Is this how we will propel our cars in the near future?
In, "Buy a Honda, Kill a Polar Bear, " I explored the practicality of hydrogen as a fuel for automobiles, either to use in on-board fuel cells to generate electricity, or to enhance gasoline combustion by adding the hydrogen to the air-intake flow just before injection into the combustion chamber.
Fuel-cell technology is proven and the new, all-electric Honda Clarity is being offered for lease (only) in southern California this year. It is powered only by a fuel cell stack.
As for whether hydrogen-has (H2) injection into the intake manifold of IC engines really is valid for improving efficiency, there are a lot of web sites that reek of snake-oil salesmanship. Promises of up to 60 percent better gas mileage are made. My reservation was not whether H2 injection actually improves gasoline combustion at least some, but whether there is a net energy gain because of the energy required to make the H2 to begin with, especially with on-board H2 reforming or electrolysis.
Setting aside the web sites selling plans for such systems, it turns out that H2 on-board generation is in fact energy efficient. The increased engine power and fuel efficiency is not gained from burning the H2 instead of gasoline. Adding H2 to the fuel-air mixture increases the flame temperature, enables a higher compression ratio and, most significantly, enables the engine to run with greater efficiency on a much leaner fuel-air mixture. All these things combine to improve fuel economy quite a bit.
But only in engines designed for H2 injection. Retrofitting a car with an H2 system gives some benefit, but not a lot, and one auto forum member who tried it pretty much concluded its maintenance and aggravation were more trouble than they were worth.
Note that there is no violation of the laws of thermodynamics here. The improved efficiency does not come from burning the H2, but from H2's catalytic effect on the gasoline's combustion. The energy gained from burning the H2 is less than the energy it took to electrolyze or reform it, but the energy gained from improved gasoline efficiency is more than the energy required to make the H2. And the net energy gotten from the gasoline is still less than the energy it took nature to make the oil to begin with.
Now, on to plasma-drive cars.
Whilst surfing around the Internet getting some links for Avoiding gas-mileage ripoffs, I came upon a site offering for sale a Pre-Ignition Catalytic Converter.
Using a magnetic and electrical reaction to break down the fuel molecules into their elemental state, the PICC creates a plasma, which burns super efficiently and cleanly!
Italics original. The site claims its system can improve gas-engine efficiency by up to nine times. Their test car, they claim, improved from 22 mpg to almost 200 mpg.
I actually laughed aloud when I read that. Yet as it turns out, gas-plasma engines may be a near-term reality after all. That from no less authority than the Los Alamos National Laboratory, which says that Plasma combustion technology could dramatically improve fuel efficiency.
The technology, a plasma combustion technique that applies electrical voltage to the gaseous-phase fuel stream prior to combustion-turning the fuel into a plasma-has already produced excellent results with propane. ...
Kerosene, propane, gasoline and diesel fuel are all hydrocarbons, all made up of the same basic chemical constituents but separated by the size of their individual molecules. The more efficient fuels, and therefore more highly refined and expensive kerosene and propane, consist of fairly small chains of carbon and hydrogen atoms, whereas the less efficient and cheaper fuels, gasoline and diesel, are made of long chains of molecules. According to Coates, when electrodes attached at the spray nozzle of a fuel injector apply enough voltage to the fuel, energetic plasma electrons from voltage-induced breakdown of the fuel cause reactive species to be created, changing the basic chemical composition as the fuel becomes a plasma
"You put into an engine the equivalent of a 'process plant' or fuel refinery," said Coates. "The plasma unit basically acts like a 'cracker' in a refinery, cutting the long chains of hydrocarbons into bite-size parts -- the smaller the parts the better the burn -- taking cheap fuels and making them combust like expensive ones."
The three researchers also believe they can construct a device that is relatively simple, cheap and easy to retrofit to existing fuel injection systems.The Lab makes no claim of how much efficiency will be gained using its system, but it would seem to be a very large amount.
But wait, there's more!
Massachusetts Institute of Technology is also working on plasma system for cars. Their tack is a little different. Instead of making the fuel itself into plasma for combustion, they use a plasma unit to reform gasoline into H2, which is mixed with the air-fuel mixture as I described above:
(Click image for larger view)
MIT claims that their system can make a significant impact on petroleum use by 2025 while fuel-cell vehicles, they say, won't do so until 2050.
Of the two approaches, the Los Alamos system seems to me to offer the most promise because it can be retrofitted to existing engines and because it does not involve injecting H2 into the combustion chamber. It's not that the latter doesn't work, it's that doing so (as a retrofit) runs the risk of hydrogen embrittlement of engine parts and rust of interior engine parts since the product of H2 combustion is water.
Note that the energy required to 'get h2' isn't necessarily loss to the system. It is if you're electrolyzing it, sure, but there's plenty of other ways to make h2 from other fuels. An example would be just decomposition of methane at elevated temperatures. If you can integrate the decomposition and the combustion in the main engine closely together, you can use high temperature waste heat (of which there is lots!) as the method of making hydrogen in the first place.
This wouldn't be 'plasma', exactly, but they seem to be marching in the same general direction.
"since the product of H2 combustion is water."
Water is a part of the combustion products of every hydrocarbon. Methane, for instance, CH4, combines with two molecules of O2 to make one molecule of CO2, and two of H2O.
Hydrogen embrittlement might be a real issue, but I doubt rust from H2 injection would be.
I do remember reading on one of the H2 sites that if you convert your car to run on H2 enhanced combustion, it is a good idea to replace the valve covers with a stainless version. The site said it is not expensive to do so, but I wouldn't know myself. I assume the valves themselves are suitably rust resistant already.
I discussed reforming H2 from its source, using the exhaust heat, in the first post, "buy a Honda...", cited in this post. GM is pursuing exactly that research angle, using the auto's fuel itself as the H2 source.
The Los Alamos article is from 2003. On a quick search I couldn't find an update - do you know if there has been one?
Good question about that 2003 article. Since it was about getting an engine in 2003 to do experiments on there should be results from the experiments by 2008. No?
I have long been curious about Fuel Cell technology. We want this technology to reduce the consequences of global warming, one being rising sea levels. So, to do so we propose to create more water with fuel cells and I don't understand how this will not increase sea levels.
Nate:
Hydrogen is currently produced by steam reforming, in which water as steam reacts with a carbon-containing fuel (coal, methane/natural gas, light naphta). This process consumes water.
In some visions of the future, hydrogen will be produced by electrolysis and/or solar-powered cracking of water, closing again the cycle.
Nate;
It is hard for me to come up with a suitable comparison to communicate to you the quantity disparity between human production of H20 and the water in the sea, but try this: throwing teaspoons of sand into the Sahara.
Rising sea levels would only occur as an indirect result of human action, through increasing atmospheric and ocean heating. Warm water expands. Melting ice caps fill the oceans somewhat higher. Those are the ONLY two ways we could increase sea levels.
As it happens, since about 1998, neither is occurring overall. Recently the ice caps have been expanding, and oceans have been cooling.
If you produce hydrogen from water, you don't have any problem of rising sea levels.
I don't think either that rust is a problem in hydrogen fueled SI engines. As in a boiler, the water is expelled as water vapour. The engine keeps moving aspirating air and removing all the product gases for a while when you cut off the fuel, cleaning it from any vapour that might condense later, when it cools.
It is known that injecting hydrogen along with gasoline increases the octane number of a fuel. It might yield a better efficiency, however, the control problems and complexity of such and engine could counterbalance such improvements, since, if the octane number is not constant (or varies in a close range) you have to regulate the pressure inside the engine thorugh the turbocharger, as in an airplane, the engine would also have to be more robust indeed, more weight...
The underlying problem, IMHO, is that the alternative engine we love (its sound, its vibration) cannot compete in efficiency and torque vs. speed with an electric one. We'd already be driving electric cars if electricity could be stored as chemical energy is stored in gasoline.