Design of high temperature thermal energy storage for high power levels

A latent heat thermal energy storage unit has been modeled, simulated and designed for integration into a cogeneration plant that supplies steam to industrial customers in Saarland, Germany. The design consists of a vertical bundle of extended finned tubes surrounded by phase change material in the shell. The heat transfer fluid water/steam flows through the tubes between the upper and lower headers. A new fin design was developed to achieve the required high power levels. The storage system was designed and analyzed with the development of an iterative multi-step method. The method spans from the design of the fin, based on both empirical and geometrical information, to the heat transfer analysis of a storage system. The analysis is comprised of several steps: a heat transfer analysis of the cross-section of one tube without modeling the heat transfer fluid, a transfer from the cross-section to a simplified one-dimensional radial model and a two-dimensional axial and radial analysis coupling the axial flow of the heat transfer fluid and the radial heat transfer into the storage. The developed analysis method and the resulting storage system are presented and the comparison of different fin designs shows the suitability of each fin for different applications.