Carbon dioxide capture from air in buildings – Design and techno-economic feasibility of practical systems

Direct Air Capture (DAC) is needed alongside other CO 2 removal methods to ensure that the total amount of CO 2 required is removed from the atmosphere so that global warming can be limited to below 2 °. While large-scale DAC farms are a promising solution, their high CAPEX and OPEX, along with societal concerns, may hinder widespread deployment. This study presents a novel, modular DAC concept designed for integration into heating, ventilation, and air conditioning (HVAC) systems of buildings. A prototype was engineered and modeled in MATLAB to analyze key physical processes in the adsorber bed using two amine-based adsorbents. A linear driving force model was applied to simulate mass transport, and the DAC unit was coupled with an HVAC system in Simulink to evaluate CO₂ capture from indoor air. Solar thermal energy with thermal storage was defined as the heat source. Optimization results indicate a 40 % reduction in thermal energy demand compared to separate DAC and HVAC systems. Cold, humid air improves CO₂ capture, while dry air significantly lowers the energy demand – up to 50 % when reducing humidity from 90 % to 10 %. A techno-economic analysis suggests that mass-produced DAC modules for HVAC systems could achieve levelized costs of DAC as low as 280 € per ton CO 2 , particularly when waste heat is utilized. Implementation in densely occupied buildings may yield additional savings of up to 9 %. This work highlights the potential of HVAC-integrated DAC systems as a scalable, cost-effective complement to centralized DAC facilities. • Systematic assessment of the integration of DAC into existing ventilation infrastructure. • In depth modelling of building integrated DAC with dynamic input parameters. • Results show that building type and operation strategy do substantially influence energy demand. • Techno-economic analysis revealed levelized cost of DAC as low as 280 EUR per ton of CO 2 captured.