UC Davis

Phase Change Materials (PCMs) have the potential to reduce the cooling and heating energy consumption of buildings. The high latent heat of PCMs helps them to absorb and release large amounts of energy when the PCM changes phase from solid to liquid and from liquid to solid respectively. The climatic conditions and the thermophysical properties of the PCMs play a crucial role and thus, understanding the impact using a particular PCM in a particular climatic condition needs to be understood thoroughly before adding PCM to the building envelope. Previous research has shown that addition of PCM to building envelopes does not always reduce energy consumption.

In this research project, the performance and heat transfer characteristics of two PCMs integrated in a typical residential wall in California was characterized using simulations. PCM 1 is a spackle type product that can be applied to the inner wall and consists of 53% PCM. PCM 1 is a blend of different PCMs and has a melting range from 280K (6.85˚C) to 300K (26.85˚C). PCM 2 is a salt based PCM and is encapsulated inside panels of plastic material. PCM 2 has melting 294.15K (21˚C) to 294.95K (21.8˚C). The typical residential wall with no PCM integrated was used as a baseline and a total of 8 PCM-integrated wall designs were studied using simulations, and their impact on reducing cooling and heating energy consumption in comparison to the baseline case was analyzed. The Sacramento weather was used in these studies and representative days of Winter, Summer, and Shoulder were tested. Addition of PCM 1 to the inner wall surface did not produce any significant energy savings for the Winter day and Shoulder day. But adding PCM 1 to the inner wall surface produced 6.7% drop in the cumulative heat leaving the inner wall surface and entering the house for the Summer day and thus, has the potential to reduce cooling energy consumption. Addition of PCM 2 to the inner wall surface does not reduce the energy consumption of the Winter day and the Summer day to have any significant impact. PCM Next to Studs was a design tested where the PCM was placed between the stud and the insulation. PCM inside Insulation+Stud Layer was another design tested where cubes of PCM were uniformly distributed inside the Insulated+Stud blended layer. For the PCM Next to Studs and PCM inside Insulation+Stud layer the behaviors of PCM 1 and PCM 2 are significantly different but results in reduced heating energy consumption for the two Winter representative days simulated. The results indicated that the for all the different wall designs tested in the Sacramento weather no significant energy savings are generated by use of the two specific PCMs characterized in this study.