The main purpose of this book is to present a different phenomenological approach to practical energy storage. Throughout the book, a main thread of the problems associated with the generation, transmission, conversion, and storage of energy is proposed, and various technologies are addressed primarily from a phenomenological viewpoint. The exploration of new processes is a major part of the continual search for improved means of the generation and storage of energy.

Although some mathematical developments are presented, this book is not intended as a text on thermodynamics or electrochemistry. Certainly, thermodynamics is employed and generous use is made of mathematical tools, but this is not a text directed toward the development or teaching of such principles. It is assumed that the reader possesses some knowledge of elementary classical physics and mathematics and differential calculus in order to easily understand some of the details of thermodynamics and diffusion processes upon which the mechanisms of concentration cell operations are based.

This book presents a broad review of energy technology only in summary fashion in order to provide a background so that the concentration cell approach will be viewed in context with other available means of energy storage. It is necessary to cover a reasonable portion of these subjects in order to make this narrative understandable as an alternative presentation. The rationale behind the concentration cell approach should become apparent as the reader moves through the arguments and reviews.

The primary aim is to suggest and describe an alternative approach to energy storage other than the ones that have been pursued in the past, especially so vigorously within the past thirty to forty years. The recognized need for improved and practical ways to store large quantities of energy for later use, such as in load leveling for the electric power utilities, has resulted in innumerable programs sponsored by the Atomic Energy Commission, the Energy Research and Development Administration, and the present Department of Energy.

However, many of the concepts regarding the processes at electrode surfaces evolved during the prolonged writing of this book, and the mathematics was developed subsequent to the experiments with laboratory cells described here. The work is hardly complete, and much still needs to be explained. Our astonishment was significant when we first observed the large voltages produced in symmetrical cells with electrodes of large micro-areas.

Hopefully, this book will engender interest in acquiring a basic understanding and stimulate further explorations into other, alternative methods of storing energy that may have been largely overlooked, such as the class of phenomena generally referred to in electrochemistry as “concentration cells.” There is much opportunity to store energy in an efficient and easily reversible fashion. Since this type of cell makes use of the colligative properties of substances, many different combinations of materials can be employed in such cells.

The first five parts are devoted to a general discussion of energy issues and the presentation of tutorial information.

The author gathered most of the data and operation and construction details during the various development projects undertaken in redox and concentration types of cell and battery development. Much of the technical information, performance data, and design parameters were obtained while the author was with the Westinghouse Electric Co. Research Center in Pittsburgh, the General Electric Co., the Research and Development Center in Schenectady, NY, and the Technology Research Laboratories, Inc. in Durham, NC.

The practical application aspects of a category of phenomena in physics and electrochemistry have been largely overlooked. That category is the source of electric potentials that can be produced from concentration differences of the same chemical ionic species opposite electrode surfaces.

The only practical answer to all-around energy storage needs may lie in the application of the class of phenomena referred to as electrochemical concentration cells. The electrical potential results from structured cells with intense differences in concentration of the same elemental (chemical) specie at two different oxidation states. Storage continues to be a main concern in the whole spectrum of energy related issues.

There is no question regarding the efficacy or scientific soundness of the principles employed for storing energy in this fashion. The approach is well beyond such serious concerns. The questions that remain are those regarding the ultimate practicality and competitiveness with respect to other methods of reversible energy storage in such matters as its ultimately achievable efficiency, cost, and energy density.

The information presented in this book is the result of forty years of search and experimental researching for a method of storing energy in a reversible, dependable, and life-long manner. Research has largely been centered on the electrochemistry of what has in recent years become known as redox systems. Both static and full flow electrolyte systems have been explored. The resultant system that satisfied most, if not all, of the imposed practical requirements and appeared to offer the least limited performance with future development was the concentration cell – a significant departure from the normal path of such studies.

This mechanism for storage is based upon Nernst’s equation for the chemical potential that can be derived from the ratio of concentrations of the same ionic substance at opposing electrodes in an electrochemical cell.

There are two further volumes planned in this series on energy storage, the first of which, tentatively titled, Concentration Cells: Fabrication Methods and Materials, is due to be published by Wiley-Scrivener in September 2011. The aim of this second volume will be to provide the engineer and scientist with the most comprehensive coverage of the concentration cell yet written, with a view toward employing the concentration cell in the storage of energy on a large scale.