Thermal Packaging of High Temperature Superconductor Bulk for Superconducting Flywheel Energy Storage

2013 ◽  
Vol 23 (3) ◽  
pp. 5701104-5701104 ◽  
Author(s):  
Taekyung Ki ◽  
Sangkwon Jeong ◽  
Young Hee Han ◽  
Byung Jun Park
Author(s):  
Kangwon Lee ◽  
Bongsu Kim ◽  
Junseok Ko ◽  
Sangkwon Jeong ◽  
Seung S. Lee

A micro flywheel energy storage system has been developed using a high temperature superconductor bearing. In the previous paper, the micro flywheel was fabricated and successfully rotated 38,000 rpm in the vacuum chamber. However, there are the large drag torque because of the non-axisymmetric magnetic flux of the motor/bearing magnet and the eddy current loss in the planar stator, which makes short spin-down time as 20~30 sec and coefficient of friction as 0.15. This paper presents the design, fabrication and electromagnetic analysis of the flywheel to reduce the large drag torque. The advanced flywheel is made up of motor and bearing magnet, aluminium disk, and magnetic screening disk. The maximum rotational speed is up to 51,000 rpm and furthermore the spin-down time is about 3 hr 20 min in the vacuum condition. From these results, the coefficient of friction is calculated as 0.001~0.002.


Author(s):  
Bongsu Kim ◽  
Junseok Ko ◽  
Sangkwon Jeong ◽  
Seung S. Lee

A micro flywheel energy storage system with a high-temperature superconductor (HTS) bearing which is characterized by the diamagnetic effect and the flux pinning effect has been developed. The micro flywheel is made up of circumferential magnets for a motor/generator as well as concentric magnets for an HTS bearing and they are fitted into a 34-mm diameter and 3-mm thick aluminum disk. Mass and moment of inertia of the micro flywheel are 12.75 g and 1.84E−6 kgm2, respectively. For simplicity and miniaturization of the whole system, the micro flywheel directly takes torque from a planar stator, which consists of an axial flux type brushless DC motor/generator. The micro flywheel successfully rotated up to 38,000 rpm in vacuum condition as it is levitating above the stator with a gap of about 1 mm. However, there are some eddy current losses in the stator and non-axisymmetry in magnetic field causing large drag torque. In order to solve these problems, an improved magnet array in the flywheel including a Halbach array is proposed and 3D simulations have been conducted.


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