Idea: Protection film in crystals that does not let the heat from solar radiation go through

There exist totally transparent panels that you can put in your crystals of the car.

There are different types. The cheapest ones filtrate around 65% of heat and the best one made out of graphene filtrates 80% of heat from solar radiation. They are totally transparent.

I think transparent solar protection films are key in this car because you can avoid a lot of heat inside the cabin.

Good luck with your project I follow you from Spain.