hi
i've read that in case of a leakage in a hydrogen powered vehicle,there is less chances of a fire as compared to a petrol powered vehicle.i think hydrogen powered vehicle should be more risky sinse h2 is highly inflammable and as in the sun there are always explosions happenings(fusion) due to h2 and O2.what do u think about it?

Fusion needs incredibly high temps, like the kind you find in the sun.

I think that the biggest risk with converting vehichles over to hydrogen power is that you have to drive around with a tank full of compressed hydrogen in your car.  (Probably a tank of compressed oxygen too).

I've heard of a couple of ways to make transport safer though, like storing the hydrogen in sodium borohydride.  This might not be pratical for cars though.

The other problem is that if we go to a hydrogen fuel economy then we would need literally tons of hydrogen.  You'd have to make the hydrogen from something like water, but that takes a lot of energy in its own right, so you still have the same problem.

Or possibly just nuclear power plants to make hydrogen....

That solar thing is really cool.  I thought that in general solar power wasn't efficient enough to make large amounts of hydrogen though.  Solar plants just take up too much space in order to generate a comparable amount of power.

I was in Iceland about a year ago and they are all excited about the potential of a hydrogen economy because they have so much geothermal and hydropower that the would be able to produce hydrogen very cheaply.  This would almost certainly be an ideal method of obtaining hydrogen, unfortunately not a lot of places have access to that much electricity because geothermal power is only practical in a very volcanically active area such as Iceland.

Cool idea though for sure!

The next energy source should be sugar, if it is good enough for every other animal on the planet it should be good enough for us. Plus you can just grow it.

I personally think that hydrogen internal combustion engines are the way to go.  Here's my reasons:

1. Hydrogen generates a tremendous amount of power, and a small engine with hundreds of HP will go over well with all of us who are in love with speed.

2. Hydrogen combustion engines get insane fuel economy (estimates I've heard quoted about 300-400mpg)

3. Yes, you'd have to carry liquid H2 in a tank.  Who cares?  NASCAR, F1, etc., have all had crash cages around their fuel tanks for years.  Simply design one that fits around the H2 fuel tank and have a fail closed valve to it.  It if loses power or becomes disconnected, it simply mechanically fails closed.  These valves are common in industry.  Even if the thing is really heavy and it detracts say 30mpg (extreme), then you 've still got a car with ridiculous gas mileage.  The tank wouldn't even have to be that big to get the same mileage range out of it as regular cars.

--Side note-- on the issue of safety vs. gas, that's debateble.  On one hand, H₂ has a very low density, so it may float away before it can catch fire, whereas gasoline vapors are more dense and tend to hang around longer.  Any source of ignition would light both of them, but there is a good chance with the hydrogen that you'd have a teriffic explosion, whereas gas explosions look like those in the movies.  Six of one, half-dozen of the other in my opinion.

4. Transporting it may not be as much of a problem as you think.  Natural gas is a NFPA Flammability Class 4 material, and as such, containers that hold it, and more specifically, pipelines that carry it, have to meet specific standards.  Hydrogen is also a Class 4.  This means that the stuff that contains these gasses must be machined to the same standards.  Hydrogen presents a few more specific problems, but for the most part, with some valve changing, we could most likely use our existing natural gas pipeline to transport the hydrogen about the country.  Of course, we'd have to switch from methane to hydrogen, which could pose a few more safety hazards in the home.  It's debatable, though, because you wouldn't have hydrogen explosions from buildups of hydrogen like you do with methane--the hydrogen is so light, it would diffuse right out of the house.

5. Solar power, getting our H2 from Iceland, wind power, geothermal power, hydroelectric power, whatever we want, would be better than going to OPEC and more environmentally friendly, too.  We can crack seawater using this, producing H2 and Cl2.  The Cl2 we can send to 3rd world countries to sanitize their water, or use it ourselves.  There's a lot of cool uses for it, like making HCB for a color enhancing agent in fireworks.

6. There are problems with the engine designs right now--specifically, many engines absorb hydrogen and eventually explode.  However, there are prototype cars and trucks out there that have these engines made out of special ceramics and metals, and these perform well.  They're expensive now, but once you have it mass produced...

7. Want better performance?  Just add oxygen from a cylinder.  Don't even need that much.

8. Break down in the desert?  Need water?  Open the air-cooled trap on your exhaust line.

These are just off the top of my head, and I'm sure I'm going to get flamed and people will correct my figures, etc., but these are the concepts, the ideas.  I think it's viable and more sustaining than battery powered cars and fuel cell cars.

With currently available materials, the actual efficiency of a fuel cell is currently in the 30 % range, competitive with the internal combustion engines.  Theoretically, the potential of the fuel cell is higher.  As you mentioned, production is the biggest problem for hydrogen.  Producing enough hydrogen to propel a car 400 miles, relative to the direct distillation and combustion of gasoline in a light efficient car, generates almost the same amount of CO2 (if you are in the US, 80+ % of energy production is coal/gas/oil-based.  France would be a likely country to convert to hydrogen since it is reported that most consumer power is nuclear derived).  The biggest need is a solar-powered device or enzyme that electrolyzes water and enables hydrogen separation / storage without significant energy input  Any serious effort to change to a hydrogen economy prior to these developments falls into the "fools gold" category.  

The problem with using the Australian Desert to generate solar power is that large amounts of land are needed, and although uninhabited by people there are diverse and unique ecosytems there as well, which massive amounts of solar panels would surley destroy.  Personally, if folks want hydrogen, i really belive that currently our only choice is nuclear power to make it (or fossil fuels though that sorta defeats the purpose).  Despite the bad public rap nuclear very safe if you are not stupid, and pretty much the only choice anyway.

Cisco