Multi-Objective Optimization of Stand-alone Cost-effective Renewable Energy Systems: the Role of Storage Technologies in Curtailment and Cost Minimization

The urgent need to reduce global CO₂ emissions demands an accelerated transition to renewable energy systems. In this context, stand-alone renewable systems in remote areas are increasingly relevant, as such systems often rely on diesel generators that contribute to high CO₂ emissions and operating costs. This study investigates the design of a fully renewable energy system for a Mediterranean island, relying on both photovoltaic and wind energy. To achieve this, a multi-objective optimization framework is developed, targeting the minimization of the Levelized Cost of Electricity (LCOE) and renewable energy curtailment. The intermittency of renewable energy sources necessitates the use of storage systems. This study evaluates three energy storage configurations: battery storage, hydrogen storage, and a hybrid solution combining the two technologies. The hydrogen storage system includes an electrolyzer to convert excess electricity into hydrogen, a compressor and tank for storing hydrogen at the desired pressure, and a fuel cell to generate electricity when needed. The results demonstrate the shortcomings of both storage systems when employed independently. Consequently, the hybrid solution, which combines the high efficiency of batteries in short-term storage with the long-term reliability of hydrogen systems, represents the optimal selection. However, the analysis also highlights a trade-off between minimizing LCOE and renewable energy curtailment due to the high cost of storage systems. Increasing production capacity, while accepting a degree of curtailment, is currently more cost-effective. A key focus of the study is identifying threshold storage system costs at which the LCOE and curtailment cease to be conflicting objectives. This price gap serves as a critical indicator of the need for cost reductions in storage technologies to ensure economic sustainability and efficient utilization of renewable energy sources. By providing a comprehensive assessment of the interdependence between economic and technical factors across diverse storage systems, this study offers valuable insights into the design and optimization of stand-alone renewable energy systems for remote areas.