but people use it all the time. The "dangers" of hydrogen fuel are over rated.

Still, it'll be very difficult and expensive to move to a hydrogen based economy. There are several obstacles that must be overcome first.

1. We need an economical method for producing lots of hydrogen. Electrolysis of water seems a natural but it requires a lot of energy. The water may be free but the energy isn't. From what I've read, the most economical method for generating hydrogen is to split it from natural gas. Natural gas isn't free, either.

2. We need an infrastructure to deliver the hydrogen all the way from the production plants all the way to the corner service station. That means new pipelines, new storage facilities, new tankers, new pumps, etc. This step alone will cost untold billions of dollars.

3. We need a safe and practical storage system for vehicles. Pressurized gaseous hydrogen would require large and heavy tanks to hold enough gas to go anywhere. Liquid hydrogen would require ruggen and crash resistant Dewars. It would also need training to teach people how to work with pressurized cyrogenic liquids. Perhaps the best technology is to either bind the hydrogen lightly to a metal such as lithium to form a metallic hydride or to use some form of carbon nanotube. The metallic hydride approach was tested in Germany about 20 years ago and seems to work well. The nanotube approach is still in the research labs.

Personally, I think the way to go is along the lines of what the Ballard Corp of Canada is doing. They've made fuel cells that can extract the hydrogen directly from natural gas, alcohol, or gasoline. This eliminates the need to build new production plants (unless you go the alcohol route), infrastructure, and vehicle storage systems. Today, the fuel cells are still too expensive for auto use but they're making small units for home use. It's a lot harder to make a unit powerful enough (100 kilowatts or more) and small enough for cars than to make a home power unit. If the research pans out, these fuel cells might be affordable within 3-10 years.