Hysteresis model predictions of thermal performance of hempcrete-based walls with phase change materials

Abstract

Phase Change Materials (PCMs) can improve the energy performance of buildings by storing and releasing large amounts of thermal energy with low or no temperature variation. However, they require optimal integration to be fully effective. While numerical analysis can assist the successful integration of PCMs into building envelopes, only a few tools can simulate the hysteresis effect, and all of them introduce simplifications that might hinder prediction accuracy, especially in case of interrupted phase change. This work addresses these limitations by proposing a novel algorithm for realistic hysteresis modelling by introducing a new path for changing the liquid fraction during the partial phase change process to enable the phase change curve transition without assuming that the liquid fraction is constant. The new model was validated against experimental results and compared to three widely used PCM hysteresis methods: Track, Switch, and Scale. This study is also the first to compare the effect of several hysteresis models applied to two different PCM integration methods into hempcrete wall assemblies based on microencapsulation and macroencapsulation techniques. The results of the different hysteresis models vary significantly depending on the PCM integration technique, the observed design parameter, the schedule heating setpoints, and the PCM percentage in the wall. When applied to a hempcrete wall with a PCM panel, the models showed a significantly higher sensitivity in the three performance parameters (heating energy consumption, liquid fraction, and inner temperature) than when applied to a hempcrete wall infused with the microencapsulated PCM.