PCM-Metal Foam Composite Systems for Solar Energy Storage

Efficient storage of solar thermal energy has been a key research area in recent years. Among the various methods for energy storage, phase change material (PCM) based latent heat systems have shown a lot of promise due to their high energy storage densities and smaller system sizes. However, the low thermal conductivities of PCM pose a significant challenge in designing such systems, therefore, augmentation with suitable thermal conductivity enhancers becomes necessary to improve their energy charging and discharging performances. The use of metal foam structures embedded in PCM to form composite PCM-metal foam energy storage system can improve the effective thermal conductivity remarkably due to the high surface area for heat transfer between the metal foam and the PCM. This chapter presents a study of PCM-metal foam composite systems for solar energy storage. At first, a brief overview of the relevant thermal enhancement methods with particular emphasis on metal foam systems is presented. This is followed by the description of a typical PCM-metal foam composite system and the important parameters governing its energy storage performance. Different modelling approaches for such systems and their advantages and disadvantages are presented. The effect of important factors for metal foam-PCM composite systems are analyzed by performing pore-scale simulations. It is shown that factors such as metal foam porosity, pore size distribution, foam material, phase change material and overall system size contribute significantly towards the melting pattern and energy storage characteristics of these systems.