GIS–MCDA Approach for Underground Hydrogen Storage Site Screening in Deep Saline Aquifers: Geological, Renewable Energy, and Infrastructure Criteria

Large-scale underground hydrogen storage (UHS) in saline aquifers requires preliminary screening methods that consider both subsurface suitability and the spatial context of the energy system. This study develops an integrated geographic information system with multi-criteria decision analysis (GIS–MCDA) framework for the regional assessment of candidate UHS sites under conditions of limited data availability. Eleven geological and operational criteria were grouped into reservoir quality (RQ), seal integrity (SI), and operational conditions (OC) and weighted using the Best–Worst Method (BWM), resulting in component weights of 0.520, 0.296, and 0.184, respectively. The normalised criteria were aggregated into a Geological Hydrogen Suitability Index (GHSI), which was subsequently combined with the spatial distribution of installed renewable energy (RE) capacity and proximity to high-voltage power infrastructure (DI) to derive a Total Suitability Index (TSI). Three weighting scenarios representing geological, balanced, and energy–infrastructure priorities were analysed. The framework was applied to five candidate structures in north-western Poland: structure S4 achieved the highest GHSI (0.757), followed by structure S1 (0.699); structures S2 and S5 obtained very similar intermediate values (0.579 and 0.578, respectively); and structure S3 received the lowest score (0.505). The contrasting component profiles demonstrate that high performance in a single criterion group does not necessarily result in high overall geological suitability. The scenario analysis also showed that increasing the weights of the components relating to installed renewable energy (RE) capacity and distance from power transmission infrastructure (DI) can significantly alter the assessment, which is based primarily on geological suitability; these changes are particularly pronounced in the case of structures S4 and S5. The proposed framework provides a transparent spatial decision-support approach for preliminary regional UHS screening. Its results should be interpreted as relative suitability assessments rather than direct estimates of storage safety, capacity, injectivity, or commercial feasibility.