This week, Kevin van Hese and Elias Wawoe from the Brunel Solar Team unveiled its latest solar car, Nuna 13, at the Louwman Museum in The Hague.
The car marks the team’s 25th anniversary and features innovations such as an extendable fin for extra speed, a lighter chassis and an ironless engine. In August, the team will participate in the Bridgestone World Solar Challenge in Australia for the twelfth time.
Several technical innovations on Nuna 13 should make the difference on the 3,000-kilometre long course through the Australian outback. The most striking is the extendable and rotatable fin: an aerodynamic innovation that converts crosswind into extra propulsion. “Just like with an aircraft wing, a pressure difference is created on the fin during crosswind, which provides a pushing force forward,” explains Kevin van Hese, electrical engineer at the Brunel Solar Team. “As a result, we use less solar energy – and that is important, because new rules mean we are racing with a battery that is three times smaller than last year. And because the race is taking place two months earlier this year, we are racing in the Australian winter: the sun is lower, which means we have less solar income.”
Never before has a solar car been built with both an asymmetric catamaran design and a fin. To make the most of the fin, a wind tunnel test was needed. For the first time since 2011, the team tested with a full-scale car.
Combative
During the wind tunnel test on June 3 and 4 at the Volkswagen Group in Wolfsburg, the team gained valuable insights into the performance and stability of Nuna 13. The collaboration with the Volkswagen engineers was pleasant and professional. During the test, a remarkable discovery was made: with sufficient crosswind, the fin generates more thrust than there is air resistance, leaving a net propulsive force. This can be used to charge the battery.
At the end of one of the last sessions, however, things went wrong, Nuna 13 flipped over. The Brunel Solar Team had secured Nuna at several points and the solar car came loose at one of those points. Van Hese: “It was quite a shock, but we carry out these types of test trajectories to understand how the solar car behaves under different conditions. We have started repairing the damage and today we proudly present Nuna 13, which will soon participate in the solar race in Australia. Based on the test results, we have a lot of confidence in the car. And also confidence in the team, which has come through this ordeal well. We are better prepared than ever before.”
Lighter, faster, smarter
Progress has also been made at the material level: this year, the team applied the pre-preg method for the first time. Previously, carbon was manually coated with resin, which hardens quickly. Now, the resin is already in the carbon, so the material only hardens when heated. This allowed team members to repeatedly deform the carbon and work more precisely. The result: a lighter chassis, less chance of defects and a tighter finish. In addition, Nuna 13 features an efficient ironless motor, an improved steering system with less energy loss and silicon solar cells that are around 30 percent more efficient than standard solar panels.
25 years of solar innovation
Where solar energy was once a promise, it is now a proven engine for progress. This anniversary edition of Nuna reflects 25 years of courage, knowledge and innovation and the ambition to show the Netherlands as a leader in the energy transition. “We are not just building a car, we are building the future of mobility,” says Elias Wawoe, team leader at the Brunel Solar Team. “With this car we bring together 25 years of knowledge, ambition and innovation. Since 2001 we have participated in the world championship solar racing in Australia every other year and of the eleven times we have participated, we have won seven times. Without the knowledge of our predecessors, we would never have come this far. This year we are going all out for the eighth world title.”
Dutch pride, inside and out
The exterior of Nuna 13 is a mobile work of art full of references to the Netherlands and the four elements: sun, wind, water and earth. In a Van Gogh-like style, a lion, a mill, seven golden tulips and clouds are incorporated into the wrap, symbols of strength, innovation and craftsmanship. Wawoe: “The seven golden tulips represent the seven world titles that we have already brought back to Delft. The bodywork was built by a Frisian boat builder, the fin refers to our sailing tradition and the technology to 25 years of Delft innovation. The car is truly a tribute to where we come from.”
Photo: Hans-Peter van Velthoven