Kyeongdal Choi

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.

Design of HTS Magnets for a 600 kJ SMES

Development of a 600 kJ Superconducting Magnetic Energy Storage (SMES) system is in progress by Korean Electric Research Institute (KERI). High-temperature superconducting (HTS) wires are going to be used for the winding of the system. The design of the HTS windings for the system is presented in this paper. We considered BSCCO-2223 wire for the HTS windings. The operating temperature of the winding was decided to be 20 K which will be accomplished by conduction cooling method using cryo-coolers. Auto-Tuning Niching Genetic Algorithm was adopted for an optimization method of the HTS magnets in the SMES system. The objective function of the optimal process was minimizing the total amount of the HTS wire. We also estimated the AC loss which can be generated in the discharge period. These HTS windings are going to be applied to the SMES system whose purpose is the stabilization of the power grid

Characteristic tests of a 1 MVA single phase HTS transformer with concentrically arranged windings

A 1 MV A single phase high temperature superconducting (HTS) transformer was manufactured and tested. The rated voltages of primary and secondary of the HTS transformer are 22.9 kV and 6.6 kV respectively. BSCCO-2223 HTS tape was used for HTS windings of 1 MV A HTS transformer. In order to reduce AC loss generated in the HTS winding, the type of concentric arrangement winding was adopted to a 1 MV A HTS transformer. Single HTS tape for primary windings and 4 parallel HTS tapes for secondary windings were used considering the each rated current of the HTS transformer. A core of HTS transformer was fabricated as a shell type core made of laminated silicon steel plate. And a GFRP cryostat with a room temperature bore was also manufactured. The characteristic tests of 1 MV A HTS transformer were performed such as no load test, short circuit test and several insulation tests at 65 K using sub-cooled liquid nitrogen. From the results of tests, the validity of design of HTS transformer was ascertained.

Stress Analysis of HTS Magnet for a 600 kJ SMES

Auto tuning niching genetic algorithm was used to design optimal HTS magnets for the 600 kJ class SMES system under several design constraint conditions. Constraint conditions were operation loss of magnet (less than 2 W), inductance of magnet (less than 24 H), the number of double pancake coils (about 10 DPCs), the number of turns of DPC (less than 300 turns), outer diameter of DPC (close to 800 mm) and total length of HTS wire in a DPC (less than 500 m). As a result of optimum design, we obtained design parameters for the 600 kJ SMES magnet according to two operating currents, 360 A and 370 A. However, even though the HTS magnet was designed optimally in respect to the electromagnetics, consideration of mechanical integrity due to the stress by Lorentz force must not be neglected for the stable operation of the SMES system. Therefore, we developed a program, through the finite element method (FEM), for stress analysis due to Lorentz force in operation of the SMES system. In this paper, the stresses (radial and hoop stress) imposed on the designed HTS magnets were calculated by the program, and the results of stress analysis were discussed.

Design of a 1 MVA high T/sub c/ superconducting transformer

A 1 MVA transformer using BSCCO-2223 high T/sub c/ superconducting (HTS) tapes was designed. The rated voltages of each sides of the transformer for primary and secondary are 22.9 kV and 6.6 kV respectively. Double pancake HTS windings, which have advantages of insulations and distribution of high voltage, were adopted. Four HTS tapes were wound in parallel for the windings of low voltage side. Each winding was composed of several double pancake windings and four parallel conductors of secondary winding were transposed in order to distribute the currents equally in each conductor. The core of the transformer was designed as a shell type core made of laminated silicon steel plate and the core is separated from the windings by a cryostat with a room temperature bore. Configuration of the cryostat made of nonmagnetic and nonconducting material and a liquid nitrogen sub-cooling system were used in order to maintain the coolants temperature of 65 K.

Conceptual Design of HTS Magnet for a 5 MJ Class SMES

Superconducting magnetic energy storage (SMES) systems with High Temperature Superconducting (HTS) wires have been actively developed world-wide. A 600 kJ class SMES with Bi-2223 HTS wire has been in development as a national project since 2004 and is currently approaching the final testing stage of the first of three phases. In the second phase of the project, several MJ class HTS SMES will be developed. In this paper, designs of magnets for 5 MJ class SMES with DI-BSSCO and YBCO coated conductor are presented and compared.

AC Loss and Thermal Stability of HTS Model Coils for a 600 kJ SMES

A 600 kJ superconducting magnetic energy storage system (SMES) project with high temperature superconductor (HTS) started as a national project in Korea. The HTS model coils were designed and fabricated for a preliminary test prior to the creation of a full scale prototype. Single reinforced BSCCO-2223 wires were used for the model coils and the operating temperature was decided to be 20 K. Even though an SMES is not an AC-powered device, time-varying currents during the charging and discharging periods lead to the generation of time-variation magnetic fields applied to the model coils and the generation of AC loss. In this paper, AC loss and the temperature distribution of model coils are analyzed and discussed.

Reduction Effect on Magnetization Loss in the Stacked Conductor With Striated and Transposed YBCC Coated Conductor

Recently, it is proposed to make striations on the YBCO coated conductor and to transpose each other as one of the solutions to decrease the perpendicular magnetization loss. For large power application using HTS, the stacked conductor packing the YBCO coated conductors should be used because the current carrying capacity of a single conductor is limited. The stacked conductor has different AC loss characteristics from single conductor because the screening currents in the adjacent conductors affect the local magnetic field at the position of each conductor in the stacked conductors. In this paper, we research the effect by the stack, striation and transposition on magnetization loss of YBCO coated conductors in perpendicular magnetic field. To estimate the reduction effects of perpendicular magnetization loss, several short samples as the stacked conductor with striation and transposition are prepared and tested. We compare the measured results of the conductors with that of the single YBCO coated conductor to estimate the reduction effects.

Design of a Single Phase 33 MVA HTS Transformer With OLTC

HTS transformers which have been developed until now had only fundamental structures. Among the auxiliary functions of conventional transformers, voltage regulating is the most important one. For the voltage regulation, conventional transformers are equipped with on load tap changers (OLTCs). In this paper, we investigate the possibility of the HTS transformer with OLTC. For the case study, we designed a single phase 33 MVA HTS transformer with OLTC. It is one of three individual HTS transformers which composes a 3 phase, 100 MVA transformer. It is expected to substitute for a 3 phase, 60 MVA conventional transformer in Korea. The parameters of an HTS transformer are varied due to the gap length between primary and secondary windings. The length was decided for the transformer to have the impedance of 12%. Its size was limited to the one of the conventional transformer. The characteristics of the HTS transformer were analysed in both case of having OLTC and not.

Tests of disk type magnetic flux pump with the ability of high voltage output

Using a superconducting magnetic flux pump, thick power leads for a superconducting magnet could be replaced with thin string leads to excite the excitation magnet of the superconducting flux pump. We have developed a new type of flux pump with high-voltage output to shorten the charge and discharge time of the load magnet. The test of the pump with four stacked disks as the exciter for the load magnet has been carried out. This disk type flux pump yielded 70 mV of voltage across its terminal and 10 A of current through a 85 mH load magnet which was the field winding of 20 kVA class fully superconducting generator within 12 seconds. This output voltage of the new flux pump is about 10 times larger than that of our previous work. Moreover since it is easy to stack disks for a superconducting flux pump, the high-voltage exciter for a 1 H class superconducting magnet could be expected to be made easily.