THERMAL ENERGY STORAGE WITH MULTIPLE FAMILIES OF PHASE CHANGE MATERIALS (PCM)

The world is facing a major challenge when it comes to proper energy utilization. The increasing energy demand, the depleting fossil fuel resources and the growing environmental and ecological concerns are factors that drive the need for creative solutions. Renewable energy resources such as solar sit in the center of these solutions. Due to their intermittent nature, development of energy storage systems is crucial. This dissertation focused on the latent thermal energy storage systems that incorporate phase change materials (PCM). The main goal was to enhance the heat transfer rates in these systems to address the low melting (energy storage stage) and solidification (recovery stage) rates that are caused by the PCMs’ low thermal conductivity values. The application of multiple PCMs (m-PCMs) with varying melting temperatures in several arrangements was investigated. The effects of applying m-PCMs on the conduction heat transfer and on the natural convection heat transfer in both horizontally and vertically oriented heat exchangers were studied. This was followed by an optimization study of the PCMs’ melting temperatures and the working fluid flow rate. Further heat transfer enhancement using metal fins was also investigated. Numerical models were developed and validated. Results are reported and discussed. Significant enhancement in both complete melting time and energy storage capacity was obtained by the m-PCMs in series arrangement. This enhancement is more pronounced in the vertically oriented system. The working fluid flow rate was found to have a limited effect during the melting stage. However, it seems to be crucial in the solidification stage