Study and Development of Novel and Next-Generation Self-Cooling Building Materials using Daytime Passive Radiative Cooling Technology

Buildings consume substantial energy for air-conditioning (AC), particularly in Hong Kong, a subtropical region with a hot and humid climate. Passive radiative cooling, an innovative cooling technology that is energy-free and refrigerant-free (green), is able to cool buildings for AC energy-saving. This project aims to promote and commercialize novel daytime passive radiative cooling (DPRC) building materials, including colored thermochromic DPRC paints and ceramic tiles for roofs and walls, and transparent DPRC paints/films for windows and solar cells. A colored thermochromic DPRC paint and ceramic tile will be developed, which can strongly reflect solar irradiance and effectively emit thermal radiation to the cold universe for cooling in summer, meanwhile absorbing solar energy in winter for heating. Besides, a transparent DPRC paint/film, that can cool windows and solar cells by emitting the thermal radiation to outer space, will also be developed. Note that lowering the operating temperature of solar cells enhances their efficiency. It is predicted that energy-saving of buildings adopting these materials can achieve >20% with a payback period < 2 years, meanwhile the efficiency of the solar cells can be further improved by >5% without additional retrofit work or energy input. Overall, the novel and next-generation DPRC building materials will bring a substantial impact in construction, property management and renewable energy industries, benefiting the premises owners, occupants and public at large. It is believed that the DPRC building materials not only can achieve significant building energy-saving but also enhance solar cell energy-generation efficiency, striving towards carbon neutrality by 2050, showing a great market potential.