Modular Hydrogen-Driven Electrochemical Systems Integrated with a Proton Exchange Membrane Electrolyzer for Dynamic CO2 Capture in Occupied Enclosed Spaces

Hydrogen-driven electrochemical CO2 capture systems (HECCS) offer a promising technology for direct air capture (DAC). However, the coordinated operation of HECCS with water electrolysis under dynamic conditions poses significant challenges, and the system-level optimization of the integrated system remains unexplored. In this work, a modular hydrogen-driven electrochemical CO2 capture system integrated with a proton exchange membrane (PEM) electrolyzer is proposed for time-varying CO2 capture in enclosed spaces. A multiperiod optimization framework with surrogate models of HECCS modules and the PEM electrolyzer is developed to optimize the design and operation of the integrated system. A case study of DAC for a 600 m3 enclosed space accommodating 50 occupants is exemplified to evaluate techno-economic performances of the integrated system. The results demonstrate that the modular configuration enhances operational flexibility by enabling adjustable module on/off states, series–parallel configurations, and independent regulation of gas flow and current density, allowing the system to maintain high electron efficiency under time-varying demands of CO2 removal. The total cost of the integrated system increases as the allowable CO2 concentration limit decreases, with operational costs dominating the total cost and accounting for about three quarters, whereas the capital expenditure of HECCS shares the smallest portion. For simultaneous CO2 removal and O2 supply in the occupied enclosed space, these findings provide deep insights and optimization guidance for the design of air quality control systems by using the HECCS integrated with PEM electrolysis.