As little air resistance as a coke can

During the presentation of their newest solar car, Solar Team Twente already expressed their expectations: solar car RED E would have a similar air resistance as that of a coke can. The wind tunnel results have confirmed this expectation, also confirming that the air resistance is even lower than the previous editions’ RED Shift solar car. This is largely due to the compact shape of the solar car. By choosing gallium arsenide solar cells, mainly used in space travel, it became possible to decrease the size of the car. RED E is now the smallest solar car of Solar Team Twente ever, positively influencing its aerodynamic properties.

Students from the Saxion University of Applied Sciences and the University of Twente are testing the car’s air resistance experienced in a wind tunnel. Mariska Bos explains how this testing method works: “We place the car on a scale that can measure forces very precisely in all directions. We then test the car at different wind speeds and conditions. We are interested in the forces that affect the car because, with them, we can predict how much energy it will take to drive at certain speeds during the Bridgestone World Solar Challenge in Australia. In addition to the RED E solar car, RED Shift was tested recently under the same conditions. This made it easier to compare the results. 

Solar car RED E is Solar Team Twente’s smallest solar car ever. Because of this size, it fits in the wind tunnel. RED Shift was the first car that fitted in a wind tunnel, making the test results much more accurate. The alternative is a scale model; however, they often lack details such as partial lines and small changes in shape due to imperfections from the production process. All such details influence the air resistance. “The measured aerodynamic properties in the wind tunnel are at the basis of a performance model of the car, which is essential for the racing strategy”, says Hans Maseland of the Royal Netherlands Aerospace Center (NLR). NLR supports the students in aerodynamic design and construction. “At all times during the design process, the aim must be that the aerodynamic characteristics of the new car must be at least 2% better than those of all competitors. If that is the case, there is a chance to win.”

The aerodynamics engineers spent more than 3000 hours on the design of the solar car, which corresponds to the number of kilometres the team will be driving in Australia during the Bridgestone World Solar Challenge. Mariska: “It was quite a complicated process at times because the possibilities are endless. There are so many things you can do that improve your design. Fortunately, we received much help from former team members and Hans Maseland from NLR. They helped us interpret results, checked that we did not forget anything and thought along to solve problems.”

On October 13, 2019, Solar Team Twente will be at the start of the Bridgestone World Solar Challenge, the most prestigious race for solar cars. With more than fifty other international participants, Solar Team Twente drives the solar car 3,000-kilometre right through the outback of Australia. The race has three different classes. Solar Team Twente is participating in the Challenger Class, the Formula 1 class for solar cars.

The Solar Team Twente consists of nineteen students from the Saxion University of Applied Sciences and the University of Twente. In addition to the students, Solar Team Twente consists of a strong network of over 150 innovative partners. Top sport is practised together, and so is the process of building the fastest solar car in the world. The Solar Team Twente believes in their motto “Challenge triggers innovation”. That is why the team participates in the Bridgestone World Solar Challenge with its solar car. The goal is two-fold: winning the race, but also generating attention for the possibilities of solar energy.