Flexible off-grid renewable power-to-methanol system: Techno-economic optimization

Renewable methanol production a promising pathway for industrial decarbonization, yet off-grid Power-to-Methanol (PTM) deployment is limited by the intermittency of wind and solar resources. With the aim to optimally configure an off-grid PTM system balancing efficiency, cost, and renewable utilization, we propose a flexible off-grid PTM process that integrates H₂O/CO₂ co-electrolysis and CO₂ energy storage, with a focus on the process intensification and flexibility operation. We employ a two-stage optimal dispatch model to determine optimal system capacities and conduct techno-economic assessment. Results show that the optimized system achieves 95.5 % renewable penetration, 62.0 % energy efficiency, a minimum levelized cost of methanol of $902.3/t, and a negative carbon intensity of −0.90 t CO₂ t −1 MeOH. Flexible operation extends annual operating hours of the solid oxide electrolysis cell and methanol synthesis unit to 8730 h and 8345 h, respectively. Sensitivity analysis identifies the solid oxide electrolysis cells as critical cost drivers. This work provides a technical solution for the efficient use of renewable energy in remote regions and presents a conceptual techno-economic design study based on modeling and simulation. These findings demonstrate that process flexibility and energy storage enable economically competitive, carbon-negative methanol production, advancing the role of PTM in industrial decarbonization. • An off-grid PTM system integrating SOEC co-electrolysis and CCES is proposed. • Renewable energy utilization reaches 95.54 % and overall efficiency reaches 62.03 %. • Negative carbon emissions of −0.90 t CO₂/t MeOH is achieved. • Optimized system achieves a levelized cost of methanol (LCOM) of 902.30 $/t. • The cost and lifetime of the SOEC are the key factors on economic viability.