A novel solar photothermal/radiative cooling-thermal catalytic (PT/RC-TC) hybrid system for improving indoor environment by a broadband absorber/emitter with thermal catalysts

Abstract

Creating a comfortable indoor environment, which includes appropriate temperature control and effective pollutant removal, requires a significant amount of energy consumption from air conditioning systems. Harvesting energy from the sun and the universe for building heating and cooling has attracted much attention due to its clean utilization. Herein, a novel solar photothermal/radiative cooling-thermal catalytic (PT/RC-TC) hybrid system for indoor heating, cooling and air purification by a broadband absorber/emitter with back-coated thermal catalysts $\alpha$-MnO₂ was proposed and designed. The hybrid system provides cooling in summer and space heating in winter, offering temperature regulation during transitional seasons and air purification in whole year. We established and validated a numerical model for the PT/RC-TC hybrid system. Based on this model, we investigated the heating performance, radiative cooling performance, and formaldehyde degradation efficiency of the system during different seasons and different cities. The main results are as follows: The absorber/emitter has an average absorptivity of 0.94 in the solar radiation band and an average emissivity of 0.90 in the atmospheric window band. Simulation results show that without air conditioning, the maximum daily cooling gain of the system in summer was 233.7 Wh/m², with a clean air production of 86.4 m³/m²; and the maximum daily heat gain in winter was 172.9 Wh/m², with a clean air production of 29.5 m³/m². And with air conditioning, the maximum daily cooling gain in summer was 107.2 Wh/m², with a clean air production of 82.3 m³/m²; and the maximum daily heat gain in winter was 49.4 Wh/m², with a clean air production of 17.5 m³/m². Annual performance analysis indicates that the system is adaptable and practical under different climatic conditions (Beijing, Nanjing, Guangzhou, and Xining), efficiently meeting the heating and cooling needs of buildings, significantly improving indoor air quality, and reducing energy consumption.