Designing the New Solar Car

Aerodynamics, Featured, General, Structures / Monday, November 28th, 2022

For nearly two years, the RAHS solar car team has had their eyes on designing a new solar car to compete in the 2023 National Solar Car Challenge. As we have hinted towards in the past, an aerodynamic design has been in the works for some time now. With a new year, the team has the opportunity to follow through with the idea and build the new 2023 RAHS solar car.

The process began in late 2021 when we began experimenting with new designs. In the past, we have built cars with wider track widths (eg. catamaran and side pod style cars) that run up against the 1.8-meter width limit set in the rules. We made this choice because they were incredibly stable and their surfaces were smooth which helped with the ease of manufacturing. Unfortunately, the wider track width often resulted in an increased frontal area, thus inducing more aerodynamic drag. To remedy this issue, the team took a very aggressive approach.

Many of the collegiate and private teams have opted to use a single-body car in the recent 2021 Moroccan Solar Car Challenge. These are sleeker and punch through the air with ease, leading to an increase in aerodynamic efficiency. There were, however, some drawbacks to this design. The single-body approach reduces the amount of area on top of the car, thus reducing the amount of space reserved for solar panels. Due to this loss, all other components of the car need to be streamlined to account for the known reduction in solar area, and therefore, a significant decrease in available power throughout the race.

After some initial hypothesizing, the aerodynamic team designed various preliminary single-body models to understand the flow of air over this new aero shell. Through a few iterations of simulation through our new software SolidWorks Flow, the team was able to see how profound the changes were. This iterative design approach resulted in a substantial reduction in drag (nearly 65%). 

Final Aerodynamic Model for the 2023 RAHS Solar Car

The team has committed to the single-body car in an attempt to reduce the aerodynamic drag and adhere to the strict collegiate-level rules. To give the challenge a new spark, we have made it our goal to build a car capable of racing in both our current high school Solar Car Challenge and the Bridgestone World Solar Car Challenge. With these new criteria, the team has been forced to look at the competition through a completely new lens.

As opposed to our current challenge which allows for up to nine square meters, the World Solar Car Challenge enforces a much stricter set of rules. The rules dictate that the solar area of a car must remain under four square meters which actually plays right into the hands of the single-body car.

Solar Panel Layout for the 2023 RAHS Solar Car

After designing and refining nearly forty aerodynamic simulations, the team finally developed the final model. It features a lower tail with a nearly flat bottom, allowing for a balance between low drag and ease of manufacturability. Using two different airfoil shapes for the top and bottom formers, the car induces an almost completely laminar flow trajectory across all surfaces. Due to the design of the car, a few fundamental design changes had to be made. The first major change would be the material from which the safety cell is built. Since this aeroshell will be formed from a layup of pre-infused carbon fiber, a composite interior reduces the complexity of bonding steel to composites. As a result, the interior frame will be built out of a high-strength carbon sandwich panel, which the team has never done before.

Preliminary Structural Designs for the 2023 RAHS Solar Car

The upcoming Solar Car Challenge poses various new challenges; as a result, the team has a lot to do ahead. From the manufacturing of our mold, all the way to the development of our frame, this year’s car is an ambitious goal. While we work hard in the shop at RAHS, we are always motivated by the possibility of racing our dream car across America or the Australian Outback!

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