How to make a solar powdered toy car?

For a science projects(sort of like the science fair, except we have to make it 'reuse' themed, sort of) I want to make a solar powered toy car. What can I use to make this, approximately how much will it cost, and how difficult will it be? Has anyone done things before, for school or something?How to make a solar powdered toy car?i am a technology education teacher, there are countless websites that offer everything from parts to complete kits, most are inexpensive, just do a little research and you will for sure find what you are looking for.