Every spring, the Lawrence Livermore National Laboratory and the Department of Energy produce Sankey diagrams showing energy flows in the U.S. I have called it “The Chart That Explains Everything,” and every year, we look at it to see where our energy comes from, where it goes, and how much is “rejected energy” that is lost up the smokestack or out the tailpipe as heat and waste. Except for this year, I forgot and was reminded recently when Physicist Allison Bailes III used the chart to explain the meaning of rejected energy. But before we get to that, let’s look at the lessons from Livermore’s 2021 chart.
The first lesson is that energy consumption is way up over 2020 when consumption was 92.9 quads. A quad is a quadrillion BTUs (1015) and is equivalent to the energy in 8,007,000,000 gallons of gasoline—it’s big and so is the increase of 4.4 quads. But we are not quite back to the pre-Covid levels of 2019 when energy consumption was 100.2 quads.
Low carbon sources like nuclear and renewables were up again, a teensy 0.132 quads over 2020, which is kind of insignificant compared to the 2.9 quad leap in petroleum at the same time. At that rate of growth, it is going to be a long time before the “electrify everything” gang has enough juice to replace all that petroleum, coal, and fossil gas.
But wait! Saul Griffith and the Rewiring America team point to all those 65.4 quads of “rejected energy” and say, “Look how much energy we save when we go all electric!”
In his book “Electrify,” Griffith looks at this chart and says if everything is electric, then we only need about 42% of the energy we are using now. Alas, this is where Bailes and that guy at the top of the post, French military scientist and physicist Nicolas Léonard Sadi Carnot, come into play.
If you look at the Sankey Diagrams from the ’90s and earlier—published in my earlier post here—the big block of Energy Services is labeled “useful energy.” This is because a lump of coal isn’t a lump of energy; it is a lump of carbon that reacts with oxygen to make heat and carbon dioxide.
As Bailes notes, we use the heat to do work, whether driving a car or spinning the turbine to generate electricity: “All of those processes involve a heat engine, a device that turns heat into work. Heat moves when there’s a temperature difference, and the second law of thermodynamics tells us that heat always moves from a warmer place to a cooler place. That means heat engines won’t work without a temperature difference.” But there is no way to convert all of the heat into useable work.
Carnot also figured out that efficiency depends on the temperature difference. Bailes noted, “For the temperatures used in conventional electricity generation plants, about two-thirds of the energy in the fuel turns into rejected energy. Combined-cycle gas turbine power plants can achieve higher temperatures and get efficiencies up to about 60 percent. Automobiles reject about three-fourths of the fuel’s energy.”
This is a fact of life, a law of thermodynamics. This is why the electrify everything gang is being disingenuous when they say we will only need 42% as much energy; we need the exact same amount of useful energy; the rejected energy was never on the table. Carnot showed this in 1824, entered an asylum suffering from “mania and delirium” in 1832, and died at the age of 36 shortly after. But he is now known as the Father of Thermodynamics, and Bailes explains the big lesson from him that we all need to understand:
Or, as the old joke goes, when there is a huge solar energy spill, it’s just called a nice day.
This also brings us back to the question of where we are going to get all this renewable useful energy. We’ve got 15.446 quads of clean, usable energy now; subtract that from the total usable energy we consume, and we need to find 16.36 quads in a hurry. It’s not going to be hydro, nukes are contentious and slow to bring online, so it looks like a lot of solar and wind, although I have great hopes for geothermal.
So once again, I am going to learn from Livermore and make my efficiency and sufficiency arguments. We won’t need much more electricity for residential or commercial if we get seriously efficient and build everything new to the Passivhaus standard and if we insulate and heatpumpify what we have now. We won’t need as much for industrial if we stop making so much steel and concrete. We won’t need as much steel or concrete if we stop building so many cars and parking garages and highways.
This year, Livermore has published a Sankey Diagram for Carbon Dioxide Emissions, and it tells a similar story. Although it can be deceptive since the bulk of those electrical carbon emissions really is residential and commercial emissions—if you look at the Energy Diagram, that is where the electricity is going. But the song is the same: The bulk of industrial emissions are from making steel and concrete, which primarily go into roads, cars, and buildings. And the biggest direct source of emissions is transportation, primarily driving cars between buildings. Along with the original Livermore Chart that explains everything, it tells us what we have to do.
