Analysis for temperature stability and thermal transport performance of cascaded phase change packed bed thermal energy storage system under unstable factors

Thermal energy storage technology can provide better mitigation of thermal and mass fluctuations in energy systems, ensuring that an integrated system can work under the designed operating conditions. In this work, the radial temperature uniformity of steady and Gaussian-like unsteady sources is first investigated. Various thermodynamic evaluation indexes are then used to study the effects of two key unsteady conditions, i.e., temperature and inlet flow, on the thermal transport performance of the phase change packed bed. As last, the amplitude and proportion of the key factors are further analyzed by using Taguchi's method. The results show that the radial temperature inhomogeneity index (RTII) relatively increases to maximum by 140.06 % with the peak value and proportion of the unsteady mass source. As the peak value and proportion of unsteady heat sources increase from their minimum values to maximum ones, the total thermal energy storage and latent heat proportion rise by 20.04 % and 40.43 %, respectively. Similarly, for the unsteady mass sources, the total thermal energy storage and latent heat proportion increase by 46.22 % and 73.33 %, respectively. The key factors function as a whole and reinforce each other. This work provides guidelines for designing the controlled operation of thermal energy storage under unsteady conditions.