Experimental study on combined sensible-latent heat storage system for different volume fractions of PCM

•A novel combined sensible-latent heat thermal energy storage system has been proposed.•Effect of system performance under different volume fractions of PCM is investigated.•Charging and discharging time is increased with the increase of volume fraction of PCM.•Investigated the effect of mass flow rate on charging and discharging characteristics. Renewable energy sources are unable to provide continuous energy because of their sporadic nature. To counter this, in the case of solar thermal energy applications, there is a need for effective thermal energy storage. The concept of single tank thermocline storage is considered as a potential cost-optimized approach for medium thermal applications. Although, one of the major disadvantage of this design is greater degradation of the thermocline during the discharge cycle, which results in poor performance. In the present work, a novel combined sensible-latent TES system is proposed to combat these problems. A combined sensible-latent TES system is designed by incorporating the PCM spherical capsules above the concrete spheres in the same storage tank. An experimental study has been performed to investigate the effect of four different volume fractions of PCM on the performance of the proposed TES system during charge and discharge cycles. The increase in volume of PCM has a significant impact on the performance of the system. The higher volume fractions of PCM have greater energy storage, extraction and cumulative energy transfer than the lower volume fractions. The volume fraction of 80% and 60% shows better performance than the 40% and 20% volume of PCM. Based on the results, it is recommended that charging at higher flow rates provides faster charging and discharge at lower flow rates provides better utilization of energy for a longer duration of time in case of solar thermal applications.