Around the world on a solar ebike

[solarEbike]

Um… hello. I’m imagining this post will become the introduction for what will eventually become a mega-thread over the next several years so I feel some pressure to make it a good one.

I’ve been tinkering with adding solar charging to an ebike for a little over 10 years. The goal has always been to add enough solar power to the bike to offset the additional weight of the motor, batteries and solar panel while extending the range compared to a fully loaded touring bike without electric assist.

This is easy moderately difficult to do if you cherry pick your riding days and only count cloudless summer days. But on a long distance bike tour you don’t have the luxury of being a fair weather rider so this equation needs to include foggy, cloudy and rainy days as well. In other words, my average day on a long distance tour needs to be better than riding a bike without all that extra weight and clutter. An ebike with a dead battery is no fun. I think I’m close to accomplishing that goal.

Here’s the penultimate prototype:

Current build

Penultimate prototype.jpg (180.33 KiB) Viewed 21026 times

And here’s what’s on the drawing board:

On the drawing board.png (84.79 KiB) Viewed 21026 times

What about the “around the world” part? Right. Almost forgot. I’m building this crazy contraption so I can take the ultimate victory lap when it’s ready: head west and keep going until I return to my starting point and/or meet myself. Whichever comes first.

I’ve posted a brief history in pictures of this project on my blog. There are a few photos up on Instagram and a couple of short videos on YouTube. I expect to have more content for a non-technical audience once I’m posting from the road. In the meantime, I figure this is the best place to discuss all the nitty gritty technical details.

Cheers,
Mark

PS: There’s an in-depth video coming soon to the Grin YouTube channel so subscribe now to get a notification when it comes out.

UPDATE: The video is now available here: https://www.youtube.com/watch?v=7RGBBNctWNA

UPDATE 2: If you're here because you're thinking about adding solar to your own ebike, start by reading How to convert your ebike to a solar ebike. It's my synopsis of lessons learned (as of August 2020) with hardware recommendations and solar panel sizing tips.

[solarEbike]

A few build photos to get the ball rolling.

Custom fabricated battery box with room for wiring, spares and tools. Magnetic latches, waterproof charging port and integrated heatsink for Phaserunner.

battery box layout.jpg (151.42 KiB) Viewed 21016 times

Wiring channels cut into foam for PV output, LED lights and photosensors for automated tilt mechanism.

routing wiring channels in foam.jpg (169.7 KiB) Viewed 21016 times

Testing the lights.

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Foam sealed with fiberglass and epoxy. Aluminum inserts embedded with extra layers of fabric for attachment points.

back of foam panel before painting.jpg (90.17 KiB) Viewed 21016 times

Back side of PV modules before attaching to foam support panel. Using extra-thin double-sided foam tape suitable for low surface energy plastics to ensure lasting bond with solar backsheet material. Note junction boxes on back side of panel. On the next build I will bond the entire surface with GE Sillicone II rather than using double sided tape.

PV module back sides with adhesive placement.jpg (129.22 KiB) Viewed 21016 times

Fabricating bracket for Grin motor torque arm.

motor bracket fabrication.jpg (136.73 KiB) Viewed 21016 times

And here's the finished bracket. The bracket is threaded and there's a nut on the back so I can adjust the clamping force on the carbon fiber suspension fork independently from the clamping force to the torque arm. Should make it easier to change tires and fix flats. If you're certain I'm going to die a horrible death because I'm using a front hub motor with a carbon fiber suspension fork, check back on this thread in a couple of years. I've got 1100 miles (1770 km) on it so far and it's holding up just fine with regen braking.

custom torque arm bracket.jpg (146.93 KiB) Viewed 21016 times

Back of the panel showing tilt mechanism via 12V linear actuator, elastomer suspension, and almost no visible wiring.

tilt mechansim with linear actuator.jpg (286.59 KiB) Viewed 21016 times

Riding position showing self-shading on solar panel when riding toward the sun early and late in the day. This is definitely a design trade-off. I didn't do a solar roof because it would make the bike top-heavy and more susceptible to cross-winds. The next build will have the solar trailer a little further back.

riding position wth self-shading issue.jpg (230.35 KiB) Viewed 21016 times

And finally, a profile view to better show the bike geometry. The next build will use a similar bike but both wheels will be 20" and the bike will have a folding hinge in the middle for easier transport.

profile at sunset.jpg (155.66 KiB) Viewed 21016 times

[Voltron]

That's an awesome project on so many levels...

[John and Cecil]

I can understand boating or flying around the world, but how would you ride a bike around the world? It is not even possible to walk around the world except with oxygen supply equipment and heavy boots to keep you on the ocean floor.

It is very cool though!

[solarEbike]

I can understand boating or flying around the world, but how would you ride a bike around the world?

I assumed the inflatable pontoons were implied.

ridiculous or ridiculously awesome.jpg (12.49 KiB) Viewed 21000 times

[/url]


[Rats. I told myself I wouldn't feed the trolls. Must. Try. Harder.]

[John and Cecil]

Dude, if you could build inflatable pontoons on that and actually go around the world I think you might end up with a movie offer

Seriously though I was not messing with you, I truthfully do not understand how it could be considered riding around the world if you cannot possibly make it all the way. You would obviously need to fly or take a ship to cross the oceans, and those routes coule be different. Do you have to stop at every island and ride across it, or do you pass over some land masses. If the plane took the correct route you might only need to cross the usa and fly the rest of the way over water. It would seem more accurate to be considered crossing several continents, or even all of them.

I think it would be a great accomplishment though, and we will be rooting for you!

[billvon]

Seriously though I was not messing with you, I truthfully do not understand how it could be considered riding around the world if you cannot possibly make it all the way.

I think "riding around the world" is akin to "walking around the city." It does not imply that the person will cover every inch of the periphery of the city - but that he will cover a lot of ground.

My girlfriend and I once rode across Europe, but we took a train through the mountains in the Ardennes. Still a lot of fun, and got to see the world from very close up.

[John and Cecil]

Yes, I have been looking it up and there are people who have walked around the world and they were not in fact Jesus It makes a big difference which way you go I guess.

The bike with the solar panel trailer is awesome! I wouldn't mind a small cargo trailer with a solar panel top, and maybe a small sunscreen for Cecil made with a small solar panel. I was also considering those roll up solar panels so you can charge your battery while spending the day at the beach. I wish they were not quite so heavy and they were more efficient though.

Still very cool!

[solarEbike]

I wouldn't mind a small cargo trailer with a solar panel top, and maybe a small sunscreen for Cecil made with a small solar panel.

Go for it!

dog-trailer-+-50w-solar-panel-+-MPPT-boost-controller.jpg (89.95 KiB) Viewed 20953 times

I would add a coroplast panel to keep the PV panel from flexing too much and just attach it with zip ties. If you're in the US, $216 plus tax and shipping for trailer, solar panel and boost charge controller. I don't vouch for any of these personally but that should be a good starting point.

EDITS: Fixed link rot.

[John and Cecil]

I see they have decent semi flexible panels now. I just saw a 200w one that is 57" x 31". Perhaps it can be used as a curved roof over an open trailer like a conestoga wagon when riding and when parked the sides can extend up and flatten it out to take in more sun. The wind must be brutal on those panels though. When riding a motorcycle in windy conditions you can really feel the force by merely pointing your knee to the windward side. I often use my knee as a sail to help tack into the wind when getting blown sideways on the freeway.

Maybe the curved flexible panels would work ok for a trike too. The wind should pass through it like wind going through a tunnel. It would be nice to be able to generate enough power so the bike/trike can travel on sunny days with no need to charge the battery, or possibly even carry a battery (direct power).

*Ah, I found something similar online that someone made already:

solar-bicycle.jpg (58.32 KiB) Viewed 20948 times

[solarEbike]

When I was 11 years old, my parents gave me a copy of the Guinness Book of World Records. It was a cheaply printed mass-market paperback and I kept thumbing through that volume until it fell apart. The world’s oldest human, the jump rope endurance record, the man who ate an entire bicycle. The more preposterous, the better. The stories of human endurance stayed with me the longest. I was approaching puberty and my body was about to experience all kinds of magical changes. Maybe I would grow the longest human tongue?

More recently, I read Christopher McDougall’s Born to Run and experienced that same sense of wonder about what the human body can accomplish when pushed to the limits of endurance. Our evolutionary heritage as a species has left us poorly equipped for sitting in front of screens all day long. But running down antelopes on the Savannah? Our bodies are uniquely suited to the task. Most of us have just forgotten.

Until a few days ago, I believed the origin of this project was a fully loaded 2000 mile (3200 km) bicycle tour of Italy I completed in 2006 but now I’m thinking this all started with that book.

When I started planning the route for this adventure it only made sense that I would consult the oracle of St. James Gate, Dublin. They define around the world cycling for record purposes like this:

The journey should be continuous and in one direction (East to West or West to East), that the minimum distance ridden should be 18,000 miles (29,000 km), and that the total distance travelled by the bicycle and rider should exceed an Equator's length, i.e. 24,900 miles (40,100 km)

And that the route

must be ridden through two approximate antipodal points.

But this is my trip and I'm making my own rules. For one thing, I think you should actually travel the length of the equator by bicycle to offset the fact that you’re crossing the oceans by other means. My proposed route consists of:

• 60,000 miles (100,000 km) total distance including water crossings
• 40,000 miles (65,000 km) over land
• 6.5 continents (Antarctica is a definite maybe)
• One pair of antipodes

I didn’t grow the world’s longest tongue. And while I did grow up to be freakishly tall, it’s nothing for the record books. The thought of having to register with Guinness in advance and having to keep daily records and having to collect signatures along the way seems like a giant hassle. But now that I’m reminiscing about that old record book maybe the 11 year in me would like to be in the book.

What do you all think?

proposed-route-as-of-June-2019.jpg (41.61 KiB) Viewed 16932 times

EDIT: Updated map June 2019. Live map here.

[fechter]

That does look pretty epic. I have trouble just going 50 miles.

Question: how much does the solar panel weigh?

[energyi]

Excellent project fechter, know your pain and motivations.

Would be very interested in your charge controller of choice/why, and would recommend anyone looking into doing a similar project to also consider a bifacial module, can generate electricity from both sides.

My experience with a 75 lb trailer plus PV panels written previously here on Endless Sphere and at this blog: http://renewableenergyspace.blogspot.co ... solar.html

etrikepv.jpg (273.71 KiB) Viewed 20888 times

energyi

[billvon]

When I was 11 years old, my parents gave me a copy of the Guinness Book of World Records. It was a cheaply printed mass-market paperback and I kept thumbing through that volume until it fell apart. The world’s oldest human, the jump rope endurance record, the man who ate an entire bicycle. The more preposterous, the better. The stories of human endurance stayed with me the longest.

Me too. It was a thick (2" or so) book and it was printed on flimsy paper; it got pretty tattered after a while, but it was great for car trips.

I just got a hardcover version (with pictures) for my kids, 4 and 6. And I'm even in one of the pictures.

[solarEbike]

Question: how much does the solar panel weigh?

The whole trailer is 30 lbs (14 kg), the tilting red support panel without the PV modules is 7 lbs (3 kg) and the PV modules are 2.9 lbs (1.3 kg) each. I'm now building what will hopefully become the version I take on the road and it should come in at a lower weight and have 350 watts of solar on it. Weight reduction using lots of carbon fiber and custom fabricated PV modules with ultralight encapsulation.

[solarEbike]

Would be very interested in your charge controller of choice/why,

Genasun GVB-8 boost controller. Designed by former MIT solar race car team members. MPPT updates 15 times per second for use on a moving vehicle. Proven track record with past and current The Sun Trip participants.

and would recommend anyone looking into doing a similar project to also consider a bifacial module, can generate electricity from both sides.

Do your bifacial modules have separate outputs for the front and back facing cells? I've encountered them several times as an option for solar carports during my residential/commercial solar career but never found a project where they were the most cost effective solution.

I seriously considered adding two additional rows of cells mounted on long hinges so they face down while riding and swing out 180° to charge when stopped. You can see the back of my panel is designed to accommodate this. But then I ran the numbers and it just didn't pencil out for me. I would mostly need the extra panels on days when I'm trying to do 100-200 miles (150-300 km) but then I consider that I won't have time for long stops on those days so the cells that don't face the sun while riding (and their support structures) negatively impact my Wh per kg number. Albedo irradiance is only a tiny fraction of direct irradiance.

[billvon]

Do your bifacial modules have separate outputs for the front and back facing cells?

Bifacial cells are cells with transparent backing so that they generate from both sides. One output; it just can receive light from both sides.

[solarEbike]

Bifacial cells are cells with transparent backing so that they generate from both sides. One output; it just can receive light from both sides.

Ah. That explains why the bifacial module data sheets I've seen all have just one pair of outputs. I incorrectly assumed they were made with two cells back to back. Well, I'll consider anything that can get me more Wh per kg than my current setup.

BTW, I love the solar camper trailer concept. There's a guy with a camper in this year's The Sun Trip. I'm betting he's the envy of the group when it's time to set up and strike camp every day.

I tried to design a pop-up tent concept that used my trailer as a support structure but just couldn't get it lighter than my 2.7 lb (1.2 kg) 1.5 person backpacking tent.

I also have a design constraint that my entire rig has to be able to fly with me on a commercial flight. That eliminated some other range-extending possibilities like this velomobile I test-rode in Holland two years ago.

velomobile.jpg (219.02 KiB) Viewed 20864 times

[andrebandre]

When I was 11 years old, my parents gave me a copy of the Guinness Book of World Records. It was a cheaply printed mass-market paperback and I kept thumbing through that volume until it fell apart. The world’s oldest human, the jump rope endurance record, the man who ate an entire bicycle. The more preposterous, the better. The stories of human endurance stayed with me the longest. I was approaching puberty and my body was about to experience all kinds of magical changes. Maybe I would grow the longest human tongue?

More recently, I read Christopher McDougall’s Born to Run and experienced that same sense of wonder about what the human body can accomplish when pushed to the limits of endurance. Our evolutionary heritage as a species has left us poorly equipped for sitting in front of screens all day long. But running down antelopes on the Savannah? Our bodies are uniquely suited to the task. Most of us have just forgotten.

Until a few days ago, I believed the origin of this project was a fully loaded 2000 mile (3200 km) bicycle tour of Italy I completed in 2006 but now I’m thinking this all started with that book.

When I started planning the route for this adventure it only made sense that I would consult the oracle of St. James Gate, Dublin. They define around the world cycling for record purposes like this:

The journey should be continuous and in one direction (East to West or West to East), that the minimum distance ridden should be 18,000 miles (29,000 km), and that the total distance travelled by the bicycle and rider should exceed an Equator's length, i.e. 24,900 miles (40,100 km)

And that the route

must be ridden through two approximate antipodal points.

But this is my trip and I'm making my own rules. For one thing, I think you should actually travel the length of the equator by bicycle to offset the fact that you’re crossing the oceans by other means. My proposed route consists of:

• 60,000 miles (100,000 km) total distance including water crossings
• 40,000 miles (65,000 km) over land
• 6.5 continents (Antarctica is a definite maybe)
• One pair of antipodes

I didn’t grow the world’s longest tongue. And while I did grow up to be freakishly tall, it’s nothing for the record books. The thought of having to register with Guinness in advance and having to keep daily records and having to collect signatures along the way seems like a giant hassle. But now that I’m reminiscing about that old record book maybe the 11 year in me would like to be in the book.

What do you all think?

proposed route as of June 2018.jpg

Outstanding project!
I wish you succes!
As a long time bicycle rider, the only hardship that always bothered me is the the traffic whizzing by.
In all developed countries there is no way to avoid high speed traffic, there are no roads (in my experience) where one can enjoy the peace of pedalling along and imerse oneself into the surroundings without man made interference and eventually risks and discomfort or even danger.
None the less you are a brave man and i will keep my fingers crossed for your biking enedeavour or for your tongue to grow as much as you like.

[John and Cecil]

Wow that map is EPIC! I was a little proud of myself for doing only 15 miles the other day... LOL!

[solarEbike]

As a long time bicycle rider, the only hardship that always bothered me is the the traffic whizzing by.

I hear you. Sharing the road with cars takes some getting used to. I've been ebike commuting 20 miles a day for most of the last 10 years Rain or shine. Half of that has been along side of traffic. It helps if you make good decision like riding assertively and defensively as the situation dictates. It helps if you assume cars don't see you. I use two mirrors on my bike, wear high visibility clothing, run very bright lights day and night, never ride with headphones, etc. but none of these will do me any good against the teenager behind the wheel looking at their phone instead of the road. But what's the alternative? Staying home? Joining the traffic jam, stuck in a metal box on wheels? No thank you.

...or for your tongue to grow as much as you like.

I may not be able to lick my eyebrows but I did eventually learned to speak in four different tongues, which is likely to be more useful on this adventure.

[John in CR]

Have you tested your panel in hot sun? It all looks great though I'd want to use the panel for shade like my motor customer who took his solar ebike all the way around Australia. I ask about the panel testing, because with the foam I'd worry about heat buildup, which is a big concern with factory built panels here in the tropics where the sun is stronger. The heat reduces panel efficiency and reliability. Since cells are designed to absorb as much sun as possible and what doesn't get converted to electricity becomes heat, I'd worry whether the foam and resins can handle the temps.

[solarEbike]

Have you tested your panel in hot sun? It all looks great though I'd want to use the panel for shade like my motor customer who took his solar ebike all the way around Australia. I ask about the panel testing, because with the foam I'd worry about heat buildup, which is a big concern with factory built panels here in the tropics where the sun is stronger. The heat reduces panel efficiency and reliability. Since cells are designed to absorb as much sun as possible and what doesn't get converted to electricity becomes heat, I'd worry whether the foam and resins can handle the temps.

Good point. Heat is a legitimate concern. I've done about 500 miles (800 km) of road testing with this red foam panel, including a couple of days with 100°F (38°C) ambient air temperature so assuming solar cell temps are 25°C above ambient, that's hot enough to slow-cook an egg. Under those conditions, large blisters appeared between the fiberglass/epoxy skin and the extruded polystyrene (XPS) rigid construction insulation foam. Not enough to compromise the integrity of the panel, but it probably wouldn't survive three years of bouncing around the world. I suspect the culprit was outgassing from the foam at elevated temperatures. It turns out that this is a known issue among surfers who use certain types of XPS foam cores.

I've talked to the guy who builds ultralight PV module assemblies for most of the North American solar race car teams and he told me to expect up to 75°C (167°F) cell temperatures based on race conditions in Texas. I believe the fluoropolymer top and bottom sheets and the encapsulant will be able to handle that but I'm switching out the foam core for Nomex honeycomb and using an epoxy with a higher glass transition temperature (Tg). First test build video:



As for using the solar panel as a canopy roof on the bike, it's a popular choice with many of The Sun Trip participants so clearly it can be done. I have no doubt I will be second-guessing my decision not to build a roof on many hot and rainy days. My feeling is that this works better on a trike than a 2-wheeler. Having had a tadpole trike some years back and having flown with bikes, I elected to use a folding 2-wheeled recumbent for my trip. I'm trying out a mini-roof idea now. Will post photos if it works. Better yet, will post photos if it doesn't work because those are often more instructive.

PS: Justin gives me credit for inspiring his decision to use fiberglass/foam construction for his panel. I’m keeping my fingers crossed that this works out well for him. I don’t want to incur the wrath of the ES community if anything bad should happened as a result.

[Cephalotus]

This is what I plan to use to stabilize my "semiflexible" solar modules.

It's called Metawell Aluflex, it's made of aluminum and weights around 2,2kg/m²:

https://www.metawell.com/wp-content/upl ... hl_h47.pdf (sorry, datasheet is in German)

It's bendable in one direction, but quite rigid in the other if you glue the flat surface to the module. In that case the area to dissipate heat on the rear is extended. I plan to do some thermal tests in the upcoming weeks...

Aluflex2.jpg (122.81 KiB) Viewed 20773 times

I also use solar modules with ETFE front side instead of the cheaper PE versions. ETFE will last much longer under hot conditions ans also does not reflect as much light as PE, which imho is a real security concern when using low mounted panels in traffic.

[solarEbike]

It's called Metawell Aluflex, it's made of aluminum and weights around 2,2kg/m²

Nice. Haven't seen that one before. My Nomex (aramid) honeycomb core panel in the video above came in at 1.2 kg/m² with 5.5 oz/yd² (186 g/m²) cloth on both sides and my second test was 1.0 kg/m² with a lighter cloth on one side. Given the Sunpower Gen III cell temperature coefficient of power is -0.29%/ºC, I would need to see a significant cell temperature drop to offset the extra weight. It's all about the Wh per kg for me.

2015 The Sun Trip winner Bernard Cauquil is using aluminum honeycomb for his current panel.

I also use solar modules with ETFE front side instead of the cheaper PE versions. ETFE will last much longer under hot conditions ans also does not reflect as much light as PE, which imho is a real security concern when using low mounted panels in traffic.

Absolutely. Fluropolymer topsheet is the way to go. My current and future panels have this as well.