Applicability of phase change materials (PCMS) for peak load shifting of air conditioning and mechanical ventilation (ACMV) systems of office buildings in tropical climates

Abstract

Air Conditioning and Mechanical Ventilation (ACMV) Systems are often used to maintain the thermal comfort and the indoor air quality in office buildings in tropical climates. These ACMVs usually account for more than 50% of the total energy consumption of the buildings. Compared to other available technologies, use of Phase Change Materials (PCMs) has been identified as an attractive innovative technology to reduce the peak cooling load and also to shift the peak cooling load to after office-hours. Temperature of building envelopes constructed using conventional materials such as bricks and concrete tend to vary with the surrounding environmental conditions, as they only absorb or release the sensible heat. On the contrary, PCMs can absorb or release much larger amount of thermal energy from/to the surrounding as latent heat, while maintaining the building envelope temperature unaffected under varying environmental conditions. Thus, conventional building envelopes accompanied with PCMs are able to significantly reduce the external heat gains into the conditioned spaces of the buildings, resulting a significant reduction in the peak cooling load. This study is mainly focused on exploring the applicability of PCMs for hot and humid tropical climates. Numerical analysis supported and validated by an experimental program and a case study revealed that by covering exterior of building envelop with 5 mm - 10 mm thick PCMs can reduce the building peak cooling load by 8% - 12%. Moreover, it was found that the peak cooling load could be easily shifted to after office hours by increasing the PCM thickness. Economic analysis showed that the PCMs with higher thermal cycles reduces the pay back periods up to 2 - 3 years and, further supported the use of low-temperature PCMs for building applications. Findings of this study recommend to incorporate the PCMs on the building envelops of the sunlit walls to reduce the peak cooling load of the building with the aim of reducing the energy consumption by the ACMV system.