CalSol Zephyr – Berkeley’s First Win After 27 Years

CalSol's solar car Zephyr on the road, rolling shot

Not every solar race crosses a continent. The Formula Sun Grand Prix is a track race: for three days, college teams drive as many laps as their batteries and the sun allow. In July 2017, 18 teams met at the Circuit of the Americas in Austin, Texas, the Formula 1 track. The winner was Zephyr from CalSol, the solar car team of UC Berkeley.

Zephyr was already four years old and had raced since 2014. It completed 228 laps, about 775 miles (1,250 km), with zero penalties. It also set track records, including the most laps in a single day (82). After 27 years of racing, it was CalSol’s first victory.

Under the canopy: the driver sits low beneath a small bubble in the solar deck. Photo: Roxanne Makasdjian and Stephen McNally / Wikimedia Commons, CC BY 3.0

What does it feel like? Zephyr is very light and handles “mostly like a go-kart”. In tests it reached about 80 mph (130 km/h), but in races it usually cruises around 40 mph (65 km/h) after charging in the sun for four to five hours.

Victory at the 2017 Formula Sun Grand Prix in Austin, Texas. Photo: Roxanne Makasdjian and Stephen McNally / Wikimedia Commons, CC BY 3.0

CalSol has about 70 active members, split into operations, mechanical and electrical teams. They handle everything from sponsorship to carbon-fibre layups and battery management. As with every student solar team, the real product is people: engineers who learned to squeeze range out of every watt-hour. That is the same skill you need when you plan a LiFePO4 battery for your own solar trike.

Zephyr from the side: a flat solar deck on a slim chassis. Photo: Roxanne Makasdjian and Stephen McNally / Wikimedia Commons, CC BY 3.0

More American solar racers: Momentum, Maize & Blue and GM Sunraycer.

Technical data

Builder	CalSol, UC Berkeley (USA)
Raced	2014–2017
Class	Single-seat solar racer
Speed	~80 mph (130 km/h) tested, ~40 mph race cruising
Result	Formula Sun Grand Prix 2017 winner: 228 laps, ~775 miles, zero penalties
Records	Most laps in a day at the Circuit of the Americas (82)