The race of the sun, The Bridgestone World Solar Challenge and the Kogakuin University Solar Team

Teijin’s new technologies that support the challenge of solar car racing.

A streamlined white vehicle is running on a harsh desert road. In the stormy winds, the young driver grips the steering wheel even more tightly. The young driver is aiming to reach the finish line for the team, for everyone who has supported the driver, and for the future of mobility. One of the world’s most prestigious solar car races, the Bridgestone World Solar Challenge, is held once every two years. Its entrants drive for five days, about 3,000 km across the Australian continent from north to south.

A solar car race is a competition for electric vehicles powered by the energy generated by solar cells mounted on the surface of the vehicle, and the races are held worldwide including in the United States, Japan, Europe and Africa. In the case of the Bridgestone World Solar Challenge, the area of the cars of the solar panels is limited to about 2.64 m2 to 4 m2, depending on the material used. The one-seater racing vehicle is 5 m or less in length, 2.2 m or less in width, and 1.6 m or less in height, and is driven by two or more drivers taking turns. In addition, the weight limit of the driver and the running time of each section are also regulated.

Solar car racing vehicles require several important factors to be considered including air resistance, weight reduction, rigidity of the vehicle body making it strong enough to secure running stability, and power generation performance determined by the installation form of the solar cells. It is critical to enable long running range while minimizing energy consumption. Also, strategic vehicle management is needed to enable running for a long time efficiently even in inconsistent power generation conditions where the sunshine conditions change from moment to moment.

The Bridgestone World Solar Challenge has been held since 1987, and is the oldest race among existing solar car races. Also, it boasts the largest number of participating countries. The Kogakuin University Solar Team has been participating in the Bridgestone World Solar Challenge since 2013. The race is divided into three classes. The Challenger class, in which the Kogakuin University Solar Team has participated, is a speed race where participants compete to find the fastest solar car in the world. In the 2019 race, the Kogakuin University Solar Team placed fifth. In addition, they have achieved excellent results in races in Japan. In August 2021, they participated in the World Green Challenge (WGC) solar car race held in Ogata Village, Akita Prefecture, and came second.

Vehicles participating in Bridgestone World Solar Challenge since 2013

Unit 1 “KGUS09”

Unit 2 “Practice”

Unit 3 “OWL”

Unit 4 “Wing”

Unit 5 “Eagle”

As is the case with the challenge facing these young student engineers, companies that support them have been continually developing new technologies. Since the Kogakuin University Solar Team first competed in the Bridgestone World Solar Challenge in 2013, Teijin Group has supported them by providing lightweight, high-strength vehicle body materials, and materials and products that improve the comfort of team members.

For example, the world’s top class solar car racing vehicles require improved aerodynamic performance, so it is necessary to give the vehicle body complicated 3D-curved surfaces, fine edge shapes, and the like. By adopting an ultra-lightweight woven fabric prepreg (forming thickness 0.06 mm) made of Tenax carbon fiber manufactured by Teijin, the laminating process has been easier due to its flexibility, and helped to make more complex shapes, which was difficult with conventional prepreg. This not only reduces the vehicle weight, but also realizes a vehicle body with low air resistance.

In addition, the vehicle windows using highly impact-resistant and lightweight Panlite polycarbonate resin contribute to reducing the vehicle body weight and improving driver safety. Also, the prepreg made of the para-aramid fiber Technora, which is eight times stronger and one-fifth lighter than steel, has realized a weight reduction and durability improvement of the tire covers.

For the 2019 race, Teijin cooperated in supporting the development of high-efficiency solar power generation. By using a solar cell for artificial satellites (GaAs triple junction) and flattening the panel surface, a configuration that prioritizes power generation was realized.

The technologies and know-how cultivated in this solar car racing vehicle development are wide-ranging, such as improving the efficiency of solar power generation, power storage performance, and designing and forming lightweight vehicle bodies. These contribute to the optimization of energy consumption, and are indispensable for the realization of a sustainable society.

The key to realization of a sustainable society is the spread of renewable energy that does not emit carbon dioxide (CO₂). Along with companies’ tireless pursuit of technological innovation, the passion of young student engineers in solar car racing will open the door to the future.