Phase change materials with ceiling ventilation system to reduce summer cooling loads

This work deals with the evaluation of the performances of phase change materials (PCMs) coupled with a ventilated ceiling system in order to reduce summer cooling loads and improve the internal comfort in buildings, thus enhancing the positive effect of night ventilation. Object of the study is the numerical simulation of the thermal behaviour of a typical open space office located in three Italian cities during the summer. Indoor climate is only controlled by means of passive ventilation; a usual ventilation system configuration (i.e. the outdoor air is supplied directly inside the ambient) is compared with another characterised by the PCM activation by means of a ceiling air-PCM exchanger. Both systems provide daily and night ventilation and are aimed to maintain, as much as possible, thermal comfort conditions during the office working hours. The numerical simulations are performed using an explicit dynamical model, with a finite difference discretization, developed on the software Simulink®. The PCM is modelled with the equivalent heat capacity method. The results show the positive effect of PCMs, if activated by means of intensive night ventilation. This measure allows to appreciably reduce the peak cooling loads and to achieve a good indoor thermal quality.