Fall 2003


Energy - a Basic Physics Concept and a Social Value

John L. Roeder

Thirty years ago I began teaching at The Calhoun School in New York City. Soon after I arrived, the Arab Oil Embargo meant that the availability of gasoline at the corner service station could no longer be taken for granted, and before year's end I would pay in excess of a dollar for a gallon of it for the first time. The term "energy crisis" entered our vocabulary, and at Calhoun we decided to start a seminar about it.

That seminar later led to more organized and systematic teaching about energy, first in a course on "Critical Social Issues" and later in a physical science course called "Energy for the Future." I got involved with the educational work of the National Energy Foundation, then headquartered in New York City, spent two summers working on NSTA's "Project for an Energy Enriched Curriculum," and became a Resource Agent for the New York Energy Education Project.

Although my energy-focused physical science course gave way to Conceptual Physics and later Active Physics, after Paul Hewitt convinced me in 1989 that physics could and should be taught to ninth graders, only last year did I return to my earlier "life" as an energy educator and develop an Active Physics-formatted chapter on energy issues, in which the challenge was the same as the final exam of my former course: for students to plan their energy future without fossil fuels.1

It is the Second Law of Thermodynamics that makes energy an important concept in society. If we had only the First Law to worry about, we wouldn't have to worry: energy might not be created, but it isn't destroyed either. All the energy in the world today would continue to be available to us.

But for energy to meet our needs, it must be transformed -- e.g., we need to increase the thermal energy in our homes in winter, and we need a lot of energy brought to our appliances by electrons in electric current if they are to operate. The Second Law of Thermodynamics tells us that when energy is transformed, some of it gets transformed to a form that is less useful (the most typical example of this is “waste heat”). Energy “sources” are more useful forms of energy that can be transformed to meet our needs. When we “produce” energy, what we are really doing is to transform useful energy from these energy "sources" to a form that meets our needs. When we “use” these energy “sources,” energy in a form that met our needs is transformed to a less useful form. When we “conserve” energy, we “use” the smallest amount of an energy “source” to accomplish a particular task.

An important plan for any energy future is to “conserve” as much as we can, but “conserve” as much as it might, an industrial society still needs to “use” new “sources” of energy – to heat and cool its buildings, to run its appliances, to move its people, and to manufacture its goods. Because of their convenience, the "sources" of choice for more than a hundred years have been fossil fuels, the fuels I ask my students to plan their future without.

Why? Not just because a shortage of fossil fuels got us into trouble in 1973 – and again in 1979. Not just because burning fossil fuels produces carbon dioxide which leads to global warming. More fundamentally, we're eventually going to run out of them. Their continued use to support an ever-increasing population is not "sustainable" -- in the sense that our use of them denies future generations the benefits of their use (and as a manufacturing material as well as an energy "source").

Twenty years after the 1973 Arab Oil Embargo I took a retrospective look at what our actions showed we had learned from it. I learned that US total energy "use" had declined the years immediately following the energy crises of 1973 and 1979, that US energy use through 1990 had fallen below a host of predictions, but that most of the reduction was due to the industrial sector. But little had been done to wean us from our diet of fossil fuels.

The Solar Energy Research Institute was charged at its founding in 1977 to meet 20% of US energy needs from renewable sources by 2000. It was renamed the National Renewable Energy Laboratory (NREL) in 1991. I thought that this 30-year anniversary of the Arab Oil Embargo might be a good time to find out whether this goal had been met.

Data for US fossil fuel and total energy use are plotted on Figures 1 and 3. Both graphs show a decline following the energy crisis years of 1973 and 1979 and that both fossil fuel and total energy use had climbed back to their peak 1979 values a decade later and continue to climb. But, while fossil fuel use doubled from 1949 to 1968, it has not increased even 50% more than the 1968 usage since then. And not until 2000 did petroleum use climb back to its 1979 peak.

But the fact that we have put the brakes on increasing our petroleum use more than for other fossil fuels since the energy crises of the 1970s is no overt cause for rejoicing. For while imports still comprise only a small fraction of the coal (1.5%) and natural gas (20%) that we use, the fraction of petroleum imported passed 50% in 1990. M. King Hubbert, whose ability to forecast future fossil fuel production in terms of past data was legendary, wrote in the September 1971 Scientific American2 that "In the case of oil the period of peak production appears to be the present," and he was right.

We've decreased the rate at which our use of energy in general and fossil fuels in particular has increased, but these uses are still increasing. Moreover, the time since the energy crises of the 1970s have seen a decline of US production of petroleum and continually increasing imports.

How're we doing on renewables? Did NREL achieve the goal of 20% of US energy from renewable sources by 2000? Fig. 2 plots energy from conventional hydroelectricity, biomass, geothermal, and solar, and only since 1988 has solar gotten up off the t-axis on the graph. Most of our renewable energy continues to come from the two sources that have played the leading role even before renewable energy was fashionable: hydroelectricity and biomass. Geothermal has also started to make a more significant contribution since the energy crisis years, although it, too, had been around for a long time (see Fall 2002 issue). The total US energy use in Fig. 3 shows an increasing gap between total energy use and fossil fuel use. Although no new nuclear reactors have been erected since Three Mile Island in 1979, nuclear electricity continues to play an increasing role, and this has increased to be just a little greater than renewables.

In 1979 the Ford Foundation-sponsored study, Energy: The Next Twenty Years, opened with the following statement:

More than half a decade has passed since the oil crisis of 1973-1974 signaled a new era in U.S. and world history. The effort to develop a satisfactory policy response to what was once characterized as the "moral equivalent of war" has stretched out so long that weariness rather than vigor characterizes the national debate. . . . energy and environmental objectives seem irreconcilable; . . . a national consensus that solar energy is a good thing has yet to result in significant resource commitments, while support for nuclear energy, yesterday's hope for tomorrow, is eroding; and coal is marking time. Meanwhile, the slow, steady increase in the number of barrels of oil imported . . . provide[s] reminders that much needs to be done.3

I don't think it would stretch the imagination to replace "more than half a decade" in this statement with "three decades." In that time we have not learned the lessons of the energy crises, nor have we met the well-intentioned goal of 20% of our energy from renewable sources by 2000. In fact, at the World Summit on Sustainable Development in Johannesburg last year the leaders of the world could not agree to increase the percentage of the world's energy use from renewables to 15% by 2010. Last fall when I presented my ninth graders the challenge of the new Active Physics-formatted chapter I wrote on energy issues, I told them that I was asking them to do what the leaders of the world were unwilling to commit to: plan their energy future without fossil fuels.

In the year 2010 those ninth graders will be graduating from college and begin to take their place in the world. If the leaders of the world, more preoccupied with the politics of the present when they should be framing a forward-looking vision of the future, haven't figured out how to produce 15% of the world's energy by renewable means by then, I hope that the next generation will be better trained to deal with this problem.


1. John L. Roeder, "Active Physics Chapters on Energy," AAPT Announcer, 32(2), 95 (Summer 2002)

2. M. King Hubbert, "The Energy Resources of the Earth," in Energy and Power (Freeman, San Francisco, 1971)

3. Hans H. Landsberg, et al., Energy: The Next Twenty Years (Ballinger, Cambridge, MA, 1979)

(Note: The preceding article was excerpted from the author's talk of the same title at the American Association of Physics Teachers meeting in Madison, WI, 4 Aug 2003.)

Figure 1

Figure 2

by John L. Roeder

The Calhoun School

New York, NY 10024