The ability of large-grain (RE)Ba2Cu3O7−δ ((RE)BCO; RE = rare earth) bulk superconductors to trap magnetic fields is determined by their critical current. With high trapped fields, however, bulk samples are subject to a relatively large Lorentz force, and their performance is limited primarily by their tensile strength. Consequently, sample reinforcement is the key to performance improvement in these technologically important materials. In this work, we report a trapped field of 17.6 T, the largest reported to date, in a stack of two silver-doped GdBCO superconducting bulk samples, each 25 mm in diameter, fabricated by top-seeded melt growth and reinforced with shrink-fit stainless steel. This sample preparation technique has the advantage of being relatively straightforward and inexpensive to implement, and offers the prospect of easy access to portable, high magnetic fields without any requirement for a sustaining current source.

https://iopscience.iop.org/article/10.1088/0953-2048/27/8/082001/pdf

A trapped field of 17.6 T in melt-processed, bulk Gd-Ba-Cu-O reinforced with shrink-fit steel

The deployment of energy storage systems (ESSs) is a significant avenue for maximising the energy efficiency of a distribution network, and overall network performance can be enhanced by their optimal placement, sizing, and operation. An optimally sized and placed ESS can facilitate peak energy demand fulfilment, enhance the benefits from the integration of renewables and distributed energy sources, aid power quality management, and reduce distribution network expansion costs. This paper provides an overview of optimal ESS placement, sizing, and operation. It considers a range of grid scenarios, targeted performance objectives, applied strategies, ESS types, and advantages and limitations of the proposed systems and approaches. While batteries are widely used as ESSs in various applications, the detailed comparative analysis of ESS technical characteristics suggests that flywheel energy storage (FES) also warrants consideration in some distribution network scenarios. This research provides recommendations for related requirements or procedures, appropriate ESS selection, smart ESS charging and discharging, ESS sizing, placement and operation, and power quality issues. Furthermore, this study identifies future research opportunities in relation to challenges for optimal ESS placement planning, development and implementation issues, optimisation techniques, social impacts, and energy security.

/pdf/overview-of-energy-storage-systems-in-distribution-networks-4cp0cljxir.pdf

Overview of energy storage systems in distribution networks: Placement, sizing, operation, and power quality

https://cyberleninka.org/article/n/818074.pdf

Recent advances in iron-based superconductors toward applications

Energy storage systems (ESSs) play a very important role in recent years. Flywheel is one of the oldest storage energy devices and it has several benefits. Flywheel Energy Storage System (FESS) can be applied from very small micro-satellites to huge power networks. A comprehensive review of FESS for hybrid vehicle, railway, wind power system, hybrid power generation system, power network, marine, space and other applications are presented in this paper. There are three main devices in FESS, including machine, bearing, and Power Electronic Interface (PEI). Furthermore, advantages and disadvantages all of them have been presented. In addition a brief review of new and conventional power electronic converters used in FESS, have been discussed. Finally, practical ways to develop this technology in the future are presented.

A comprehensive review of Flywheel Energy Storage System technology

Electric vehicles (EVs) have recently been significantly developed in terms of both performance and drive range. There already are various models commercially available, and the number of EVs on road increases rapidly. Although most existing EVs are charged by electric cables, companies like Tesla, BMW and Nissan have started to develop wireless charged EVs that don’t require bulky cables. Rather than physical cable connection, the wireless (inductive) link effectively avoids sparking over plugging/unplugging. Furthermore, wireless charging opens new possibilities for dynamic charging – charging while driving. Once realised, EVs will no longer be limited by their electric drive range and the requirement for battery capacity will be greatly reduced. This has been prioritised and promoted worldwide, particularly in UK, Germany and Korea. This paper presents a thorough literature review on the wireless charging technology for EVs. The key technical components of wireless charging are summarised and compared, such as compensation topologies, coil design and communication. To enhance the charging power, an innovative approach towards the use of superconducting material in coil designs is investigated and their potential impact on wireless charging is discussed. In addition, health and safety concerns about wireless charging are addressed, as well as their relevant standards. Economically, the costs of a wide range of wireless charging systems has also been summarised and compared.

/pdf/a-critical-review-on-wireless-charging-for-electric-vehicles-k5zdoa0gkx.pdf

A critical review on wireless charging for electric vehicles

It is well known that the efficiency of a wireless power transfer (WPT) system depends on the resistance of the transmitting and receiving coils, especially for the case of low frequency. Since the ac loss of high temperature superconductors (HTS) is much lower than that of conventional conductors, using high temperature superconductors for WPT system is a good way to increase power transfer efficiency. Here, several kinds of WPT experiments were designed and conducted by use of HTS and conventional conductor (copper) coils, respectively. The results are presented and analyzed. It is shown that the behavior of HTS WPT system is similar to that of a conventional WPT system, but the efficiency of WPT system is much higher by use of HTS coils and HTS coil is more suitable for being as a transmitting coil than as a receiving one.

Wireless Power Transfer Using High Temperature Superconducting Pancake Coils

High temperature superconducting (HTS) generator was promising in the wind power applications for its advantages in the weight, size and thermal stability against load fluctuations, especially in the “direct-driven” design. A 100 kW generator was proposed for the demonstration of the feasibility of using HTS in 10 MW wind turbine generators. The electromagnetic design and optimization of the rotor were done using finite element method (FEM). The excitation coil of the rotor was designed considering variable working conditions. According to the numerical results, a number of suggestions in the design and winding techniques of the superconducting rotor were proposed.

Design of a High Temperature Superconducting Generator for Wind Power Applications

Superconducting magnetic energy storage (SMES) system is an equipment that can help improving the stability of a power system. Location of SMES in multi-nodes power network plays a significant role for the stability improvement level. In this paper, based on the quantitative voltage stability index, genetic algorithm (GA) is used for optimization of the SMES location. The voltage stability index is used as the fitness function in GA. The GA mathematic parameters and optimal flow chart are presented. The proposed algorithm is tested in an IEEE 14-bus system. Simulation results show that the SMES is settled on the best site through GA optimization during the period of the voltage stability fault.

Optimal Location of SMES for Improving Power System Voltage Stability

High temperature superconducting (HTS) coils are key parts of many AC applications, such as generators, superconducting magnetic energy storage and transformers. AC loss reduction in HTS coils is essential for the commercialization of these HTS devices. Magnetic material is generally used as the flux diverter in an effort to reduce the AC loss in HTS coils. To achieve the greatest reduction in the AC loss of the coils, the flux diverter should be made of a material with low loss and high saturated magnetic density, and the optimization of the geometric size and location of the flux diverter is required. In this paper, we chose Ni-alloy as the flux diverter, which can be processed into a specific shape and size. The influence of the shape and location of the flux diverter on the AC loss characteristics of stacked (RE)BCO tapes is investigated by use of a finite element method. Taking both the AC loss of the (RE)BCO coils and the ferromagnetic loss of the flux diverter into account, the optimal geometry of the flux diverter is obtained. It is found that when the applied current is at half the value of the critical current, the total loss of the HTS stack with the optimal flux diverter is only 18% of the original loss of the HTS stack without the flux diverter. Besides, the effect of the flux diverter on the critical current of the (RE)BCO stack is investigated.

https://iopscience.iop.org/article/10.1088/1361-6668/aa9362/pdf

Numerical study on AC loss reduction of stacked HTS tapes by optimal design of flux diverter

Flywheel energy system (FES) is a non-pollution energy storage system which uses high-speed rotation flywheel to store energy. As high temperature superconducting (HTS) bearings have very low friction and self-stability characteristic, they are applied to FES increasingly. In this paper, for the optimal structure of permanent magnet rotor, 3 topologies were presented and their magnetic field characteristics were analyzed. For effective cooling of YBCO bulks, a thermal model of the superconductor magnet stator using alumina shims was set up and its temperature distribution was analyzed. The result shows that the structure of the stator in which alumina shims were put between the neighboring YBCO bulks is better than that without alumina shims, and the temperature of YBCO bulks in the structure is lower. Then a radial-type HTS bearing prototype with outer diameter of 200 mm, inner diameter of 40 mm and height of 120 mm was built. The axial force, the axial stiffness and the levitation characteristics of the device were measured and analyzed in field cooling and zero-field cooling respectively.

Guomin Zhang

Papers

Wireless Power Transfer Using High Temperature Superconducting Pancake Coils

Design of a High Temperature Superconducting Generator for Wind Power Applications

Optimal Location of SMES for Improving Power System Voltage Stability

Numerical study on AC loss reduction of stacked HTS tapes by optimal design of flux diverter

Analyses and Tests of HTS Bearing For Flywheel Energy System