flexible solar panels and UV protection

[AilSnail]

I found these: www.powerfilmsolar.com/

should work well for putting on a backpack - I haven't found out the efficiency of them yet.

The "weatherpro" series looks like they are laminated into some clear plastic. This is probably UV blocking plastic, as the other series panels are not "UV stabilised".

What sort of plastic can be used - normal laminating plastic for paper?

You see, I want to use the 4.8v panels for charging a single li-ion cell, and they don't come in the "weatherpro" version. The size of the 4.8v cells is also more convenient.

 

[VidPro]

the efficency is poor, on Most "flexable" plastic cells, i get about 50% in full sun, and they dont do much at all under clouds.
because they can only be flexed and not crunched, they get ruined when you roll them to tight, when they blow in the wind, or if they get crinkled.
often you see them rolled up showing that they are flexable, but the roll is carefully done , and never gets rolled to tightly (like 3-4" max)

because of that, they are best used in Folded configuarations, and not damaged when hiking :-(
all of the above is why i got stuck with high efficency GLASS non-flexable ones. it took to much Area, and there was not enough power in normal conditions, and it still needed a Frame to keep from damaging it.

so if you can fold it up in seperated sheets that is better.

UV plastic sprays, and UV laminations dont seem to provide for Full UV protection. have used them all, and sun damages still gets through a lot. but laminates, Vynal , will work on top of this stuff without much problem, and strengthen it a bit too. mabey its stopped the UV , but that doesnt stop the sun/light damage itself?
UV plastic sprays can not stick to most of the plastic stuff, and can be more diffusion than a laminate, either a heat lamination or a glue sheet lamination. you would loose 8-10% sticking 1 more hunk of plastic on top of them.

plastic cells have the lifetime of plastic , but when your just hiking that of course is not an issue, but i sure wouldnt try and buy into an array of this stuff for some 20 year payoff. glass breaks, plastic falls apart, aww what can you do :-(
in the trees and when the clouds hits is when the solar need gets higher, and plastic cells want Full straight on sun more than glass.

checkout the plastic or glass foldups that are already finished, the per cell price is similar to buying seperated cells. buy 2x as much area of sun collection for plastic cells vrses high efficency glass cells.

 

[AilSnail]

That was certainly a good answer, thanks!

Where do I find vynal laminate?

By 50% efficiency, I assume you mean 50% of normal, glass cells - since the best efficiency pv is around 20% I think.
EDIT: here is a quote from the powerfilm site, regarding the dismal efficiency:

Overall efficiency is strongly dependent on the module design configuration which determines the percentage of the area which is actually collecting sunlight. You can use 5% as a starting point. We have ongoing research and development programs to continue to improve the efficiency of PowerFilm modules. Note: There are widely varying standards for module efficiency numbers. We encourage you to test actual commercially manufactured modules on a consistent basis.

A frame should be easy to make strong and light from carbon.
Easier if each cell is small, since it doesn't have to be as strong then.

I'll think about it some more.

 

[shadowjk]

<deleted>

 

[VidPro]

That was certainly a good answer, thanks!

Where do I find vynal laminate?

By 50% efficiency, I assume you mean 50% of normal, glass cells - since the best efficiency pv is around 20% I think.
EDIT: here is a quote from the powerfilm site, regarding the dismal efficiency:

A frame should be easy to make strong and light from carbon.
Easier if each cell is small, since it doesn't have to be as strong then.

I'll think about it some more.

yes 50% of the already poor efficency of glass ones
but specifically in tests, 50% of Wonderfull high quality glass ones, as compared to wonderfully high quality plastic ones.
i tried to get the best sized powered things of both, plastic was 50% less when used. and worse when cloudy. (per square foot)

i dont know where to get vinyl laminate, vinyl will "static" adhere to things, that is what they call it. if you get nice soft new fresh vinyl at the wallymart or craft shop, it just gooshes onto things, and sticks.

i would certannly be interested in anything you get working with the Lightweight plastic cells, because they are awesomly lite, and i would like to switch my backpack system to them somehow. mine weighs 10oz and paperthin plastic cells with light frame could have come in at 5oz or less, but was to large in Size for the excessive power i wanted.

so be sure to get pictures

 

[AilSnail]

Pictures: that goes for you to, please.
10 oz, how large is that? And what sort of amount of energy can you get from it during a day of walking(/whatever you do), in what conditions?

My mother has got a 16.7% efficient Sunpower panel on the cabin. It is rated 95 w which becomes 172w/sqm. I heard this is one of the most efficient available, for such use? The cells aren't very thick, I'd hazard a couple mm, but I can't get them separately.

The powerfilm is then 39w/sqm from my spreadsheet - 4% eff.

I found these Super Solar Cells, "same as in space industry", no specs on eff. or weight - but I calculate 125watt/sqm - and they are very thin, 0,36mm! I think these would be worth a try, if I can find nothing better - but they are rather dear. And I don't know if they'd need any coating or laminate or such.

 

[VidPro]

i cant find the actual site that had the good pics :-( and was the primary souce of them, because i bought knock off ones that were supposed to have 10% less total power, i only needed 1/2 so i figured one of the halves would be good.

these look and sound like the exact same items
http://www.radiolabs.com/products/electronics/power/solar-panel.php

they are on fiberglass backs with epoxy topped the base of it looks exactally like "PCB" materials, and they will break if abused, i abused mine and its got hairline fractures in it.
Glass cells are thin less than 1mm "wafers" , then they have to be put in a frame, and the frame style type was the concideration of weight, aluminum backed.

i will just put up the pics already
Captions are Below the picture

a Motly assortment of broken some usable Glass cells of about 12-13% efficiency claim
each unit is .5V and outputs about 3amps, they are 6"x3" they sell for about 50c a watt, and cost about $2 a watt after you sort the broken pile of junk they give you. the busted junk is usable still, but not worth dealing with imo.
this pic is to just show how thin and breakable they are in thier initial single cell item start.

there is a paper reciept on top there, and attempts to show how thin they are in comparison

this is the weight of about 3.5 of those, in thier raw state that is Point .9 oz

this is them paper thin plastic things, 9.5" x 3" each, 2 assembled together to attempt to make the lightests foldup i could make that had some usable power, you can see it flexing in the light .9ozes total

this here is it folding up, EVEN the end connections on these are metalicized plastic
i was able to get solder to hold, but aparentally it didnt hold over time?
i donno but they have Edge Clips for this stuff instead of soldered connections
i can imagine how a clip would hold up under movements if it wasnt done right

this could charge 4X ni-mhy just fine given enough time, if you can give it enough sun, and heck it dont weigh a oz yet.

this is the next stage i went to, from the paper thin, when i decided i would need to many square feet of paper thin for mobile sun grabbing
this is a high efficency probably 13% Aluminum backed Epoxy topped, with screw connects
i think this does some 225ma at 7.5v max, intended for 6V charging. (check specs at link)

its 4.5"X 8.5 inches weighs about 6oz.
this i actually installed, and you will see the instalation need I wanted to fufill and know why.
you can drop this toss it, play frisbee with it, you just cant heavily impact it,
anything that would bend the aluminum/epoxy, would break the glass
this one i dont use, it might be good for charging 4x ni-mhy, but i needed WAY more power


continued next post

 

[VidPro]

this is 1/2 of an expedition fibrerglass epoxy with some of the highest efficency cells you can get , other than round ones, and they loose to much space because round things dont fit into square holes

originally it was in a light blue nylon container, with a hunk of cardboard it was riveted to, the cardboard would be on the outside when folded and zipped up, keeping impacts down.
I failed to understand what the heck good a solar cells is, folded up with its teammate in the DARK but such it how it was built.

of course i just needed one of the 2.
originally designed for 12V charging or adapting from.

it is 8"x11" and can be trimmed to about 10.7" with bandsaw

the wiring (thank gawd) was on the back of the unit in PCB foils.
remember each pannel is designed for 6V charging some 7.5-8v or something? 1/2 of the 12v.
i wanted to charge li-ion with as much amps, and the least losses of conversion, so i halved the voltage again, and split the connecting foil on the back, as seen later. so 1/2 the voltage 2x the amps.

and that is the thing i presentally use. (really i do, just last month, i have no idea how it got that dusty) .
this is it on the External frame backpack, a Jansport D with special center weight hip belt (ok its complicated).

here is the back, and the wiring and the mount, that wire is solid copper, and it just turns the series pannel into parellel.
the wires that lead off, to the breakaway connector, are stranded copper so they will flex more.

sew-on velcro was Glued on, because adhesive velcro is useless, especially in the heat.
the velcro allows it to "breakaway" so it lands safely if i die , , , hey wait a minute :huh: also the wires are on a connector that will breakaway.
i can also pull it off the backpack and put it around the tent.

the original diode was tossed in the garbage, and a Shotkey low-voltage dropping diode was put in its place.

the mount is something i found at the hardware store, its a conduient holder, then i just added a aluminum strip, with a curved ketch at the far end. the curved end locks the pannel under, most of the pressure is on the whole velcroed strip
the mount was originally designed for the small aluminum backed cell.

this will do some 24* movement from side to side, and 200* front to back, just barely enough for all sun locations.

Max charging power (vrses any useless max power of the unit) is about 1.6-2Amps for parelel li-ion, battery voltage dependant, that way when the li-ions get more charged , it tapers off just like specs for charging the battery, if the battery is low, then it charges faster. self regulated with cutoff.
the item is connected through a protection cutoff, and a switch with led that shows output functional. (more complications)

you should be able to see the hairline fracturing in this picture, fractures effect solar cells when they disconnect the silicoln wafer areas gridded out, from the wiring that pulls the power off to use. so fractures can be zero change, or a percentage of change based on the quantity of cell removed from the curcuit.
this one is still running at 90% with all the fractures you can see there.

i intend to replace it with the other half, as it has been beat to heck.

and what good would a backpack solar be without picture OUT there , where one could be instead of making solar junk

messing around at the BLM

 

[AilSnail]

wow, speechless. Seems you've done most of the work for me in trying out the panels, and what a nice looking place. Are the hairline fractures due to bending or to impacts to the cells themselves, you think?

Here is what I think I will try: one layer of 100-150g/m^2 carbon (if I can bloody find it!), each side of a 2-3mm 80kg/m^3 foam or balsa. With 50/50 epoxy/carbon (vacuum table - fridge pump), the backing plate becomes from 560 to 840 g/m^2. Since yours is 11"*8"=0,06m^2, that would be from 32g to 48g.

I don't use an external frame pack usually (only above 15kg or with lots of bulk), so I would make the panel(s) about 15x15cm, with holes in the corners, and tie them to the pack. When they are small they are less bendable.

Far as I understand the peak power/rated power is measured when the sun shines 1000w onto one m^2. Thus a 150w/m^2 panel is 15% efficient.

I built a tiny charger that I think I will use, the chip is TI bq2420x, "single cell li-ion charger for current limited applications" - 500mA. Not sure if this will be less efficient than using a schottky - there is only a FET in the power path - but I want idiot proof.
I want to charge one 18650 and one AAA per day, at least, so I need around 10wh/day. The days are short and dark now. The charger bodies will be something called "Cohglan (sp?) waterproof matchbox" which I bought at REI for 1$/pc, which fits an 18650 perfectly.

What I need is a larger overview of available cells - if you have more links I would be thankful. I'd go with the Super Cells but for the price - they are probably super light - but with only 12,5% eff there may be better alternatives still. It seems risky to buy an assembly, since it may be impossible to get the backing plate off.
I also need lightweight water resistant/non corroding plugs/sockets.

I will also think a bit more about using reflective film (mylar?) to increase the yield when stationary.

 

[AilSnail]

I went over the numbers you gave. I think that the motley assembly with the broken pieces seem nice. 640g/sqm & 13% eff, that could go around.
Where can I get such? Would it be difficult to split them to make a panel with higher V and less A? Or do I need to put there a boost converter as well?

 

[VidPro]

yes the fractures came about when i impacted the pannel, with large branches, and when the pack swung down from standing upright to flopped on its side.

i was thinking about using carbon fiber rods to make a frame, carbon fiber bends a lot, but does not break, and weighs nothing, that would have been good for the plastic cells.

Links duh, that is where the pannels are, gosh i should have looked there first. some links:
http://www.ctsolar.com/index.asp
http://www.solar-world.com/batterychargers.htm
http://www.siliconsolar.com/diy-solar-panel-kits.php
http://windandsunpower.com/store/
http://www.fieldlines.com/section/__all__
this is a motly assortement of links

i got the specs wrong on the aluminum backed one
http://www.solar-world.com/SolarPanels.htm
get the specs from there instead, those are the styles.
they would work very good for small quantities like 1 li-ion or 4 AAAs or something.

reflecting light back to the pannel, instead of moving it works good, like solar oven, depending on configuration of cells, you MUST hit all cells to get amps, meaning shadows that cut across a whole cell in a Series pannel will wipe the whole pannel from output.
then you still end up with the KITE problem, lightweight and large and a light breeze.

glass cells are literally thin glass, and break if you even drop them, they are so thin and fragile, that even plastic frames and wood frames (expanding and contracting seasonally) can break them.
they can be split in half exactally like your saying , to get 1/2 the amperage, and as long as the electricity collector is on them, there is no other loss than the ammount removed or split. split items can then be placed in series for higher voltages.
some amatures Can split glass cells with glass cutting methods, myself i can not at all without blowing it to pieces, but lots of the places you buy from will do that for you on special order. that is one way to get the "Best Cell" in the right size.

mosfets and fets with lower resistance can definatly be used to make lower voltage dropping diodes, as long as the gate trigger voltage is met on the silicoln device. the backwards draw from un-lighted pannels is not that high anyways, its about 10% or something, it exists, but its not terrible.
the funny thing about that is most of the Very high end controllers, ALREADY have rectifications in them, so many huge arrarys are wasting power with diodes in the pannel, and rectification in other areas too.
Then of course there is Jump past a cell or past a pannel when its shadowed dioding, where the diode allows the rest of the items (in series) to continue when one is broken damaged or not getting any sun.

and one more, the voltage does not change when you get clouds and such, the voltage on solar cell items is very stable, the amperage is what changes, so the voltage only has to be higher than the battery by a fair ammount. having Huge voltages over the battery voltage, are wastefull. there is points of deminishing returns in that. you must have some voltage differentials, like say 20% over the battery to get flow from the differential, but 2X the voltage of the battery is wastefull. that is why i rewired the cell.

i had to get 5times the ammount of power in solar than my use need, because i wanted to use power at night, because of clouds and trees, and because days could go by without adequite sun power, along with that i had to have 3 times the initial storage that the device had (a PDA) to be able to charge quick when i had sun, and operate when there was not adequite charge.
my "pay off" period comes some 4 DAYS after being out there, vrses just carrying some 10amps of li-poly cells, because of the weight of the contraption, wires included comming in at 11oz. pay-off would be much quicker with something lighter.

 

[AilSnail]

What do you think, how many 0.55v cells do I need to charge a li-ion? the charger has a 0.3v dropout so on shady days it should stay above 4.5v.