Achieving reduced emission and enhanced air quality by designing a solar-driven indoor CO₂ capture system

Green buildings desire low CO₂ emission and high indoor air quality (IAQ), which, however, are inherently conflicted on energy consumption and cannot be achieved simultaneously in air conditioning-based ventilation methods. One alternative can be combining building-integrated renewable energy and CO₂ capture technology to remove CO₂ from stale indoor air and return CO₂-depleted air to save air conditioning's (AC) energy demands. Despite the great potential, developing such a system remains challenging owing to the complex mass-energy exchange between the two subsystems, which has been oversimplified in previous research. This study for the first time developed an integrated solar-driven indoor air CO₂ capture system and unveiled the dynamic mass-energy balance while considering selective air recirculation. Specifically, multi-variate analyses are conducted to evaluate the proposed system's overall performance, characterized by CO₂ capture capacity, air quality enhancement and energy-saving potential. A scenario analysis covering different crowdedness and room areas is also conducted to obtain optimal design configurations for practical implementations. Results show that for one example case of a 40 m² room with 39 occupants, the proposed system with optimal configuration captures 40.655 kg CO₂ per day, controls the indoor CO₂ concentration below 800 ppm and saves 24.082 kWh (38.18%) cooling energy by selectively recirculating clean post-captured air. This study sheds light on the rational design of a renewable hybrid system for enhanced indoor air quality, CO₂ emission reduction, and energy saving, all of which are preferred in establishing a smart, sustainable and comfortable city.