Energy Storage Devices for Electronic Systems

Rechargeable Batteries and Supercapacitors

Nihal Kularatna

• Publisher: Academic Press
• Year: 2014
• eBook ISBN: 9780124081192
• Topic: Physical Sciences
• Subtopic: Energy

Energy storage devices are a crucial area of research and development across many engineering disciplines and industries. While batteries provide the significant advantage of high energy density, their limited life cycles, disposal challenges and charge and discharge management constraints undercut their effectiveness in certain applications. Compared to electrochemical cells, supercapacitors are charge-storage devices with much longer life cycles, yet they have traditionally been hobbled by limited DC voltage capabilities and energy density. However, recent advances are improving these issues.This book provides the opportunity to expand your knowledge of innovative supercapacitor applications, comparing them to other commonly used energy storage devices. It will strengthen your understanding of energy storage from a practical, applications-based point-of-view, without requiring detailed examination of underlying electrochemical equations. No matter what your field, you will find inspiration and guidance in the cutting-edge advances in energy storage devices in this book.- Provides explanations of the latest energy storage devices in a practical applications-based context- Includes examples of circuit designs that optimize the use of supercapacitors, and pathways to improve existing designs by effectively managing energy storage devices crucial to both low and high power applications.- Covers batteries, BMS (battery management systems) and cutting-edge advances in supercapacitors, providing a unique compare and contrast examination demonstrating applications where each technology can offer unique benefits

1

Energy storage devices—a general overview

Abstract

This chapter provides a quick and essential revision on simple fundamentals applicable to energy storage devices (ESDs). Device equivalent circuits, time constants, and requirements for maximum power transfer are discussed with an introduction to Ragone plots. Different types of ESDs are introduced in relation to state of the art.

Keywords

Fundamentals

Electrochemical storage devices

Supercapacitors

Energy density

Power density

Ragone plot

1.1 Introduction

From the invention of the transistor in late 1940s, electronic products and systems have become an essential part of the modern world with interconnected global communication systems, intelligent white goods, electronic subsystem dominated automotive and a plethora of portable devices. With the world population growing beyond 7 billion in 2012, and with the portable electronic devices getting popular even in the poorest parts of the world, worldwide energy consumption keeps growing at a steady rate. In 2008, world’s energy consumption was estimated to be around 144,000 TWh. Energy supply usually comes from several dominant sources, namely, fossil fuel and nuclear (as nondominant major sources), and from many renewable sources such as hydroelectric, solar, wind, geothermal, biomass, and biofuels.

In the world of energy usage, energy storage requirement comes in different forms. In our home and work environments, sometimes we need to store energy in systems such as the uninterruptible power supplies (UPSs) used for information systems and other critical facilities such as hospitals, airports, and factories in order to safeguard against power outages. In these situations, different types of energy storage systems (ESS) such as batteries, supercapacitor (SC) banks, flywheels, and compressed air are used together with suitable electromechanical energy conversion systems. In these systems, we usually deal with few 100 W to few megawatts order requirements with the outages expected in the range of fractional seconds to few hours.

In our modern hybrid electric vehicles (HEV) and electric vehicles (EV), battery banks and fuel cells are used to deal with kilowatt order requirements lasting for few minutes to few hours of driving, where the ESS comes into play. With the inefficiencies of internal combustion engine together with mechanical drive systems in the cars, overall energy efficiency is in the range of 15% to over 20%, encouraging the development of more energy efficient HEVs and EVs. In these applications, where tens of kilowatts of power is required, the capacity of the battery banks in terms of energy storage should be in the range of kilowatt-hours.

Compared to the above scenario, if we consider our portable electronic devices such as cell phones, PDAs, and laptops where battery packs are used, we commonly come across the capacity in terms of milliampere-hours (mAh) or ampere-hours (Ah), with battery packs with nominal voltage values varying from about 2.5 to about 16 V. Given these nominal voltage values, assumed to be constant over the operational range, will give us the energy storage capacity in mWh to Wh. Compared to the two above application areas, if we take much smaller power and energy requirements such as wrist watches, hearing aids and implants, the battery pack capacity may be specified in microwatt-hours to few milliwatt-hours only. Terminal voltages of these battery packs, mostly coming in the form of one or few single cells, may be in the range of 0.5 V to few Volts per cell.

Given a few common day-to-day examples of battery-based systems, we could practically appreciate that a few commonly identified electrical parameters such as terminal voltage, and the energy storage capacity in terms of Watt-hours or milliwatt-hours allow us to compare the capabilities of the battery packs. If a load consumes power at a steady rate of 1 W for 1 h, the device has consumed a total energy of 1 Wh during that period. In standard SI units, this translates to a value of 3600 J, since 1 W dissipated during 1 s is equal to 1 J.

So far we have considered only batteries as an energy storage device (ESD) family, but in general many different methods and devices can be used for energy storage suitable for electrical and electronic systems. This chapter provides an overview of energy storage and delivery devices, methods, and the essential fundamentals applicable to energy transfer into electronic systems and devices. With some quantification approach, the contents will assist comparing the details of energy storage capabilities, and ...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Dedication
• Preface
• Acknowledgments
• 1. Energy storage devices—a general overview
• 2. Rechargeable battery technologies: an electronic engineer’s view point
• 3. Dynamics, models, and management of rechargeable batteries
• 4. Capacitors as energy storage devices—simple basics to current commercial families
• 5. Electrical double-layer capacitors: fundamentals, characteristics, and equivalent circuits
• 6. Supercapacitor as a lossless dropper in DC-DC converters
• 7. Supercapacitors for surge absorption
• 8. Supercapacitors in a rapid heat transfer application
• Appendix A: capacitors and AC line filtering
• Index