Preface to first edition
Renewable energy is the collective name for a number of energy resources available to man on Earth. Their conversion has always played an important role for the inhabitants of the planet, and apart from a period of negligible length—relative to evolutionary and historical time scales—the renewable energy sources have been the only ones accessible to mankind.
Yet the study of renewable energy resources, their origin and conversion, may at present be characterized as an emerging science. During the past fifty years of scientific and technological revolution, much more effort has been devoted to the extraction and utilization of nonrenewable energy resources (fuels), than to the renewable ones. Only very recently have funds been made available to re-establish renewable energy research and development, and it is still unclear whether the technologies based on renewable energy sources will become able to constitute the backbone of future energy supply systems.
The purpose of the present book is to provide an incentive as well as a basis of reference for those working within the field of renewable energy. The discontinuity between earlier and present work on renewable energy, and the broadness of disciplines required for assessing many questions related to the use of renewable energy, have created a need for a comprehensive reference book, covering methods and principles, rather than specific engineering prescriptions of passing interest in a rapidly developing field.
A survey of renewable energy has to draw upon a large number of individual scientific disciplines, ranging from astrophysics and upper atmospheric science over meteorology and geology to thermodynamics, fluid mechanics, solid-state physics, etc. Specialists in each discipline often use a vocabulary recognized only by insiders, and they rarely emphasize the aspects pertinent to renewable energy. I have attempted to use a common language throughout, and to restrict the prerequisites for understanding to a fairly elementary level (e.g., basic physics). However, this does not mean that I have avoided any degree of complication considered relevant, and the reader must be prepared to face a number of challenges.
I envisage my reader as a research worker or student working somewhere within the field of renewable energy. Such work is currently undertaken at universities, engineering schools, and various offices and laboratories in the public or private sectors. However, since a substantial part of the book deals with energy systems comprising renewable energy elements, and with the management and economy of such systems, including environmental and social aspects, then I sincerely hope to attract also readers in the energy planning and management sectors, whether their concern is the physical planning and operation of energy supply systems or the socioeconomic assessment of such systems.
When used as a textbook, particular chapters may be more relevant than others. Cross-references are included in most cases where definitions or basic concepts have to be taken from a different chapter. Courses in engineering may place the emphasis around Chapter 4 (e.g., including Chapters 3–6), courses in “energy physics” or on energy in general may place more emphasis on Chapters 2 and 3, while courses on energy planning, systems aspects, and technological or economic assessments may find it natural to shift the emphasis to Chapters 6 and 7.
It should be stressed that the main purpose of the book is to provide general tools for treating problems relating to renewable energy. This is evident from the approach to energy conversion in Chapter 4 (stressing principles rather than describing individual pieces of equipment in detail), and from the treatment of supply systems in Chapter 6 (which contains no exhaustive reviews of possible system combinations, but illustrates basic modeling and simulation techniques by use of just a few, selected system examples). Energy storage and transmission (Chapter 5) are described in a highly condensed form, with the sole purpose of introducing the components for use in energy systems like those discussed in Chapter 6.
I have been motivated to engage in work on renewable energy and to see the possibility of an increasingly important role played by the associated technologies by reflections that are largely summarized in Chapter 1, and that to some extent lie behind those amendments to conventional economic theory for application to long-term energy planning, proposed in Chapter 7. The subjective nature of a number of interpretations made in these two chapters is recognized, and an effort has been made to ban such interpretations from the remaining five chapters, so that readers disagreeing with my interpretations may still find the bulk of the book useful and stimulating.
I thank the following for reading and commenting on portions of the draft version of the manuscript: Niels Balling, Henning Frost Christensen, E. Eliasen, Frede Hvelplund, Johannes Jensen, Marshal Merriam, B. Maribo Petersen, and Ole Ulfbeck.
Allerød, January 1979