hydrogen power would be an option, as for availability, I can walk into nearly any welding supply shop in the country and get a bottle, or a bottle filled. Its not as convenient as a corner gas station, but its close. Propane is an option as well. At my old school district, we had propane fueled buses, and the drivers filled them up as with a gas or diesel bus. Screw on fitting, pull the handle, and 60 gallons goes into the tank in about 3-5 minutes..... As for a reserve, think like a scuba diver and have a pony sized bottle for "backup"... 2 minutes with a crescent wrench, and you are back running. Sure you should plan to be able to go out and back with a safe reserve, but the law of "schitt happens" exists for a reason. Fuel contamination could kill your main supply. Batteries lose capacity as they age. A viable backup plan is almost always in order.... Mine on my boat is a small trolling motor... if the main engine drops dead, I can at least get to shore (or a hell of a lot closer to help) with the little bugger.... at least until the batteries die, then I am on to "plan C" which is likely swimming.....