There is a long history of oil interests ensuring electric vehicles don't go anywhere. And batteries are always a problem.
I wondered where my tin hat was.
The last time I looked at this, the power to weight ratio for stored energy electric vehicles was not great. The limitations on capacity and charging time are a problem.
It boils down to energy conversion. In general every time you convert energy from one form to another there are losses. A solar powered car that does not store energy for later use is much more efficient than a car that converts solar, to stored, to motion. A combination is better is you can store any extra power when it is not needed for use when it is. Energy recovery baking systems try to return the energy needed to accelerate the vehicle back into stored energy, trading kinetic for potential and back again ... but there are losses. You never get it all back. It's like using an inverter to power the battery charger that charges the inverter battery.
Not having to cart around stored power is a good thing ... a sailboat is more efficient than a wind generator charging a battery that runs an electric motor. The wind energy is converted directly into motion.
I don't know how heavy the storage system is for a hydrogen fuel system with the same number of BTU stored as 50 liters of fossil fuel, but I suspect it is higher. Power is needed to cart around the fuel, lighter is better.
They have been experimenting with hydrogen fuel cells in the transit buses in Vancouver for a number of years. The technology is developing, but it will be a long time before you see a fuel cell powered production vehicle.
I'm not anti-new technology fuels and transport systems, I just haven't seen one yet that makes me sit back and say, "Wow, I have to get me one of those".
If you add a requirement for infinitely sustainable to the equation, then fossil fuel is a bad choice. I'm not going to live forever, so what we need in 100-500 years is of little concern to me.
Of the items that have been posted in this thread, the Solar powered hydrogen generating system looks pretty good. It would seem that once the cell is built it can produce hydrogen as long as the sun shines ... do the titanium oxide units last forever or do they have to be replaced weekly? How big/heavy is a unit that can generate enough hydrogen to power a vehicle?
If you are looking at solar power and water ... how about a solar fired steam engine?
This stuff is all good, you might be surprised at how much energy research is funded by oil companies. They are interested in the bottom line and they know oil won't keep them rich forever. They have become energy companies (the smart ones) and they want to be the first to have a viable replacement for fossil fuel ... that way the money keeps going into their pockets after people get tired of fighting wars for oil.