• Progress in Superconductivity
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• v.13 no.1
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• pp.52-57
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• 2011

A superconductor flywheel energy storage system (SFES) is an electro-mechanical battery which transforms electrical energy into mechanical energy for storage, and vice versa. The 35 kWh class SFES is composed of a main frame, superconductor bearings, electro-magnetic dampers, a motor/generator, and a composite flywheel. The energy storing capacity of the SFES can be limited by the operational speed range of the system. The operational speed range is limited by many factors, especially the resonant frequency of the main frame and flywheel. In this study, a steel frame has been designed and constructed for a 35 kWh class SFES. All the main parts, their housings, and the flywheel are aligned and assembled on to the main frame. While in operation, the flywheel excites the main frame, as well as all the parts assembled to it, causing the system to vibrate at the rotating speed. If the main frame is excited at its resonant frequency, the system will resonate, which may lead to unstable levitation at the superconductor bearings and electro-magnetic dampers. The main frame for the 35 kWh class SFES has been designed and constructed to improve stiffness for the stable operation of the system within the operational speed range.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 1999.02a
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• pp.121-124
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• 1999

A horizontal axle-type superconductor flywheel energy storage system has many great features such as extensibility and stability compared to the traditional vertical axle-type flywheel systems. In this paper, a prototype flywheel device with a horizontal axle is presented briefly, and the hybrid construction as an essential supplement in superconductor journal bearing design against the levitation drift is proposed.

• Progress in Superconductivity and Cryogenics
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• v.3 no.1
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• pp.50-55
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• 2001

A new type of flywheel energy storage system that has a horizontal axle with High $T_c$, superconductor bearings using Y123 single-domained crystals was developed.The dynamic Properties, stiffness and damping of the high $T_c$, superconductor radial bearings were experimentally estimated using a imbalance excitation method. The imbalance excitation method applied to this rotor- bearing system identified the identified stiffness and damping of the high temperature superconductor beatings to be 2.8 $3.3 {\times} 10^5 N/m and 775 204$ Nsec/m respectively.

• Progress in Superconductivity
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• v.14 no.1
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• pp.60-65
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• 2012

A superconductor flywheel energy storage system (SFES) is an electro-mechanical battery which transforms electrical energy into mechanical energy for storage, and vice versa. A 35 kWh class SFES module was designed and constructed as part of a 100kWh/1MW class SFES composed of three 35 kWh class SFES modules. The 35 kWh class SFES is composed of a main frame, superconductor bearings, a composite flywheel, a motor/generator, electro-magnetic bearings, and a permanent magnet bearing. The high energy density composite flywheel is levitated by the permanent magnet bearing and superconductor bearings, while being spun by the motor/generator, and the electro-magnetic bearings are activated while passing through the critical speeds. Each of the main components was designed to provide maximum performance within a space-limited compact frame. The 35 kWh class SFES is designed to store 35 kWh, with a 350 kW charge/discharge capacity, in the 8,000 ~ 12,000 rpm operational speed range.

• Progress in Superconductivity
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• v.10 no.1
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• pp.55-59
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• 2008

A Superconductor Flywheel Energy Storage System(SFES) mainly consists of a pair of non-contacting High Temperature Superconductor(HTS) bearings that provide very low frictional losses, a composite flywheel with high energy storage density. The HTS bearings, which offer dynamic stability without active control, are the key technology that distinguishes the SFES from other flywheel energy storage devices, and great effort is being put into developing this technology. The Superconductor Journal Bearing(SJB) mainly consists of HTS bulks and a stator, which holds the HTS bulks and also acts as a cold head. Static properties of HTS bearings provide data to solve problems which may occur easily in a running system. Since stiffness to counter vibration is the main parameter in designing an HTS bearing system, we investigate SJB magnetic force through static properties between the Permanent Magnet(PM) and HTS. We measure stiffness in static condition and the results are used to determine the optimal number of HTS bulks for a 100kWh SFES.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.9
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• pp.1750-1756
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• 2009

In this paper, 5 kWh class Superconductor Flywheel Energy Storage System (SFES) was constructed including motor/generator, superconductor magnetic bearing(SMB), composite rotor and electromagnetic damper(EMD) system. High speed rotation test was performed after levitating flywheel rotor only using EMD without SMB. the PD controller of EMD was designed. the control system is constructed using xPC which is real time digital control system. the results of high speed rotation test showed that proposed EMD system have sufficient damping in cylindrical mode and conical mode, and vibration of wheel was suppressed below 10 ${\mu}m$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.10
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• pp.1775-1781
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• 2007

In this paper, the rotational loss of the superconductor flywheel energy storage system (SFES) by motor/generator stator core was assessed. To do this, the vertical axial type SFES with journal type superconductor bearing was manufactured. To quantitatively assess the rotational loss by the stator core, the rotational losses by superconductor bearing and the degree of a vacuum were measured. In case of variation of the inner radius and outer radius of the stator core, the rotational losses were measured. From the experimental results, It is confirmed that the rotational loss can be reduced by means of the optimal stator core design.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.791-792
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• 2009

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1197-1198
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• 2011

• Progress in Superconductivity
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• v.13 no.1
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• pp.40-46
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• 2011

A superconductor flywheel energy storage system (SFES) is an electro-mechanical battery which transforms electrical energy into mechanical energy for storage, and vice versa. A 10 kWh class flywheel energy storage system (FESS) has been developed to evaluate the feasibility of a 35 kWh class SFES with a flywheel $I_p/I_t$ ratio larger than 1. The 10 kWh class FESS is composed of a main frame, a composite flywheel, active magnetic dampers (AMDs), a permanent magnet bearing, and a motor/generator. The flywheel of the FESS rotates at a very high speed to store energy, while being levitated by a permanent magnetic bearing and a pair of thrust AMDs. The 10 kWh class flywheel is mainly composed of a composite rotor assembly, where most of the energy is stored, two radial and two thrust AMD rotors, which dissipate vibration at critical speeds, a permanent magnet rotor, which supports most of the flywheel weight, a motor rotor, which spins the flywheel, and a central hollow shaft, where the parts are assembled and aligned to. The stators of each of the main components are assembled on to housings, which are assembled and aligned to the main frame. Many factors have been considered while designing each part of the flywheel, stator and frame. In this study, a 10 kWh class flywheel energy storage system has been designed and constructed for test operation.