Storage and transport: the two major challenges of hydrogen deployment

Decarbonizing processes, including thermal processes, while guaranteeing the flexibility of the electricity network and the country's security of supply: the hopes raised by hydrogen are immense. Because everywhere, the idea is spreading that this vector could well meet many of the challenges posed by the energy transition, from the intermittency of renewables (wind or solar) to the persistent dependence on fossil fuels. Until replacing, by 2050, the natural gas circulating in our pipelines with a new network of low-carbon gas pipelines, weaving its web between hydrogen production, storage and consumption sites?

The subject, in any case, agitates both industrialists and public authorities. Last November, Emmanuel Macron announced to devote 1.9 billion euros to the development of "gigafactories" of electrolyzers as part of the France 2030 investment plan, in addition to the 7 billion euros already put on the table by the executive. A month later, the France Hydrogène association published a white paper with great fanfare to "make presidential candidates aware that the next five-year term will be decisive for the take-off of the sector", and encourage them to "invest even more". . Same story on the energy side, with an escalation of promises on what Engie now considers "the missing link to decarbonize". Mass has been said.

And yet, according to the manager of the electricity transmission network RTE, a central question remains unanswered: how to store and deploy hydrogen concretely on the territory? Indeed, advances RTE, the establishment of such logistics actually involves taking up a large number of “technical and technological bets”. While Engie asserts, on the contrary, that hydrogen proves to be "easy to transport and store", and that the challenge consists rather in massiveizing its "green" production (when 90% of the hydrogen in the world comes from steam reforming of hydrocarbons today), who should we believe?

No proven storage solution

First, it must be understood that no technique for storing electricity over the long term (and on a large scale) exists yet. In this respect, hydrogen could meet this need. And thus guarantee France its security of supply, when controllable energy sources (notably fossil fuels) will have to decrease to preserve the climate, and the share of renewable energies with intermittent production will continue to grow in the overall mix. Thus, the current from wind turbines or photovoltaic panels would make it possible to create this hydrogen by electrolysis of water, before it is stored in the basement in gaseous form... then returned during production lows.

An attractive idea on paper. However, in fact, “the availability” of these “storage infrastructures” is not today “certain”, he specifies. Saline cave storage demonstrators do exist, in particular the HyPSTER project by Storengy (Engie subsidiary), in Ain, “the most advanced” and currently “in the engineering phase”. Costing 13 million euros, its objective is "to adapt the well which connects the surface to the saline cavity from the summer of 2022" and "to start cycling three tonnes of hydrogen from 2023", explains on at the French leader in underground gas storage. And this, until the use of the total capacity of the identified salt cave, ie 44 tons.

Technical brakes

But according to engineer Ludovic Leroy, who provides training for professionals in the energy world, threshold studies have in fact still not started. “They haven't injected a single molecule of hydrogen into it. They are trying to redefine the compressor [the device which increases the pressure of the gas by reducing its volume, editor's note], this one not being adapted to hydrogen. In fact, this type of salt cavern storage has so far only worked in Texas and the UK, and only for a very short storage time,” he says. And for good reason, beyond just a few days, the hydrogen risks becoming charged with sulfur due to the micro-organisms in the cavity, requiring downstream desulphurization.

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In Storengy, the existence of “technical brakes” is indeed admitted. “We must check that the equipment used today with methane can be adapted for hydrogen, that the seal is suitable, and that all the surface equipment is in place. We have to get it to work, and for that we benefit from European subsidies”, argues Camille Bonenfant-Jeanneney, general manager of Storengy.

However, even if the solution were finally approved in the long term, the salt cavities remain “limited in number” on the territory, and the possibility of developing new sites is still “uncertain”, estimates Thomas Veyrenc.

Read also: In Ain, Hypster wants to disrupt the green hydrogen storage sector

Moving from tankers to gas pipelines

Above all, these should be connected to a global hydrogen transport infrastructure, rather than passing through tanker trucks, as planned in the HyPSTER project. A subject taken head-on by the two gas transmission network operators in France, GRTGaz and Téréga. But also at European level: by 2040, a backbone of nearly 40,000 kilometers could cover 21 countries on the continent, in order to limit the costs of distribution to a few euro cents per kilometer by massifying the process. In France, GRTGaz is notably responsible for the Mosahyc project on the Franco-German border, 100 kilometers long. As for Téréga, with the Lacq project, it hopes to connect France and Spain from 2025 in order to transport pure hydrogen there, “if the market conditions are met”.

Because to do this, many obstacles must still be removed. Indeed, beyond safety issues (hydrogen being highly flammable), methane pipes were not designed to transport hydrogen, whose molecules are so small that they can diffuse into the metal structure and weaken it.

Especially since the energy density of hydrogen, from the point of view of its volume, is four times lower than that of natural gas. In other words, to obtain the same number of megajoules transported, it will be necessary to multiply the flow rates in volumes by four.

Arbitration on exchanges between countries

For their part, GRTGaz like Terega want to be reassuring: almost half of their current pipes would already be compatible with the injection of 100% hydrogen. “It will be necessary to check that the existing equipment, valves and compressors are suitable. But there will be no major work in terms of piping,” says Geoffroy Anger, in charge of business development for hydrogen transport at GRTGaz. And even for pipes that will need to be modified, the process should prove to be “economically optimal” quickly, the company says.

In any case, political arbitration will have to guide the development of this future network. Because while Germany, Spain or the Netherlands plead for sustained exchanges of hydrogen between the various European countries, Emmanuel Macron seems to favor the most concentrated production, consumption and storage possible, in order to limit transportation. For good reason, France has an “advantage over other large countries” because it has “a solid, installed nuclear power” which allows it to “produce hydrogen much more massively”, according to the Head of State. The fact remains that before any political decision, the gas transmission network operators intend to broaden the outlook.

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