Indirect effects of solar energy on phase change material-based thermal energy storage unit

Understanding the effects of indirect solar heating on latent thermal energy storage systems, under various heat transfer fluid conditions, is essential to optimize their applicability in real-life conditions. This study aims to investigate the influence of solar energy on a latent thermal energy storage system, using two types of paraffin: refined paraffin and paraffin mixed with aluminum dust. Torada C32 oil was chosen as the heat transfer fluid for its favorable thermal properties. During the tests, the temperature of the phase change material was measured at two points along the heat transfer fluid path and at three points inside the storage unit. The results obtained reveal that an increase in the heat transfer fluid flow rate from 0.2 to 0.36 L/min accelerates the charging phase by 10 % and delays the discharging phase by 15 %. Furthermore, the use of paraffin mixed with aluminum dust resulted in a 24 % delay in the discharge process. It was also concluded that fluctuations in the temperature of the heat transfer fluid between 30 °C and 80 °C have minimal impact on the charging phase, with the melting time being significantly longer than the fluctuation period. • Heat Transfer Fluid flow increase accelerates charging by 10 % but delays discharge by 15 %. • Heat Transfer Fluid temperature fluctuations (30–80 °C) minimally affect charging phase. • Phase Change Material shows axisymmetric melting while convection drives top-down heat transfer. • Paraffin mixed with aluminum dust resulted in a 24 % delay time in the discharge process.