Mechanic's DiaryIt's one thing for
a car to run on air, but do the latest claims of hydrogen-turned-oxygen-turned-electricity propulsion hold water—or feed in to the hysteria of the gas crunch? In his
biweekly online column, PM's senior automotive editor focuses his chemistry prowess on the case of miracle water fuel, then builds an HHO car himself.
From a startup snagging headlines to DIYers posting plans, water-powered cars have been
all over the Web recently—not to mention stuffing my email inbox. Yes, you can run your car on water. All it takes is to build a “water-burning hybrid” is the installation of a simple, often home-made electrolysis cell under the hood of your vehicle. The key is to take electricity from the car’s electrical system to electrolyze water into a gaseous mixture of hydrogen and oxygen, often referred to as Brown’s Gas or HHO or oxyhydrogen. Typically, the mixture is in a ratio of 2:1 hydrogen atoms to oxygen atoms.
This is then immediately piped into the intake manifold to replace some of the expensive gasoline you’ve been paying through the nose for these last couple of months. These simple “kits” will increase your
fuel economy and decrease your bills and dependence on foreign petroleum by anywhere from 15 to 300 percent. There’s even a Japanese company,
Genepax, showing off a prototype that runs on nothing but water. On June 13 Reuters
published a report on the prototype, complete with a now
much-blogged-about video even showing an innocuous gray box in the Genepax vehicle'strunk supplying all the power to drive the car. All you have to do is add an occasional bottle of Evian (or tea, or whatever aqueous fluid is handy), then drive all over without ever needing gasoline. So what do I think about all of this? Why haven’t I tested and written about this stuff? It’s certain to Change the World As We Know It ... right? Rubbish. The only real definitive claim Genepax makes
on its Web site is that its process is going to save the world from global warming. (A request for comment was not returned at press time.) Their Water Energy System (WES) appears to be nothing more than a
fuel cell converting the hydrogen and oxygen back into electricity, which is used to run to a motor that drives the wheels.
Fuel cell technology is well-understood and pretty efficient at changing hydrogen and oxygen into electricity and water, which is where we came in, right? Except the hydrogen came from water in the first place—something doesn’t add up here. Here’s the deal, people: There ain’t no such thing as a free lunch. There is energy in water. Chemically, it’s locked up in the atomic bonds between the hydrogen and oxygen atoms. When the hydrogen and oxygen combine, whether it’s in a fuel cell, internal combustion engine running on hydrogen, or a jury-rigged pickup truck with an electrolysis cell in the bed, there’s energy left over in the form of heat or electrons. That’s converted to mechanical energy by the pistons and crankshaft or electrical motors to move the vehicle. Problem: It takes exactly the same amount of energy to pry those hydrogen and oxygen atoms apart inside the electrolysis cell as you get back when they recombine inside the fuel cell. The laws of thermodynamics haven’t changed, in spite of any hype you read on some blog or news aggregator. Subtract the losses to heat in the engine and alternator and electrolysis cell, and you’re losing energy, not gaining it—period.
But enough about Genepax, which is sort of tangential to my main thesis here, and on to a more common topic in my mail que: HHO as a means of extending the fuel economy of conventional IC engines. HHO enthusiasts—from
hypermilers to Average Joes desperate to save at the pump—suggest that hydrogen changes the way gasoline burns in the combustion chamber, making it burn more efficiently or faster. Okay, there have been a couple of engineering papers that suggest a trace of hydrogen can change the combustion characteristics of ultra-lean-burning stratified-charge engines. Properly managed H2 enrichment seems to increase the burn rate of the hydrocarbons in the cylinder, extracting more energy. However, these studies only suggest increases in fuel economy by a few percentage points and don’t apply unless the engine is running far too lean for decent emissions. That’s a long way from the outrageous claims of as much as 300-percent improvements in economy that I see on the Internet and in my mailbox. There’s no reason to believe that even more modest increases claimed by some of the ads could be achieved by a conventional, computer-controlled automobile engine running under closed-loop driving—that is, the computer’s ability to sample the oxygen output of the engine’s exhaust in real time and slew the fuel/air ratio for big mpg and small emissions. The combustion chamber events are far different in the type of ultra-lean-burn engines where hydrogen enrichment has been seen to help.
Ultra-lean means there’s a lot of extra oxygen around for the hydrogen to have something to react with—far more than the very modest amount we’re sucking in from the typical homebrew hydrogen generator made from a Mason jar. And remember, these studies deal with hydrogen enrichment under closely-controlled lab conditions, not spraying an uncontrolled amount of hydrogen-oxygen mixture into your air cleaner. I’m building a water-electrolyzer car—right now. The electrolysis cell assembly is on my workbench and ready to install, so stay tuned for the test results soon. If it works, then you can believe the hype.
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