Fuel Cells E-Book

• Herausgeber: Wiley-VCH
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 579

Veröffentlichungsjahr: 2016

Beschreibung

This ready reference is unique in collating in one scientifically precise and comprehensive handbook the widespread data on what is feasible and realistic in modern fuel cell technology.

Edited by one of the leading scientists in this exciting area, the short, uniformly written chapters provide economic data for cost considerations and a full overview of demonstration data, covering such topics as fuel cells for transportation, fuel provision, codes and standards.

The result is highly reliable facts and figures for engineers, researchers and decision makers working in the field of fuel cells.

Leseprobe

Contents

Cover

Related Titles

Title Page

Copyright

Preface

Part I: Transportation

I-1 Propulsion

I-1.1 Benchmarks and Definition of Criteria

1: Battery Electric Vehicles

References

2: Passenger Car Drive Cycles

Abstract

2.1 Introduction

2.2 Drive Cycles for Passenger Car Type Approval

2.3 Drive Cycles from Research Projects

2.4 Drive Cycle Characteristics

2.5 Graphic Representation of Selected Drive Cycles

2.6 Conclusion

References

3: Hydrogen Fuel Quality

Abstract

3.1 Introduction

3.2 Hydrogen Fuel

3.3 Fuel Quality Effects

3.4 Fuel Quality for Fuel Cell Vehicles

3.5 Single Cell Tests

3.6 Field Data

3.7 Fuel Quality Verification

3.8 Conclusion

References

4: Fuel Consumption

Abstract

4.1 Introduction

4.2 Hydrogen Production

4.3 Hydrogen Packaging

4.4 Hydrogen Consumption in FCEVs

4.5 Conclusion

References

I-1.2 Demonstration

I-1.2.1 Passenger Cars

5: Global Development Status of Fuel Cell Vehicles

Abstract

5.1 Introduction

5.2 Update on Recent Activities of Car Manufacturers

5.3 Key Data and Results from Demonstration Programs

5.4 Technical Data of Fuel Cell Vehicles

5.5 Conclusions

References

6: Transportation – China – Passenger Cars

Abstract

6.1 Introduction

6.2 National R&D Strategy (2011–2015)

6.3 Government Policy

6.4 Published Technical Standards

6.5 Demonstrations

6.6 Commercialization – Case of SAIC Motor

6.7 Conclusions

References

7: Results of Country Specific Program – Korea

Abstract

7.1 Introduction

7.2 FCV Demonstration Program

7.3 Summary

8: GM HydroGen4 – A Fuel Cell Electric Vehicle based on the Chevrolet Equinox

Abstract

8.1 Introduction

8.2 Technology

8.3 Conclusions

Acknowledgments

References

I-1.2.2 Buses

9: Results of Country Specific Programs – USA

Abstract

9.1 Introduction

9.2 FCEB Descriptions

9.3 SunLine Advanced Technology Fuel Cell Electric Bus

9.4 Zero Emission Bay Area Program

9.5 SunLine American Fuel Cell Bus

9.6 Conclusion

References

I-1.3 PEM fuel cells

10: Polymer Electrolytes

Abstract

10.1 Introduction

10.2 Membrane Properties

10.3 Conclusions

References

11: MEAs for PEM Fuel Cells

Abstract

11.1 Introduction

11.2 MEA Basic Components (PEMs, Catalysts, GDLs and Gaskets)

11.3 MEA Performance, Durability, and Cost Targets for Transportation

11.4 MEA Robustness and Sensitivity to External Factors

11.5 Technology Gaps

11.6 Conclusion

References

12: Gas Diffusion Layer

Abstract

12.1 Introduction

12.2 Macroporous Substrate

12.3 Microporous Layer

12.4 Characterization of GDL

12.5 Conclusion

References

13: Materials for PEMFC Bipolar Plates

Abstract

13.1 Introduction

13.2 Composite BP Materials

13.3 Metallic BP Materials

Acknowledgments

References

14: Single Cell for Proton Exchange Membrane Fuel Cells (PEMFCs)

Abstract

14.1 Introduction

14.2 Main Components of a Single Cell for a PEMFC

14.3 Assembly of a Single Cell

14.4 Measurement of a Single Cell Performance

14.5 Conclusions

References

I-1.4 Hydrogen

I-1.4.1 On board storage

15: Pressurized System

Abstract

15.1 Introduction

15.2 High Pressure Storage System

15.3 Cost

15.4 Conclusions

References

16: Metal Hydrides

16.1 Metal Hydrides as Hydrogen Storage Media

16.2 Classes of Metal Hydrides

16.3 How Metal Hydrides Could Be Improved

References

17: Cryo-Compressed Hydrogen Storage

Abstract

17.1 Introduction

17.2 Thermodynamic Principles

17.3 System Design and Operating Principles

17.4 Validation and Safety

17.5 Summary

References

I-1.4.2 On board safety

18: On-Board Safety

Abstract

18.1 Introduction

18.2 High Pressure Fuel Container System

18.3 Hydrogen Refueling Requirements and Safety

18.4 Conclusions

References

I-2 Auxiliary power units (APU)

19: Fuels for APU Applications

Abstract

19.1 Introduction

19.2 Diesel Fuel

19.3 Jet Fuel

19.4 Other Fuels

19.5 Conclusion

References

20: Application Requirements/Targets for Fuel Cell APUs

Abstract

20.1 Introduction

20.2 DOE Technical Targets

References

21: Fuel Cells for Marine Applications

Abstract

21.1 Introduction

21.2 Possible Fuel Cell Systems for Ships

21.3 Maritime Fuel Cell Projects

21.4 Development Goals for Future Systems

21.5 Conclusions

References

22: Reforming Technologies for APUs

Abstract

22.1 Introduction

22.2 Guideline

Appendix 22.A

Abbreviation

List of Symbols

Definitions

References

23: PEFC Systems for APU Applications

Abstract

23.1 Introduction

23.2 PEFC Operation with Reformate

23.3 Application Concepts

23.4 System Design

23.5 System Efficiency

23.6 System Test

23.7 Conclusion

References

24: High Temperature Polymer Electrolyte Fuel Cells

Abstract

24.1 Introduction

24.2 Operating Behavior of Cells and Stacks

24.3 System Level

References

25: Fuel Cell Systems for APU. SOFC: Cell, Stack, and Systems

References

Part II: Stationary

26: Deployment and Capacity Trends for Stationary Fuel Cell Systems in the USA

Abstract

26.1 Fuel-Cell Backup Systems

26.2 Fuel-Cell Combined Heat and Power and Electricity

References

27: Specific Country Reports: Japan

Abstract

27.1 Introduction

27.2 Start of the Sales of Residential Fuel Cell Systems

27.3 Market Growth of the Ene-Farm

27.4 Technical Development of the Ene-Farm

27.5 Sales of the Ene-Farm for Condominiums

27.6 Conclusions

References

28: Backup Power Systems

Abstract

28.1 Introduction

28.2 Application and Power Levels

28.3 Advantages

28.4 Fuel Choice

28.5 Product Parameters

28.6 Economics

28.7 Conclusion

References

29: Stationary Fuel Cells – Residential Applications

Abstract

29.1 Introduction

29.2 Key Characteristics

29.3 Technical Performance

29.4 Economic and Market Status

29.5 Conclusions

References

30: Fuels for Stationary Applications

Abstract

30.1 Introduction

30.2 Natural Gas

30.3 Biogas, Landfill Gas, and Biomethane

30.4 (Bio)ethanol

30.5 Hydrogen

References

31: SOFC: Cell, Stack and System Level

Abstract

31.1 Introduction

31.2 Cell Concepts and Materials

31.3 Cell Designs

31.4 Stack Concepts

31.5 Stationary Systems

31.6 Performance and Durability Parameters

References

Part III: Materials Handling

32: Fuel Cell Forklift Systems

Abstract

32.1 Introduction

32.2 Forklift Classification

32.3 Load Profile of Horizontal Order Pickers

32.4 Energy Supply for Forklifts

32.5 Systems Setup and Hybridization

32.6 Cost Comparison of Different Propulsion Systems for Forklifts

References

33: Fuel Cell Forklift Deployment in the USA

Abstract

33.1 Fuel Cell-Powered Material Handling Equipment

References

Part IV: Fuel Provision

34: Proton Exchange Membrane Water Electrolysis

Abstract

34.1 Introduction

34.2 Bibliographic Analysis of PEM Electrolysis versus Water Electrolysis

34.3 Electrocatalysts Used in PEM Water Electrolysis

34.4 Anode Supports for PEM Water Electrolysis

34.5 Membranes for PEM Electrolysis

34.6 Stack and System Costs in PEM Electrolysis

34.7 PEM Electrolysis Systems in Comparison with Competing Technologies

References

35: Power-to-Gas

Abstract

35.1 Introduction

35.2 Main Components and Process Steps

35.3 Transport and Application of H2 and CH4

35.4 Current Developments: Pilot Plants

35.5 Conclusion

References

Part V: Codes and Standards

36: Hydrogen Safety and RCS (Regulations, Codes, and Standards)

Abstract

36.1 Introduction

36.2 Hydrogen Safety

Non-Metallic Materials

36.3 Hydrogen Regulations, Codes, and Standards (RCS) International Activities

36.4 Conclusions

Acknowledgments

References

Index

EULA

List of Tables

Table 1.1

Table 1.2

Table 1.3

Table 1.4

Table 2.1

Table 3.1

Table 3.2

Table 3.3

Table 3.4

Table 4.1

Table 4.2

Table 4.3

Table 5.1

Table 5.2

Table 5.3

Table 5.4

Table 5.5

Table 5.6

Table 5.7

Table 5.8

Table 5.9

Table 5.10

Table 5.11

Table 5.12

Table 5.13

Table 5.14

Table 5.15

Table 5.16

Table 6.1

Table 6.2

Table 6.3

Table 7.1

Table 7.2

Table 7.3

Table 7.4

Table 8.1

Table 8.2

Table 9.1

Table 9.2

Table 9.3

Table 9.4

Table 10.1

Table 10.2

Table 10.3

Table 10.4

Table 10.5

Table 10.6

Table 11.1

Table 11.2

Table 11.3

Table 11.4

Table 11.5

Table 12.1

Table 12.2

Table 12.3

Table 12.4

Table 12.5

Table 12.6

Table 13.1

Table 14.1

Table 15.1

Table 15.2

Table 15.3

Table 15.4

Table 16.1

Table 17.1

Table 17.2

Table 17.3

Table 17.4

Table 17.5

Table 17.6

Table 18.1

Table 18.2

Table 18.3

Table 19.1

Table 19.2

Table 19.3

Table 19.4

Table 19.5

Table 19.6

Table 19.7

Table 19.8

Table 19.9

Table 20.1

Table 21.1

Table 21.2

Table 21.3

Table 21.4

Table 22.1

Table 22.2

Table 22.3

Table 22.4

Table 22.5

Table 22.6

Table 22.7

Table 23.1

Table 23.2

Table 24.1

Table 24.2

Table 24.3

Table 24.4

Table 25.1

Table 26.1

Table 26.2

Table 26.3

Table 26.4

Table 27.1

Table 29.1

Table 29.2

Table 29.3

Table 29.4

Table 29.5

Table 29.6

Table 30.1

Table 30.2

Table 30.3

Table 30.4

Table 30.5

Table 30.6

Table 31.1

Table 31.2

Table 31.3

Table 31.4

Table 31.5

Table 31.6

Table 31.7

Table 31.8

Table 31.9

Table 31.10

Table 32.1

Table 32.2

Table 32.3

Table 32.4

Table 32.5

Table 32.6

Table 32.7

Table 33.1

Table 33.2

Table 33.3

Table 34.1

Table 34.2

Table 34.3

Table 34.4

Table 34.5

Table 34.6

Table 34.7

Table 35.1

Table 35.2

Table 35.3

Table 35.4

Table 36.1

Table 36.2

List of Illustrations

Figure 1.1

Figure 1.2

Figure 1.3

Figure 1.4

Figure 2.1

Figure 2.2

Figure 3.1

Figure 6.1

Figure 6.2

Figure 6.3

Figure 6.4

Figure 7.1

Figure 7.2

Figure 8.1

Figure 8.2

Figure 8.3

Figure 8.4

Figure 8.5

Figure 8.6

Figure 9.1

Figure 9.2

Figure 9.3

Figure 9.4

Figure 9.5

Figure 9.6

Figure 9.7

Figure 9.8

Figure 9.9

Figure 11.1

Figure 14.1

Figure 14.2

Figure 15.1

Figure 15.2

Figure 17.1

Figure 17.2

Figure 17.3

Figure 17.4

Figure 17.5

Figure 18.1

Figure 18.2

Figure 18.3

Figure 18.4

Figure 21.1

Figure 22.1

Figure 22.2

Figure 22.3

Figure 22.4

Figure 23.1

Figure 24.1

Figure 24.2

Figure 24.3

Figure 24.4

Figure 25.1

Figure 25.2

Figure 25.3

Figure 25.4

Figure 25.5

Figure 26.1

Figure 26.2

Figure 26.3

Figure 26.4

Figure 26.5

Figure 26.6

Figure 26.7

Figure 26.8

Figure 26.9

Figure 27.1

Figure 27.2

Figure 27.3

Figure 27.4

Figure 28.1

Figure 29.1

Figure 29.2

Figure 29.3

Figure 29.4

Figure 31.1

Figure 31.2

Figure 31.3

Figure 32.1

Figure 32.2

Figure 32.3

Figure 32.4

Figure 33.1

Figure 34.1

Figure 34.2

Figure 34.3

Figure 35.1

Figure 35.2

Figure 35.3

Figure 35.4

Figure 35.5

Figure 36.1

Guide

Cover

Table of Contents

Begin Reading

Part 1

Chapter 1

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Related Titles

Gao, F., Blunier, B., Miraoui, A. (eds.)

Proton Exchange Membrane Fuel Cells Modeling

2012

Print ISBN: 978-1-848-21339-5

Bagotsky, V.S.

Fuel Cells

Problems and Solutions, Second Edition

2 Edition

2012

Print ISBN: 978-1-118-08756-5

Jiang, S.P., Yan, Y. (eds.)

Materials for High-Temperature Fuel Cells

2013

Print ISBN: 978-3-527-33041-6

Stolten, D. (ed.)

Hydrogen and Fuel Cells

Fundamentals, Technologies and Applications

2010

Print ISBN: 978-3-527-32711-9

Stolten, D., Emonts, B. (eds.)

Fuel Cell Science and Engineering

Materials, Processes, Systems and Technology

2012

Print ISBN: 978-3-527-33012-6

Edited by Detlef Stolten, Remzi C. Samsun and Nancy Garland

Fuel Cells

Data, Facts and Figures

All books published by Wiley-VCH are carefully produced. Nevertheless, authors, editors, and publisher do not warrant the information contained in these books, including this book, to be free of errors. Readers are advised to keep in mind that statements, data, illustrations, procedural details or other items may inadvertently be inaccurate.

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British Library Cataloguing-in-Publication DataA catalogue record for this book is available from the British Library.

Bibliographic information published by the Deutsche NationalbibliothekThe Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available on the Internet at <http://dnb.d-nb.de>.

© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Boschstr. 12, 69469 Weinheim, Germany

All rights reserved (including those of translation into other languages). No part of this book may be reproduced in any form — by photoprinting, microfilm, or any other means — nor transmitted or translated into a machine language without written permission from the publishers. Registered names, trademarks, etc. used in this book, even when not specifically marked as such, are not to be considered unprotected by law.

Print ISBN: 978-3-527-33240-3ePDF ISBN: 978-3-527-69389-4ePub ISBN: 978-3-527-69391-7Mobi ISBN: 978-3-527-69390-0oBook ISBN: 978-3-527-69392-4

Preface

Fuel cell technology made substantial progress in the last decade, although this was not always reflected in the public mind due to unrealistically high expectations and partial overselling in the previous decade. The automotive industry for one made strong and steady progress and is edging ever closer to bringing fuel cell-based vehicles to market.

Hyundai and Toyota produced cars using the world's first dedicated manufacturing lines for fuel cell vehicles. In the stationary sector, fuel cells also became more prominent through the deployment of over 100,000 residential systems in Japan, amongst other countries, as well as portable applications (the latter, however, remain focused on special market segments and niches).

At this stage, systems analysis with respect to the widespread implementation of fuel cells becomes highly important, particularly in this case. For given that fuel cells constitute a cleaner and more efficient energy conversion solution, they typically substitute existing technologies. Hence, a comparative analysis of performance, longevity and costs is paramount.

This book compiles cutting edge research to comprehensively convey the current status of the technology. It is intended as a data reference book for people familiar with energy analyses and/or fuel cells and hydrogen.

Part ITransportation

I-1 Propulsion

I-1.1 Benchmarks and definition of criteria

1Battery Electric Vehicles

Bruno Gnörich and Lutz Eckstein

RWTH Aachen University, Institut für Kraftfahrzeuge, Steinbachstraße 7, 52074 Aachen, Germany

Keywords: battery electric vehicles; concept car; electric machines; hydrogen fuel cell electric vehicles; Li-ion batteries

In the early years of motor vehicle history, the most frequently used propulsion system was an electric drivetrain with batteries as energy storage. Power sockets were more common than petrol stations. From the 1920s, the increasing density of fueling stations made battery electric vehicles less desirable due to the longer recharging times.

It took many decades before the aspect of emissions and scarcity of primary energy resources (re)surfaced and, as of today, a significant number of series production vehicles from major car manufacturers are available to end customers. E-mobility stakeholders also stress the potential linkage of battery electric vehicles and the energy sector to create a smart grid where vehicles could act as balancing loads when plugged into the charging pole.

In general terms, and with electricity being a secondary energy carrier just like hydrogen, this underlines the necessity to assess the well-to-wheel efficiency, emissions, and sustainability of such drivetrains.

Figure 1.1 illustrates a simplified overview of the well-to-wheel energy conversion for the main propulsion technologies, with focus on the battery electric vehicle (BEV). Electricity can be produced from any of the primary or secondary sources, including hydrogen.

Figure 1.1 Energy conversion pathways for motor vehicles with focus on BEVs [1].

It becomes clear that electric vehicles benefit from the versatile electricity pathways, making them in theory the most sustainably propelled types of vehicles. This includes battery and hydrogen fuel cell electric vehicles (FCEV).

These differ only by the delivery of electricity to the traction motor(s), and this synergy is beneficial when creating BEVs and FCEVs with identical motors.

Battery electric vehicles have several benefits over conventional vehicles. They feature low noise emissions and do not produce local pollutants like NOx, particulate matter, or other toxic substances and gases. They therefore are predestined for urban traffic, where the limited driving range does not obstruct adequate usage.

The average driving range of any passenger vehicle in Germany in 2012 was 49.2 km per day, over an average of 3.9 journeys [1]. The power requirement in urban traffic is approximately 10–15 kWmech, which is significantly lower than the requirement for extra-urban traffic (>30 kW at 100 km h−1). The main bottleneck in this market is the lack of acceptance of a vehicle with limited driving range and high purchase costs.

The only full-range BEV as of early 2015 is the Tesla Model S with its large 85 kWh battery and a range of up to 500 km. Tesla has used a combination of conventional Li-ion battery technology and powerful motors in a very aerodynamic body (cd = 0.24) to create a well-received vehicle in the luxury car segment. It mainly addresses markets with government subsidies, substantial CO2 emissions taxation, or good coverage of quick-charging infrastructure, Tesla's Supercharger stations.

Several BEVs are so-called purpose-designed vehicles that have been specifically developed as electric vehicles and that are not derived from an internal combustion engine (ICE) vehicle (Table 1.1). Tesla's Model S aside, such vehicles are mostly in the micro to compact car segment, like the Peugeot iOn, BMW i3, or Nissan Leaf. Conversion design examples include the Volkswagen e-Golf and the Smart fortwo electric drive. In the case of newly developed vehicles such as the Mercedes-Benz B-class, different propulsion options have been considered from the start of the development process, using one platform for conventional versions and an adapted platform for natural gas powered and electric versions.

Table 1.1 Series production battery electric vehicles. (Source: manufacturers.)

Parameter

Smart fortwo ed

Peugeot iON

Nissan Leaf

BMW i3

VW e-Golf

Mercedes B-Class

Tesla Model S

Vehicle data

Class

Sub-compact

Compact

Compact

Lower middle

Lower middle

Lower middle

Luxury class

Price (2015) (€)

23 680

29 393

23 790

34 950

34 900

27 102

85 900

Driving performance

Range (km)

145

150

200

190

190

200

502

Consumption (kWh per 100 km)

15.1

15.9

12.4

12.9

12.7

16.6

18.1

0 to 100 km h

−1

(s)

11.5

15.9

11.3

7.2

10.4

7.9

4.6

Maximum speed (km h

−1

)

125

130

145

150

140

160

250

Battery

Type

Lithium ion

Lithium ion

Lithium ion

Lithium ion

Lithium ion

Lithium ion

Lithium ion

Capacity (kWh)

17.6

16

24

18.8

24.2

28

85

Max. charging power (kW)

22

62.5

6.6

4.6

17.6

11

120

Electric motor

Type

PSM

PSM

SM

HSM

PSM

SM

ASM

Nominal power (kW)

55

49

80

125

85

132

2 × 384

Torque (Nm)

130

196

280

250

270

340

491

In general, electric drivetrains have a moderate amount of drivetrain components and a straightforward structure. The novel components are the battery system and the electric motor. Furthermore, auxiliary components need adjusting such as the steering and braking system as well as the heating and cooling systems (thermal management).

The latter has become a vital aspect of drivetrain development and aims to combine energy demand analyses and efficiency optimization across all on-board energy requirements. Examples include the use of thermal inertias of components such as the battery, the passenger compartment, or thermochemical storage systems and to include thermal management in the vehicle energy management system.

Battery electric vehicles use high-energy batteries to maximize driving range. Today, almost all BEVs use Li-ion batteries with energy densities of up to 150 Wh kg−1. For example, the Volkswagen e-Golf has a battery with a density of 140 Wh kg−1 (230 Wh l−1) and a total energy capacity of 24 kWh at 323 V [2]. This results in a total driving range of up to 190 km. The driving range is influenced by several factors, like driving resistance (e.g., tyre pressure, load, topography), driving speed pattern (acceleration, velocity), and battery specific parameters like temperature and its state of health. The aim to increase the energy density is therefore a high priority. From an automotive point of view, the specifications must also cover costs, thermal management, durability, and end-of-life aspects.

Notable technologies today are mostly based on lithium ion batteries but also on nickel-metal-hydride batteries (e.g., Toyota) and double layer capacitors (supercapacitors) for use in high-power applications (e.g., KERS, heavy duty) (Table 1.2). In BEVs, they could be used as an optional add-on for high-performance applications.

Table 1.2 Specifications of different battery types used in electric vehicles (BEV/HEV). (Source: manufacturers.)

NiMH

Li-ion

Li-ion

Supercapacitor

Manufacturer

PEVE

Hitachi

Sanyo

Maxwell

Shape

Prismatic

Cylindrical

Prismatic

Cylindrical

Cathode

Ni(OH)

2

LiMn

2

O

4

LiNiMnCo

Graphite

Anode

Rare earth AB

5

Amorphous carbon

Amorphous carbon

Graphite

Cell capacity (Ah)

6.5

4.4

25

0.56

Cell voltage (V)

1.2

3.3

3.6

2.7

Energy density (Wh kg

−1

)

46

56

76

5.4

Power density (Wh kg

−1

)

1300

3000

600

6600

Operation temperature (°C)

−20 to +50

−30 to +50

−30 to +50

−40 to +65

Market

Toyota HEV

GM HEV

VW BEV

Faun HEV

Electrochemical high temperature cells (e.g., ZEBRA) are no longer considered for most applications in passenger cars due to their critical thermal management. Apart from capacitors, all automotive battery technologies are secondary cells with reversible electrochemical energy conversion, an essential prerequisite for electric cars.

In principle, all of the energy storage technologies presented here are feasible for traction application in road vehicles. Due to their limited energy and power density, lead-acid batteries only play a role in niche applications and two-wheel vehicles.

Electric machines are electromechanical converters, where energy conversion takes place by means of a force on the mechanical and induced voltage on the electrical side. In principle, every electric machine can be operated as motor or as a generator. For every electric machine, operational limits for speed, torque, and power exist (Figure 1.2). A distinction must be made between nominal values and maximum values. Nominal values (MNom, PNom) can be applied permanently; maximum values (Mmax, Pmax) only for a short period, otherwise mechanical and thermal failure may occur and affect the durability of the machine [1].

Figure 1.2 Operating range of electric machines [1].

Operation of electric machines can be divided into two areas: base load range and field weakening range. In the base load range the machine is capable of delivering maximum torque (MNom or MMax) at all speeds from standstill. Nominal power is then available at nominal speed (nNom):

(1.1)nNom=PNom2πMNom

For a permanent operation the nominal power must not be exceeded. As a result, the output torque decreases with higher speeds:

(1.2)M=PNom2πnwithPNom=const.

Equation (1.2) describes the area of constant power, achieved by a weakening of the magnetic field.

DC machines use DC current to induce an electromagnetic field to drive the rotor, whereas AC machines are driven by alternating current. Today, almost all machines used in electric vehicles are synchronous or asynchronous three-phase AC machines due to their high efficiency (Table 1.3). High efficiency can also be achieved with permanently excited machines, but their permanent magnets are expensive. Transverse flux or reluctance machines combine the characteristics of the other machine types.

Table 1.3 Basic categories and examples of electric machines.

Electric machines

DC machines

AC machines

Asynchronous

Synchronous

Electrical excitation

Permanent excitation

Advanced

(BL) DCM (brushless) DC motor

ASM induction (asynchronous motor)

SM (synchronous motor)

PSM (permanent magnet synchronous motor)

SRMPSM (switched reluctance motor)

TFMPSM (transverse flux motor)

HSMPSM (hybrid synchronous motor)

Induction (asynchronous) machines (ASM) are powered by electromagnetic induction from the magnetic field in the stator winding. The rotation of the magnetic field is asynchronous to the operating speed of the machine. This is referred to as the slip of the ASM, and is necessary for torque transfer (Table 1.4). Example vehicles are Tesla's Roadster and Model S.

Table 1.4 Technical assessment of selected types of electric machines [3].

Motor type

ASM

SM

PSM

HSM

Control

O

+

O

O

Noise emissions

O

+

++

++

Thermal limits

++

+

O

O

Costs

+

O

−

−

Safety

++

++

O

O

Maximum speed (min

−1

)

>10 000

>10 000

>10 000

>12 000

Continuous torque (Nm kg

−1

)

0.60–2.65

0.60–0.75

0.95–1.72

2.08–3.43

Continuous power (kW kg

−1

)

0.20–0.89

0.15–1.10

0.30–1.07

1.12–1.82

Maximum efficiency (%)

83–91

81–95

81–95

95

Example vehicle

Tesla Model S

Renault Fluence Z.E.

Smart Fortwo ed

BMW i3

Synchronous motors (SMs) contain three-phase electromagnets and create the magnetic field rotating synchronous to the rotor speed. Renault's Fluence Z.E. uses a synchronous machine as traction motor. Permanent magnet synchronous machines (PSM) contain neodymium magnets or other rare earth magnets to create the electromagnetic field. Example vehicles are the Smart fortwo electric drive and the Volkswagen e-Golf.

Hybrid synchronous machines (HSM) are a specific type of synchronous machine containing both permanent magnets and electromagnetic winding. This permits higher motor speeds due to the stronger magnetic field. The BMW i3 uses HSM technology.

Depending on the concept, electric machines can be placed at different positions of the drivetrain. There are many possibilities from a simple connection to the gearbox to direct integration into the gearbox. A special configuration is the wheel hub drive, which represents an integration of the electric machine directly into the wheel hub. This is beneficial with regard to the vehicle package, as differentials and drive shafts become superfluous, and in view of functionalities that can be implemented into the propulsion algorithm, such as ABS, traction control, and torque vectoring. However, the higher unsprung mass needs to be addressed in suspension design. Wheel hub motors are not yet deployed in any series (passenger) vehicle. Integrative solutions featuring lower mass are currently being developed, for example, the Active Wheel system by Michelin with a nominal power of 30 kW per wheel and a mass of 7 kg [4].

Electric machines for traction applications in road vehicles are currently substantially more expensive than combustion engines of identical power. Synchronous machines cost approximately €50 kWmech−1 including voltage converter, which is four-time higher than for combustion engines [5].

Drivetrain topologies in battery electric vehicles can consist of twin motors powering individual wheels to permit versatile control strategies such as torque vectoring for e-differential applications or innovative steering geometries for minimal turning circles, as seen in the recent SpeedE BEV concept car (Figure 1.3) [6]. It features 400 V twin motors at the rear wheels and a 48 V steer-by-wire system with a maximum steering angle of 90°.

Figure 1.3 Innovative steering sytsem in the SpeedE BEV concept car with twin RWD motors and torque vectoring. (Source: fka.)

The SpeedE vehicle also features steering with sidesticks instead of a steering wheel, which allows for new interior design layouts and innovative operability concepts (Figure 1.4).

Figure 1.4 Minimal turning circle with electric torque vectoring in the SpeedE BEV concept car.

Recent BEV developments and market success of some vehicles show that electric vehicles are mature and that they will grow their share in the vehicle population for the foreseeable future. R&D progress, especially in battery and motor technology, will strengthen electric and sustainable mobility.

It may be the new driving experience features that pave the way for even more EVs in the future, regardless of the drivetrain technology itself. X-by-wire, connectivity, and user interface novelties will have an impact on the EV market prospects, since these innovations will need electric energy to function.

This underlines the fact that developments for BEVs are not necessarily showstoppers for FCEVs but can complement the effort to create clean and sustainable mobility for the future.

References

1.

Eckstein, L. (2010)

Alternative Vehicle Propulsion Systems

, Schriftenreihe Automobiltechnik, Aachen, ISBN: 978-3-940374-33-2.

2.

Huslage, J. (7 October 2014) The next generation of automotive batteries! Presented at World of Energy Solutions, Stuttgart, Germany, 6–8 October 2014.

3.

Ernst, C. (2014)

Energetische, ökologische und ökonomische Lebenszyklusanalyse elektrifizierter Antriebsstrangkonzepte

, Schriftenreihe, Automobiltechnik, Dissertation RWTH Aachen University, Aachen, ISBN: 978-3-940374-80-6.

4.

Oliva, P. (2009) Michelin arbeitet seit zwölf Jahren am neuen Rad. Interview, Automobiltechnische Zeitschrift (ATZ), March 2009.

5.

Gnörich, B. (2009) HySYS Technical Workshop. Result of expert discussion. Aachen, May 2009.

6.

Eckstein, L.

et al.

(2013) The wheel-individually steerable front axle of the research vehicle SpeedE. Presented at the Aachen Colloquium Automobile and Engine Technology, Aachen, 7–9 October 2013.

2Passenger Car Drive Cycles

Thomas Grube

Forschungszentrum Jülich GmbH, IEK-3: Electrochemical Process Engineering, Leo-Brandt-Strasse, 52425 Jülich, Germany

Abstract

The evaluation of road vehicles requires standardized methods for the determination of fuel consumption and emissions. A constitutive part of such methods is the drive cycle that is typically used for chassis dynamometer tests. A large variety of country or region specific drive cycles for vehicle type approval exists worldwide. Other drive cycle definitions result from research projects related to specific assessments in vehicle development and evaluation. This chapter introduces selected drive cycles that are considered relevant as they apply for regions with large vehicle fleets or are otherwise commonly used. The focus here is on passenger cars; however, notably, such drive cycle definitions also exist for buses and trucks.

Keywords: alternative powertrains; drive cycle; well-to-tank analysis

2.1 Introduction

For the assessment of environmental impact and resource use of vehicle and fuel systems, fuel consumption and air pollutant emissions of vehicles must be determined. To achieve reproducible results of respective measurements standardized test procedures must be applied. This is carried out on the basis of legal regulations in many countries. Ambient conditions, fuel specifications as well as load conditions of the vehicles tested are defined here. Moreover, a drive cycle that consists of time-dependent speed data points or rotational-speed and torque data points is detailed. Special rules may apply for alternative powertrain configurations.

Vehicle load, traffic, topographic road conditions, and driver behavior have, among others, a great impact on fuel economy and exhaust emissions. Consequently, drive cycles strongly simplify real-world car driving. The selection of a preferable realistic drive cycle is therefore decisive regarding environmental performance ratings and, not least, consumer information.

Besides their application for type approval purposes, drive cycles are used for specific tasks in vehicle development and for specific assessments in the field of energy systems analysis, particularly in tank-to-wheel analyses of road vehicles.

2.2 Drive Cycles for Passenger Car Type Approval

In the following, relevant examples of up-to-date drive cycles that are used for type approval procedures are presented. The respective speed–time graphs of the above-mentioned drive cycles can be found below in Figure 2.2 (numbers 1–14). A more comprehensive compilation of in total 256 drive cycles can be found in Barlow et al. [1]. Moreover, Rakopoulos [2] and Delphi [3] provide summarized information on worldwide vehicle emission standards also including the respective drive cycles.

The drive cycle that is relevant for type approval of light passenger and commercial vehicles in the European Union is specified in Council Directive 70/220 [4]. In the literature it is referred to as the NEDC (New European Drive Cycle) or MVEG-B (Motor Vehicle Emissions Group) drive cycle. The MVEG-B drive cycle consists of two parts that are also separately used: the ECE (Economic Commission for Europe) drive cycle for urban driving and the Extra Urban Drive Cycle (EUDC) representing driving at elevated speeds. With regulation (EC) No. 715/2007 of the European Parliament and of the Council [5] the European Commission is asked to review the drive cycle and possibly replace it “…reflecting changes in vehicle specifications and driver behavior” [5, p. L171/172]. The proposed new drive cycle for the European Union is the Worldwide Harmonized Light Duty Test Cycle (WLTC).

Drive cycles related to the US Federal (Tier 1-3) and California (Low Emission Vehicle, LEV 1-3) vehicle emissions legislation are the Urban Dynamometer Driving Schedule (UDDS), the Federal Test Procedure (FTP), the Highway Fuel Economy Test (HWFET), and the US06 and the SC03 driving cycles. US06 and SC03 supplement the FTP with the aim of also including driving with higher accelerations and higher speeds (US06) and the use of air conditioning (SC03) [6]. The FTP drive cycle is basically the UDDS repeating the first 505 s of the UDDS at its end.

Vehicle type approval in Japan requires the new drive cycle JC08 that came into effect in 2011, replacing the former cycles 11 Mode, known as Cold Cycle and 10–15 Mode known as Hot Cycle. These two outdated drive cycles are not shown in Figure 2.2 below.

2.3 Drive Cycles from Research Projects

Apart from the aforementioned drive cycles for type approval procedures various research activities, international projects and other initiatives lead to the definition of drive cycles that should reflect car driving in a more representative way. Three examples are given here based on information and data given in Reference [7]. The research projects MODEM and HYZEM resulted in the definition of drive cycle sets on the basis of monitoring fleets of 58 (MODEM) and 77 (HYZEM) cars. These cars were operated in France, UK, Germany, and Greece. The total distance covered was more than 160 000 km for the two projects. The subsequent ARTEMIS project made use of the databases provided by MODEM and HYZEM and included additional data from car monitoring in Italy and Switzerland. The MODEM, HYZEM, and ARTEMIS full drive cycles and the respective sub-cycles can be found in Figure 2.2, numbers 15–26 (see below).

2.4 Drive Cycle Characteristics

Selected parameters that allow for comparison of drive cycles will be presented in the following. The equations used for the calculation of the respective values are based on information in Reference [1] and rely on speed–time data points. The time resolution of available drive cycles is typically one second. During this time interval acceleration is considered constant. Speed–time values from real dynamometer tests or from dynamic simulations may deviate as the desired values from the drive cycle definitions cannot accurately be followed by real drivers or by the driver model that is part of a control circuit in dynamic simulations.

Basic characteristics of drive cycles are duration, distance, and average speed (see Eqs. (2.1)–(2.3)):

(2.1)tcycle=∑i=2nti−ti−1

(2.2)scycle=∑i=2nti−ti−1vi3.6

(2.3)v¯cycle=scycletcycle

Definitions: n is the number of speed–time data points; speed values are given in km h−1; indices are one-based, that is, the first index is one.

With increasing average speed, drive cycles can roughly be grouped into urban, extra-urban, or rural and motorway driving. Mechanical energy use basically increases with average speed. However, urban driving may also show high energy turnover, if frequency and duration of acceleration periods increase. For this reason, various parameters can be used to provide additional information on drive cycle characteristics. Examples of such parameters are: relative positive acceleration (RPA) and relative negative acceleration (RNA) and standstill time (see Eqs. (2.4)–(2.6)). The RPA and RNA are measures for the dynamic properties of a drive cycle. High values indicate high numbers of acceleration and deceleration periods:

(2.4)RPA=1s∑i=1naivi3.6,(a>0)0,(a≤0)

(2.5)RPA=1s∑i=1naivi3.6,(a<0)0,(a≥0)

(2.6)xt,standstill=ti−ti−1,(vi=0ˆai=0)0,(else)tcycle⋅100%

The calculation results of Eqs. (2.1)–(2.6) related to the 26 drive cycles presented in this chapter can be found in Table 2.1. It can be seen that drive cycle durations range from 323 to 3207 s. Values for the total distance are between 1.7 km (MODEM-slow urban) and 61 km (HYZEM). Average speeds are high for the MODEM-motorway (102 km h−1) and ARTEMIS-motorway (97 km h−1) cycles and low for the drive cycles MODEM-slow urban (14 km h−1) and ECE and ARTEMIS-urban (both with 18 km h−1).

Table 2.1 Drive cycle characteristics of selected passenger car drive cycles. For speed–time graphs see Figure 2.2. RPA: relative positive acceleration; RNA: relative negative acceleration. For equations related to the displayed parameters see Section 2.4.

Cycle name

Duration (s)

Distance (km)

Average speed (km h

−1

)

RPA (m s

−2

)

RNA (m s

−2

)

Relative time standing (%)

(1) MVEG-B

1180

11

33

0.12

−0.11

24

(2) ECE

780

4.0

18

0.15

−0.13

31

(3) EUDC

400

6.9

62

0.09

−0.09

10

(4) WLTC

1800

23

46

0.16

−0.15

11

(5) WLTC-low

589

3.1

19

0.22

−0.20

25

(6) WLTC-middle

433

4.7

39

0.21

−0.19

11

(7) WLTC-high

455

7.1

56

0.14

−0.13

6.4

(8) WLTC-very high

323

8.3

92

0.13

−0.12

1.9

(9) UDDS

1372

12

31

0.19

−0.16

18

(10) FTP

1874

18

34

0.18

−0.16

18

(11) HWFET

765

17

78

0.09

−0.07

0.65

(12) SFTP-US06

600

13

77

0.22

−0.20

6.7

(13) SFTP-SC03

594

5.8

35

0.22

−0.19

18

(14) JC08

1204

8.2

24

0.19

−0.17

29

(15) MODEM

1948

25

46

0.19

−0.17

15

(16) MODEM-slow urban

451

1.7

14

0.28

−0.23

33

(17) MODEM-road

695

8.5

44

0.23

−0.21

11

(18) MODEM-free flow urban

352

2.2

23

0.32

−0.28

18

(19) MODEM-motorway

450

13

102

0.12

−0.11

1.8

(20) HYZEM

3207

61

68

0.15

−0.14

8.5

(21) HYZEM-urban

560

3.5

22

0.28

−0.24

24

(22) HYZEM-rural

843

11

48

0.22

−0.20

9.8

(23) HYZEM-highway

1804

46

92

0.13

−0.12

3.2

(24) ARTEMIS-urban

993

4.9

18

0.34

−0.28

26

(25) ARTEMIS-road

1082

17

57

0.18

−0.17

2.8

(26) ARTEMIS-motorway

1068

29

97

0.14

−0.13

1.4

RPA and RNA values are typically close. ARTEMIS-urban (0.34 and −0.28) and MODEM-free flow urban (0.32 and −0.28) are in the higher range of values. EUDC (0.09 and −0.09) and HWFET (0.09 and −0.07) show comparably low RPAs and RNAs. Interestingly, the ARTEMIS-urban drive cycle with the shortest distance (4.9 km) and one of the lowest average speeds (18 km h−1) has the overall highest RPA and RNA (0.34 and −0.28). Other cycles with high RPAs are the US cycles UDDS, FTP, US06, and SC03. Finally, high shares of standstill periods can be found for MODEM-slow urban (33%) and JC08 (29%).

Based on passenger car simulations carried out in Reference [8] results for the mechanical energy requirements of the drive cycles presented here are displayed in Figure 2.1. Considering urban driving, it can be seen that for drive cycles with high RPAs and RNAs the mechanical energy values are also comparably high. In extra-urban driving ARTEMIS-road, EUDC, and WLTC-high show lowest mechanical energy values due to comparably low average speeds. For motorway driving the HWFET cycle has the lowest mechanical energy, again due to a low average speed that is here combined with a low RPA.

Figure 2.1 Mechanical energy (Em) at the wheels of a passenger car with a mass of 1251 kg, a cross-sectional area of 2.1 m2, and an air drag coefficient of 0.32. Values are derived from dynamic powertrain simulation results [8]. The numbers in the figure correspond to the numbering in Table 2.1.

2.5 Graphic Representation of Selected Drive Cycles

Speed–time data points of the selected drive cycles are shown in Figure 2.2. The first part of the figure is dedicated to drive cycles that are part of vehicle type approval regulations (drive cycles with the numbers 1–14). Subsequent drive cycles have been designed on the basis of data from vehicle monitoring in international research projects. Further explanations can be found in Sections 2.2 and 2.3. Descriptive parameters that allow for characterization of drive cycles have been introduced in Section 2.4.

Figure 2.2 Speed–time graphs of selected drive cycles. The drive cycle numbers correspond to the numbering in Table 2.1.

2.6 Conclusion

This chapter has presented relevant drive cycles designed for vehicle type approval and for other specific tasks of vehicle powertrain evaluation. Some parameters that allow for a first characterization of drive cycles regarding their dynamic properties and mechanical energy requirements have been defined. Consequently, the drive cycle-specific spectrum of load points in combination with the performance characteristics of powertrain configurations is decisive for the actual results of fuel economy and emissions assessments. In this regard drive cycles are widely used as the basis for dynamometer tests and as time-dependent input variables for dynamic powertrain simulations. Such simulations may usefully be applied for technical development as well as for various systems analysis tasks. Measurements based on dynamometer and real-word tests of vehicles, however, provide the required data for vehicle type approval as well as for environmental assessments.

References

1.

Barlow, T.J.

et al.

(2009)

A Reference Book of Driving Cycles For Use in the Measurement of Road Vehicle Emissions

, Transportation Research Laboratory (TRL), Wokingham, Berkshire, UK.

2.

Rakopoulos, C.D. and Giakoumis, E.G. (2009)

Diesel Engine Transient Operation: Principles of Operation and Simulation Analysis

, Springer, London. ISBN: 978-1-84882-375-4.

3.

Delphi Automotive LLP (2012) Worldwide Emissions Standards – Passenger Cars and Light Duty Vehicles.

4.

The Council of the European Communities, Brussels (2006) Council Directive of 20 March 1970 on the approximation of the laws of the Member States on measures to be taken against air pollution by emissions from motor vehicles.

5.

European Commission, Brussels (2007) Regulation (EC) No 715/2007 of the European Parliament and of the Council of 20 June 2007 on type approval of motor vehicles with respect to emissions from light passenger and commercial vehicles (Euro 5 and Euro 6) and on access to vehicle repair and maintenance information, in Commission, E. (ed.).

6.

Environmental Protection Agency (1996) Final Regulations For Revisions to the Federal Test Procedure for Emissions from Motor Vehicles, Federal Register/Vol. 61, No. 205.

7.

André, M. (2004) The ARTEMIS European driving cycles for measuring car pollutant emissions.

Sci. Total Environ.

,

334–335

, 73–84.

8.

Grube, T. (2014). Potential der Stromnutzung in Pkw-Antrieben zur Reduzierung des Kraftstoffbedarfs. Technische Universität Berlin, Fakultät V – Verkehrs- und Maschinensysteme, Dissertation.

3Hydrogen Fuel Quality

James M. Ohi

3024 Carter Circle, Denver, CO 80222, USA

Abstract

This chapter gives a brief overview of fuel quality as specified in ISO 14687-2:2012 for hydrogen dispensed for use in polymer electrolyte fuel cell (PEMFC) road vehicle systems.

Keywords: fuel quality; hydrogen fuel; ISO 14687-2:2012; PEM fuel cells; road vehicle systems

3.1 Introduction [1]

An international effort to establish a fuel quality standard for hydrogen began in 2004 to address the accelerating pace of fuel cell vehicle (FCV) demonstration projects in Asia, North America, and Europe. Adoption of such a standard would remove one variable in the data obtained from these demonstration projects and would also facilitate eventual commercialization of fuel cell vehicles. The contaminants and their recommended limits included in the standard published in 2012 are shown in Table 3.1. Verification of fuel quality is to be conducted at the dispenser nozzle under applicable standardized sampling and analytical methods or at other locations or methods acceptable to the supplier and customer. As the table was based on then current knowledge, contaminants not listed should not be assumed to be benign.

Table 3.1 Directory of limiting characteristics (maximum allowable limits of contaminants) ISO 14687-2:2012.

Characteristics (assay)

Type I, Type II Grade D

Hydrogen fuel index (minimum mole fraction)

a)

99.97%

Total non-hydrogen gases

300 µmol mol

−1

Maximum concentration of individual contaminants (

µmol mol

−1

)

Water (H

2

O)

5

Total hydrocarbons

b)

(methane basis)

2

Oxygen (O

2

)

5

Helium (He)

300

Total nitrogen (N

2

) and argon (Ar)

b

100

Carbon dioxide (CO

2

)

2

Carbon monoxide (CO)

0.2

Total sulfur compounds

c)

(H

2

S basis)

0.004

Formaldehyde (HCHO)

0.01

Formic acid (HCOOH)

0.2

Ammonia (NH

3

)

0.1

Total halogenated compounds

d)

(halogenate ion basis)

0.05

Maximum particulates concentration

1 mg kg

−1

Note: For the constituents that are additive, such as total hydrocarbons and total sulfur compounds, the sum of the constituents are to be less than or equal to the acceptable limit. The tolerances in the applicable gas testing method are to be the tolerance of the acceptable limit.

a)

The hydrogen fuel index is determined by subtracting the “total non-hydrogen gases” in this table, expressed in mole percent, from 100 mole percent.

b)

Total hydrocarbons include oxygenated organic species. Total hydrocarbons are measured on a carbon basis (µmol-C mol

−1

). Total hydrocarbons may exceed 2 µmol mol

−1

due only to the presence of methane, in which case the summation of methane, nitrogen, and argon is not to exceed 100 ppm.

c)

As a minimum, includes H

2

S, COS, CS

2

, and mercaptans, which are typically found in natural gas.

d)

Includes, for example, hydrogen bromide (HBr), hydrogen chloride (HCl), chlorine (Cl

2

), and organic halides (R–X).

3.2 Hydrogen Fuel

Given the near-term focus of the standard, contaminants and their limitations are specified for hydrogen produced and purified by steam methane reforming (SMR) of natural gas and pressure-swing adsorption (PSA), respectively, and stored on board FCVs with high-pressure gaseous storage containers. Testing and analysis were focused on five “critical constituents”: carbon monoxide (CO), sulfur (S) species, ammonia (NH3), methane (CH4) and other inert gases, and particulate matter (PM) under 10 microns in diameter. These constituents are those most likely to affect PEM fuel cell performance and durability as well as the cost of hydrogen produced by SMR and purified by PSA to the levels required by the standard. Table 3.2 shows the relative difficulty of removing these key contaminant species from hydrogen produced by SMR and purified by PSA.

Table 3.2 Relative difficulty of removing selected contaminants species from hydrogen produced by SMR and purified by PSA. (Source: Chevron Technology Ventures.)

Species

Adsorption force

ISO 14687 specification (ppm)

SMR (mol.%)

Purification ratio for SMR

Overall effect

Helium (He)

Zero

300 (total inert)

500 ppm

5

Not possible

Hydrogen (H

2

)

Weak

99.97%

75–80

Impacts PSA recovery and capital cost

Oxygen (O

2

)

5

—

—

Impacts PSA recovery and capital cost

Argon (Ar)

100 (total inert)

500 ppm

5

Impacts PSA recovery and capital cost

Nitrogen (N

2

)

100 (total inert)

1000 ppm

10

Impacts PSA recovery and capital cost

Carbon monoxide (CO)

0.2

0.1–4

200 000

Impacts PSA recovery and capital cost

Methane (CH

4

)

2 (incl. THC)

0.5–3

15 000

Impacts PSA recovery and capital cost

Carbon dioxide (CO

2

)

2

15–18

90 000

Relatively easier to remove

Total HCs

2 (incl CH

4

)

0.5

2500

Relatively easier to remove

Ammonia

Strong

0.1

Low ppm

Relatively easier to remove

Total sulfur

Strong

0.004

Relatively easier to remove

Halogenates

Strong

0.05

Relatively easier to remove

Water (H

2

O)

Strong

5

Dew point

Relatively easier to remove

3.3 Fuel Quality Effects

The effects of minute amounts of specific contaminants on PEM fuel cell performance and durability must be considered within the larger context of the causes and mechanisms of PEM fuel cell degradation, that is, the gradual decline in power output during operation in road vehicles. These mechanisms include degradation of mechanical properties due to dissolution and sintering of platinum particles, thinning of the membrane, and corrosion of carbon support materials [2]. Contaminants such as CO and hydrogen sulfide (H2S) adsorb on the surface of the catalyst and impede the electrode charge-transfer process, leading to losses due to higher cell overpotential. Contaminants such as NH3 form cations that through ion exchange with protons in the ionomer inhibit proton conduction and create large ohmic losses. Contaminants can also decrease mass transfer by changing water and/or gas transport in the gas diffusion layer. The effects of fuel contaminants on performance and durability are themselves complex and are just one contributing factor among many other considerations discussed in References [2,3].

3.4 Fuel Quality for Fuel Cell Vehicles

Hydrogen quality must be maintained from the fueling nozzle receptacle to the anode inlet, which encompasses on-board storage and balance-of-plant (BOP) fuel system components. Fuel quality must be considered in the context of the synergistic operation of the PEM fuel cell vehicle subsystems that are critical to overall system efficiency and durability. For example, efficient compression, cleanup, and delivery of air are critical to cathode operation, and the heat exchange subsystem must maintain uniform stack temperature during cold and hot thermal and load excursions. The water management subsystem must maintain consistency in stack performance from sub-freezing to high temperature and low relative humidity (RH) operations. Furthermore, the hydrogen storage and delivery subsystem affects anode performance and life, particularly since a highly active low anode catalyst loading is necessary to meet system cost objectives. Vehicular operations that are critical to fuel cell performance include temperature of operation, shut down/start up procedure, extent of time operating at idle and full load potential (i.e., degree of hybridization, etc.), and transient/steady-state demands, among other parameters.

3.5 Single Cell Tests

The maximum allowable concentrations of selected non-hydrogen constituents are based on a limited number of tests under a small set of primarily constant operating conditions using single-cells that do not reflect the state-of-art of PEM fuel cell design and engineering. That said, the specifications represent a consensus of international experts from industry, universities, and national laboratories and, as stated in ISO 14687-2, they should provide adequate requirements for the pre-commercial phase of technology development of PEM fuel cells for road vehicles. Each test laboratory followed a cell conditioning procedure based on recommendations from the cell manufacturer. The following parameters and conditions were followed by each laboratory for baseline testing:

temperature: 80 °C;

RH: 75% anode/25% cathode (in accordance with manufacturer recommendations);

pressure: 150 kPa (abs);

electrical load: 1 A cm

−2

stoics: 1.2/2.0 (anode/cathode).

Given the limited time available, testing focused on obtaining critical data points:

contaminants to be tested: CO, NH

3

, halogenates, ISO mixture (CO, H

2

S, NH

3

, inerts);

contaminant levels: two for each contaminant – (1) at ISO specification level, (2) at 10× specification level;

test duration: (300 h or until performance drops by >60 mV) or as suitable for a contaminant.

As an example, the results of single cell tests for the effects of CO are summarized in Figure 3.1. The test conditions included anode platinum loading of 0.05 mg cm−2, constant current (1 A cm−2), 100% relative humidity at 80 °C, and constant dosage (20 ppm h−1 CO) obtained by varying both concentration and exposure times. These results show that cell performance losses increase with CO concentration but decrease with cell temperature.

Figure 3.1 Summary of CO tests with 0.05 mg-Pt cm−2 at different temperatures [4].

3.6 Field Data

Data on the effects of fuel quality on the performance and durability of PEM fuel cell vehicles under real-world fueling and driving conditions are very limited. Such vehicles have been and continue to be demonstrated in Asia, Europe, and North America, but the main focus of these demonstrations has been on key technical targets, primarily durability (hours of FC stack operation) and vehicle range. Fueling with hydrogen is at a pre-commercial stage, and the quality of such fuel, delivered or produced on-site, is controlled carefully by fuel providers to minimize or eliminate the effect of fuel quality on the performance and durability of the very expensive PEM fuel cell demonstration vehicles. The Japan Hydrogen and Fuel Cell Demonstration Project (JHFC) was the first demonstration in the world of concurrent operation of stations with hydrogen produced from different feedstocks and methods. These feedstocks and methods included: reforming of natural gas, naptha, gasoline, methanol, LPG, and kerosene; electrolysis of water; and liquefaction of hydrogen. Furthermore, JHFC gathered and made available data on fuel quality from these stations. These data were derived from continuous monitoring of CO and CH4 at the PSA exit of six stations and batch analysis of N2, CO, CO2, CH4, O2, and H2O at different intervals (bimonthly, quarterly, semiannually) at various stations. Table 3.3 shows fuel quality data in parts per million (ppm) from one station (Senju) using natural gas reformed on site.

Table 3.3 Fuel quality data (ppm) from the Senju fueling station (ND: “not detected”).

March 2004

February 2005

September 2005

December 2007

December 2008

CO

0.02

0.02

ND

ND

0.01

CO

2

ND

ND

ND

ND

ND

CH

4

0.08

ND

0.08

ND

ND

NMHC

ND

ND

ND

ND

ND

C

6

H

6

ND

ND

ND

ND

ND

S-compounds

ND

ND

ND

ND

ND

MeOH

ND

ND

ND

ND

ND

HCHO

ND

ND

ND

ND

ND

CH

3

CHO

ND

ND

ND

ND

ND

HCOOH

ND

ND

ND

ND

ND

CH

3

COCH

3

ND

ND

ND

ND

ND

NH

3

ND

ND

ND

ND

ND

Halogen

—

—

—

ND

ND

O

2

ND

ND

ND

ND

ND

H

2

O

24.0

0.9

ND

ND

ND

Ar

4.95

0.11

0.73

1.5

1.34

N

2

3.03

0.12

3.59

10.4

6.91

He

ND

ND

ND

ND

ND

3.7 Fuel Quality Verification

Standardized analytical methods and instrumentation are required to verify compliance with the specifications. ASTM International developed and is validating consensus analytic procedures to enable laboratories to verify whether a particular fuel sample meets these specifications using standardized instrumentation and test procedures [6]. Table 3.4 shows analytical sampling and measurement of contaminants at hydrogen fueling stations conducted by the JHFC. These data indicate that existing analytical instrumentation and methods are sensitive enough to detect and measure contaminants in hydrogen fuel at the levels specified by the ISO standard (Reference [1] footnote 5).

Table 3.4 Analytical sampling and measurement of contaminants at hydrogen fueling stations.

Impurities

Analytical methods

a)