A 45-m-long high-temperature superconducting (HTS) Maglev ring test line, named “Super-Maglev,” has been successfully developed in Chengdu, China, in February 2013, 12 years after the birth of the first man-loading HTS Maglev test vehicle. The Maglev vehicle (2.2 m in length, 1.1 m in width) is designed for one passenger with a levitation height of 10–20 mm; the permanent-magnet guideway (PMG) (45 m in length, 0.77 m of track gauge) is a racetrack shape with a curve radius of 6 m; the driving is accomplished by a linear induction motor with a maximum running speed of 50 km/h. The linear motor is composed of four submotors installed at one straight section in the middle of the double PMGs, and the total length is 3 m. This second-generation HTS Maglev vehicle system is highlighted by the cost-performance and the wireless multiparameter onboard monitoring function. The current same-level load capability has been achieved over a small-section low-cost PMG whose cross-sectional area is only 3000 mm
 2
. On the vehicle, parameters of levitation weight, levitation height, running speed, acceleration, lateral offset, online position, and total running distance of the vehicle are real-time monitored and displayed on the onboard tablet computer. The system component and test data are reported in detail in this paper.

A High-Temperature Superconducting Maglev Ring Test Line Developed in Chengdu, China

This paper presents a topical review of the current state of the art in modelling the magnetization of bulk superconductors, including both (RE)BCO (where RE?=?rare earth or Y) and MgB2 materials. Such modelling is a powerful tool to understand the physical mechanisms of their magnetization, to assist in interpretation of experimental results, and to predict the performance of practical bulk superconductor-based devices, which is particularly important as many superconducting applications head towards the commercialization stage of their development in the coming years. In addition to the analytical and numerical techniques currently used by researchers for modelling such materials, the commonly used practical techniques to magnetize bulk superconductors are summarized with a particular focus on pulsed field magnetization (PFM), which is promising as a compact, mobile and relatively inexpensive magnetizing technique. A number of numerical models developed to analyse the issues related to PFM and optimise the technique are described in detail, including understanding the dynamics of the magnetic flux penetration and the influence of material inhomogeneities, thermal properties, pulse duration, magnitude and shape, and the shape of the magnetization coil(s). The effect of externally applied magnetic fields in different configurations on the attenuation of the trapped field is also discussed. A number of novel and hybrid bulk superconductor structures are described, including improved thermal conductivity structures and ferromagnet?superconductor structures, which have been designed to overcome some of the issues related to bulk superconductors and their magnetization and enhance the intrinsic properties of bulk superconductors acting as trapped field magnets. Finally, the use of hollow bulk cylinders/tubes for shielding is analysed.

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Modelling of bulk superconductor magnetization

As a bellwether transportation mode, albeit with hot controversy, evacuated tube transport (ETT) can dramatically reduce air friction, and incorporating Maglev technology could also thoroughly eliminate wheel-rail friction. It is not difficult to imagine that incorporation of these two technologies could establish an innovative transportation system, with particular advantages in terms of high speed, safety, energy saving, and environmental protection. The integration of these two technologies has been a great challenge, however, due to the composite technology. To realize this revolutionary idea, we have successfully developed the first proof-of-principle prototype of a 45-m-long high-temperature superconducting Maglev evacuated tube transport (HTS Maglev-ETT) test system, called the “Super-Maglev,” based on the passive self-stable HTS Maglev conceived in our group in 2000. The system mainly consists of three parts: an HTS Maglev-vehicle-guideway coupling system with 1-t load capability at a levitation gap of 10 mm, a 45-m-long racetrack-type evacuated tube with a 2-m-diameter circular cross section pumped by a hybrid air extraction system, and a 3-m linear induction motor to provide sectional propulsion. The system can achieve a pressure as low as 2.9 kPa in the tube. Experiments show that air drag on the vehicle is greatly reduced at that low air pressure, and a maximum speed of 50 km/h was recorded on the 6-m-diameter test guideway. Theoretically, the reduction of the aerodynamic consumed power could reach as high as to 90% under 10 kPa. This “Super-Maglev” strongly demonstrates the feasibility and potential merits of the HTS Maglev-ETT transportation concept.

A High-Temperature Superconducting Maglev-Evacuated Tube Transport (HTS Maglev-ETT) Test System

There is universal agreement between the United Nations and governments from the richest to the poorest nations that humanity faces unprecedented global challenges relating to sustainable energy, clean water, low-emission transportation, coping with climate change and natural disasters, and reclaiming use of land. We have invited researchers from a range of eclectic research areas to provide a Roadmap of how superconducting technologies could address these major challenges confronting humanity.Superconductivity has, over the century since its discovery by Kamerlingh Onnes in 1911, promised to provide solutions to many challenges. So far, most superconducting technologies are esoteric systems that are used in laboratories and hospitals. Large science projects have long appreciated the ability of superconductivity to efficiently create high magnetic fields that are otherwise very costly to achieve with ordinary materials. The most successful applications outside of large science are high-field magnets for magnetic resonance imaging, laboratory magnetometers for mineral and materials characterization, filters for mobile communications, and magnetoencephalography for understanding the human brain.The stage is now set for superconductivity to make more general contributions. Humanity uses practically unthinkable amounts of energy to drive our modern way of life. Overall, global power usage has been predicted to almost double from 16.5 to 30?TW in the next four decades (2011 Equinox Summit: Energy 2030 http://wgsi.org/publications-resources).The economy with which electrons carry energy compels the continued quest for efficient superconducting power generation, energy storage, and power transmission. The growing global population requires new arable land and treatment of water, especially in remote areas, and superconductivity offers unique solutions to these problems. Exquisite detectors give warning of changes that are otherwise invisible. Prediction of climate and disasters will be helped by future supercomputer technologies that support huge amounts of data and sophisticated modeling, and with the aid of superconductivity these systems might not require the energy of a large city.We present different sections on applications that could address (or are addressing) a range of environmental issues. The Roadmap covers water purification, power distribution and storage, low-environmental impact transport, environmental sensing (particularly for the removal of unexploded munitions), monitoring the Earth?s magnetic fields for earthquakes and major solar activity, and, finally, developing a petaflop supercomputer that only requires 3% of the current supercomputer power provision while being 50 times faster.Access to fresh water. With only 2.5% of the water on Earth being fresh and climate change modeling forecasting that many areas will become drier, the ability to recycle water and achieve compact water recycling systems for sewage or ground water treatment is critical. The first section (by Nishijima) points to the potential of superconducting magnetic separation to enable water recycling and reuse.Energy. The Equinox Summit held in Waterloo Canada 2011?(2011 Equinox Summit: Energy 2030 http://wgsi.org/publications-resources) identified electricity use as humanity?s largest contributor to greenhouse gas emissions. Our appetite for electricity is growing faster than for any other form of energy. The communiqu? from the summit said ?Transforming the ways we generate, distribute and store electricity is among the most pressing challenges facing society today?. If we want to stabilize CO2 levels in our atmosphere at 550 parts per million, all of that growth needs to be met by non-carbon forms of energy? (2011 Equinox Summit: Energy 2030 http://wgsi.org/publications-resources). Superconducting technologies can provide the energy efficiencies to achieve, in the European Union alone, 33?65% of the required reduction in greenhouse gas emissions according to the Kyoto Protocol (Hartikainen et?al 2003 Supercond. Sci. Technol. 16 963). New technologies would include superconducting energy storage systems to effectively store power generation from renewable sources as well as high-temperature superconducting systems used in generators, transformers and synchronous motors in power stations and heavy-industry facilities. However, to be effective, these systems must be superior to conventional systems and, in reality, market penetration will occur as existing electrical machinery is written off. At current write-off rates, to achieve a 50% transfer to superconducting systems will take 20?years (Hartikainen et?al 2003 Supercond. Sci. Technol. 16 963).The Roadmap next considers dc transmission of green power with a section by Eckroad and Marian who provide an update on the development of superconducting power transmission lines in view of recent sustainability studies. The potential of magnetic energy storage is then presented by Coi and Kim, who argue that a successful transition to wind and solar power generation must be harmonized with the conventional electrical network, which requires a storage technology with a fast response and long backup times.Transport. Superconducting Maglev trains and motors for international shipping have the potential to considerably reduce the emissions that contribute to greenhouse gases while improving their economic viability by reducing losses and improving efficiencies. International shipping, alone, contributes 3% of the greenhouse gas emissions. Three sections of the Roadmap identify how high-speed rail can be a major solution to providing fast, low energy, environmentally-friendly transport enabling reduction in automobile and aircraft travel by offering an alternative that is very competitive. With maritime international environmental regulations tightening, HTS motors with the characteristics of high torque and compactness will become important devices for high-performance and low-emission electric ship propulsion systems. A section on the development of a megawatt-class superconducting motor for ship propulsion is presented by Umemoto.Monitoring in manufacturing for waste reduction. Environmental impact from the waste created by the manufacturing sector and the need to make manufacturing efficient can be addressed by terahertz imaging. This technology has great potential in non-destructive testing, industrial process monitoring and control to greatly improve the industry process efficiency and reliability by reducing waste materials and toxic by-products. The section by Du shows how terahertz imaging can provide process and property information such as rust levels under paint that can assist with the reduction of waste in manufacturing and maintenance.Monitoring for naturally occurring disturbances. The environmental and social impact of natural disasters is mounting. Febvre provides the Roadmap for the use of ultra-sensitive magnetometry to understand geomagnetic phenomena and Earth?ionosphere couplings through the study of very small variations of the magnetic field. This magnetic monitoring has many implications for understanding our environment and providing new tools for early warning of natural hazards, either on Earth or in space which will enable us to be better prepared for natural disasters.Restoring environments after military use. Throughout the world, there are many areas confirmed or suspected of being contaminated by unexploded munitions known as unexploded ordnance (UXO). Its presence is the result of wars and training of military forces. Areas affected by UXO contamination are hazardous to the public and have a major influence on the nature of land use. UXO has impact in developed as well as developing nations. For example, the USA has UXO dating back to the American Civil War and countries such as Cambodia are living with landmines as a daily issue due to more recent wars. Underwater UXO has caused severe impacts such as the explosion in 1969 in the waters of Kent in the UK that caused a reading of 4.5 on the Richter scale for earthquake monitors. Another example was a land-based detonation of a 500?kg World War II bomb in Germany killing three people in 2010. There is countless UXO from recent conflicts worldwide. Detection and accurate location with 100% reliability is required to return land to safe civilian use. Keenan provides details of a prototype magnetic gradiometer developed for this purpose.Reducing power needs for high-end IT. Supercomputers are so large that they are close to requiring their own small power plant to support the energy needed to run the computer. For example, in 2011 Facebook data centers and operations used 532 million kW hours of energy. Mukhanov explores the potential of reducing the power dissipation for future supercomputers from more than 500?MW for Exascale systems to 0.2?MW by using superconducting-ferromagnetic Josephson junctions for magnetic memory and programmable logic.Clearly superconductivity is an ultimate energy-saving technology, and its practical implementation will contribute to the reduction of CO2 emissions, improved water purification, reduction of waste and timely preparedness for natural disasters or significant events. This Roadmap shows how the application of superconducting technologies will have a significant impact when they are adopted.

https://iopscience.iop.org/article/10.1088/0953-2048/26/11/113001/pdf

Superconductivity and the environment: a Roadmap

We review the modeling progress of the magnetic response of hard type-II superconductors (SCs) using the critical-state model (CSM). We focus on magnetization loops when a uniform field is applied to the SC and on the levitation forces that appear when the applied field is nonuniform. Different analytical and numerical solutions of the CSM are discussed, and the main characteristics and parameters of the magnetization loops and levitation forces are reviewed. Although this paper does not pretend to be an exhaustive review of the modeling of type-II SCs or of the superconducting levitation studies, a general overview of some important theoretical models used to understand the hard type-II SC macroscopic behavior is presented.

Macroscopic Modeling of Magnetization and Levitation of Hard Type-II Superconductors: The Critical-State Model

In order to improve the cost performance of the present high-Tc superconducting (HTS) Maglev vehicle system for practical application, the multi-pole permanent magnet guideway (PMG) concept was introduced. A well-known double-pole Halbach PMG was chosen as a representative of multi-pole PMGs to compare with traditional monopole PMGs from the point of view of levitation efficiency and cost. Experimental results show that YBCO bulks above the double-pole Halbach PMG can exhibit better load capability and guidance performance as well as dynamics stability at the applied working height between the bulk HTSC and the PMG due to a more reasonable magnetic field distribution at the working range of bulk HTSC. Furthermore, the double-pole PMG configuration can play a more important role in improving guidance performance due to the potential-well field configuration. By comparing with former 'century' PMGs, the double-pole Halbach PMG shows another remarkable advantage in reducing the cost of levitation. As another necessary issue, magnetic field homogeneity and the corresponding magnetic drag force of a double-pole Halbach PMG has been considered by experiment in spite of the above highlights. Synthetically, the multi-pole Halbach PMG design is concluded to be one important choice for future HTS Maglev vehicle applications because of its high efficiency and low cost.

https://iopscience.iop.org/article/10.1088/0953-2048/21/11/115018/pdf

High-efficiency and low-cost permanent magnet guideway consideration for high-Tc superconducting Maglev vehicle practical application

A magnetic levitation vehicle using bulk high-Tc superconductors (HTSC) is considered as a promising transportation type thanks to its lateral inherent stability, but previous studies have found that the levitation force (LF) decays due to lateral movement. In this paper, a pre-load method is presented to reduce the LF decay, and the experimental results indicate that this method is very applicable in supressing this decay in spite of the applied field and material property of the bulk HTSC, and this effect can be ascribed to the reduction of the hysteresis loss in the bulk HTSC, i.e. more trapped magnetic flux after the pre-load case. In the end, experimental results indicate that the Halbach PMG has an advantage to reduce the cost of the PMG, but its rate of LF decay is also larger due to lateral movement

https://iopscience.iop.org/article/10.1088/0953-2048/21/6/065020/pdf

Y Y Lu

Papers

High-efficiency and low-cost permanent magnet guideway consideration for high-Tc superconducting Maglev vehicle practical application

Method to reduce levitation force decay of the bulk HTSC above the NdFeB guideway due to lateral movement