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

Abstract

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.