Austria’s RAG has started up the world’s first underground hydrogen storage site at a former natural gas reservoir in Rubensdorf.

RAG plans to store 1.2mn m³ of hydrogen, equivalent to 4.2GWh of power, with the ambition that the pilot will demonstrate how hydrogen can play a role in seasonal energy storage.

Hydrogen for the storage pilot will be produced by a 2MW proton-exchange-membrane electrolyser provided by Cummins. The electrolyser will initially operate off baseload power to fill the reservoir with sufficient hydrogen, with potential to more flexibly operate to store excess renewable electricity on the grid later on in the project’s timeline.

RAG is one of Europe’s largest gas storage operators, with around 6.3bn m³ of capacity and 11 pore storage facilities.

€20mn – Total project cost

Countries not actively pursuing CCS, such as Germany and Austria, are exploring hydrogen as a potential storage solution as part of a shift away from natural gas. However, Germany is also expected to start exploring CCS in the near-term.

Converting power to hydrogen and back has a round trip efficiency of 30–35pc—uncompetitive with batteries for short-term energy storage. However, for seasonal storage, availability and security of supply are likely to trump round-trip efficiency.

RAG anticipates Austria will have a surplus of renewable energy in the summer months, while low solar irradiation and low water flow over winter, combined with additional energy demand, will lead to a shortfall. It cites data from transmission system operator APG that Austria will have a seasonal shift of 10TWh/yr by 2030.

A gas separation unit and an 8km pipeline to RAG facilities in Gampern will be installed by October, with withdrawal to be tested before the end of the year. RAG plans to eventually construct a combined-heat-and-power plant at Gampern, which will be run on hydrogen, in order to decarbonise operations at the natural gas storage site.

Including the pipeline, the Rubensdorf project cost €20mn ($22mn) to develop. RAG CEO Markus Mitteregger tells Hydrogen Economist that the electrolyser unit cost €4–5mn, although he anticipates electrolyser costs will fall to €1mn/MW for future projects.

In addition to having suitable rock, Rubensdorf was chosen owing to the site’s relative isolation.

RAG has previously trialled storing blends of up to 20pc hydrogen in natural gas reservoirs, as well as 100pc hydrogen storage in laboratory tests.

---

Author: Polly Martin