The Crash Course - Chris Martenson [95]
Energy comes in many forms, ranging from highly concentrated to diffuse, from extremely useful to utterly useless for the task of performing work. The least-concentrated form of energy is diffuse heat at the background temperature (whatever that happens to be), and that form lives over on the “completely useless” end of the work spectrum. No machine in the world can perform net work from a single temperature reservoir, no matter how much heat energy it contains; work can only be extracted from heat if there’s a temperature difference between two separated reservoirs. For example, there is an enormous amount of heat energy contained within Lake Superior, but we cannot hook a machine up to it and use that energy to perform any work.
The second law states that as we transform energy, we always start with a concentrated form, like diesel fuel or a stick of wood, and after we’ve transformed it into something else, we’re left with whatever work that energy performed plus heat—random, diffuse heat. Our unavoidable entropy tax.
Think of the Second Law of Thermodynamics as a frictionless slide (meaning you can’t wriggle back up the slope to a higher spot), where at the top of the slide is beautiful, wonderful, concentrated energy, and at the bottom is diffuse heat. At the top of the slide we might put heating oil and 50 degree air molecules, and at the bottom we might put 70 degree air molecules. Once that heating oil descends and is converted into heat along the way, the trip down the slide is over and done. Once that heating oil has taken its trip down the slide, no more work can be performed from the energy that the heating oil once contained.
Suppose we put some natural gas, a marvelously concentrated form of energy, at the top of the slide and then use it to turn an electrical generator. The natural gas, when burned, performs some work by turning the generator, while the rest is turned into heated exhaust molecules. In asking the natural gas to perform this work, we nudge it down the slide, and it races to the bottom, while performing some useful work and paying the entropy tax along the way. Work and heat.
When energy takes a trip down that frictionless slide, it’s a one-way trip. Water never flows uphill and burned hydrocarbons never magically reform themselves out of exhaust fumes. Every form of energy gets only one turn on the slide.
Given this, I like to think of the concentrated energy that we have been given as a one-time free gift of energy perched at the top of a frictionless slide. Our choice is whether we’re going to do something truly useful with that energy when we push it down the slide, or simply turn as much of it as we can into useless heat as fast as possible. Either way, we only get to do it once.
In all of history, we’ve never, not once, violated this law of entropy. If we did, it would be the most spectacular news in scientific (and human) history, and many people, especially me, would scour the findings with great excitement to be sure they were true. But we quite regularly read about people who have claimed to violate this law. Nearly every year, claims surface that a perpetual motion machine that produces more energy than it consumes has been invented. The inventors of these magical devices demonstrate a remarkable ability to secure gullible media interest, and sometimes even deep-pocketed investors, but not one of them in all of history has ever produced a surplus-energy-perpetual-motion machine that actually works as claimed. To do so would mean that a perpetual motion machine would be able to nudge some energy down the frictionless slide and harvest enough work along the way that the same amount of energy could be pushed back up the slide as was used. You might as well try and lift yourself into the air. Needless to say, the law has