The effectiveness of a strategic reserve in the presence of a high portfolio share of renewable energy sources

To ensure sufficient investment in electricity generation capacity, mechanisms such as strategic reserves are being considered or already implemented. We analyze the effectiveness of a strategic reserve in the presence of a growing portfolio share of renewable energy sources (RES) with EMLab-Generation, an agent-based electricity market model. A strategic reserve can stabilize investment, but within limits. Uncertainty regarding future demand may cause the market to become instable, potentially leading to periods with very high electricity prices. In the presence of a large share of variable renewable energy sources, the reserve design should be adjusted or replaced by an alternative capacity mechanism.     

A coordinated strategic reserve to safeguard the European energy transition

In Germany and beyond, various capacity mechanisms are currently being discussed with a view to improving the security of electricity supply. One of these mechanisms is a strategic reserve that retains generation capacity for use in times of critical supply shortage. We argue that strategic reserves have specific advantages compared to other capacity mechanisms in the context of the European energy transition. To date, however, the debate on capacity mechanisms has largely been restricted to national contexts. Against this background, we discuss the feasibility and potential benefits of coordinated cross-border strategic reserves to safeguard electricity supply and aid the energy transition in Germany and neighboring countries at large. Setting aside strategic reserve capacity which is deployed only in the event of extreme supply shortages could improve the security of electricity supply without distorting the EU's internal electricity market. In addition, overall costs may decrease when reserve procurement and activation are coordinated among countries, particularly if combined with flow-based market coupling.     

Impact of tertiary reserve sharing in Portugal

Ancillary services play a fundamental role in the operation of electricity systems. In the Iberian Peninsula, since mid-2014, ancillary services have gained a transnational dimension, namely through the introduction of cross-border balancing replacement reserves between the Portuguese and the Spanish Transmission System Operators (TSOs). This paper evaluates the impact of replacement reserves on the Portuguese electricity system, from the onset of this mechanism until the end of 2017, as a new contribution to earlier studies. It also describes the pecuniary impact of tertiary transactions, the identification, and categorization of possible different scenarios of tertiary mobilization, and the respective impact on the internal tertiary mobilization. On the one hand, the Iberian electricity system is one of the most influenced by a high penetration of intermittent renewables, and therefore one of the best candidates to experience increased benefits from the platform. On the other hand, the Portuguese TSO is one of the most peripheral TSOs in Europe that benefits more from the market integration in various dimensions of the electricity sector.     

A simplified method for collapse capacity assessment of moment-resisting frame and shear wall structural systems

A simplified methodology for predicting the median and dispersion of collapse capacity of moment-resisting frame and shear wall structural systems subjected to seismic excitations is proposed. The method is based on nonlinear static (pushover) analysis. Simple mathematical models denoted as “generic structures” are utilized to model moment-resisting frames and shear walls. After examining a wide range of structural parameters of the generic structures, a comprehensive database of collapse fragilities and pushover curves (using ASCE 7-05 lateral load pattern) are generated. Based on the obtained pushover curves, closed-form equations for estimation of median and dispersion of building collapse fragility curves are developed using multivariate regression analysis. Comparing the estimates of the median collapse capacity calculated from the closed-form equations with the actual collapse capacities determined from nonlinear response-history analysis indicates that the simplified methodology is reliable. The effectiveness of this methodology for predicting the median collapse capacity of frame and wall structures is further demonstrated with two case studies of structural systems designed based on current seismic provisions.     

抗剪切和抗冲切截面高度影响系数取值的研究

在总结规范抗剪切和抗冲切承载力高度截面影响系数取值方法基础上,对二者进行了比较和分析,得出了实用的计算公式,将二者在形式上统一起来;并分析了新公式对抗冲切承载力值的影响程度,证明了其可行性。     

密砂中圆形锚上拔承载力尺寸效应分析

通过模型试验和有限单元法分析了密砂中圆形锚板上拔承载力的尺寸效应问题。分别对直径为20,50,400 mm的锚板在埋深比为2～6时进行拉拔试验,获得上拔力和位移关系曲线及极限上拔力。基于不同埋深比时板径与上拔承载力系数关系曲线,可发现:相同埋深比时,随着锚板直径增加,上拔承载力系数逐渐减小;且随着埋深比增加,此现象愈明显。考虑密砂强度随应变发展而出现的软化现象,对理想弹塑性Mohr-Coulomb模型进行改进,基于改进的模型对上述12个拉拔试验进行有限元数值模拟,同时与理想弹塑性模型模拟结果进行比较。结果表明:理想弹塑性模型严重高估锚板上拔承载力,而考虑土体软化的模型能够模拟锚板上拔过程中破坏面上土体强度逐渐发挥的过程,计算得到的极限承载力与试验结果吻合较好。尺寸效应产生的原因一方面由于应力水平对土体强度的影响,另一方面由渐进破坏引起;埋深比越大,随着锚板直径增加,周围土体依次进入破坏的过程愈加明显。     

砂土地基承载力离心模型试验中的粒径效应研究

通过对原型的模拟结果进行总结,得出对于承载力试验只要离心试验中的模型基础宽度与重力场试验中的不同,离心模型试验结果总大于重力场试验结果,即离心试验中总是存在粒径效应问题。随着模型基础宽度与地基材料平均粒径比值的增大,离心试验结果逐渐接近重力场试验结果;当比值足够大时,离心试验结果趋于稳定且与重力场试验结果之差可忽略不计。因此,可以利用模型的模拟的方法,讨论离心模型试验中的粒径效应问题。在一系列砂土地基上条形基础地基承载力的离心模型试验中,使模型基础宽度与地基材料平均粒径的比值在较大范围内变化,即最大比值为最小比值的5倍,且其变化范围的上限达291。基于试验结果导入评价粒径效应对试验结果影响程度的指标,定量地讨论了离心模型试验中的粒径效应问题。本试验结果表明,当模型基础宽度与地基材料平均粒径的比大于233时,粒径效应对试验结果的影响小于1%,基本可忽略不计。     

粉喷桩单桩承载力时间效应试验研究

结合粉喷桩单桩承载力影响因素,针对其成桩过程中单桩承载力随时间增长而逐渐增大的现象,通过水泥土室内强度试验和不同龄期的单桩载荷试验,得出了单桩承载力变化规律,对工程实践具有指导作用。     

Integration of Demand Response in Electricity Market Capacity Mechanisms

Ensuring that the power system meets demand peaks is a key challenge of liberalized markets. On the supply side, capacity can be supported through a Capacity Remuneration Mechanism (CRM). On the demand side, Demand Response (DR) technologies can be deployed. We find that while all traditional generation should receive the same payment, capacity payments for DR technologies should gradually decrease based on operators’ position in the load-shedding order. We observe that all CRM schemes currently implemented provide inadequate incentives to non-price responsive DR and propose to adjust payments to DR units as a function of their expected activation periods.     

多中心跨境城市一区域的多层级管治——以大珠江三角洲为例

在全球化和区域化并驾齐驱的格局下,全球城市一区域（Global City-Region）日益成为全球经济增长的核心动力,跨境区域（CBRs：Cross-BorderRegions）大量涌现。近年来欧盟国家有关大都市区的研究揭示了多中心（Polycentric）格局和区域融合中多层级管治（multi-level governance）的形态,但罕有探讨两者之间的关系及其制订对区域发展政策和规划的影响。目前,对于亚洲特别是中国的大都市多中心和多层级管治的系统研究尚不多,本文尝试揭示大珠三角作为多中心都市区和跨境区域的多层级管治的形成、演变和影响。本文进一步透过跨境大桥的案例分析,尝试揭示这个跨境城市一区域的多中心和多层级管治格局在“一国两制”框架下的独特之处。     

集中供热系统热源循环流量对供热质量的影响

阐述了在设计工况和非设计工况下集中供热系统热源循环流量变化对热用户供热质量的影响规律。通过计算，确定出这种影响的幅度，为冬季供暖运行指标中“实际循环流量”的确定提供参考。     

FRP筋混凝土梁有限元分析与抗弯承载力计算

对FRP筋混凝土梁正截面抗弯承载力分析是FRP筋用于实际工程的前提。我国混凝土规范已经给出了普通钢筋混凝土结构承载力计算公式,由于FRP筋与普通钢筋在材料性质上有很大差异,普通钢筋混凝土结构承载力计算公式对于FRP筋混凝土结构不是完全适用的。本文在应用ABAQUS有限元软件分析和混凝土规范的基础上提出适用于FRP筋混凝土梁承载力计算的实用计算方法。     

Expert survey on capacity markets in the US: Lessons for the EU

We present a survey of US capacity market experts with the purpose of drawing lessons for the EU. Of the respondents, 41% advised EU member states against implementing capacity markets, while the remaining were neutral or provided suggestions for improving capacity markets. Cross-border effects are currently not a concern but may become so in the future. Imports may dampen prices in a capacity market, but neighbouring markets may also experience pressure to implement a capacity market. The capacity markets in the USA were believed to have achieved their goals with respect to reliability, but in an economically inefficient manner.     

Reactive power pricing in power markets: a comprehensive review

ABSTRACT

Reactive power is one of the main characteristics that play a major role in power systems. When reactive flow is inadequate, the power system is confronted with voltage collapse and more than enough reactive power production follows the circulation in the network and consequently the occupation of power lines. On the other hand, power market evolves from centralised and vertically integrated structure to a competitive environment. The reactive power market is different from energy market and like others such as spinning reserve, frequency control and power system stabiliser is taken in the category of the ancillary service market. This paper reviews various mechanisms for pricing of reactive power in both levels of transmission and distribution (T&D) system. Additionally, the cost paid for reactive power service in the presence of distributed energy resources is analysed because of their high penetration in the power system, especially in distribution level.     

Implementation of scarcity pricing without co-optimization in European energy-only balancing markets

The implementation of scarcity pricing is underway in the Belgian balancing market. The market design proposed in this paper aims at transposing the first principles of scarcity pricing theory to the boundary conditions of European balancing markets. One relevant boundary condition is the absence of real-time co-optimization of energy and reserves in Europe. As international experience demonstrates, the fact that energy and reserves are not co-optimized in balancing markets does not preclude the implementation of scarcity pricing. The mechanism can be implemented implicitly, and a concrete path has been proposed in the context of the Belgian balancing market. The Belgian design proposal, which is based on the implicit trading of reserve in real time, has raised questions related to financial implications for market stakeholders, the pricing of multiple reserve products, cross-border interactions, the financing of the mechanism, compatibility with EU law, and the coexistence of the proposed mechanism with capacity markets. We attempt to address these questions in the present work by drawing comparisons between the explicit co-optimization of energy and reserves and the implicit trading of reserve capacity.     

Evaluation of expected energy generation in multi-area interconnected systems with photo voltaic generating units

This paper presents a methodology which extends the segmentation method to evaluate the expected energy generation and the expected export/import among the electrical utilities in an interconnected system with renewable energy-based units as well as conventional thermal units. The proposed methodology is applied to the Power Grid of Bangladesh. The method helps the system planner determine the expected cost of energy generation of various sources. The randomness in the output of a renewable energy generator is appropriately modelled in the proposed methodology.     

Suggested empirical models for the axial capacity of circular CFT stub columns

In this paper, a total of 250 experimental tests of axially loaded circular concrete-filled steel tube (CFT) stub columns, published in the literature was summarized. The applicability of the current design codes such as ACI, Australian Standards, AISC, AIJ, Eurocode 4, DL/T and some available empirical models proposed by various researchers for calculating the axial capacity of circular CFT stub columns was examined using these experimental data. Based on the investigations, four new empirical models for predicting the axial capacity of circular CFT stub columns are proposed. The comparisons between the experimental results and the predictions of these models show that the proposed empirical models provide a direct, compact, and efficient representation of the ultimate strength of circular CFT stub columns made with not only normal strength but also high strength steel tubes and concrete. Finally, the limiting values of the maximum effective length, the compressive strength of concrete, the yield strength of steel tubes and the diameter-to-thickness for circular CFT stub columns with respect to the present empirical models are suggested. It is expected that engineers can easily use the present empirical models to estimate the axial capacities of circular CFT stub columns for engineering designs.     

冰蓄冷系统中主机制冷量的确定

通过对三种不同配置的冰蓄冷系统的逐时负荷和各节点载冷剂温度变化的详细分析,指出根据目前常用的公式计算出的主机制冷量在很多场合不能满足实际负荷要求。通过对这几种系统控制性能的初步比较得出主机上游且融冰优先的串联系统最有效,同时指出配有基载主机的蓄冰系统的负荷分配设计中需要注意的问题。     

Continuous and multidimensional assessment of resilience based on functionality analysis for interconnected systems

The increasing number of disruptions to critical infrastructure, like natural disasters, terrorist attacks or internal failure is today a major problem of society. Concern is even greater when considering the interconnected nature of critical infrastructure, which might lead to failure propagation, causing domino and cascade effects. To mitigate such outcomes, critical infrastructure must recover its capacity to function with regard to several criteria. Stakeholders must therefore analyse and improve the resilience of critical infrastructure before any disruption occurs, and base this analysis on different models so as to guarantee society’s vital needs. Current resilience assessment methods are mainly oriented toward the context of a single system, thus narrowing their criteria metrics, limiting flexibility and adaptation to other contexts and overlooking the interconnected nature of systems. This article introduces a new tool-equipped approach that makes it possible to define a model to evaluate the functionalities of interconnected systems. The model is then used to assess the resilience of these systems based on simple and generic criteria that can be extended and adapted. Several assertions related to the concept of resilience and some resilience indicators are also introduced. A case study provides the validation performed by experts from several domains.     

Adaptation of interconnected infrastructures to climate change: A socio-technical systems perspective

Climate change is likely to affect how society will function in this century. Because climate change effects may be severe, a next step is to study not only the effects on natural systems, but also the effects on built infrastructure systems and, in response to anticipated effects, the adaptation of those systems. Studies that discuss interconnected infrastructures, society's backbones, in light of climate change are emerging. We apply a socio-technical systems perspective in order to gain insight into the effects of climate change on our infrastructure systems and possible adaption strategies for the coming decades. We use this perspective to collect and describe the literature on adaptation of infrastructures to climate change. We find that the analysed papers predominantly focus on specific geographic areas and that various types of impacts on and interdependencies of built socio-technical systems are recognized, not only for energy and transport, but also for water infrastructures. A missing step is the modelling of adaptation measures. Recent literature enables an exploration of strategies for adaptation, which should be expected in the coming years.