To invent a new type of solar cell car, I can only conceive and draw the structure. Can I apply for a patent?

Yes, many patents are just an idea when applying, as long as you can clearly describe the technical scheme in the application documents so that the technicians in this field can implement it;

A patent only requires that the technical scheme can be realized, not that you have already realized it and made a physical object.

Judging from your description, your technical scheme should have been conceived completely and can be implemented by those skilled in the field. So you can apply for a patent for the technical scheme you are conceiving now.