Motoaki Terai

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.

The Project Overview of the HTS Magnet for Superconducting Maglev

This paper describes the outline of a development project for the HTS magnet for the superconducting Maglev, which commenced in 1999. A very small current decay rate of 0.44%/day was achieved in 2003, using a prototype HTS coil, and a second HTS magnet, consisting of four persistent current HTS coils, was produced in 2005 for vehicle running tests. The second HTS magnet was operated in a persistent current mode at a rated magneto-motive force of 750 kA, and a top speed of 553 km/h was attained on the Yamanashi Maglev Test Line on December 2,2005.

Persistent current HTS magnet cooled by cryocooler (1)-project overview

This paper describes a project overview for a persistent current HTS magnet, which has been in development for Maglev trains since 1999. The HTS magnet operates with a very small current decay rate of 0.44%/day and can be cooled by a cryocooler below 20 K. The HTS coil consists of 12 single-pancake coils, which were wound with 4 parallel Ag-sheathed Bi2223 tapes. In order to minimize the magnetic field decay rate during persistent current operation, we have made efforts not to decrease the high Tc superconductor characteristics during the winding of the single-pancake coils. The HTS coil is connected with a persistent current switch made of a YBCO thin film, and cooled by a G-M (Gifford-MacMahon) type two-stage pulse tube cryocooler. Detachable current leads were used to reduce heat leakage to the 1st stage of the cryocooler.

Persistent current HTS magnet cooled by cryocooler (4) - persistent current switch characteristics

We developed a persistent current high temperature superconducting (HTS) magnet for Maglev train. The HTS magnet mainly consists of an HTS coil, a persistent current switch (PCS), a GM type two-stage pulse tube cryocooler. A PCS is one of the most important components to maintain persistent current operation. A YBCO thin film was adopted for a PCS conductor because it has a high resistivity over a critical temperature and a high critical current density at lower temperatures. Persistent current mode operation tests were successfully carried out with the PCS. The current decay rate at the rated current operation of 532 A was 0.44%/day which was investigated by measuring the magnetic field at the center of the coil.

HTS Magnet for Maglev Applications (1)— Coil Characteristics

We developed an HTS coil for maglev applications. The magnet consists of four persistent current HTS coils and is operated at a rated temperature of 20 K and a rated magnetomotive force of 750 kA for each coil. This paper describes the fabrication and test results of each persistent current HTS coil. The HTS coil consists of 12 single-pancake coils wound with four parallel Ag-sheathed Bi2223 wires and a persistent current switch (PCS) made of YBCO thin films. The coil is conductively cooled by a cryocooler to approximately 20 K. Persistent current operating tests for four HTS coils at 750 kA were carried out and current decay rates of 0.37-0.68%/day were obtained. Mechanical vibration tests up to plusmn15 (plusmn150 m/s2) were carried out to investigate the mechanical properties of the HTS coils. Temperature increasing tests up to 25 K, which is 5 K higher than the rated operating temperature and higher magnetomotive force operating tests up to 800 kA were carried out to investigate the thermal stability of the coils and check the mechanical strength of the coils

Persistent current HTS magnet cooled by cryocooler (3)-HTS magnet characteristics

We fabricated a persistent current HTS magnet wound with conductors composed of four Ag-sheathed Bi2223 wires and an insulated stainless-steel tape. The HTS magnet is composed of 12 racetrack formed single-pancake coils and impregnated with epoxy resin. The magnet is the same size as a magnet for a Maglev train. The stored energy of the magnet is 0.34 MJ and the central magnetic field is 1.3 T at the rated current operation of 532 A. Cooling the magnet to less than 20 K, I-V characteristics in persistent current operations and AC losses in charging and discharging the magnet were investigated.

Persistent current HTS magnet cooled by cryocooler (2) - magnet configuration and persistent current operation test

An high temperature superconducting (HTS) magnet, consisting of an HTS coil, a persistent current switch, a GM type two-stage pulse tube cryocooler, and YBCO current leads was developed. Detachable current leads were adopted to reduce heat leakage during persistent current operation. The HTS coil was cooled to approximately 10 K and persistent current mode operation tests were carried out at various currents up to 532 A, which is the rated current. Current decay at each persistent current mode operation was investigated by measuring the magnetic field at the center of the coil. The current decay rate at the 532 A operation was found to be approximately 0.44%/day.

Development of a low heat leak current-lead system

This paper describes a low heat leak current-lead system for a high temperature superconducting magnet which is refrigerated by conduction cooling and operated in a persistent-current mode. Under the condition that the current lead is cooled by conduction without gas cooling, we investigated the current-lead structure with which the heat load to the cryocooler is sufficiently low. The current lead consists of two parts. One of them spans the temperature interval between room temperature and around 70 K. The other spans the temperature interval between around 70 K and the lower end temperature. The former is made of copper alloy and the latter is made of a high temperature superconductor. To decrease the heat leak to a thermal anchor in the 70 K region, a detachable joint is installed in the copper alloy part. The driving mechanism for the joint is set in the room temperature region. An ultrasonic rotation motor, which works in the vacuum and the magnetic field, is adopted for the driving mechanism. We designed and constructed a detachable current lead of 600 A class, and obtained a test result that the heat leak to the thermal anchor is sufficiently low.

The Running Tests of the Superconducting Maglev Using the HTS Magnet

An HTS magnet for a Superconducting Maglev, consisting of four persistent current HTS coils, was developed. The HTS coils are installed in a cryostat, and cooled to approximately 15 K by conduction cooling, using two sets of two-stage GM type pulse tube cryocoolers. The HTS magnet is operated in a persistent current mode at a rated magneto-motive force of 750 kA. The running tests were executed on the Yamanashi Maglev Test Line, with a top speed of 553 km/h achieved on December 2, 2005. The test result demonstrated that the HTS coils generated no excessive vibration or heat load.

HTS Magnet for Maglev Applications (2)–Magnet Structure and Performance

An HTS magnet for maglev application has been developed. The magnet consists of four persistent-current HTS coils, and is operated at a rated temperature of 20 K and a rated magnetomotive force of 750 kA for each coil. This paper describes the structure and performance test results of the HTS magnet. The four HTS coils are installed in a cryostat and conductively cooled by two sets of two-stage GM type pulse tube cryocoolers below 20 K. Detachable current leads, which are composed of connectors and ultrasonic motors, are adopted to reduce the heat leakage to the 1st stage cold head of the cryocoolers. The HTS coils are simultaneously charged up to the rated magnetomotive force. Persistent current operating tests were carried out and the current decay rates of 0.4-0.7%/day were attained. Also, in order to evaluate the mechanical capability of the magnet, vibration tests were conducted and permissible vibration responses were obtained