diy solar

diy solar

Lightweight solar panels without compromising on efficiency?

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davelondon

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I'm designing an expedition truck which will have solar panels attached to the roof. However I would also like to store in the truck some additional solar panels that can be manually placed on the ground around the truck to get more power. I'd like these panels to be approx 2m x 1m each.

I've seen lightweight (~5kg per square meter) flexible panels but these seem to be far less efficient (under 100 watts per square meter) than the heavy (~15kg per square meter) rigid panels (over 200 watts per square meter).

Do more efficient but lightweight panels exist? If they need to be rigid, I'm thinking about mounting them on foam cored carbon fibre panels, which are only 2.7kg per square meter. Perhaps the solar panels can be removed from a standard panel and re-mounted onto a lighter frame material?
 
There are very lightweight "folding" and "rollup" panels, but they are absurdly expensive. The weight for the most part of any traditional panel is the protective cover and the frame holding everything together. If you want to get really frisky and just make a panel, all you need are the cells.




 
Simple ETFE coated flexible 100W panels are extremely lightweight. Historically, they haven't been horribly durable, but a handful of options with the ETFE coating to protect them have emerged with 5 year manufacturing warranties with 20+ year performance warranties. Given also that you won't be permanently mounting them and subjecting them to daily exposure means the biggest risk is handling damage as you deploy them.
 
I don't see the warranty. I would hesitate to buy flexible panels unless from a long-standing manufacturer with a good reputation. While I'm not big fan of Renogy, it's pretty clear they're here to stay, and they offer a 5 year warranty.
 
Hmm it's for an expedition truck, so if I have a failure in the middle of the gobi desert, it's highly unlikely I'll be able to return them and get a replacement sent out, so I think it's a case of ordering a few extra panels to replace failures ?
 
Now if we're saying the Renogy panels will last 10 years but other panels will fail after 6 months, then that's a different matter...
 
Regardless of source, your stated use demands redundancy, so that's a separate matter entirely. Long-standing companies with good warranties are likely to produce a reliable product on the basis that they don't want warranty liability with each sale.

What has happened in the past is a brand pops up, sells a ton for a period, and then when they take a crap a year later (after being mounted and baked all year), the company is no longer to be found.

If you have confidence in the reputation of the company you linked, then that's good enough for me.
 
Best quality is going to be rigid panels with tempered glass.
No panel is going to be > 200W/m^2 (20% efficient and 1000W/m sun) unless it is a more expensive multi-junction cell. That would be thin-film or thin film on wafers, to capture the extra electrical energy from different wavelengths without as much heat.
Some panels weigh 50% more than others of same output. My 327W panels are 41 lbs/18.6 kg.

Heat is more of a problem if air is trapped behind the panel, becomes a solar oven. Ground mount allows air circulation.
Have a secure structure that won't blow over and break them. Top secured to side of truck, bottom held but a strut the truck's tires are resting on?
Or a hanger at top edge of truck, strut holding out like an awning? From the ground you could lift a panel to hang on a hook. But first put gussets on the corners to tie frames together - they aren't secure.

If you can stow (and pad for safe transport) panels that are 1m x 2m x 40mm and deal with the weight, quality commercial framed panels would be good. We figure the large expanse of glass wasn't meant for mobile applications, but maybe sheets of bubble wrap filling the space between stacked panels would secure them against vibration.

A charge controller that accepts high voltage would let you connect many panels in series. If one fails, just remove it and keep operating with lower voltage.
 
This is what I was looking at:


2120x1052mm = 2.2 m2 @ 460W = 206W/m2

I'm not an expert on the actual chemistry... These are the panels I was planning on permanently attaching to the roof of the truck (I can fit 7 on I think)... There weight isn't too much of a concern and I need something to optimise durability and power/area.

With the mobile panels that will be stored in the garage and arranged on the ground around the truck... I want to optimise weight/power and thickness without too much of a compromise on power/area. Durability isn't that much of a concern because I'll have 10 or 20 of them and just stop using broken panels. I probably have a 2m x 1m x 0.3m space for storing these panels, so I'll take as many as I can squeeze in without damaging them.

I was thinking about just pegging them to the ground with tent pegs and maybe wooden stakes to raise one end... Simple solution without adding too much bulk.
 
2120x1052mm
We would guess having that bouncing up and down might put excessive stress on the cells. Consider bonding a few ribs on the underside to stiffen the glass.
Allow some room for air flow to keep them cool. Of course, flat means air stagnates. Heat will shorted life of the cell and deteriorate the backsheet which seals out humidity.

Panels are a thin glass laminate with a tall aluminum frame for rigidity. If you wanted to pack spares in the same volume, could remove the frames. A pair of those back to back would be as thick as 1x junction box + 2x laminate.

If frames were modified to be two edges toward back, two edges toward front, then they would nest together up to 5x as dense (depending on thickness of junction box). I think you could invert two sides to do that, then make custom corner pieces to span between front/back.
If frames were made sloped rather than right angle, they would nest like bowls. Don't know if that is available, though.
 
Yeah I haven't really started to think about how to mount the roof panels... and yes I'm expecting to have to add some sort of support structure and elevate them a bit...
 
... but I'm pretty sure that the panels attached to the roof won't be on any complex tilting or sliding structure. Too complex, too expensive and heavy to get right. Too much to go wrong... Plus the weight is all high up - not good for driving dynamics. Plus you can only extend these structures when you're stopped, so do you really gain that much over a simple stack of lightweight solar panels in the back that you put on the ground around the truck?
 
... but I'm pretty sure that the panels attached to the roof won't be on any complex tilting or sliding structure. Too complex, too expensive and heavy to get right. Too much to go wrong... Plus the weight is all high up - not good for driving dynamics. Plus you can only extend these structures when you're stopped, so do you really gain that much over a simple stack of lightweight solar panels in the back that you put on the ground around the truck?
Sounds like a weakness to me to be worked on. ?
 
Their 18 panels maybe 50 pounds each would be 900 pounds on the roof not counting added structure. Their application is for highway use.

I'm considering two rows of 3 on my roof rack, which extends from cab to front bumper.
Flat, 3 cover the other 3. Tilt up to the shape of a roof with East and West slopes, acute 60 degree angle between them.
Tilt whole thing to the front for seasonal tilt South. (would probably roll forward to balance point first, makes tilting easier. 350 pounds plus structure)

For you, I figured individual panels tilting up, could be done with struts accessible by stepladder on one side. Additional panels hanging down other side, tilt up as awning. Then move vehicle for 2 or 3 directions during the day.

Each individual panel could be tilted by itself with hinges on one end (you only have to lift half of 50 or 60 pounds). But tie the four sides of panel frame together better; just has a little screw joining them.

If they may get high winds on the face, may need stronger frame in the long direction. We usually mount on two rails about 25% and 75% of the way along the long edge, but use 3 rails for large panels in high wind areas.
 
I'm pretty sure even a simple manually operated tilting structure would add too much weight if it was strong enough to be totally stable in high winds and also secure enough when the truck is moving. Remember I have 14 square meters of panels - even a light gust of wind getting under that will be a huge dynamic load on the support structure. Reliability is absolutely critical on this build. I really don't want my silly tilting solar rig blowing away in the middle of the gobi desert.

Plus I'm really not looking for any more "custom" mechanical solutions... I already have enough work ahead of me on this build I don't want any more complexity.
 
I'm pretty sure even a simple manually operated tilting structure would add too much weight if it was strong enough to be totally stable in high winds and also secure enough when the truck is moving. Remember I have 14 square meters of panels - even a light gust of wind getting under that will be a huge dynamic load on the support structure. Reliability is absolutely critical on this build. I really don't want my silly tilting solar rig blowing away in the middle of the gobi desert.

Plus I'm really not looking for any more "custom" mechanical solutions... I already have enough work ahead of me on this build I don't want any more complexity.
Brute-force instead of adjustability: How many extra panels you would be able to mount to truck sides?
Panels are already enough cheap that on a project like yours it might be worthwhile just add more panels instead of complex, expensive and failure-prone tilting mechanisms.
 
panel roll out.png
For example....

SN-CIGS560W gives 560W at 1.3m wide and 2.6m long..... not sure what diameter you could roll it into, but for desert use, in a box would stop it getting dusty between usage. Dont know how much wattage you needed? Just a simple solution, nothing to complicated.
 
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