Three-dimensional FEM model to study and improve the heat transfer in concrete for solar thermal energy storage.

摘要

everal thermal energy storage (TES) systems for solar thermal power plants have KA6 been developed over the past two decades. Concrete has been used lately as an inexpensive energy storage medium. A literature review was performed to obtain information about the current status of solar power concentration technologies, storage systems and materials. A summary/analysis of the achievements, limitations, and necessary improvements to previous computer modeling for TES systems is presented with a focus on sensible heat in solid media. A 3-D finite element computer program was used to study and improve the heat transfer process for thermal charging and discharging of concrete. The three-dimensionality of the program was required to account for the effect of fins attached to the pipe. The fans cause variation in the temperature distribution in all directions of the cylindrical coordinates used in the model. Fin configurations including rods, disks, plates, and spirals (auger) attached to the steel pipe have been studied along with their contribution to the reduction of the duration of the heating cycles. Based on duration of charging cycles of one hour, the reductions obtained were 12.06%, 25.04%, 42.8%, and 49% when using 8 rods, 4 disks, 2 plates and 6 spirals, respectively. The configurations with four disks and six spirals have been found to be the most feasible designs based on thermal performance, costs, and practicality for construction. Furthermore, the design of a laboratory scale thermal energy storage unit is documented in this thesis. The unit consists of commercially available components that will allow testing the concrete mixtures developed for this project while reducing the cost of equipment from roughly