飞轮储能热管理研究现状分析

Analysis on Research Status of Thermal Management of Flywheel Energy Storage System

飞轮储能可广泛应用于不间断电源、可再生能源并网、电力调峰调频、轨道交通和航空航天等领域。在真空环境下,电机及电磁轴承的散热问题关系到飞轮储能系统是否能够安全运行,是飞轮储能技术发展中亟待解决的关键科学技术问题,针对飞轮储能系统热管理的研究具有重要意义。飞轮储能系统发热主要由电机和电磁轴承引起,电机发热主要来自定子铁心铁损、绕组铜损及转子涡流损耗,电磁轴承发热主要由铁损和铜损构成。转子涡流损耗的分析是准确预测飞轮储能系统发热的基础。电机定子冷却手段主要有风冷、水冷、油冷、热管冷却以及相变冷却等,电机转子冷却手段主要有填充惰性气体增强对流换热、轴孔内油冷、扩展表面强化辐射换热等。目前高速飞轮储能系统采用的轴承主要有电磁轴承和高温超导磁悬浮轴承,传统电磁轴承的主要冷却方式是水冷,高温超导磁悬浮轴承的主要冷却方式是填充低压氦气。系统转子散热是飞轮储能系统热管理的难点,在转子散热技术方案设计中,需要考虑冷却流体挥发、密封和腐蚀问题,以及高黏度冷却流体随转子转动过程中的发热和动能损失问题。转子散热可行的解决方案主要有填充低温惰性气体以强化转子对流换热、电机低损耗设计以消除高频激波以及真空油冷等。

Flywheel energy storage can be widely used in the fields of uninterrupted power supply,renewable energy generation,peak shaving and frequency modulation of power system,rail transit and aerospace.In vacuum environment,the thermal dissipation of motor and electromagnetic bearing affects the safe operation of fly-wheel energy storage system,so it is a key problem of science and technology to be solved urgently in the development of flywheel energy storage technology,and the research on the thermal management of flywheel energy storage system is of great significance.The heating of flywheel energy storage system is mainly caused by the motor and the electromagnetic bearing.The heating of the motor mainly comes from the iron loss of stator core,the copper loss of winding and the eddy current loss of rotor.The heating of the electromagnetic bearing is mainly resulted by iron loss and copper loss.The analysis on eddy current loss of rotor is the ba-sis for accurately predicting the heating of flywheel energy storage system.The cooling methods for motor sta-tor mainly include air cooling,water cooling,oil cooling,heat pipe cooling and phase change cooling,while the cooling methods for motor rotor mainly include filling inert gas to enhance convective heat transfer,the oil cooling in shaft hole and the extended surface to enhance radiation heat transfer.At present,the bearings used in high-speed flywheel energy storage system mainly include electromagnetic bearing and high-temperature superconducting magnetic bearing.Water cooling is mainly adopted for traditional electromagnetic bearing,while filling low-pressure helium is adopted for high-temperature superconducting magnetic bearing.The thermal dis-sipation of system rotor is the difficulty of the thermal management of flywheel energy storage system.In the thermal dissipation design of rotor,it is necessary to consider the volatilization,sealing and corrosion problems of cooling fluids as well as the heating and kinetic energy loss problems of high viscosity cooling fluids as the rotor rotates.The feasible solutions for the thermal dissipation of rotor mainly include filling low-tempera-ture inert gas to enhance the convective heat transfer of rotor,the low-loss design of motor to eliminate high frequency shock wave and the vacuum oil cooling.