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 all just pseudo-scientific bullshit? I get asked about HHO generators all the time.
Here’s the most recent such question from a guy named Mark.
“I have been watching many videos on Youtube regarding the use of HHO generators in Vehicles
Could you please give us pros & cons on this?” I’m John Cadogan from AutoExpert.com.au
– the place where Aussie new car buyers save thousands off their next new cars. Hit me
up on the website for that. And now: jihad on bullshit, captain’s log,
star date 3.141592654. 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 a mere $250 bucks.
Slightly under. 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
electrolytically). 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, so it’s not going to be a problem.) And this
might make you feel really 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, very dangerous. Here’s why.
Spoiler alert. We have to use the ‘T’ word. It’s a big, scary word, too. ‘Thermodynamics’.
Spooky. There are four laws, numbered (perversely) zero through three, inclusive. Defining the
behaviour of energy everywhere. The Leatherman Surge of heat and energy interaction. We only
need to use one of those laws, thankfully – number one.
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. That seems reasonable, and is observationally true, essentially, everywhere. Let’s leave
(sort of) the big bang and black holes out of it, and keep our feet here, firmly on planet
earth. 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. 100 per cent efficiency.
No losses. Wouldn’t that be nice? In this case, every kilojoule of energy in
the fuel gets converted with 100 per cent efficiency into motion, and the first law
is very happy indeed. But obviously there are losses, in the real world, right? Otherwise
you’d never need to fill up at the fuel station. 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 sieve, which is why car owners need to keep filling
up the fuel tank. But the first law is still happy – because
it allows you to pump energy into the box or drain energy from the box just like water
going into and out of a dam. The only thing you’re not allowed to do is magic up energy
conveniently from nowhere. Like Harry Potter with a wand, in the box. That’s not allowed.
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
the exhaust pipe. OK? Let’s put a magic HHO generator inside the
box with the engine. It’s exactly the same scenario here – energy in from the fuel. Energy
out from the crank and waste heat leaking like a sieve. Nothing actually 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. And 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. So 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 in friction, the alternator is also 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 capacity in the system available for you to exploit with any accessory. You
will kill the electrical system if you try this.
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 going to be about
800 watts. That’s about one horsepower. And of course if you burn it in the engine,
about 75 per cent gets chucked out of that box because engines are only 25 per cent efficient.
Leaving you with 200 watts of actual motive power at the crankshaft.
So just to be perfectly clear on this: You need to burn enough petrol to produce 3000
watts of crankshaft power to drive a belt, which loses about 10 per cent on the way to
the alternator. The alternator gets 2700 watts of belt power and produces about 1600 watts
of electricity. The so-called HHO generator turns 1600 watts
of electricity into 800 watts of combustible chemicals, and the engine turns those chemicals
into 200 watts of motive power. And this is the most unrealistically powerful HHO generator
you could hope to install. So we started with three kilowatts of motive
power at the crank and we turned it into 200 watts of motive power with an HHO generator.
Speaking as an engineer, this is not a blueprint for increased efficiency. An HHO generator
is nothing more than a device allowing you to throw even more energy out of the box before
it gets to the wheels. It’s hard to make power at the crank. It’s
really stupid to throw it away once you get it there. And that is really all that an HHO
generator does. A system offering you the unique opportunity to throw 94 per cent of
the energy it consumes, straight outside the box. Yes!
And this is being exceptionally generous. Unrealistically generous. Just leave the HHO
generator out of the car and instead of 200 watts of motive power you get three kilowatts.
That’s a plan. And to all of you who say: ahh – but the HHO
generator uses waste electricity, excess electricity from the alternator, spare electricity: I
am so sorry you are that profoundly scientifically illiterate.
There is no spare electricity in a functioning alternator. The current ratings are the maximum
the alternator will produce. The actual production of electricity by an alternator is a direct
response to electrical load. In other words – alternators produce zero electricity when
they are not powering anything. If you flick on all the lights, the front
and rear demister, you crank the fan on the HVAC, they start working hard, those alternators,
and that’s just how they roll. All of you budding engineers saying you could
use regenerative braking to make the electricity to electrolyse the water: Well, yeah. You
could do this. But in practice it’s just easier and more efficient to brake regeneratively
and store the energy in a battery because – fewer losses.
You could plaster the roof, bonnet and boot with photovoltaic cells and use that, too.
Yeah. But incident sunlight is only about one kilowatt for every square metre, and there’s
maybe two square metres of viable real estate on an average car. And the cells: well they’re
only going to be about 20 per cent conversion efficiency, so that’s going to be about
400 watts of input electricity – but only when you are parked in bright sunlight. Probably
not worth doing really… And it would be a visual abomination. Let’s not forget that.
So apart from being completely ineffective, an HHO generator will cost you money, it’ll
probably shorten the life of your alternator, void your warranty, and pose a significant
fire risk. An ideal, stoichiometric mixture of hydrogen
gas and oxygen gas, plumbed by some amateur through the engine bay, in close proximity
to all that heat, vibration, airflow and electricity. What could possibly go wrong?
And when the insurance investigator gets done with looking into that inevitable fire, discovers
the charred remnants of your ill-fated dalliance with thermodynamics, good luck getting the
insurance company to pay your claim. The differential confirmation that these things
are bullshit is simply that carmakers do not install them routinely as a means of extracting
greater efficiency from an internal combustion engine. Twenty, maybe 30 years ago, someone
invented electronic fuel injection. Carburettors were thrown out, and it’s been adopted on
all engines because it achieves essentially this efficiency increase. Greater efficiency.
If HHO worked, and you thought of it, you’d tender it out for eight figures, and a carmaker
would buy it. But unfortunately it does not work.
These things are 13 different flavours of bad idea, neatly gift wrapped in a gobsmacking
thermodynamic fraud, waiting for some scientifically illiterate muppet to hit ‘buy now’. Do
not be that muppet. I’m John Cadogan. I hope this helps. Thanks