• Energy Research

The question of storing energy in France has become of primary importance since the launch of a road map from the government which places in pole position this topic among seven major milestones to be challenged in the context of the development of innovative technology in the country. The European objective to reach 20% of renewables in the energy market, from which a large part would come from wind and solar power generation, raises several issues regarding the capacity of the grid to manage the various intermittent energy sources in line with the variability of the public demand and offer. These uncertainties are highly influenced by unpredictable weather and economic fluctuations. To facilitate the large-scale integration of variable renewable electricity sources in grids, massive energy storage is needed. In that case, electric energy storage techniques involving the use of underground are often under consideration as they offer a large storage capacity volume with a adapted potential of confining and the space required for the implantation. Among the panel of massive storage technologies, one can find (i) the Underground Pumped Hydro-Storage (UPHS) which are an adaptation of classical Pumped Hydro Storage system often connected with dam constructions, (ii) the compressed air storage (CAES) and (iii) the hydrogen storage from conversion of electricity into H2 and O2 by electrolysis. UPHS concept is based on using the potential energy between two water reservoirs positioned at different heights. Favorable natural locations like mountainous areas or cliffs are spatially limited given the geography of the territory. This concept could be extended with the integration of one of these reservoirs in an underground cavities (specifically mined or reuse of preexisting mines) to increase opportunities on the national territory. Massive storage based on compression and relaxation of air (CAES) requires high volume and confining pressure around the storage that exists naturally in the underground and which increases with depth. However, the move to an interesting efficiency requires that the heat generated during compression can be stored and used during expansion. This storage can be also underground. H2 underground storage is part of the "Power to gas" concept which allows for converting electricity into a gas available for either electrical or gas grid. Each of these techniques requires the selection of appropriate geological formations which contains specific characteristics in agreement with several criteria under consideration when choosing electric energy storage methods for application (lifetime, life cycle, discharge rate, environmental impact, public acceptance ...). We propose in this paper a preliminary review of the potential massive electric energy storage capacities in France of using specific geological formations (salt, basement) and the various physical phenomena linked to the couple geology/technology. Several approaches and methodologies developed formerly with other applications (geothermal, CO2 storage, heat storage ...) will be used to investigate rock mechanical integrity, geochemical and thermal environmental impacts associated to these innovative technologies.

The question of storing energy in France has become of primary importance since the launch of a road map from the government which places in pole position this topic among seven major milestones to be challenged in the context of the development of innovative technology in the country. The European objective to reach 20% of renewables in the energy market, from which a large part would come from wind and solar power generation, raises several issues regarding the capacity of the grid to manage the various intermittent energy sources in line with the variability of the public demand and offer. These uncertainties are highly influenced by unpredictable weather and economic fluctuations. To facilitate the large-scale integration of variable renewable electricity sources in grids, massive energy storage is needed. In that case, electric energy storage techniques involving the use of underground are often under consideration as they offer a large storage capacity volume with a adapted potential of confining and the space required for the implantation. Among the panel of massive storage technologies, one can find (i) the Underground Pumped Hydro-Storage (UPHS) which are an adaptation of classical Pumped Hydro Storage system often connected with dam constructions, (ii) the compressed air storage (CAES) and (iii) the hydrogen storage from conversion of electricity into H2 and O2 by electrolysis. UPHS concept is based on using the potential energy between two water reservoirs positioned at different heights. Favorable natural locations like mountainous areas or cliffs are spatially limited given the geography of the territory. This concept could be extended with the integration of one of these reservoirs in an underground cavities (specifically mined or reuse of preexisting mines) to increase opportunities on the national territory. Massive storage based on compression and relaxation of air (CAES) requires high volume and confining pressure around the storage that exists naturally in the underground and which increases with depth. However, the move to an interesting efficiency requires that the heat generated during compression can be stored and used during expansion. This storage can be also underground. H2 underground storage is part of the "Power to gas" concept which allows for converting electricity into a gas available for either electrical or gas grid. Each of these techniques requires the selection of appropriate geological formations which contains specific characteristics in agreement with several criteria under consideration when choosing electric energy storage methods for application (lifetime, life cycle, discharge rate, environmental impact, public acceptance ...). We propose in this paper a preliminary review of the potential massive electric energy storage capacities in France of using specific geological formations (salt, basement) and the various physical phenomena linked to the couple geology/technology. Several approaches and methodologies developed formerly with other applications (geothermal, CO2 storage, heat storage ...) will be used to investigate rock mechanical integrity, geochemical and thermal environmental impacts associated to these innovative technologies.

In Europe, most data relevant to energy storage exists in a fragmented form. The major work in the ESTMAP project therefore consisted of compiling existing data in a unified database and exploiting it to optimize energy systems planning. Geologists, engineers and system modellers joined forces to define the format and the content of a database of both subsurface (i.e. in sedimentary basins) and above surface storage sites (existing, planned and potential). The idea is to ensure that the newly compiled dataset will fit the needs for robust modelling, planning and designing on a coherent basis and comparable among Member States and other European neighbouring countries. One of the project output consisted of a geographical database providing information on distribution and expected capacity of existing and future energy storage sites in Europe. Both subsurface storage options (hydrogen, compressed air, natural gas, underground pumped hydro, etc.) and above ground storages (pumped hydro, LNG, liquid air, etc.) were taken into account.In this project, BRGM, assisted by TNO, CGS and VITO, was in charge of data collection for underground energy storage (mainly in sedimentary basins), in order to gather readily available and public data on existing and future potential storage sites. These data incorporate the geographic location, geological description and characterization, subsurface properties, and feasibility and capacity assessments of the subsurface reservoirs (aquifers, salt formations and caverns, depleted hydrocarbon reservoirs…).A co-operation with European national geological institutions has been established; the ESTMAP geological subsurface database populates data from EU member countries, the countries of the European Free Trade Association-EFTA (4 countries) and the Member of the Energy Community (8 countries). About 1000 subsurface sites spread around Europe have been identified during the subsurface data collection. All of them have assessment information per technology, in term of proven, likely, possible, unknown, or unlikely feasibility of energy storage.All these data were forwarded for integration in the database to compute further pan-European and regional energy system analyses. The ESTMAP project provided the opportunity to review the available public geological subsurface data in the European countries. These encouraging results let open the possibility for further European cooperation in the future.

In Europe, most data relevant to energy storage exists in a fragmented form. The major work in the ESTMAP project therefore consisted of compiling existing data in a unified database and exploiting it to optimize energy systems planning. Geologists, engineers and system modellers joined forces to define the format and the content of a database of both subsurface (i.e. in sedimentary basins) and above surface storage sites (existing, planned and potential). The idea is to ensure that the newly compiled dataset will fit the needs for robust modelling, planning and designing on a coherent basis and comparable among Member States and other European neighbouring countries. One of the project output consisted of a geographical database providing information on distribution and expected capacity of existing and future energy storage sites in Europe. Both subsurface storage options (hydrogen, compressed air, natural gas, underground pumped hydro, etc.) and above ground storages (pumped hydro, LNG, liquid air, etc.) were taken into account.In this project, BRGM, assisted by TNO, CGS and VITO, was in charge of data collection for underground energy storage (mainly in sedimentary basins), in order to gather readily available and public data on existing and future potential storage sites. These data incorporate the geographic location, geological description and characterization, subsurface properties, and feasibility and capacity assessments of the subsurface reservoirs (aquifers, salt formations and caverns, depleted hydrocarbon reservoirs…).A co-operation with European national geological institutions has been established; the ESTMAP geological subsurface database populates data from EU member countries, the countries of the European Free Trade Association-EFTA (4 countries) and the Member of the Energy Community (8 countries). About 1000 subsurface sites spread around Europe have been identified during the subsurface data collection. All of them have assessment information per technology, in term of proven, likely, possible, unknown, or unlikely feasibility of energy storage.All these data were forwarded for integration in the database to compute further pan-European and regional energy system analyses. The ESTMAP project provided the opportunity to review the available public geological subsurface data in the European countries. These encouraging results let open the possibility for further European cooperation in the future.

The major hurdle of energy transition in France is the energy storage, since the renewable sources with great potential (wind and solar) are highly intermittent. The FLUIDSTORY project, funded by ANR explores the innovative concept consisting in storing energy trough fluids vectors (O2, CO2 and CH4) in salt caverns. The Electrolysis–Methanation–Oxy-fuel (EMO) concept is designed to bring a closed-loop solution able to absorb renewable electricity surplus and recover it later, via the transient storage of O2, CO2 and CH4. During the storage phase, the electric energy excess is used in an electrolysis process. The resulted O2 is stored, while H2 is combined with CO2 in a methanation process. CH4 formed is also stored. During the retrieval phase, electric energy is produced in a thermal generator, where the fuel is the methane and oxygen previously stored. The produced CO2 is in turn stored for later use in the methanation process.The main objectives of the FLUIDSTORY project are to study the operability, the safety and the integrity of O2 and CO2 storage in salt caverns as well as to investigate the medium to long term (2030-2050) requirements for reaching the energy efficiency and economic profitability of the EMO concept in France.In order to achieve this goal, availability of storage volumes required by EMO development has to be investigated through systematic inventory of the existing salt caverns and geological study of suitable salt formations.We present the main results of the inventory of the French salt formations and estimation of the French geological energy storage potential. It consists in an exhaustive inventory of salt formations in France with a special focus on halitic series. This review is based on public and accessible data.Six sedimentary basins were targeted: Paris Basin, Aquitaine Basin, South-East Basin, Valence Basin, Bresse Basin and Upper Rhine Graben. For each basin, we looked for:•the general lithostratigraphy: Position of the evaporitic series in the sedimentary pile and relationship between evaporites and the caprock;•the geographical extension of the evaporitic series;•the depth and thickness of the evaporitic series;•Nature and content of insoluble rocks.Two main conclusions can be drawn from this inventory:•Salt bearing series of the Paris Basin (Lorraine region) are shallow and thin enough to satisfy the operational constraints of a small storage operated at low pressures.•Evaporitic series of Apt-Forcalquier, Valence, Bresse or Mulhouse Tertiary basins may be interesting targets for larger storages. Their depths are great enough to increase operating pressures compared to the Paris Basin.This work will be then valued in the techno-economical tasks of the project. Storage capacity needs for optimal use of EMO technology will be assessed in order to define the optimal location for the EMO technology deployment in France.

The major hurdle of energy transition in France is the energy storage, since the renewable sources with great potential (wind and solar) are highly intermittent. The FLUIDSTORY project, funded by ANR explores the innovative concept consisting in storing energy trough fluids vectors (O2, CO2 and CH4) in salt caverns. The Electrolysis–Methanation–Oxy-fuel (EMO) concept is designed to bring a closed-loop solution able to absorb renewable electricity surplus and recover it later, via the transient storage of O2, CO2 and CH4. During the storage phase, the electric energy excess is used in an electrolysis process. The resulted O2 is stored, while H2 is combined with CO2 in a methanation process. CH4 formed is also stored. During the retrieval phase, electric energy is produced in a thermal generator, where the fuel is the methane and oxygen previously stored. The produced CO2 is in turn stored for later use in the methanation process.The main objectives of the FLUIDSTORY project are to study the operability, the safety and the integrity of O2 and CO2 storage in salt caverns as well as to investigate the medium to long term (2030-2050) requirements for reaching the energy efficiency and economic profitability of the EMO concept in France.In order to achieve this goal, availability of storage volumes required by EMO development has to be investigated through systematic inventory of the existing salt caverns and geological study of suitable salt formations.We present the main results of the inventory of the French salt formations and estimation of the French geological energy storage potential. It consists in an exhaustive inventory of salt formations in France with a special focus on halitic series. This review is based on public and accessible data.Six sedimentary basins were targeted: Paris Basin, Aquitaine Basin, South-East Basin, Valence Basin, Bresse Basin and Upper Rhine Graben. For each basin, we looked for:•the general lithostratigraphy: Position of the evaporitic series in the sedimentary pile and relationship between evaporites and the caprock;•the geographical extension of the evaporitic series;•the depth and thickness of the evaporitic series;•Nature and content of insoluble rocks.Two main conclusions can be drawn from this inventory:•Salt bearing series of the Paris Basin (Lorraine region) are shallow and thin enough to satisfy the operational constraints of a small storage operated at low pressures.•Evaporitic series of Apt-Forcalquier, Valence, Bresse or Mulhouse Tertiary basins may be interesting targets for larger storages. Their depths are great enough to increase operating pressures compared to the Paris Basin.This work will be then valued in the techno-economical tasks of the project. Storage capacity needs for optimal use of EMO technology will be assessed in order to define the optimal location for the EMO technology deployment in France.

AbstractFrance Nord project is a Joint Industry Project that has grouped 4 public research institutes (BRGM, IFPEN, INERIS and Eifer) and 7 industrial partners (Total, GDF SUEZ, Storengy, EDF, Air Liquide, Lafarge and Vallourec) from 2008 to 2012. The first step of the France Nord project was to identify in the deep saline aquifers of the Paris Basin a geological site providing a storage capacity of at least 200 Mt of CO2 during 40 years of injection. This level of capacity is considered as appropriate for a project of industrial size. In parallel, a review of the CO2 emitters in Northern France was performed and potential CO2 transportation solutions were reviewed. The second step was to implement a CCS pilot in a CO2 storage target identified previously. An R&D program has also been implemented, reviewing key elements of the CCS chain.Five potential CO2 storage targets were analyzed in detail, following a regional geological assessment, a geological modeling and dynamical flow simulations. However, on the basis of available data, it was not possible during the project to identify a CO2 storage site with the target capacity of 200 Mt of CO2. As a consequence, the demonstration pilot was not implemented.These results are discussed and compared to past CO2 storage assessments of the Paris Basin that provided much higher estimations of the saline aquifer CO2 storage capacity of the basin.