CFD-based reduced model for the simulation of thermocline thermal energy storage systems

Thermocline thermal storages are widely used in energy systems. Computational Fluid Dynamic (CFD) can be used for an accurate simulation of the physical phenomenon but its implementation in system-level annual simulations is hardly possible because of the huge computational time required. The present paper proposes a novel approach for the utilization of CFD simulation results in system-level annual simulations and optimizations. An analytical function able to represent the dimensionless vertical temperature profile inside the tank is parameterized statistically using the results of multiple simulations of a CFD model, which have been previously validated with experimental data. The reduced model obtained is then compared to other CFD simulations under highly variable conditions, showing a satisfactory degree of agreement (the mean absolute error and the error standard deviation are calculated to be 1.52 K and 1.93 K respectively). Furthermore, it is demonstrated that this approach can be conveniently adopted for the modeling of a wide range of systems with a single tank thermal energy storage, from Concentrated Solar Power to District Heating.