Hydrogen-centric multi-energy systems for high-renewables grids: Technologies, flexibility services, and deployment pathways - A critical review

The escalating integration of variable renewable energy (VRE) necessitates the development of energy systems that can furnish flexibility across a spectrum of temporal scales, ranging from mere seconds to entire seasons, in alignment with Sustainable Development Goals (SDGs) 7, 9, and 13. Hydrogen-centric multi-energy systems (H-MES) fulfill this requirement by facilitating the transformation of surplus renewable electricity into hydrogen, thus enabling long-duration energy storage, followed by its reconversion into electricity, thermal energy, and mobility fuels, all while enhancing grid reliability. This review offers a systematically structured and decision-oriented evaluation of H-MES across four pivotal domains: grid-responsive electrolysis, hydrogen storage technologies, reconversion pathways, and the integration of systems with market participation. The assessment of performance is standardized through the utilization of grid-relevant metrics, thereby facilitating a consistent evaluation of both flexibility and adequacy. A cohesive techno-economic and life-cycle framework is employed that accounts for parasitic losses and the utilization of by-products. Decision-oriented indicators, including Effective Load Carrying Capability (ELCC), Loss of Load Expectation (LOLE), curtailment absorption, and ₹/MWh-shifted, are introduced to enhance transparency in planning, investment analysis, and the scalable deployment of hydrogen-based energy systems. • Normalized framework links electrolyzer, storage, and reconversion dynamics. • Decision-ready KPIs connect technology, market design, and reliability metrics. • Temporal LCA aligns hydrogen system operations with dispatch and emissions. • Archetype-based synthesis enables bankable hydrogen deployment pathways. • Unified model bridges flexibility, adequacy, and sustainability in high-VRE grids.