We use fossil fuels like petrol or diesel in cars. The plants which lived millions of year ago have also used solar energy for photosynthesis to make food. Humans and animals grew up by taking these plants and fruits. Then this humans and animals are burned in earth after their death and became fossil fuels. Fuels are formed out of them. This fuel is being used in cars so the ultimate source of energy here is the solar energy itself. The vehicles connected with solar panels uses solar energy in the direct form.