Are hydrogen powered vehicles the greenest way to go

No-- hydrogen has its own issues-- like:

According to John Heywood, director of MIT is Sloan Automotive Lab, ''If the hydrogen does not come from renewable sources, then it is simply not worth doing, environmentally or economically.''

and because of these:
http://www-formal.stanford.edu/jmc/progress/hydrogen.html

and because:
''If we do not generate hydrogen in an environmentally responsible way, we'd be going five steps backward, rather than forward,'' said Scott Samuelsen, director of the National Fuel Cell Research Center at UC Irvine, where he is also an engineering professor.

i dont understand why soemone cannot make a solar powerd car.they have solar everything but not one solar powerd car

H2 powered vehicles still have issues, but ''greenness'' in comparison to fossil fuels is one of the smallest.

1. H2 is most commonly created by the electrolysis of water. So the cycle is water + energy = 2H2 + O2. Combustion of H2 releases the energy, recombines the 2H2 + O2 & produces water.

2. As has been already stated by other responders, the source of the H2 (methane/natural gas, or fossil fuelled electrical plants) affects the relative ''greenness'' of the H2, i.e. if u use fossil fuels to create H2 there is not a net benefit.

3. There is not currently a good method of storage or distribution for H2 as a transportation fuel, storage technology is currently under development. (see link for more information)

4. The favored technology for using H2 is to produce electricity in fuel cells. Fuel cells have 2 technological problems: 1) Platinum is the catalyst, there is not enough platinum on the planet to meet all the transportation needs with fuel cells [iron based catalysts r being studied], & 2) fuel cells r bloody HEAVY. A fuel cell to provide the same horsepower to a vehicle that a current internal combustion engine produces would be almost 100X the weight. Fuel cells might have current applications for rail & heavy machinery, but not so much for road or air transport where weight is an issue, unless the technology improves.

5. Batteries have little or no green advantage over fuel cells, it all comes down to the source of the energy. If fossil fuels create the electricity to charge the batteries it still produces CO2. The batteries r heavy as well, the quantity of energy u can reasonably carry is small & the recharge times r a lot slower than refilling a tank of Hydrogen gas. The ENV motorcycle (2nd link) is fuel cell powered & has a top speed of 50 mph & a range of 100 miles on a tank of H2 about the size of a water bottle.

This does not exclude batteries from being part of the final process. Fuel cells create electricity, regenerative braking creates electricity. To avoid energy conversion efficiency losses it is better to store any unused or recaptured energy in a battery than to try to create H2 out of it.

Hydrogen vehicles do release vapor, but the total amount is minuscule. The problem with hydrogen vehicles right now is the process to create the hydrogen. At present that process uses oil.

Once they get that figured out hydrogen vehicles will be a very good idea.

One thing that people always seem to forget about water vapor is that the capacity of the atmosphere to hold water vapor is dependent on temperature (the hotter it is the more water vapor it can hold). If u get too much water vapor in the atmosphere it rains, sort of a self regulating system (alot like the global temperature.self regulating.even though the greenies do not want to admit that).

It is not as it would be like riding a BOMB!!!

Bubba has put his finger on it.
There is no ecological problem with the production of water vapor, as Bubba tells us. The single reality in the way of hydrogen powered vehicles is the indisputable fact that the production of hydrogen uses vast amounts of power, emits polution, & is prohibitively expensive.
Precisely the reason that we need a ''Manhaten Project'' for alternative fuels. Bring together the best & brightest to work on the applied mechanics & theoretical chemistry of hydrogen production, & we can make the gasoline engine an antiquarian oddity.

The traditional fuels cannot be replaced by alternative sources until there is build out of a distribution system. All of the Green plans are not objectionable as an academic exercise. Where are the service stations for a nationwide launch of hydrogen, fuel cell, etc.?

They're not the greenest way to go, but not for the reason u think. Water vapor is a feedback, not a global warming forcing. For an explanation, see Myth #9 here:

http://greenhome.huddler.com/wiki/global-warming-myths

We could emit as much water vapor as we wanted & the planet would not warm at all. It would rain more though.

However, hydrogen is not the greenest way to go because currently we get 96% of our hydrogen from fossil fuels. Electric vehicles r the greenest way to go. See the links below for further details.

Your right that water vapor is another greenhouse gas. It is the largest greenhouse gas in the atmosphere by far (about 0.03 % CO2 vs 100% RH before the water vapor rains out). The actual percentage of water vapor in the air changes constantly, but it is very large relative to CO2.

Water vapor however is NOT very effective at absorbing long wave radiation compared to CO2. It tends to moderate climate instead of making it consistently warmer like CO2 does. It is an important feedback mechanism & will influence precipitation patterns.

The moderating effect is why the climate in New Orleans is warmer in the winter (rarely below freezing) than deserts at the same latitude. New Orleans is also cooler than places like Death Valley in the summer, for example, because of water vapor. New Orleans gets 99 or 100 degrees in the summer (not uncommon) & the water vapor is so great, if any convection is happening at all, the cooling as hot, moist air rises triggers a thunderstorm & cools things down. The humidity is stifling for people & makes it feel hotter because sweat is not evaporating, but the air temperature is actually cooler than Death Valley.

Death Valley, by contrast gets in the triple digits often & as high as the 110-115 degrees F. Plants grow great in high heat & humidity of New Orleans, but not so great in the high heat & low humidity of Death Valley.

Reducing CO2 would do more to help reduce global warming & climate change than reducing water vapor, since most of the Earth is covered with water anyway. And if we make hydrogen out of water, when we burn it, we just re-make the water. The system is sustainable (at least as I have conceptualized it) with no disruption to the hydrological cycle.

Now producing the hydrogen from water without making more greenhouse gases - that is energy intensive & may be a problem.

Yes, yes it is true. Everything is a green house gas. You breath in green house gas. You pass green house gases from every opening. Cars make green house gas. Cows make green house gas. Buildings, out gas. Oceans out gas. Bogs make green house gas.

Trees pass gas, but that is good gas.
When trees die they make gas, but that is bad gas.

We make gas, we generate gas when we burn gas.
Gas bad, man bad, must stop gas. Yes, master, what me do now master?

actually your correct water vapor is a greenhouse gas. And is much more present in our atmosphere than co2. Co2 makes up .03 percent of our atmosphere. Water vapor however makes up 70%. So when people tell you that co2 is even making a difference you can laugh in their face

You're right hydrogen power is a really bad idea. Who wants to pay twice as much for a car with half the range and has half as much power and costs 4 times as much to run.

Gasoline would have to get really expensive before that idea catches on.