High-temperature Superconducting Materials Research Articles

A Review of the Cryocooler-Based Cooling Systems for SMES

A key component in superconducting magnetic energy storage (SMES) system design is the cooling system. A well-designed cooling apparatus allows a SMES to work with higher critical currents, have less AC losses and work in a stable way. Acknowledging the importance of cooling systems in a SMES and that there have been many different designs presented in the bibliography, we hereby analyze various thermal designs that utilize cryocoolers, and we estimate the total volume of the superconducting coils used in their experiments. This review article focuses on recent high temperature superconducting (HTS) materials, and presents the cooling methods employed to cool the coil in conjunction with other important characteristics, such as the coil geometry, the operating temperature of the magnet, the thermal insulation temperature and the cooling power of the cryocoolers. From the presented analysis, the authors propose a procedure to devise a proper cooling scheme for a SMES design. Additionally, a qualitative comparative assessment of the analyzed designs in literature, in eight assessment criteria, is presented.

Leakage flux reduction of axial-flux switching PM machine by using HTS-disk

Nowadays, axial flux switching permanent magnet machines are attractive and widely used in direct drive applications because of their unique features. This paper proposes a high temperature superconductor (HTS) disk axial flux switching permanent magnet (AFSPM) machine with spoke type permanent magnets (PMs) and three-phase two layers concentrated windings. The novelty of the proposed machine is using HTS material on the rotor and stator as a disk, insignificant relative permeability of the HTS materials causes magnetic reluctance to become extreme. Because of this feature HTS-Disk in the proposed HTS-AFSPM machine does not allow the flux to enter or exit which causes leakage flux reduces. In order to better investigate and fair comparison, all analyses have done at the same condition using the finite element method (FEM) by Ansys Maxwell. The comparison results show that the proposed HTS-Disk AFSPM machine achieves higher back-EMF, permanent magnet (PM) flux, flux distribution, lower inductance and losses and fewer total harmonics distribution compared to conventional AFSPM machine.

New coil configurations with 2G-HTS and benefits for applications

A scalable concept to prepare high current density windings with high-temperature superconducting material is introduced. The concept covers miniaturized high-current windings and large coils for applications in energy technology as well. The principle is based on a circular disk-up-down-assembly (‘DUDA’) and extended to rectangular coils. First measurements on the assemblies (≈40 turns) in liquid nitrogen are presented as a proof-of-concept. Centre fields of ≈40 mT and ≈340 mT are measured during steady operation and pulsed operation respectively. Operating the assemblies at lower temperatures will strongly increase the current and field performance. Lowering the contact resistance might lead to further improvements. Due to the homogenous structure in the radial direction, shear stresses are minimized and large winding heights can be realized in principle. The DUDA concept of coil windings can be used to build even more sophisticated magnetic arrangements, e.g. Halbach-arrays, or complex windings for new stator configurations of rotating machines. The optional miniaturization offers compact and powerful magnets, e.g. for accelerators too.

Quench Detection and Protection for High-Temperature Superconductor Accelerator Magnets

High-temperature superconductors (HTS) are being increasingly used for magnet applications. One of the known challenges of practical conductors made with high-temperature superconductor materials is a slow normal zone propagation velocity resulting from a large superconducting temperature margin in combination with a higher heat capacity compared to conventional low-temperature superconductors (LTS). As a result, traditional voltage-based quench detection schemes may be ineffective for detecting normal zone formation in superconducting accelerator magnet windings. A developing hot spot may reach high temperatures and destroy the conductor before a practically measurable resistive voltage is detected. The present paper discusses various approaches to mitigating this problem, specifically focusing on recently developed non-voltage techniques for quench detection.

Calculation and comparison of HTS electromagnetic characteristics with different models

To ensure the effective design and operation of high-temperature-superconducting (HTS) devices, the electromagnetic properties of HTS materials attract widespread attention. To date, the H-formulation and T-A formulation are two principal formulations applied to the finite element method to analyze the electromagnetic characteristics of HTS materials and devices. It is necessary to verify and to conduct a comparison of different effects of element order, mesh number along the width, and thickness expansion, with regard to calculation efficiency and accuracy under the H model and T-A model respectively. Compared to the H model, the T-A model with linear or quadratic element order can complete the calculation process more efficient having high accuracy and less time. The model with optimal parameters has been verified in a common case of a superconducting pancake coil. The optimal model of this work benefits to design or simulate HTS applications in building practical large-scale devices in terms of calculation efficiency and accuracy.

Investigation of transmission properties in defective one dimensional superconductive photonic crystal for ultralow level bioethanol detection

The present study exhibits design and analysis of a superconductor-based defective 1D photonic crystal (PhC) to envisage an ultra-high sensitive ethanol sensor. The proposed structure is realized with alternate layers of high temperature superconductor (YBa2Cu3O7) and dielectric (SrF2) material, whereas the central defect layer is designed with porous silicon (P-Si) material. Transmittance and absorption spectrum are explored theoretically by employing transfer matrix method and two-fluid model. The mainstay of this work is to investigate the shift in wavelength of the resonant mode, which is created within the band gap, in the transmittance spectrum. The position of the defect mode wavelength is assayed by varying the incidence angle, thickness of superconductor layer and operating temperature. An ultra-high wavelength sensitivity of 8.53×105 nm/RIU and temperature sensitivity of 6.673 nm/K are achieved by the proposed sensor, which open up an avenue for effective sensing of different % volume of ethanol with minute refractive index contrast. Besides sensitivity, other sensing parameters like figure of merit, quality factor and detection limit are thoroughly studied and compared with the recently published works. On top of that, the simple structure, easy analysis, and available fabrication techniques make the proposed design a suitable candidate for biosensing applications.

Recent Advances and Challenges in the Development of Radiofrequency HTS Coil for MRI

Radiofrequency (RF) coils fashioned from high-temperature superconductor (HTS) have the potential to increase the sensitivity of the magnetic resonance imaging (MRI) experiment by more than a dozen times compared to conventional copper coils. Progress, however, has been slow due to a series of technological hurdles. In this article, we present the developments that recently led to new perspectives for HTS coil in MRI, and challenges that still need to be solved. First, we recall the motivations for the implementations of HTS coils in MRI by presenting the limits of cooled copper coil technology, such as the anomalous skin effect limiting the decrease of the electric resistance of normal conductors at low temperature. Then, we address the progress made in the development of MRI compatible cryostats. New commercially available low-noise pulsed-tube cryocoolers and new materials removed the need for liquid nitrogen-based systems, allowing the design of cryogen-free and more user-friendly cryostats. Another recent advance was the understanding of how to mitigate the imaging artifacts induced by HTS diamagnetism through field cooling or temperature control of the HTS coil. Furthermore, artifacts can also originate from the RF field coupling between the transmission coil and the HTS reception coil. Here, we present the results of an experiment implementing a decoupling strategy exploiting nonlinearities in the electric response of HTS materials. Finally, we discuss the potential applications of HTS coils in bio-imaging and its prospects for further improvements. These include making the technology more user-friendly, implementing the HTS coils as coil arrays, and proposing solutions for the ongoing issue of decoupling. HTS coil still faces several challenges ahead, but the significant increase in sensitivity it offers lends it the prospect of being ultimately disruptive.

High temperature superconductors for fusion applications and new developments for the HTS CroCo conductor design

Recent improvements in the superconducting performance and technical maturity of high-temperature-superconductors (HTS) lead to considerations of using HTS in future fusion magnets in addition to the presently used low-temperature superconductors (LTS). Compact high field magnet systems entirely made of HTS for compact tokamaks, hybrid HTS-LTS magnets for enhanced operational capabilities (e.g. larger flux swing) in conventional tokamaks and future stellarator devices with HTS magnet systems are presently investigated. An overview of recent concepts, developments and designs of HTS-based future fusion magnet systems is given and a number of physical and technical challenges will be addressed, too: In particular, the so-called second generation HTS Rare-Earth-Barium-Copper-Oxide (REBCO) shows an excellent superconducting performance over a wide range of magnetic fields and temperatures. The layered architecture of these technical REBCO conductors and the ceramic nature of REBCO lead to mechanical challenges at high Lorentz forces, which is relevant for cable-in-conduit-conductors (CICC) of future fusion magnets due to the high currents and high field strengths. Different high-current cable concepts for future fusion magnets are discussed. High loads are not only a challenge for potential future HTS conductors but also for the conductor jackets and the coil casing of the magnet systems. An increase of the numbers of load cycles on the path towards a future fusion power plant requires superior mechanical strength. The high critical temperature of HTS materials allows to design HTS CICC with a noticeably higher minimum quench energy and temperature margin compared to LTS conductors – but leads inevitably to substantially slower quench propagation velocity and challenges related to quench detection. Recent results from numerical modeling and experimental investigation of quench in high-current HTS CrossConductor (HTS CroCo) based CICC are addressed.

Experimental investigation of the thermal performance of the thermosyphon cooling system with rotating

Rotating machine applications with superconductors attract much interest in the industry. For maintaining the operating temperature of high-temperature superconductor (HTS) field poles, a sophisticated cooling system is required. A thermosyphon (TS) is one of the ways for this purpose. The cryo-mechanical system composition is relatively simple, lightweight, and based on natural convection therefore not using any mechanical pump. It can supply the refrigerant from the static condenser part to the rotating evaporator part by using a successful rotary joint. The operating temperature of the TS cooling system depends on the refrigerant. Considering the current HTS materials, the suitable refrigerant is neon, hydrogen. Nitrogen which provides a higher operating temperature than neon and hydrogen is employed for future development. In this work, we focused on and investigated the heat transfer capacity of TS using nitrogen as the refrigerant. The heat transfer performance with rotating was also studied. As a result of the experiment, the TS cooling system could maintain the evaporator temperature by rotating. Moreover, it could transfer the 90 W heat load with rotating.

The small spacecraft with a magnetic sail on high-temperature superconductors

It is proposed to develop a small spacecraft for an experiment using high-temperature superconductors (HTS) and shape memory materials. The purpose of the experiment is to test a technological capability of creating a strong magnetic field on the small spacecraft using HTS and shape memory materials for deployed large-area structures, and study the magnetic field interaction with the solar wind plasma and the resulting force impact on the small spacecraft. This article is of a polemical character and makes it possible to take a fresh look at the applicability of new technologies in space-system engineering. Key words: high-temperature superconductors, shape memory materials, solar wind, spacecraft.

The small spacecraft with a magnetic sail on high-temperature superconductors

It is proposed to develop a small spacecraft for an experiment using high-temperature superconductors (HTS) and shape memory materials. The purpose of the experiment is to test a technological capability of creating a strong magnetic field on the small spacecraft using HTS and shape memory materials for deployed large-area structures, and study the magnetic field interaction with the solar wind plasma and the resulting force impact on the small spacecraft. This article is of a polemical character and makes it possible to take a fresh look at the applicability of new technologies in space-system engineering.

Numerical Study on Transient Behaviours of a 30-kW Generator Using a Coupling Method

As research and production technologies for high-temperature superconducting (HTS) materials have become increasingly mature, many high-efficiency and low-weight electrical machines made of HTS conductors have been successfully manufactured. In this paper, a transient numerical model for processing a three-phase symmetrical short circuit in a 30-kW HTS generator is proposed. It is based on an electromagnetic and thermal model, coupling the multiphysics of the rotating machinery and magnetic, circuit, and heat transfer modules. Some macroscopic characteristics of the generator, such as the output voltage and current waveforms, can be obtained. It also simulates the microscopic current shunting phenomenon between layers and temperature variation across HTS armature coils during a three-phase symmetrical short circuit fault. Then, some parameters of HTS conductors that are relevant to the temperature rise in coils are considered in this model. This simulation is an effective tool for analysing the transient performance of HTS generators in various fault operating conditions and could correspondingly provide an important guidance for the HTS machines’ preliminary design stage.

A proposal of the hybrid energy transfer pipe

Among the many modifications of superconducting power transmission lines, hybrid lines stand out for their originality. Their design implies the joint transmission of cold liquid fuel through the pipe and electricity through the high-temperature superconducting (HTS) cable cooled by this fuel directly or indirectly. Currently, the critical temperatures of HTS materials are low and that means that only liquid hydrogen can be the “cooling fuel”. It is known that natural gas is a viable alternative to hydrogen as a chemical fuel for many reasons. Since its boiling temperature is too high, the use of liquefied natural gas (LNG) in hybrid lines is considered only in the future when suitable HTS materials will be discovered. Assuming that LNG cannot be used to cool HTS cable over the coming years, we propose to combine the LNG pipeline and the cable pipelines cold by liquid nitrogen in the common heat-insulating pipe. In addition to the considerable economic effect due to the common thermal insulation, the LNG cold will be utilized to cool the radiation shield that prevents the penetration of heat to the cable pipes.

Processing and application of high-temperature superconducting coated conductors

Coated conductors formed from the high-temperature superconducting (HTS) material REBCO (REBa2Cu3O7−δ) enable energy-efficient and high-power-density delivery of electricity, making them key materials for clean energy generation, conversion, transmission and storage. Widespread application of HTS coated conductor wires requires operation at high temperatures in wide-ranging magnetic fields, as well as low-cost processing. In this Review, we investigate different processing methods and applications of HTS coated conductors, highlighting advances in laboratory-scale conductor processing and performance, and examining commercial potential. We discuss how the nanostructure of the HTS material impacts wire performance across different application regimes, and how the nanostructure and performance are related to the inherent supersaturation levels of the respective processing method. We outline approaches to decrease wire cost and improve wire performance in the critical application regime (20–40 K, >1 T magnetic field), and examine emerging and potential future applications of HTS coated conductors.

A Lower-Pressure Route to Superconductivity

A new synthesis technique pushes high-temperature superconducting materials a step closer to ambient pressure.

The evolution of properties and microstructure of Bi-2212 wires after gamma-ray irradiation

Among various high-temperature superconducting materials, Bi2Sr2CaCu2O8+x (Bi-2212) is considered as one of the most promising candidates to fabricate superconductors for magnetic confinement fusion reactors. Considering that the superconductors will be subject to irradiation in nuclear reactors, the effects of gamma-ray irradiation on the superconducting properties of Bi-2212 wires is studied in the present work. Critical current (I c) tests have been done for Bi-2212 wires with different gamma-ray irradiation doses and the variation of I c is correlated to the change of microstructures. During the 12 T I c tests, the normalized I c first rises to 1.15 then decreases to 0.89 with the increase of irradiation time. Results from x-ray diffraction, Raman spectroscopy and x-ray photoelectron spectroscopy indicate that defects are produced within the gamma-ray irradiated samples. From the images of high resolution transmission electron microscopy, amorphous structure in the gamma-ray irradiated sample is discovered as well.

Topological Nature of High Temperature Superconductivity

AbstractThe key to unraveling the nature of high‐temperature superconductivity (HTS) lies in resolving the enigma of the pseudogap state. The pseudogap state in the underdoped region is a distinct thermodynamic phase characterized by nematicity, temperature‐quadratic resistive behavior, and magnetoelectric effects. Till present, a general description of the observed universal features of the pseudogap phase and their connection with HTS is lacking. The proposed work constructs a unifying effective field theory capturing all universal characteristics of HTS materials and explaining the observed phase diagram. The pseudogap state is established to be a phase where a charged magnetic monopole condensate confines Cooper pairs to form an oblique version of a superinsulator. The HTS phase diagram is dominated by a tricritical point at which the first order transition between a fundamental Cooper pair condensate and a charged magnetic monopole condensate merges with the continuous superconductor‐normal metal and superconductor‐pseudogap state phase transitions. The universality of the HTS phase diagram reflects a unique topological mechanism of competition between the magnetic monopole condensate, inherent to antiferromagnetic‐order‐induced Mott insulators and the Cooper pair condensate. The obtained results establish the topological nature of the HTS and provide a platform for devising materials with the enhanced superconducting transition temperature.

High temperature superconducting material based energy storage for solar-wind hybrid generating systems for fluctuating power management

The green energy infrastructure plays an important part in existing world of power scarcity. Owing to their dependence on environmental factors, renewable energy technologies continue to fluctuate. Using the energy storage device will solve the problem. The technical and economical requirements of the energy storage process can be met with the use of hybrid combinations. This paper proposes a hybrid energy management system based on the Super conductive magnetic material and the lead acid battery to provide power stabilization in the grid-connected unstable microgrid. Here, second-generation High Temperature Superconducting (HTS) material is used as Super Conducting Magnet Energy Storage (HTSMES) which exhibits a high irreversibility field and critical current density within an active magnetic field. The proposed system may be a good solution to minimize the impact of the Point of Common Coupling (PCC) power variability during fault condition. To improve the efficiency and flexibility of the proposed system, the two hybrid power sources are connected via dual input single output zeta converter. The HTSMES is used to minimize the difference in active power during fault and to give the reactive current to handle the fault. Grid connected microgrid with HTSMES-battery was simulated using the MATLAB Simulink platform and tested using an energy management algorithm with and without the presence of fault. The system proposed is demonstrated with detailed simulation results.

Reduction of Thrust Force Ripple of High Temperature Superconducting Linear Flux-Switching Motors using Asymmetry Mover Structure

Compared with traditional linear motors, such as Linear Permanent Magnet Motors (LPMs) and Linear Induction Motors (LIMs), Linear Flux-Switching Permanent Magnet (LFSPM) motors have the merits of high efficiency, power density, with simple and robotic secondary structure. Despite these advantages, the flux-weakening ability of LFSPM motor is limited and thus the speed range of it is not ideal. As a promising choice, it is feasible to replace the PMs of LFSPM motors with coils made with High Temperature Superconducting (HTS) tapes. By using HTS material, High Temperature Superconducting Linear Flux-Switching Motors (HTS-LFSMs) have good flux-weakening ability while inheriting the edges of LFSM motors. Since the existence of HTS coils, the cooling system has a minimum size and has to take up certain room of the motor. When it comes to applications where the volume of motor is strictly restrained, there may not be enough room for a basic pattern of typical pole pitch combinations for HTS-LFSM, such as 12-7 or 12-9, leading to large thrust ripple. To solve this problem, a method of reducing thrust force using asymmetry mover structure is proposed based on a 9-5 pole pitch ratio. The mechanism and working principle are analyzed and the validation is verified with the help of Finite Element Method (FEM).

Обзор высокотемпературных сверхпроводниковых электрических машин

Electrical machines are important parts of different power systems. The application of high temperature superconductors (HTS) in electrical machines is very promising due to high transport currents. This paper reviews various topologies of superconducting motors and generators using HTS published in the literature in recent time. It begins with a brief presentation of the HTS material used in electrical machines. The description of AC losses and cryogenic systems is done afterwards. Then we offer a striking description of the various realizations of HTS electrical machines such as half HTS synchronous machines, fully HTS synchronous machine, machines with HTS bulks and stacks. Some of these machines are totally innovative compared to conventional ones and their operating principle is strictly related to the presence of HTS materials.