A friend of mine said she had seen a website that sold plans for making car fuel cells that run on water that you can use to convert your car to a more fuel efficient one that runs part on gas and part on water. How do these fuel cells work? How do they turn water into energy? I am really curious about this, and would love to find out more information on the science behind this. Can anyone recommend a good website where I can go for more information? I want to see whether this would be feasible for me to do.