Designing CO2 reduction microreactor systems under fluctuating renewable H2 supply by multi-objective stochastic optimization

Reverse water-gas shift (RWGS) microreactor systems offer the flexibility to efficiently utilize CO2 and renewable H2 for syngas production. However, the inherent fluctuation in the green H2 supply presents a substantial obstacle for cost-effective production, particularly at larger scales. In this work, the design and operation of RWGS microreactor systems with fluctuating H2 feed are addressed by multi-objective stochastic optimization. The optimization objectives are the reaction performance, the annual total cost, and the carbon footprint of the microreactor system, while the decision variables include the channel geometry, channel topology, and inter-stack flow controller configuration. The results demonstrate that a well-designed hierarchical microreactor system achieves excellent reaction performance even without inter-stack flow controllers under both deterministic and uncertain conditions. Small plate-level distribution channels and moderate-sized higher-level distribution channels allow good and stable reaction performance. To balance all the design objectives, it is suggested to first increase the number of stacks at smaller production scales and then increase the number of substrates within each stack at larger production scales. Our study provides new design insights for distributed production using modular devices under high penetration of renewable energy.