A model for large-scale deployments of CO₂ Direct Air Capture systems

Direct Air Capture (DAC) is an emerging technology for removing carbon dioxide from the atmosphere, by deploying “absorbers” that implement a chemical reaction with ambient air. Recent DAC research has focused primarily on chemistry and heat transfer processes, in order to optimize the performance of individual CO₂ absorbers. However, large DAC arrays will introduce an additional issue: behind the first absorber, subsequent ones must operate with inlet air that has progressively lower CO₂ concentration, thereby increasing their energy requirement for capture and separation. Minimizing this adverse effect requires increasing the spacing between absorbers, leading to increased land requirements and deployment costs. Furthermore, there appear to be no published models for predicting the performance of such large DAC arrays. To address this issue, we introduce a multi-scale model for the aerodynamics of large-scale DAC systems. We obtain an explicit expression for CO₂ capture by a large array, which combines single-absorber design and capture processes with effects of wind speed, atmospheric turbulence, and layout geometry. Our findings provide a quantitative link between atmospheric dynamics and the performance of large-scale DAC deployments.