Wind and Solar Power Systems

Design, Analysis, and Operation

Mukund R. Patel, Omid Beik

• Publisher: CRC Press
• Year: 2021
• Print ISBN: 9780367476939
• eBook ISBN: 9781000356960
• Edition: 3
• Topic: Technology & Engineering
• Subtopic: Environmental Management
• Index: Technology & Engineering

This book provides technological and socio-economic coverage of renewable energy. It discusses wind power technologies, solar photovoltaic technologies, large-scale energy storage technologies, and ancillary power systems. In this new edition, the book addresses advancements that have been made in renewable energy: grid-connected power plants, power electronics converters, and multi-phase conversion systems.

The text has been revised to include up-to-date material, statistics, and current technology trends. Three new chapters have been added to cover turbine generators, AC and DC wind systems, and recent advances solar power conversion.

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• Discusses additional renewable energy sources, such as ocean, special turbines, etc.

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• Covers system integration for solar and wind energy

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• Presents emerging DC wind systems

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• Includes coverage on turbine generators

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• Updated sections on solar power conversion

It offers students, practicing engineers, and researchers a comprehensive look at wind and solar power technologies. It is designed as a reference and can serve as a textbook for senior undergraduates in a one-semester course on renewable power or energy systems.

Part C

System Integration

13 Energy Storage

Electricity is more versatile in use than other types of power, because it is a highly ordered form of energy that can be converted efficiently into other forms. For example, it can be converted into mechanical form with efficiency approaching 100% or into heat with 100% efficiency. Heat energy, on the other hand, cannot be converted into electricity with such high efficiency, because it is a disordered form of energy in atoms. For this reason, the overall thermal-to-electrical conversion efficiency of a typical fossil thermal power plant is less than 50%.

A disadvantage of electricity is that it cannot be easily stored on a large scale. Almost all electric energy used today is consumed as it is generated. This poses no hardship in conventional power plants, in which fuel consumption is continuously varied with the load requirement. Wind and photovoltaics (PVs), both being intermittent sources of power, cannot meet the load demand at all times, 24 h a day, 365 d a year. Energy storage, therefore, is a desired feature to incorporate with such power systems, particularly in stand-alone plants. It can significantly improve the load availability, a key requirement for any power system.

The present and future energy storage technologies that may be considered for stand-alone wind or PV power systems fall into the following broad categories:

• Electrochemical battery
• Flywheel
• Compressed air
• Superconducting coil

13.1 Battery

The battery stores energy in an electrochemical form and is the most widely used device for energy storage in a variety of applications. The electrochemical energy is in a semi-ordered form, which is in between the electrical and thermal forms. It has a one-way conversion efficiency of 85 to 90%.

There are two basic types of electrochemical batteries:

The primary battery, which converts chemical energy into electric energy. The electrochemical reaction in a primary battery is nonreversible, and the battery is discarded after a full discharge. For this reason, it finds applications where a high energy density for one-time use is required.

The secondary battery, which is also known as the rechargeable battery. The electrochemical reaction in the secondary battery is reversible. After a discharge, it can be recharged by injecting a direct current from an external source. This type of battery converts chemical energy into electric energy in the discharge mode. In the charge mode, it converts the electric energy into chemical energy. In both modes, a small fraction of energy is converted into heat, which is dissipated to the surrounding medium. The round-trip conversion efficiency is between 70 and 80%.

The internal construction of a typical electrochemical cell is shown in Figure 13.1. It has positive and negative electrode plates with insulating separators and a chemical electrolyte in between. The two groups of electrode plates are connected to two external terminals mounted on the casing. The cell stores electrochemical energy at a low electrical potential, typically a few volts. The cell capacity, denoted by C, is measured in ampere-hours (Ah), meaning it can deliver C A for one hour or C/n A for n hours.

FIGURE 13.1 Electrochemical energy storage cell construction.

The battery is made of numerous electrochemical cells connected in a series–parallel combination to obtain the desired battery voltage and current. The higher the battery voltage, the higher the number of cells required in series. The battery rating is stated in terms of the average voltage during discharge and the ampere-hour capacity it can deliver before the voltage drops below the specified limit. The product of the voltage and ampere-hour forms the watthour (Wh) energy rating th...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Dedication
• Table of Contents
• Preface
• Acknowledgements
• Author Biographies
• List of Abbreviations and Conversion of Units
• Glossary
• Part A: Wind Power Systems
• Part B: Photovoltaic Power Systems
• Part C: System Integration
• Part D: Ancillary Power Technologies
• Index