Abstract
The increasing need for Direct Air Capture (DAC) technologies is driven by the urgent global need to mitigate rising CO2 levels due to climate change. In humid climates, DAC systems face challenges as high humidity increases the energy required for regeneration. This study introduces a novel DAC system integrated within an Air Handling Unit (AHU) that includes a silica gel wheel for air dehumidification before CO2 capture, significantly enhancing physisorbent performance by optimizing conditions for CO2 adsorption. This system, tailored for the AHU of Doha Tower, involves dehumidifying return air, subsequently cooling it for effective CO2 capture. The introduction of the silica gel wheel notably reduced the energy requirements by 81.5% for NbOFFIVE compared to configurations without dehumidification, and the thermal energy cost for NbOFFIVE when integrated with HVAC and silica gel is 70 USD/ tonCO2, compared to 160 USD/ tonCO2 for SBA-15 + TEPA used alone. Additionally, the thermal energy cost for the HVAC system was reduced from 430 USD/tonCO2 to 303 USD/ tonCO2. A technoeconomic analysis highlights these improvements as crucial for reducing operational costs and cutting capital expenditures by leveraging existing AHU infrastructure. Despite the higher initial cost of NbOFFIVE, the levelized cost for DAC using NbOFFIVE is estimated at 184 USD per ton of CO2, making it economically advantageous compared to 208 USD per ton for SBA-15.