Controlled Natural Ventilation Coupled with Passive PCM System to Improve the Cooling Energy Performance in Office Buildings

The building sector is responsible for consuming one-third of the global final energy use. In office buildings, high internal heat gains increase the cooling energy use. Thermal energy storage (TES) is a promising technology to decrease the cooling energy use, to achieve a low-carbon future, and to increase thermal comfort if properly designed. An appropriate use of the passive PCM system and natural ventilation can provide long-term energy and thermal comfort benefits. Many factors influence the efficient use of passive PCM system in buildings, such as outdoor/indoor boundary conditions, and HVAC control strategies. In office buildings, the PCM passive system integrated into the building envelope has the potential to regulate the indoor air temperature by absorbing high internal heat gains during day, however, discharging the PCM during night to work efficiently for the next day remains a challenging design criterion. The passive PCM system would not work efficiently if charging/discharging cycle is not completed. Whole-building energy simulation tools and numerical models are essential to deal with this issue. The present study is aimed at defining cooling energy savings in office buildings located in temperate climates applying PCM and natural ventilation passive technologies. A reference small office building was chosen and PCM panels with optimised melting temperature together with different natural ventilation control strategies were applied to an office building model. EnergyPlus airflow network capability was used to calculate the natural ventilation potential induced by wind and buoyancy effects. Simulation results have shown cooling energy savings from 8% to 15%. In addition, natural ventilation could increase the efficiency of PCM by 8%.