Emergence of a phase transition for the required amount of storage in highly renewable electricity systems

Due to global environmental concerns, our electricity supply will transform from mostly conventional power generation to mostly fluctuating renewable power generation. The transition will require combined backup from conventional sources and storage. A phase transition emerges during the ramp-up of the required amount of storage, with renewable penetration being the control parameter and average relative storage filling level being the order parameter. A singularity appears for the required storage energy capacity at a renewable penetration determined by the parameters of the storage. For an ideal storage with no roundtrip losses the transition occurs at 100% renewable penetration. Moreover, the required storage energy capacity is strongly enhanced by temporal correlations on the synoptic weather time scale. A Markov process is proposed, which reproduces these findings.     

太阳能光伏-温差发电驱动的新型冰箱模型设计与热力学分析

结合太阳能电池温度特性和温差发电特点,设计了一套新的太阳能光伏发电-温差发电驱动的冰箱模型,该模型包括太阳能光伏电池、半导体温差发电模块、电源控制系统等.根据负载用电需求,做出了光伏发电系统的设计方案.采用热力学基本理论,对该模型进行了工作效率及 火 用 效率的分析.结果发现:能效比COP达到了2.73(一般 冰箱COP为2左右), 火 用 效率也达到42.5%.同时,该系统模型环境效益明显,可以减排CO₂ 1394.2 kg,SO₂     

Models for the modern power grid

This article reviews different kinds of models for the electric power grid that can be used to understand the modern power system, the smart grid. From the physical network to abstract energy markets, we identify in the literature different aspects that co-determine the spatio-temporal multilayer dynamics of power system. We start our review by showing how the generation, transmission and distribution characteristics of the traditional power grids are already subject to complex behaviour appearing as a result of the the interplay between dynamics of the nodes and topology, namely synchronisation and cascade effects. When dealing with smart grids, the system complexity increases even more: on top of the physical network of power lines and controllable sources of electricity, the modernisation brings information networks, renewable intermittent generation, market liberalisation, prosumers, among other aspects. In this case, we forecast a dynamical co-evolution of the smart grid and other kind of networked systems that cannot be understood isolated. This review compiles recent results that model electric power grids as complex systems, going beyond pure technological aspects. From this perspective, we then indicate possible ways to incorporate the diverse co-evolving systems into the smart grid model using, for example, network theory and multi-agent simulation.     

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.     

芯片式流通池顺序注射可更新表面反射光谱分析系统的研究

本文提出一种用于流动注射或顺序注射分析进样可更新表面反射光谱法检测的芯片式流通池 ,并将此流通池与顺序注射系统及检测系统相匹配。流通池采用三层组合结构 ,流通池通道刻在中间层的硅橡胶膜上 ,多孔滤层横嵌于硅橡胶膜上的通道处以实现对微珠的截留。流通池检测窗口面积约为 3 6mm2 ,填充微珠体积 2 2 μL ,微珠层厚度 6 0 0 μm。与流通池相接的多股双岔光纤分别与光源、检测器相耦合 ,以实现对微珠表面的反射光谱检测。工作中采用Cr(Ⅵ )与固定在PolysorbC 18微珠表面的DPC的显色反应做为模型系统对流通池和仪器系统进行优化。微珠表面反射光谱在 5 40nm处检测 ,Cr(Ⅵ )采样量 10 0 μL ,载流流速为 1 0mL·min- 1 时 ,线性范围为 0～ 0 6 μg·mL- 1 Cr(Ⅵ ) ,检测限为 6ng·mL- 1 ,分析精度RSD(n =11)为1 5 % ,进样频率 6 4样·h- 1 。文中讨论了分析体系的设计思路 ,微珠层厚度、微珠注入量、载流流速、采样量等因素对检测的影响     

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.     

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.     

一级相变材料Mn1.2Fe0.8P0.4Si0.6的热磁发电性能

本文报道把热能直接转换电能的热磁发电技术所用一级相变新材料Mn_1.2Fe_0.8P_0.4Si_0.6的磁性和热磁发电性能.用高能球磨机械合金化技术和固相烧结合成方法制备了Mn_1.2Fe_0.8P_0.4Si_0.6化合物.磁性测量结果表明,该化合物呈现从铁磁状态变为顺磁状态的一级相变,居里温度为337K,并伴随巨大的磁化强度的变化.根据该材料的这一特性,设计制作了热磁发电演示装置,测定了热流引起材料的相变而产生的电流,并研究了固定磁场中热致磁转变产生的电流随热流温度和样品质量的变化.研究结果表明Mn_1.2Fe_0.8P_0.4Si_0.6化合物具有很好的热磁发电性能,可作为热磁发电材料.     

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.     

Power management in heterogeneous networks with energy harvesting base stations

In this paper, heterogeneous cellular networks (HCNs) with base stations (BSs) powered from both renewable energy sources and the grid power are considered. Based on a techno-economic analysis, we demonstrate that by controlling both transmit power and stored energy usage of BSs, energy costs can be effectively reduced. Specifically, we propose a two-stage BS operation scheme where an optimization and control subproblem is solved at each stage, respectively. For the first subproblem, transmit power of BSs is adjusted while quality of service (QoS) experienced by users is preserved. In the second subproblem, we consider the strategic scheduling of renewable energy used to power the BSs. That is, harvested energy may be reserved in the battery for future use to minimize the cost of on-grid power that varies in real-time. We propose: (1) an optimization approach built on a lattice model with a method to process outage rate constraint, and (2) a control algorithm based on nonlinear model predictive control (NMPC) theory to solve the two subproblems, respectively. Simulation results include a collection of case studies that demonstrate as to how operators may manage energy harvesting BSs to reduce their electricity costs.     

High peak power and sub-picosecond Fourier-limited pulse generation from passively mode-locked monolithic two-section gain-guided tapered InGaAs quantum-dot lasers

We report on the development of a new generation of high-power ultrashort pulse quantum-dot lasers with tapered gain section. Two device designs are proposed and fabricated, with different total lengths and absorber-to-gain-section length-ratios. These designs have been informed by numerical simulations of the dynamic mode-locking regimes and their dependence on the structural parameters. One device design demonstrated a record-high peak power of 17.7 W with 1.26 ps pulse width and a second design enabled the generation of a Fourier-limited 672 fs pulse width with a peak power of 3.8 W. A maximum output average power of 288 mW with 28.7 pJ pulse energy was also attained. In addition, the integrated timing jitter of 2.6 ps and far-field patterns are demonstrated.     

新型多能源互补系统的热力经济性分析

本文对SOLRGT系统（一种新型的中低温太阳能与化石燃料互补的动力系统）进行了热力经济性分析。该系统基于化学回热循环,通过中低温太阳能品位的间接提升、与先进燃气轮机的集成,实现中低温太阳能的高效、低成本热功转换以及和化石燃料的综合梯级利用。本文将其与同等输入下的两种单输入发电系统进行对比分析,研究表明：基本工况下,SO...     

A generation-attraction model for renewable energy flows in Italy: A complex network approach

In recent years, in Italy, the trend of the electricity demand and the need to connect a large number of renewable energy power generators to the power-grid, developed a novel type of energy transmission/distribution infrastructure. The Italian Transmission System Operator (TSO) and the Distribution System Operator (DSO), worked on a new infrastructural model, based on electronic meters and information technology. In pursuing this objective it is crucial importance to understand how even more larger shares of renewable energy can be fully integrated, providing a constant and reliable energy background over space and time. This is particularly true for intermittent sources as photovoltaic installations due to the fine-grained distribution of them across the Country. In this work we use an over-simplified model to characterize the Italian power grid as a graph whose nodes are Italian municipalities and the edges cross the administrative boundaries between a selected municipality and its first neighbours, following a Delaunay triangulation. Our aim is to describe the power flow as a diffusion process over a network, and using open data on the solar irradiation at the ground level, we estimate the production of photovoltaic energy in each node. An attraction index was also defined using demographic data, in accordance with average per capita energy consumption data. The available energy on each node was calculated by finding the stationary state of a generation-attraction model.     

感应耦合非热等离子体催化转化二氧化碳

射频感应耦合等离子体能够在室温条件下选择活化并分解二氧化碳，本文通过调控等离子体放电条件(气体流量、放电频率等)获得了较高的一氧化碳产率. 研究发现网状金属催化剂在二氧化碳等离子体中能促进氧原子的复合反应，从而有效抑制其与目标产物一氧化碳的逆反应，提升反应整体效率. 本文为实时转化过剩的可再生电能(来自太阳能、风能、潮汐能等)为高附加值一氧化碳中的化学能提供了一个可行的方案.     

基于LR305的平面荧光太阳能聚光波导研制

光伏发电是目前太阳能最佳的利用方式之一,但发电成本高。利用聚光结构提高光的转换和收集效率,是提高太阳能电池效率、减少电池用量、降低光伏发电系统成本的重要途径。以Lumogen F Red 305 (LR305) 染料作为荧光材料,将其掺杂到PMMA中,通过本体聚合法制作出尺寸为50 mm×50 mm×5 mm的PMMA平面荧光太阳能聚光波导,对其光学特性进行表征,同时将太阳能电池粘贴到聚光波导的输出端面,通过测试平面荧光太阳聚光波导对太阳能电池性能的影响研究了荧光太阳能聚光波导的聚光特性。     

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.     

Cherenkov superradiance with a peak power higher than electron flow power

The results of theoretical and experimental studies allowing the use of Cherenkov superradiance for the generation of electromagnetic pulses with a peak power higher than electron flow power are reported. For an injection current of 2.6 kA and a particle energy of 330 keV, the power of a microwave pulse with a carrier frequency of 9.3 GHz and a duration of 0.5 ns attained 1.2 GW.     

静电式同位素辐射能量收集器的研究

针对目前无线传感网络节点对长寿命微能源的需求,提出了将同位素辐射能量转换为电能的静电式振动能量收集原理.该原理利用同位素63Niβ辐射能实现平行板悬浮-质量块结构的自由阻尼振动,并通过可变电容电路实现充-放电振荡循环,从而实现电能的转换.通过分析运动状态和能量转化过程,给出了结构的运动状态和能量输出方程,并使用Matlab/Simulink对输出特性进行了数值模拟和基于Ansys的结构优化设计.根据仿真和优化的结构尺寸设计出了满足最大平均输出功率的微电子机械器件结构.结果表明:所设计的结构在一阶固有频率为500 Hz,两极板间距离为75μm,外接电阻为90 k?时平均输出功率最大为0.416μW,转化效率8.25%.     

Solar thermal power plants

The solar thermal power plant technology, the opportunities it presents and the developments in the market are outlined. The focus is on the technology of parabolic trough power plants, a proven technology for solar power generation on a large scale. In a parabolic trough power plant, trough-shaped mirrors concentrate the solar irradiation onto a pipe in the focal line of the collector. The thermal energy thus generated is used for electricity generation in a steam turbine. Parabolic trough plants can be combined with thermal storage and fossil or biomass fired heat exchangers to generate electricity even when the sun is not shining. Solar Millennium AG in Erlangen has developed the first power plant of this kind in Europe. After two years of construction the plant started operation in Southern Spain in 2008. This one and its sister projects are important steps leading the way for the whole market. The paper also covers the technological challenges, the key components used and the research and development activities concerning this technology. Solar thermal power plants are ideal for covering peak and medium loads in power grids. In hybrid operation they can also cover baseload. The Solar Chimney power plant, another striking technology for the conversion of solar into electric energy, is described briefly. The paper concludes with a look at the future – the import of solar energy from the deserts of North Africa to central Europe.     

Module-level design and characterization of thermoelectric power generator

Thermoelectric power generation provides us the unique capability to explore the deep space and holds promise for harvesting the waste heat and providing a battery-free power supply for IoTs. The past years have witnessed massive progress in thermoelectric materials, while the module-level development is still lagged behind. We would like to shine some light on the module-level design and characterization of thermoelectric power generators (TEGs). In the module-level design, we review material selection, thermal management, and the determination of structural parameters. We also look into the module-level characterization, with particular attention on the heat flux measurement. Finally, the challenge in the optimal design and reliable characterization of thermoelectric power generators is discussed, together with a calling to establish a standard test procedure.