Frequently Answered Questions
I’ve been asking questions about solar bikes since 2006 when I first got it into my head that I wanted to build one for myself. I’ve been answering questions about solar bikes since 2007 when I started riding around Oakland, California on my first solar ebike prototype. It’s mostly the same 10 questions over and over. Basically, my life is like the movie Groundhog Day.
An early version of this FAQ is still online. Most of it still applies today with the notable exception of my take on regenerative braking. In 2007, I wrote “regenerative braking would only add 2-3% to the battery’s range.” This was based on a my reading of a white paper which in turn was based on outdated assumptions. I now have an ebike with regenerative braking and it extends my range by 10% on flat roads and 20% or more in hilly terrain. I love being wrong about stuff like that. Regenerative braking is awesome.
The following is a sampler platter of the kinds of questions I’m asked while test riding my rig around Berkeley and Oakland. Looking back over my choices, I seem to have selected questions based more on how much I’ve had to think about the answer than on frequency of the question. It’s a challenge to craft one-size-fits-all answers when the person asking the questions might be a conspiracy theorist or a Nobel Laureate. We have a fair share of both types around here.
It’s electric… so you don’t have to pedal?
I get this one all the time so you might think that I’ve gotten good at answering it but nothing could be further from the truth. I find it’s an ongoing source of frustration. When linguists discuss the theoretical challenges of communicating with extraterrestrials, they point out that the basis of communication is a shared frame of reference. I believe this is my problem: the person asking lives in a completely different reality from my own. They’re an alien.
My sense is that these aliens haven’t been on a bike since they first got their driver’s license and would only consider riding a bike if their car broke down and both Über and Lyft had banned them for life. Perhaps they view bicycles as toys for children and hipsters? They hear electric bike and think “Finally! A bicycle without all that bothersome pedaling!”
But I like pedaling! I didn’t get an ebike because I lost my driver’s license to a DUI or because I have a physical limitation that prevents me from operating a traditional bicycle. I got an ebike because I wanted to build a solar powered long distance touring machine that would extend the daily range of a loaded touring bicycle on a trip around the world. It’s a hybrid. The electric motor and pedal power are not mutually exclusive. They go great together. Think chocolate and peanut butter, not chocolate or peanut butter.
This question is typically asked with a tentatively hopeful expression so I suspect
the alien my new friend is not looking for a lecture on semiotics. I think the answer they’re looking for goes like this:
Yes. The motor is powerful enough to make the bike go without any pedaling whatsoever. You could just use the pedals as foot pegs if you really wanted to.
Next time, I’ll just lead with that.
How much solar power are you getting?
Short answer: 20 miles (32 km) per hour.
Yes, really. And it’s true if I’m moving or stopped. For each hour of full sun, I get enough energy to travel 20 miles. If I’m moving, that energy is immediately converted to mechanical energy. If I’m stopped, it’s stored in the battery for later. When it’s cloudy, I’m lucky to get 10 but it can be 5 or less.
Most people asking this question really want to know “Are you getting a useful amount of solar energy?” and “What can you do with it?” The answers are “yes” and “go farther and faster than a touring bicycle without a motor and solar panels.”
Sure, I could give you numbers measured in watts or amps or hours to charge the battery from empty to full. Unless you’re comparing the performance to another electric vehicle in the same weight class, battery size and voltage, those numbers are easily misinterpreted.
The total solar energy production per day varies significantly based on location and time of year, not to mention daily variations due to weather and shading along the route. Overall, my setup gives me a range of 50 to 200 miles (80 to 320 km). The low end is a rainy day with mostly pedal power. The high end is an ideal day with an early start, short breaks, cloudless skies, minimal headwinds and few hills on good roads. Your mileage may vary.
How much did it cost?
Another hard one to answer. Is the person asking the question because they assume this is a commercially available product I purchased on Amazon? I guess I should be flattered as it implies that it’s not completely obviously that it’s home made.
This is a one-of-a-kind prototype. It is the end product of 12 years of research and development. The bill of materials for the latest build adds up to about US$15,000 not including thousands of hours of labor. I’ve spent enough on R&D over the years (bikes, components, materials, tools, etc.) to buy your average four-wheeled midlife crisis status symbol. When I factor in the value of my time at my peak career earnings rate, the total project cost is in the mid six figures.
Why didn’t you try X?
Short answer: I tried X and X didn’t work.
I get this one all the time. Usually, it’s intended as a helpful suggestion from a well-meaning individual who is blurting out the first thing that pops into their head upon seeing a solar bike for the first time. Mostly, these suggestions are impractical or unfeasible because they either fail to consider the design goals of the vehicle I’ve built or they violate the laws of thermodynamics.
I’m sympathetic to people who don’t get it because they’ve never done any bike touring and try to imagine impractical use cases formed by their own experiences. I’m less sympathetic to the conspiracy theorists who feel compelled to educate me about the shadowy cabal of lizard people with a hidden agenda for keeping Nicola Tesla’s secret free energy discovery off the market. I suppose I’m kind of asking for it by riding around on a perpetual motion machine.
Rarely does the person asking consider that I’ve spent 12 years and 45,000 miles (72,000 km) building and road testing this stuff. I have tried at least four different versions of every component on my journey to build the ultimate round-the-world machine. So, very likely I tried X and X didn’t work. I try to accept the suggestion in the spirit in which it was given so I smile and thank them for their input.