Rocky Tam, M.Eng. 2012
Supervisor: Dr. Rodrigo Mora
The use of alternative materials is becoming increasingly important in the construction industry. Whether they are sustainable, high performance, or simply lower cost, alternatives often have some different characteristics that can be appealing in some way. One promising alternative in construction is phase change material (PCM). PCMs are designed to have a high latent heat of fusion and store energy at a constant temperature through the phase change process. PCMs simulate thermal mass much like concrete would, reducing peak temperature loading and inducing a time lag on the indoor air temperature, increasing thermal comfort and saving energy. While PCMs can act like concrete, they are much smaller, making them ideal for retrofit options where space is limited. PCMs are also ideal for passive houses, where extreme air tightness, high R values, and large solar gains can cause overheating without proper thermal management.
This research project ultimately sought to determine the effectiveness of using PCMs in Vancouver through the use of a life cycle cost analysis. This goal was achieved through three successive phases using various software and experimentation with a sample of BioPCM. The first phase involved testing with a heat flow meter (HFM) and creating a simple analytical model. With the HFM, heat flow testing was performed on a PCM sample, creating heat flow data that was used to create the analytical model. The testing also determined the 1D thermal resistance of the PCM that was used for whole building energy modelling later on. The analytical model was created in MATLAB to predict the thermal behaviour of the PCM, allowing for the creation of more comprehensive models later. The second phase of the project involved small scale testing and the creation of a more comprehensive analytical model. The small scale testing was done by constructing two identical test chambers simulating a house and placing them side by side. One of the chambers would have samples of PCM inside. With a local weather station nearby and thermocouples inside the box, temperature data could be collected over a period of time. The temperature behaviour of the boxes could be observed and the effects of the PCM analysed. A new analytical model, based on the previous model (Phase 1), was created that would simulate the behaviour of the small scale test chambers. Using the weather data collected as input, the model was made to simulate the thermal behaviour inside the test chambers. The simulation was compared to the measured data from the actual testing in order to validate the model and refine it. The third phase of the project involved evaluating the life‐cycle cost benefits of using PCM on a passive house in Vancouver based on energy simulations and using the PCM results calibrated from the mallscale experiment (Phase 2); as well as monitoring a house with PCM in the attic located in Burnaby, BC. Unfortunately due to time constraints, the life cycle cost analysis was not completed. The life cycle cost analysis would have utilized the modelling results from the previous phases in a whole building energy model. The home monitoring portion was managed by John Lovatt and involved the placement of BioPCM into the ceiling/attic space of his home.
The results of the project showed that the latent heat storage of the PCMs had a noticeable effect in controlling the thermal behaviour of the environment. In both the small scale testing and the home monitoring, the effect of the PCM was clear, the indoor temperature was heavily influenced by the temperature of the PCM rather than the temperature outdoors or in the attic space. The peak temperatures were less extreme and a time lag was induced, delaying the peak temperatures by a few hours.
This project shows that PCMs can be effective in Vancouver. They can potentially save energy by reducing peak loads and thermal comfort. However, there are a lot of opportunities for further validation of the project, such as completing the life cycle cost analysis to validate the performance of the PCM throughout the year and quantify the energy savings it provides.