Abstract:

Large-scale, long-duration energy storage technologies are vital for achieving the dual-carbon goals. Among them, Liquid Air Energy Storage (LAES) has received significant attention due to its high energy density, geographical flexibility, long service life, and environmental friendliness. As the core cold storage unit in LAES, the thermal performance of the packed bed directly impacts the cycle efficiency and economic viability of the system. Traditional cold storage packed beds use an axial-flow design, where the heat transfer fluid enters from the bottom and exits from the top after exchanging heat with the storage material. This design suffers from high pressure drop, large pump power consumption, and severe velocity fluctuations, limiting its overall performance. To overcome these limitations, a novel design of radial-flow cold packed bed is proposed, in which the cooling fluid enters via a central inlet at the bottom, flows radially through the storage material, and exits centrally after heat exchange. Numerical simulations were conducted to analyze the flow velocity, interstitial convective heat transfer coefficient, pressure drop, and exergy efficiency of the radial-flow packed bed under different working fluid pressures, and to compare these results with those of the axial-flow configuration. Results indicate that under a storage capacity of 150 MWh and a fluid pressure of 0.1 MPa, the radial-flow packed bed experiences a pressure drop of only 2 kPa during charge/discharge, markedly lower than the 82.8 kPa observed in the axial-flow bed. The exergy efficiency of the radial-flow system reaches 87.7%, significantly outperforming the 59.8% efficiency of the axial-flow configuration. When the working pressure increases to 0.8 MPa, the pressure drop during the charge/discharge process decreases significantly in both radial- and axial-flow beds. The influence of pumping power on exergy efficiency becomes negligible, and the axial-flow bed achieves a higher exergy efficiency of 93.1%. Therefore, the radial-flow cold storage packed bed is more suitable for low-pressure charge/discharge operating conditions. This study offers theoretical insights and design references for structural optimization of cold packed beds, highlighting the strong potential of radial-flow designs in practical energy storage applications.

Key words: liquid air energy storage, cold storage bed, radial flow, axial flow