This could be an idea Get Toyota to put a bigger tank under a van that runs off pure water with one of them Hydrogen Hybird engines in it, then you gould kill to birds with one stone fuel to run your van, and water to clean your windows. The benifits no tank in van because its now under your van nice and safe. this is how to do ithttp://www.youtube.com/watch?v=94VHhQW6b4Q