Heat pump assisted direct air capture system for carbon enrichment in plant factory

This study proposes a direct air capture (DAC)-integrated carbon enrichment strategy for plant factories with artificial lighting (PFALs), where continuous CO2 supplementation is required for stable photosynthetic growth. The performance of amine-impregnated resin (RP-50) was evaluated under low-concentration CO2 adsorption and moderate-temperature regeneration conditions. The adsorption-desorption behavior was experimentally characterized using an Avrami-based kinetic model, enabling prediction of regeneration time under both fully and partially saturated conditions. The regeneration energy requirements were quantified for different desorption gas compositions, highlighting the coupled influence of temperature and equilibrium driving force on desorption kinetics. These experimentally derived kinetics were then incorporated into a DAC-heat pump module model to analyze operational performance in PFAL environments. System-level parametric analyses demonstrated that regeneration temperature is the dominant factor governing sorbent demand, system sizing, and indoor CO2 stability. High-temperature regeneration enabled rapid desorption performance, whereas lower-temperature operation reduced thermal energy input. During the carbon enrichment process, contact between the circulating air and the heated sorbent reactor elevates the air temperature, generating an additional cooling load as a side effect. Nevertheless, under waste heat-assisted heat pump operation, the system maintained competitive specific energy consumption (SEC) values within 2.96-4.89 GJ tonCO2−1. Overall, this approach provides an effective utilization pathway for CO2 captured by DAC systems that traditionally require additional storage or conversion processes, without imposing extra energy penalties for compression, storage, or conversion.