The Energy Bottom Line
by Jerry Silberman
Editor’s note: This is Part Three of a series that concludes in July.
Question: Which kind of energy is the most efficient?
The Right Question: How much energy does it take to get energy?
The most important aspect of energy that most people have never heard of is “energy return on energy invested,” or EROI. In business, profits are the money left over after all expenses of business are paid. Widening the profit margin is what businesses strive for. The business that can bank $10 in profits out of every $100 sale will do much better than a competitor that can only manage to gain $1 on each $100 sale.
The potential energy of a fuel, or of a sunbeam, is not what’s most important about that energy source. What’s most important is what proportion of that energy will be needed to make the rest of it available for useful work. That’s the energy profit margin.
If it takes 5 percent of the energy contained in a barrel of oil to make the rest of that barrel available as diesel fuel for a truck, then the EROI, expressed as a ratio, is 19-to-1. The higher the EROI, the more energy is available to do society’s work. The more complex our society, the more energy we need to maintain it. The extremely high EROI of fossil fuels compared with any prior sources of energy has allowed us to develop the most complex society in history.
Another critical concept in understanding the system by which we energize our society is “low-hanging fruit.” We always will pick the apple easiest to reach from the ground before pulling out the ladders. It takes less time and energy to do so, and like water, we’ll take the path of least resistance. The apple at the top of the tree may contain a few more calories of food energy than the one at the bottom, but by the time we fetch the ladder and climb up, we will get a far smaller return of energy from it. (We need to save up something to be able to play baseball.)
Let’s apply these principles to our primary nonrenewable energy source: oil.
Fifty years ago, most oil was extracted from shallow wells and was under pressure that minimized the need to pump. An amazing EROI of up to 40-to-1 characterized the Texas oil industry. (The energy in one barrel of oil was enough to produce 40 barrels, 39 of which could be used to power society.) That oil is gone, and today we need to frack, and drill in the ocean, and EROI is between 12-to-1 and 15-to-1 now—and dropping steadily. That’s depletion at work.
Those numbers, however, are still significantly better than most renewables. How would these principles play out with photovoltaic electricity, usually referred to as solar energy? The amount of sunlight arriving daily on the planet is not going to change within any time frame relevant to humanity. The solar energy industry in recent years has greatly increased its efficiency, converting a much higher percentage of incoming solar energy to useful electricity. Can’t we count on this technological improvement to continue?
There are different limiting factors that impact EROI. First—and this is important—the energy required to improve the technologies for the extraction of useful electricity from sunlight comes mostly from fossil fuel energy. What we consider a clean technology is subsidized by the fossil-fuel-driven economy we live in.
Mining, transporting, and processing chemicals and metals from around the world to build photovoltaic installations all depend on the subsidy of the fossil fuel economy, and on industrial processes that cannot run efficiently on energy in the form of electricity. As the cost of producing fossil fuels increases, because of depletion, those increases affect the EROI of photovoltaic electricity.
Second, the technology to convert many functions of society that are not already accomplished with electricity, such as transportation, is not practical. (Low-hanging fruit—if electric cars were easier to make or more efficient, they would have been on the road en masse long ago.)
Third, the intermittent nature of solar energy (and wind) presents huge problems. Our current electric grid relies on generating a constant “baseload” and then increasing generation as needed. Electricity demand changes hourly, daily and seasonally. Nuclear plants and coal-fired plants, being the most costly to start up or shut down, usually run continuously with fixed output. Gas generators can be fired up or shut down much more efficiently, and so operators turn them on or off as needed.
But because solar and wind generation are unpredictable, they cannot be relied upon for baseload electricity. In order todo so, we would need to make immense investments in generating capacity that far outstrip our actual needs. We also need to invest in technology to store large amountsof energy—batteries, pumped storage and other methods—which is unnecessary in our current fossil-fuel-based system.
The takeaway here is that energizing our society relies on a very complex system with many variables and limiting factors. To think about the changes needed to make that system sustainable requires a system view, rather than hoping for a simple, single adjustment to make it work. With this framework, we will return in the final column of this series to revisit whether renewables can really power our society.
Jerry Silberman is a retired union organizer who now devotes his time to negotiating a resilient future for all of us.