Solar powered cars are far more aerodynamic than your average street vehicle. Designing a good aerodynamic shell that is efficient, convenient, lightweight, and not featured in an Escher painting is an art form few have mastered. We consider frontal wind and side wind in order to reduce load on the motor and the steering system. The design gets machined into a car-sized block of foam and turned into a mold for the shells.
Mechanical systems in solar cars must be much more lightweight and efficient than those made for ordinary vehicles. Most of the parts are machined out of solid blocks of 7075-T6 aluminum, often by computer controlled mills. We have the freedom to make almost any geometry we want, giving the designer the opportunity to make very narrow suspensions that weigh very little and produce very little tire scrub. Other mechanical bits include all of the nice parts of the car that the driver touches – the steering wheel, handles, the door, etc.
Electrical systems control the storage and use of all the energy in the vehicle. They must use very little power for anything other than powering the motor. Traditionally our electronics have been very minimal – almost everything was purchased and we had little telemetry capability. These days, however, we build everything from our own pedal sensors and interface circuitry, to telemetry, maximum power point trackers, and battery protection system.
Nowadays we use a carbon fiber monocoque design instead of a steel chassis. We still use steel for the roll bar, but everything else is composites. Our latest change is to include a carbon fiber top shell as well as bottom shell. The body must be very lightweight and strong, yet be easy to attach things to internally. Composites are a fairly simple idea with an incredible amount of nuance and elbow grease to get in the way of a straightforward concept.
Optimizing our ability to gather and convert solar power is a primary concern of the team. Building an efficient vehicle is worth nothing if you don’t collect energy for it. We solder and encapsulate our own solar array. Just sourcing the materials to be able to pull off such a big job is no small feat in itself. Solar is a surprisingly finicky business, and it’s very easy to make highly suboptimal systems.
As we design the car, we model and simulate race performance as well as the performance of individual components, such as the solar array. This gives us a useful benchmark during testing and lets us tweak the design (for example, the pattern in which the cells are wired) and iterate on it much quicker than if we actually had to implement those changes. We also use simulations to try to find the best speed to drive at during each race.