Preparation and thermophysical performance of diatomite-based composite PCM wallboard for thermal energy storage in buildings

Abstract

Phase change materials (PCMs) are commonly used in latent heat storage systems. Two novel diatomite-based, shape-stabilized composite phase change materials (PCMs) were compounded by incorporating organic alcohol PCMs into diatomite. The chemical, morphological, and thermal performances of the composite PCMs were evaluated using Fourier transform infrared spectroscopy, scanning electron microscopy, and differential scanning calorimeter analyses. As the organic alcohol PCMs were incorporated into the diatomite pore structure, the resulting composite PCMs presented good chemical stability. The phase-change temperatures of the two composite PCMs (designated TC35 and HC42) were in the ranges 33.1–35.1 °C and 41.7–42.7 °C, respectively. The latent heats were 90.5 ± 1.5 J/g and 92.6 ± 1.3 J/g, respectively. PCM-contained wallboards (PCMWs) were then fabricated and attached to the exterior surface of a test room wall to evaluate their thermal performance against that of polystyrene plastic insulation wallboards. The impacts of both the wallboard location and the phase transition temperature on the PCMWs were investigated. It was observed that the external surface temperature of the PCMW was lower than that of the traditional polystyrene plastic insulation wallboard owing to the former's more favorable thermal storage capacity. The thermal resistance of the PCMWs, however, was too small to reduce the indoor cooling loads in summer. Enhancing the thermal insulation performance of the wallboard is required in order to obstruct the outdoor-to-indoor heat transfer and thus save daytime energy; however, this is unfavorable for heat dissipation at night. The optimal phase transition temperature was found to depend on not only the outdoor meteorological conditions but also the location of the PCMW.