Imho, the main problem I see with hydrogen with cars, either fuel cell or combustion engine, the intrinsic overall long chain for production & distribution is a total waste has way too much energy losses along the entire process to make any environnemental & economical sense... You can install your own solar system & stationary battery at home if you want to be independant, with hydrogen you can't. Big ship, long distance plane maybe, I have no real knowledge into this.