The European Network of Transmission System Operators for Electricity (Entsoe) expects hydrogen to be critical in providing long-duration storage to fully decarbonised power systems.

"Hydrogen and its derivatives are the most interesting candidates” for seasonal storage, said Antonio Iliceto of Italian TSO Terna, who also convenes Entsoe’s working group on the future of energy systems, at a recent webinar.

There are many means available to power grid operators for short- and medium-duration flexibility, but very few that offer durations of a month or longer, Iliceto says.

Some of the larger pumped storage hydropower plants can offer seasonal storage, but their potential is limited by geography. Thermal storage technologies could potentially offer months of long-term storage, he says, but they are still in the development stage.

Another advantage of hydrogen is that molecules can be stored for a long time with few losses, Iliceto adds. Hydrogen can also utilise existing gas storage and transport infrastructure, which will prevent them from becoming stranded assets.

67GW – Projected German dispatchable power plant capacity by 2030

Converting power to hydrogen and back into power has a round trip efficiency of around 30–35pc, making it uncompetitive against batteries for intraday power storage, says Grzegorz Pawelec, director of intelligence at lobby group Hydrogen Europe. “But when you go to seasonal storage that efficiency loss has less importance versus the fact that there are just not that many alternatives for long-term high-capacity storage,” he adds.

A huge amount of hydrogen storage may also be necessary to balance variable supply of green hydrogen with stable demand from industrial hydrogen users. A good rule of thumb is that storage volumes equivalent to 10pc of the annual hydrogen demand may be required if the electrolyser is not connected to the power grid, Pawelec says.

An average steel plant consuming 200,000t/yr of hydrogen would require storage of 20,000t—equivalent to around 600GWh. “That could translate to a huge potential that can be used when there is a ‘dunkelflaute’—when you have two or three weeks of reduced renewable energy production,” he notes, adding this hydrogen can also be used as fuel for dispatchable power.

But one issue will be how to remunerate providers of long-duration storage. “Seasonal reserve is fundamental but who pays for it?” Iliceto says. “System needs like seasonal storage are not market products, so they have to be centrally regulated and properly remunerated.”

Iliceto suggests there may be strategic reserves in future for hydrogen “like we have today for oil and gas”, although these would need to be set by a central public authority.

German needs

Hydrogen will be a particularly important source of seasonal storage in countries where fossil fuels with CCS or nuclear power are not politically accepted, says Joerg Kerlen, senior manager of public affairs at RWE.

For example, dispatchable power plant capacity in Germany would fall to 67GW by 2030—down from 110GW in 2018—if no new plants were built and the country were to continue  current coal phaseout plans.

Germany’s energy regulator estimates 17–21GW of newbuild dispatchable capacity will be required by 2031. And this is already based on optimistic assumptions of other supplies, Kerlen argues, such as 38GW available from other countries in an environment where dispatchable capacity in neighbouring countries is also falling. It also assumes more than 30GW of demand-side response and storage.

This 17–21GW of dispatchable capacity will mostly be gas-fired power plants. These plants will be required to be hydrogen-ready and will need to switch to hydrogen as soon as sufficient amounts are available, Kerlen says.

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Author: Killian Staines