Modelling green hydrogen storage in salt caverns: Implications of future storage demands on cavern operation

Abstract

The transition to a renewable energy system based mainly on an electricity and hydrogen infrastructure places new requirements and constraints on the infrastructure systems involved. This study investigates the impact of future hydrogen storage demands on a representative salt cavern, considering two cases: a regional focus on Lower Saxony with high wind energy penetration, and a national perspective on Germany with a PV-dominated mix of installed capacities. A numerical model is developed for in-depth assessment of the thermodynamics inside the cavern. Hydrogen storage profiles, generated from 2045 renewable electricity projections for Germany, reveal substantial storage demands. Key parameters, such as hydrogen production and storage share, turnover rate, and storage interval length, vary significantly between the two cases. In the Lower Saxony case, high wind shares lead to increased turnover rates and reduced required working gas volumes, but also result in steeper pressure and temperature gradients inside the cavern and necessitate larger compressor systems. In contrast, the PV-dominated Germany case experiences lower internal cavern stresses but requires more flexible surface components to manage frequent fluctuations in hydrogen flow. These findings underscore the complex interplay between regional power mixes, storage facility design, and operational requirements.