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Forética (Metro de Madrid) - Geothermal system for Metro stations

Added on 22-03-2013


Metro de Madrid





Business challenge

The challenge is to reduce the emission of greenhouse gases and to use natural resources to offer more sustainable services through an air conditioning system that uses geothermal energy.


The objective of this initiative is to build an air conditioning system using geothermal energy at metro stations in Spain.

The installation of a geothermal air conditioning system in Madrid's ‘Pacífico' metro station was completed in 2009. This was the first station in our network to use geothermal energy to air-condition its facilities.

Geothermal energy is a renewable energy source that uses the difference in temperature between the subsoil and the surface. The system works as a heat exchanger and is capable of both heating and cooling.  The heat pump transfers heat into the subsoil when functioning as a refrigeration system and absorbs heat from the subsoil when functioning as a heating system.

For this purpose, we have installed a terrestrial heat exchanger made up of 32 tubes, buried in the subsoil at a depth of 150 meters, where the temperature is a constant of 15ºC. Heat pumps connected to the heat exchanger then transfer the heat or cold extracted from subsoil to the distribution system.

This system offers many advantages compared to traditional systems, such as energy savings and greater independence from the electrical supply. Geothermal energy savings reduce CO2 emissions by 50% while also reducing noise pollution, since the heat pumps operate quietly. Other advantages of this system include low maintenance costs and increased useful life of equipment and installation.


We are considering extending this system to other stations.

In order to reduce costs, we plan to use profits from the construction of new stations and/or complete renovation of existing stations to implement a pre-installation of this geothermal system.

Owing to the special characteristics of the Madrid subsoil, Metro de Madrid is also researching the possibility of using some other low enthalpy systems to air conditioning its stations, such as using water collected from the leakage of the water table.

Challenges/Lessons learned:

  • 75% reduction in energy consumption.
  • 50% reduction in CO2 emissions.
  • Sustainable use of natural resources.

More information

This project has been partially subsidized by local (Madrid Community) and national (IDAE Instituto para la Diversificación y Ahorro de la Energía) organizations focused on Energy Saving.

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