Harnessing Wind with a Passive Direct Air Capture (PDAC) System for CO₂ Capture: Insights from Computational Fluid Dynamics Modeling

Rising atmospheric carbon dioxide (CO₂) levels pose a significant threat to global climate stability, urging the need for effective mitigation strategies. Direct air capture (DAC) offers a promising solution to reduce atmospheric CO₂ levels; however, its extensive energy requirements and high costs hinder widespread deployment. In this study, we develop a computational fluid dynamics (CFD) model to design a passive direct air capture (PDAC) system with an effective wind catcher (a historical architectural element) to passively direct ambient wind into a sorbent-coated monolith, thereby bypassing the need for energy-intensive mechanical fans. The study investigated the influence of wind catcher geometry, monolith structure, and ambient wind velocity on the performance of the PDAC system. Our findings illuminate the complex interplay between geometric parameters of the PDAC system and wind velocity on the monolith velocity, a key determinant of the CO₂ capture efficiency. We highlight that design optimization is not merely about maximizing specific parameters but also striking a balance that considers performance, practicality, and adsorption kinetics. Furthermore, our model reveals the balance between a high monolith velocity and a high surface area for CO₂ adsorption, which is critical in the PDAC system design. Our CFD model was validated with results from a bench-scale experimental setup. This research paves the way for better-informed design and operation of PDAC systems, enhancing the CO₂ capture performance in response to the urgent call to mitigate climate change.