A novel techno–economic methodology for optimal sizing and configuration of electrolyzers in solar-powered hydrogen systems

The global transition toward sustainable energy systems requires efficient Power-to-Hydrogen (P2H) solutions for converting variable solar energy into clean hydrogen. Among available technologies, proton exchange membrane (PEM) and solid oxide electrolysis cell (SOEC) systems offer promising pathways for solar-to-hydrogen conversion; however, the intermittent and midday-peaking nature of solar generation poses major operational and planning challenges. This study develops a novel unified techno–economic optimization framework for determining the optimal size, number, and configuration of electrolyzers in solar-powered hydrogen systems, including both single-technology and hybrid electrolyzer designs. Four configurations are analyzed — PEM, PEM + BESS, SOEC + BESS, and hybrid PEM–SOEC + BESS — to evaluate the techno–economic trade-offs between flexibility, efficiency, and cost. A mixed-integer linear programming (MILP) model is developed based on an inverse unit commitment (IUC) framework to optimize both electrolyzer and battery energy storage capacities while considering operational characteristics, including startup/shutdown transitions, ramp-rate limits, degradation, and variable efficiency. The model is further extended to a two-stage stochastic programming formulation to address uncertainty and enable risk-aware decision-making by considering both risk-neutral and risk-averse strategies through a Conditional Value-at-Risk (CVaR) metric. Results show that integrating energy storage improves solar utilization from 89.79% to 91.75% and increases the annual profit by 3.93% for the PEM configuration, while the hybrid PEM–SOEC + BESS system achieves 87.92% utilization and 10.3% higher profit compared to PEM + BESS. Stochastic analysis indicates that uncertainty leads to a 7%–12% reduction in profitability, whereas risk-averse planning enhances system robustness under fluctuating solar conditions. The proposed framework provides a robust foundation for the techno–economic planning of solar-powered hydrogen production systems and highlights the advantages of each system configuration.