Solar car aero shells are designed for zero lift, not to press the car into the ground or take off. This is the minimum energy usage. It's true that you could

Solar car aero shells are designed for zero lift, not to press the car into the ground or take off. This is the minimum energy usage. It's true that you could reduce your rolling resistance by making a car with positive aerodynamic lift, but doing so would make you dissipate more energy in the air than you would save.