(289f) A Passive Wind Collector Integrated with a Direct Air Capture (DAC) System for Efficient, Sustainable, and Scalable CO2 capture

One of the major challenges facing our current COâ‚‚ mitigation technologies is the scale-up of direct air capture (DAC) systems at the large scale to meet the desired target goal of <$100/tonne CO₂ removed. Conventional DAC systems rely on fans to drive the ambient air through a COâ‚‚ adsorption system to produce air with lean COâ‚‚ levels. It is imperative to passively collect and drive wind to reduce a continuous operating cost (i.e. fan) required to introduce air flow to DAC system while providing good mass transfer for subsequent CO₂ capture in the system. Here we introduce a wind collector that can passively collect winds from all directions and drives it into a CO₂ adsorption system containing sorbent coated monolithic structure with open cells while still maintaining low pressure drop across the adsorption unit to ensure high operational throughput.

Even though the concept is simple, the overall efficiency of COâ‚‚ adsorption in such a passive DAC system depend on the intricate and coupled effects of (i) available wind velocities (ii) pressure and velocity distribution throughout the DAC system and (iii) mass transfer and adsorption characteristics of the sorbent coated monolith. To resolve this complex interplay, we developed a comprehensive computational fluid dynamics (CFD) model to analyze the effect of critical geometric parameters of the wind collector (opening width (R), height of side opening (H), and opening angle (θ)) and the monolith structure (pitch size (P), Length (L)) on the transport of air through the open monolith cells. Depending on the pressure drop generated inside the passive DAC system (due to internal flow resistance imposed by the monolith), a range of expected internal air velocities at different wind speeds can be achieved. Results from the CFD model provide us with valuable insights into the dependence of system’s geometric parameters on the COâ‚‚ capture efficiencies and location specific optimal design parameters based on the locally available wind velocities. As there are no moving parts in this design, the maintenance requirement is very low. The high throughput removal of CO₂ from ambient air in a system that offers a small footprint, scalability, and off grid operation (no electricity required) has the potential for widespread implementation, enabling us to address the COâ‚‚ mitigation needs at large scales.