[mvpel]

If it needs methane or natural gas or hydrogen as a fuel, how does it use sun beams as a fuel?

You electrolyze water with your solar panels then feed the hydrogen and oxygen into the fuel cell?

[dangerdoc]

The fuel cell is bidirectional. If you supply electricity it will work in reverse creating O2 and H2. Unless, there is another major solar break through and a hydrogen storage breakthrough, I don't see it as practical.