Effective one-dimensional dynamic modelling of latent heat thermal energy storage units for heating applications

Abstract

Effective use of the energy stored within thermal energy storage systems requires mathematical models that faithfully represent the dynamics of interest. Although three-dimensional or two-dimensional models may provide an accurate representation of the thermal store, these are computationally intensive and may not be suitable for control system design or to simulate complex networks. Following this line, a low-order one-dimensional model of a latent heat thermal store is presented. The model is based on energy balance, the specific heat–temperature curve of the storage medium, and the dynamic calculation of the heat transfer coefficient. The simplicity afforded by the model facilitates its implementation in any programming language, guaranteeing its compatibility with commercial software to simulate complex systems. The model was implemented in MATLAB/Simulink and verified against experimental data of the real unit and simulation results obtained with a two-dimensional model. Simulation results for charging and discharging operations obtained with the one-dimensional model exhibit a root mean square error of ≤0.53 °C and a mean square error of ≤0.32 °C when compared with experimental results of the output temperature of the heat transfer fluid. These outcomes are deemed acceptable considering the low order of the one-dimensional model.