Techno-economic assessment and multi-objective optimization of a hybrid methanol-reforming proton exchange membrane fuel cell system with cascading energy utilization

This article proposes an innovative tri-generation system aimed at improving the efficiency of proton exchange membrane fuel cell (PEMFC) combined methanol steam reforming (MSR) setups. The proposed system merges MSR-PEMFC with an organic Rankine cycle (ORC) and Latent-thermal energy storage (LTES) to produce heat, electricity, and purified water concurrently. The MSR process, using methanol and water, acts as a hydrogen source for the PEMFC. Waste heat from the reforming reaction and PEMFC exhaust gases is efficiently recuperated through ORC and LTES. Moreover, a composite phase change material comprising 8 % expanded graphite and 92% industrial paraffin wax is formulated for LTES, exhibiting a thermal conductivity of 4.65 Wm(-1)K(-1). Parametric analysis of the methanol-reforming fuel cell system suggests a methanol to water mass ratio of 1.5 and a pressure swing absorption shunt fraction of 0.77. Multi-objective optimization of the recovery system using the Non-dominated Sorting Genetic Algorithm II algorithm is conducted, with objective functions including tri-generation system exergy efficiency, CO2 emission reduction, and total cost to evaluate system thermodynamic, environmental, and economic performance, respectively. The ORC system employing R245fa and R600 yields 27 % more electricity than the R152a-based system, with exergy efficiencies approximately twice as high. Compared to conventional systems, the proposed tri-generation system achieves an energy efficiency of 81 % and exhibits a 22 % enhancement in energy efficiency.