Experimental and numerical analysis of a packed-bed thermal energy storage system designed to recover high temperature waste heat: an industrial scale up

An industrial-scale air-ceramic horizontal packed-bed thermal energy storage (Eco-Stock®) has been designed and built by Eco-Tech Ceram and tested during an experimental campaign of 500h. The goal is to provide experimental data and analysis of a horizontal and containerized packed bed TES at high temperature, with performance indicators specific to waste heat recovery. A single charge-discharge at 525°C and 3 cycles at 500°C were carried out (300 kWTh for charge, 350 kWTh for discharge). The unit was able to store up to 1.9 MWhTh in a TES system (1.7 × 1.7 × 3.08 m3) composed by 16-ton of bauxite ceramic media. The packed bed was able to valorize up to 90% of the heat source, which demonstrates the system ability to recover waste heat up to 525°C at industrial scale. No channeling effect and moderate radial thermal gradient were detected, even though the tank had a horizontal geometry. The plug and play TES presents a non-negligible part of its energy stored in the insulant, which can be recovered during discharge. To take into account such phenomenon, a one-dimension 3 temperature model is proposed. The model fitted well with experimental results, with a root mean standard deviation of the model below 20°C for the temperature profiles.