Enhanced performance of laminated PCM wallboard for thermal energy storage in buildings

Abstract

Research interest into the application of phase change materials (PCM) as energy storage materials in buildings has gathered momentum over recent years. PCMs utilising latent heat produced during phase change transformation processes do attain higher energy density with small temperature difference than other storage media using sensible heat. One potential concept being pursued for minimising cooling and heating loads is the integrated PCM wallboard system. This system is based on randomly mixing PCMs into wallboards. However trial samples have so far failed to overcome the heat and mass transfer barriers associated with the thermal behaviour of PCMs. This study evaluates the concept of laminated-PCMs as integral part of wallboard system in building fabric. This novel approach of integrating PCMs promotes rapid transfer of latent heat, sharp response to indoor temperature, and minimises multidimensional mode of heat transfer. It also facilitates production and recycling methods of wallboards The investigation into the thermal performance of the laminated wallboard system was done numerically. In order to address the moving boundary phenomenon the finite difference method incorporating implicit enthalpy method was used. Through series of heat transfer simulations and under different sets of properties and conditions, the surface temperature variations were obtained. The temperature variations were then used to calculate the heat flux and the total amount of heat transferred in and out of the wallboard. For the purpose of comparison, simulations were also carried out for randomly mixed PCMs during heat storage and discharge processes. The results showed a great advantage of the laminated PCM-wallboard system over the randomly mixed PCM type in terms of enhanced thermal performance, rapid heat transfer rates under narrow temperature swing. For instance maximum instantaneous enhancement in heat flux was about 20-50 % higher during the phase change process and up to about 18% more heat storage and release capacity. Practical development is however urged towards validation and production assessment.