It can be hard to get your head around just how much energy the world uses. Expressed in terms of oil, it was equivalent to almost 14 billion metric tons of the stuff in 2017. That’s like burning through all of Russia’s proved reserves in the space of 12 months, which is, in technical terms, a lot.
But there’s an even trickier issue to ponder: What does it even mean to “use” energy? Granted, that sounds like something you might hear from a stoner at the engineering faculty. But it’s an increasingly important question as renewable energy and electrification expand.
Harry Benham, an oil-industry veteran who now runs Carbury Consulting, wrote an elegant blog post this summer about the fundamental difference between thermal energy — mostly from burning stuff or splitting atoms — and what he calls the “universal energy” captured in wind and solar power. While earlier shifts, such as swapping wood for coal, are often called energy transitions, they were really substitutions of one thermal source to another. But wind and solar “are different energies in kind, not degree.”
The big thing here is waste. Broadly speaking, when you burn a gallon of gasoline, perhaps only a quarter of the energy released actually goes into turning the wheels. The rest is wasted, mostly as heat. In other words, you buy roughly four gallons of gasoline to get the useful energy of one. Renewable energy doesn’t work that way, with wind turbines or solar arrays effectively capturing energy from the ether. Yes, they only convert a portion of the energy hitting them into electricity, but that energy is infinite and hasn’t had to be mined or pumped and transported.
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