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So I keep hearing about hydrogen fuel cell cars and how they're the eco-friendly future, yadda yadda yadda.
Setting aside all the arguments against hydrogen, from the cost of manufacture to the lack of infrastructure, here's what I'm wondering...
Why a fuel cell? Why not just burn the hydrogen? Seems to me that the fuel cell just adds unneccessary complexity.
It's been done that way too, but theoretically the fuel cells might be more efficient.
Is it more efficient once you factor in the losses of the electric motor in converting the electricity to motion versus the internal combustion engine converting the hydrogen into motion?
And what's really funny is that the biggest offender for greenhouse effects is (wait for it...) WATER VAPOR. What do you get when you burn hydrogen?
Someone ( I think from here) said they had worked on a ford zetec running on hydrogen, and it produced a large amount of NOx becasue the hydrogen burned so hot.
Slightly off-topic, but I think Mazda built a prototype 5 with a hydrogen-burning rotary in it. If that's the eco-friendly future, than I for one welcome our hydrogen-fueled overlords.
I've read that rotaries work particularly well with hydrogen, although I'm not sure why.
Everything's better with magical spinning triangles. 
-There is no combustion in a fuel cell. It emits only water during use. - Hydrogen combustion still results in emissions of nitrous oxides (smog- just like petroleum) - Fuel cell process is theoretically more efficient than combustion (at the point of use)
But, of course, the primary reason is that no one wants to drive a car referred to as "The Hindenberg".
Mazda built a screwy looking hydrogen rotary concept car called the HR-X. It was followed by the HR-X2, which was a family car.
As far as hydrogen working well in a rotary engine, it has to do with burn times and the long skinny combustion chambers. IIRC the hydrogen version was direct injection as well, that's much easier to accomplish in a rotary since the injector doesn't have to battle for space with a bunch of valves and spark plugs and stuff.
On Mythbusters, they ran an Olds something or other on hydrodgen for a min or two before things went kablooey.
Jensenman is right on, it has to do with burn time, people generally think gasoline 'explodes' in an IC engine when rather fuel dropets burn 'relatively' slowly from the outside in at an accelerated rate due to surface area vs volume of the droplet and due to the heating of the inside as the combustion proceeds because air and gasoline is not a homogenous mixture, it is rather heterogenous in fact. Hydrogen by comparison at the temperatures and pressures we're talking about is basically in a pure gaseous state and mixes so fast and easily with the very much larger and heavier air molecues that as soon as you ignite it, it actually does 'explode'. Thus you have to control timing alot, especially under load much more carefully or else EGTs and pressures will become too much for the components of a traditional engine.
This is all without going into the real limitation of a true hydrogen combustion powered car which is the associated cost of cracking water to generate the hydrogen, i.e. it takes more energy to crack the water than you get from burning it so the entire system is even less efficient than face value.
Mazda also had an rx-8 that ran on hydrogen and bmw has the land speed record in a swoopy 3ish looking thing burning hydrogen.
So with burning hydrogen there are draw backs but what I can't stand about fuel cells is the process involved to get the hydrogen. You get water, you add electricity, you get hydrogen, you add it to a fuel cell, it recombines with oxygen and makes water, heat and less electricity. Hmm if only we could just take in power we put into the water to get hydrogen into a car directly....
I see diesels and plug in hybrids like the volt taking over. plug in makes the most sense as the range is still limitless and it can be used as a pure electric.
Hydrogen powered cars and the so-called hydrogen economy is a total farce. Unless someone can overturn the laws of thermodynamics and find a cheap (energy wise) method to make H2 from water. It is not a fuel, it is more of a storage medium of energy. More like a battery than fossil fuels - just like you've got to charge up a battery from some source, you've got to do a lot of work to make the hydrogen. I guess one could argue that gasoline is the same way, but the work required didn't have to be done by us for the most part.
PaulY wrote: So with burning hydrogen there are draw backs but what I can't stand about fuel cells is the process involved to get the hydrogen. You get water, you add electricity, you get hydrogen, you add it to a fuel cell, it recombines with oxygen and makes water, heat and less electricity. Hmm if only we could just take in power we put into the water to get hydrogen into a car directly....
Really, the question is hydrogen vs batteries. Either one can let you use energy sources that couldn't conveniently be shrunk to car size to power a car. Nuclear power is the obvious example here, along with some of the renewables that have massive land requirements (windmills, solar power).
I've sometimes wondered why we haven't seen more attempts at converting coal into something you can run in a car, with the way the price of oil's gone.
There's people working on CTL (coal to liquid) where they make gasoline like stuff from coal.
Were some of the old steamers coal burners?
GM had an Eldo that ran on coal. It was the big one, like a '74 or '75 model and had a turbine engine. You opened the trunk, dumped your coal in there, it had something to grind it up and feed the powder to the turbine. Yet another failed GM venture. They probably killed it because the color didn't match the new building for the executive tennis court.
Albert Arnold Gore, Jr. is the manifestation of our slavery. The United States of America would be the Saudi Arabia of coal. But as long as we are little drones of people like Albert Arnold Gore, Jr., we will never achieve our freedom.
How about propane power? It's very clean, available from friendly folk (Trinidad) not very expensive, and seems to have a good power output. Will power most IC engines without major mods. What's wrong with it?
Propane is already in widespread use in industrial applications like forklifts. Its only real drawbacks are: it contains less energy than gasoline so like E85 you get worse mileage and it has to be stored in a pressurized tank. I suppose it's really no worse than gasoline but there's something about having a 50 gallon tank of pressurized flammable substance in a vehicle on the highway that sorta gives me pause. If you are careful and use common sense it's no big deal to refill a propane tank but I can just see some 80 IQ knucklehead blowing him/herself up at a refueling station. Along with a couple of blocks surrounding them.
FWIW, in the early '80's there was a guy in Columbia SC with an AMC wagon that ran on propane. He had the (huge) tank mounted on the roof rack. 
Ha, the roof rack makes sense, in a crash, that tank will fly away from the car, leaving you un-blown-up
I thought that a big problem with hydrogen was that it was expensive to extract/separate from oxygen (or anything else for that matter). By expensive, I mean it took a lot of energy, say by electrolsys to separate the atoms. But couldn't you use electricity generated from solar power or steam from a plant located near a geo-thermal source to assist with that? From there it's just a matter of distribution. Seems like such a simple solution to me, and since hydrogen is the most abundant element and the only by product is heat and water, I'm not seeing the down side.
My $.02
Getting H2 from water is very inefficient. Throw that in the trash. Burning previously extracted H2 has two main drawbacks; 1) the easiest way to get H2 is from cracking HCs from fossil fuels, and 2) burning it in an IC engine is insanely inefficient. Most of it gets lost as heat. You would have to carry large quantities in highly compressed states to get any decent range, and not too many people want to carry one of the world's most explosive gasses in a compressed cylinder at 1500 psi.
There are several other drawbacks, including the fact that it isn't much help to emissions. Although H2 is the fuel, its still combining with mostly nitrogen. Another drawback is that the violence of the combustion tends to destroy engines rather quickly. I'm sure that is pretty easy to engineer around, but still an issue.
Using H2 to power a fuel cell has only H2 and water as its emissions, requires a small quantity to provide electricity, and for now anyway is a much more efficient means than burning it.
Although the IC engine is a wonderful thing, it is inefficient, old technology. Trying to adapt new fuels and technologies to IC is kinda like polishing a turd. Given the huge world of possibilities that are afforded by alternative propulsion, further fine-tuning of the IC engine is kinda moot. We've put so much time and energy into it getting it really great, but its not going to be easy to take it further. A "simple" jump to more logical means (like electric propulsion from fuel cells) would really be better.
Ummm isn't the tanks in the FCX Clarity pressurized to something like 5000psi Dosn't sound much better than 1500psi really
IIRC the main source for commercially available H2 is chemically cracking it from methane. I do believe Iceland is trying an experiment of using their famous geothermal plant to electrolyze water for use in fuel celled vehicles.
Fuel cell cars are really terrible to drive. I've driven them before (and scared a GM rep almost to tears doing it). Throttle lag is several seconds long, and the performance is abysmal.
Fuel cells can only get so much hydrogen per minute from the system, and that means only so much energy available. So you go slow. You cannot produce enough hydrogen to run an internal combustion engine of any size from the process.
Hess, I've yet to hear from anyone that water is the biggest green house gas contributor. Not from the EPA, Rush Limbaugh, or any right wing or left wing group of fanatics.
billy3esq wrote:Everything's better with magical spinning triangles.
quoted for truth
