Coming up: HHO generators for your car. The dark side of the lightest element in the universe - none other than hydrogen, the power source for the Sun. Can you generate this in your own engine bay and save money on fuel, or is it just pseudo-scientific bullshit?
Executive summary: HHO generators are bullshit because they do not work. They do not work because, scientifically, they cannot work. You will not save any money. You will not save any fuel.
You can buy a so-called HHO generator on eBay, etc., like this one claiming to produce four litres a minute. Four! For under $250 bucks.
So, if you’ve got the hots for what’s in the box with the dots, you should know that such a device probably will use electricity from your car and electrolyse water to produce both hydrogen gas and oxygen gas (two litres of hydrogen for every litre of oxygen - because that’s just how water rolls when it decomposes).
You probably can pump it into your engine and burn it. (Combustion converts it back into water and releases energy. There’s already a helluva lot of water in exhaust.) And this might make you feel good. It might emotionally empower you in some perceived asymmetric conflict with Big Evil Oil. But it will not save you any fuel, and it could even be very dangerous.
Here’s why.
The first law of thermodynamics says that if you put a box around a system, and energy cannot get into or out of the box, then the total amount of energy in the system doesn’t change. Seems reasonable, and is observationally true, essentially, everywhere.
The first law is essentially the ‘anything that sounds too good to be true almost certainly is’ law. So let’s put one of those boxes around your car. No energy in; no energy out. And let’s make it an ideal car with an ideal engine where all of the energy in the fuel gets turned into motion.
But obviously there are losses, right? Otherwise you’d never need to fill up the fuel tank. Engines - really good ones - are only about 25 per cent efficient. You lose 75 per cent of the energy in the fuel mainly as internal friction and waste heat. Mainly as heat.
There’s rolling resistance, transmission losses, aerodynamic drag and of course the driver ultimately hits the brakes, which turns all your residual kinetic energy into waste heat, which you throw outside the box by bleeding it off into the surrounding air. In other words, the box leaks energy like a seive, which is why car owners need to keep refilling the tank.
So let’s just put a box around the engine. You’ve got chemical potential energy coming in from the fuel, you’ve got rotational kinetic energy leaving the box via the crankshaft and a bunch of mechanical losses - mainly waste heat - leaving via the radiator and exhaust pipe.
Let’s put a magic HHO generator inside the box with the engine. It’s exactly the same scenario - energy in from the fuel. Energy out from the crank and waste heat leaking like a sieve. Nothing changes.
So unless the HHO generator has a means of reducing the waste heat or other losses it will never be able to deliver more energy at the crankshaft. And it is impossible for the HHO generator to do this. Here’s why.
The electricity required to electrolyse the water (to split it up into so-called HHO) comes from the car’s battery. And the electricity in the battery comes from the alternator, which is driven by the engine.
Let’s put the battery, alternator and HHO generator in a thermodynamic energy box, just for kicks. Energy comes into the system from the belt driving the alternator. Energy goes out in the form of chemical energy in the HHO ready to burn.
The belt loses about 10 per cent of its input energy to friction, the alternator is not especially efficient because efficiency is not as important as robustness in the context of alternator design and operation. But a typical alternator might be capable of producing a maximum of 120 amps at 13.5 volts - that’s about 1.6 kilowatts.
Trust me on this - you cannot put a 1.6 kilowatt electrolyser under the bonnet. Bad idea. Because there is not anything like this spare capacity in the electrical system available for you to exploit with any accessory. You’ll kill the electrical system.
So this is an entirely generous proposition for the HHO generator. The best small-scale industrial alkaline electrolysers (which an eBay electrolyser is, frankly, not even close to being) is about 50 per cent efficient.
So the chemical potential energy in the so-called HHO coming out of the most overly generous underbonnet electrolyser is about 800 watts. That’s about one horsepower.
And of course if you burn it in the engine, about 75 per cent gets thrown out of that box because engines are only 25 per cent efficient. Leaving you with 200 watts of actual motive power at the crankshaft.
