Electrochemical Components E-Book

Marie-Cécile Pera

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 436

Veröffentlichungsjahr: 2013

Beschreibung

This book focuses on the methods of storage commonly used in hybrid systems.

After an introductory chapter reviewing the basics of electrochemistry, Chapter 2 is given over to the storage of electricity in the form of hydrogen. Once hydrogen has been made, we have to be able to convert it back into electricity on demand. This can be done with another energy converter: a fuel cell, the subject of Chapter 3. Such a system is unable to deliver significant dynamics in terms of storage and release of electricity and needs to be supplemented with another solution: a detailed study of supercapacitors is provided in Chapter 4.While the storage systems touched upon in the previous three chapters (hydrogen batteries and supercapacitors) both exhibit advantageous characteristics, at present they are still relatively costly. Thus, the days of the electrochemical accumulator by no means appear to be numbered just yet. This will therefore be the topic of Chapter 5. Finally, on the basis of the elements laid down in the previous chapters, Chapter 6 will focus on electrical hybridization of these storage systems, with a view to enhancing the performance (in terms of energy, lifetime, cost, etc.) of the newly formed system.

Aimed at an audience of researchers, industrialists, academics, teachers and students, many exercises, along with corrected solutions, are provided throughout the book.

Leseprobe

Table of Contents

Preface

Chapter 1. Basic Concepts of Electrochemistry used in Electrical Engineering

1.1. Introduction

1.2. Brief description and principles of operation of electrochemical components

1.3. Redox reaction

1.4. Chemical energy

1.5. Potential or voltage of an electrode

1.6. Reversible potential of a cell

1.7. Faradaic current density and the Butler–Volmer equation

1.8. Butler–Volmer equation for a whole cell

1.9. From the Butler–Volmer equation to the Tafel equation

1.10. Faraday’s law

1.11. Matter transfer model: Nernst model

1.12. Concept of limit current

1.13. Expression of the polarization curve

1.14. Double-layer capacity

1.15. Electrochemical impedance

1.16. Reagents and products in the gaseous phase: total pressure, partial pressure, molar fraction and mixture

1.17. Corrected exercises

Chapter 2. Water Electrolyzers

2.1. Introduction

2.2. Principles of operation of the main water electrolyzers

2.3. History of water electrolysis

2.4. Technological elements

2.5. Theoretical approach to an electrolyzer

2.6. Experimental characterization of the electrical behavior of an electrolyzer

2.7. Procedures for parameterizing the models

2.8. Combination with a fuel cell. Concept of the “hydrogen battery”

2.9. A few examples of applications for electrolyzers

2.10. Some points about the storage of hydrogen

2.11. Conclusions and perspectives

2.12. Exercises

Chapter 3. Fuel Cells

3.1. Introduction

3.2. Classification of fuel cell technologies

3.3. Proton Exchange Membrane Fuel Cells (PEMFCs)

3.4. Solid Oxide Fuel Cells (SOFCs)

3.5. Fuel-cell systems

3.6. Applications for fuel cells

3.7. Corrected exercises

Chapter 4. Electrical Energy Storage by Supercapacitors

4.1. Introduction

4.2. Operation and energy characteristics of EDLCs

4.3. Supercapacitor module sizing

4.4. Supercapacitor modeling

4.5. DC/DC converter associated with a supercapacitor module

4.6. Thermal behavior of supercapacitors

4.7. Hybrid electricity storage device: the LIC (Lithium Ion Capacitor)

4.8. Exercises – statements

Chapter 5. Electrochemical Accumulators

5.1. Introduction

5.2. Lead accumulators

5.3. Nickel accumulators

5.4. Lithium accumulators

5.5. Characteristics of an accumulator or battery

5.6. Modeling of a battery

5.7. Aging of batteries

5.8. Exercises

Chapter 6. Hybrid Electrical System

6.1. Introduction

6.2. Definitions

6.3. Advantages to hybridization

6.4. Management of the energy flows in a hybrid system

6.5. Example of application in the domain of transport: the ECCE platform (Evaluation des Composants d’une Chaine de traction Electrique – Evaluation of the Components in an Electric Powertrain)

6.6. Corrected exercises

Bibliography

Index

First published 2013 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc.

Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address:

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© ISTE Ltd2013

The rights of Marie-Cécile Péra, Daniel Hissel, Hamid Gualous and Christophe Turpin to be identified as the authors of this work have been asserted bythem in accordance with the Copyright, Designs and Patents Act 1988.

Library of Congress Control Number: 2013941766

British Library Cataloguing-in-Publication Data

A CIP record for this book is available from the British Library

ISBN: 978-1-84821-401-9

Preface

“You can’t store electricity! …”

Many of us have heard this phrase before, or indeed hear it regularly said still. At present, when there is a great deal of debate and reflection about the necessity of making a switch in our energy provision, this phrase is often even used as an excuse for the holders of one vision or another of that transition. Indeed, if electricity cannot be stored, we must at all times be able to balance supply and demand, and therefore we need to be able, to control either supply … or demand – or indeed both – in a highly dynamic way.

Yet this phrase is not entirely true. In fact, everyone knows this. On a daily basis, we all use objects, tools or mobile systems using an electrical supply (mobile telephones, laptop computers, portable electric tools, electrical vehicles, etc.). Thus, de facto, we know that electricity can be stored. Nevertheless, it is relatively difficult to store it, more difficult to store it over long periods of time, and more difficult still to store it in extreme environmental conditions.

Nevertheless, almost paradoxically, there are many technological solutions that can be envisaged in terms of electricity storage. In particular, we can cite electrochemical or electrostatic storage means (electrochemical accumulators, supercapacitors, etc.), but also magnetic means of energy storage (such as superconductors) or mechanical ones (such as flywheels). We can even envisage storing electricity by means of another energy vector, such as hydrogen. The purpose of this book is not to give an overview of all these means for the storage of electricity; rather, our aim here is to devote our attention to those methods of storage which are commonly used in hybrid systems, whether intended for stationary applications or use in transport.

Thus, after an introductory chapter – which cannot, however, be viewed as a complete ab initio introduction to the subject – reviewing the basics of electrochemistry, Chapter 2 is given over to the storage of electricity in the form of hydrogen. While technological prototypes using this method are, as yet, limited, they should, in the future, come to play an increasingly significant role in storage for electrical grids or for supply of isolated sites. Electricity can be transformed into hydrogen by electrolysis of water. This is the technology which will be outlined and analyzed in Chapter 2.

Once hydrogen has been made by electrolysis and stored in ad hoc tanks, we have to be able to convert it back into electricity on demand. This can be done with another energy converter: a fuel cell. The description and usage of this technology will therefore be the subject of Chapter 3. Note that the complete combination of an electrolyzer, hydrogen storage facility and fuel cell can be viewed as what is known as a “hydrogen battery”.

Such a system is unable to deliver significant dynamics in terms of storage and release of electricity. In hybrid systems, the time-delay is often prohibitive. Hence, we need to be able to supplement this solution with another, which is capable of dealing with the time requirements to meet storage/release of power needs. A supercapacitor is perfect for this role. Hence, a detailed study of supercapacitors is provided in Chapter 4.

While the storage systems touched upon in these three chapters (hydrogen batteries and supercapacitors) both exhibit potentially advantageous characteristics, which vindicate their usage in hybrid electrical systems, at present they are still relatively costly. In fact, the days of the electrochemical accumulator by no means appear to be numbered just yet. This will therefore be the topic of Chapter 5.

Finally, on the basis of the elements laid down in the previous chapters, Chapter 6 will focus on electrical hybridization of these storage systems, with a view to enhancing the performances (in terms of energy, lifetime, cost, etc.) of the new system thus formed.

Before getting to the heart of the matter, it is also useful to mention that the primary goal of this book is for use in teaching. It is intended for an audience of researchers, industrialists, academics, teachers, students, school students, etc., who are anxious to be informed, to gather information and to acquire the basic knowledge of physics and technology that will enable them to comprehend and appreciate these systems. Many exercises, along with corrected solutions, will therefore be provided to the reader throughout this manuscript. In addition, a carefully-considered list of pertinent bibliographical references is provided at the end of the book. We invite interested readers who wish to look more closely at the concepts evoked from a pedagogical angle in this book to refer to these other works.

Chapter 1

Basic Concepts of Electrochemistry used in Electrical Engineering

1.1. Introduction

The aim of this chapter is to lay down some basic concepts of electrochemistry which are necessary in order to understand the behavior of the electrochemical components described in this book. For a detailed presentation, the reader could be helped by referring to specialized books such as [DIA 96; LEF 09].

1.2. Brief description and principles of operation of electrochemical components

1.2.1. Principle of operation [TUR 08]

Every electrochemical component is made up of a positive electrode and a negative electrode, separated by an electrolyte which may be either liquid or solid (see Figure 1.1). Conventionally, with generators, it is the positive electrode from which the current originates when functioning in generator mode.

Generally speaking, an electrochemical component can operate as an electric generator or an electric load, or both if it has reversible function.

Figure 1.1. Principle of operation of electrochemical components [TUR 08]

In short, the component is the site of an oxidation/reduction reaction which involves two “redox” pairs. More specifically, each electrode is the site of oxidation (loss of electrons) or reduction (gain of electrons) depending on the direction of the current flowing through the component (Figure 1.1e). The n electrons released by the oxidation reaction occurring in an electrode circulate from that electrode to the other via the external electrical circuit. Simultaneously to this circulation of electrons, and in the same direction, the n ions from the electrode being oxidized circulate toward the other electrode through the electrolyte. Thus, the reduction reaction is able to take place on the other electrode.

The electrodes need to be good electrical conductors. The electrolyte has to be a good ion conductor and a good electron insulator, in order to avoid any short-circuits between the two electrodes. In the case of a liquid electrolyte, a separator is usually used to electrically insulate the two electrodes. The reactions consume reactants and form products, which have to be respectively brought to and evacuated from the reaction area.

In addition, in any electrochemical component, at every interface between an electrode and the electrolyte, there is a spontaneous phenomenon of accumulation of opposite charges on both sides of that interface, which then constitutes a condenser, in the electrostatic sense of the term (Figure 1.2a). This phenomenon is referred to as a “double electrochemical layer”. As local electrical polarization occurs over a depth ranging from a few dozen to a few hundred nanometers around that interface, the equivalent condensers may have very large values if the electrodes have a very large surface per volume (they are therefore dubbed supercapacitors). This phenomenon plays an important role in the dynamic behavior of the component.

Finally, the phenomena described above are accompanied by heat exchanges; the performances and lifetimes of the components are very sensitive to temperature. Hence, thermal aspects are of crucial importance for their implementation in electrical systems.

1.2.2. Brief description of groups of components

There is a wide variety of electrochemical components for the production and storage of electricity [TUR 08], some of which will be the subject of a more in-depth description later on in this book. Amongst other things, it is possible to distinguish the following “families” of electrochemical components: