As part of its hydrogen plan, France is initially pursuing two major objectives: decarbonising industry and replacing fossil fuels for heavy mobility. But in the longer term, this tiny molecule could also play a key role in stabilizing the electricity grid and thus securing the country’s electricity supply.
Hydrogen can in fact be used to store electricity over long periods, in particular that produced from intermittent renewable energies, such as solar photovoltaic and wind power.
Concretely, during a peak of production (in spring, for example, where there can be a lot of wind in certain regions), the electricity generated from a wind farm could supply an electrolyser which makes it possible to dissociate a molecule of water into oxygen and hydrogen. The hydrogen obtained, without CO2 emissions, is then stored. It can be restored in electricity, thanks to a fuel cell, when the production of renewable energies will not be sufficient to cover all the electricity consumption needs (in winter in particular). This is called seasonal storage.
Not necessary before 2035
According to an RTE report, the operator of the electricity transmission network, however, hydrogen storage will not be necessary before 2035.
“By 2035, the electricity system will still have a great deal of flexibility, like existing thermal power plants. And a large part of nuclear reactors will remain in service at that time. On the other hand, after 2035, needs can emerge in particular in scenarios of strong development of renewable energies “, explains RTE.
In France, a report recently confirmed the feasibility of an electricity system tending towards 100% renewable energies by 2050, while today solar and wind power represent less than 20% of the French electricity mix and nuclear more than 70%.
Store over long periods of time
For RTE, this strong penetration of intermittent renewable energies represents a major challenge. The manager must in fact permanently guarantee a balance between demand and production of electricity. This is the sine qua non for each consumer to have electricity at all times. In a configuration where renewable energies are largely dominant, the tools to manage this variability, such as storage, are therefore essential.
Unlike batteries, which store electricity for only a few hours, hydrogen can store much larger volumes of energy over long periods of time. The hydrogen could thus be stored in saline cavities (cavities dug in deep and thick layers of rock salt, obtained by injecting water which gradually dissolves part of the salt) over an entire season.
In Ain, Storengy, a subsidiary of Engie, is already experimenting with this type of storage, with the HyPSTER demonstrator. The objective is to define the best technical and economic conditions for storing green hydrogen using an existing micro-cavity of 8,000 cubic meters.
“On this more distant horizon, we believe that hydrogen storage can have its place, even in scenarios where the nuclear fleet is renewed”, affirms RTE.
Hydrogen power plants to be industrialized
It remains to determine the hydrogen storage capacities that will be necessary according to the scenarios selected. “Several levels of revival of the nuclear fleet are possible. [Le gouvernement doit confirmer ou non le lancement d’un nouveau programme nucléaire en 2023, ndlr] If there is a strong recovery and nuclear still represents 50% of the electricity mix, the needs will not be the same as if the government only relaunches a few reactors or even none “, explains RTE. To answer these questions, the network manager will publish a long-awaited report next fall.
RTE will also have to look into the question of the technological maturity of hydrogen storage.
“Today, these hydrogen power plants do not yet exist commercially,” emphasizes RTE. “For the time being, there are only experiments or prototypes. It is necessary to develop a proactive roadmap for the industrial deployment of these hydrogen plants”, adds the manager.
François Kalaydjian, Director of Economics and Strategic Watch at IFP Energies nouvelles, however wonders about the economic viability of such a storage system:
“If the electrolysers only work when there is a surplus of electricity production, this poses the problem of their profitability. Because an electrolyser of industrial size can come close to the billion investment. How to make it profitable if it does not operate continuously ? “
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FRAMEWORK – In Corsica, “the sun is already bottled” thanks to hydrogen
In Corsica, the use of hydrogen to store renewable electricity is already a reality. As early as 2012, the University of Corsica Pasquale Paoli, the CEA and the company Helion launched the Myrte research platform (for Renewable hydrogen mission for integration into the electricity grid). Located near Ajaccio, it aims to study the deployment of photovoltaic energy storage via hydrogen in order to guarantee the power of renewable energies. Objective: to improve the management and stabilization of the electricity network.
This early interest in hydrogen as a storage vector is directly linked to the characteristics of an island territory, disconnected from the network. “Corsica is not self-sufficient in energy, it imports diesel to run thermal power stations”, explains Christian Cristofari, a professor at the University of Corsica. As a result, electricity is more expensive and more carbon than in the metropolis. “In Corsica, energy is seven times more carbonaceous than in mainland France. It is on average twice as expensive, or even five times more expensive during peaks in consumption, between 6 p.m. and 10 p.m., when it reaches 450 euros per megawatt. hour”, details Christian Cristofari. In addition, the island cannot integrate more than 30% of renewable energies in its mix because of their intermittence.
On the Myrte platform, a 560 KW solar power plant supplies a 150 KW electrolyser to produce hydrogen. This is stored and then the electricity is returned thanks to a fuel cell during peak consumption. “We bottle the sun”, summarizes the academic. “We then arrive at costs of 300, 350 euros per megawatt-hour”, he specifies. In order to make this hydrogen chain profitable, the fuel cell is also used to produce heat for buildings. Some of the hydrogen must also be used to serve heavy mobility, especially rail. The next step for the research teams: spreading this system across the island as part of a hydrogen plan.
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