A labour of love for Danish solar-energy engineer Jesper Frausig, the Solarbike is an e-bike prototype that incorporates photovoltaic charging while still managing to look like, well, a normal bike.
“Most solar-powered bikes use off-the-shelf components that present design limitations,” says Frausig, who works for Gaia Solar, a solar-energy integration company based outside Copenhagen, where he lives. After studying various concepts, he opted to design the bike’s solar panels and battery into the wheels and central frame, respectively. This more integrated design reduces weight and aerodynamic drag, compared with other solar-equipped e-bikes.
“My initial observation is that normal [electric] bikes aren’t that exciting,” notes Frausig, who, like most Denmark residents, is an avid biker. (Government figures show that 90% percent of Danes own bikes and 36% of them pedal to work each day.) “They’re heavy and not built for young people.
“But if you design a lighter electric bike with a sporty design and that is powered by solar energy, suddenly it is something that people get excited about,” he says. “People stop me all the time and ask me what I’m riding.” With its battery pack, the Solarbike weighs only about 37lbs – a featherweight compared with typical e-bikes, which can top 70lbs.
Of course, as a solar engineer who works for a solar-energy company, Frausig knows a bit more about solar technology than the average DIY solar hacker. “This knowledge allowed me to slowly work toward a concept [bike] with custom-made components instead of off-the-shelf components,” he explains. “And I didn’t have to change the basic two-wheel design to make it a solar-powered bike.”
Frausig’s Solarbike features a 500-watt electric motor mounted by the pedal assembly. A tube-like container affixed to the main frame houses the lithium-ion battery pack, fed by disc-shaped arrays of solar panels mounted inside the wheel spokes. Each side of the solar panels is capable of collecting 25 peak watts of solar energy on a sunny day, though only when the bike is at rest – a limitation that, says Frausig, could change in future Solarbike iterations. Of course, because the sun can be occasionally uncooperative, the bike’s battery pack can be charged via a household outlet.
The top speed of the fixed-gear Solarbike is about 30mph under optimal conditions, and the bike’s range on a fully charged battery is about 40mi. The rider can set a desired speed on a handlebar-mounted control; sensors in the pedals then supply more or less electric assistance as needed. “The motor is always supplementing you,” he says.
One problem with integrating solar panels into the wheels is only one side can receive direct sunlight, though shadow-optimized technology helps a bit. As such, it can take five days to fully charge the battery, depending on sun conditions. However, that shouldn’t hamper an average bike rider in Denmark; national studies show that an average e-cycler rides for an hour a day and travels only about 6 miles, Frausig says.
Another problem with the Solarbike’s wheel-mounted solar arrays – similar to the disc wheels used by indoor track cyclists – is heightened sensitivity to crosswinds. It’s a problem that has Frausig considering ways to increase the density of the solar cells on the rear wheel and eliminate them completely from the front wheel. He’s also investigating better shadow-optimizing technology that could boost the bike’s ability to collect solar energy when it’s parked in shade.
Alas, those who yearn to park a Solarbike in a sunny spot in their yard may be waiting a while; despite some interest from cycle manufacturers, Frausig – who developed the bike on his own – doesn’t expect his creation to be available to consumers any time soon. “I’m anxious to hear what ideas people have,” he says. “I’m looking for funding to get to the next step, which is to improve the bike’s design and functionality.”
For a look at Jesper Frausig's Solarbike in action, check out the video below:
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