Cycle touring with an electric bike powered by a solar panel

Many times while riding to The Gambia, we discussed how we’d get back to England. A Citroen 2CV or an electric hub motor with solar panel driving the tandem were the two options most talked about. In the end, we did neither and flew instead.

I’ve recently bought a Heinzmann electric motor retrofit kit for what turned out to be one of my failed projects. However, the motor’s still with me and so is my curiosity. So, what about electric bikes for touring? Are they realistic over distance?

The motor on bikes is normally housed in either the front or rear wheel, but there are variations. The Watt Bott is an electrically assisted trailer whose battery is charged by a 20 watt solar panel. There’s little information to be found on this trailer online, but Kristin Rule, a cellist, tours with one, along with her Yuba Mundo cargo bike.

Cargo bikes seem to be a popular choice for electric assist cycle touring. As do recumbents, some with interesting panel mounting.

The Solar Tour bike and trailer is a project developed by two mates in a garage. What they wanted to design was, “a bike we could ride all day if we liked, perhaps as much as 200 miles entirely powered by the sun and our muscles. We wondered whether off-the-shelf commercial technology had advanced enough for two guys to build our 200-mile-per-day dream vehicle affordably and without a million dollars or a 50-person university team.

Find out if they were successful here

The guy at “my solar electric cargo bike” had to deprive his dog of its transport to make his electric assist long john.

But what about range? If you want to tour with a legal motor (250 watts in the UK for a two wheeler (Source), how big does your solar panel need to be to keep the battery charged for all day touring?

The Czech Solar Team took part in a 7300 km solar-powered ride from France to Kazakhstan in July 2013. The event is called the Sun Trip and is a race between 30 or so invited participants. The Czech team was powered by a Bionx 250 watt motor charged by a 500 watt panel measuring 250cm x 80cm.

This meant they had power all day, assuming half decent weather. But, despite the hefty panel, they didn’t win the race. That accolade went to Raf Van Hulle riding a Hase Pino tandem and pulling a home made trailer. He was probably the person we needed to talk to about our Pino conversion.

Raf is also the designer of the Solarwind trailer. There are 3 variations of this trailer, increasing in power as they increase in price, but all giving decent output.

The people at the Solar Bike Project point out that the weight of the vehicle will also be a determining factor in how much energy you need to put in versus the output you can expect in return.

“It was clear that putting solar panels on wheeled vehicles made more sense when applied to lighter vehicles. As the whole system scales down, the weight and therefore the power required decreases as the cube of the scaling factor, but the solar power decreases as the square. You win if the system gets smaller. Thus a vehicle half the size may have a quarter of the solar, but an eighth of the required power. Little toys about two inches long powered only by a small array of cells on top zip along quite nicely. Clearly, as the size is decreased, the ratio between operating power and solar panel power decreases, so you can charge for less time between runs, and even run all day without having to charge (when the ratio is 1). One can use this run/charge power ratio as a design goal. For instance, if you expect to charge four times as long as you run, then a 100W panel with a 400W motor is about right. Of course there are inefficiencies and variations in available sun that aren’t taken into account in this simple approach, but this has been the rule of thumb for the design of the cars from the beginning, and it seems to work.” (Source)

The AKT Solar Bike crossed Western Sahara to the Mauritanian border on a bike powered purely by a solar panel with no battery for storage to raise money for Oxfam. They used a 180 watt 24v motor powered by a 220 watt panel. Here’s the video…

And finally, here’s the trailer for the 2015 Sun Trip.

All in all, a great mix of transport solutions and another reason to chase the sun on your next cycle tour.





3 thoughts on “Cycle touring with an electric bike powered by a solar panel

  1. I’m fitting a Heinzmann Direct Power kit to our Pino right now. Just doing the fine tuning and tidying up at the moment. The Direct Power kit is the one that Hase fit themselves and it has regenerative braking which (might) give you an extra 15%. The older Heinzmann geared hub is famously reliable and has more torque but is noisy and no regen. (However our regen isn’t working yet, waiting for some advice from Heinzmann)
    First comments are that it is a gentle assist. Given the weight of a two-up tandem with luggage it’s not really powerful enough to make a huge difference but we are hoping it will be enough to compensate for one of us having limited strength due to arthritis. I guess an illegal (ie US-legal) higher power motor would give us more of a shove but that power has to come from somewhere. The Pino frame won’t fit Heinzmann’s 500 WattHour frame mount battery so we have the 400 WH rack-mounting one. It would be possible to pack a second battery but of course it’s all weight and on a tour that would mean two chargers and so it goes.
    For us the art will be to use it very judiciously when you need it, and see if we can husband the power over a long day ride (but not as long as you guys would aim for). That means only switching on for longer uphills and only using the lowest level of assist unless it’s getting tough (steep or late in the day). We’ll also be developing the art of dashing into every cafe or pub stop and getting the battery and charger plugged in ASAP to get the maximum topup during the break.
    I wonder what the trick was in that ‘Sun Trip’ race. The Pino looked a lighter setup than many others and consequently might make better use of the human power element, Raf looks like he contributes plenty of that, and is that front panel tilting to one side to take better advantage of the sun?
    Some of those designs just look very heavy and you wonder how much of the power gained from the sun is used to pull the solar kit along – diminishing marginal returns? That ‘Solar Power’ tandem looked very over-engineered by comparison with Raf’s Pino, they say the trailer was light but I reckon you could get rid of at least half of the tubing without compromising the structure. Probably a good idea to use an existing well-engineered bike like the Pino as it’s probably lighter, more reliable and easier to ride than a home-made job.
    We have a couple of long hilly rides coming up (one day in the Welsh borders and the 5-days on the Way of the Roses coast to coast route so after that we’ll be able to give a proper report.

  2. Ha, just noticed the clever part, Raf has a third panel packed on the Pino so whenever he pauses he has 50% more charging capacity, and his history indicates that he’s a real athlete.

  3. I’m with you on the weight issue of some of these solar machines. They look like overkill. I was amazed at the high tech nature of the Czech Team’s communications – Gone are the days of pulling alongside your riding partner for a chat, now it’s done via headphones and speakers.

    I’m a bit of a traditionalist when it comes to the bicycle – I love the simplicity of human power. These bikes are in another realm. That said, I do like the leftfield approach to cutting carbon and like most people, I find new ideas intriguing. Plus there’s an element of Wacky Races about the whole thing which made me smile.

    Regarding the Heinzmann, Janyis has a Velorbis trike from Denmark with a 250 watt Heinzmann fitted on the rear wheel. The trike weighs about 45kg unladen and will climb any hill in Brighton, with some leg work thrown in. Superb motor (not regenerative), which is what convinced me of their worth. Mine’s the 200 watt version and will be fitted to a standard bike initially, then perhaps a cargo bike if all goes well.

    I think charging at cafes when on tour is a good option. I imagine most cafes would be obliging on this score. Look forward to hearing how you get on with it.

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