Long-distance renewable hydrogen transmission via cables and pipelines

Intermittency is one of the main obstacles that inhibit the wide adoption of the renewable energy in the power sector. Small-scale fluctuations can be tackled by short-term energy storage system, whereas long-term or seasonal intermittencies rely on large-scale energy management solutions. Besides the supply and demand mismatch in temporal domain, renewable energy sources are usually far away from consumption points. To connect the energy sources to the demand cost-effectively, cable transmission is usually the default option, and considering the long distance, other emerging energy carriers such as hydrogen could be a feasible option. However, there is handful studies on the quantitative evaluation of the long-distance energy transmission cost. This paper investigated the economic feasibility of renewable energy transmission via routes of power cable and gas pipeline. In the direct power transmission case, renewable energy is transmitted via HVDC cable and then converted to hydrogen for convenient storage. The alternative case converts renewable energy into hydrogen at the source and transports the hydrogen in the gas pipeline to consumers. Existing data available from public domain are used for cost estimation. Results show that the improvements of capacity factor and transmission scale are the most cost-effective approach to make the renewable hydrogen economically viable. At 4000 km of transmission distance, renewable hydrogen LCOE of 7 US$/kg and 9 US$/kg are achievable for the corresponding optimum cases, respectively.     

Superconducting power transmission: The perils and promise

The development of bulk electricity transmission systems must be considered in the light of changing growth rates, increasing resistance to EHV overhead transmission and the tendency to concentrate generation in fewer sites. Helium-cooled, or superconducting, cables possess technical characteristics which will make them suitable as utility network components for power transmission over distances of ten to several hundred miles. These properties are illustrated by considering two applications in existing electrical networks. The first is a 43 mile system to transmit 4800 MVA and the second is a potential application under study in Pennsylvania to transmit 10,000 MVA over a distance of 350 miles or so. Helium-cooled versions of these transmission systems were designed to permit technical and economic evaluations.The major groups and institutions throughout the world engaged in the development of helium-cooled cables are listed and aspects of the technical approaches are briefly described.     

Superconducting power generation

With respect to the electric power industry, the superconducting AC generator has the greatest potential for large-scale commercial application of superconductivity. Such a machine should be able to convert mechanical energy to electric energy more efficiently and with greater economy of weight and volume than any other method. These advantages can be accrued at a scale of 1200 MVA output, with the added potential of operation at transmission line voltage and greater system stability. In the past, a great deal of R&D was done in this area, but the present industry trend to smaller machines has decreased this effort. Though the advantages diminish at the much smaller scale of 250 MVA, such machines still offer interesting possibilities. Superconducting synchronous generators with a superconducting adjustable field rotor keep power losses to a minimum since the field in the stator is phase-locked in synchronism with the rotating rotor field. The high magnetic flux density produced by a superconducting rotor field winding permits a great reduction in the amount of iron required in both the rotor and stator. This reduction introduces degrees of freedom not previously possible in generator or motor design. This article is written to help better perceive the technological potential of new developments     

Superconducting fault current limiters

Events in the power utility industry, such as deregulation, demands for better power quality and reliability, the advent of high temperature superconductivity, and the push to use technology to realize greater profits, have renewed interest in fault current limiters (FCL). Superconducting FCLs will become very important as the deregulation environment takes hold and utilities seek more efficient and cost-effective methods to couple grids, improve power quality, and delay expensive upgrades. The working principle and progress of superconducting FCLs is discussed in this article     

Superconducting magnetic energy storage

Superconducting magnetic energy storage (SMES) is an energy storage technology that stores energy in the form of DC electricity that is the source of a DC magnetic field. The conductor for carrying the current operates at cryogenic temperatures where it is a superconductor and thus has virtually no resistive losses as it produces the magnetic field. The overall technology of cryogenics and superconductivity today is such that the components of a SMES device are defined and can be constructed. The integrated unit appears to be feasible for some utility applications at a cost that is competitive with other technologies. SMES is the only technology based on superconductivity that is applicable to the electric utilities and is commercially available today. In addition to today's power quality application, the historical development of SMES starting with the concept of very large plants that would store hundreds of megawatt hours of energy and were intended for diurnal load leveling are described.     

Development of Superconducting AC Generator

The superconducting ac generator is expected to be the optimum choice among ac generation systems in the future because of its reduced size, weight, high efficiency, and its contribution to stability of power systems and higher generator terminal voltage. Conceptual design on a 2P-1000MVA class superconducting ac generator has been completed to clarify problems and to confirm advantages. Fundamental studies are performed on key technologies that have to be solved for realization of superconducting generators. As a summary of those fundamental studies, a scaled-down superconducting generator of 3000kVA capacity is constructed and tested. Also clarified are effects of major design parameters for commercial superconducting ac generators such as dimensions, reactances, and weight.     

Energy cables 2050: a futuristic view

The author describes how, given the intrinsic conductivity of polymer material and the availability of HV semiconductive power devices, an elegant new solution for the supply networks of electric power and data can be realized.     

Power cables in 21st century energy development

A brief overview is given which identifies and predicts some issues that will impact the use and development of cables over the next decades. Reliability of such cable systems will continue to be extremely important and will moderate the rate at which new technologies are introduced. The architecture of the distribution and transmission networks may change, for example, a wider use of DC cables would be one factor. A number of issues are identified and will require attention over the first part of the 21st Century. This will lead to more extensive use of underground and undersea cable systems. The following topics are covered: HVDC transmission; AC distribution and transmission cables; monitoring/diagnostic systems; multifunctional cables; and superconducting cables     

Superconducting coil fed by PEM fuel cell

Fuel cells are electrochemical energy converters which allow transformation of the chemical energy of a fuel to electricity through oxido-reduction reaction. The voltage of an elementary cell is usually near 1 V in open circuit and around 0.6 V in nominal conditions of power generation. Fuel cells are then by essence low voltage sources, so that for most practical applications, power management is carried out by electronic converters, allowing in particular to rise the voltage to usual application levels.     

超导磁体技术与磁约束核聚变

目的  磁约束核聚变是解决能源问题的有效途径之一。为了实现准稳态运行,超导磁体（特别是高场高温超导磁体）已成为未来托卡马克设计的首选方案。 方法  介绍了EAST的最新实验进展及未来研究计划,并从超导磁体技术方面总结了未来聚变装置CFETR的最新进展。 结果  2021年底,世界首个全超导托卡马克EAST（Experimental Advanced Superconducting Tokamak）成功实现1056 s长脉冲高参数等离子体运行,创造最长运行时间的世界记录。 结论  中国聚变工程试验堆（CFETR, China Fusion Engineering Test Reactor）的设计已经完成,它将填补国际热核聚变实验堆（ITER, International Thermonuclear Experimental Reactor）和示范堆（DEMO）间的空白。     

New method for derating cables in trays traversing firestops

An attempt is made to show that the Namgne method (R. Namgne and L. Ashbaugh, 1977) is simple and practical bt clarifying the analytic evaluation, and presenting a simpler step-by-step method for calculation of allowable ampacity. Using this method, a computer program has been developed to generate tables of correction factors which can be directly applied to the ICEA P-54-440 ampacities. Experimental results and the theoretical basis of method presented in references, are reviewed, and a comparison is made of the Namgne method with other approaches     

High voltage cables at the turn of the century

The author describes how power cable extruded dielectrics, by means of cross-linked polyethylene, are increasingly used at higher and higher voltage levels because of their favorable properties, such as dielectric losses, simple maintenance elimination of impregnant, etc     

Future proofing your generation system with power control andcommunication cables

Electric power generation facilities continue to undergo rapid technological change. Trends and anticipated developments in medium and high-voltage power, control and communication cables that will impact the design, construction, retrofit, and maintenance of power generation systems are discussed. Included is a discussion of the probable impact of optical fiber technology. Careful selection of the wire and cable used in power generation facilities will minimize future upgrade, retrofit, and maintenance costs. The proper application of wire and cable will also help assure trouble-free operation of present and future electrical power generating systems     

Recyclable insulation material for HVDC cables in Global Energy Interconnection

With the development of modern power systems, especially that of the global energy internet, high-voltage, direct current (HVDC) cable power transmission will play an important role in the future. The key problem of HVDC cable power transmission is the need for novel cable insulation materials that have high performance, recyclability, and higher working temperature to replace traditional crosslinked polyethylene. This paper investigates the thermal and electrical properties of polypropylene (PP)/Al₂O₃ nanocomposites as a potential recyclable HVDC cable insulation material. The developed nanocomposites exhibit excellent thermal and electrical properties with the introduction of Al₂O₃ nanoparticles. Particularly, the space charge accumulation is greatly suppressed.     

A Feasible Utility Scale Superconducting Magnetic Energy Storage Plant

This paper presents the latest design features and estimated costs of a 5000 MWh/1000 MW Superconducting Magnetic Energy Storage (SMES) plant. SMES is proposed as a commercially viable technology for electric utility load leveling. The primary advantage of SMES over other electrical energy storage technologies is its high net roundtrip efficiency. Other features include rapid availability and low maintenance and operating costs. Economic comparisons are made with other energy storage options and with combustion turbines.     

超导电缆的结构及特点

高温超导电缆(HTSC)有支撑体、超导层、绝缘层、屏蔽层和护套等组成,具有载流能力强、损耗低、尺寸小和无电磁泄漏等优点.商用化的超导带材有Bi-2223和YBCO两种,前者是目前超导电缆项目主要采用的材料,后者还在商业化途中.由于超导电缆的众多优势,各国都将其列为发展规划中.制造成本高、系统维护难是超导电缆发展的主要障碍,超导电缆的商业化还有待时日.     

超导限流器的多目标优化设计算法研究

为优化设计超导限流器参数,提出了超导限流器在电力网络中多目标优化设计的一种改进算法。即先基于MATLAB和PSCAD/EMTDC搭建超导限流器仿真模型,并利用有限元模型对其进行准确性校验;然后根据上海市某配电网搭建电力网络仿真模型,从而进行优化设计。在仿真计算过程中,考虑了短路类型和短路初始相位角所带来的影响,从而使超导限流器的优化参数可以通过三个优化目标和四个约束条件来获得。仿真结果表明,参数优化后的超导限流器能在不影响电网正常运行的同时有效限制短路电流。     

Evaporating system for cryogenic support of long length HTS power cables

The paper deals with an analysis of the results of theoretical and experimental research on an evaporating system for cryogenic support as supplied to long length thermostatting channels of high-temperature superconducting (HTS) cables and hybrid power transmission lines as well as thermal control systems for cryogenic components in aircraft fuel tanks during long-term spaceflights. Experimental evidence for nitrogen and hydrogen are presented here. The importance of such research for practical application in developing modern cryostatting systems has been highlighted.The design of an experimental hybrid power transmission line for studying thermostatting of superconducting power cables has been considered in the paper. The transmission line contains three sections with different types of thermal insulation and current leads providing high current supply to superconducting threads with minimum external heat inflow. The unique experimental data on heat inflows from the outer surface of the transmission line in different sections has been obtained by the authors. It is shown that it may be possible to compensate fully for external heat inflow to a cryogenic line as well as to lower the temperature of a cryogenic coolant in the section with an evaporating system for cryogenic support. In order to determine the possible length of the cryostatting work field of a long length superconducting cable, estimates of using liquid nitrogen and liquid hydrogen as a working fluid for various mass flow rates of the coolant feed have been made via the mathematical model describing physical processes in a thermostatting channel using an evaporating system for cryogenic support. Calculation data on changes in the length of the long length temperature cryostat, pressure and cooling capacity of the evaporating cryostat system has been obtained.     

Nonlinear planar secondary resonance analyses of suspended cables with thermal effects

Abstract

This paper deals with a geometrically nonlinear model of suspended cables in thermal environments. In particular, the secondary resonant behaviors with thermal effects are investigated and discussed analytically and numerically. First, considering the influence of temperature changes, a dimensionless coefficient is generated. The nonlinear dynamic equations of motion in thermal environments are established, and the governing PDEs are reduced to a set of ODEs by using the Galerkin procedure. Four super and sub-harmonic resonant cases are studied, and frequency responses equations and steady-state solutions for each case are obtained. Extensive numerical results show that the hardening/softening behaviors, the response amplitudes, the number of nontrivial solutions, the range of resonant responses, the jump points, and the peak values are all closely connected to temperature. In some specific warming/cooling conditions, the nonlinear system just shows linear vibration behaviors or even just opposite spring characteristics. The time–displacement curves and phase portraits are extremely sensitive to temperature changes, but the number of cluster points in Poincaré sections seem to be independent of temperature changes.     

饱和铁心型超导限流器应用技术研究

短路电流水平越来越大对电力系统的安全稳定运行造成了极大的威胁。饱和铁心型超导限流器具有稳态阻抗小、损耗小、恢复时间短、限流效果好等优点,是限制电力系统短路电流的理想设备之一。介绍了饱和铁心型超导限流器的工作原理,阐述了其国内外发展现状,并在此基础上分析了其应用于电力系统应考虑的重点问题。