Modeling and Control of Fuel Cells: Distributed Generation Applications (IEEE Press Series on Power and Energy Systems) - Hardcover

Nehrir, M. H.; Wang, C.

Hardcover

ISBN 10: 0470233281 ISBN 13: 9780470233283

Publisher: Wiley-IEEE Press, 2009

Synopsis

The only book available on fuel cell modeling and control with distributed power generation applications

The emerging fuel cell (FC) technology is growing rapidly in its applications from small-scale portable electronics to large-scale power generation. This book gives students, engineers, and scientists a solid understanding of the FC dynamic modeling and controller design to adapt FCs to particular applications in distributed power generation.

The book begins with a fascinating introduction to the subject, including a brief history of the U.S. electric utility formation and restructuring. Next, it provides coverage of power deregulation and distributed generation (DG), DG types, fuel cell DGs, and the hydrogen economy. Building on that foundation, it covers:

• Principle operations of fuel cells

• Dynamic modeling and simulation of PEM and solid-oxide fuel cells

• Principle operations and modeling of electrolyzers

• Power electronic interfacing circuits for fuel cell applications

• Control of grid-connected and stand-alone fuel cell power generation systems

• Hybrid fuel cell–based energy system case studies

• Present challenges and the future of fuel cells

MATLAB/SIMULINK-based models and their applications are available via a companion Web site. Modeling and Control of Fuel Cells is an excellent reference book for students and professionals in electrical, chemical, and mechanical engineering and scientists working in the FC area.

About this title

About the Author

M. HASHEM NEHRIR, PhD, is a Professor of Electrical and Computer Engineering at Montana State University-Bozeman. His primary areas of interest include modeling and control of power systems, alternative energy power generation systems, and applications of intelligent controls to power systems. In addition to this book, he is the author of two textbooks and the author or coauthor of numerous technical papers. He is a member of the IEEE PES Energy Development and Power Generation Committee and currently is Vice Chair of the IEEE PES Energy Development Subcommittee.

CAISHENG WANG, PhD, is Assistant Professor at Wayne State University in Detroit, Michigan. He has worked in the areas of both large power systems and distributed generation systems, including alternative energy sources. As a part of his doctoral research, during 2002–2006, Dr. Wang was involved in fuel cell modeling and control and design of hybrid alternative energy power generation sources, including fuel cells.

The emerging fuel cell (FC) technology is growing rapidly in its applications from small-scale portable electronics to large-scale power generation. This book gives students, engineers, and scientists a solid understanding of the FC dynamic modeling and controller design to adapt FCs to particular applications in distributed power generation.

The book begins with a fascinating introduction to the subject, including a brief history of the U.S. electric utility formation and restructuring. Next, it provides coverage of power deregulation and distributed generation (DG), DG types, fuel cell DGs, and the hydrogen economy. Building on that foundation, it covers:

• Principle operations of fuel cells

• Dynamic modeling and simulation of PEM and solid-oxide fuel cells

• Principle operations and modeling of electrolyzers

• Power electronic interfacing circuits for fuel cell applications

• Control of grid-connected and stand-alone fuel cell power generation systems

• Hybrid fuel cell–based energy system case studies

• Present challenges and the future of fuel cells

MATLAB/SIMULINK-based models and their applications are available via a companion Web site. Modeling and Control of Fuel Cells is an excellent reference book for students and professionals in electrical, chemical, and mechanical engineering and scientists working in the FC area.

The emerging fuel cell (FC) technology is growing rapidly in its applications from small-scale portable electronics to large-scale power generation. This book gives students, engineers, and scientists a solid understanding of the FC dynamic modeling and controller design to adapt FCs to particular applications in distributed power generation.

The book begins with a fascinating introduction to the subject, including a brief history of the U.S. electric utility formation and restructuring. Next, it provides coverage of power deregulation and distributed generation (DG), DG types, fuel cell DGs, and the hydrogen economy. Building on that foundation, it covers:

• Principle operations of fuel cells

• Dynamic modeling and simulation of PEM and solid-oxide fuel cells

• Principle operations and modeling of electrolyzers

• Power electronic interfacing circuits for fuel cell applications

• Control of grid-connected and stand-alone fuel cell power generation systems

• Hybrid fuel cell–based energy system case studies

• Present challenges and the future of fuel cells

MATLAB/SIMULINK-based models and their applications are available via a companion Web site. Modeling and Control of Fuel Cells is an excellent reference book for students and professionals in electrical, chemical, and mechanical engineering and scientists working in the FC area.

Excerpt. © Reprinted by permission. All rights reserved.

Modeling and Control of Fuel Cells

Distributed Generation ApplicationsBy M. Hashem Nehrir Caisheng Wang

John Wiley & Sons

Copyright © 2009 The Institute of Electrical and Electronics Engineers, Inc.
All right reserved.
ISBN: 978-0-470-23328-3

Chapter One

INTRODUCTION

Global environmental concerns and the ever-increasing need for electrical power generation, steady progress in power deregulation, and tight constraints over the construction of new transmission lines for long distance power transmission have created increased interest in distributed generation (DG). Of particular interest are renewable DGs with free energy resources, such as wind and solar photovoltaic (PV), and alternative energy DG sources with low emission of pollutant gases, such as fuel cell (FC) and microturbine (MT) power generation devices.

In this chapter, some background about the restructured utility that lead to increased interest in DG is given first. Then, an overview of distributed generation and its different types is addressed. Distributed generation applications of fuel cells will be covered next. Finally, since all viable types of fuel cells use hydrogen ([H.sub.2]) as fuel, the last part of this chapter covers the hydrogen economy, a need for a fuel-cell-powered society.

1.1 BACKGROUND: A BRIEF HISTORY OF U.S. ELECTRIC UTILITY FORMATION AND RESTRUCTURING

Electric utilities were initially formed in the United States in late nineteenth century and established as isolated electric systems without connection to one another. In 1920s, the isolated electric systems were interconnected to help each other in load sharing and backup power. In 1934, the U.S. Congress passed the Public Utility Holding Company Act (PUHCA), where it increased the jurisdiction of the Securities Exchange Commission as well as the jurisdiction of the Federal Power Commission. This act created incentives for the isolated utilities to expand and create regional utilities, where several state utilities joined under a regional utility company. Each entity operated in its region under an investor-owned monopoly, owning generation, transmission, and distribution. However, each utility was subject to state regulation, where the utilities' rates had to be approved by the Public Utilities Commissions.

In 1977, the U.S. Department of Energy (DOE) was created to oversee the nation's energy-related activities, and under it, the Federal Energy Regulatory Commission (FERC) was formed to establish rules for generation, transport, and quality of power, among others.

The U.S. Congress passed the Public Utilities Policy Act (PURPA) in 1978. This act encouraged the construction and integration of nonutility-owned power generation technologies, including conventional and nonconventional (renewable/alternative) energy sources, to the utility grid. Under the above act, FERC sets rules for the interconnection of these power generation sources to the utility grid. Until near the end of the twentieth century, the utilities were still operating under the vertical (monopoly) structure; each utility owned generation, transmission, and distribution in a given region.

The major Energy Policy Act, enacted by the Congress in 1992, drove the U.S. power industry into complete restructuring; now, more than 15 years later, it is still ongoing. As a result of this act, "Exempt Wholesale Generator (EWG)" entities were created with the restriction that EWGs can only sell the power they generate on the wholesale market and not on the retail market. On the contrary, electric utilities are not required to purchase power from EWGs, but they are required to purchase power from qualified power generating facilities that include renewable/alternative energy power generation facilities. This energy policy act created a major shift in regulatory power from the regional level to the federal level with FERC continuing to be its rule making body. According to the policy act, the power generating entities had transmission access for the power they generated. In 1996, FERC issued the "Mega Rule," which spelled out how open access transmission of power is to be handled. It requires the transmission system owners to treat all transmission users on a nondiscriminatory basis and file tariffs for their transmission services.

Gradually, the vertical electric utility, where one company owned generation, transmission and distribution facilities, changed to a horizontal structure. In this new paradigm, generation, transmission and distribution companies became separate and independent, namely GENCO, TRANSCO, and DISCO. Generation being the only one of the three entities that is truly deregulated, numerous independent power producers (IPPs) were formed and found an opportunity to market their power. This change also created the opportunity for large and small power marketers to be formed to begin marketing the power produced by IPPs (GENCOs). Since the start of power deregulation in 1996, FERC has promoted the formation of regional transmission organizations (RTOs).

In 1999, FERC Order 2000 required the transmission system owners to put their transmission system under the control of RTOs. Today, several regions have established independent system operators (ISOs), or are in the planning stage to establish ISOs, to operate their transmission systems and provide transmission services. In 2005, the U.S. government passed the Energy Policy Act of 2005. This act authorizes the creation of an electric reliability organization (ERO), giving it the authority to enforce compliance of all market participants with the reliability standards of the National Electric Reliability Council (NERC), which was voluntary prior to 2005. In 2006, FERC certified NERC to be the U.S. ERO. Given the close interconnection of the U.S. and Canadian electric system, NERC is also seeking recognition as the ERO from the Canadian government.

Figure 1.1a shows the structure of the vertical utility of the past, where generation, transmission, and distribution systems in one region were owned by the utility in that region and sale of power within the region took place by that utility. Figure 1.1b shows the restructured horizontal utility, where different GENCOs market their power and TRANSCOs and DISCOs arrange the transport of power to customers. Figure 1.2 shows the role of ISO in the restructured utility and the deregulated power market. ISOs oversee the transport of power from generation to transmission to distribution including the marketing (buy/sell) of electric power. The structure and different entities of ISO in a region depends on the market structure in that region. At the time of writing this book, power deregulation and utility restructuring are being actively pursued worldwide.

1.2 POWER DEREGULATION AND DISTRIBUTED GENERATION

As explained in the previous section, numerous IPPs were formed as a result of power deregulation, which also spurred the consideration of DG sources. The main reason behind this consideration was, and still is, economics and the driving market forces. The fast growth in demand for electricity along with the slow growth in generation capacity in the last quarter of the twentieth century resulted in shrinking spinning reserve margins, which as a result, made power systems vulnerable and brought about the need for additional power generation. The economic constraints behind building large central power generating stations and expanding the transmission infrastructure encouraged the consideration of DGs. DGs are modular in structure and less costly to build, normally placed at the distribution level at or near load centers, and are small in size (relative to the power capacity of the system in which they are placed). When possible, DGs can be strategically (optimally) placed in distribution systems for grid reinforcement, reducing power losses, on-peak operating costs, and improving voltage profiles and load factors. As a result, their installation can defer or eliminate the need for system upgrades, and can improve system integrity, reliability and efficiency. Because of these benefits, DG became, and still is, a priority.

DGs also have barriers and obstacles, which must be overcome before they can become a mainstream service. These barriers include technical, economic, and regulatory issues. Some of the proposed technologies have not yet entered the market; they need to meet some pricing and performance targets before entry. In addition to this, the most important issues facing DGs are safety issues, operation issues, power quality issues, and accountability issues. These issues are briefly discussed below:

Safety issues are very important. Grid-connected DGs can keep the power lines live after a grid power outage (thus making it unsafe for maintenance crews to work on the power lines) if appropriate measures are not taken to disconnect the DGs from the grid shortly after the outage. The IEEE Power Engineering Society has taken a leading role in developing standards (e.g., IEEE Standard 1547 [26]) for detection of power islands, that is, when the grid power goes out and DGs are still connected to the grid. According to the above standard, the islanded DGs must be disconnected from the grid within two seconds. Research is under way to develop reliable islanding detection and autonomous operation of DGs so that they can operate as isolated DGs to provide power to some critical loads, which they may be feeding. In spite of the technical and socio-economic issues, DGs, conventional and modern, are expected to become wide-spread around the globe.

Operation and reliability issues of DGs could have positive or negative impacts on the distribution systems to which they are connected. DGs are normally connected to the utility grid at the distribution level and can bring voltage support to the grid by providing reactive power support. This condition could be helpful for reliable operation of distribution systems provided that the distribution system is properly configured for inclusion of DGs. On the contrary, DGs could have negative impact on distribution systems operation. For example, DGs with variable output power (i.e., wind and solar) may not be able to provide the required power at the right time, or, DGs that use induction generators (e.g., wind), receive reactive power from the grid and could actually worsen reactive coordination and operational reliability.

Power quality issues are becoming more pronounced as the more modern DG technologies (e.g., wind, photovoltaic, fuel cells) utilize power electronic devices (i.e., dc/dc and dc/ac converters) to interface with the utility grid. These devices inject nonsinusoidal (or at least imperfect sinusoidal) current to the grid. If the harmonics generated by these devices are not properly filtered, they can cause operational problems and possible malfunction of loads connected to distribution system to which the DGs are connected. IEEE standards 519-1992 and 1547-2003 recommend that the total current harmonic distortion injected by a DG source should be less than 5%.

Accountability issues related to DGs can be very complex. The end-users may not know or care about the nature of the restructured power industry. However, they want reliable power. In a distribution system enhanced with one or more DGs, if the DGs trip out or are not able to provide the desired amount of power to the grid, the quality of power provided to the end-users may diminish. Who is accountable to the customers for such problems, the DG owners or the end-use service provider? This is a serious problem facing the restructured power industry, which will increase in magnitude as DGs penetrate the power grid. Therefore, carefully written policies, regulations, and buy-sell agreements are needed to address such problems-thus making the role of FERC in the deregulated power market more important than ever.

1.3 DG TYPES

In this book distributed generation is referred to small generators, starting from a few kWs up to 10 MW, whether connected to the utility grid or used as stand-alone at an isolated site. Normally small DGs, in the 5-250 kW range serve households to large buildings (either in isolated or grid-connected configuration). In grid-connected configuration, DGs with larger capacities are managed by a utility or an IPP. They are located at strategic points, normally at the distribution level, near load centers, and used for such purposes as capacity support, voltage support and regulation, and line loss reduction. DG technologies can be categorized to renewable and nonrenewable DGs.

Renewable energy technologies are in general sustainable (i.e., their energy source will not run out) and cause little or no environmental damage; they include the following:

Solar photovoltaic

Solar thermal

Wind

Geothermal

Tidal

Low-head (small) hydro

Biomass and biogas

Hydrogen fuel cells (hydrogen generated from renewable resources).

Nonrenewable energy technologies are referred to those that use some type of fossil fuel such as gasoline, diesel, oil, propane, methane, natural gas, or coal as their energy source. Fossil fuel-based DGs are not considered sustainable power generation sources as their energy source will not renew. They include the following:

Internal combustion engine (ICE)

Combustion turbine

Gas turbine

Microturbine

Fuel cells (using some type of fossil fuel, e.g., natural gas, to generate hydrogen).

Both types of DGs (renewable and nonrenewable) discussed above are popular and widely used around the world. The downside of renewable resource DGs is the intermittent nature of their renewable energy source; and the disadvantage of fossil fuel-based DGs is that they generate environmentally polluting, and in some cases poisonous exhaust gases, such as S[O.sub.2] and N[O.sub.x], which are similar to the pollutants from conventional centralized power plants. However, considering the increasing need for electricity, the benefits of the nonrenewable DG technologies with low emission of polluting gasses exceed their disadvantages and are expected to be used in the foreseeable future.

Fuel cell technology can belong to either of the above categories. If the hydrogen fuel needed to power the fuel cell is generated from a renewable source, the fuel cell power-generating unit is considered a renewable energy technology. An example of this case (i.e., wind and solar energy used to generate hydrogen to fuel a fuel cell stack) will be covered in Chapter 9. On the contrary, if hydrogen is produced from a fossil fuel source (e.g., natural gas or methane), the fuel cell is considered a nonrenewable energy technology.

Through careful design, selected fossil fuel driven DGs can be built to oxidize some of the fossil fuel (by combining with oxygen) to produce heat. Such operation modes, whether in electromechanical (rotational) or electrochemical (fuel cell) systems, are referred to as combined heat and power (CHP) operation mode.

Table 1.1 shows some existing and potential DG technologies, nonrenewable and renewable, and their capacity and efficiency ranges.

Most of the new DG technologies include power electronic devices to provide usable output power. These DGs are often referred to as power electronically interfaced DGs. Enormously improved power control of these generation sources has become possible by controlling their power electronic interfacing units. In a common approach the output voltage of these generation devices, whether dc or ac, is converted to a controlled dc voltage and then converted to usable ac, which can be connected to a utility grid or used stand-alone.

Distributed generation devices can pose both positive and negative impacts on existing power systems. These new issues, such as islanding detection and operation (discussed earlier) and optimal size and placement of DGs in power systems, have made DG operation an important research area, which can help obtain maximum potential benefits from DGs.

Since this book's focus is on Fuel cell DGs (FCDGs), this topic will be covered in the next section.

1.4 FUEL CELL DG

Fuel cells are static energy conversion devices that convert the chemical energy of fuel directly into dc electrical energy. Fuel cells have a wide variety of potential applications including micropower, auxiliary power, transportation, stationary power for buildings, and cogeneration applications.

Since entering the twenty-first century, fuel cell technologies have experienced exponential growth; the number of installed FC units worldwide is increasing rapidly. As shown in Fig. 1.3, Government policies, public opinion, and technology advances in fuel cells all contributed to this phenomenal growth. It is expected that FC (and FCDG) technology will advance in the first half of the twenty-first century as the computer technology did in the second half of the twentieth century. However, a number of barriers must be overcome before FCDG can be a reliable energy source. The main barriers are technical and economic issues.

(Continues...)

Excerpted from Modeling and Control of Fuel Cellsby M. Hashem Nehrir Caisheng Wang Copyright © 2009 by The Institute of Electrical and Electronics Engineers, Inc.. Excerpted by permission.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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Edition details

• Publisher: Wiley-IEEE Press
• Publication date: 2009
• Language: English
• ISBN 10: 0470233281
• ISBN 13: 9780470233283
• Binding: Hardcover
• Edition number: 1
• Number of pages: 312