Test of a DC-HTS Busbar Demonstrator for Power Distribution in Hybrid-Electric Propulsion Systems for Aircraft

In the framework of the German project TELOS (Thermo-Electrically Optimised Aircraft Propulsion Systems) a high-temperature superconducting 40 MVA DC demonstrator busbar for hybrid-electric propulsion systems for aircraft has been developed. The design current for a temperature below 25 K is 13.3 kA and the rated voltage is 3 kV. The 2-pole busbar contains 2 stacks of REBCO coated conductors which are supported by a 3D-printed structure allowing compensation of thermal length changes of the superconductor. It fits in a cryostat tube with an inner diameter of 25 mm. A special focus has been put on low-resistive joints that are necessary to connect single elements of the busbar system. The special layout of the joints allows an effective current redistribution between the different tapes in a stack. We present results for the test of the DC busbar demonstrator in liquid nitrogen at 77 K. The design current for this temperature is 3.3 kA which corresponds to a rated power of 10 MW. We applied currents up to 3.5 kA and measured the I-V characteristics and contact resistances of 90° and 180° joints in a virgin and in a strained state thus simulating thermal length changes. We also present results of Lorentz-Force tests with short AC current pulses up to 20 kA to demonstrate the viability of the design for application with currents up to 13.3 k

Engineering Properties of Superconducting Materials

Plastic (and microplastic) pollution has been described as one of the greatest environmental challenges of our time, and a hallmark of the human-driven epoch known as the Anthropocene. It has gained the attention of the general public, governments, and environmental scientists worldwide. To date, the main focus has been on plastics in the marine environment, but interest in the presence and effects of plastics in freshwaters has increased in the recent years. The occurrence of plastics within inland lakes and rivers, as well as their biota, has been demonstrated. Experiments with freshwater organisms have started to explore the direct and indirect effects resulting from plastic exposure. There is a clear need for further research, and a dedicated space for its dissemination. This book is devoted to highlighting current research from around the world on the prevalence, fate, and effects of plastic in freshwater environments

Investigation into maximizing component availability for superconducting cables in turbo-electric distributed propulsion aircraft

The commercial aviation industry is growing at a substantial rate, with demand doubling every 15 years and this trend is set to continue well into the 21st Century. At the same time regulatory pressures are being exerted on the industry as governments around the world seek to reduce their greenhouse gas emissions in an effort to contain global temperature rise to 2°C . Combined with existing infrastructure challenges, these issues are forcing air-framers to develop new, novel designs that support sustainable approaches to future aviation to meet environmental, social and economic demands. The pathway to decarbonisation of aviation will involve a combination of fuel, technology and operational measures. Many of the proposed technologies, such as electrical propulsion, are inherently disruptive and require changes to supply-chains,ground operations, maintenance standards and procedures, and pilot training. Such disruption is unavoidable given the scale of the challenge of electrical propulsion: a typical widebody jet engine for passenger aircraft can output over 22 MW fully loaded; an equivalent electrical system must be able to generate, distribute, and produce same amount of thrust with equal or greater reliability than the existing drivetrain that has been perfected over the course of the last century. Turbo-electric Distributed Propulsion (TeDP) is an approach for the electrification of propulsion systems on aircraft that aims to do this. Instead of large turbofan engines used to generate thrust, power in the engines is converted to electricity using electrical generators, and then distributed electrically through a network to propulsion motors placed in aerodynamically advantageous locations, significant fuel savings and performance benefits may be realised. Electrification of the propulsion system comes with large weight penalties. It is critical that the weight of the electrical power system does not mitigate the benefits of electrification. Superconducting electrical machines have been proposed as a route to lightweighting the electrical power system due to their promising high power densities compared to conventional electrical machines. It is proposed that the rest of the electrical power system be superconducting as far as technically possible to minimise heat sinks within the system. Integration of superconducting materials into the most safety critical aspects of commercial aviation raises multiple research questions regarding the design of resilient systems and how appropriate electrical protection strategies can be designed given the strict electric, magnetic, and thermal operating requirements that these components have. All electrical systems experience faults. This Thesis investigates how these faults manifest within a compact, power-electronically interfaced, superconducting network. The research presented in this thesis captures electrical protection requirements through modelling, simulation, and experimentation to develop requirements for TeDP feeder cables. By building on these requirements this thesis will then show how cable design can be optimised to withstand faults and present a control method which enables maximising throughput of cables during temperature rise events. This knowledge aims to improve availability, in terms of reducing the amount of superconducting network de-rating required, and power provision of superconducting feeder cables during adverse conditions encountered by superconducting TeDP aircraft.The commercial aviation industry is growing at a substantial rate, with demand doubling every 15 years and this trend is set to continue well into the 21st Century. At the same time regulatory pressures are being exerted on the industry as governments around the world seek to reduce their greenhouse gas emissions in an effort to contain global temperature rise to 2°C . Combined with existing infrastructure challenges, these issues are forcing air-framers to develop new, novel designs that support sustainable approaches to future aviation to meet environmental, social and economic demands. The pathway to decarbonisation of aviation will involve a combination of fuel, technology and operational measures. Many of the proposed technologies, such as electrical propulsion, are inherently disruptive and require changes to supply-chains,ground operations, maintenance standards and procedures, and pilot training. Such disruption is unavoidable given the scale of the challenge of electrical propulsion: a typical widebody jet engine for passenger aircraft can output over 22 MW fully loaded; an equivalent electrical system must be able to generate, distribute, and produce same amount of thrust with equal or greater reliability than the existing drivetrain that has been perfected over the course of the last century. Turbo-electric Distributed Propulsion (TeDP) is an approach for the electrification of propulsion systems on aircraft that aims to do this. Instead of large turbofan engines used to generate thrust, power in the engines is converted to electricity using electrical generators, and then distributed electrically through a network to propulsion motors placed in aerodynamically advantageous locations, significant fuel savings and performance benefits may be realised. Electrification of the propulsion system comes with large weight penalties. It is critical that the weight of the electrical power system does not mitigate the benefits of electrification. Superconducting electrical machines have been proposed as a route to lightweighting the electrical power system due to their promising high power densities compared to conventional electrical machines. It is proposed that the rest of the electrical power system be superconducting as far as technically possible to minimise heat sinks within the system. Integration of superconducting materials into the most safety critical aspects of commercial aviation raises multiple research questions regarding the design of resilient systems and how appropriate electrical protection strategies can be designed given the strict electric, magnetic, and thermal operating requirements that these components have. All electrical systems experience faults. This Thesis investigates how these faults manifest within a compact, power-electronically interfaced, superconducting network. The research presented in this thesis captures electrical protection requirements through modelling, simulation, and experimentation to develop requirements for TeDP feeder cables. By building on these requirements this thesis will then show how cable design can be optimised to withstand faults and present a control method which enables maximising throughput of cables during temperature rise events. This knowledge aims to improve availability, in terms of reducing the amount of superconducting network de-rating required, and power provision of superconducting feeder cables during adverse conditions encountered by superconducting TeDP aircraft

High temperature superconducting cables and their performance against short circuit faults: current development, challenges, solutions, and future trends

Along with advancements in superconducting technology, especially in high-temperature superconductors (HTSs), the use of these materials in power system applications is gaining outstanding attention. Due to the lower weight, capability of carrying higher currents, and the lower loss characteristic of HTS cables, compared to conventional counterparts, they are among the most focused large-scale applications of superconductors in power systems and transportation units. In near future, these cables will be installed as key elements not only in power systems but also in cryo-electrified transportation units, that take advantage of both cryogenics and superconducting technology simultaneously, e.g., hydrogen-powered aircraft. Given the sensitivity of the reliable and continuous performance of HTS cables, any failures, caused by faults, could be catastrophic, if they are not designed appropriately. Thus, fault analysis of superconducting cables is crucial for ensuring their safety, reliability, and stability, and also for characterising the behaviour of HTS cables under fault currents at the design stage. Many investigations have been conducted on the fault characterisation and analysis of HTS cables in the last few years. This paper aims to provide a topical review on all of these conducted studies, and will discuss the current challenges of HTS cables and after that current developments of fault behaviour of HTS cables will be presented, and then we will discuss the future trends and future challenges of superconducting cables regarding their fault performance

Dipole magnets above 20 tesla: Research needs for a path via high-temperature superconducting rebco conductors

To enable the physics research that continues to deepen our understanding of the Universe, future circular colliders will require a critical and unique instrument—magnets that can generate a dipole field of 20 T and above. However, today’s maturing magnet technology for low-temperature superconductors (Nb-Ti and Nb3 Sn) can lead to a maximum dipole field of around 16 T. High-temperature superconductors such as REBCO can, in principle, generate higher dipole fields but significant challenges exist for both conductor and magnet technology. To address these challenges, several critical research needs, including direct needs on instrumentation and measurements, are identified to push for the maximum dipole fields a REBCO accelerator magnet can generate. We discuss the research needs by reviewing the current results and outlining the perspectives for future technology development, followed by a brief update on the status of the technology development at Lawrence Berkeley National Laboratory. We present a roadmap for the next decade to develop 20 T-class REBCO accelerator magnets as an enabling instrument for future energy-frontier accelerator complex

Overview of H-Formulation: A Versatile Tool for Modeling Electromagnetics in High-Temperature Superconductor Applications

This paper reviews the modeling of high-temperature superconductors (HTS) using the finiteelement method (FEM) based on the H-formulation of Maxwell\u27s equations. This formulation has become the most popular numerical modeling method for simulating the electromagnetic behavior of HTS, especially thanks to the easiness of implementation in the commercial finite-element program COMSOL Multiphysics. Numerous studies prove that the H-formulation is able to simulate a wide scope of HTS topologies, from simple geometries such as HTS tapes and coils, to more complex HTS devices, up to large superconducting magnets. In this paper, we review the basics of the H-formulation, its evolution from 2D to 3D, its application for calculating critical currents and AC losses as well as magnetization of HTS bulks and tape stacks. We also review the use of the H-formulation for large-scale HTS applications, its use to solve multi-physics problems involving electromagnetic-thermal and electromagnetic-mechanical couplings, and its application to study the dynamic resistance of superconductors and flux pumps

Contribution for the Study of the Integration of Inductive Superconducting Fault Current Limiters in Electrical Distribution Grids

A wider adoption of distributed generation sources and an increased interconnection of networks tend to increase the complexity of electric power grids, thus causing a surge in failures, especially short-circuits. The conventional solution against short-circuit currents, for example, the construction of new substations, splitting of busbars, even updating the technology of the existing current limiters may prove either economically or technically unfeasible. Fault current limiters, mainly the superconducting fault current limiters, have already demonstrated their viability in electric power grids. Fault current limiter devices at normal operation are invisible to the grid, acting almost instantly upon a fault, returning to their normal state upon its correction. To disseminate these technologies, the development of straightforward design tools is required. These tools must consider the properties of the available constitutive elements of the devices. Behind these design tools, the integrity of the fault current limiter should be assured during its operation. Problems regarding the electrodynamic forces developed under short-circuit events must be properly characterized because they can damage windings, causing device breakage and affecting the power grid. In this thesis, a design methodology that intends to model and optimise saturated cores superconducting fault current limiters is presented. This methodology considers the characteristics of each constitutive element of the limiter while addressing utility requirements and power grid characteristics. Genetic algorithms are used both to optimise the constitutive elements of the limiter and its performance in the power grid. In order to validate the present methodology, a three-phase superconducting fault current limiter is designed/optimised, built and tested. The electrodynamic forces analysis developed in superconducting tapes of an inductive transformer type superconducting fault current limiter, under short-circuit conditions is performed.A crescente adoção de fontes de geração distribuída e o aumento das ligações internas entre redes de energia levou ao aumento da complexidade das redes elétricas, causando um provável aumento do número de falhas, especialmente os curto-circuitos. Soluções convencionais para lidar com curto-circuitos, como por exemplo, a construção de novas subestações, a divisão dos barramentos, ou a atualização tecnológica dos limitadores de corrente existentes, podem se mostrar muito dispendiosas ou tecnicamente inviável. Os limitadores de corrente de defeito, principalmente os dispositivos supercondutores, têm vindo a demostrar a sua viabilidade em redes de energia elétrica. Estes dispositivos são considerados invisíveis para a rede, quando em operação normal. Quando uma falha na rede ocorre, estes agem instantaneamente, retornando ao seu estado normal após a falha terminar. De modo a disseminar estas tecnologias, é necessário o desenvolvimento de ferramentas de projeto e modelação, de fácil uso. Essas ferramentas devem considerar as propriedades dos elementos que constituem os dispositivos de proteção. Por detrás dessas ferramentas de projeto, a integridade do limitador deve ser assegurada durante todo o seu funcionamento. Problemas relacionados com forças eletrodinâmicas desenvolvidas sob eventos de curto-circuito devem ser devidamente caracterizados, pois podem danificar os enrolamentos, e por sua vez o equipamento e afetar a rede elétrica. Nesta tese, é apresentada uma metodologia de projeto, que visa modelar e otimizar limitadores de corrente de defeito supercondutores, do tipo núcleos saturados. Esta metodologia considera as características de cada elemento constitutivo do limitador enquanto aborda os requisitos da concessionária da rede de distribuição de energia e as características da rede elétrica. Algoritmos genéticos são usados para otimizar os o limitador e o seu desempenho na rede elétrica. A fim de validar a metodologia atual, um limitador trifásico é projetado/otimizado, construído e ensaiado. É ainda realizada a análise das forças eletrodinâmicas desenvolvidas em fitas supercondutoras de um limitador de corrente de defeito, do tipo transformador, em condições de curto-circuito