He Built a Solar E-Bike That Needs No Charging and Took It Across the Alps

Shawn Ryan set out to answer a simple question: how far could an electric bicycle travel if sunlight were its only energy source? He built a solar-powered bike and took it into the Sun Trip Alpine event in France.

The event gives riders no support vehicles. They must find their own routes, camp, repair their bicycles and carefully calculate how much electricity they can use. Grid charging is prohibited for competitors who want to remain eligible for the solar-only category.

Ryan based his design on an Omnium cargo bicycle. He replaced the front cargo area with solar panels and added a 250-watt Tongsheng TSDZ2B mid-drive motor. Two 36-volt batteries stored electricity routed through an MPPT charge controller. During tests in Britain, the bicycle used about 6 to 7.5 watt-hours per kilometer. Its 200-watt solar system typically generated 70 to 100 watts, depending on the weather and the sun’s angle.

In the French Alps, the route included the 2,642-meter Col du Galibier and the Col de l’Iseran, at about 2,770 meters, considered the highest paved pass in the Alps. On the toughest day, Ryan covered 130 kilometers over mostly mountainous terrain. His controller recorded 985 watt-hours of usable solar power, or about 7.58 watt-hours per kilometer, while the bike averaged 21 to 22 kilometers per hour.

The biggest problem was not the climbs but the heat. Temperatures reached 41 degrees Celsius during a heat wave that also caused a wildfire near Lyon. The battery-management system became too hot and stopped accepting power from the panels. Ryan said the system had correctly protected the batteries, but he could not store all the electricity the panels produced. He eventually used grid power twice, totaling about 1 kilowatt-hour, which ended his eligibility for the solar-only class, although he continued the journey.