Modeling a hot water storage tank for thermal energy storage using encapsulated phase change materials (PCMs)

Over the past few decades, there has been a steady increase in the use of solar water heaters in areas of the world that have large amounts of solar energy. However, as the sun can only provide energy for a portion of each 24-hour solar cycle, there is a need to augment the solar-powered water heaters with thermal energy storage systems. These systems feature Phase Change Materials (PCMs) that can store extra energy in order to provide sufficient power to, for instance, offset potential shortages which might occur due to low production times such as occur at night or on a heavily clouded day. PCMs can experience phase changes from solid to liquid (i.e., melting solidification) when heated to a temperature that accords with the thermal application being used. The present thesis study will investigate ways to enhance thermal efficiency in hot water tanks by applying potential numerical simulations using PCMs that incorporate paraffin wax. Finding the most expedient PCMs for the finite element model includes finding changes in thermal conductivity and enthalpy across different temperatures. Elements which enhance efficiency (e.g., raise the thermal conductivity level in paraffin wax) potentially include utilizing encapsulated PCMs for spheres on the heat exchanger and changing the time needed in the melt/solidification process. The present study also includes an overview of the latent heat energy storage system (LHESS) and the theory underlying it.