Brian K. Sohn, Ph.D.
This diagram represents an estimate of U.S. energy consumption. Like most such diagrams, a little context goes a long way to helping understand them. First and foremost, charts like these are often presented as facts when they are really best guesses. Other organizations have different guesses. All that grey “rejected energy” on the upper right is the energy that is lost or wasted as a result of inefficiency.
Now when inefficiency is used in talking about joules or BTUs (or quads: 1 quad = 1 quadrillion BTUs), you have to keep in mind that we’re talking about inputs and outputs. When we talk of inputs and outputs, most of us need to step beyond the usual bounds of our thinking into the world of physics.
In my introductory physics courses in college, I first learned about the technical use of the term efficiency. We use it commonly in a positive way, but in physics it’s a calculation, not a value judgment. Energy out divided by energy in. That gives a fraction, we convert it to a percentage, and we have to compare relative efficiencies in order to gain any understanding of what is good and bad. For example, a typical gasoline engine is about 20% efficient. Incandescent lights are about 2%. Commercially available photovoltaic solar cells range from 14-19%. With those efficiencies in mind, you can look at the diagram above with more sense of our overall efficiency: around 32%.
100% efficiency is impossible via Newton’s second law: entropy increases over time. That is, even if an energy source is just sitting around, it’s decaying. Whenever we try to convert energy into something usable, some of it (usually a lot of it) is lost. Gas engines produce a lot of heat and noise as they push the pistons. Light bulbs give off heat as they shine. Solar cells…leak. I don’t know where the lost energy goes. Probably not noise, maybe heat.
Just as it is helpful to compare efficiencies of typical energy-consuming items like motors and light bulbs, it is informative to compare how energy use changes over time. Five years ago, we were using more coal and hydro. Every other source has grown in the last five years.
Over the very long haul, we are using more less efficient energy sources. In 1970, we used around 67.5 quads, but LLNL estimated our efficiency at closer to 50%. The article linked above will give you a lot of information in a short amount of time (it’s very efficient!)
Learning and Energy
Schools use a lot of energy but rarely teach about it. The lights are (usually) on. The rooms are (usually) somewhere between 65 and 80 degrees. At Belfry High School, where I used to work, they ran on geothermal, and even as the sponsor for the environmental club, I didn’t learn that until after I worked there for two years. We tend to only think about electricity when it is lost or when the power bill comes in. But learning about energy should be a major chunk of the curriculum, and not just in elementary school. Even many well-educated people fail to understand how we get it, where it comes from, and where it goes.
According to a professor I talked with, even the smarty-pants students that attend Virginia Tech struggle with the concept of the lifespan, “cradle to grave” of energy. Non-renewables must be discovered, transported, refined, burned, etc. Solar requires specialized materials for construction of cells (and the cells don’t last forever!). And then there are the byproducts. From carbon dioxide to sulfur to ash, production and consumption of energy doesn’t end at the point of use.
With knowledge and awareness of energy source lifespans, people can then grapple with the moral implications. Ivan Illich at one point calculated the speed at which sin begins. That is, at some point our increase of speed is taken out on the rest of the world through car accidents, extractive industry destruction, etc. Yvon Chouinard says that in all the discussions around energy use, no one ever puts taking a step backward on the negotiation table. How about let’s use less? How about turn off devices? How about not drive? All these suggestions can be deconstructed from an economic point of view; someone will always bring up Al Gore or Leonardo DiCaprio. But those with relative wealth–individuals, businesses, organizations, governments, etc.–consume the most electricity. The moral imperative is theirs, in the case of energy, to take a step back, to design more efficient systems, and, in the cases of Al and Leo, to help educate people on energy.
But I don’t know if the best way to learn is to watch An Inconvenient Truth or Before the Flood. If you want a sense of energy, go to a power plant. See what’s powering your lights. Ask where the resources come from. Find the ways in which you are tangled up in the spaghetti-string diagrams above.