The Crash Course - Chris Martenson [94]
Energy can neither be created nor destroyed. So says the First Law of Thermodynamics. Energy can only be transformed from one form to another, such as when coal is turned into electricity, which becomes the cold air blown into a dentist’s office in summer. Not once, not ever, not in any laboratory in the world, not even for a millisecond, has technology created more energy than it has used. Energy has certainly been transformed in quite brilliant ways, but the final accounting is always the same: Just as much energy exists as before the transformation; it’s just that some of it is now in the form of diffuse heat that is useless for performing any work.
This is where the Second Law of Thermodynamics comes in. It governs what happens to energy when it’s transformed: Every transformation always loses at least a little energy (and sometimes quite a lot) in the form of diffuse heat. Diffuse heat is the tax that the universe places on all energy transactions. There’s nothing wrong with diffuse heat—those of us in the northern United States happen to love it in our offices in February—it’s just that diffuse heat cannot perform any work, and it’s the work that energy performs that we’re mainly after. It bears repeating: Every single time we convert energy from one form to another, we lose some of that initial energy content to the universe in the form of heat.
For example, we might burn coal to turn into electricity, which we then use to split water so that we can capture and use hydrogen. Following this same set of transformations using the Second Law of Thermodynamics as our guide, we get the following: (1) When that coal is burned, about 40 percent of the energy it initially contained goes toward turning the electrical turbines, but 60 percent of its energy is lost to the universe as waste heat. (2) The electricity travels to the site where the water will be split, losing 7 percent of its energy along the way in the form of nicely warmed transmission lines that gently radiate their heat into the universe. (3) The electrolysis is performed, splitting water into oxygen and hydrogen, with 80 percent of the energy in the electricity captured in the form of pure hydrogen and a final 20 percent lost as heat. At every step, the universe demanded and received its tax in the form of diffuse heat. In this example, the final efficiency of converting coal ⇒ electricity ⇒ hydrogen is 0.40 × 0.93 × 0.80 = 30 percent. In other words, the act of converting coal to hydrogen loses 70 percent of the energy in coal to the universe.
The universe always tends toward randomness as it ceaselessly strives toward its goal of someday reaching one very average and uniform temperature. This is the law of entropy. Entropy represents the amount of energy in a system that is no longer available for doing mechanical work. At each stage of our conversion of coal into hydrogen, entropy (randomness) increases. Perhaps confusingly, lower entropy means there’s a higher level of order in a system. As entropy increases, so does disorder and randomness. Entropy then, is the name of the tax that the universe places on all energy transformations.
Entropy is the reason that your coffee cup starts hot and gets cold, but never starts warm and gets hotter all on its own. Cold molecules are slower-moving, closer together, and more orderly than heated molecules. They have less entropy than warmer molecules. It is the rule of the universe that high entropy always runs toward low entropy and never the opposite, just as running water always heads toward the sea. All molecules with higher disorder (heat energy) seek to share their wild exuberance with molecules that have less disorder, never the other way around. So your coffee cup starts hot but grows cooler,