Yet another geek blog

1 August 2008

Like Water for Octane

Water to Fuel

Recently, my local news paper carried a story about a local man turning water into fuel.

The article starts of fairly reasonably. It even manages to avoid the dreaded words "water powered car", perhaps to avoid sounding like something from The Lone Gunmen. In fact the tone is so restrained that many people I know have been taken in by it- hence the blog. So, lets work through it.

Can you power a car by water?

No. In fact all so called water powered cars produce water as a waste. They are no more powered by water than a torch is powered by a flat battery.

So what is happening here?

Water is being split into a highly combustible mixture of hydrogen and oxygen. This mixture is then added to the petrol in a car and burnt along with it to propel the car forwards.

But that is the same thing!

That is indeed what you are being invited to believe. But the energy is not coming from the water.

The Science Bit

The First Law of Thermodynamics states:

You get nowt for nowt.

The car is being propelled forwards by some energy. The first law tells us that this energy cannot be coming from nowhere. So where does it come from? It comes from the mains. The machine splitting the water needs to be plugged in and the energy it takes pushes the car. All that is happening is that your fuel bill goes down and your electricity bill goes up. And where does the power for the mains come from? Burning oil.

But it only takes as much energy as a light bulb!

This figure is meaningless and irrelevant.

Meaningless

It is meaningless because it does not say how long you need to run the generator for to produce a given volume of gas. Nor do we know how long a given volume of gas will run the car. Remember, if the generator uses as much power as running a light bulb for a year to produce as much gas as it takes to push the car for a second then we could still make this claim.

Irrelevant

It is irrelevant because it does not matter. The energy given to the car will always be less than the energy taken from the mains.

The Madness Continues

But wait; I have saved the best till last! Mr Thompson goes on to say:

Something like this, maybe a little more compact in time, could be mounted in a car and you wouldn't have to refuel. You could drive along and produce the gas as you're driving.

Now we are completely into the realm of magic.

Several people I have showed this to take this to mean that a car can be built to run on nothing. Let me bend over backwards and imagine the most reasonable interpretation of this sentence. A unit like this could be fitted to a petrol powered car so that the motor generates hydroxy gas as you drive. The hydroxy gas improves the fuel efficiency of the car.

Sounds perfectly reasonable until you remember that the energy making the hydroxy gas comes from the petrol. The energy in the petrol is all you are putting in and that is all the energy you will ever get out. Even if you could make the machine weightless and 100% efficient you still need to add the weight of the water (which was not there before).

In other words, a car with this device would never be an improvement on a car that did not.

An Age Old Dream

Machines like this have been imagined for centuries. For example, it is perfectly possible to design and even build a water wheel that lifts buckets to return the water used. But these machines never work because you can never get out as much energy as you put in.