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Geothermal power in metro station facilities

Powering 127 homes and two office areas

The rise in the consumption and cost of energy sources, and the desire to reduce greenhouse gas emissions, mean that geothermal energy is now more attractive than ever. By capitalising on its synergies and partnerships, Egis was keen to improve the technical framework (currently still at the experimental stage) in the field of geothermal piles. An exciting challenge launched during the creation of a second metro line in Rennes and a first in France.

Métro Rennes géothemie 2 © Egis

In December 2010, Rennes Métropole entrusted Egis with the EPCM (infrastructure and buildings) for line B of the Rennes metro, with one key challenge: the integration of geothermal energy in four stations. Not to heat or cool the stations, as had already been done in Austria, but to supply power to the 127 homes and two office areas that will be built over this transport line in coming years. Using walls in direct contact with the ground, the geothermal system will recover heat during the winter and cold air in summer. Heat pumps will collect low-temperature energy from the ground and bring it to a temperature sufficient for heating buildings, i.e. temperatures between 30°C and 75°C. The stations’ concrete walls are used as thermal storage.

Adapting a very low energy technique for geothermal capture to a complex civil engineering work

The innovation focused on analysing the behaviour of a structure under unusual thermal loads, and the incorporation of a geothermal system into a civil engineering structure.
Delivery is scheduled for 2019/2020.
In terms of sustainable development, in addition to the geothermal aspect, other features make this an exemplary project:

  • a maintenance workshop heated with wood and powered by photovoltaic panels
  • the choice of a low carbon footprint cement
  • lighting with presence detection for the site facilities…

These are all examples of the project owner’s desire to control energy costs at all stages.