Integrating Thermodynamic Modelling in the Optimization of Salt Caverns Storage for Dedicated Offshore Wind Farms

Abstract

The demand for hydrogen is expected to increase significantly in the coming years due to its critical role in decarbonizing industrial processes. Offshore wind presents a viable energy source for powering electrolyzers, though it leads to intermittent production. While underground salt caverns are acknowledged as a promising solution for large-scale hydrogen storage, the technology still faces challenges regarding integration with fluctuating renewable energy sources.

This research, conducted in collaboration with Vattenfall, introduces a framework for modeling hydrogen storage in salt caverns, linked to hydrogen production from offshore wind farms. The framework features a technical model that addresses the thermodynamic changes within the cavern during hydrogen injection and withdrawal.

This new framework was expanded with an economic model and used to evaluate the optimal configuration for a standalone green hydrogen production and storage system. The analysis demonstrates that, up to a high security of supply threshold, increasing the storage capacity is the most effective strategy. Beyond this threshold, optimizing the configuration by increasing the number of stack changes or slightly enhancing the overall production capacity proves more beneficial than merely expanding storage. Additionally, the study explores two case study variations to assess the impacts of integrating flexible demand and line packing into the system.

The study concludes that the thermodynamic modeling of caverns significantly improves the accuracy of storage capacity estimations. It also highlights that optimal system design extends beyond adjusting storage capacity, necessitating comprehensive component optimization to strike a cost-effective balance for required supply securities. Furthermore, integrating demand flexibility enhances security of supply, enabling systems with high flexibility to achieve 100% security of supply with smaller storage capacities. However, the inclusion of line-packing does not improve economic performance. The insights underscore the need for strategic system design in hydrogen production and storage systems.