05.23.06
Why can’t a car engine run on water?
I recently came across a mention of yet another inventor who supposedly has built a car engine that runs on water. The claim is in a video which doesn’t play on my computer, so I don’t know much for details of what he’s actually claiming. But even without watching the video, I can say with almost absolute certainty that this inventor hasn’t built a car powered by water.
I’m sure of this, even though I have no idea how this engine is supposed to work. Why? It’s a matter of applied thermodynamics.
First, imagine that the engine is in a black box. We can’t see into the black box, so it could be any possible type of engine that has been or will be invented. All we can measure is what goes in and out.
What goes in is basically just the “fuel”: room-temperature water. There might be some air with it, too. There are a couple of things that come out: The exhaust from the engine, and the power from the engine — maybe in the form of a shaft coming out of the engine that it’s turning, or something.
According to the First and Second Laws of Thermodynamics, available energy cannot be created, though it can be destroyed by turning available energy into unavailable energy. If we apply that principle to the box with the engine in it, it’s pretty clear that the sum of the available energy that goes into the box and what is in it when we start running it has to be at least as much as the sum of what comes out and what is in it when we finish.
Now, this is an “engine”, not a storage system; it’s not allowed to be running off some sort of hidden internal energy supply that’s also contained in the box. So, if the engine isn’t cheating, the amount of available energy in the box when we start will be the same as the amount when we finish. Thus, we conclude: what goes in must be at least as much as what goes out.
So, look at the available energy that’s in that exhaust. Whatever the exhaust is, it has to contain the same hydrogen and oxygen atoms that came in with the water, along with the atoms that came in with the air. It could hot steam — which has higher available energy than the water that came in. It could be some other compounds of hydrogen and oxygen and stuff in the air — and all of those have higher available energy than water and air do. It could be a cool wet fog, which has slightly higher energy than the water. It could even be ice, but even that has higher available energy than room-temperature water. The best possible case is that it could be room temperature water and air just like what came in, and have the same available energy.
That means that the available energy that comes out in the exhaust is at least as much than the available energy that goes in with the fuel and air. And there’s supposedly even more energy coming out via the power from the engine — thus, the output is claimed to be higher than the input.
This is obviously a contradiction. We just found that, by the laws of thermodynamics, we can’t have more energy coming out in the exhaust and power shaft than what came in with the fuel.
Thus, the engine is impossible.