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.

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.

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.