Evaluation of the humidity performance of a carbon dioxide (CO₂) capture device as a novel ventilation strategy in buildings

This study examines the moisture performance of a carbon dioxide (CO₂) adsorption device and its utilization as a novel ventilation strategy in buildings. The device adsorbs CO₂ and a small amount of moisture in the CO₂ capture process. To activate a CO₂ capture device for air recirculation in a building or connect it to an air handling unit to minimize the ventilation rate, the air needs to be controlled to have a steady-state humidity ratio below 12 g/kg, which is the maximum humidity ratio allowed in a room according to international standards. This study exhibits the moisture performance of an implemented CO₂ capture device in the operation of an air ventilation system and its ability to recirculate indoor air via experimentation and numerical modeling for saving energy in buildings. Moreover, this research also evaluates the humidity performance using the strategy of connecting the CO₂ capture device with an air handling unit and recirculating the air in the breathing zone based on an occupancy diversity factor. Based on these results, the study indicates that the air recirculation achieved by either using the CO₂ capturing unit itself or connecting it to an air handling unit reduces not only the thermal energy load but also the energy load of dehumidifying the air in buildings. This work newly introduces the humidity performance of a CO₂ capture device for air ventilation in buildings, and the novel ventilation paradigm can adjust the supply outdoor airflow rates depending on the surrounding environment and occupant behavior.