Optimisation of off-grid energy systems with hydrogen and battery options

This study investigates optimal sizing of the components of a hybrid power plant that integrates variable renewable energy sources with two backup storage technologies: battery and hydrogen energy systems, the latter comprising electrolyser, hydrogen storage and fuel cell units. The model incorporates multiple objectives — economic, technical, and environmental — allowing for flexible prioritisation depending on project-specific goals. The objectives are represented, respectively, by total present cost, loss of power supply probability, and lifecycle emissions. A key contribution of this work lies in the comprehensive assessment of how system constraints, objective prioritisation, and location-specific factors influence the optimal design. The results show that, under base-case assumptions, hydrogen energy system offers a more cost-effective and operationally flexible solution for time-shifting excess renewable energy compared to battery-only configurations. This is primarily due to the separation of energy conversion (in the electrolyser and fuel cell) and hydrogen storage within the hydrogen energy sub-systems, although long-duration battery technologies were also part of the optimal solution under certain scenarios. Overall, the optimal sizing solution is highly sensitive to the choice of objective weights, component configurations and topology, level of reliability required, and the temporal characteristics of renewable energy resources at a given location. For example, relaxing reliability constraints significantly reduces cost, while integrating wind and solar resources can reduce reliance on dual storage systems. The findings underscore the importance of using a multi-objective, constraint-aware, and context-sensitive approach for designing sustainable and reliable renewable energy systems.