Numerical study of the feasibility of coupling vacuum isolation panels with phase change material for enhanced energy-efficient buildings

Abstract

Effective thermal performance of a building envelope is crucial to reduce total energy consumption in buildings. In the past decades, different insulating materials and techniques have been proposed to improve building energy efficiency. Among various insulating materials vacuum insulation panels (VIPs), due to their extremely low thermal conductivity, become one of the emerging materials, striving for replacing conventional insulation materials. From different perspectives, phase change material (PCM) is another promising material with a large amount of latent heat capacity to improve building thermal inertia. Much research has been conducted for PCMs or VIPs individually. However, there are rare studies found in the literature to integrate both materials in the building envelopes. Therefore, this study aimed to evaluate the feasibility of an energy-saving building wall by coupling VIP with PCM as a compact unit that could significantly reduce heat flux through the wall, thereby leading to a tremendous reduction in energy consumption. The aging effect of VIP is also considered to examine its long-term thermal performance and compared with that of a traditional thermal insulation material-expanded polystyrene (EPS). The results reveal that the combined utilization of VIP and PCM in the same building envelope can reduce the heat flux oscillation through the wall more effectively, as compared to using the individual one. The maximum heat flux oscillation through the wall is found in direct proportion to the amplitude of the input loading, and inverse proportion to the VIP and PCM thickness. In addition to decreasing the heat flux oscillation through the wall, the integration of the PCM layer also causes a time delay on the peak heat fluxes, showing great potential to shift the electricity load from peak to off-peak hours. Results also show that the VIP with extremely low thermal conductivity allows the building envelope to achieve the same thermal performance with up to 77.3% of wall thickness saved compared with EPS. Moreover, the optimal integrating location of PCM is found to be on the interior side of the VIP layer under various loading conditions. The optimal PCM melting temperature of the PCM-VIP-based wall is highly dependent on the input loading conditions in direct proportion.