Hydrogen has a relevant position in the national strategy to facilitate the achievement of environmental objectives and to guarantee a safer and more reliable energy production, in presence of an increasing generation from renewable sources. These energy sources, characterized by a marked discontinuity, can lead to significant problems in the management of the electric grid due to the unpredictable imbalances between production and demand. Therefore, the conversion of the electric overgeneration produced from renewable sources into hydrogen, which can be stored for long periods and used on site or injected in the gas network, would ensure greater stability to the electric grid by decoupling, in space and time, the production from the final use.

From this point of view, hydrogen storage in salt caverns, depleted hydrocarbon fields and aquifers is an attractive option to ensure large energy amount over the time. However, the use of the subsoil for energy storage can introduce risks that can have a negative impact on health, environment, economy as well as on the public acceptability of the technology. While the risks associated with the underground storage of natural gas are known for decades, those related to the hydrogen storage are relatively unexplored mainly due to the specific chemical-physical properties of this gas such as wide flammability ranges, high diffusivity in materials, low minimum ignition energy.

The aim of this document is to analyze the main safety issues related to the underground hydrogen storage, with the view that a greater knowledge of the hydrogen safety can improve public awareness and confidence in the use of this technology. In particular, the report considers the impact of hydrogen on the integrity and durability of materials, leakages from the subsoil and wells, diffusion, dissolution, and contamination of hydrogen in the reservoir, subsidence, and induced seismicity.

Finally, the report includes some considerations on the methodological approach to be used for the risk analysis of surface infrastructures deduced from the experience gained in the operation of natural gas storage plants.

The document is available on the site in Italian