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The Right Question: It’s Time for a Little Physics 101


Illustration by Jameela Wahlgren

Illustration by Jameela Wahlgren

Stop Confusing Energy with Electricity

by Jerry Silberman

Question: Can we run our entire society on solar energy?
The Right Question: Which kind of solar energy would you like?

Right now, more than 90 percent of all of our energy needs are powered by the sun, so we can answer the first question “yes” and stop worrying about whether our lifestyle is sustainable, right?

Maybe not.

Before we discuss the different kinds of solar energy, we need to have some basic definitions. The way the word “energy” is used in the media, mainstream and otherwise, suggests that it is not well understood. In fact it’s quite simple. Energy is an abstract concept, not an object. Energy is the capacity to do work. You can’t hold energy in your hand.

Work, in turn, is defined in physics as simply causing something to move. So the work of rolling your bowling ball down the lane requires a certain amount of energy. Depending on your skill, some of that energy used to move the ball will do additional work at a distance: knocking down pins. What’s left of the energy in the ball, after some is absorbed by friction on the lane and impact with pins, will be transferred to the bumper at the end, which will move slightly (and heat up slightly) as the energy is dissipated. In the course of doing work, energy is dissipated into the surrounding environment, mainly as heat. It is then too diffuse to do any more work, and it will keep diffusing out into the universe.

We need concentrated energy to do work. Fuels are concentrated sources of energy, substances in which a great deal of energy has been stored in chemical form—and is stable over time. That stored energy is usually released by burning it to heat air or water, whose motion, in turn, we use to run complicated systems, such as automobile engines, or fairly simple ones such as fireplaces. Each time we change the form of energy, a portion of it is dissipated as heat: A smaller part is literally burnt off, and a larger portion actually does the useful work we seek.

Electricity is not the same thing as energy. Electricity is a very versatile form that energy can take to do work for us, and the generation of electricity is a transformation that loses power along the way, like any other. Usually, references to renewable energy mean “electricity derived from renewable sources.” Since most of our energy use is not in the form of electricity, this reference is often misleading.

One way to look at the trajectory of human civilization is to look at how efficiently we have been able to find and use various forms of concentrated energy to work for us. We’ll come back to this, but first let’s look at the flavors of solar energy that power our society today. Each kind of solar energy is a variation on the theme of capturing the energy in photons from the sun and transforming it so that it can work for us:

Photosynthesis. All of the energy in every molecule of food we eat was originally stored by a plant that can store the energy of photons in its own tissue through biochemical reactions.

Fossilized sunlight. Oil, coal and gas began as photosynthetically produced tissues, isolated by geological processes from the cycle of life, and further concentrated by the force of gravity.

Biomass. This is mainly firewood, on a global basis.

Hydropower. Incoming solar energy turned to heat in our atmosphere allows us to have weather. Temperature gradients give us the movements of the atmosphere and the hydrologic cycle, by which water is evaporated and returns to the ground as rain. Dams store energy mechanically, rather than chemically.

Wind power. Solar energy creates temperature differences in the atmosphere, which result in air currents. Windmills convert this kinetic energy directly into electricity.

Photovoltaic electricity.  Electric charge is captured directly from photons and converted by chemical processes to electricity in a form we can use directly.

What’s left? Nuclear electricity accounts for 3 to 4 percent of our total energy use. Uranium, the fuel for nuclear energy generation, is a nonrenewable resource, and its production is past its peak.

Over the last 200 years, the flow of energy through human society, both as a whole and per capita, has increased by several magnitudes, a situation that is overwhelmingly due to the consumption of fuels from category two above: fossilized sunlight. This, in turn, has resulted in an increasingly unstable climate, along with pollution that threatens to overwhelm public health.

The quantity of energy flowing through our (American) society is staggering. We know that it has to be reduced and restructured substantially to have a sustainable society for the next seven generations. Two “right questions” are: Where is substitution or reduction possible? What choices make sense for individuals, and which must be made at a societal level?

Before we can answer these, there is much more to understand about how energy works now in our society. Which sources of energy are used for what tasks? What are the costs of using energy (environmental and economic) as we do now? Over the next several columns, we will cover some background information needed to discuss the right questions above.

Jerry Silberman is a retired union organizer who now devotes his time to negotiating a resilient future for all of us.

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