Author Topic: Making decent solar panels part 3  (Read 84072 times)

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oztules

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Making decent solar panels part 3
« on: February 14, 2011, 05:37:25 AM »
Well it's time to ramp it up a bit. Yesterday I attempted to show how simple it is to work with the EVA, and make a single cell panel with very little tools at all..... cardboard oven etc.

Today I needed to build a new 250watt panel, so I tried to photograph it as I went..... but forgot to use the camera as much as I would haver liked. You just forget that people may not know how to do some things that I take for granted, and so gloss over it.... eg how to build a 2.5m*2m plastic bag at a moments notice etc.

I will take it as read that we know how to tab cells, (youtube does this well). Once tabbed we are ready to begin..... first we need the glass.

In this case we will be using the iron free solar glass from a disused hot water panel. It is toughened, and the iron free...... this means when you should get 1.8w per cell you will. If you use window glass, then it will be less, but work anyway.

So we get the glass and wash it in water and dry thoroughly. Then wash the cell side with methylated spirits and dry. My glass looked like this:


I won't attempt to detail the cell joining process as it is just soldering cells together, and this too is covered well elsewhere. Suffice to say, keep as much room between cells as your design and glass size can afford... I like 1/4 inch, but never get that luxury. In this case I need 23 cells in a single string to fit in the glass with an inch left at each end. This dictates very close spacing between cells, and can lead to shorts if not careful.

I also use the solar hot water case as a straight edge to build the string in. I use transformer paper on top of the aluminium, and use the side of the case as the straight edge. This way guarantees that the cells don't wander about the place.
It looks like this:




We then carefully (very) pick it up and transfer it to the glass sheet which has the EVA cut to size on it I use some untabbed cells to get the spacial arrangement to make it look symmetrical   not very well really, but i did try a little bit.



We keep laboring away until we fill the glass up with cell strings. We then need to place the bus lines in to join the strings. There was not a lot of room to do this here, so I actually placed the output tabs on top of the last cells in the string in some places. I use transformer paper to effect the isolation needed, and EVA strips between any surfaces, so that the whole lot will melt together later. It may be seen here:



From a "looks" point of view, it is more important to get the strings straight, and the gap between strings even. The inter cell gaps in a single string seem to have little impact visually compared to these other two requirements. I see a lot of youtube folks with tile spacers to try to get it right, and they still fail miserably.... so just keep the lines straight, and even between strings and it will look ok. .... I think anyway.

Then it's time to place your second sheet of EVA on the pile. Hopefully you remember to cut it before we get to this point.... unlike me.


Then it's time for the backing material (tyvek for me, whatever else for you).


Later I turned the sheet over ...... with mixed results. It wrecks the visual impact because of the blue and red wirting.... ahh well.

Now the next part is critical to success..... yes the plastic bag and wicking material

2.5m x 1.5m plastic bags don't grow on trees over here, so we need to build our own easily and quickly.... and it MUST be airtight.

I did have a roll of plastic sheet donated from a farmer. It was 2m wide and a million meters long.... so I cut off 2x 2.5M bits of it and laid then  on the table one on top of the other.... Now we just need to seam them. We can use a straight edge.... for no other reason than to limit the damage we are about to do.

Place the straight edge about 1" in from the edge of the 2 pieces of plastic laying on the table. Grab the heat gun, and heat the plastic edge, running up and down the straight edge quite quickly. The plastic will start to melt in that 1" zone. Move the straight edge onto the 1" melted zone, and it will cool it rapidly, and seal that zone..... like this:


We then end up with a huge plastic bag, with very little effort. We can seal the open end after we place the cell inside of it.

Here is my plastic bag:


Last time I used shade cloth for the air wick material, this time I found an old dooner, which will allow for reasonably free air movement. This is key to no bubbles... as well as no leaks in the bag. Shade cloth shrinks with the heat and distorts the cell layout, the dooner did not... yippee.

Bagged up, and the vacuum starting to take up the slack, we get to this:


We can see how I have sealed the end of the bag now, and placed the vacuum hose into the dooner cloth. It's all starting to happen about now.


and nearing vacuum condition, the dooner is now flat as a pancake:


Here is a closeup of the hose going into the cloth:


Now we have to maneuver it into the oven


The whole lot was under vacuum for about 15 mins before I started the heater. It slowly climbed up to 105 degrees or so, and so I ran it for 70 mins... better more than less, or glass adhesion may not be complete.... and thats it.

There is nothing more that can be done now.... but wait... and wait.

After about 70 mins, I turn off the heater, pull back the lid of the oven, and let it cool off.

Before it gets too cool, it is wise to get it out onto the table and undress it.... the EVA runs where ever it can, and some may stick to things you don't want it to stick to (the dooner for one)... so rip off the plastic and free the dooner as soon as practical. The eva will still be a bit soft at this stage, and you can remove some from the edge or whatever. When it cools and the curing is finished.... nothing is easy with it. It is tough stuff.

Like I mentioned earlier, I may ditch the tyvek altogether, and use grease proof paper, and try to just get the eva on the back. It needs no protection at all in my application, the solar water jacket protects the rear of the cells from pointy objects, and the EVA  is water resistant, uv and everything else resistant. Open panels may need protection .... although I can't really see what from.

This software can't handle more than this, so I will continue with a comment to keep it all together


...........oztules
« Last Edit: February 14, 2011, 06:26:46 AM by ghurd »
Flinders Island Australia

oztules

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Re: Making real solar panels part 3
« Reply #1 on: February 14, 2011, 05:45:21 AM »

So we have our panel and it looks like this


and this

Up close like this:


When placed back into it's frame/jacket it's like this.... fairly respectable really


and the rear like this.


It really is a big panel, and I don't think there is much point going bigger. This one does about 250 watts. It's max power V is at 34.5v, and max power I is at 7.5A
Short circuit current is at 8.3A and open circuit voltage is 40.5.

It will be used as a water pumping panel with V set at 32v and current whatever it can do according to the sun... hopefully lots of 7.5A would be good. This will derate it to about 240W

only another 20 to go.....




Yes I know the tyvek writing makes it look bad, but apart from that it is a very successful panel.

I hope this inspires some folks to have a go now that there is a way to mimic the big boys without the fuss.




Not bad for a days work I guess.



................oztules
« Last Edit: February 14, 2011, 06:03:06 AM by oztules »
Flinders Island Australia

DamonHD

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Re: Making real solar panels part 3
« Reply #2 on: February 14, 2011, 05:52:21 AM »
Excellent write-up!

I'm beginning to think that you might not be *completely* mad to DIY!

Rgds

Damon

oztules

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Re: Making real solar panels part 3
« Reply #3 on: February 14, 2011, 06:01:42 AM »
No Damon..... your gut instinct is probably correct..... I am completely mad



...........oztules
Flinders Island Australia

Harold in CR

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Re: Making real solar panels part 3
« Reply #4 on: February 14, 2011, 06:29:42 AM »

 You may be completely mad, but, that's one damn fine looking Giant sized panel. You Sir, are a craftsman.  8) 8) 8)

 Question= What's a Dooner ??  That be a Blanket for sleeping under ??

 I'm thinking maybe a Fibreglass Matte material. It might stick to the EVA, and I can spread Resin thinly over the open side, after cooking the panel. Not sure what might exist here for protecting the "Dooner" stuff.

  Really great Tutorial. Thank You very much for doing this and posting it.    Harold

Volvo farmer

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Re: Making decent solar panels part 3
« Reply #5 on: February 14, 2011, 06:39:38 AM »
Excellent write up.

Do I understand this correctly? You are sandwiching the cells between layers of EVA?

So it goes glass-eva-cells-eva-tyvek?

Also, I wonder if you wouldn't rather have the back side of that panel open to the air where it can cool off in the breeze, rather than in the still air of the tin box.

Lastly, isn't the industry standard 72 cells for a 24V nominal battery? You have 69? I realize you aren't using these for battery charging, but if you were, I would think that extra volt and a half might be useful, especially in a hot climate.

Pretty impressive work. The best I have ever seen!




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oztules

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Re: Making decent solar panels part 3
« Reply #6 on: February 14, 2011, 07:11:43 AM »
Harold,
this is a dooner


I'm not sure why you think it necessary to protect the eva on the back so strongly. For your private stuff, it is unlikely that you will poke them unnecessarily.... however, keep in mind the differential expansion that goes on. I had considered epoxy, then resin and glass, then realised I didn't need to do it. All I would be doing is insulating it, and making it harder to get rid of the heat. EVA is tough on it's own, but won't do much to protect the cells from hard knocks from behind it's true.

EVA seems to stick to anything.... even tyvek. If it stuck to the dooner, and cooled and cured properly.... thats where the dooner would have to stay.... would certainly stick to glass fiber... probably would not need the resin and would be better. Some older panels I have worked on used unwoven glass matt...... impregnated with eva or sylgard type of stuff. In all instances of stuff on the backs of commercial cells I have come into contact with.... they are all very flexible.... except the tedlar??

Volvo,
Yes, the cells get completely encapsulated in the eva, and protected from the oxygen and water from thence forth. I have heard that air and water denature the silicon junction somehow, but don't know for sure if this is so.

It is UV stable, so won't discolor, flexes with temperature, is water proof etc etc..... and because it is glued directly to the glass, stops it from shattering/splintering etc.... exactly like a laminated windscreen..... which is what they use for that application as well.

That panel will be  30 degrees vertical, and it has five 3" holes cut in the top and bottom  of the aluminium back. It creates quite a draft through the void between the cells and the back of the panel. It does not show on the picture, as it is a few inches inside the edge of the panel back.

The industry standard is 72 for 24v as I understand it, but there is not enough room to fit them on. If I was to charge batteries, and I didn't use mppt, then I would have to make a high current low voltage booster panel in series with a few of these 34.5v panels..... ie for 6 panels, you could have 1 small panel of 8A x 1.5 or 2 volts (4 cells/string and 6 strings wide to run with 3 of these panels....... the good thing is when you make your own........ you can easily get what you want one way or another.

Currently water pumping is occupying my attention for a neighbour. 30000+ liters/day into 200 foot head a mile away... thirsty darn cows.... designed from scratch...good fun.

...... and thanks for the kind words..... but I admit I read your escapades a few times before I was prepared to have a go. Whilst you were a bit negative, it spurred me to find another way around the problem... thanks


........oztules
Flinders Island Australia

ghurd

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Re: Making decent solar panels part 3
« Reply #7 on: February 14, 2011, 07:27:42 AM »
72 cells...
Here is my current thoughts about it.

Need 36 cells in a 12V panel for the wire and diode loss.  That is a given.  It needs that many to get past the voltages losses and still have enough voltage to do any charging.

They tried 30, 32, and 33 cells in an attempt to not require a charge controller, and that did not work out.

The I^2*R wire and 0.7V diode loss will be the same for a 24V panel as a 12V panel.  That uses up 36 cells for half the 24V panel.
The next set of cells (sort of) does not need to consider those losses.
So 30 cells for the other half may be enough.  32 or 33 cells should be plenty for the other half?
36 + 33 = 69 cells.

Even 66 may be enough for a standard 24V battery based system, but I would not want to try to cut it that close.
G-
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zap

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Re: Making decent solar panels part 3
« Reply #8 on: February 14, 2011, 07:43:14 AM »
Absolutely impressive!

Thanks for the pictures and great description, here and the other parts.  Time to approach DuPont for a sponsorship? ;)

Of course now that you've posted this and the other 2 parts of your tutorial, and seeing how many members and guests read this board, EVA and cell price will probably skyrocket (I should have bought stock!)
« Last Edit: February 14, 2011, 07:48:37 AM by zap »

Ovais

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Re: Making decent solar panels part 3
« Reply #9 on: February 14, 2011, 08:16:32 AM »
Oztules,

Truly remarkable!

Many thanks for sharing your work with all of us. You are certainly an innovator.


Regards,
Ovais

Harold in CR

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Re: Making decent solar panels part 3
« Reply #10 on: February 14, 2011, 11:26:30 AM »

 Escapades  ??? ???

 Who, ME  ??? ??? ;D ;D ;D ;D

Harold in CR

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Re: Making decent solar panels part 3
« Reply #11 on: February 14, 2011, 03:32:56 PM »

 OZ, would you happen to know how much that EVA weighs per meter or whatever amount you bought ?? Need it to see about shipping weight to CR. Thanks

klsmurf

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Re: Making decent solar panels part 3
« Reply #12 on: February 14, 2011, 03:36:28 PM »
YOU the MAN! A+
" A man's got to know his limitations " ------ Harry Callahan

oztules

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Re: Making decent solar panels part 3
« Reply #13 on: February 14, 2011, 06:29:21 PM »
Harold,
mine was 38kg or something...... however....

http://www.aliexpress.com/product-gs/317352087-Solar-EVA-Film-wholesalers.html

This is the cheapest place in the world I have found. Service was excellent, product you've seen.....excellent, and if you check it out... shipping is FREE to Costa Rica as well as Flinders Island

I bought 60 meters at less then $8.00/meter including shipping.....who cares what it weighed......... it was DELIVERED in 8 days.... not the slow boat to oblivion.

I'm not a pimp for them, but they deserve some praise for making EVA available to the world at peanuts prices. Even the boys in the USA would have trouble sourcing it locally for that price delivered from what I have observed..... they get cheap cells but dear EVA.

Admin... feel free to delete this (after Harold has read it preferably ... he suffers tyranny of distance like me) if you feel it is too commercial..... just how I feel


.............oztules

Flinders Island Australia

Harold in CR

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Re: Making decent solar panels part 3
« Reply #14 on: February 14, 2011, 07:32:01 PM »

 OK, Oz. I read it. Thanks again

walp

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Re: Making decent solar panels part 3
« Reply #15 on: February 15, 2011, 06:16:52 AM »
ber-impressive oztules!  ;D

So this is the way to do it as properly as possible? Thanks for sharing!

Is the temperature in the oven crucial?  What about a 100C sauna? or even better, a 100C-120C wood dryer? :)
I guess if you have a hotter oven, the time required will be less, (to a certain point of course...max 140C maybe?)

What kind of material is tyvek made of? Plastic? Wood? And what preferable properties does it have as a backing?

Will *Plexi/PMMA/Lucite|EVA|Cells|EVA|WhateverTyvekIsEquvivalentOfInSweden|  work out fine?

Is it really no shipping cost from that above site?

Man, I gotta try this with my next build! :D

Thx oztules!

zap

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Re: Making decent solar panels part 3
« Reply #16 on: February 15, 2011, 09:00:23 AM »
What kind of material is tyvek made of? Plastic? Wood?

Most everything you'd ever want to know about tyvek... thanks to Google:
http://www2.dupont.com/Tyvek/en_US/index.html
http://www2.dupont.com/Tyvek_Weatherization/en_US/products/residential/resi_homewrap.html

And what preferable properties does it have as a backing?

Will *Plexi/PMMA/Lucite|EVA|Cells|EVA|WhateverTyvekIsEquvivalentOfInSweden|  work out fine?

From part 2 of "Making decent solar panels"...http://fieldlines.com/board/index.php/topic,144995.0.html
The tyveK

Originally I had hoped the teflon based tyvek would not even stick to the EVA, and I would use it simply to hold the eva away from the plastic bag/s, peel it off and just have an EVA backing. Later I could paint it or leave it if I wanted etc etc.... it's teflon right???

Well that didn't happen. My tyvek has no slits, but does have breathing pores. So small that water seems to be repelled if incidental.

Under high pressure and reasonable temp (only 100C etc) the EVA is forced into the tyvek pores, and it ceases to breath. It dosen't just peel off the EVA like I had hoped, it is stuck but good..impossible to remove..... so the pores must be lock and keying to the substrate, it is surely not sticking to the teflon.

I could still paint it, but I would actually prefer to try wax paper, which I believe is one of the few things that does not stick to the EVA, and then have a choice of what to do then.... paint it or leave it. At this time I believe it is not an issue I need to address.

In those hostile climates, maybe I'd use tedlar....I have not researched the temp/pressure profiles for it though.
I don't know, how you live there .....really I don't.

AFAIK Tyvek doesn't contain any Teflon.
« Last Edit: February 15, 2011, 09:19:41 AM by zap »

oztules

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Re: Making decent solar panels part 3
« Reply #17 on: February 15, 2011, 02:47:08 PM »
Thanks Zap.

I've had this stuff for the last 8 years, and would have gone to the grave thinking that this stuff was a high tech material made up of teflon and other stuff.....only to find out now it's not..... think the salesman at the building supply may have led me a bit astray.......

Walp

Tyvek is not a prerequisite for making your solar panels..... EVA is. You can use anything you like on the back, and get the same results.... I only used Tyvek initially because I was led to believe it was teflon based (sure is slippery stuff), and I had hoped it would just peel off.... it was only to be an EVA barrier. As it turns out, it is not teflon based, and it sticks to the EVA big time.... now we know why.

The EVA is all you need really for success, and then whatever you want after that. If you have any concern, then Tedlar is available, but I dont have any info on it's temperature profile.

The sauna or wood dryer would be perfectly good, and is in the same range as my "oven". The hotter it is, the less time required for curing ..... it is a bit suck it and see. Test panels are the best way to learn how long does what at what temp.

Yes, that EVA site is all inclusive. If you press the button for shipping cost, it will allow you to find the transport cost to Sweden or any where else....... and it will return with FREE shipping to Sweden via UPS expess saver...... as it was to here as well


..........oztules
Flinders Island Australia

SparWeb

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Re: Making decent solar panels part 3
« Reply #18 on: February 15, 2011, 10:53:21 PM »
-but you didn't get out the chainsaw, man.



...



Seriously you have changed my point of view here, it looks fantastic, and it's all done with simple materials.  Has Gary (build it solar) seen this yet?
No one believes the theory except the one who developed it.  Everyone believes the experiment except the one who ran it.

System spec: 135w BP multicrystalline panels, regulated by Xantrex C40, DIY 8ft diameter wind turbine, regulated by Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024

oztules

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Re: Making decent solar panels part 3
« Reply #19 on: February 16, 2011, 04:10:22 PM »
Thanks Sparweb.

It is nice to think I have changed the way you see this DIY panel business. I was as skeptical as you with the DIY panels... but figured that there had to be a viable way to utilize the cheap cells awash on the net. At this stage this looks like this process will make it viable for many to dabble with solar more successfully than has been the case in the past.

I don't know if Gary has read this. Maybe he will, and offer some feedback we can use..... he is the solar guru after all.




................oztules
Flinders Island Australia

oztules

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Re: Making decent solar panels part 3
« Reply #20 on: February 16, 2011, 04:15:27 PM »
Absolutely impressive!

Thanks for the pictures and great description, here and the other parts.  Time to approach DuPont for a sponsorship? ;)

Of course now that you've posted this and the other 2 parts of your tutorial, and seeing how many members and guests read this board, EVA and cell price will probably skyrocket (I should have bought stock!)

Zap, I took you at your word, and ordered another KW from ebay @ 35cents/watt TABBED front and back from fred480v before the prices go up.... just in case..... and I hate tabbing too!


.............oztules
Flinders Island Australia

zap

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Re: Making decent solar panels part 3
« Reply #21 on: February 16, 2011, 10:24:51 PM »
Heh... funny you mention that.
Ever since you posted this "part 3" I've started following some of the eBay auctions.
I can't say I've seen enough to notice any trend.

joestue

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Re: Making decent solar panels part 3
« Reply #22 on: February 16, 2011, 10:43:14 PM »
i don't think a few more orders will affect the price when theres "more than 10 available"

when this thread makes it to hack a day.. then we better put our orders in

SparWeb

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Re: Making decent solar panels part 3
« Reply #23 on: February 16, 2011, 11:54:25 PM »
... then I'd better not tell Gary about this yet!   ;)

...when this thread makes it to hack a day.. then we better put our orders in

This summer's project was going to be a solar air heater, inspired from Build it Solar.  Now, I'm not so sure...  Maybe it's time for more PV.   ;D
No one believes the theory except the one who developed it.  Everyone believes the experiment except the one who ran it.

System spec: 135w BP multicrystalline panels, regulated by Xantrex C40, DIY 8ft diameter wind turbine, regulated by Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024

Madscientist267

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Re: Making decent solar panels part 3
« Reply #24 on: February 17, 2011, 01:14:43 PM »
Quote
Maybe it's time for more PV

No doubt!

I'm still a little skiddish myself of trying this, simply because I don't have the funds set aside (yet) for playing with even test panels to get it figured out.

There are 3 things for certain -

1 - You obviously know what you're doing, and have it down to a very fine science.
2 - That's one big a$$ panel
3 - Datsuns make excellent backdrops for freshly minted solar panels.

 ;D

Seriously, excellent work. Ever consider selling them? You could probably turn a decent profit by simply ditching the tyvek (that whole aesthetics thing)...

And you said 20 more to go? LMAO How much joose ju needz mang!?  :o

Very nice, indeed.

Steve
The size of the project matters not.
How much magic smoke it contains does !

phil b

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Re: Making decent solar panels part 3
« Reply #25 on: February 17, 2011, 07:00:38 PM »
I have to say, Oz you've turned my way of thinking around too. Now it does look doable with a bit of practice.

Seems all the raw material have been found except low iron glass. Anyone know where to buy it or have a good substitute for it?
Phil

niall2

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Re: Making decent solar panels part 3
« Reply #26 on: February 17, 2011, 08:41:10 PM »
yeah...this is a pain now ...i love wind ...but what if ....i did look at those cells a long while back...