Energy from wind – perspectives and research needs

Wind energy will provide a major share of our future energy supply, and, due to the possibility of going offshore, has an immense additional potential for power supply. To use wind energy in a reliable way, much research work still has to be done. One of these fields is the evaluation of wind energy in terms of sustainability. The results of Life Cycle Assessments (LCA) show that wind energy converters have a short energy payback time and low emissions, even in comparison with other renewable energy systems. Another field of research is the creation of optimisation models which can provide answers to questions concerning the future power generation mix. The opportunity exists, now that a great part of the over-aged conventional power plant stock has to be replaced, to adapt the power plant mix to an expanded share of wind energy. Within this mix, electric storage may play a major role. The results of the optimisation models indicate that storage sites alone will not be profi enough to reduce operating costs of the modelled system, and that this will only be possible through the option of energy trading. Hence there are interesting instruments in the deregulated energy market, especially for electric-power commodity exchanges like the EEX.     

Hierarchical distributed stabilization of power networks

Large fluctuation of electric power due to high penetration of renewable energy sources such as photovoltaic and wind power generation increases the risk to make the whole power network system unstable. The conventional frequency control called load frequency control is based on PID (proportional-integral-derivative) control or more advanced centralized and decentralized/distributed control. If we could more effectively use information on the state of the other neighbor generators, we can expect to make the whole system more robust against the large frequency fluctuation. This paper proposes a fundamental framework towards the design of hierarchical distributed stabilizing controllers for a network of power generators and loads. This novel type of distributed controller, composed of a global controller and a set of local controllers, takes into account the effect of the interaction among the generators and loads to improve robustness for the variation of locally stabilizing controllers.     

Kolmogorov spectrum of renewable wind and solar power fluctuations

With increasing the contribution of renewable energies in power production, the task of reducing dynamic instability in power grids must also be addressed from the generation side, because the power delivered from such sources is spatiotemporally stochastic in nature. Here we characterize the stochastic properties of the wind and solar energy sources by studying their spectrum and multifractal exponents. The computed power spectrum from high frequency time series of solar irradiance and wind power reveals a power-law behaviour with an exponent ～ 5/3 (Kolmogorov exponent) for the frequency domain 0.001?Hz < f < 0.05?Hz, which means that the power grid is being fed by turbulent-like sources. Our results bring important evidence on the stochastic and turbulent-like behaviour of renewable power production from wind and solar energies, which can cause instability in power grids. Our statistical analysis also provides important information that must be used as a guideline for an optimal design of power grids that operate under intermittent renewable sources of power.     

Combustion processes for carbon capture

A review of the technologies for coal-based power generation closest to commercial application involving carbon capture is presented. Carbon capture and storage (CCS) developments are primarily adaptations of conventional combustion systems, with additional unit operations such as bulk oxygen supply, CO₂ capture by sorbents, CO₂ compression, and storage. They use pulverized coal combustion in entrained flow—the dominant current technology for coal-based power, or gasification in entrained flow, although similar concepts apply to other solid-gas contacting systems such as fluidized beds. Currently, the technologies have similar generation efficiencies and are associated with efficiency penalties and electricity cost increases due to operations required for carbon capture. The R&D challenges identified for the combustion scientist and engineer, with current understanding being detailed, are those of design, optimisation and operational aspects of new combustion and gasification plant, controlling the gas quality required by CCS related units and associated emission compliance, and gas separations. Fundamental research needs include fuel reactions at pressure, and in O₂/CO₂ atmospheres, as few studies have been made in this area. Laboratory results interpreted and then included in CFD models of combustion operations are necessary. Also identified, but not detailed, are combustion issues in gas turbines for IGCC and IGCC-CCS. Fundamental studies should be a component of pilot-plant and demonstrations at practical scale being planned. Concepts for new designs of combustion equipment are also necessary for the next generation of technologies. The challenges involved with the design and operation of these integrated systems, while supplying electricity on demand, are considerable.     

Analysis of renewable energy sources and electric vehicle penetration into energy systems predominantly based on lignite

We consider an integration of renewable energy into transport and electricity sectors through vehicle to grid (V2G) technologies for an energy system that is predominantly based on lignite. The national energy system of Macedonia is modeled using EnergyPLAN which integrates energy for electricity, transport and heat, and includes hourly fluctuations in human needs and the environment. We show that electric-vehicles can provide the necessary storage enabling a fully renewable energy profile for Macedonia that can match the country’s growing demand for energy. Furthermore, a large penetration of electric vehicles leads to a dramatic reduction of 47% of small particles and other air pollutants generated by car traffic in 2050.     

云计算技术在未来智能电网信息处理平台中的应用

未来的电网将会是一个高度自动化、智能化的电网,如此一个庞大、复杂的系统从发电、输电一直到变、配、用电的过程时刻都会生成海量的电能信息及设备运行状态数据,这就需要一个强有力的信息处理平台作为支撑,且这个平台应具有对海量数据的可靠存储、准确分析、实时同步更新及共享的功能,尤其是音视频等异构数据的分析与处理.云计算技术在大数据处理中具有得天独厚的优势,本文将云计算技术引入到未来智能电网的信息处理平台的建设中,针对未来智能电网信息处理平台的各项功能需求,对比目前电网信息处理平台的诸多瓶颈进行深层次的探讨,证明了将云计算技术应用到未来智能电网信息处理平台中的可行性。     

Electrostatic ultra-low-energy antiproton recycling ring

There is a strong need to push forward developments in the storage and control of ultra-low-energy antiproton beams to enable important scientific research. To this end, a small electrostatic ring, and associated electrostatic acceleration section, is being designed and developed by the QUASAR group. The ring will be placed on the MUSASHI beamline at the CERN-AD. It will serve as a prototype for the future ultra-low energy storage ring (USR), to be integrated at the facility for low-energy antiproton and ion research (FLAIR) and will enable various components of the USR to be tested and optimised. A reaction microscope will be integrated in the ring to enable partial ionisation cross section measurements to be made. This small recycler ring will be unique due to its combination of size, electrostatic nature and energy and type of circulating particles (ca 3?C30 keV antiprotons). A short electrostatic accelerating section is also being developed, which will be placed between the beamline and the ring to accelerate the antiprotons from the trap extraction energy (typically 250 eV) to the final required (re-circulating) energy. The AD recycler project will be described, including ring design, accelerating injection section and the inclusion of a reaction microscope and the experiments it will enable.     

恒功率输入恒流输出的电容器充电电源

常规恒流充电电源输入端的功率随着输出电压的升高而逐渐增加,充电结束时输入端的功率由最大值迅速降为0,不仅需要电网能够提供近2倍于平均值的峰值功率,还会造成电网电压的波动,特别是在重复频率与工频接近的大功率应用场合时,可能造成电网滤波系统的振荡,影响供电可靠性和干扰其他用电设备。提出了一种带有储能环节的电路拓扑,使得在对负载恒流充电期间,输入端的功率保持在平均功率水平。充分利用了串联谐振电路断续工作模式的特点,无需辅助变换器,仅通过双向开关对电流的控制,可将充电初期多余能量存储到储能环节,并在充电后期逐渐将此能量向负载释放,在充电启停时刻储能环节的净增能量为0。将上述拓扑电路添加到基于DC-link的恒流充电电源中,进行了分析和控制参数推导,并在输出电流8 A、最高输出电压5 kV的电源上进行了实验,结果表明:充电期间直流母线提供的电流基本稳定,幅值为常规方案中最大母线电流的一半左右。     

Investigation of plasma opening switch conduction and openingmechanisms

Plasma opening switch techniques have been developed for pulsed power applications to exploit the advantages of electrical energy storage in a vacuum inductor compared to conventional, capacitive-based energy storage. Experiments are described that demonstrate the successful application of these techniques in conduction time ranges from 50 ns to over 1 μs. Physics understanding of the conduction and opening mechanisms is far from complete; however, many insights have been gained from experiments and theory. Measurements of current distribution, plasma density, and ion emission indicate that conduction and opening mechanisms differ for the 50 ns and 1 μs conduction times. For the 50 ns conduction time case, switching begins at a current level close to the bipolar emission limit, and opening could occur primarily by erosion. In the 1 μs conduction time case, limited hydrodynamic plasma displacement implies far higher plasma density than is required by the bipolar emission limit. Magnetic pressure is required to augment erosion to generate the switch gap inferred from experiments     

Evolution of pulse shortening research in narrow band, high powermicrowave sources

The achievements resulting from the application of advanced pulsed power to the generation of high power microwaves (HPM) have included the generation of multi-gigawatt pulses of RF energy. The power achievable is orders of magnitude greater than conventional microwave sources can generate. However, the introduction of the HPM technology into logical applications has been limited to date due to the phenomenon of pulse shortening in which the RF pulse terminates before the pulse power source used to produce it. Conventional microwave tubes can generate a few to 10 MW of power with pulsewidths of many microseconds when required. High power microwave sources can produce gigawatts of power, but only for relatively short pulsewidths, typically tens to hundreds of nanoseconds. An international effort during the past few years has generated important new discoveries toward the elimination of pulse shortening. Some of the new techniques have the potential for helping the conventional tube industry as well as being practical for high power microwave sources. This paper reviews the pulse shortening problem, its causes, and the worldwide scope and direction of research conducted to date to resolve it. The paper also discusses the potential remedies for the problem and recommends a course of research to further progress on the issue     

The Effects of the Pion String at Heavy ion Collisions

We study the possible signals of the pion string associated with the QCD chiral phase transition in LHC Pb–Pb collision at energy s=5.5 TeV.We follow the Kibble–Zurek mechanism to discuss the production and evolution of the pion string.We will show that if the QCD chiral phase transition really takes place in the LHC Pb-Pb collision process and the phase transition is in the second order,the pion string will be inevitably produced and subsequently decay.The main effect of this phenomenon is that there is a generation of a large number of pions in the final state produced by the decay of the pion string, and these pions are mostly distributed in a low momentum region with p～143MeV; also there are lots of neutral pions distributed in a low momentum region with the mean momentum at p～21MeV.     

Experimental studies of using wireless energy transmission for powering embedded sensor nodes

A major challenge impeding the deployment of wireless sensor networks for structural health monitoring (SHM) is developing a means to supply power to the sensor nodes in an efficient manner. In this paper, we explore possible solutions to this challenge by using a mobile-host based wireless energy transmission system to provide both power and data interrogation commands to sensor nodes. The mobile host features the capability of wirelessly transmitting energy to sensor nodes on an as-needed basis. In addition, it serves as a central data repository and processing center for the data collected from the sensing network. The wirelessly transmitted microwave energy is captured by a receiving antenna, transformed into DC power by a rectifying circuit, and stored in a storage medium to provide the required energy to the sensor node. The application of wireless energy transmission is targeted toward SHM sensor nodes that have been recently developed by the authors, which can be used to collect peak mechanical displacements or piezoelectric impedance measurements. This paper will describe considerations needed to design such energy transmission systems, experimental procedure and results, method of increasing the efficiency, energy conditioning circuits and storage medium, and target applications. Experimental results from a field test on the Alamosa Canyon Bridge in southern New Mexico will also be presented.     

微电网动态调度模型

微电网系统中可再生能源出力和建筑负荷均具有随机特性,使得传统方法难以描述其动态特征,随着可再生能源的大量接入,微电网系统结构也愈趋复杂化,本文基于Modelica非因果建模语言对含随机参数的复杂系统进行动态描述,实现对可再生能源发电、储能元件和可控负荷的耦合建模,并验证其准确性。运用动态模拟结合多种群遗传算法对典型微电网系统进行24 h运行策略调整,结果验证了该模型与动态调度方法的有效性。     

Quantum critical behavior of the cluster glass phase

In disordered itinerant magnets with arbitrary symmetry of the order parameter, the conventional quantum critical point between the ordered phase and the paramagnetic Fermi liquid (PMFL) is destroyed due to the formation of an intervening cluster glass (CG) phase. In this Letter, we discuss the quantum critical behavior at the CG-PMFL transition for systems with continuous symmetry. We show that fluctuations due to quantum Griffiths anomalies induce a first-order transition from the PMFL at T = 0, while at higher temperatures a conventional continuous transition is restored. This behavior is a generic consequence of enhanced non-Ohmic dissipation caused by a broad distribution of energy scales within any quantum Griffiths phase in itinerant systems.     

Self-organized synchronization and voltage stability in networks of synchronous machines

The integration of renewable energy sources in the course of the energy transition is accompanied by grid decentralization and fluctuating power feed-in characteristics. This development raises novel challenges for power system stability and design. We investigate power system stability from the viewpoint of self-organized synchronization aspects. In this approach, the power grid is represented by a network of synchronous machines. We supplement the classical Kuramoto-like network model, which assumes constant voltages, with dynamical voltage equations, and thus obtain an extended model, that incorporates the coupled categories voltage stability and rotor angle synchronization. We compare disturbance scenarios in small systems simulated on the basis of both classical and extended model and we discuss resultant implications and possible applications to complex modern power grids.     

News and Views: Nuclear Power in Brazil

No energy, whether renewable, clean or known by any other name can possibly be relied upon as the only solution for ensuring a supply of electricity compatible with a nation’s economic and social development. Brazilian consumption and installed capacity of electric power generation per capita indices are still inadequate and below the world average—this crucial fact must be considered. It obliges Brazil to take the most advantage of all resources available to increase its electricity generation capacity as rapidly as possible, thereby enabling consumption to reach levels compatible with the quality of life the Brazilian population aspires to. Planning of a country’s electric system requires efficient management of a diversified portfolio of energy sources. In Brazil, hydroelectricity will continue for many years yet to be the main component of its portfolio of electric power generation sources, but it must be supplemented by thermal sources—uranium, coal, biomass, natural gas, and oil by-products derived from petroleum—in this order of importance, keeping in mind aspects related to local availability, cost, environmental impacts, and use in other applications.     

Design,manufacture and testing of a closed cycle thermosyphon rankine engine

The Thermosyphon Rankine Engine (TSR) is a recent concept for power generation using solar or other available low grade heat sources. The basis of the engine is the modification of a heat pipe, with its excellent heat and mass transfer characteristics, to incorporate a turbine, thereby making the system into a Rankine Cycle Engine.The TSR is directed towards power production from solar ponds, geothermal energy and heat produced by solar collectors, as well as for waste heat utilisation for electrical power generation.A theoretical formulation and results from experiments on prototype units are presented. Based on the results, it is concluded that the TSR engine may play an important role for conversion into electrical energy of thermal energy produced by conventional solar collectors, geothermal sources and waste heat.     

Decompositions of injection patterns for nodal flow allocation in renewable electricity networks

The large-scale integration of fluctuating renewable power generation represents a challenge to the technical and economical design of a sustainable future electricity system. In this context, the increasing significance of long-range power transmission calls for innovative methods to understand the emerging complex flow patterns and to integrate price signals about the respective infrastructure needs into the energy market design. We introduce a decomposition method of injection patterns. Contrary to standard flow tracing approaches, it provides nodal allocations of link flows and costs in electricity networks by decomposing the network injection pattern into market-inspired elementary import/export building blocks. We apply the new approach to a simplified data-driven model of a European electricity grid with a high share of renewable wind and solar power generation.     

The effect of interaction time and saturation of rock on specific energy in ND:YAG laser perforating

Laser perforating in oil and gas wells is a new scientific approach to the generation of uniform holes at a selected pitch to increasing the permeability of rocks. The influence of laser irradiation time and rock saturation by water and heavy oil on the specific energy, the energy required to remove the unit weight of rock, used during Nd:YAG laser perforating. The results show that an increase in the laser irradiation time increases the depth of the rock hole as well as the specific energy used, with a nonlinear relationship. Here, the estimated equation of rate of penetration as a function of the specific energy (SE) is free from saturation effects. The type of saturation influences the specific energy; the amount of SE required for water saturated samples is more than that required for the heavy oil saturated samples, and heavy oil saturated samples needed more SE than the dry samples.     

LD侧面抽运Nd：YAG陶瓷激光器运转条件下归一化热参数优化理论及实验研究

考虑激光提取对介质内非辐射跃迁的抑制作用，建立和完善LD侧面抽运Nd：YAG陶瓷激光器运转条件下增益介质的发热模型，通过实验测量激光器斜率效率和增益介质吸收的抽运功率来推导出归一化热参数.通过归一化热参数，讨论了影响Nd：YAG陶瓷介质内热沉积的主要因素，研究结果表明：增益介质内热沉积对激光提取效率、交叠效率以及掺杂浓度的变化比较敏感.为有效减少热沉积，对所研究的掺杂原子百分比浓度为1.0%的Nd：YAG陶瓷多模激光器的输出耦合镜进行优化选择，激光提取效率提高到0.905，归一化热参数降低到0.474.研究结果可为进一步研究陶瓷激光器中热效应以及冷却方案设计等提供一定参考. 关键词： 热沉积 归一化热参数 Nd：YAG陶瓷