Thermodynamic analysis and optimisation of a combined liquid air and pumped thermal energy storage cycle
Thermodynamic analysis and optimisation of a combined liquid air and pumped thermal energy storage cycle
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DOI：
10.1016/j.est.2018.04.016
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发表时间：
2018-08
影响因子：
9.4
通讯作者：
Pau Farres-Antunez;Haobai Xue;Alexander J. White
中科院分区：
文献类型：
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作者：
Pau Farres-Antunez;Haobai Xue;Alexander J. White
泵送储能（PTES）和液态空气储能（LAES）是两种以热（火用）形式储存能量的大型储能技术。这是通过在绝热储罐之间操作机械驱动的热力学循环来实现的。这两种技术都不受适用于抽水蓄能和大多数压缩空气储存的地理限制。本文介绍了一种新型的，组合系统，其中PTES作为一个顶部循环和LAES作为一个底部循环。基本的优点是，两个单独的循环所需的冷的热储存器被在它们之间起作用的单个热交换器所取代，从而节省了每单位能量存储的大量存储介质。为了达到低温，PTES循环使用氦气作为工作流体，而LAES循环使用超临界空气（约150 bar），其被充分冷却以在膨胀时完全液化，从而避免剩余蒸汽的再循环。的联合循环的基线配置的热力学研究，并与单独的系统的结果进行了比较。这些表明新循环具有与单独系统相似的往返效率，同时提供显着更大的能量密度。此外，三个适应的基本情况下联合循环的建议和优化。这些改进中最好的一种实现了热力学效率提高约10个百分点（从60%到70%），因此在能量密度和效率方面都大大超过了单个循环。
Pumped thermal energy storage (PTES) and liquid air energy storage (LAES) are two large-scale electricity storage technologies that store energy in the form of thermal exergy. This is achieved by operating mechanically-driven thermodynamic cycles between thermally insulated storage tanks. Both technologies are free from geographic restrictions that apply to pumped hydro and most compressed air storage. The present paper describes a novel, combined system in which PTES operates as a topping cycle and LAES as a bottoming cycle. The fundamental advantage is that the cold thermal reservoirs that would be required by the two separate cycles are replaced by a single heat exchanger that acts between them, thereby saving significant amounts of storage media per unit of energy stored. In order to reach cryogenic temperatures, the PTES cycle employs helium as the working fluid, while the LAES cycle uses supercritical air (at around 150 bar) which is cooled sufficiently to be fully liquefied upon expansion, thus avoiding recirculation of leftover vapour. A thermodynamic study of a baseline configuration of the combined cycle is presented and results are compared with those of the separate systems. These indicate that the new cycle has a similar round-trip efficiency to that of the separate systems while providing a significantly larger energy density. Furthermore, three adaptations of the base-case combined cycle are proposed and optimised. The best of these adaptations achieves an increase in thermodynamic efficiency of about 10 percent points (from 60% to 70%), therefore significantly exceeding the individual cycles in both energy density and efficiency.