Hybrid Systems Based on Solid Oxide Fuel Cells

Modelling and Design
 
 
Wiley (Verlag)
  • erschienen am 12. Juni 2017
  • |
  • 344 Seiten
 
E-Book | ePUB mit Adobe-DRM | Systemvoraussetzungen
978-1-119-03907-5 (ISBN)
 
A comprehensive guide to the modelling and design of solid oxide fuel cell hybrid power plants
This book explores all technical aspects of solid oxide fuel cell (SOFC) hybrid systems and proposes solutions to a range of technical problems that can arise from component integration. Following a general introduction to the state-of-the-art in SOFC hybrid systems, the authors focus on fuel cell technology, including the components required to operate with standard fuels. Micro-gas turbine (mGT) technology for hybrid systems is discussed, with special attention given to issues related to the coupling of SOFCs with mGTs. Throughout the book emphasis is placed on dynamic issues, including control systems used to avoid risk conditions.
With an eye to mitigating the high costs and risks incurred with the building and use of prototype hybrid systems, the authors demonstrate a proven, economically feasible approach to obtaining important experimental results using simplified plants that simulate both generic and detailed system-level behaviour using emulators. Computational models and experimental plants are developed to support the analysis of SOFC hybrid systems, including models appropriate for design, development and performance analysis at both component and system levels.
* Presents models for a range of size units, technology variations, unit coupling dynamics and start-up and shutdown behaviours
* Focuses on SOFCs integration with mGTs in light of key constraints and risk avoidance issues under steady-state conditions and during transient operations
* Identifies interaction and coupling problems within the GT/SOFC environment, including exergy analysis and optimization
* Demonstrates an economical approach to obtaining important experimental results while avoiding high-cost components and risk conditions
* Presents analytical/computational and experimental tools for the efficient design and development of hardware and software systems
Hybrid Systems Based on Solid Oxide Fuel Cells: Modelling and Design is a valuable resource for researchers and practicing engineers involved in fuel cell fundamentals, design and development. It is also an excellent reference for academic researchers and advanced-level students exploring fuel cell technology.
weitere Ausgaben werden ermittelt
MARIO L. FERRARI is Associate Professor in the Dipartimento di Ingeneria Meccanica, Energetica,Gestionale ed dei Trasporti (DIME) of the University of Genova, Italy.
USMAN M. DAMO is at the School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, UK, as a Research Associate.
ALI TURAN is a Professor and chair holder in the thermodynamics of power generation and propulsionat the University of Manchester, UK.
DAVID SÁNCHEZ is currently a Professor in Energy Systems and Turbomachinery in the Department of Energy Engineering at the University of Seville, Spain.
  • Cover
  • Title Page
  • Copyright
  • Contents
  • Preface
  • Acknowledgements
  • Chapter 1 Introduction
  • 1.1 World Population Growth, Energy Demand and its Future
  • 1.2 World Energy Future
  • 1.3 Introduction to Fuel Cells and Associated Terms
  • 1.3.1 Background for Fuel Cells and Thermodynamic Principles
  • 1.3.2 Solid Oxide Fuel Cells (SOFCs)
  • 1.3.2.1 Electrolyte
  • 1.3.2.2 Anode
  • 1.3.2.3 Cathode
  • 1.3.2.4 Interconnector
  • 1.3.3 Fuel Cell Reactions
  • 1.3.4 Fuel Cell Performance
  • 1.3.5 Pressure and Concentration Effects
  • 1.3.6 Irreversibilities in Fuel Cells
  • 1.3.7 Fuel Cell Applications
  • 1.3.7.1 Transportation Applications
  • 1.3.7.2 Portable Electronic Equipment
  • 1.4 Gas Turbines
  • 1.4.1 Background of Gas Turbines
  • 1.5 Coupling of Microturbines with Fuel Cells to Obtain 'Hybrid Systems'
  • 1.5.1 Active Hybrid Systems Research Groups
  • 1.6 Conclusions
  • References
  • Chapter 2 SOFC Technology
  • 2.1 Basic Aspects of Solid Oxide Fuel Cells
  • 2.2 SOFC Types
  • 2.2.1 High-temperature SOFCs
  • 2.2.2 Intermediate/Low-temperature SOFCs
  • 2.3 Materials for SOFCs
  • 2.4 Different SOFC Geometries
  • 2.4.1 Tubular SOFCs
  • 2.4.1.1 Electrical Conduction Around the Tube
  • 2.4.1.2 Electrical Conduction Along the Tube
  • 2.4.1.3 Segmented-in-series Tubular SOFCs
  • 2.4.2 Planar SOFCs
  • 2.5 SOFC Stacks
  • 2.6 Effect of Pressurization for SOFCs
  • 2.7 Fuel Processing for SOFCs
  • 2.7.1 Processing for Gas and Liquid Fuels
  • 2.7.1.1 Steam Reforming
  • 2.7.1.2 Partial Oxidation
  • 2.7.1.3 Autothermal Reforming
  • 2.7.2 Processing for Solid Fuels
  • 2.7.2.1 Syngas Treatment
  • 2.8 SOFC Applications in Hybrid Systems
  • 2.8.1 Atmospheric SOFC Hybrid Systems
  • 2.8.2 Pressurized SOFC Hybrid Systems
  • 2.9 Aspects Related to SOFC Reliability, Degradation and Costs
  • 2.10 Conclusions
  • 2.11 Questions
  • References
  • Chapter 3 Micro Gas Turbine Technology
  • 3.1 Fundamentals of the Brayton Cycle
  • 3.1.1 The Simple Cycle
  • 3.1.2 The Simple Recuperative Cycle
  • 3.1.3 The Intercooled and Reheat Brayton Cycles
  • 3.1.4 The Intercooled and Reheat, Recuperative Brayton Cycle
  • 3.1.5 Cycle Layouts used by Contemporary Micro Gas Turbines
  • 3.2 Turbomachinery
  • 3.2.1 General Considerations on the Selection of Turbomachinery for Micro Gas Turbines
  • 3.2.2 Fundamentals of Radial Compressor Design and Performance
  • 3.2.3 Some Notes on Compressor Surge
  • 3.2.4 Fundamentals of Radial Turbine Design and Performance
  • 3.2.5 Scaling of Radial Turbomachinery
  • 3.3 Recuperative Heat Exchanger
  • 3.4 Bearings
  • 3.5 Conclusions: Commercial Status and Areas of Research
  • 3.6 Questions and Exercises
  • References
  • Chapter 4 SOFC/mGT Coupling
  • 4.1 Basic Aspects of SOFC Hybridization
  • 4.2 SOFC Coupling with Traditional Power Plants
  • 4.2.1 Coupling with Steam Power Plants
  • 4.2.2 Coupling with Gas Turbines
  • 4.2.3 Coupling with Combined Cycle-based Plants
  • 4.3 Beneficial Attributes Related to SOFC/mGT Coupling
  • 4.4 Constraints Related to SOFC/mGT Coupling
  • 4.4.1 Turbine System Constraints
  • 4.4.2 SOFC System Constraints
  • 4.4.3 Control System Constraints
  • 4.5 Design and Off-design Aspects
  • 4.5.1 Design Aspects
  • 4.5.2 Off-design Aspects
  • 4.6 Issues Related to Dynamic Aspects
  • 4.7 Main Prototypes Developed for SOFC Hybrid Systems
  • 4.7.1 Prototype by Siemens-Westinghouse
  • 4.7.2 Prototype by Mitsubishi Heavy Industries
  • 4.7.3 Prototype by Rolls-Royce Fuel Cell Systems
  • 4.8 Conclusions
  • 4.9 Questions and Exercises
  • References
  • Chapter 5 Computational Models for Hybrid Systems
  • 5.1 Introduction
  • 5.2 Steady-state Models for Hybrid Systems
  • 5.3 Computational Models for Hybrid Systems: Modelling Steps
  • 5.3.1 Computational Models for Hybrid Systems at the Component Level
  • 5.3.2 Prediction of Performance of Gas Turbines
  • 5.3.3 Off-design Operation of the Single-shaft Gas Turbine
  • 5.3.4 Off-design Calculation with 'Complex' Layout Turbines
  • 5.3.4.1 Equilibrium Running of a Gas Generator
  • 5.3.4.2 Off-design Operation of a Free Turbine Engine
  • 5.4 System Modelling
  • 5.4.1 Reformer
  • 5.4.2 SOFC Module
  • 5.4.3 Overpotentials
  • 5.4.4 Fuel and Air Supply Calculations
  • 5.4.5 Combustor
  • 5.4.6 Turbine
  • 5.4.7 Compressor
  • 5.4.8 Recuperator
  • 5.5 Results and Discussion
  • 5.6 Dynamic Models
  • 5.7 Model Validation
  • 5.8 Conclusion
  • 5.9 Questions and Exercises
  • References
  • Chapter 6 Experimental Emulation Facilities
  • 6.1 Experimental Emulation Facilities
  • 6.2 Reduced-scale Test Facilities
  • 6.2.1 Anodic Recirculation Test Rig
  • 6.2.2 Cathodic Loop Test Rig
  • 6.3 Actual-scale Test Facilities
  • 6.3.1 Low-temperature Rigs
  • 6.3.1.1 Surge Test Rig
  • 6.3.1.2 Emulation Rig for Tests on Control Components
  • 6.3.2 High-temperature Rigs
  • 6.3.2.1 Emulator by the US Department of Energy - NETL
  • 6.3.2.2 Emulator by the University of Genoa - TPG
  • 6.3.2.3 Emulator by the DLR
  • 6.4 Conclusions
  • 6.5 Questions and Exercises
  • References
  • Chapter 7 Problems and Solutions for Future Hybrid Systems
  • 7.1 The Future of Micro Power Generation Systems
  • 7.2 The Future of Hybrid Systems: Hydrogen as an Energy Carrier
  • 7.2.1 Hydro-methane and Hydrogen-rich Fuel Mixtures
  • 7.3 Future Hybrid Systems: Design, Optimization and Sizing
  • 7.3.1 Hybrid Systems Sizing Techniques
  • 7.3.2 Hybrid System Sizing Simulation Tools
  • 7.4 Cost Analysis of Hybrid Systems for Power Generation Applications
  • 7.5 Performance Degradation Problems in Solid Oxide Fuel Cells
  • 7.6 Turbomachinery Problems
  • 7.7 Dynamic and Control System Aspects
  • 7.8 CO2 Separation Technologies for SOFC Hybrid Plants
  • 7.9 Coal and Biofuel for Hybrid Systems
  • 7.10 Conclusions
  • References
  • Glossary
  • Index
  • EULA

Chapter 1
Introduction


Chapter Overview


  1. World Population Growth, Energy Demand and its Future
  2. World Energy Future
  3. Introduction to Fuel Cells and Associated Terms
  4. Gas Turbines
  5. Coupling of Microturbines with Fuel Cells to Obtain 'Hybrid Systems'
  6. Conclusions

The current and future energy scenarios faced by the international community are discussed in this chapter, starting with a brief presentation of the energy landscape and related issues, including the increase in demand and environmental aspects. A list of possible solutions to existing and foreseen problems is presented and discussed, setting the framework to highlight the significant potential of fuel cells for future power generation. Following on from this, the performance characteristics of fuel cells are introduced, including an analysis of their different types and corresponding differential features. Additionally, attention is devoted to hybrid systems based on the coupling of high-temperature fuel cells and microturbines (mGTs).

1.1 World Population Growth, Energy Demand and its Future


A study carried out by the United States Census Bureau (USCB) [1] estimated that the world population exceeded 7 billion on 12 March 2012. Now, at the time of writing in August 2016 with the global population standing at about 7.4 billion [2], this figure is expected to continue rising over the coming decades [2]. As the world population grows, in many countries faster than the global average of 2%, the need for more and more energy is intensifying in a somewhat similar proportion, thus putting pressure on the natural resources available and existing infrastructures. This higher energy consumption is not only due to the growth in world population, but also to the improved lifestyles leading to a greater energy demand per capita (two features that inevitably come together). This is best exemplified by the fact that the wealthy industrialized economies comprise 25% of the world's population but consume 75% of the world's energy supply [3]. A recent study (from ref. [4]) shows that the total world consumption of marketed energy is expected to increase from 549 quadrillion British thermal units (Btu) in 2012 to 629 quadrillion Btu in 2020, and to 815 quadrillion Btu in 2040 - a 48% increase from 2012 to 2040 [4].

Indeed, the landscape of future energy demand and generation projected for the world seems rather bleak, as most nations, including the most developed ones, depend primarily on conventional energy sources such as oil, coal and gas to generate power not only for the domestic and industrial sectors but also for transportation. This dependency results in global warming, contributes to rises in fuel prices that constitute a burden on economies, and can lead to delays in energy production and supply [5, 6]. Furthermore, even if the global production of fossil fuels is currently sufficient to cover the world's needs, the exponential rise in the exploitation rate of this finite, fast-depleting resource would pose a risk to the future energy demand and generation balance [7-9]. In the long run this global dependence on conventional fuel sources for power production will prove problematic because the world will eventually fall short or run out of these resources. Renewable energy sources are often set forth as a feasible alternative to this fossil-fuel dominated world [10], although many of their inherent features, such as their low energy density, intermittency and geographical distribution, pose a number of challenges that remain to be solved today.

1.2 World Energy Future


Due to the heavy reliance of most nations worldwide on fossil fuels for power generation and transportation, the atmospheric concentrations of carbon dioxide and methane have increased by 36% and 148% respectively, compared with pre-industrial levels [11]. These levels are indeed much higher than at any time during the last 800,000 years, the period for which reliable data have been extracted from ice cores. This observation is further confirmed by less direct geological observations that also show that carbon dioxide concentrations higher than today were last seen about 20 million years ago. These findings suggest that the root cause for such high concentrations is anthropogenic, mainly hydrocarbon-based fuel burning (responsible for three-quarters of the increase in CO2 from human activity over the past 20 years) and deforestation [11]. Other environmental factors, including air pollution, acid precipitation, ozone depletion and emission of radioactive substances, are also of concern and raise awareness of the negative impact of human activity on the environment [3].

As a consequence of this massive production of anthropogenic carbon dioxide and other greenhouse gases (trace gases in particular [12]), global temperatures in 2016 were 0.87°C above the long-term 1880-2000 average (the 1880-2000 annually averaged combined land and ocean temperature is 13.9°C), which translates into a warming rate of around 0.61°C/century over the last few decades. In particular, the average temperature of the Atlantic, Pacific and Indian oceans (covering 72% of the Earth's surface) has risen by 0.06°C since 1995. The situation regarding global warming is far from being under control. As stated by the US Department of Energy's forecast, carbon emissions will increase by 54% above 1990 levels by 2015, making the Earth likely to warm by 1.7-4.9°C over the period 1990-2100 (see Figure 1.1). Such observations demonstrate the need for efforts towards alleviating energy-related environmental concerns in the near future [3].

Figure 1.1 Global mean temperature probability changes, for the years 1990-2100 and 1990-2030.

Source: Omer (2008) [3]. Reproduced with permission of Elsevier.

Achieving higher efficiencies and, if possible, the utilization of renewable energies in power generation technologies will be vital steps in mitigating or reducing these environmental problems, whilst meeting the expected rise in energy demand in the future. With increasing fuel prices and significant pressure to reduce emissions, increasing energy efficiency is considered amongst the most feasible and cost-competitive approaches for reducing CO2 emissions. For instance, Britain wastes 20% of its fossil fuel and electricity which, if used efficiently, would translate into a potential £10 billion annual reduction in the collective fuel bill and a reduction of some 120 million tonnes of CO2 emissions [3]. Unfortunately, even if energy is currently recognized globally as being at the centre of the sustainable development paradigm, the industrial and social development paths favour energy consumption rather than conservation [3].

The significant fuel consumption and CO2 emission issues have to link with the fact that conventional thermal power plants (regardless of the type of fuel used) cannot convert all of the thermal energy supply into useful (mechanical) work. In most cases, more than 50% of the heat added to the working cycle is rejected to the environment. Combined heat and power (CHP) installations are able to use a part of this heat, which would otherwise be wasted in a conventional power plant, to raise the overall first law efficiency to values higher than 80% for the best available technology [3]. This concept enables drastic reductions of the primary energy consumption and cost compared with the independent production of both forms of energy (electricity and thermal energy).

Complementary to energy conversion at high efficiency, substituting fossil fuels with renewable energy sources is envisaged as another means to tackle the aforecited social, economic and environmental problems. Renewable energies are broadly regarded as energy sources that are naturally replenished over a short timescale (i.e. in comparison to the lifetime of a human being), such as sunlight, wind, rain, tides, waves and geothermal heat. They have shown the potential to replace conventional fuels in various distinct areas, such as utility-scale electricity generation, hot water production/space heating, fuels for transportation, and rural (off-grid) energy services [13, 14]. Renewable energy sources have the potential to constitute the future energy sector's backbone, despite some evident shortcomings such as low density and inherent intermittency.

According to the REN21's 2014 report [15], renewables contributed 19% to the world's energy consumption in 2012, and 22% to electricity generation in 2013, using both traditional (biomass) and more innovative renewable energy technologies such as solar power, large wind farms and biofuels [10]. The importance of renewable energy sources has been disseminated widely, and several nations worldwide have decided to invest large sums of money in renewable technologies; such is the case in the US with a total investment of more than $214 billion in 2013, whereas other countries like China are following close behind [15].

Hybrid systems based on the coupling of a microturbine with a high-temperature fuel cell are highly regarded as a solution for future power generation due to their high efficiency, ultra-low emissions and their ability to run on fuels such as hydrogen produced from renewable sources. These systems can achieve very high efficiencies: more than 60% electrical efficiency using natural gas (depending on the low heating value). This efficiency is virtually independent of plant size due to...

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