基于液氮动力循环的无间断电源研究探索

The Uninterruptible Power Suppply (UPS) generally utilizes chemical battery as the electricity storage unit at present, which comes up with some drawbacks, such as low energy density, short life time, high-cost maintenance, hazardous effect to the enviroment, etc.. An UPS system based on supercapacitor and liquid nitrogen power cycle hybridization was first introduced in this research proposal. And it will mainly investigate the liquid nitrogen power cycle. This liquid nitrogen cycle combines an open Rankine cycle and a closed Brayton cycle, which could recover the cold energy of the liquid energy. Moreover, a thermal storage unit is also engaged, which preheats the nitrogen before entering the expander to generate power.The proposed UPS system may reveal merits as follows: fast reaction when outage occurs, high energy density (both storage and discharging processes), environmentally benign technique, long life time, easy maintenance, easy inspection of the remained energy and so on. The project will carry out fundamental research in depth including: the systematic thermodynamic theory, fluid flow and heat transfer characteristics under high-pressure and low-temperature conditions, phase change material property, thermal energy storage and heat transfer mechanism, to develop and optimize high pressure ratio expander, etc.. It will build up the first demonstration of an UPS based on supercapacitor and liquid nitrogen cycle hybridization system. It could provide theoretical principle and verification for the UPS design based on physical energy storage technology.

当前无间断电源（UPS）的储能单元以化学蓄电池为主，能量密度低、寿命短、维护费用高、污染环境等。本研究提出一种新型的基于超级电容与液氮动力耦合的无间断电源系统，并重点研究液氮动力循环系统，它包括一个开式郎肯（Rankine）循环和一个闭口布雷顿（Brayton）循环，二者相耦合，从而充分回收利用液氮冷能，并有蓄热换热器为膨胀机前的氮气提供预热。该无间断电源系统具有反应迅速、能量密度高（储存、输出）、环境友好、寿命长、易维护、剩余电量易检测等优点。本项目将深入研究该系统的基础理论、总体热力学性能、高压低温流体的流动与传热特性、相变蓄热材料特性、蓄热换热机理以及高压比膨胀机的设计优化等科学问题，同时建立基于超级电容与液氮动力系统耦合的无间断电源系统原理试验台，为基于新型物理储能的无间断电源的设计提供理论基础和原理验证。

当前无间断电源（UPS）的储能单元以化学蓄电池为主，能量密度低、寿命短、维护费用高等，研发新型的无间断电源系统，将可以作为蓄电池的一种有效的补充。本项目主要针对液氮动力循环开展理论分析与实验研究工作。首先建立了超级电容与液氮动力耦合的无间断电压系统的模型，研究得到了动态工作特性；进一步研发了一种新型的多级单阀往复式膨胀机，并开展了详细的实验研究和理论分析，研究表明该膨胀机具有工作压力高、效率高的有点，通过对气缸内部流场的分析，得到了该膨胀机的流动损失机理；研究得到了蓄热材料的热物性，并实验研究了蓄热换热单元的工作特性；开展了低温换热器的研究，完成了换热器的参数敏感性分析和结构设计；开展了MW级先进压缩空气储能系统的实验研究，并以此为基础，进一步开展了分布式供能与储能系统的研究，获得了分布式供能与储能系统的热力学特性、动态性能及其节能效果。通过本研究，验证了该新型无间断电压的可行性，为进一步的混合储能系统的应用提供理论和实验验证基础。