Numerical investigations of high temperature packed bed TES systems used in hybrid solar tower power plants

Abstract

Packed bed thermal energy storage systems with air as high-temperature heat transfer fluid are a cost effective technology for air-based hybrid solar tower plants. A scheme of this plant has been proposed and an optimal mathematical heat transfer model has been formulated to investigate the cyclic thermal behavior of two packed bed TES systems within this plant. The first TES system stores energy at high-temperature (around 1000°C) and at high pressure (around 10bars), while the second one stores energy at 650°C and under atmospheric pressure. The developed model in this study is a dynamic 1-dimensional two-phase heat transfer model, which incorporates variable thermophysical properties for both fluid and solid phases, and hence, enables an accurate prediction of the TES system dynamic. A numerical method for solving the model equations is described in this effort, as well as the required physical correlations. Based on this model a simulation tool was developed in the environment of MATLAB R2011b, and was validated with previous experimental and simulation studies. This calculation tool is fast compared to previous models; thus, it enables the prediction of the cyclic performance of packed bed TES technology at high temperature and pressure working ranges in a relatively short simulation time.