The cheetah in the figure knows very well that it cannot spend more energy in chasing the impala than the impala can provide once eaten (in other words, the cheetah needs an energy return on the investment (EROEI) >1). Carnivores make no calculations about that question, they only know that, if they want to survive , they have to run. And this is our destiny, too. If we want to survive, we need to build new energy sources to replace fossil fuels and to that before depletion or climate change (or both) destroy us. But, unlike lions and cheetahs, we tend to discuss a lot on the subject and, sometimes, to get it completely wrong. This is the problem with the recent movie “Planet of the Humans” and its totally wrong evaluation of renewable energy (image by Nick Farnhill, creative commons license)
Years ago, when I discovered the concept of “EROEI” (or EROI), energy return for energy invested, I was both delighted and elated. “Here is,” I thought, “an objective way to evaluate and compare the efficiency of energy technologies. No more shaky financial calculations, no more ideology, no more politics, only facts. And everyone has to agree on the facts.” And the beauty of the concept was that if the EROEI is smaller than one for a certain technology, then it is an energy sink, not an energy production system.
I was wrong more than I could have imagined. From when the idea of EROEI was first proposed, in the 1980s by Charles Hall, the concept was stretched, squashed, squeezed, twisted, and shaken until it became a useless mongrel. Ideology took over from physics and EROEI became a support for preconceived ideas rather than an evaluation tool.
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