Passive building cooling achieved with a new class of thermal retrofit: The liquid vapour phase change material

Abstract

For a period covering more than half of the last century and until now, the term “phase change material” (PCM) in context of passive building coolingunanimously referred to a class of materials undergoing solid–liquid phase transition in cyclic manner. In contrast to solid–liquid PCMs (SLPCMs), the liquid-vapour phase transition has not been capitalized in a similar way to cool buildings by passive means despite the clear notion that the latent heat of evaporation exceeds the latent heat of fusion by a significant margin. The present work is an endeavour towards offering a new passive cooling system for buildings in hot climate with the help of liquid–vapour phase transition. Unlike existing active evaporative cooling systems, the liquid–vapour PCM (LVPCM) system does not require any external power supply to induce cooling effect. In the hot climate of Delhi, India, a peak temperature dip of 2.22℃ was achieved with the LVPCM system. An average indoor heat gain reduction of 13.56% was realized which reached a maximum value of 20.51% during the experiment. This novel system could overcome the night time heating issue of SLPCM. Furthermore, several additional benefits (such as the use of environment friendly and low-cost materials, ease of installation etc) could make LVPCM a competitive alternative to the prevailing SLPCM technology.