Solar panels efficiency increases every year, yet their power to price ratio & power to surface ratio are still insufficient for ebikes. Nevertheless…
Featured image courtesy of Elektrek
Mounting photovoltaic panels on ebikes: surface to power ratio is an issue
Solar photovoltaic panels don’t produce much electric energy per square meter of surface. We can roughly reckon some 260 Wh per square meter, with a flexible solar panel only 3 mm thick, for top quality solar panels. Still, there’s no way to set even a flexible solar panel with one square meter of surface on any ebike. Exploiting luggage racks, we guess you could install a total of half square meter of solar panels on your ebike. That would bring their power output, i.e. the electric energy they can produce, to more or less 140 Wh. Just consider that the declared power output of solar photovoltaic panels always refers to peak power, the maximum electricity they can produce when they can get the most sun energy, that is in a sunny day around noon. In these conditions, for instance in Spain, solar panels with a 100W output would add some 85W per hour to your battery. Indeed, not all electricity produced by the panels would be stored by the battery, since the transmission via the charger involves a dispersion. The same happens when you charge at home with a sector plug. Just look at the picture above, from Elektrek, two photovoltaic panels with a surface of about 0.3 m² and a combined output of 100Wh were mounted on that ebike.
You wouldn’t like to ride a bike like that, would you? Perhaps you would feel more at ease with the bike pictured below:
Ebike with solar panel mounted on the canopy. Artisanal but worth considering.
Nevertheless, an ebike battery, say a 250 Wh range extender, could be charged from 20% to 80% in just a couple hours. We explained here how batteries should ideally be charged from 20% to 80%, and the last 20% takes much longer. Not bad, especially for long trips when you could charge while riding.
Citkar e-cargo delivery bike
It’s better for cargo ebikes and e-trikes
In order to carry heavy and bulky payloads, e-cargoes and e-trikes, and cargo e-trikes, like the Citkar, present large surfaces where solar panels could be easily installed, be they removable or fixed. Photovoltaic energy would be particularly useful for day long delivery trips, allowing charging on the go of the main or sole battery, although only for certain batteries. An additional battery or a range extender can always be charged on the go, though.
Cube Trike Cargo Hybrid e-cargo bike
Solar panels are still kind of expensive
Regarding the price of photovoltaic panels, we can approximatively reckon 1,4 euro per watt of power, a 140W photovoltaic solar panel costing around €200. Add to that more or less the same sum for a solar panels control. That can be paid for, if you are to use a solar panel to extend the range of an e-cargo bike for deliveries, or even enjoy longer trips in the nature with your ebike. Anyway, their price per Watt power keeps decreasing year after year.
Under what conditions is a full charge possible?
If your ebike is exposed to sunrays all day long, because it’s parked in a sunny place or because you are riding in the sun, eight hours would be enough to fully charge a 500Wh battery, with 0.3 m² of solar panels.
Bergamont E-Cargoville LJ Expert e-cargo bike for the 2023 season
How to mount solar panels on your ebike
You should mount them on the luggage racks if you’ve got a normal ebike. If you’ve got any e-trike, or an e-cargo bike, you could set them on the roof or on the cargo container, using rigid fixed panels on the former and flexible removal ones on the latter.
You will need some solar panels specifically made for ebikes, like the ones for sale by OZO, best quality SunPower panels that should be coupled with a solar charge controller just like those you can buy at Genasun‘s. Count around €200 for each one of them.
Solar powered ebikes charging stations
Sometimes it’s difficult or too expensive connecting an ebike charging station to the grid. Charging stations powered by photovoltaic panels and storage batteries can be a good solution, especially if the surplus energy can be sold to the grid, for instance in off peak season. Even hotels could benefit from such solutions.
Flexible solar panel OZO, 140W, priced at 199 €
A trekker’s experience: flexible panels are much lighter
On the Facebook Ebike Touring Group, Chris Barker, an experienced ebike trekker, published the photo below, with this comment: “That’s the old 100 watt panel. It was a rigid one but heavy as hell. I just upgraded to a 150 watt flexible. The 100 watt panel works great but I wanted a little more power. Now I can charge at 2amps no problem and that’s my preferred rate. Also the flex panel is 13 pounds lighter.”
Chris Barker’s solar ebike-trailer
We thank Chris for letting us publish it.
