Underground hydrogen storage in salt caverns: the potential of bedded salt formations

Abstract

Large-scale energy storage solutions are essential to address the intermittent nature of renewable energy sources. Hydrogen is found to be a promising option for energy storage due to its renewable nature. When integrating energy storage systems into the electricity grid, the storage systems need to have a capacity in the MW range, these are considered large-scale storage systems. Hydrogen can provide this storage capacity due to its high energy density, compared to other energy storage mechanisms.

Underground hydrogen storage (UHS) has minimal social and envi- ronmental impacts compared to large-scale surface energy storage. UHS in salt caverns is mostly discussed in domal salt formations, however the use of bedded salt formations is gaining interest as these formations are more com- monly present in certain countries, such as the Netherlands. To this date the only UHS caverns in bedded salt formations are three smaller caverns in Teesside in the United Kingdom. The hydrogen storage potential in other bedded salt formations has not been fully analysed. The Netherlands has an increased need for energy storage due to the various renewable developments in the North Sea. With these projects the Netherlands will play a key role in the transport of the generated energy to other countries, potentially using hydrogen as an energy carrier.

To analyse the storage potential in bedded salt formations, a comprehensive methodology has been employed. Firstly, the technical requirements for a salt cavern storing hydrogen were defined. Secondly, a model is developed to analyse the cyclic injection and extraction (IE) processes of hydrogen in salt caverns, investigating IE rates under various well configurations and IE velocities. It then finds the storage capacity of the cavern based on the working gas volume, and plots the loading profile of each cavern. The final section of the research creates an interactive map which displays the storage capacity of a single cavern in various locations in the Netherlands, which have been chosen in this research based on the presence of bedded salts in the area.

The main cavern requirements are based on the salt formation depth and thickness. The pressure range is found to be 30-80% of the overburden pressure. The injection and extraction rates are only found to reach the maximum rate of 1 MPa/day when using a second well. The modelled cavern was found to have a storage capacity of 14.66 GWh. According to a residual load profile the potential for variable loading was analysed, and the modelled cavern was found to be too small to match the residual load of the Netherlands in 2030.

In conclusion, bedded salt formations offer significant potential for UHS. The Netherlands contains many suitable locations for UHS in bedded salt formations, with the size of the caverns differing significantly throughout the country. The suitable salt formations are located mostly in the East and North of the Netherlands. Further research is required to explore the integration of specific caverns into local or national energy systems, and the costs associated with this storage technique.