Ahhh, Hydrogen - the fuel of misty-eyed dreamers!
Honda has dropped off a hydrogen fueling station outside a state garage near the capital, and they are demonstrating one or more cars that run on compressed hydrogen. I don't know if the design is an electric car with a fuel cell, or if it has an internal combustion engine DESIGNED to run on the stuff. But apparently the little cars are drivable.
Also, a past governor provided a grant to put demonstration hydrogen fuel cells for electric back-up at several state radio sites. I (my agency) was given three of them. One site has one 4.5 kW unit, the other has two in parallel to make 9 kW, since the second site has air conditioning. The small site has two "six-pack'" cabinets, for a total of twelve welding-sized tanks of hydrogen stored at 2300 psi. The tanks there will all be empty in 24 hours running at full tilt. The larger site has a tank cage for each generator, with 18 tanks in each cage, 36 tanks total. This site will run for 36 hours at full tilt (but will 'drop a dime' to the fuel truck after 18-24 hours). The only problem with radio site back-up is that the storms that take out commercial power (snow, ice, high winds) will probably make the roads impassible, too.
Since 9000 watts is about twelve horsepower, and using the fuel cell efficiency as a reference, I figure it would take roughly 1 welding-sized tank of compressed hydrogen per hour to run a 12 horsepower engine. That would be 15 tanks per hour for 180 horsepower.
The fuel cells are quieter than a generator (they do have a cooling blower & pump), and are cleaner AT THE SITE (only water as exhaust). I would probably consider putting one into a sensitive micro-environment, as long as I could get fuel trucks in. It might also be great to pump pre-compressed hydrogen into transit buses in smog-plagued urban cities. But in the macro-environment universe, hydrogen isn't "Green."
I'm not an expert, but I have read it takes 4 watts of electricity to separate the hydrogen from the water (and compress it?) for every watt the fuel cell returns. Add the diesel fuel for all the tank trucks running back and forth, and hydrogen is NOT a green fuel. I have heard it referred to as a 'storage medium' instead.
I have two radio sites that are off-road and off-grid. Each has a wind turbine, solar panels, plus a propane generator for bad-weather backup. We fly ten 100 lb. bottles up to each site before winter each year, whether they need it or not. Five bottles in parallel will run a 12 kW generator about 110-120 hours at part throttle. I figure if part throttle is 4.5 kw, I get about 22 hours of electricity per bottle of propane, compared to two hours per bottle of hydrogen. No way am I flying 110 bottles of gas per year to each site, considering the cost of helicopter operations (including Jet-A fuel), plus the salaries of two pilots and 6-8 'grunts' on the ground.
I have heard of some research (Clarkson College maybe?) being done concerning making hydrogen on-site for backup fuel cells while the electricity is on, but haven't read any reports.
All that said, a totally 'water powered' vehicle CAN work. You just have to think of it as a plug-in electric vehicle with a hydrogen battery. Range and speed will be severely limited. Forget the interstates. You could drive a bus about as fast as you could tow it with a souped-up lawnmower, if you wanted any range. If you park at campsites with free water & electricity, and have on-board tanks, hydrogen generator, and COMPRESSOR with you, you could conceivably store enough fuel over time to get maybe a hundred miles or so to the next plug-in. It would be a lifestyle choice. If you tried to store hydrogen using a genset, it would probably take more fuel to make the hydrogen needed to drive on than it would to just drive using the existing engine running on petroleum, WVO, propane or wood gas. You could never make enough electricity using solar (using today's technology) on a bus roof to both live on plus store hydrogen fuel.
I'm not saying you could simply plumb hydrogen gas to a gasoline, propane or diesel motor and expect it to work, either. I'm just saying you CAN separate hydrogen from water by PUTTING ENERGY FROM ANOTHER SOURCE INTO IT, and Honda at least can somehow run a vehicle on compressed hydrogen. Two liters per minute uncompressed isn't enough. But I do love thinking 'outside the box.' Efficiencies improve. I've heard today's pocket cell phones have more computing power in them than the entire space capsules that went to the moon. "What will they think of next?"