This guy needs to get smaller tanks. You couldnt possibly need all of that fuel just to get around. It would work out better to have refillable smaller tanks that only take you a smaller number of miles. You also have to worry about having steam inside of a small shell. I guess its a novel idea but producing steam on a bike seems like a waste to me. Plus the whole system has to be bulky otherwise you might get a rupture in the line and then... ouch hot ass steam right to your face!!! There will also be losses in the system so you would contantly have to add water and then have some form of cooling.... basically its a small power plant... and no matter what you do power plants can only be made so small.
Compessed air is not worth it. you cant possibly have a big enough container to hold enough pressure to get you going anywhere. Dont forget heat is energy and energy is power. Someone should make nuclear mopeds.