Renewable Energy

A First Course

Robert Ehrlich, Harold A. Geller, John R. Cressman

• Editore: CRC Press
• Anno: 2022
• ISBN:
  9781000606348
• Edizione: 3
• Argomento: Physical Sciences
• Categoria: Energy

This revised edition of Renewable Energy: A First Course is fully updated and continues to provide the best in-depth introduction to renewable energy science. The book focuses mainly on renewable energy, but also addresses nonrenewable energy (fossil fuels and nuclear technology). The coverage extends from the basic physics to conservation, economic, and public policy issues, with strong emphasis on explaining how things work in practice. The authors avoid technical jargon and advanced math but address fundamental analytical skills with wide application. Updated statistics, figures, policies, trends, and technological advancements will bring the reader up to speed with the current state of renewable energy.

Chapter 1 Introduction

DOI: 10.1201/9781003172673-1

Contents

• 1.1 Why Another Book on Energy?
• 1.2 Why Is Energy So Important to Society?
• 1.3 Exactly What Is Energy?
• 1.4 Might There Be Some New Forms of Energy Not Yet Known?
• 1.5 What Are the Units of Energy?
• 1.6 Laws of Thermodynamics
• 1.7 What Is an Energy Source?
• 1.8 What Exactly Is the World’s Energy Problem?
• 1.9 How Is Green or Renewable Energy Defined?
• 1.10 Why Has Renewable Energy and Conservation Been Neglected Until Fairly Recently?
• 1.11 Does Energy Efficiency Really Matter?
• 1.12 Which Renewable Energy Sources Hold the Greatest Promise?
• 1.13 Who Are the World Leaders in Renewable Energy?
• 1.14 What Is Our Likely Energy Future?
• 1.15 Complexities in Charting the Best Course for the Future
• 1.16 Summary
• Problems
• References

1.1 Why Another Book on Energy?

The idea for this book arose as a result of one of the author’s first time teaching a course on renewable energy. The course was not Energy 101, but it was intended for students who had completed an introductory physics sequence and taken a few courses in calculus. Most available books were either too elementary or too advanced, and the handful of books at the right level seemed too focused on technicalities that obscured the basic ideas. In addition, many of those texts lacked the desired informal writing style, with even some occasional touches of humor that can enhance readability. Moreover, any course focused on renewable energy must also cover nonrenewable energy (fossil fuels and nuclear, specifically), because only then could useful contrasts be drawn. Renewable energy is a multidisciplinary subject that goes well beyond physics, although it is fair to say that this book has a physics orientation. Physicists do have a certain way of looking at the world that is different from other scientists and from engineers. They want to understand how things work and strip things down to their fundamentals. It is no accident that many new technologies, from the laser, to the computed tomography scanner, to the atomic bomb, were invented and developed by physicists, while their refinement is often done by engineers.

1.2 Why Is Energy So Important to Society?

Those of us who are fortunate to live in the developed world often take for granted the availability of abundant sources of energy, and we do not fully appreciate the difficult life faced by half of the population of the world, who substitute their own labor or that of domestic animals for the machines and devices that are so common in the developed world. A brief taste of what life is like without access to abundant energy sources is provided at those times when the power goes out. But while survival during such brief interludes may not be in question (except in special circumstances), try to imagine what life would be like if the power were to go out for a period of, say, 6 months. Not having cell phones, television, Internet, or radio might be the least of your problems, especially if the extended power failure occurred during a cold winter when food was not available, and your “taking up farming” was a complete joke, even if you had the knowledge, tools, and land to do so. As much as some of us might imagine the pleasures of a simple preindustrial lifestyle without all the trappings of our high-technology society, the reality would likely be quite different if we were suddenly plunged into a world without electricity. It is likely that a large fraction of the population would not survive 6 months. The idea of a prolonged failure of the power grid in many nations simultaneously is not just some outlandish science fiction prospect and could occur as a result of a large solar flare directed at the planet. The last one that was large enough to pose a threat of catastrophic damage was apparently the Carrington event, which occurred in 1859 before our electrified civilization existed, but it did cause telegraph systems all over North America and Europe to fail. Or severe disruptions may be caused by more down-to-earth weather-related phenomena like the ice storm in February 2021 that affected a large swath of the United States from Mexico to Canada. That storm caused significant blackouts in the independent Texas Interconnection power grid for several days, in sub-zero temperatures, resulting in over 150 deaths. Perhaps the most likely cause of a wide scale power disruption would occur due to human action, either accidental, like the clogging of the Suez Canal for 6 days in April 2021, or malicious, like the cyberattack that forced the Colonial Pipeline to go offline for 6 days in May 2021. Furthermore, the prospect of competing in a global market for limited resources has become increasing difficult with the further ascension of China, dysfunctional US leadership, and a world still reeling from a pandemic.

1.3 Exactly What Is Energy?

In elementary school, many of us learned that “energy is the ability to do work” and that “it cannot be created or destroyed” (conservation of energy). But these memorized and parroted phrases are not always easy to apply to real situations. For example, suppose you had a hand-cranked or pedal-driven electric generator that was connected to a light bulb. Do you think it would be just as hard to turn the generator if the light bulb were unscrewed from its socket or replaced by one of lower wattage? Most people (even some engineering students) who were asked this question answer yes and are often surprised to find on doing the experiment that the answer is no—the generator is easier to turn with the bulb removed or replaced by one of lower wattage. This of course must be the case by conservation of energy, since it is the mechanical energy of your turning the crank that is being converted into electrical energy, which is absent when the light bulb is unscrewed. Were the handle on the generator just as easy to turn regardless of whether a bulb is being lit or how brightly it glows, then it would be just as easy for a generator to supply electric power to a city of a million people as one having only a thousand! Incidentally, you can probably forget about supplying all your own power by using a pedal-powered generator, since even an avid cyclist would be able to supply at most only a few percent of what the average American consumes.

Aside from misunderstanding what the law of energy conservation implies about specific situations, there are also some interesting and subtle complexities to the law itself. Richard Feynman was one of the great physicists of the twentieth century who made many important discoveries, including the field of quantum electrodynamics, which he coinvented with Julian Schwinger. Feynman was both a very colorful person and a gifted teacher, who came up with novel ways to look at the world. He understood that the concept of energy and its conservation was more complex and abstract than many other physical quantities such as electric charge where the conservation law involves a single number—the net amount of charge. With energy, however, we have the problem that it comes in a wide variety of forms, including kinetic, potential, heat, light, electrical, magnetic, and nuclear, which can be converted into one another. To keep track of the net amount of energy and to recognize that it is conserved involve some more complicated “bookkeeping,” for example, knowing how many units of heat energy (calories) are equivalent to how many units of mechanical energy (joules).

How Many Joules Is Equal to 1 Calorie?

The calorie is the amount of heat needed to raise 1 g of water by 1°C. But since this amount slightly depends on temperature, one sometimes sees slightly different values quoted for the conversion factor commonly taken to be 4.1868 J/cal.

In presenting the concept of energy and the law of its conservation, Feynman made up a story of a little boy playing with 28 indestructible blocks (Feynman, 1985). Each day, the boy’s mother returns home and sees that there are in fact 28 blocks, until one day, she notices that only 27 are present. The observant mother notices one block lying in the backyard and realizes that her son must have thrown it out the window. Clearly, the number of blocks (like energy) is “conserved” only in a closed system, in which no blocks or energy enters or leaves. In the future, she is more careful not to leave the window open. Another day when the mother returns, she finds that only 25 blocks are present, and she concludes that the missing three blocks must be hidden somewhere—but where?

The boy seeking to make his mother’s task harder does not allow her to open a box in which blocks might be hidden. However, the clever mother finds that when she weighs the box, it is heavier than it was when empty by exactly three times the weight of one block, and she draws the obvious conclusion. The game between the mother and the child continues day after day, with the child finding more ingenious places to hide the blocks. One day, for example, he hides several under the dirty water in the sink, but the mother notices that the level of the water has risen by an amount equivalent to the volume of two blocks. Notice that the mother never sees any hidden blocks, but can infer how many are hidden in different places by making careful observations, and now that the windows are closed, she always finds the total number to be conserved. If the mother is so inclined, she might write her finding in terms of the equation for the “conservation of blocks”:

$\begin{array}{c}\text{Number}\text{of}\text{visible}\text{blocks}+\text{number}\text{hidden}\text{in}\text{box}\\ +\text{number}\text{hidden}\text{in}\text{sink}+\cdots =\text{28,}\end{array}$

where each of the numbers of hidden blocks had to be inferred from careful measurements, and the three dots suggest any number of other possible hiding places.

Energy conservation is similar to the story with the blocks in that when you take into account all the forms of energy (all the block hiding places), the total amount works out to be a constant. But remember that in order to conclude that the number of blocks was conserved, the mother needed to know exactly how much excess weight in the box, how much rise in dishwater level, etc., corresponded to one block. Exactly the same applies to energy conservation. If we want ...