The importance of near-surface geothermal energy in Bordeaux Metropole’s energy plan

The need

The aim of the climate plan adopted by Bordeaux Métropole in 2017 is for the region to achieve a positive energy tipping point by 2050, with ambitious targets for controlling energy consumption and increasing the use of renewable energies. To this end, the intention is to mobilise geothermal resources as a major lever; however, on a local scale, the information on near-surface geothermal energy sources is not yet available to project developers. The aim of this joint project was to raise awareness of these solutions and encourage the emergence of geothermal energy projects in the region.

The results

BRGM's programme of work between 2018 and 2023 was focussed on three areas:

• A map of near-surface geothermal resources was drawn up with consolidated decision-making data (locations, properties), at a scale adapted to the needs of decision-makers, around a three-dimensional geological model. Investigations focused in particular on the thermal characteristics of the subsurface, with i) the collection of borehole data to assess the expected temperatures in each aquifer, and ii) the implementation of thermal response tests, supplemented by temperature profiles, which led to the proposal of a methodology adapted to the region;
• Although in terms of covering energy needs, the project encountered a lack of sufficient geolocated data on consumption and needs, the focus on certain well-documented types of buildings nevertheless revealed a definite potential for conversion to near-surface geothermal energy for most of the region;
• Finally, the support provided to project developers showed that by providing factual information, the majority of developers were able to direct their project towards a geothermal solution.