Liquid air energy storage (LAES) is increasingly popular for peak-load shifting of power grids, which includes air liquefaction at off-peak hours and power generation at peak hours. The standalone LAES system does not rely on external cold and heat sources, and hence is more favorable for applications. In the standalone LAES system, heat storage in the air liquefaction process and cold storage in the power generation process play a key role on the system performance. The previous studies often chose propane/methanol as cold storage materials, and thermal oils as heat storage materials, which show a relatively higher system performance. However, propane, methanol and thermal oils are flammable, have a high capital cost and require strict safety measures, which are unfavorable for some industrial applications. To address this issue, we propose a novel standalone LAES system with pebbles/rocks as both cold and heat storage materials in packed beds. Such stores have a low capital cost and a high chemical stability and have not been studied in detail before. The dynamic effect of packed beds on the proposed LAES system is investigated from start-up to stable operation for the first time. Our simulation results show that it takes ~10 days for the system to reach a stable operation from start-up mainly due to the cold accumulation in the packed bed, and the average liquid air yield increases from 0.23 at the start-up to 0.56 in the stable operation. Besides, the proposed LAES system gives a round trip efficiency of ~42.8% and a combined heat and power efficiency of ~82.1%. These findings provide valuable information for industrial applications of the LAES technology.

液态空气储能（LAES）在电网调峰中越来越受欢迎，包括非高峰时段的空气液化和高峰时段的发电。独立的 LAES 系统不依赖外部冷热源，因此更适合应用。在独立的 LAES 系统中，空气液化过程中的蓄热和发电过程中的蓄冷对系统性能起着关键作用。以往的研究往往选择丙烷/甲醇作为蓄冷材料，导热油作为蓄热材料，表现出相对较高的系统性能。然而，丙烷、甲醇和导热油易燃，资金成本高，需要严格的安全措施，不利于某些工业应用。为了解决这个问题，我们提出了一种新颖的独立 LAES 系统，将鹅卵石/岩石作为填充床中的蓄冷和蓄热材料。此类存储具有较低的资本成本和较高的化学稳定性，之前尚未进行详细研究。首次研究了填充床对所提出的 LAES 系统从启动到稳定运行的动态影响。我们的模拟结果表明，系统从启动到稳定运行大约需要 10 天，主要是由于填充床中的冷积聚，平均液态空气产量从启动时的 0.23 增加到 0.56运行稳定。此外，所提出的 LAES 系统的往返效率约为 42.8%，热电联产效率约为 82.1%。这些发现为 LAES 技术的工业应用提供了有价值的信息。