Parametric study for a structured thermal energy storage system for concentrated solar power plants

The objective of this paper is to study and optimise thermal energy storage systems of structured thermocline type. The system consists of a solid filler material made from waste ceramic products and a set of channels through which the heat transfer fluid flows. A well-verified and validated unsteady and one-dimensional computational model was developed for this study. The investigation is carried out considering three main output values: outlet temperature, thermocline thickness and discharged exergy. The behaviour of several parameters, such as the flow velocity and cut-off temperature difference, the height and the diameter of the tank, together with the void fraction and the diameter of the channels, were studied. The results suggest that increasing the cut-off temperature, tank diameter and height, and/or void fraction reduces the thermocline thickness. Similarly, decreasing the flow velocity and/or channel diameter leads to a reduction in thermocline thickness. In order to increase the discharged exergy, it is necessary to reduce the cut-off temperature, flow velocity, or channel diameter while increasing the void fraction, as well as the diameter and height of the unit. This work outlines design guidelines aimed at optimising operational and geometrical parameters to achieve improved efficiency for structured thermocline systems.