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Comment by topher515 | Hacker News Reader

I had a buddy who built a solar e-bike for Burning Man; it had a sort-of roof on top, so it had room for something like four of those flexible 100 watt solar panels[1].

He told me his biggest build-regret was the solar panels. Mounting the solar panels on the bike makes everything much more complicated—which means it's more expensive and more delicate. And even if it doesn't shake itself apart, you're constantly thinking about where and how you're parking it.

The right solution for solar powered biking is to keep the solar panels off the bike, fixed in place, facing the right direction. Then you can use lots of cheap, heavy panels, and just plug the damn bike in when you get home.

[1] for example: https://www.amazon.com/Flexible-Monocrystalline-Bendable-Sem...

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Unless you're off the grid, is there any use case for the solar panel you linked?

It costs $90, not including the protection circuitry.

Even if you pay a lot for electricity (e.g. $0.35 per kWh, like in PG&E service regions), you'd need to be drawing 100W for 7 hours per day, for 365 days, before you break even.

I guess realistically you're more likely to break even after 2 years? Do these small panels 'wear out' over time, or will they work for several years?

Solar panels don't really wear out like that. It's possible that severe hail may damage these flexible, less well protected cells but you can easily expect well over a decade out of them. Most residential systems are rated for 25-30 years but can realistically last longer.

Most residential systems have a warranty for 25 years. The manufacturer guarantees that there is no significant degradation for that time. That probably means that they last a lot longer than that.

Or it means they enter the steep part of the bathtub curve at 26yr

Wouldn't it be smarter to have a warranty period end further from a significant increase in the probability of failure?

Well if you break even even in 2 years that's still a great investment, beats most other investments out there and there is very little risk

Ultimately it's a semiconductor, so it's affected by the same aging processes that transistors and LEDs undergo. Actually, LEDs and solar cells are physically the same component, just designed for opposite use cases - much like motors and generators.

You can reasonably expect it to lose less than 1% of original efficiency a year, so they should last decades.

I doubt there are many silicon based LEDs. So the both might be made from silicon, but they are definitely not the same component.

With the range of cargo ebikes it isn't hard to get off grid. Riding a century - 100 miles (200km) - is regular achievement for normal bikes - not e-bikes. Most ebikes only have a range of 40 miles, so just the ability to get 50 miles by charging while riding can be useful. If you go camping, solar puts a campground that if more than 20 miles from you in range: so long as you can recharge while at the campground for a few days you can get back home again.

Note that none of the above is about saving money. Other than indirectly because it lets you use a bike for trips that otherwise would require a car, and cars cost a lot more money to own. The above are also uses that I have for an ebike (I don't have one, but those are potential uses making me interested in one), and solar would help make it work out.

Aren't those last 50km going to much more difficult since you're not having to carry the extra weight, and the extra resistance of the electric motor?

Taking an ebike farther than the batteries range should be considered impossible. While it is possible to ride on a dead battery, the effort isn't worth it. Thus a regular bike has more range than an ebike.

E-Bike touring would be an excellent use case for this. A lot of people would love to bike tour but don't have the physical ability. I have a friend who was touring on an E-Bike because it made hauling more stuff easier and he would just recharge at each stop. A solar panel would have made a huge difference.

That rad power bike in the article is already quite shitty with the high cargo position compared to a more sensible approach to put cargo in a front bed.

This bike seems to have been designed to carry kids at the bike, not haul stuff.

That's a bit negative. Like you say, better at carrying kids than stuff (which is how I use mine), but that doesn't make it "quite shitty".

I own this bike: it's very good at carrying kids, pretty good at carrying stuff, and exceptionally good value. Rad has been shrinking the back wheel to lower cargo position as iterations progress, which is nice.

They make a front rack for it as well. But it isn't a bakfiets. But it's also about 1/4 the price.

I've owned a RadCity before and it wasn't shitty at all. The dang thing is still running after 7k miles of rough treatment and crashes. The only problem I really had is with the spoke pattern on the drive wheels. They used way too thick spokes that didn't like being bent at such a sharp angle.

Exactly, have the heavy, cheap panels charge a battery bank and plug into that when you get home. Still off grid, charge any time.

The mileage lost due to carrying an additional bank gets covered by the additional bank, is this correct?

Unless you are going someplace for a few days that you cannot get home from on your charge. Then you need the charger with you.

What were the costs?

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