Experimental evaluation of a double-layered radial flow packed bed thermal energy storage

High-temperature thermal energy storage (TES) is increasingly regarded as essential for sustainable energy systems, enabling the decoupling of supply and demand in renewable-heavy scenarios where flexibility and reliability are critical. This work builds on previous authors work and presents a novel double-layered packed bed TES prototype and its experimental assessment. The prototype, with 35 kWh capacity, operates between 20 °C and 600 °C at ambient pressure. Its key feature is two coaxial particle layers, whose sizes can be independently adjusted to test multiple configurations, offering unique flexibility for performance evaluation. Experiments explore variations in charging/discharging mass flow rates, operating temperatures, and particle/layer sizes. Temperature sensors embedded within the bed capture detailed thermocline development. Performance is quantified through key performance indicators and dimensionless parameters. Results show robust and repeatable behavior, with efficiencies around 90% and consistently high temperature uniformity across the bed. The pressure drop remains minimal, below 1 mbar, while particle size has a strong influence: larger particles reduce pressure drop, whereas smaller ones enhance thermal performance. Nevertheless, under the tested operating conditions, the discharge temperature exhibits a decreasing profile. Overall, this study demonstrates the potential of radial-flow packed bed concepts, while also showing that certain coaxial layering configurations can reduce pressure drop by about 30% without compromising thermal performance, maintaining efficiencies near 90%. • A novel air-based radial flow double-layered packed bed prototype is experimentally tested up to 600 °C • Several layer configurations and two particle sizes are tested • Thermocline development is monitored using 50 embedded temperature sensors in various positions along the bed • Repeatability tests show reproducible results with limited pressure drops and thermal efficiency near 90% • More than 30% pressure drop reduction is achieved by using two particle layers