carried out by the company concluded that the geothermal exploitation of the mine waters had usable potential. It is an innovative solution, an example of a circular economy that creates, from a problem, a source of wealth and a sustainable resource.

These costs are produced because the Asturian coal mines act as a large underground store of water generated by the intense extractive activity developed for more than a century in the interior of the Central Carboniferous Basin of Asturias. During its exploitation, a multitude of infrastructure and start-up work were carried out which, in turn, generated a network of fissures and cavities that increased infiltration and, therefore, the need to pump the flow outside.

When exploitation ceases and pumping stops, a natural flood occurs, so that the water passes to occupy the generated spaces, fissures and, finally, the pores. This controlled flooding process takes place until a minimum safety level is reached. To maintain that level, a constant pumping of water is necessary to avoid possible conditions.

First phase: 4 MW of installed thermal energy generation capacity

The first phase of the geothermal project using water from the Barredo Well, carried out by Hunosa, began in 2006 with the start-up of the first two geothermal facilities to supply heat and cold to two buildings: the Vital Álvarez Hospital. Buylla -with a surface area of ??28,000 m2 and 120 rooms-, and the Research Building of the University of Oviedo on the Barredo Campus. The estimated annual geothermal energy demand of the Hospital is around 7 million kWh, while that of the Research Building exceeds 208,000 kWh.

In 2016, a third facility that supplies geothermal energy was added to the headquarters of the Fundación Asturiana de la Energía (FAEN) – an entity dedicated to the promotion and development of research, technological development and training activities related to energy – which occupies a Rehabilitated building in what was the old compressor room of the same well. The estimated annual energy demand of the building is about 72,000 kWh.

The three installations, carried out independently, have involved an investment of around EUR 1.5 million and add up to a total power of 4 MWt.

During the development and operation of the three projects mentioned and being aware of the technological advances in generation systems (chillers) that allow to produce at conventional heating temperatures with reasonable COPs and, therefore, the integration of all types of buildings, from Hunosa they saw the need to modify their Roadmap for the development of future geothermal projects, since they were encountering various conditioning factors that limited their growth possibilities

On the one hand, the infrastructure in the wells itself makes it technically difficult to add more exchange or impulsion systems to the existing ones. On the other hand, the consumption / distance relationship from potential customers is critical. Added to this is the difficult installation of chillers in the boiler rooms of existing buildings due to issues of installed electrical power and physical space, as well as the fact that recirculating water from the mine can cause scale formation problems in the pipeline. underground distribution.

The conclusion reached by Hunosa was that future projects could not be viewed in a fragmented way for specific clients. In order to extend the potential of the geothermal resource, the most reasonable, profitable and efficient way was to develop a District Heating (or Heat Network) in which, through a distribution network, future clients could join.

Second phase: 2 MW more capacity

In line with this, at the end of 2018 the company began the works of the second phase of the project, the District Heating Pozo Barredo, which ended last summer and whose start-up, scheduled for this spring, has been delayed to this fall due to the coronavirus health crisis.

The new geothermal installation will allow to power the Polytechnic School of Mieres of the University of Oviedo, the Bernaldo de Quirós Secondary Education Institute and the buildings M-9 and M-10 (totaling 248 homes) of the new Vasco Mayacina residential area, all they also in Mieres, with which the three buildings will achieve significant energy savings.

To guarantee the viability of the project, Hunosa also participated in the call for “grants co-financed by the European Union through the European Regional Development Fund (ERDF) in a competitive competition regime to favor the transition to a low-carbon economy in all countries. sectors “with the support of the Ministry of Employment, Industry and Tourism of the Principality of Asturias. The grant awarded slightly exceeded EUR 500,000  for an investment of just over EUR 1.4 million.

The new geothermal heat network will have a capacity of 2 MWt, which, added to the 4 MWt of the three previous installations, will represent a total power close to 6 MWt, making it the first project to be developed as a heat network with a heating system. centralized generation with geothermal mine water.

The estimated annual geothermal energy demand of the Barredo heat network is 2,462.88 MWh, which will cover 100% of the demand for heating and DHW preheating in buildings M-9 and M-10. The commissioning of the entire complex (phase 1 + phase 2) will prevent the emission into the atmosphere of some 636 tons of CO2 per year.

Currently, the Hunosa Group is working on the development of a new Heating District based on mine water from the Fondón Well, located in Langreo (also in Asturias), with the idea of ??being able to replicate the facilities developed in Mieres. Likewise, it analyzes a future hybridization with biomass in Mieres in order to serve a greater number of potential clients.

The project has been awarded a grant from the ERDF Funds of EUR 1.1 million for an estimated investment of EUR 2.2 million. For now, the heat network will serve the La Felguera health center, a residential building and the sports center, a list to which new customers could still join given the capacity of the network. The company estimates that the start-up of this project will prevent the emission into the atmosphere of some 407 tons of CO2 per year.

With this type of project, Grupo Hunosa values ??its own resource (the thermal energy contained in the mine waters), to promote the recovery of local natural resources and the areas affected by mining activity. This project, of marked social interest, innovative and with a low carbon footprint, places Asturian mining regions as a benchmark in the development of new energy projects.

Source: El Economista