Desclaimer: This article is not directly connected to mobility, however, mobility on alternative fuels is directly connected to energy production, distribution and storage. The following article represents the production and storage solution for hydrogen.
On Wednesday, December 11th 2024, a Store More (Interreg Danube programme) project partner Elektro Gorenjska JSC, Ambrož Bogataj and partner BSC, Ltd, Kranj – Regional Development Agency of Gorenjska, Blanka Odlazek attended a study visit to see the underground hydrogen storage system, Underground Sun Storage 2030, in Rubensdorf, Austria.
The site used to be a natural gas storage and it has been converted into the hydrogen storage. The capacity of the storage is 1,2 mio Nm3. The electric energy, which is produced from renewable energy sources, solar, wind is used for production of hydrogen with 2 MWe proton permeable polymer membrane (PEM) electrolyser. The output of electrolyser is 400 m3 per hour, transfer pressure is 30 bar, efficiency of electricity to hydrogen for the whole plant including auxiliary equipment is 72%. The hydrogen is then compressed and pushed down 1 km into the ground, where it is stored. During the storage it blends with natural methane. Initial reservoir pressure is 107 bar. Porosity of sandstone is 16-25%. In the winter months when gas is needed for heating and industrial applications, the blend is pumped from the ground into the purification chamber, where hydrogen and methane are separated (Pressure swing adsorption, Membrane gas permeation and Catalytic desulfurization). The methane residue from the purification process is emitted into the air. When hydrogen is purified, 2% of hydrogen is blended with compressed natural gas and distributed to the consumers via gas lines.
The project „Underground Sun Storage” as well as the further research project “Underground Sun Conversion” receive funding from Austrian Climate and Energy Fund established by the Ministry for Transport, Innovation and Technology, as part of its energy research program.
It has to be noted that according to the Interstate Natural Gas Association of America, a 20% hydrogen blend reduces the energy content of natural gas by nearly 14%, compared to 100% natural gas. This means that the 2% of hydrogen blended into the natural gas reduces the energy content by 1,4%. The White paper Restoring Energy Capacity of Natural Gas Following Hydrogen Blending by Ameerudeen Najumudeen, PE, P.Eng in 2024, states that a University Alberta study published in 2023 found that burning a blend of 15-20% hydrogen in natural gas by volume can cut carbon emissions as much as 5%, compared by burning natural gas alone. This means that in a blend of 2% hydrogen in natural gas by volume reduces carbon emissions as much as 0,5%. According to APEG – Associação Portuguesa de Empresas de Gás hydrogen has a volumetric Gross/Net Calorific Value (GCV/NCV) roughly 1/3 of the one of natural gas. For this reason, any volumetric unit of hydrogen/natural gas blend will have a minor energy content than the same volume of pure natural gas.
The project is from the technical point of view interesting and looks promising. The question that remains open is how economical this whole process is (CAPEX, OPEX, payback time…).
You can find more information about the project „Underground Sun Storage” on https://www.uss-2030.at/das-projekt/kurzbeschreibung.html.
