Modeling Thermal Energy Storage Utilizing Air As Heat Transfer Fluid and Alumina As Storage Material

Thermal energy storage is a critical component of concentrated solar power plants to increase the capacity factor and drive down the cost of electricity. One storage option is a packed bed of a solid storage material with a gaseous heat transfer fluid. Alumina is considered a strong candidate as the storage material in the packed bed due to a high heat capacity and thermal stability, making it well suited for high temperature thermal energy storage. A simplified, one-equation model is presented with air as heat transfer fluid flowing through a packed bed of α-alumina beads. The thermal properties are averaged in the one-equation model, and all of these properties are calculated as a function of temperature. In addition to the thermal model, the pressure drop is also calculated. The modeling approach is compared to experimental data at multiple flow rates during storage and recovery. For this air and alumina system, the one-equation approach works well in describing the thermal front as it moves through the packed bed. With this validated approach, a designer could quickly study the key parameters (e.g. bed diameter, bead size, materials) associated with the storage for a user’s specific conditions (e.g. maximum temperature, flow rates).