Solar panel making questions

Firstly I express my greeting to all the active forum members!
I just dropped in to start a discussion about how to make a solar panel from "the cheep 3x6 cells", so it is not as neat as industrial one, but still a good quality and reliable. I presume, there is nothing wrong about those string ribbon solar cells themselves and the problem is about packing them properly. I do know, they are rated 14% efficient, not 16%, but that is not that much.

At this point many questions pop up about the elements, I go through them and please feel free to advice and comment:

1. I would use window glass on the top layer, because it is freely available, scratch resistant and should be able to tolerate hail too,
2. aluminum frame, that can seal the plates into it and has bonds between the sides,
3. X back plate,
4. Y sealant for fixing cells, eliminating condensation and lower reflection losses,
5. same sealant for the frame.

As I know it, industrial panels are laminated, but that requires special lamination machine, which is too much at the moment (still makes me interested about how it works - how can cell cracking be avoided for example). So I would prefer to do it the same old way with silicone. I found, that there was 2 part silicone used once, so it could heal up being confined.

If there are no other advices from your part, I would like to know about what is X and Y! If I use some polycarbonate like in http://www.buvplastikati.lv/pc.html it might be too insulating. If I use a second plate of glass, it might be too fragile.
And about the sealant - maybe there is some known to fit and proven to hold all weather conditions and stay clear and soft?
Any ideas?

Finally I am curious about the thermal coefficients of silicones and laminates: are they close to those of silicon cells or they are sufficiently elastic?

Hope there are people out there, who may help this out... Note, that I can't transport those solar panels to where I am and it looks better to make them from components...

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Solar panel making questions

    Here are some thread with information on building solar panels:

    Thread 1
    Thread 2 (information/video on commercial panel production)

    User "Brenneis" is currently trying to build his own panels (~200 watt).

    Vacuum sealing solar panels
    Casting solar panels in composite material
    DIY solar panels

    You might try posting in one of his threads and/or using PM with Brenneis and see where he is at on his project for a ~200 watt panel (I know he has it soldered together, and working--not sure about the glass/sealing).

    Since solar panels are "so dear" / hard to get where you are at (Latvia?), you would probably want to make a solar tracker for your panels (homemade or store bought) as this will increase their output by quite a bit.

    The electronics are available in kit form (see this thread for some information) and you might find old C-Band (large) satilite dish/frames to convert for your needs.

    To be honest, most people here (including me) spend more time trying to convince people not to build their own panels as it is expensive and difficult (modern solar cells can be extremely thin and are very difficult to separate and handle without breaking). As well as almost impossible to seal against weather.

    I saw one person (don't remember link) that had to place a stack of cells in some sort of liquid (alcohol or water????) and almost float the cells apart.

    If you need "solar power" to save money/fuel--solar thermal (hot water, hot air) projects are much better suited to do-it-yourself projects.

    If you need electricity from PV cells--you are pretty much up the river without a paddle with homemade solar panels.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • brenneis
    brenneis Solar Expert Posts: 34
    Re: Solar panel making questions

    I can tell you, it is not as easy as I thought it would be, I have decided to make it a long term project building them as I have time in my basement because I want them to last and do it right. After many trials and error I have come up with the following that seems to work the best. I ordered plexiglass online as it was not that much more expensive than glass and easier to work with. I had them cut it to about an inch and a half over around all sides. Make sure you lay out the cells and solder the first panel first before measuring as you need space between cells. I used small ceramic tile spacers nailed down to a piece of dryway as my template. I set each cell between the spacers and end up with a very nice layout.

    I am using plexiglass for both the front and the back in a sandwich. Building a weatherproof aluminum frame is not that easy and I was not happy with how waterproof it would be if I used wood as a backing, plus over time wood warps in weather. Put a blob if silicone on the back of each cell then place your first piece of plexiglass on it and press lightly. Having it clear at this point really helps to get all the edges where you want them. The silicone does not dry right away so you can kind of slide it around a little to get it right. Let dry and flip over carefully.

    I then ran 1/4 inch plumbers vinyl tubing around the edge leaving about 1/8 inch of the plexi hanging over the tubing and left a gap at the bottom and stuck about an inch long piece of tubing perpendicular to the other tubing and extending out a little off the bottom as an air vent. I used plumbers silicone plastic glue for the tubing (goop). I tried with holes, bolts and screws but it was a pain and did not give me a clean finished look. The glue with big binder clips to set works great and gives a strong hold. Plus is flexible and weather and UV resistant. I then glued two of the tile spacers together to make a set of nine and layed and glued them in the panel at even spacing in between the gap that was already there to be even with the top of the tubing and act as support for the top sheet. Ensure you rough the edges of the plexiglass for good hold on the glue. I drilled a hole ran my wires and soldered leaving one small hole in the back with wires protruding and siliconed it in. Ran glue again around all edges and little on the spacers and lay other sheet on top. I used left over marble tile as weights on the whole thing to ensure a tight fit. Last step is I ran silicone around the whole thing in the 1/8 inch space I mentioned above and smoothed flush with a latex glove. You end up with a nice thin sandwich between to plexiglass pieces and a smoth weather proof edge.

    Now understand that the whole panel is still flexible at this point and not ideal for mounting. I had home depot cut me pieces of thick plywood equal to the size of 3 of my panels side by side with a little extra. Drilled 3 holes in the plywood directly under where they come out of the plexiglass so when you mount they lay perfectly flush. Each one was bolted down with corner brackets for a tight fit. Ensure you paint the plywood or protect it somehow. The color shows all the way through the glass of course and gives a real nice look. At this point it is easy to work with junction boxes on the back of the plywood and connect them all together. Ensure you read all about bypass diodes and the wiring needed. Most of the online help stuff shows one panel connected to a battery. It is different if you plan on connecting several panels together in a grid tie. I had dreams of building enough of these to cover my roof, but they take a long time at first. Much faster when you get the hang of it. Hope this helps....send me a message if you have any questions. Brian
  • KarlisRepsons
    KarlisRepsons Registered Users Posts: 8
    Re: Solar panel making questions

    I would be glad to see some as much detailed information as possible on panel making, that is "semi-serious" or industrial. Basically I want to know about the material and process regarding my X and Y...
    Certainly, industrial panels are currently hard to reach for start-up maker, but the economical situation in Latvia is pretty bad now and if only there is a way to actually make reliable panels, it would be beneficial to make locally as much as possible. Also its a complete silence about them over in here - local energy monopoly and gov pretends, they don't exist!
  • brenneis
    brenneis Solar Expert Posts: 34
    Re: Solar panel making questions

    I also want to point out that these are NOT on my roof.....they are mounted to an old shed....I have no idea if my materials would pass building code but I would not put them on my house. I would only put professionally made solar panels purchased from Arizona wind and sun on my house....how you like that plug Bill
  • brenneis
    brenneis Solar Expert Posts: 34
    Re: Solar panel making questions

    so are you saying my work is not semi-serious....LOL....they work great...
  • KarlisRepsons
    KarlisRepsons Registered Users Posts: 8
    Re: Solar panel making questions

    Easy, your message was not visible for me when I started to write the next post!
    I still have to read it through one more time and think about it a little more, but right now I have a thought about that silicone - it was one component silicone, right? And what is between the cell and the top plexiglass?
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar panel making questions

    plexiglass is not a good choice for solar as it will not pass light as well as glass and it gets worse in time.
  • brenneis
    brenneis Solar Expert Posts: 34
    Re: Solar panel making questions

    I did not know that....the glass I bought is crystal clear, I made sure of that..it looks like a window pane........can't see how it would be a problem.......and here i thought I was good to go, now you got me paranoid....they are conducting well within spec right now..??
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Solar panel making questions

    UV light breaks down plexiglass and many other plastics. Plexiglass will have noticeable clouding in a matter of months in direct, hot sun,, and will yellow quite quickly. Also it begins to loose some of it's strength, and becomes more brittle.

    Tony
  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    Re: Solar panel making questions

    How about that: sand instead of oil. SiO2 for glass or Si crystals for semiconductors (doped of course) or PV! Good stuff and abundant. Was that crystalline structure face centered or body centered? I can't remember. Is glass affected at all by UV? Just for for fun and... post count ;)

    Craig
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Solar panel making questions

    http://www.polymerplastics.com/transparents_lexan.shtml

    "Lexan XL is a solar grade sheet which provides superior UV resistance in addition to offering high thermal insulation values. Applications for Lexan XL include skylights, space enclosures, covered walkways, and sloped and vertical glazing. "
  • brenneis
    brenneis Solar Expert Posts: 34
    Re: Solar panel making questions

    well, now that I already got some of them made and don't want to change out, is there any reason I can't coat the plexiglass with several coats of clear UV protectant?? will that prevent the yellowing?? That would be first choice.....any recommendations on product to use if so??

    Second choice, any reason I can't keep the plexiglass on the bottom and just replace the top sheet with real glass....I can reuse the top for another bottom anyway?? Shoud it be tempered or will regular glass work...any specifics that you recommend....thanks Brian
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Solar panel making questions
    dwh wrote: »
    http://www.polymerplastics.com/transparents_lexan.shtml

    "Lexan XL is a solar grade sheet which provides superior UV resistance in addition to offering high thermal insulation values. Applications for Lexan XL include skylights, space enclosures, covered walkways, and sloped and vertical glazing. "

    Lexan is NOT plexiglass

    UV resistance, is not UV proof.

    Low iron glass will last much longer, and seal better, lexan has pores which leak air and water (nearly all plastics do)
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • brenneis
    brenneis Solar Expert Posts: 34
    Re: Solar panel making questions

    check out this stuff guys,,, any thoughts they even have a demo with exactly what I am 1/4 inch plexi..

    is it just the light that makes the power, or is it UV or infared rays?? what
    properties should a mertial idealy have for solar panel covers??


    http://www.myboatstore.com/aerospaceprotectant.asp
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Solar panel making questions

    As MIke says,, Lexan is not plexiglass.

    It is BETTER in fending off the effects of UV,, but it will cloud and change over time,, something on the order of 3-5 years depending on climate. Glass (any sort) has no degradation over time,,, that I know of.

    T
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Solar panel making questions

    Glass will probably have a closer match to the thermal expansion properties of the silicon solar cells...

    Glass on top and "plastic of some sort" on the bottom is probably OK if you do not attempt to firmly bond the glass to cell to plastic with a "hard" adheseve (such as expoxy, super glue, etc.).

    Attaching the cell to one surface (back surface, not front where will block more light?) with silicon or other flexible adhesive is probably OK. Attaching the glass to plastic backing only at the edges is about the best you can do.

    Problem is that most adhesives out-gas and many involve water/moisture in their curing (at least one parts would). So getting the "ideal" hermetic seal is difficult or impossible.

    And, I will post a link to the "panel fire" thread again... :roll: . (and thank you again to "Sundiego" for posting this information).

    DSC_2689.jpg

    DSC_2696.jpg

    DSC_2699.jpg
    Take a look at this closeup of a "good panel". These panels where of "plastic" construction and show a lifting of the copper foil buses.

    My guess is that panel flexing (panels where not properly mounted and allowed flexing in wind/sun) and/or differential expansion (between plastic, cells, and copper foil) "helped" cause the foil to eventually lift (and possibly the failure led to the fire).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • brenneis
    brenneis Solar Expert Posts: 34
    Re: Solar panel making questions

    From the close up bill, it looks like whoever made this firmly sealed the cells to the plastic backing not allowing for expansion and contraction. I affixed my cells just with a little blob of silicon in the middle of the cell only??

    I have the top glued to the edges only with a flexible tubing as a buffer and no glue anywhere from top to cells or in the middle anywhere. I left the glue and tubing about 1/8 inch inside the panel edge and then smoothed silicone around the whole thing except for a vent hole flush with the edges for a better seal. Like you said, I think the concept is sound and about as good as I could do.....I am going to try the UV protectant and see if it stands up.....I guess I can always swap out with glass later
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Solar panel making questions

    By the way--the above failures of bus connections were after about 1 week of exposure to sun and rain (and possible handling issues).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • KarlisRepsons
    KarlisRepsons Registered Users Posts: 8
    Re: Solar panel making questions

    So nobody considers filling the tiny gap between front glass and cell?
    Industrial panels are laminated at least to attach cells to the front glass... Just I can't figure out how that happens such a way, bubbles are not overly present into the sandwich.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Solar panel making questions

    If you look at one of the videos in the thread I posted earlier--they lay down the glass, then a film (probably something like polyvinyl butyral (PVB) which is used to make laminated/safety glass), then the cells, and lastly the backing.

    Put it in a vacuum oven to bake/seal (80C in the video).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • KarlisRepsons
    KarlisRepsons Registered Users Posts: 8
    Re: Solar panel making questions

    Thanks... Just I regret, youtube doesn't allow downloading the file (or I missed something?). It doesn't work for me as I have no flash player in my 64bit linux.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Solar panel making questions

    If you search around, you should be able to find a downloader/converter/player for linux (one article here).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Solar panel making questions
    Thanks... Just I regret, youtube doesn't allow downloading the file (or I missed something?). It doesn't work for me as I have no flash player in my 64bit linux.

    Mozilla Add-ons should have a d/l that will work.

    Flash 9 on 64-bit linux (requires 32-bit Mozilla):

    http://www.darronschall.com/weblog/2007/02/installing-flash-player-9-on-64-bit-linux.cfm
  • KarlisRepsons
    KarlisRepsons Registered Users Posts: 8
    Re: Solar panel making questions

    Ok, I found my solution for that.
    The video is quite short, but now I understand the basics of lamination. It might work without vacuum too... But its just "might".
  • brenneis
    brenneis Solar Expert Posts: 34
    Re: Solar panel making questions

    if you figure it out let me know...I tried vaccuum sealing mine with my food saver LOL....it worked for about a day and then the vaccuum leaked....
  • KarlisRepsons
    KarlisRepsons Registered Users Posts: 8
    Re: Solar panel making questions

    There is one more important thing to ask and you might know it: how is the back side of PV cells made? They are laminated in and then? What material / composition is used for the back plate?