Experimental validation of steel slag as thermal energy storage material in a 400 kWh_t prototype

Packed bed systems have been proposed in the last years as a promising thermal energy storage alternative to reduce the levelized cost of electricity in concentrated solar power plants. However, although the interest of the scientific and industrial community in this thermal energy storage alternative is increasing, there is still a lack of a clear technology viability demonstration at a relevant scale. This is one of the main barriers this technology is facing to reach a complete deployment at commercial level. Aiming to take one step forward in the state of the art of the technology, in this work, a 400 kWh_t packed bed system has been tested in the Air Test Loop facility available at CIC Energigune with a double objective: the validation of the steel slag as low-cost and high-performing filler material on one hand, and to investigate the performance of the packed bed technology using air as heat transfer fluid under different charge, discharge and idle operational conditions, on the other hand. Furthermore, the experimental results have been validated with a computational fluid dynamics model that, in further steps of this work, will be used to investigate the techno-economic viability of the slag-based packed bed solution at a real industrial scale.