Numerical evaluation of a phase change material-shutter using solar energy for winter nighttime indoor heating

The incorporation of phase change materials in movable structural cells of shading elements associated with southward-facade windows is evaluated in this article. The proposed phase change material-shutter is a thermal energy storage system designed to take advantage of solar energy for winter nighttime indoor heating. A two-dimensional phase-change heat diffusion model based on the enthalpy formulation was considered. The numerical model follows the finite-volume method with a fully implicit formulation and allows the alternating melting and solidification of a phase change material submitted to cyclical thermal boundary conditions. Parametric investigations were carried out about the effects of thermophysical properties of the phase change material and temperature and convection heat transfer boundary conditions on the charge/discharge rates of energy. Due to the low thermal diffusivity of the phase change material, an aluminum fin arrangement was considered as a heat transfer enhancement technique. The distance between fins is directly proportional to the daily energy storage/release capacity of the system. The solar radiation flux has a strong effect on the charging/melting processes during the day. The indoor temperature and the interior convection heat transfer coefficient have a major influence on the discharging/freezing processes during the night. The design of the phase change material-shutter depends strongly on the thermophysical properties of the phase change material and on the interior and exterior boundary conditions considered.