Thermal energy storage systems provide the potential to attain energy savings and reduce the environmental impact related to energy use. In this respect, phase change materials (PCMs) work as `` latent heat storage units'' which store or release large amounts of thermal energy. The aim of the presented study is to determine the function of PCM in an actively operating cold store at - 18oC during an operational failure or electricity shortage. The indoor temperature of the cold store, PCM temperature in the macrocapsules and ambient temperature are the continuously monitored parameters in this research. The results indicate that PCM macrocapsules, which cover 10% of the total heat transfer surface area, provide significant temperature maintenance under all ambient conditions and prominently extend the time to break the cold chain.