Meet Silvretta, our second solar car. With 50% more solar panel surface than Aletsch, 10% less aerodynamic drag, and a fully redesigned drivetrain reaching up to 96% peak efficiency, Silvretta is ready to take on the Australian Outback in the Bridgestone World Solar Challenge.
Inspired by the stunning Swiss glacier it’s named after, Silvretta carves its own path forward.
To ensure low drag, we created our special aeroshell and canopy around the chassis. Most of the car is built from carbon fiber (CFRP) for rigidity while other parts are build from E-glass (GFRP) where signal transparency is needed. This ensures that GPS and telemetry can work without interference. The transparent components, such as the windshield and light covers, were crafted using advanced forming techniques that ensure both optical clarity and aerodynamic integration.
Our drivetrain consists of a custom-designed motor and an inverter that convert the electrical power from the solar cells into mechanical torque.
The direct-drive motor is optimized for maximum efficiency, achieving a theoretical peak efficiency of up to 96%. This is achieved through motor geometry refined via simulations and optimized rotor/stator design.
The inverter converts solar and battery DC power into AC the motor uses. It also controls the car’s acceleration based on input.
The suspension uses a double wishbone suspension system in the front and a trailing arm for the rear. Most parts are machined. A notable exception is the wheel hub that was optimized for weight and strength. Its geometry was generated through simulation and produced via Powder Bed Fusion additive manufacturing. This reduced weight by about 50%.
The battery uses 43 Lithium Iron Phosphate cells in series and is split into compartments for packs and control electronics. Batteries can be quite dangerous if they were to overheat under the hot Australian sun. Thus, Silvretta has six temperature sensors distributed across the packs, enabling continuous thermal monitoring to detect early overheating issues. A custom converter supplies 12 V to the low-voltage system. The 7.5 kg battery box is built from carbon sandwich panels with glassfibre insulation.
Aerodynamic design is key to efficiency, especially in Australia, where it accounts for about 75% of total energy loss. Reducing drag and avoiding lift or downforce were top priorities, along with maintaining stability in changing wind conditions. We focused on minimizing frontal area and optimizing airflow over the canopy and rear. The orientation of the solar cells was also adjusted to improve performance. Over 100 design iterations and 25,000 hours of simulation went into shaping the final outer shell. We reduced aerodynamic losses by about 10% compared to our first car, Aletsch, even with 50% more solar surface.
