need help with hand lamination of flexible sun power solar cells on bike trailer

ThinkFab

100 µW
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Jul 12, 2016
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9
Location
lansing, Michigan
I am gearing up to start a solar trailer build project, and part of that project involves building a curved solar top, kind of a slight convex surface for strength, and I wonder if anyone has any experience with doing this type of project. I see the flexible panels with the sun power cells and although they would work conceptually, I would like to get my hands dirty building a very lightweight and tough ~250w array. Hoping to keep the total weight of the lid down to around 10-14 lbs. I have used the flexible panels in the past, and while the low weight is good, the fragility of them bouncing around while traveling down the beautiful pothole filled roads of Michigan is not ideal. Lets start a discussion on this topic, and best practiced of materials used, and materials that would be good to experiment with. So far there are considerations for flax fiber and bio-resin, with a carbon backing.

-Rex
 
ThinkFab said:
So far there are considerations for flax fiber and bio-resin, with a carbon backing.
Carbon is conductive. There was a rather spectacular failure of a Sunracer-type vehicle due to that problem.
 
Thank you for making sure I have this information. The carbon fiber would not be used directly under the solar cells specifically for this reason.
 
FWIW, once you put a curve into a flat panel, it gets a lot more rigid. So light materials like wood panel would work fine, with the curve set into it by a light rib. Think how they built fabric wings on airplanes in the 20's.

Reinforced by the rib frame, very light material could be very rigid, such as coroplast, or even, doped fabric.
 
I did some epoxy/glass/silicone cell laminates as experiments, several 3.6v cells with 6x100x100 monocrystaline wafers that were laid face down on a mould face of polycarbonate sheet, the first two layers of light weight cross weave glass fiber were wet out to clear consistancy and the cells were carefully pressed onto the weave until most excess resin came out, this was followed with two more layers of glass cloth and more epoxy and vac bagged and cured at 80 degrees C. The polycarbonate sheet was then peeled off the front leaving a butifully optically clear fininsh on the panels front side the glass fiber was almost totally transparent and invisible.

the truly amasing thing was the flexibility of the resultant laminate. no loss of electricl performance with repeated flexing to a 50cm radius, at 40 cm radius electrical performance was degraded due to minute fractures in the cells.

I think the key was utting an equal thickness of glass either side of the silicone wafers preventing tensile straining on them during flex as would be the problem it they were on top or bottom of the laminate.

a lesser bend than 50cm or using thinner silicone that can be had today would be even better these were late 90s cells not the new ones that can be 1/4 the thickness. carbon should be fine if you have a linen backing but i would go with glass infront and behind cells with carbon behind that if you need more strength.

dogman dan has the right idea formed over ribs with another lightweight sheet over the back makes ultra ridgid flattened tube that has torsional stability, you could make yourself a mean lightweight verandah roof for lunch stops on your trailer and if you solder the panels up yourself you can add shade tolerance with low voltage drop diode bypass on every cell
 
dogman dan said:
FWIW, once you put a curve into a flat panel, it gets a lot more rigid. So light materials like wood panel would work fine, with the curve set into it by a light rib. Think how they built fabric wings on airplanes in the 20's.

Reinforced by the rib frame, very light material could be very rigid, such as coroplast, or even, doped fabric.

I like your thoughts on this. So far, the plan is to actually built the solar panel in a hollow format, allowing a secondary cover to fit, tucked into the solar top. This would allow the panel to be angled toward the sun on longer rides in the same direction, gaining more solar input, and allowing the trailer to stay covered. I don't expect the strength to be of much issue, as there will be a "rib" of sorts built into the circumference of both the solar top, and the inner cover. Space inside the trailer will need to be considered highly valuable, and even 4" of ceiling height should be considered part of this valuable space. If wood ends up being the material of choice, I will keep your thoughts in mind. Thank you for your input.
 
mechhead said:
I did some epoxy/glass/silicone cell laminates as experiments, several 3.6v cells with 6x100x100 monocrystaline wafers that were laid face down on a mould face of polycarbonate sheet, the first two layers of light weight cross weave glass fiber were wet out to clear consistancy and the cells were carefully pressed onto the weave until most excess resin came out, this was followed with two more layers of glass cloth and more epoxy and vac bagged and cured at 80 degrees C. The polycarbonate sheet was then peeled off the front leaving a butifully optically clear fininsh on the panels front side the glass fiber was almost totally transparent and invisible.

the truly amasing thing was the flexibility of the resultant laminate. no loss of electricl performance with repeated flexing to a 50cm radius, at 40 cm radius electrical performance was degraded due to minute fractures in the cells.

I think the key was utting an equal thickness of glass either side of the silicone wafers preventing tensile straining on them during flex as would be the problem it they were on top or bottom of the laminate.

a lesser bend than 50cm or using thinner silicone that can be had today would be even better these were late 90s cells not the new ones that can be 1/4 the thickness. carbon should be fine if you have a linen backing but i would go with glass infront and behind cells with carbon behind that if you need more strength.

dogman dan has the right idea formed over ribs with another lightweight sheet over the back makes ultra ridgid flattened tube that has torsional stability, you could make yourself a mean lightweight verandah roof for lunch stops on your trailer and if you solder the panels up yourself you can add shade tolerance with low voltage drop diode bypass on every cell
These are almost exactly the thoughts I have had in the building process of this trailer top. Let me tell you how happy I am to hear that someone has created this with success. As for the cloth backing, would a fiber like kevlar be a reasonable candidate? Thank you so much for sharing your procedure of the build process. using polycarbonate as the mold backing seems like a no brainer, but somehow I hadn't thought of it yet. THANK YOU!
 
My thoughts exactly, be able to tilt right or left and ride, although that would work best for riding more or less east or west only. My plans unlikely to get much beyond fantasy though. I got only as far as a trailer prototype.

At least, be able to park in the evening so the panel easily can be tilted to the east in the am. So some kind of easy to unlatch hinge on both sides.

Possibly even modular, so you can easily lift off and reposition the lid sections when parked.

I was also thinking of a light fabric cover, if nothing else to keep stuff from bouncing out of the trailer box in motion. Maybe just a repurpose of your tent fly. Bad weather of course, no reason to tilt the panel towards no sun. so the lid gets buttoned down in actual rain. I saw no reason for the weight of two hard tops. I was thinking of the commercial flex panels, having seen them used by others here, with no mention of the flexing in motion causing problems.
 
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