Experimental and numerical study of an energy-efficient building fenestration system with seasonal adaptability

Abstract

Previous building-integrated solar thermal fenestrations were limited to the single function, either air heating or water heating. Thus, they failed to meet the seasonal thermal needs of buildings. To address this limitation, this paper proposed a novel building fenestration-integrated solar collector. This system is designed to harness solar irradiation on the fenestrations for air heating in winter and recover irradiation for water heating in summer, effectively addressing seasonal thermal demands and improving annual solar utilization efficiency. Firstly, the prototype of the proposed system was fabricated, and its thermal performance was tested. The experimental results indicated the thermal efficiency of 40∼50% for air heating and 39% for water heating. Subsequently, a mathematical model of the proposed system was developed and experimentally validated. Based on the validated model, a comparative performance analysis was conducted between the proposed system and double clear glazing. Additionally, the energy-saving potential and economic viability of the proposed system were predicted. Compared to double clear glazing, the proposed system exhibited a higher solar heat gain coefficient (SHGC) in air heating mode, lower SHGC in water heating mode, and lower U value at night. The prediction outcomes underscored the substantial energy-saving advantages conferred by the proposed system across diverse building types. The projected payback periods in subtropical and tropical regions were estimated to be around 2–4 years.