Mathematical Model of Packed Bed Solar Thermal Energy Storage Simulation

Mathematical model has been developed to assess the effects of using phase change materials (PCM) in a fully mixed water accumulation tank. Packed bed system of spheres with a diameter of 40 mm have been considered as an option to increase energy storage density. A continuous phase model has been applied to analyse the influence of phase change during a charging and discharging processes. The methodology for calculating energy mass flow, density of water, heat transfer between layers, temperature for each time step and energy transferred to PCM is given. Single type of PCM with melting temperature of 55 °C and multiple type PCM system (65, 55, 45 and 35 °C) are compared. It is found that multiple type PCM system compared to only water and single type PCM systems, provide lower return temperatures and higher energy density.