My solar bike

[avandalen]

The panel placement looks a bit awkward to me. Hard to ride it on a crowded sidewalk. I think trailer mounting would be a more viable option but still wouldn't be sporty.

Gary

Yes, I can't ride it on a crowded sidewalk...
Gary, can you look at the added articles at my site?

 

[avandalen]

Make it a shade, with the support coming up from behind the seat post. That would be nice on hot sunny days. How heavy are those panels?

Thanks, that is a good option! The goal is a panel weight of about 2 kg total, it is definitely not cheap...

 

[avandalen]

140 watts of what voltage? No way even 12v.

The real problem I see with the setup in the OP is if the plan is to generate useful electricity while riding, it needs to be at very low speed. Otherwise the increased wind resistance is likely to offset the power generated by the panels. That's why my suggestion to the gentleman wanting to do a solar bike for a 2000km ride was to arrange a 100-200W of panels into an aerodynamic form like a tailbox, and by means of mornings, long midday stop, and late afternoons, that several hundred watts of foldout panels are used to charge the battery pack. Of course, store bought panels won't work due to the weight, since solar panels aren't made for mobile use.
John

I have calculated the PV panels air drag. The result of the calculation is an air drag of 3W at 20km/h. See here:
http://www.avdweb.nl/solar-bike/solar-panels.html

 

[dodjob]

Hi there!
First, Happy new year!
Your panels weight only 1.1Kg/piece (!!) Daaamn!! I have two 120W monocristallin panel at home and they weight 16Kg... both ' Don't you need a frame for them or a protection in order to avoid any damage? (yes I'm very surprised of the weight )
Did you make a real test concerning the power output? Sorry to be so doubtful but 200W/m2 (manufacturer data) is really a lot, even in the best conditions, and due to experience I'm quite mistrustful with manufacturer's datas.
My panels are very sensitive to orientation and shadow. They sink of 50% drop very quickly and they are rated "good".
Concerning the shape I also think that the trailer is the best solution, I think that there were a swiss guy who made the turn around the world with such setting (on a "car"). This has two main advantages, it doesn't create a big aerodynamic drag and it cannot fall If they are expensive I think you don't want to damage them
Hope you got it working soon for tests!
Regards,
H.

 

[John in CR]

As a practical test try riding the bike around with some thin plywood to simulate the effects of the solar panels, or better yet, glue multiple layers of cardboard together to accurately simulate the panels. BTW, since you're expecting 2cm thick, I was wondering exactly what your construction plan is for the DIY solar panels. You mentioned honeycomb, but is that something you have a cheap or free source.

Personally, I think you're underestimating how much the wind will want to grab these things, but for very calm sunny days and low speeds, it will be a really cool solar assisted bike. I tend toward the more practical, but that doesn't mean I don't support those pushing the envelope like youself. Keep us posted as you progress.

 

[Jeremy Harris]

I have calculated the PV panels air drag. The result of the calculation is an air drag of 3W at 20km/h. See here:
http://www.avdweb.nl/solar-bike/solar-panels.html

The drag calculation is correct for a flat plate that is absolutely edge-on to the apparent wind at all times, but pitch it by just a degree or two and you have a significant increase in force. In essence you have two inefficient aircraft wings, that will generate some lift. This lift will act at a vector that is perpendicular to the apparent wind, not perpendicular to the surface of the solar panels, so will act to unbalance the bike. It will also create induced drag that is proportional to the lift generated, adding to the form drag you have from the projected frontal area of the panels. Bear in mind that side winds are the problem here, or more specifically the vector sum of the side wind and the apparent wind caused by the motion of the bike. The force needed to unbalance a bike, by taking it outside the range of corrective moments that the rider can provide by shifting body weight is pretty small. Add in that the lift force vector will change direction extremely rapidly as the bike rolls, going from a maximum positive to a maximum negative value in a short time interval as the panels go from a positive to negative angle of attack relative to any side wind component and I think you have a bit of a recipe for instability on a fairly large scale.

Jeremy

 

[GrayKard]

The panel placement looks a bit awkward to me. Hard to ride it on a crowded sidewalk. I think trailer mounting would be a more viable option but still wouldn't be sporty.

Gary

Yes, I can't ride it on a crowded sidewalk...
Gary, can you look at the added articles at my site?

Did some reading on your site and saw this:

We require full sun in summertime else the solar bike is not useful. In the Netherlands the solar bike can be used maybe 20 days a year.

Doesn't seem very practical if it sits in the garage over 300 days a year. Is this just a project to see what you can make?

 

[avandalen]

Hi there!
First, Happy new year!
Your panels weight only 1.1Kg/piece (!!) Daaamn!! I have two 120W monocristallin panel at home and they weight 16Kg... both ' Don't you need a frame for them or a protection in order to avoid any damage? (yes I'm very surprised of the weight )
Did you make a real test concerning the power output? Sorry to be so doubtful but 200W/m2 (manufacturer data) is really a lot, even in the best conditions, and due to experience I'm quite mistrustful with manufacturer's datas.
My panels are very sensitive to orientation and shadow. They sink of 50% drop very quickly and they are rated "good".
Concerning the shape I also think that the trailer is the best solution, I think that there were a swiss guy who made the turn around the world with such setting (on a "car"). This has two main advantages, it doesn't create a big aerodynamic drag and it cannot fall If they are expensive I think you don't want to damage them
Hope you got it working soon for tests!
Regards,
H.

Hi, happy new year to
I know, I do not really get 200W/m2. The articles are already updated so see your answers at my site....

I will use a Sandwich panels, See here:
http://www.avdweb.nl/solar-bike/solar-panels.html
Here you can also find info about air drag, tilt etc

For pencapsulations see here
http://www.avdweb.nl/solar-bike/solar-cell-encapsulation.html

Albert

 

[John in CR]

Hi Albert,

I had no idea you were considering such little protection between the top of your cells and the outside environment. You might want to consider a clear marine varnish as the top coat encapsulation. That's the route I've decided to go, but the varnish will be protecting the epoxy in the thin epoxy/fiberglass layer on top of the cell, not just the raw cells directly. Yes I give up some light that way, but anything protecting the cells will. I can also achieve a smooth exterior surface in that manner, and a smooth surface is likely to have a greater aerodynamic benefit than the light lost due to the extra protective material.

I am unclear about the goal of your build. I believe that solar panels can be practical for a bike, because ebikes require such little power. It seems though that you are shooting for a build with no battery. To me, even in the best conditions the result will be impractical and a waste of your solar panels. Maybe I just don't understand how you plan to ride. Is it to get from point A to point B, spend time there, and then return, OR will you ride just to ride and not really as transportation? Even the Solar Challenge race vehicles have battery packs, and for very good reasons.

 

[avandalen]

Doesn't seem very practical if it sits in the garage over 300 days a year. Is this just a project to see what you can make?

Hi GrayKard
The solar panels can be dismounted quickly so I can use the bike also when there is no sun.

As a practical test try riding the bike around with some thin plywood to simulate the effects of the solar panels, or better yet, glue multiple layers of cardboard together to accurately simulate the panels. BTW, since you're expecting 2cm thick, I was wondering exactly what your construction plan is for the DIY solar panels. You mentioned honeycomb, but is that something you have a cheap or free source.
Personally, I think you're underestimating how much the wind will want to grab these things, but for very calm sunny days and low speeds, it will be a really cool solar assisted bike. I tend toward the more practical, but that doesn't mean I don't support those pushing the envelope like youself. Keep us posted as you progress.

Dear John
I plan to ride with a dummy front PV panel soon. I hope the bike will not become an airplane.....
Maybe I can buy honeycomb panels at Italy.

Hi Albert,
but the varnish will be protecting the epoxy in the thin epoxy/fiberglass layer on top of the cell, not just the raw cells directly. Yes I give up some light that way, but anything protecting the cells will.

Hi John,
What do you mean, I don't understand, the varnish is on top of the epoxy?
Have you made your own PV panel?
Thanks for the tip, I shall consider a clear marine varnish also. I am currently testing encapsulations.
As you can see at my site, batteries are really needed!
I use the bike only for recreation and for touring many days.

 

[avandalen]

I have calculated the PV panels air drag. The result of the calculation is an air drag of 3W at 20km/h. See here:
http://www.avdweb.nl/solar-bike/solar-panels.html

The drag calculation is correct for a flat plate that is absolutely edge-on to the apparent wind at all times, but pitch it by just a degree or two and you have a significant increase in force. In essence you have two inefficient aircraft wings, that will generate some lift. This lift will act at a vector that is perpendicular to the apparent wind, not perpendicular to the surface of the solar panels, so will act to unbalance the bike. It will also create induced drag that is proportional to the lift generated, adding to the form drag you have from the projected frontal area of the panels. Bear in mind that side winds are the problem here, or more specifically the vector sum of the side wind and the apparent wind caused by the motion of the bike. The force needed to unbalance a bike, by taking it outside the range of corrective moments that the rider can provide by shifting body weight is pretty small. Add in that the lift force vector will change direction extremely rapidly as the bike rolls, going from a maximum positive to a maximum negative value in a short time interval as the panels go from a positive to negative angle of attack relative to any side wind component and I think you have a bit of a recipe for instability on a fairly large scale.

Jeremy

Hi Jeremy
Thanks for you advise. As you see, I have add your info at my site here:
http://www.avdweb.nl/solar-bike/solar-panels.html

The area of the PV panels (1m2) is not much larger than the cyclist frontal area (0.5m2). So I don't suspect much side wind problems anyway.
Also side wind problems of racing bicycle with disk wheels are not known.

 

[John in CR]

Hi John,
What do you mean, I don't understand, the varnish is on top of the epoxy?
Have you made your own PV panel?
Thanks for the tip, I shall consider a clear marine varnish also. I am currently testing encapsulations.
As you can see at my site, batteries are really needed!
I use the bike only for recreation and for touring many days.

Epoxy/fiberglass can be very clear, but all epoxies will yellow from UV, so a few coats of marine varnish is how they keep those beautiful wood/fiberglass/epoxy boats from yellowing. I have a few different mobile applications requiring lightweight but strong solar panels, so like you I'm still trying to figure something out. I need some curve in mine, so I can't use honeycomb panel for rigidity and strength.

Another alternative is a very thin lexan sheet as the top surface, then a thinned clear non-acidic silicone layer to encapsulate the front. That will give me a tough front, but no strength, so I would get the strength on the back side using fiberglass/epoxy. My problem issue is the bond at the silicone with the epoxy. If I can figure out a good way to do the fiberglass first so it is completely cured before doing the front, that would work, but I worry about getting the smooth even surface I want without too much silicone fill.

I think solar charging is very doable for touring, and I wouldn't even worry about trying to go big with the horizontal surface area while riding. Instead, I'd go with a folding panel with only one of 3 or 4 surfaces exposed while riding. Then schedule just a long lunch stop around noon. With the bike parked, you anchor the bike to something and fold out the rest of the panels at a perfect angle for a nice strong charge while stopped. Then what you're able to get while riding is bonus juice. I ride fast, so my moving time is quite low, and I am most interested in solar charging while parked.

 

[avandalen]

Hi John,
What do you mean, I don't understand, the varnish is on top of the epoxy?
Have you made your own PV panel?
Thanks for the tip, I shall consider a clear marine varnish also. I am currently testing encapsulations.
As you can see at my site, batteries are really needed!
I use the bike only for recreation and for touring many days.

Epoxy/fiberglass can be very clear, but all epoxies will yellow from UV, so a few coats of marine varnish is how they keep those beautiful wood/fiberglass/epoxy boats from yellowing. I have a few different mobile applications requiring lightweight but strong solar panels, so like you I'm still trying to figure something out. I need some curve in mine, so I can't use honeycomb panel for rigidity and strength.

Another alternative is a very thin lexan sheet as the top surface, then a thinned clear non-acidic silicone layer to encapsulate the front. That will give me a tough front, but no strength, so I would get the strength on the back side using fiberglass/epoxy. My problem issue is the bond at the silicone with the epoxy. If I can figure out a good way to do the fiberglass first so it is completely cured before doing the front, that would work, but I worry about getting the smooth even surface I want without too much silicone fill.

I think solar charging is very doable for touring, and I wouldn't even worry about trying to go big with the horizontal surface area while riding. Instead, I'd go with a folding panel with only one of 3 or 4 surfaces exposed while riding. Then schedule just a long lunch stop around noon. With the bike parked, you anchor the bike to something and fold out the rest of the panels at a perfect angle for a nice strong charge while stopped. Then what you're able to get while riding is bonus juice. I ride fast, so my moving time is quite low, and I am most interested in solar charging while parked.

Hi John,
Your panels are unlike mine for outdoor use permanetly I suppose. For me, a simple encapsulation will work perhaps.
Honeycomb panelcan be very strength.
Can’t you use PV panels from Pvcool?
http://www.pvcool.com.au/
You can maybe use Bison polymax is ( non-acidic) for glueing instead of silicone?
I have thought about folding panels but initially I do not use it, it is difficult to manufacture.
Albert

 

[John in CR]

Hi Albert,

I have just fragile raw cells and will make my own panels. I want to build them tough enough to handle dings from small rocks on the road. For one application, I'd like to make one tough and strong enough to walk or sit on if possible, which is one reason some curve is required...for far more rigidity. Walk on probably won't work, but I want to try. Regarding folding, mine will actually be separate panels joined with some kind of hinge, so no more difficult than a non-folding panel.

 

[avandalen]

Hi Albert,

I have just fragile raw cells and will make my own panels. I want to build them tough enough to handle dings from small rocks on the road. For one application, I'd like to make one tough and strong enough to walk or sit on if possible, which is one reason some curve is required...for far more rigidity. Walk on probably won't work, but I want to try. Regarding folding, mine will actually be separate panels joined with some kind of hinge, so no more difficult than a non-folding panel.

Hi John
Good luck with your PV panels, Please tell me your progress
Albert

 

[wineboyrider]

Hey Dodjob. Didn't you say in your earlier post that you had a home solar charging station for your ebike???

I have a 12v 120ah? SLA in my garage that i eventually want to charge with a solar panel to charge my lipos... 8)

 

[dodjob]

Hi Wineboyrider,
Yeah I do . With 12V120Ah it'll be perfect
We are mostly making our installation with one 12V100Ah/per ebike. Of course it will depend hoy much miles you want to drive per day and.. your location
As soon as you seems to live in New Mexico it shouldn't be a problem to get some sun .
I strongly recommand you to use monocrystalin panels combined with a MPPT charger. This will help you to get the maximum of your installation.
If you want more infos please PM me. I will be very happy to help you!
Gruß von Regensburg!
H.
PS: Sorry, hab dein post nicht gesehen (war vielleciht zu beschäftig mein Weißbier zu trinken ^^. bin ab jetzt "subscribed" auf diesem post Machs gut!

 

[wineboyrider]

@ Dodjob. I already have a big sla battery. I just want to add some solar panels and charge once in a while. I can hook up my lipo charger to it and use an inverter for my lifepo4 charger. I want an expandable system so I can add panels to it over time....I will mount them on my garage facing the southern New Mexico sun. Even with the cold spell we just had we still had sun.!

 

[dodjob]

The best way if you want to have an expendable system would be to have a system that allow you to put more panels in serie, that will allow you to not have to change the section of all your cabling.
For instance the MPPT charger we are using are accepting up to 100V Uopen for the little 250SMR. It can release his power under 12V or 24V. Under 12V, the controller will deliver 150W max and 300W under 24V. The efficiency will be nevertheless reduced if the Vdrop is big (Vin/Vout).
You can of course use a very simple setting with a "primitive" charge controller (no MPPT), this will be definitively cheaper and quite accurate if you have little solar array in comparison with the size of your battery. For example 100Ah and a 20W solar panel. But you'll loose efficiency under "transitive" weather and you can only add panels in parallel (cabling section to change at every addition or over sized from the beginning)
With such panels (20W), even if the sun is quite present in New Mexico you won't drive under extraterrestrial power very often
We advise people here in Germany to use a 120W panel and a MPPT controller with a 100Ah battery/ebike. That's allowing about two charge without sun and for what we have seen until now, it's really enough. We nevertheless offer a "confort-option" with two batteries. At this point the sun can not shine for 4 days of ebike use. Yeah I know, German Weather sucks :-/
Hope this helps!
Gruß,
H.

 

[avandalen]

For instance the MPPT charger we are using are accepting up to 100V Uopen for the little 250SMR. Hope this helps!
Gruß,
H.

Hi dodjob,
I'm definitely use a MPPT. In total there are 60 solar cells in series for about 30V input or less (depends on the shade). The battery is 36V. What for MPPT do you suggest?

 

[dodjob]

Hi Avandalen,
Sorry, I've juste noticed that I was completely hijacking your thread :-/.
Concerning your MPPT.
Most of the MPPT I know, are only bucks (drop down).
If you want to use a standard MPPT you will have only two solutions, decrease the voltage of your battery or increase the one of the pannel .
We strictly use one brand of charge controller (from schams-electronics) because they are simple, very reliable (more than 20Years on air 8) ) and REALLY efficient. (I work with this company for a while know and I also can ask him some "special" features and mods for nearly nothing :-D
The price is nevertheless related to the quality, this is not a no-name chinese analog mppt
Hope this helps!
Gruß,
H.

 

[avandalen]

Hi Avandalen,
Most of the MPPT I know, are only bucks (drop down).
Gruß,
H.

Hi
My solution is to split the battery into two batteries of 18V in series. The two 18V batteries are charged alternately (with a relays) . Thus I can use a MPPT ~ 30V to 18V.

Albert

 

[dodjob]

This means that you don't want to recharge them during the trip?
Gruß,
H.

 

[avandalen]

This means that you don't want to recharge them during the trip?
Gruß,
H.

Hi
The panels are loaded during the trip (and discharged) and the MPPT charger switching between the two panels goes automatically, say every 5 minutes.The panels are loaded during the trip (and discharged) and the MPPT charger switching between the two panels goes automatically, say every 5 minutes.

Albert

 

[dodjob]

mmm :-/
What kind of battery chemistry are you intending to use? I fear that the battery won't like it at all. Do you use a BMS? if it's the case I do think it will go crazy because of the voltage's difference between cells. If not, you will more than probably have shitty performances and short cell life because of non equal load on every cells.
I woud really advise you to go for a 8S setting (24V). If you do, you will have a 40V no-load, 33.6V optimal on the module side and a standard (setted) 24V MPPT 250W on the other side. You would be done
Gruß,
H.