Nowadays, global warming is intensifying more and more and fossil fuels are running out all over the world, which leads to increasing numbers of efforts for protecting the environments against green house effects and for using natural energy.
In the production of electric power using natural energy, electrical power fluctuation occurs due to the natural conditions such as luminous intensity, wind speed, tidal current, etc. Therefore, it is necessary to make up for electrical power fluctuation for stabilizing the power supply. Compensation for electrical power fluctuation can be carried out by secondary batteries or a flywheel energy storage system (FESS). Since the FESS using the SMB has longer life time than secondary batteries, it has already been applied in several countries.
The important problems of the FESS are to heighten load capacity, to decrease loss and to raise stability. These problems are ascribable to the improvement of the performance of SMB.
A number of basic experiments were performed to design the SMB and to improve its performance, and the FESSs with SMBs of different load capacities and structures were developed. On the other hand, numerical simulations on SMB were conducted by MATLAB, FORTRAN and COMSOL Multiphysics.
Some researchers presented a way to increase the levitation force using opposite magnetization effect through experiments and simulations, and obtained 170.14N in maximum levitation force. However, they failed to intend optimization on it.
Jo Ju Hak, a researcher at the Faculty of Physical Engineering, has simulated a three surface levitation-superconducting magnetic bearing (TSL-SMB) in two-dimensional axisymmetric system using H-formulation and Taguchi method.
The simulation was conducted by field cooling (FC) method. The effects of geometric parameters on levitation force in TSL-SMB were considered using Analysis of Variance (ANOVA). He concluded that in the optimized TSL-SMB structure the effect of concentric ring PMs with opposite polarization did not play a decisive role. Therefore, he presented four-surface levitation-superconducting magnetic bearing (FSL-SMB) as advanced multi-surface levitation system to improve the performance of SMB.
The simulation results in the FSL-SMB system showed that the gap between the stator and the rotor and levitation force per permanent magnet volume might be increased more than those of TSL-SMB system in the condition of same load capacity.
For more information, you can refer to his paper “Simulation on modified multi-surface levitation structure of superconducting magnetic bearing for flywheel energy storage system by H-formulation and Taguchi method” in “Physica C: Superconductivity and its applications” (SCI).
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