Experimental characterisation of a molten salt thermal energy storage with filler

This paper presents an investigation into the performance of stratified thermal energy storage systems using molten salt. The focus is on the impact of introducing filler materials with lower price per thermal capacity than the molten salt to reduce cost. The performance of such systems is highly dependent on the quality of thermal stratification achieved within the storage. The availability of experimental data of such systems is limited so far. Therefore, an experimental setup was developed to conduct comparative analyses between single media and dual media configurations within the same storage tank. The thermal stratification was observed before and after the introduction of ceramic filler materials, allowing for a direct comparison of the two configurations. The data provides the ability to validate the accuracy of a 1D numerical model in predicting temperature stratification. The successful validation underlines the model's relevance for predicting the performance of actual storage systems. The analysis examines the impact of fillers on thermal stratification and demonstrates their effectiveness in limiting the expansion of the thermocline, particularly during standstill periods. High storage utilization rates in cyclic operation and the impact of varying threshold criteria defining the end of charging and discharging are demonstrated for the first time for this type of dual media stratified single tank storage system operation with molten salt. The presented research offers valuable insights into selected aspects of the design and operation of molten salt thermal storage systems. The findings contribute to the development of cost-effective and efficient thermal energy storage solutions, supporting the broader integration of renewable energy resources. Core message: The presented experiments of a molten salt thermocline energy storage with ceramic filler allow to validate a numerical model and to demonstrate promising KPIs. • Enhanced molten salt thermal storage with fillers. • Validation of efficient 1D-numerical model. • Comparative single and dual media analysis. • Fillers stabilize stratification during idle times. • Utilization rate in charge/discharge storage cycling up to 92 %.