Application of numerical methods for the design of thermocline thermal energy storage: Literature review and critical analysis

Sensible or hybrid sensible-latent thermal energy storage systems are becoming mature systems and are the most common choice in high temperature applications. Among the different configurations for these systems, thermocline storages are a well-established one, presenting some advantages such as low cost and simple layout. The design of such systems is often achieved through numerical modeling and only a few experimentally validated systems are available. Considering the wide recognition of this technology also in other new fields of applications, such as new generations district heating and cooling or advanced power cycles, a deep knowledge of the numerical methods available and their main features is needed. In the present paper, an overview of numerical methods and codes applied for the design of thermocline storages is presented, discussing the constituent equations, additional correlations needed and the software and solvers employed. The effect of operating parameters according to the parametric analyses available is reported and a critical discussion is made, regarding the selection of the most suitable model for the various applications, as well as the proper range of design parameters.