Austrian gas storage operator RAG aims to store 10TWh of hydrogen from 2030–35, anticipating a shift away from natural gas by 2050. But converting underground storage facilities to store hydrogen instead of natural gas will result in a loss of two-thirds of these reservoirs’ energy content, according to CEO Markus Mitteregger.

“One cubic metre of gas is roughly 10kWh, and the same cubic metre of hydrogen has just 3[kWh]. So you are losing two-thirds of the energy. That means, even if you increase the volume, the content of the energy is less,” he says. He anticipates that RAG will have to retain its current natural gas storage capacity in the 2030s to sustain continued demand from gas-fired power plants, while also developing at least 2–3 new reservoirs to store hydrogen.

“By 2050, we have more or less just hydrogen—if everything comes true—so we have to adapt. This is one of the major drivers for us. We have to adapt according to the new sustainable, renewable world,” Mitteregger says.

More reservoirs, less energy

RAG operates 11 porous storage facilities with a combined capacity of 6.3bn m³, although the timeline for converting each of these will be “situational… depending on reservoir characteristics but also on excess electricity availability” and the timing of large-scale imports, Mitteregger tells Hydrogen Economist.

It is also “too early to say” what the cost of converting RAG’s large-scale facilities, such as the 2.9bn m³ Haidach site, will be, he adds. RAG’s recent 1.2mn m³ pilot project in Rubensdorf cost €20mn ($22mn) to develop, €4–5mn of which was spent on the electrolyser and €5mn on an 8km pipeline to facilities offsite.

“Up to 2050, we could have 10bn m³ of storage capacity, but with a third of the energy content” Mitteregger, RAG

At a site visit to the RAG-Uniper JV storage facility 7fields, the managing director for Germany’s Uniper Energy Storage, Doug Waters, echoed that exact timelines for conversion are uncertain. “How quickly can hydrogen demand replace methane demand?” he said.

As 7fields consists of seven gas reservoirs connected to a single facility, Waters notes that “we can convert things over time, so we do not need to do the whole [facility] at once”. He anticipates that both 7fields and the nearby Haidach site will “play a key role in providing hydrogen not just for Austria but to southern Germany, particularly the Bavarian chemical industry” owing to proximity.

Uniper is setting up its own hydrogen storage pilot, Hystorage, in Bavaria, with first injection scheduled for this summer. Similarly, it plans to start filling a pilot salt cavern storage project in Krummhorn near Wilhelmshaven with hydrogen late this year and test withdrawals in the spring.

Waters notes that permitting authorities must also adapt rules and regulations, such as those around explosion zones, for hydrogen storage. “All of those things, we had to start again from first principles,” he says.

But even with conversion of existing facilities, “the limitation is available reservoirs”, says Mitteregger, adding that, while the firm has converted 50pc of its reservoirs, “not all will be suitable” to store hydrogen. “Up to 2050, we could have 10bn m³ of storage capacity, but with a third of the energy content,” he says, adding this could mean that, even with best-case additional reservoirs, RAG’s stored energy will likely shrink from 72TWh today to 30TWh by mid-century.

This could have major implications for central Europe’s plans to transition away from fossil fuels while maintaining strong energy security.

“If I look into Germany and Austria, there is a clear plan—especially for Germany—to shut down in the next seven years all the coal-fired power plants… they have already shut down 3GW of nuclear, and that will be substituted by gas-fired power plants,” he says, estimating that 70GW of withdrawal capacity is needed to manage current fluctuations on the grid. He adds that, as Germany increasingly electrifies heating and transportation, 140GW of natural gas withdrawal capacity may be needed.

Given Europe has 500GW of natural gas withdrawal capacity—and converting to hydrogen would shrink this down to 170GW—“the entire European fleet would be needed just to cover the need for Germany”, Mitteregger continues.

Security of supply

“What we are saying is that the European wind and sun production has to be transformed into demand-driven power, heat and industry supply. And it is important to distinguish production from supply,” Mitteregger says.

Current industrial users produce hydrogen on-site from gas on demand, and switching to green—which depends on wind and solar availability—is expected to necessitate storage to maintain consistent flows. Similarly, while imports from multiple routes may enable continuous supply, storage is expected to play a key role in managing the risk of imports being cut off.

“Last year, everybody recognised what it means if security of supply into Europe fails. Then, the importance of storage was really acknowledged and recognised. The same will apply for hydrogen,” Mitteregger adds.

However, reservoirs are not the only way to store energy or hydrogen, and Mitteregger expects wider system changes to handle the mismatch between energy supply and demand. These include storage of hydrogen carriers and derivatives such as ammonia, and the reduction of demand via energy efficiency measures.

“Price signals are also a kind of store of energy,” he says, noting that projections of high winter prices last year resulted in voluntary reduction in consumption.

In Germany, industry reduced its gas consumption by 23pc and private households and businesses by 21pc over the winter compared with a four-year average, although the country’s energy regulator attributes much of this to a significant temperature increase during October and November compared with previous years.

Storing hydrogen versus CCS

Germany and Austria are not pursuing CCS as a route to decarbonise power and industry. However, the German government is expected to review its position in a carbon management strategy due to be published this summer.

“There are also considerations on other gases. Hydrogen is one, but… in future, another might also be CO₂ to be stored in reservoirs,” says RAG CFO Michael Laengle. Hydrogen and CO₂ may compete for underground storage.

“By combining hydrogen and CO₂, one can create chemicals, synthetic gases or synthetic fuels as the case may be,” Laengle adds. “This is at the centre of a carbon-cycle economy that is also CO₂-neutral, and we think this could have big potential for industry in future.”

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Author: Polly Martin