Free-cooling of buildings with phase change materials

In this paper, the application of phase change materials (PCM) in free-cooling systems is studied. Free-cooling is understood as a means to store outdoors coolness during the night, to supply indoors cooling during the day. The use of PCMs is suitable because of the small temperature difference between day indoors and night outdoors. An installation that allows testing the performance of PCMs in such systems was designed and constructed. The main influence parameters like ratio of energy/volume in the encapsulates, load/unload rate of the storage, and cost of the installation were determined, and experiments were performed following the design of experiments strategy. The statistical analysis showed that the effects with significant influence in the solidification process are the thickness of the encapsulation, the inlet temperature of the air, the air flow, and the interaction thickness×temperature. For the melting process the same holds, but the inlet air temperature had a higher influence than the thickness of the encapsulation. With the empirical model developed in this work, a real free-cooling system was designed and economically evaluated.