A multiscale engineering design framework for integrated carbon capture and renewable hydrogen systems

This study develops a multiscale engineering-design framework that links OpenFOAM-derived porous-photoreactor transport with reduced-order photoelectrochemical (PEC) hydrogen production, KOH-based carbon processing, State–Task Network (STN) scheduling, Model Predictive Control (MPC), multisite logistics, and techno-economic evaluation, so that reactor-scale transport physics informs infrastructure sizing and investment decisions. CFD simulations quantify transport enhancement, pressure loss, and species accessibility within porous photoreactor geometries, feeding a reduced-order PEC model coupled with a screen-and-refine design-optimisation procedure. Applied to Odense and Kassø using hourly solar-irradiance data, the CFD-informed design produces ∼8,585 t H2/year, €28.90 million/year profit, €444.31 million NPV, and 19.35% IRR. PEC-only is infeasible within investigated bounds, whereas electrolysis-only gives €380.55 million NPV. Neglecting the CFD transport correction raises apparent NPV to €614.53 million and cuts photoreactor area by 33.3%, showing transport fidelity affects both economic valuation and infrastructure sizing. Coordinated Odense–Kassø gives highest NPV, and ±20% solar-resource perturbations remain feasible (NPV €415.1–472.7 million). Transport fidelity, hybridisation, price-responsive dispatch, and spatial coordination affect infrastructure design and economic value, and reactor-scale improvements alone do not guarantee the greatest system-level benefit.