Thermal storage performance of molten salt thermocline system with packed phase change bed

• Molten salt thermocline storage with packed phase change bed is simulated.
• Phase change material can remarkably increase the effective discharging energy.
• Thermocline can be divided into three stages including phase change layer.
• Melting point of phase change material should be slightly below initial temperature.
• The discharging efficiency increases with the phase change material content.

Comprehensive transient and two-dimensional numerical model is developed to study energy storage performance of molten salt thermocline thermal storage system with packed phase change bed in solar thermal power. The results show that the packed phase change bed can remarkably increase the effective discharging energy and discharging efficiency. Because of phase change material, the thermocline can be divided into three stages including the high temperature thermocline, low temperature thermocline and phase change layer. As the melting point within the inlet and initial temperature increases, the whole discharging time decreases, while the effective discharging energy remarkably increases, and thus the melting point of phase change material should be within the initial temperature and effective outlet temperature for good heat storage performance. As the phase change material content increases, the effective discharging energy increases with the effective discharging time rising, and the effective discharging efficiency also increases.