Multilayer Packed Bed Based Latent & Sensible Heat Storage for Liquid Air Energy Storage Efficiency Enhancement

Energy storage technologies has a vital role to play in future renewable energy dominated power grids. Liquid Air Energy Storage (LAES), as one of such storage technologies, has attracted attention in recent years. Such a technology has an electrical-to-electrical round trip efficiency of ~50-60% if thermal integration is implemented particularly when a high-grade cold energy store (HGCS) is employed to capture and store cold energy during discharging for reuse charging process. Packed beds have been widely studied and demonstrated as the HGCS for the cryogenic energy storage due to low costs, long life-span and high safety. Most of these studied packed bed based HGCS is usually filled with a single sensible heat storage material, which gives a low energy density and unstable outlet temperature. Low-temperature encapsulated phase change material (PCM) has also been studied to address the two issues, which incurs a high-cost. This work examines the use of combined PCMs with sensible heat materials in one packed bed (as shown in Fig. 1). We shall show that such an approach is more cost-effective, but yet provides an enhanced stability of the outlet temperature as well as the overall performance of HGCS. Our particular focus in on the use of multilayer PCMs-sensible heat materials packed bed, investigating how this combination would affect the energy density, temperature profile, outlet temperature of the HGCS as well as the performance of the LAES system (e.g. roundtrip efficiency and liquid yield). We also optimized the number of the PCM layers in the packed bed based HGCS, considering both complexity and cost factors.