Investigating the aspect ratio's influence on the exergetic performance and thermocline dynamics of a large water-based thermal energy storage system

The transition toward more sustainable district heating networks requires the use of thermal energy storage systems. For sensible storage systems, the influence of the aspect ratio on the storage performance is a core consideration. Herein, a two-dimensional, high-resolution, model was developed based on the finite element method using COMSOL Multiphysics and validated using measured data from a corresponding real-world storage system under operating conditions. Four additional models were derived to investigate the influence of the aspect ratio. The results show that a higher aspect ratio leads to increased heat loss to the environment and reduced exergetic performance. However, the capacity for more stable and more efficient thermal stratification is also increased. •CFD model for large water thermal energy storages•Validation of the CFD model by experiments•Energetic and exergetic efficiencies decrease with increasing aspect ratio.•The thermocline is more stable at higher aspect ratios.