Along with cars and planes, hydrogen power has the potential to make boat travel cleaner and quieter than possible with internal combustion power. The team at Sandia National Laboratories believes San Francisco could be the perfect place to set hydrogen boat travel afloat, arguing a fuel cell commuter ferry would be feasible running in the Bay Area.

The study was based on the same requirements placed on diesel-powered San Francisco Bay ferries. It would be expected to carry 150 passengers on four round trips of 50 mi (80 km) every day, and need to be able to maintain a speed of 35 knots (39 mph/63 kmh) for 65 percent of its time on the move. Refueling would need to happen in the middle of the day, between the morning and evening peak-hour rushes.

To meet the top speed requirement, the team designing the catamaran gave it a longer than average hull, and stored the hydrogen in a fully enclosed section of the main deck to make sure it remains properly separated from passengers at all times.

In addition to performing as well as a diesel ferry, the research team says using hydrogen power delivers a smoother, quieter ride, and reduces the risk of messy diesel spills on the water. Because the fuel cells provide power to electric motors, the boat can also be expected to respond more quickly to inputs, making it more maneuverable than a diesel.

"This kind of boat has never been built before," says mechanical engineer Curt Leffers, the project manager for Elliott Bay Design Group. "Hydrogen fuel cells are heavier than diesel engines for a given power output, so achieving the right power-to-weight ratio for the vessel was tricky."

So, what's stopping the SF-BREEZE from being commercially viable? Well, the first hitch is cost - according to the researchers, a hydrogen ferry is likely to be around three times as expensive to buy as a conventional diesel boat, and running costs are expected to be significantly higher than they are for diesels as well.

That means - for now at least - we're not likely to see a hydrogen ferry running laps of the San Francisco bay, but at least the idea is being discussed.