*shudder* That's more or less exactly what I was thinking...Or worrying.

1) It isn't difficult to produce, but it's expensive. Cracking water for hydrogen consumes at least 14kWh, possibly up to 20kWh, just to get a pound of hydrogen. At low American utility rates, that's $1.4 for electricity alone. (That's before touching on storage, distribution, tax, and profit.) It's actually cheaper to produce hydrogen from oil (and, in fact, it's a byproduct of oil refining) than to produce it from water. The vast majority of commercially made hydrogen available today comes from oil.

2) Hydrogen isn't difficult to produce, but it's a pain in the ass to store. Ultra-high pressure storage tanks are heavy and don't deliver the range of an equivalent weight of gasoline. Metal hydrides have similarly low weight efficiencies. On top of having crappy density (70 grams per liter, vs 1000 grams per liter for water), liquid hydrogen defines "cryogenic," requiring much more insulation than liquid nitrogen or oxygen. In fact, storage is probably one of the major stumbling blocks for hydrogen use. That's why fuel cell makers keep using methanol (directly, or cracking it for hydrogen in the engine), and why Chrysler was trying to use gasoline to supply hydrogen for its fuel cell experiments.

3) The "mass quantities" used by zeppelins were not "mass quantities" as the modern transportation industry reckons it. The Hindenberg, with about 8 million cubic feet of hydrogen, had about 20 tons of the gas. That amounts to, what, about the same amount of hydrogen a jetliner would need for one or two flights? A typical car could easily need 500kg of hydrogen per year - 20 tons is enough to power all of 40 cars for a year.

Sure, hydrogen's a great fuel in terms of energy/weight ratios. It's easy to make - you can make in your house with some electricity and water. But as a practical fuel, it's a pain in the butt.

I'll agree that glucose is safer, but what's so dangerous about hydrogen? Sure, it burns nicely, but it's not explosive. As a high pressure gas, it shouldn't be any more dangerous than, say, compressed propane.

Everyone above has produced great arguments as to why hydrogen does not make a very good energy storage medium. Add to that the fact that, even as a pure liquid under several hundred psi of pressure, hydrogen cannot store energy in as dense a form as any current octane blend. That should give you a good indicator of why it is difficult at best to make hydrogen-fueled cars.

But your snide remark here isn't about hydrogen as an energy storage medium, it's about using hydrogen produced through electrolysis as a fuel source. To see why this is laughable, let's do a little basic chemistry. Here's the chemical equation for the production of hydrogen by electrolosys:

2 H2O + (energy) --> 2 H2 + O2

Simple, right? Now, here's the chemical equation for the combustion (burning) of hydrogen:

2 H2 + O2 --> 2 H2O + (energy)

Look a little similar to you? It should, because it's the exact reverse of the equation for electrolosys. Why is this important? Well, the first law of thermodynamics tells us that there is no way we can ever use this cyclic proceedure to create energy. In fact, the second law of thermodynamics tells us that this process will actually result in a net *loss* in useful energy, as both reactions in the cycle will by definition increase the entropy (non-useful energy) of the universe.

Hollywood is capable of pulling weird physics out of its ass whenever it wants to, but in the real world stuff like that movie Chain Reaction do not happen.

No, never, and cars never catch fire and burn because of the gasoline in them.

I was just pointing out that hydrogen is not an explosive, and it is about as safe as other flammable, stored fuels, like propane and gasoline. Obviously, if there's a choice, glucose is favorable (unless there's a lot of ants around ).

Perhaps I'm not making myself clear enough? Let me say it again, just to be clear. Water is the waste product formed by the combustion of hydrogen. It cannot be used to store ot produce energy. Saying that you will store or produce energy using water is as illogical as saying you will store or produce energy in carbon dioxide, claiming that you can use one of many catalysts to turn it back into octane as needed.

There's a difference between having losses in an energy storage system and the energy storage system not being able to produce useful amounts of work.

Sure, there's energy losses in the production and storage of hydrogen. There's also losses in energy when you charge a battery. There's losses when you spin up a flywheel or pump air into a compressed air tank. There's losses when a solar power plants melt and heat salt for night time power delivery. There's losses in every energy storage system.

And, yet, they still deliver power, doing useful amounts of work.

If I use 200kWh of energy from an electrical utility to charge up my (hypothetical) electric car with 180kWh of chemical energy in its batteries, only get 150kWh of electricity back out of the batteries, and only have 135kWh delivered to the wheels, does that mean I was incapable of storing energy in the batteries? No. I got 135kWh of energy out of the batteries.

Likewise, if I use a hypothetical nuclear, solar, tidal, or even oil-fired power plant to "crack" water into hydrogen for my hypothetical hydrogen-fueled car, I'm going to get less energy out of the hydrogen in the gas tank than the power plant put into making the hydrogen. That, however, is not a concern for my car, because it will get energy out of the hydrogen, which provides a fancy means of storing the power plant's energy.

Yes, but it is still much harder to store than propane, gasoline or other flammable fuels.

1) Hydrogen is not very dense (duh, we used to make blimps out of it). Although it's fuel-by-weight ratio is very high, it's low density means that its fuel-by-volume ratio--the ratio that is actually relevant to putting hydrogen in mobile containers like cars and airplanes--is very low. The solution here is to put it at a higher pressure, at eight times the pressure it has the same fuel/volume ratio of propane, its closest analogue. To get to a similar fuel-to-volume ratio as octane you'd need to compress the hydrogen to nearly 4000 times atmospheric pressure, which indroduces several other funadmental problems*. Naturally, higher pressures are more dangerous, and require tougher and more expensive containment proceedures.

2) Hydrogen is a very small molecule. As such, it has the ability to diffuce right through most containers, including most metals. Anyone who has seen how a metallic helium-filled balloon can go flat after a few days is witnessing this phenomenon, one that gets worse when you increase the pressure.

There are more reasons, but most of the big ones I've discussed previously or someone else has. Suffice to say that it's just not feasable.

*- The biggest fundamental problem here is that at such high pressures and temperatures (room temperature is considered "very high" for hydrogen), hydrogen gas becomes what is called a supercritical fluid. This introduces a great many unique complications all its own.

Yes, I know. I gave its liquid density elsewhere in this thread.

However, it can be blocked with the right anti-diffusion liner selection. Of course, that doesn't solve the inability to store a useful amount of hydrogen, just the diffusion problem.

I had a nice link about thin film diffusion barriers, but I need to post this message and close out IE while I figure out WTF is causing me so much trouble with my google searches.

Me, maybe? I gave rather long post on hydrogen's problems, too.

Also note where the majority of hydrogen comes from: in addition to gas pockets, the processing of refining crude oil into gasoline and lighter hydrocarbons produces hydrogen as a byproduct. Or maybe it's the process of making heavier hydrocarbons. But most of that hydrogen comes from oil.

Which means when the shuttle launches and those clean burning hydrogen-oxygen main engines, the oil industry chortles as another 100 tons of its products are burned in about 6 minutes. Actually, I bet the solid booster's 1200 tons of rubber-base solid fuel come from the oil industry, too, and those only burn for 2 minutes...

Yes but it is not as efficent as a fuel. That was a problem with the hindenburg, they used Hydrogen becasue the US denied Nazi Germany Helium which has more lift. To be a fuel you need much more Hydrogen than say propane or methane. More fuel means more pressure or bigger containers which means more likely to have an accident.

Does it? When and where in the typical water-cooled power plant?

I was under the impression significant thermochemical hydrogen production was a goal for high temperature nuclear power plants, but the combination of high temp fission piles and thermochemical hydrogen production hadn't been made yet.