1
Energy Fundamentals, Energy Use in an Industrial Society

1.1 Introduction

Energy enters our everyday lives in many different ways. The energy in the food we eat maintains our body temperature and lets us walk, talk, lift things, and toss Frisbees. The use of energy in food has been essential for the existence of all humankind and animals throughout our evolution on this planet. In some developing countries, the supplying of food for energy and nutrition is a difficult task that requires most of the waking hours of the population. Food acquisition is just as essential in the more developed countries, but because of the greater mechanization of agricultural production, the effort of only a relatively small number of persons is devoted to obtaining food. This leaves most of the rest of us free to pursue other activities throughout our lives.

Energy in forms other than food is also essential for the functioning of a technical society. For example, in the United States, many times more energy in the form of engine fuel goes into the agricultural enterprise than is obtained in the useful food Calorie content of the food produced. Prodigious amounts of energy are also used to power automobiles, heat homes, manufacture products, generate electricity, and perform various other tasks. In order for our society to function in its present patterns, vast amounts of coal, natural gas, and oil are extracted from the earth and burned to provide this energy. To a lesser extent, we also derive energy from hydroelectric plants, nuclear reactors, electric wind generators, and geothermal plants, and, of course, we all benefit enormously from the energy obtained directly from the sun.

The fossil fuels, coal, natural gas, and oil, supply about 81% of the energy used in the United States. These resources evolved hundreds of millions of years ago as plant and animal matter decomposed and was converted under conditions of high temperature and pressure under the earth's surface into the hydrocarbon compounds that we now call fossil fuels. Since the beginning of the machine age, industrial societies have become increasingly dependent on fossil fuels. A 150 years ago, the muscular effort of humans and animals played an important role in the American economy, and firewood supplied most of the heat energy. Now only a small fraction of our energy comes from firewood, and we rely much less on the physical effort of people and animals. The process by which we have moved to our present dependence on coal, oil, and natural gas is illustrated in Figure 1.1, where the energy consumed in the United States each year from various sources is shown in terms of quadrillion British thermal units (QBtu) for the years 1850 to 2019. The definition of QBtu will be given in Section 1.6.

Figure 1.1 Various forms of energy consumed in the United States since 1850. This type of graph is called a semilogarithmic plot, an explanation of the scales is given in the Appendix.

Source: Historical Statistics of the United States, Colonial Times to 1970, U.S. Department of Commerce. Bureau of the Census, 1975; U.S. Energy Information Administration, Monthly Energy Review, October 2020. The wood data set from 1850 to 1950 is from the first source. The wood data set from 1950 to 2019 is from the second source; it includes wood, black liquor (a byproduct of the wood‐based paper production process), and wood waste.

Should we be concerned that so much of our energy is now coming from fossil fuels? Here are two of many factors that should cause concern.

First, the fossil fuel resource is limited in amount. The fossil fuels were produced by solar energy hundreds of millions of years ago, and when they are gone, there will be no more. It is true that the fuels are still being formed, but at an entirely negligible rate compared to the rate at which we are consuming them. We first began consuming the fossil fuels at an appreciable rate only about 150 years ago. How long will they last? On a global scale, total use of fossil fuels is still rising. In the United States, only the use of coal has significantly decreased in recent years. We will still have some coal for a few centuries, but at our present rate of use, natural gas and oil will be in short supply more quickly. While modern extraction techniques have increased the available global supply of these fuels, it is not enough to change the overall situation presented in Figure 1.2, which shows the narrow blip of our fossil fuel use set against a time scale of thousands of years. As you consider the brief duration of this blip, remember that we have living trees thousands of years old, a much longer time than what will be spanned by the entire era of fossil fuel consumption. It is clear from this figure that we live in an extraordinary time in the many billion year history of the earth. The entire stock of fossil fuels available for our use has been held in storage under the earth’s surface for more than a hundred million years, and now it is being completely exploited in only a few centuries.

Second, unintended environmental consequences result from the extensive scale of our use of the fossil fuels for everything from heating our homes to powering our automobiles. When we burn coal, natural gas, or oil to obtain energy, gaseous compounds are formed and dumped into the atmosphere. This is causing problems we are just beginning to face. For many years, it was felt that the emitted gases were not significant, given the vastness of the earth’s atmosphere. But now with increasing world population, and industrialization, this is no longer true. The atmospheric pollution is producing health problems and even death, and it is now becoming recognized that carbon dioxide emissions are producing climate changes over the entire globe.

Can we find solutions to these problems of resource depletion and environmental pollution? Clearly, the answers are not simple or the solutions would have been put into effect by now. The subject is complex and involves some understanding of topics such as patterns of resource depletion, the workings of heat engines, solar cells, wind generators, nuclear reactors, and a myriad of other specialized subjects. We do not have to become experts on each of these individual topics to be sufficiently well informed as voting citizens to influence a rational decision‐making process. Our goal is to gain understanding concerning the essential points.

Figure 1.2 The complete exploitation of the world's fossil fuels will span only a relatively brief time in the 10,000 year period shown centered around the present.

Source: Reprinted with permission from Hubbert, M.K. (1969). Resources and Man. Washington, DC: National Academy of Sciences. Historical events added.

1.2 Why Do We Use So Much Energy?

A partial answer to this question is simple—we do not use our energy resources as efficiently as we could. The standard of living we enjoy in the United States could be maintained with an expenditure of far less energy per person than at present. This side of solving the energy problem will be explored later under the heading of Energy Conservation. There is a large discrepancy between the rate of energy use by a typical citizen of an industrialized society and the typical citizen of a developing country, and it is accompanied by a notable difference in what we perceive as the standard of living. This is illustrated in Figure 1.3, where we see the per capita gross domestic product (GDP) and the per capita energy use for several countries of the world. Although not indicated on this figure, several developing countries have very low rankings by either measure, and they would be located within the small quarter‐circle shown at the extreme lower left corner of the figure.

Figure 1.3 The gross domestic product (GDP) per capita in US dollars is compared to the total energy consumed per capita in equivalent barrels of oil for several countries. The small quarter‐circle at the lower left corner is discussed in the text.

Source: United Nations Statistical Yearbook, 2020 Edition.

There is no essential relationship between GDP per capita and the standard of living, but both are often related to the use of energy. A citizen of a developing country might use the energy equivalent of less than one barrel of oil per year compared with an annual energy equivalent of 20 to 60 barrels per capita for the most industrialized countries. The nonindustrialized countries derive a large fraction of their necessary energy from the muscular effort of people and animals. There is an interesting quotation from an early physics textbook written by J. Dorman Steele in 1878:

The combustion of a single pound of coal, supposing it to take place in a minute, is equivalent to the work of three hundred horses; and the force set free in the burning of 300 pounds of coal is equivalent to the work of an able‐bodied man for a lifetime.

This observation, while a bit off the mark in exact technical detail, is essentially correct, and it sets the stage and justifies the enormous effort that has gone into our learning to exploit the fossil fuels—energy reserves held in waiting for hundreds of millions of years—until we have learned to use them with high efficiency to ease human labor. Whether we refer to tons of coal or barrels of oil, it is indeed the fossil fuels that have had the major effect. Without fossil fuels,...