Experimental and numerical study of an air solid thermocline thermal energy storage system operating at high temperature

One-single tank for thermal energy storage works by creating a thermocline between a cold and a hot zone. This type of storage system can be up 35% cheaper than two-tank storage with molten salts. ALTAYR is a laboratory-scale prototype rock-air packed-bed tank capable of storing energy by forming a thermocline. It is available at the Thermal Storage and Solar Fuels Unit of CIEMAT-PSA and allows experimental tests to study the performance of a thermocline system in a wide range of operational conditions. The facility is presented in this work as well as some results of experimental tests that explore its performance. Moreover, an initiatory numerical model developed to better understand the technology and optimize the system design is presented. The model has been validated with the experimental results achieving good agreement. Further work is currently on going and it is devoted to the model refinement in order to be employed to design reliable and cost effective thermocline tanks.