Zigang Deng

Superconductivity and the environment: a Roadmap

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.

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

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

Free Vibration of the High Temperature Superconducting Maglev Vehicle Model

Free vibration of the high temperature superconducting (HTS) Maglev vehicle model has been investigated after an impulse force over the permanent magnet guideway. The impulse force was used to simulate the external disturbances on the HTS Maglev vehicle so as to study its vibration characteristics. In the experiments, the free vibration curves of time dependence of acceleration and frequency dependence of displacement were measured. It was found that the free vibration curves were some damped free vibration curves which seemed to decrease exponentially. Applying the impulse response curves to the dynamic equation of the HTS Maglev vehicle model, the stiffness and the damping coefficient were evaluated. The relationships between field cooling height (FCH) and the stiffness and damping coefficient were investigated. A 30 mm FCH has been proposed for the good dynamic stiffness and damping coefficient so that the unnecessary vibration of the HTS Maglev vehicle model can be eliminated automatically. The dynamic results are helpful to the further design of the HTS Maglev transport system for high-speed application.

Stability of the Maglev Vehicle Model Using Bulk High Tc Superconductors at Low Speed

Based on the study of static properties of the high temperature superconducting (HTS) Maglev vehicle, the dynamic characteristics and stability are investigated in the paper. A Maglev vehicle model using 86 bulk high Tc superconductors (HTSCs) is made at 1/4 scale of the first man-loading HTS Maglev test vehicle. Dynamic characteristics of the low-speed HTS vehicle in three directions are studied by measuring vibration signals of six essential point of the vehicle model. The natural frequency is analysed. 30 mm height is suggested as a reasonable field cooling height (FCH). Lower FCH brings the operation stability of the HTS Maglev system over permanent magnetic guideway (PMG) at low speed. Dynamic stability dependence on the speed of the HTS vehicle is quite different from that of the conventional Maglev vehicle system. The effect of speed on the unsafe motions can be suppressed by decreasing FCH in the operation of the vehicle model over the PMG to a great extent.

Performance Advances of HTS Maglev Vehicle System in Three Essential Aspects

In order to put the practice of high temperature superconducting (HTS) Maglev vehicle technology into peoples life, the interaction between high temperature superconductor (HTSC) and permanent magnet guideway (PMG) as the basic model of HTS Maglev vehicle was carefully investigated and enhanced from three essential aspects, i.e., bulk HTSC material, PMG field and bulk HTSC magnetization. The maglev experiments were performed with three kinds of bulk HTSC materials, two kinds of PMGs and two kinds of magnetization methods. It is found that three aspects are all very effective to improve the levitation capability and lateral stability. With better bulk material, more reasonable PMG configuration and magnetization method, the performance of HTS Maglev vehicle system will be greatly advanced and closer to an economical and practical level.

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

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 mm2. 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.

Optimization and Design of the Permanent Magnet Guideway With the High Temperature Superconductor

In order to enhance the levitation and guidance performance of the levitated high temperature superconductor (HTS) bulk over the permanent magnet guideway (PMG), it is necessary to optimize the design of the guideway. First of all, a three dimensional (3D) model of the guideway was built up, through which the influence of the air gap across the guideway on the magnetic field was studied. It was found that the magnetic field 10 mm above the guideway is roughly uniform in the length direction though that 1 mm above the guideway is not continuous. Since generally the levitation gap between the vehicle body and the guideway surface is more than 10 mm, it is possible to simplify the HTS-PMG interaction model from 3D to 2D. Subsequently the levitation and guidance forces of the superconductor with different kinds of permanent magnet guideways were calculated in the 2D model. Provided that the product of the width and the height is 2000 mm2, the numerical results indicated that the HTS-PMG system is optimum when the width ratio between PMG and HTS is between 1.005 and 1.105

Maglev performance of a double-layer bulk high temperature superconductor above a permanent magnet guideway

In order to improve the performance of the present high temperature superconducting (HTS) maglev vehicle system, the maglev performance of single- and double-layer bulk high temperature superconductors (HTSC) was investigated above a permanent magnet guideway (PMG). It is found that the maglev performance of a double-layer bulk HTSC is not a simple addition of each layers levitation and guidance force. Moreover, the applied magnetic field at the position of the upper layer bulk HTSC is not completely shielded by the lower layer bulk HTSC either. 53.5% of the levitation force and 27.5% of the guidance force of the upper layer bulk HTSC are excited in the double-layer bulk HTSC arrangement in the applied field-cooling condition and working gap, bringing a corresponding improvement of 16.9% and 8.8% to the conventional single-layer bulk HTSC. The present research implies that the cost performance of upper layer bulk HTSC is a little low for the whole HTS maglev system.

A High-Temperature Superconducting Maglev Dynamic Measurement System

The dynamic measurement of high temperature superconducting (HTS) magnetic levitation (Maglev) vehicle is a very important and difficult problem. In order to investigate the dynamic characteristics behavior of HTS Maglev, an HTS Maglev dynamic measurement system (SCML-03) was successfully developed in Applied Superconductivity Laboratory (ASCLab) of Southwest Jiaotong University, P. R. China. The system is mainly constituted by the circular permanent magnet guideway (PMG), liquid nitrogen vessel, data acquisition and processing, mechanical drive, autocontrol and so on. The PMG is fixed along the circumferential direction of a big circular disk with diameter 1500 mm. The maximum linear velocity of the PMG is about 300 km/h when the circular disk rotates round the central axis at 1280 rpm. The liquid nitrogen vessel with high temperature superconductors is placed above the PMG, and the vessel is not three-dimensional rigid connection with measurement sensor devices. These sensors can detect weak force change from three-dimensional directions. The maximal vertical and horizontal support force of the system are 3350 N and 500 N, respectively. Test process and results of the HTS Maglev dynamic test system are reported.

An efficient and economical way to enhance the performance of present HTS Maglev systems by utilizing the anisotropy property of bulk superconductors

We report a simple, efficient and economical way to enhance the levitation or guidance performance of present high-temperature superconducting (HTS) Maglev systems by exploring the anisotropic properties of the critical current density in the a–b plane and along the c-axis of bulk superconductors. In the method, the bulk laying mode with different c-axis directions is designed to match with the magnetic field configuration of the applied permanent magnet guideway (PMG). Experimental results indicate that more than a factor of two improvement in the levitation force or guidance force is achieved when changing the laying mode of bulk superconductors from the traditional fashion of keeping the c-axis vertical to the PMG surface to the studied one of keeping the c-axis parallel to the PMG surface, at the maximum horizontal and vertical magnetic field positions of the PMG, respectively. These phenomena resulted from the physical nature of the generated levitation force and guidance force (electromagnetic forces) and the fact that there are different critical current densities in the a–b plane and along the c axis. Based on the experimental results, new HTS Maglev systems can be designed to meet the requirements of practical heavy-load or curved-route applications.