Dynamic thermal performance analysis and experimental study of cascaded packed-bed latent thermal energy storage integrated solar trough collectors

The instability of the renewable energy significantly impacts the thermal performance of solar thermoelectric systems. In this paper, a coupling system consisting of solar trough collector and double-layer cascaded packed- bed latent heat storage system (PLTES) is constructed to investigate thermal performance and operating parameters under dynamic conditions. Additionally, the experimental platform was upgraded to evaluate the dynamic charging/discharging process of the cascaded PLTES. The results show that under dynamic inlet heat flow, the PLTES exhibits only one peak temperature difference, and the average temperature is lower than that in the steady-state. The cascade-packed structure promotes a more uniform temperature and liquid phase distribution, resulting in a longer heat flow output. Higher mass flow rates of the heat flow increase convective heat transfer and reduce the temperature difference, though they have little effect on the energy efficiency. Conversely, an increase in capsule diameter significantly reduces the energy efficiency. Experimental results indicate that under dynamic conditions, the total charge-discharge capacity of the cascade system decreases by 0.5 MJ and 0.9 MJ, and the energy efficiency decreases by 0.15. Nevertheless, the energy efficiency of the cascaded PLTES (0.57) is higher than that of the single layer (0.5).