Demystifying (and Cutting to Size) Flexible Thin-film Solar Panels (Fuji F-Wave)

For the last 2 - 3 years you can find flexible thin-film solar panels quite cheaply (around 50-80euros per 100w) on the internet. The bulk of them are a solar panel called Fuji F-Wave 92W. The flexibility of this panel is amazing in such ways, that you can make a roll out it and treat it like a carpet (its nearly 3,5 meters long)

But there is a catch. Those 92W panels as they are sold, are not exactly usable by hobbists. The reason is the way they are packaged. Every solar carpet, has an open circuit voltage of 430V, and an operating voltage of 320V.

Even if we take into account the much more plausible Nominal Operating Cell Temperature -NOCT- (most of the soler panels you buy state only the ideal STC which you never reach, this panels produce "only" 300V when used (around 72W in real conditions).

There few electronics that can handle this voltages, and all of them are prohibitively expensive.

The reason these panels are packaged and marketed like that, is that they are very convenient for big installations. Installing 20 of this in parallel will give you "only" 4,7A of power for a total 1,4KWatts and that means thinner cables. In such condition buying an expensive inverter that can handle 400V becomes more plausible.

I had one of this panels for a year now but never found the time to play with it. Because in the back of my mind, my idea was to somehow tame the beast and make something hobby usable (or wearable) out of it. I can proudly state that this aim is now reached :)

take the plunge with me.

Step 1: Inspecting the Panel

Trying to find data about this panels is not an easy feat. The only technical specs, are here, and here in a pdf in japanese (but you can make some things from the numbers or the diagrams).

So the first thing one notices is that this solar panel is consisted from 4 seperate ones. Each one is 83cm long and 42cm wide. You can easily see the connecting tabbing wire. The company also states that these parts are easily cuttable. And yes thats the case if you use a sharp knife cutting through the plastic insulation. So we can seperate the panel into 4 parts and bring down the voltage to more manageable levels. Lets look what we can expect from one panel of (17.5Watt real conditions I dont state the standard one as they are non achievable)

Open circuit Voltage of 99,5V

Peak Operating Voltage of 74,5V

Peak Operating Current of 0,235A

things are looking much brighter indeed. But even these values are not exactly easy to manage in hobby level to make a USB or a car battery charger. There are ICs that can regulate down to 5V (USB) or 14V (car battery) (like the LM5008 ) , but thats not an easy feat, so I wanted to go further.

If you look on the technical data on their site, it states that each one of those 4 17,5Watt panels consists of 68different cells in series times 2 (in parallel), and that these cells are cuttable. Thats of course easier said than done. The whole panel is 0.2mm thick and most of this thickness comes from the plastic insulation. But dont dispair, after some experimentation I found an "easy" solution. But first lets get a better grasp how these cells are constructed

Step 2: Inspecting the Cells

I use the japanese diagram because it gives you a much better understanding.

So the blue part on the top is the positive pole but you cant access it as it is in the micrometer range. But the wholes in the middle of the blue part

Every cell has holes on it. These actually serve the purpose of connecting the very thin film (micrometers thin) to the connecting tab "wire" in the bottom. The holes in the center are for the positive, the ones in the edges for the negative.

Those amber lines you see is the film seperating the two cells, Thats where you cut. But be carefull. You can see amber lines from both sides of the panel, you have to chose the ones from the top. The amber lines on the bottom are seperating the "tabbing wire" from each cell and are not in the same position as the amber lines from the top. Every tabbing wire on the bottom rests between two cells and actually connects the middle holes from the one (positive) to the negative holes from the next cell (negative), thus in series connection.

So after you cut it carefully with a sharp knife, you have to seperate carefully the layers on both sides in order to get access to the negative and positive poles of your panel. You dont have to seperate the whole length, just a tiny bit is enough. Use a plastic knife in order not to scratch the amber film or the tabbing wire. The tabbing wire is so thin, that if you apply too much heat with the soldering gun, it will evaporate. I suggest using some tabbing wire for solar panels to connect the ends and not more than one-two seconds of heating :)

After that seal it back with silicone or hot glue and you are ready to go.

Step 3: Applications!

By cutting 16 cells together we can achieve . 17-18V x .10A
to .12A = around 2Watts (real life conditions) power. Now thats what I call manageable! By using an LM2596 board from aliexpress or ebay you can bring it down to 5V (USB power). You can also go higher and use 20cells (28V open circuit voltage, 20-22V peak operating voltage) and that means over 2Watts of power which will give you (after the conversion loses) around 2Watts (0,4A) USB power. Its not much but we are now talking about a very flexible panel 21x25cm :)

If you use both parallel panels (so 20cells x 2) you can get close to 1A of USB power for more hungry devices by having a foldable 44x25cm tube.

And if youd like to go small, you can use one of those boards based around the MP1584 IC.

During the next days I hope I will have some pictures from the first application :)

So I humbly declare this panel tamed :)

If you liked my instructable, consider voting me for the solar contest, I wouldnt mind having one of the solar bbqs at all :)

Comments

[cleanimageuk]

easy solution? just plug the output into an old laptop charger etc. mains 220-240v is rectified to 320-380v anyway so run the dc straight in, any polarity the diode bridge will sort it out. most smps handle 100v-260v ac anyway so good over a wide range of lighting. i have been running these for years like this. also found electric wheelchair chargers are designed to charge 24v bank and are dirt cheap and run from fwaves without modification

[masaka1978]

Can you please give more information on the laptop charger?? I have a bunch of old Laptop Chargers, i remember 2 of them from 17'' laptop so they might do the job better. I have 3 pair of those panels and use a 400V to 14V step down converter but i think it's broken now and doesn't output constant current, i am very disappointed with perfomance. Also, is it normal that those panels will suck if there is shade or even cloudy days? ( i mean by 90% less output) !? On summer time not much of a problem but i am thinking even remove them from my roof on winter cause here winter is strong and lot of windy! i just attached them on the roof with ropes!

[wasteoinc]

All laptop Chargers, or if you want , ALL switching power supplies have the same principle and can be used (theoretically) for this purpose.

A switching power supply after a few filters, transforms 220AC RMS to DC that is around 308Volts DC. If you connect the panel there the circuit will probably work and step down the voltage to what the power supply outputs.

Supposdly thin film panels perform better in cloudy days compared to other panels, but specifics have a lot to do with conditions, where the sun is , time of the year etc. So here in germany for example now on a cloudy day you don't get much more than 1300-1500 lux, so any panel wouldnt really work :)

sometimes a trick is to use it with the assumption of 10% load but that's ways to cope with what you have

[kkiiff]

having trouble soldering the joining tabs..i have carefully lifted the plastic over one of them, revealing aluminium tape. is there something solderable below. even the tape seems to be insulated.

[wasteoinc]

Hey, my main issue was that the aluminium like looking substrate is too thin and the soldering iron melts it too quickly , but that's where you need to solder. If you look at the picture this silvery layer is plus and minus alternating (so by cutting on the right size you have plus on one side and minus on the other :)

Tricks to make it easier is trying self-adhesive copper tape instead of soldering, or this silver conductive paste they sell on syringes, but I would try the copper tape first. I have already one at home but here in the winter there is not suffiecient sunlight to play around :)

[kkiiff]

thanks for getting back to me. i didnt want to cut the panels particularly, but i thought i could isolate them from each other by cutting those little grey tabs that seem to bridge the different segments. but my attempt to solder in this did not go well. the grey tab (revealed by lifting the plastic) seems to be aluminium coated in more plastic, under that, a stupidly thin foil, which i promptly burned through. couldnt get anything to stick.
after looking at your fotos, im thinking maybe i should, at least partially cut between the panels, in order to start the 'pealing' process.
i presume the grey tabs go from plus on one section, to the minus on the adjoining section ..not sure on how that works.

[wasteoinc]

exactly the grey tabs are both + , and - . If I remember correctly , the dots on the side are the plus and the dots in the middle the minus :)
So each grey section on the bottom (separated by the orange lines) is the connection between + and -. The cells are seperated with the lines on the top of the panel.

try the copper tape that I told you, it works quite well, the problem with soldering is that the nickel (what you call aluminum) is sooo thin that it dissolves with the heat from the soldering iron

[britishbedouincompany]

Hi I bought 25 of these panels and installed 10 on the roof of my motor-home with a morningstar mppt 600v charge controller. We live in Morocco and the panels performed very very well and we were able to run our house off the array. I am selling the motor-home and have considered splitting the panels into sections and connecting them in parallel and running them through a lower dc input voltage charge controller (that is also cheaper than the morningstar - £1200).

Well done on your project. It all looks great.

[wasteoinc]

yep, the controler was always the problem for these panels :)

Some people have managed to use a normal 220V AC switching power supply with these panels, the whole idea is that you connect your panel not in the 220V plug but a little bit further inside. The first job a 220V AC switching power supply does is filter and convert AC to DC. 220V RMS AC = 300-310 volt DC (you multiply AC with 1.4). Thats exactly what this panel gives as output. So if you connect two cables to the + - of the bridge rectifier inside the switching power supply and then connect these cables to your panel it will convert the 300V DC to whatever the switching power supply has (for example 19VDC if you use a laptop power supply). I havent tried it yet, but there are many switching power supplies around and you can easily sacrifice one :)

with the actual cutting of the panels I havent gone much further from last year, but I found out that trying to solder a cable on the very thin tin surface. its so thin that the whole thing melts very easily with the soldering gun. You manage it sometime but its very very easy to break from mechanical movements. For that reason I have bought a silver conducting glue to use to glue a cable on the surface and then make a hot glue blob in order to protect it from mechanical friction.

please drop a line with your results or what kind of controller you used :)

[HarryK39]

Hi, I found the technical specs at

http://www.americas.fujielectric.com/sites/default...

in English.

I'm hoping someone can help me. I want to take equipment to Indonesia from Uk so that my friend (an electrician) can set it up for me on a houseboat I'm getting built but would like someone to check I'll be buying the right things.

From what I've read on this page I think the equipment I want to take is a Fwave 92 panel (which can be cut into 4 pieces) and a solar charge controller

http://s.aliexpress.com/myUvAZjM

as suggested by Orngrimm.

I will also need to buy some connectors (MC4 ?) and I can buy a 12v car battery when I get to Indo because of the weight.

Does this sound ok ?

I assume I have to buy a lead-acid battery because the specs for the solar controller say lead-acid although I'd prefer to buy a lithium battery if possible mainly because kids will also be on the houseboat and I feel Lithium would be a safer option. Is it possible to use a Lithium battery with this solar controller ?

It sounds like I could take 2 panels if I wanted more power as long as they are cut up.

I can take 30Kg luggage with me so could buy a Lithium battery here if I knew what to buy.

Anything else I need ?

Apologies for my questions. I don't know much about electrical equipment and would really appreciate any advice anyone can give.

[wasteoinc]

hi, the tech specs from the fuji site are also in english and quite complete. its the diagrams and other details that are more helpfull in the japanese spec sheet.

anyhow you got the idea correctly. With 92 watt panel you get 4 parts that you can connect in parallel. Lead Acid batteries are your best option as lithium batteries are too expensive for the same capacity, and a little bit more complex in charging. dont be afraid about the lead in the batteries as it stays inside the battery.

the connections have to be a little bit self made. My best try until now is the flat tabbing wire , the thinner and more flexible the better. I will try self adhesive tinned copper tape in a few weeks, as soldering is very hard on these parts. I hope adhesive is less damaging to the wire in the bottom that its extremely thin and too much heat destroys it

hotglueing the exposed wires works well, but my best bet anyhow is to fix the cable on some surface together with the panel (like a small piece of dibond). the idea behind it is to secure the wire on something other than the very fragile solder connection

I hope this helps, in a week or two I will post my results from using it in small (20x20cm) solar panel settings

[HarryK39]

Hi wasteoinc,

yes, thanks for your reply and your explanations.

Now I can start ordering the equipment I need.

I look forward to reading your results, especially your views on the best method to connect the panels together

[Orngrimm]

one who is willing to use a 100v to 12v buck, could, with the Info's provided here, simply reconnect the 4 individual sub-panels in parallel and get the full power back at a lower violate and higher amperage...

didn't know they got this cheap by now. will buy a roll to experiment :)

[wasteoinc]

its those 320volt variety that is cheap. The rollable ones that are 33v or so still cost more than 150euros per ideal 100watt

[Orngrimm]

found those cheap maximum power point buck converter with 12, 24 and USB for 37$ shipped. the 400v types are much more expensive...
http://s.aliexpress.com/myUvAZjM
maybe a option worth trying...

[wasteoinc]

really nice catch orngrim. This way you can have 10s of panels in parallel without fiddling into switching power supplies. If you cut the panels in four 17.5watt pieces you have two extra advantages.

A. The whole panel needs no extra sealing

B. You have leads coming out of the panels so you don't need to delaminate and solder the thin cables n the panels. The leads are short but much more sturdy

[cuyler1]

i've been through this with the gadget guy on yt so i'll ask you. where can one purchase this material. and do not come back with i think someone sells it. i would like a link.

[wasteoinc]

hi cuyler1 . What is the yt?

These panels are doing the rounds in ebay for more than 2 years now. The reason few people buy them is that they are not particularly hobby friendly and inverters that accept 400V are expensive. This instructable has the aim to make them more accessible.

Most of the sellers I have seen are in UK, the netherlands and germany. Pollin.de has them for 55euros (just checked it, it says its finished you are unlucky because they had them for more than 2 years stably.

but if you search a bit more, like here 69 euros, or 670euros if you want 10 from the same seller

or here, (one unit)

or this other seller has lots, and also I see now that he has found a quite cheap controler that accepts 400V for 75 euros (the next cheaper I have found was more than 300). He says its custom made, there are people who suggested to feed the 320V on the bridge rectifier of a switching power supply (230V AC RMS = 320V DC), but I havent tried it myself yet (im not so confortable with switching power supplies, I just know how they generally work.

they pop up all the time, I dont know how , I dont know why , but they are here for some time now