Design and operation optimization of a solar-driven methanol-to-X system with an absorption energy synergy module under multi-scenario applications

Methanol-to-X (MtX) systems based on proton exchange membrane fuel cell (PEMFC) stacks are widely recognized as a promising solution for small- to medium-scale multi-energy supply, while solar-assisted operation offers further potential for reducing carbon emissions and operating costs. However, intra-day and seasonal fluctuations in solar availability and user energy demand often force such systems to operate under off-design conditions for extended periods, leading to performance degradation. To address these challenges, this study proposes a solar-driven MtX (AESM-SMtX) system integrated with an absorption energy synergy module, enabling coordinated utilization of solar energy and PEMFC waste heat to enhance supply-demand matching. Furthermore, to overcome suboptimal performance arising from the decoupled treatment of structural design and operation optimization, a design-operation co-optimization strategy is developed. Multi-scenario application analyses are conducted across representative Chinese regions with diverse climatic conditions and energy market environments. Results indicate that the AESM-SMtX system achieves up to a 27.76% improvement in energy efficiency, a maximum increase of 152.60% in quarterly total revenue, and a reduction of up to 28.55% in mass specific emissions compared with the methanol-fueled MtX (AESM-MtX) system integrated with an absorption energy synergy module. Strong economic feasibility is demonstrated in Hong Kong and Shanghai, with a minimum payback period of 10 years in the school scenario.