Evaluation of PCM activation using changes in physical properties during phase transition for visualization of passive building envelope technologies

Paper in proceeding, 2016

There is a large potential to use passive technologies for increasing the thermal comfort and reducing the energy use for heating and cooling in buildings. In many cases the occupants of the building lack good practical understanding and knowledge on how these passive technologies function. Therefore, there is a challenge to utilize their full potential. For instance, the potential energy savings for space heating and cooling is 5-21 % with phase change materials (PCMs) integrated in building envelopes (e.g. encapsulated in the plaster board). Consequently, there is a pedagogical problem to explain how and when PCMs are active in regard to passive adjustment to changes in the indoor environment. The reason for this is the lack of proper tools. Temperature sensors alone or numbers on the energy use is not enough to give the occupants information on how to use the passive technologies in the most efficient way. One aim of this study is therefore to explore properties that can be used as a foundation for the development of technologies for visualizing the phase transition. Laboratory experiments are used to evaluate three methodologies based on density, viscosity and optical properties that change when a PCM undergoes a phase transition. The results are compared to phase transition measurements by DSC. The methods are tested on a type of organic PCMs, polyethylene glycol (PEG), of different molecular weights. From the results it is obvious that all three methods can be used to differentiate the phases even if there remains challenges before practical implementation in buildings is possible.