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About this book

Energy has been an inevitable component of human lives for decades. Recent rapid developments in the area require analyzing energy systems not as independent components but rather as connected interdependent networks. The Handbook of Networks in Power Systems includes the state-of-the-art developments that occurred in the power systems networks, in particular gas, electricity, liquid fuels, freight networks, as well as their interactions. The book is separated into two volumes with three sections, where one scientific paper or more are included to cover most important areas of networks in power systems. The first volume covers topics arising in electricity network, in particular electricity markets, smart grid, network expansion, as well as risk management. The second volume presents problems arising in gas networks; such as scheduling and planning of natural gas systems, pricing, as well as optimal location of gas supply units. In addition, the second volume covers the topics of interactions between energy networks. Each subject is identified following the activity on the domain and the recognition of each subject as an area of research. The scientific papers are authored by world specialists on the domain and present either state-of-the-arts reviews or scientific developments.

Table of Contents

Frontmatter

Gas Network

Frontmatter

Implementation of a Scheduling and Pricing Model for Natural Gas

Abstract
Since 1999, the Australian state of Victoria has operated a natural gas spot market to both determine daily prices for natural gas and develop an optimal schedule for the market based on an LP (Linear Programming) approximation to the underlying inter-temporal nonlinear aspects of the gas flow optimization problem. This market employs a dispatch optimization model and a related market clearing model. Here we present the model employed for both the operational scheduling and price determination. The basic dispatch optimization formulation covers the key physical relationships between pressure, flow, storage, with flow controlled by valves, and assisted by compressors, where flow and storage are measured with respect to energy rather than in terms of mass. But we also discuss a range of sophisticated mathematical techniques which have had to be employed to create a practical dispatch tool, including iterating between piecewise and successive linearization; iterating between barrier and simplex algorithms to manage numerical accuracy and solution speed issues, and special methods developed to deal with scheduling flexibility. The market clearing model is a variation on the dispatch optimization model which replaces the gas network with an infinite storage tank with unlimited transport capacity. We address the performance of the model including accuracy and run time.
W. Pepper, B. J. Ring, E. G. Read, S. R. Starkey

Long-Term Pressure-Stage Comprehensive Planning of Natural Gas Networks

Abstract
Due to the forthcoming regulation schemes throughout Europe, new challenges for natural gas network operators arise. The pressure for realizing and operating cost-efficient network structures increases as the regulation is based on a comparison of different network operators with the network operator setting the minimal allowable costs. Optimization methods, which will also be applied by regulatory authorities as part of the analytical cost models for calculating the efficiency of natural gas networks, provide the opportunity to identify long-term cost-efficient network structures, so called reference networks. Boundary conditions of natural gas networks, which concern the system’s technical safety and thus need to be regarded during network planning, are given by the rules set by each country’s technical assembly for natural gas supply. Degrees of freedom exist in alternative network structures, the number and degree of pressure stages and for the dimensioning of equipment. Therefore, optimization methods are required for solving the extensive optimization problem. Especially heuristic optimization algorithms have proved to deliver an optimal performance for the determination of cost-efficient network structures. Their essential advantages over exact methods are a reduced computational effort, leading to computing times of typically few hours for real natural gas systems while simultaneous delivering several similar cost-efficient network structures. These advantages allow sensitivity analysis by a variation of boundary conditions and supply tasks on network structure and network costs and lead to a greater flexibility for the future network development. Therefore, an optimization method for natural gas distribution networks based on Genetic Algorithms is proposed. The method is capable of calculating cost-efficient network structures with regard to all technical and economic boundary conditions and is also used by the German Federal Network Agency for calculating reference networks with minimum costs for given supply tasks. Exemplary applications demonstrate the method’s capability and the advantages through applying this method for long-term planning of natural gas networks.
Michael Hübner, Hans-Jürgen Haubrich

Optimal Location of Gas Supply Units in Natural Gas System Network

Abstract
Natural gas industry has been confronted with big challenges: great growth in demand, investments on new GSUs – gas supply units, and efficient technical system management. The right number of GSUs, their best location on networks and the optimal allocation to loads is a decision problem that can be formulated as a combinatorial programming problem, with the objective of minimizing system expenses. Our emphasis is on the formulation, interpretation and development of a solution algorithm that will analyze the trade-off between infrastructure investment expenditure and operating system costs. The location model was applied to a 12 node natural gas network, and its effectiveness was tested in five different operating scenarios.
Teresa Nogueira, Zita Vale

An LP Based Market Design for Natural Gas

Abstract
Many electricity markets are now cleared using Linear Programming (LP) formulations that simultaneously determine an optimal dispatch and corresponding nodal prices, for each market dispatch interval. Although natural gas markets have traditionally operated in a very different fashion, the same basic concept can be applied. Since 1999, the Australian state of Victoria has operated a gas market based on an LP approximation to the underlying gas flow optimization problem. Here we discuss market design issues, using a formulation derived from the key gas flow equations. Dual variables on key constraints imply prices which vary by location, as for electricity markets, but also by time. But gas is both delayed and stored within the transportation system itself. This raises a number of operational, pricing, and hedging issues which could be ignored in the case of electricity, but become important when operating this kind of market for gas, or other commodities, such as water, in a supply network where there are delays and storage.
E. G. Read, B. J. Ring, S. R. Starkey, W. Pepper

Network Interactions

Frontmatter

Energy Carrier Networks: Interactions and Integrated Operational Planning

Abstract
The integration of natural gas (NG) and electricity sectors has rapidly increased as a consequence of the growing installation of natural gas fired power plants (NGFPP). This has driven the need to model the interactions among the energy carriers and to optimize energy resources management from a centralized planning perspective. Currently, electricity and NG systems are considered in a decoupled manner. NG prices and availabilities for the electric power generation are used as fixed parameters for the needed coordination between both energy sectors. This chapter presents a comprehensive literature survey of previous research on integrated electricity and NG operational planning. The relevant characteristics of NG and electricity systems are compared considering the physical laws that govern the flows of these energy carriers through dedicated networks. The interactions among the energy carriers and their networks are modeled with different levels of detail according to the evaluated time horizon. The integrated operational planning problem of multiple energy carriers systems is comprehensively described and formulated, covering from the long/medium-term energy resource scheduling to the single period economic dispatch. Finally, a contribution is made about the economic interactions between different energy carriers (electricity, NG, and hydro energy) through opportunity costs such as water and NG values.
Ricardo Rubio-Barros, Diego Ojeda-Esteybar, Alberto Vargas

Costs and Constraints of Transporting and Storing Primary Energy for Electricity Generation

Implications for Optimization Models
Abstract
This article describes the fuel transportation and storage components of the supply chain for electricity. We focus on dispatchable generation based on transportable fuels. Coal has very flexible transportation and storage requirements. Natural gas requires pressurized pipelines and storage facilities; or it can be liquefied, then stored and transported at very low temperatures, and then revaporized. Biomass presents logistical challenges related to its relatively low energy intensity and seasonality of supply. We review ways to model the physical constraints and cost characteristics that govern the transportation and storage of these fuels and examine their implications for decision models in restructured electricity markets.
Sarah M. Ryan, Yan Wang

Integrated Optimization of Grid-Bound Energy Supply Systems

Abstract
Energy supply is facing the challenge to be secure, competitive and sustainable, in spite of a shortage of fossil energy sources, while worldwide demand is growing, prices for oil and gas are increasing and important regions in the word are politically instable. The European Board as well as the Federal Republic of Germany have passed laws and set regulations to intensify competition, to reduce dependency of imports of recourses, to increase energy-efficiency and to support new technological solutions. Therefore, an optimization of existing energy supply systems is necessary, taking into account alternative energy supply concepts. The concepts, which are investigated in this article, consist of grids, distributed generation units and heating systems. Combinations of these components define different energy supply concepts. All energy supply concepts have an electricity supply via the electrical grid in common. Three energy carriers, and their associated networks, are commonly used to supply heat demand: electricity, natural gas and district heating. Since the complexity of the planning process increases with the number of new technologies and possible energy supply concepts, handling complex planning tasks is challenging. Due to the aforementioned high pressure to reduce costs and to increase energy-efficiency, a solution should be found that is as cost and energy efficient as possible. Computer-based optimization methods provide the opportunity to identify long-term cost- and energy-efficient energy supply systems. Especially heuristic optimization algorithms have shown a good performance in related network optimization problems. Their essential advantages are a reduced computational effort leading to computing times allowing investigation of large-scale supply tasks while simultaneously delivering several, similarly cost-efficient energy supply systems. Therefore, an optimization method for grid-bound energy supply systems based on Genetic Algorithms is proposed. For a given supply task the method is capable of calculating cost-efficient energy supply systems with regard to all technical and environmental constrains in an integrated planning process. Exemplary applications demonstrate the method’s capability and the advantages of applying this method for long-term planning of energy supply systems. Comparing optimized energy supply systems with existing systems allows direct conclusions for necessary adjustments and possible gains of efficiency.
Simon Prousch, Hans-Jürgen Haubrich, Albert Moser

Backmatter

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