Making decent solar panels part 3

[richhagen]

Thanks for your replies IBDilbert and David Ames, 

I actually have acquired some wafer dicing blades from Ebay, but I will have to make a spindle to mount them on.  I would likely use my sherline lathe for that, but I have yet to do it.  I would also need make a frame to mount a motor and pully system for the spindle with a sliding x table, probably with a gear motor attached and a motor controller to adjust the feed rate.  Basically I am thinking a table just big enough to hold the clamping system for the wafer mounted on a linear bearing and propelled by a threaded rod attached to the motor that drives the stage.  The spindle would then be on a fixed gantry overhead with the cell pushed through the blades path.  I would also have to devise a clamping system, either a vacuum table or some other system such as Dave's magnetic clamp.  It will probably take me a bit of time to devise and build a working dicer for these reasons.  I was hoping that you guys had figured out a reliable way of scribing and snapping them as my results have not been reliable there and I was not looking forward to setting aside the block of time needed to build a dicing machine.  Rich

[kotheinwin]

Nicely done from those folks. I think I will stick with the vacuum system to avoid those bubbles.

It is nice to see someone else doing low temp cross linking..... just wish they had done it or published it before I took an interest..... would have saved a lot of testing things that didn't work as well as I had hoped.

Nice to see were not alone in this venture.

I think they are streets ahead of their U tube counterparts.

Thanks for the link  Ovais...... also, I notice you have been to the EVA shop in China...... any pictures yet??

To/ Oztules,

     Thank you very much for your link to Mar Rock EVA company and I ordered 51 meter on May 17,2011,May 18 China time,  to get better value and got here in California yesterday May 20, very quick. After you ordered you should email or going on-line with Winnie Chan, She can send right away to you. As soon as I got them I worked right away make 36 cells panel and I got air inside because I used heat gun so cover plastic bag melt and air going in. Today I will build oven using Sun and heat gun together with vacuum and weight. I will post pictures later on.

    Again, Thank you for all your posts.

     Mg Win


.................ostlers

[Ovais]

Dear All,

Where do you get your solar cells from?

Oztules, can you advise your source as well.


Regards,
Ovais

[oztules]

It seems to me Fred480v has the best deals for easy cells.

http://shop.ebay.com.au/fred480v/m.html?_trksid=p4340.l2562

http://www.ebay.com.au/itm/1KW-3x6-tabbed-short-tabbed-mix-solar-cells-/270753099458?pt=LH_DefaultDomain_0&hash=item3f0a246ec2

I'd like to try these too

 http://www.ebay.com.au/itm/216-3x6-evergreen-solar-micro-wire-solar-cells-new-/260787229441?pt=LH_DefaultDomain_0&hash=item3cb8215301
They look to be a step forward for ease of everything.

mlsolar has good deals  too I have a few kw of his as well.

I got short tabbed 6x6  (front and back )from Fred, and they are a joy to work with. (35 cents/watt)

Try to get short tabbed or tabbed cells, as they are likely up to spec... untabbed means they never got that far anyway.

Fred seems to get down to 30-40 cents/watt, mlsolar can if he wants (offer).

Best with it... and progress reports too.

for richagen then perhaps these
 http://www.ebay.com.au/itm/40-1x4-5w-solar-cells-20-watts-total-300-micron-thick-/270754289470?pt=LH_DefaultDomain_0&hash=item3f0a36973e


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

[dimeski]

Hi Mr.oztules
I'm from Macedonia and thanks to your post here, and I started the construction of solar panels.
Already ordered and got solar cells from everbright solar, EVA from the Wiinnie and now finishing construction of the oven ..
The biggest problem is with the bag, but I already have 2 solutions
The first is a cotton fabric that is coated with silicon than 300 degrees. These two pieces make a bag, which sticks to the same silicon. But you have to be well covered , why would't be air-tight.
2nd decision to wait a day or two and it bags from PE but the melting temperature of 168 degrees
When everything is complete I will send photographs of it all ..
My question to you (one of many)
is related to the glass ..
I see that you use tempered glass prism ... from solar panels
Are there bumps from the prism from one side of the glass and which side is external and which internal?
This is because of bumps bad sticking EVA with glass, and if they are rough on the other hand, from the outside, it will collect dirt and dust ..
I here in my town can purchase 1x2 m glass, such you, with prisms for 30 euro / piece that is quite cheap, but it worries me fixing the EVA with thus glass ...
Thanks
Zvonko from Macedonia

[oztules]

Zvonko,
Great news that you can get the glass cheaply.
In Australia early on, one manufacturer thought as you do, and put the prisms on the outside. It looked ok (nice actually), but had cleaning problems.
One panel went through the process and got reversed.... prism to the EVA. This was found to work just as well as the prism to the outside, and so it has been this way ever since.

I too put the prism to the EVA. It bonds just as well as to the plain side. Remember, when over 65C it is liquid, and so fills the voids between prisms without a problem.

Make sure you allow for plenty of drying time after washing the glass with Metho (alchohol), as it takes a long time to dry out in the very pin head center of the prisms.

I have about 2kw of home brew panels  running now. Winter is here, but it still puts out over 6-7kwh per day a lot of the  days (40 degrees south )..... bring on the summer......

Starting on the next few KW soon.

The other morning I had 2mm of ice/frost on them.... and still got 400W.... bit of a surprise to me. The frost crystals must have redirected the early morning sun or something, but it was probably  better than no frost at this early hour.


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

[joestue]

I have access to a small laboratory type vacuum oven, and have made some small sample panels with it on tempered green glass which was available to me at the time.  If I can figure out a method with consistent good results i will order low iron tempered glass.  I have invariably obtained some bubbles thus far with what I have tried, at first from applying too much temperature which resulted in the EVA outgassing,  but even with better control I still have gotten some bubbles.  I obtained the EVA through a vendor on Ebay.  I may try a different eva vendor to see if that makes any difference, but I am not sure if that has been any part of the problem. 

I'm thinking of doing something similar.
Use a non porous backing taped down to the glass in all the way around, except for a short strip where a sheet of plastic makes a one way valve.
Pull a hard vacuum first, and as you heat it up release the vacuum. that should give time for the eva to flow out from under the solder joints but still prevent the outgassing from creating bubbles.

[dimeski]

Hi Мr.Oztules
Thanks for your reply.
I tried to put EVA and a few cells on 20 x 30cm Glass ,  the EVA melt and filled all the pores and hollows.
But I have a bigger problem?!
I did the lamination according to your recipe 15 min. 65 degrees, and 70 min. at 100 degrees.
But the EVA is still sticky and soft at a temperature of 70-80 degrees.
Now I tried to put it in an electric oven and I left it there for 20 minutes at 130-140 degrees, and now I'm waiting for it to cool down.
My question is whether the EVA will still melt after 70-80 minutes at 100 degrees or should it be solid after the so-called curing?
And the second thing:
Can I use PET film instead of TPT as a background?
TPT is expensive and hardly accessible, and PET is easily accessible and can be purchased cheaply.
What is your experience with this?
Thanks
Zvonko

[kotheinwin]

Hi Мr.Oztules
Thanks for your reply.
I tried to put EVA and a few cells on 20 x 30cm Glass ,  the EVA melt and filled all the pores and hollows.
But I have a bigger problem?!
I did the lamination according to your recipe 15 min. 65 degrees, and 70 min. at 100 degrees.
But the EVA is still sticky and soft at a temperature of 70-80 degrees.
Now I tried to put it in an electric oven and I left it there for 20 minutes at 130-140 degrees, and now I'm waiting for it to cool down.
My question is whether the EVA will still melt after 70-80 minutes at 100 degrees or should it be solid after the so-called curing?
And the second thing:
Can I use PET film instead of TPT as a background?
TPT is expensive and hardly accessible, and PET is easily accessible and can be purchased cheaply.
What is your experience with this?
Thanks
Zvonko

To/ Zvonko,

     Any background is working with EVA. I used clear plastic on my back and they are working during big raining in California. When EVA dry with any backing they are hard as rock. You can wash,tap any thing you want. Even I over heat one of the quarter inch glass crack EVA prevented solar cell are not crack at all. So I apply EVA heat with heat gun on top with plastic. Just give you info.

    Mg Win

[dimeski]

 Hi    Mg Win


 Thanks for your reply..
But...
Even though I warmed up the EVA at a temperature of 135 degrees for 20 minutes and it cooled down, so I warmed it up again at 70-80 degrees, the EVA isn't solid.!!!
It's still sticky and can be removed from the glass.
What is the problem?
Does anyone know?

[oztules]

The EVA never goes hard/solid.... a good thing too.... flexes with the temperature of the cells.

 It turns into a rubbery material, which feels sticky to touch, but does not actually stick to you... bit like new gum rubber.

If you heated it to 130C for any period, it should stick to the glass very very very well. If not, either suspect your cleaning methods, or if your sure the glass was squeaky clean, the only other thing is the EVA itself..... unlikely. The modern EVA has materials in it to help it adhere to the glass.

It must cool down completely before you try to peel it away from the glass..... that means keep your fingers to yourself until it has cooled down  for an hour or so... then fiddle with it. Remember it is a good insulator too, and takes a while for the core to fully cool.

If you cured it at 130C, it should be near impossible to get it off the glass.

Once cured, 80C will not affect it at all, maybe make it slightly more pliable, but thats all.

I use clear plastic on the back now, as it looks good, and if you need to find the tracks etc later, it is easy to see them. It leaves a "hardish" non-sticky finish (not like the raw EVA), that is very tough... not like tedlar, but very good wearing and protection properties.

I'ts been over 6 months since the first ones I built went into the elements. There is no sign of change of any kind... they look to be in the game for a long time to come..... summer heat and winter ice.... no change.

Being on an island, the dew every night is phanom.... fenomin....phenomenal...... . both on the front and backs of the panels..... so don't forget to think of how to seal your rear connections.

waiting for the pics?




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

[Madscientist267]

so don't forget to think of how to seal your rear connections

Been using dielectric grease for this myself, at least at the terminal block and external connectors.

Some form of harder sealant is probably better going to the strips themselves tho. Not that mine are DIY, but the original 'seal' on the JBox is-no-more, thanks to how I had to mount them.  

They were weathered pretty bad anyway, so weren't doing much good.

What are you guys using for that 'master seal'? My gut instinct would be some type of RTV, but apparently RTV is actually capable of 'seeping' some moisture, right through it.

And I'm going to guess that the standby hot-glue-for-everything rule probably doesn't apply real well here, though I've been wrong before.  

Steve

[ibdilbert]

@dimeski

Not all EVA is the same, general rule seems to be 110c for 15 mins, but that is for what they are calling "fast cure" EVA.   Regarding the glass with prisms, if you get a hold of some, I'd like to see pictures of that, sounds pretty interesting.

[Harold in CR]

 If you guys need a GOOD sealer, I plan to use "5200" It's a Marine sealant, that can be used underwater, and still stick and seal.

 It comes in tubes or caulk gun tubes. It gets on to everything, so, get some mineral Spirits to use as clean up. Once dry, it stays there. It will get rubbery hard, and, can be sliced into with a SHARP knife. Comes in Black and White, last I knew.

[dimeski]

Hi ibdilbert
Thanks for your response.
EVA is ordered by Mrs Winnie  from China and she confirmed that EVA is FAST CURRING , but gave me the characteristics of the time and temperature and 135-145 degrees for 15-20 minutes. I tried 120 degrees, but the re-heating of EВА, she in turn dissolve and sticky .Once again I  was heated to 135-140 degrees, 20 minutes, but again was not as it should ,  or maybe I do not understand from this things...I got a new piece, heats to 120 degrees 75 minutes, along with 2 pieces of EVA for test , which I plan to perform a test of re-heating of the pieces.One issue of all: EVA has 2 sides, smooth and rough. What goes by the glass, which according to the cells?
Тhanks

[oztules]

dimeski,
It sounds like you have the right idea, and you understand the process.
 
I have not had those results, and will now try what you are doing (time and temp) and see what happens with my EVA.
Mine has both sides the same..., rough on both sides.

Originally (from Ebay) I had 7 meters of stuff that was as you describe (rough and smooth)..... it seemed to work the same which ever way I tried it. Hopefully someone knows  what side you should use towards the glass for your stuff..... my last 60 meters  is the same both sides, so I don't have to wonder.

I'm intrigued by your results and am keen to replicate the experiment (time is the problem... retirement is not what it's cracked up to be).


I will make my next 250w panel with the prism side out.... just to see if there is any useful difference apart from cleaning problems. (specular diffusion etc)



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

edit    Harold, where are you going to use the sealant..... the output boxes, or the glass to frame........ or are you doing a different kind of panel.........and when?

[ibdilbert]

Hmmm..   Mrs Winnie from China I is from Mars Rock, right?

What I'm finding interesting is some inconsistency in their EVA.   The sample they sent me was really rough on both sides, and worked well.   Then I ordered a large roll, and it was not nearly as rough, but still worked well, and both sides were rough.   By what I've read, the roughness is actually be design and to help assist in the initial vacuum process.  And you have some of their EVA that has a smooth side and a rough side, yet more inconsistency.  I sure hope this isn't a trend with them.  Sounds to me like they might just be re-selling.

Previous to the Mars Rock order, I bought some off Ebay that had wax paper on one side, I never did get "all" the bubbles to go away with that batch of EVA, and the best results with layering was as follows.

Backsheet
EVA / Rough Side down
Cells
EVA / Rough Side down (against Glass)
Glass

The Mars Rock EVA I have now is cross-linking at 112c (~234 degrees Fahrenheit), for 15 mins.  After cross-linking you can't peel it off the glass, and reheating it only causes it to be rubbery.  

[dimeski]

Here are the results from the testing.
The specimen was heated on 90 degrees for 10 minutes.
Part of the specimen under the foil became soft but not too much.
 The piece of the EVA which was on the glass, it melted and became sticky.
When the glass cooled down, the EVA piece removed very easily, but all of the other things were solid and they could not be removed from it.
Before, these pieces were heated on 120 degrees for 75 minutes.
And I think that the piece should not be sticky that much ?!
 To which max temperature can the panel be heated when put on a strong sun??

[ibdilbert]

May I ask what you are using to measure your temperature?

[Harold in CR]

 Oztules
 I have the 5200 to use, wherever I feel the need to be sure there is no way moisture can get inside the panel. I use the stuff on other projects, also. I might just run the wire connections out of the EVA, just far enough away from the frame, so I can surface mount a plastic wiring box. I will simply stand the wires up, coat the EVA all around the wires, so I can just mash the box into the Sealant, with the wires inside, and it will be watertight. Put the cover on, without sealant. Upside down, under the panel, should be plenty moisture resistant.

 The EVA I have, is not very thick. Is this the same stuff you all have ??

 I am presently in Florida, and go back to CR on the 17th. Soon after that, I will throw together the oven, and start experimenting.  My vacuum pump doesn't seem to pull much vacuum.  I am looking for something suitable, as I travel around from town to town, with my Son. 

 I need to get a tracking system bought REAL soon.  I was hoping to get something from the Mad Scientist, but, my days are limited. Any one of y'all use that Red Rock tracker ??  Seems to be pro's and con's from some of the other threads  

[dimeski]

May I ask what you are using to measure your temperature?

I'm using a digital device for measurement of the temperature

[ibdilbert]

An Infrared or probe style?    Reason I ask is I'm finding out the surface temprature of the back side of my panels is 20 degrees less than the actual temprature where the EVA is.   I get a far better reading using a probe with insulation on top, but then again I'm not using an oven, I'm using a hot plate.   Any chance your digital device is not measuring correctly?  Maybe its reading Fahrenheit instead of Celsius?    I know it seems unlikly, but it doesn't sound like your getting the EVA hot enough to me.   

[oztules]

"Here are the results from the testing.
The specimen was heated on 90 degrees for 10 minutes.
Part of the specimen under the foil became soft but not too much.
 The piece of the EVA which was on the glass, it melted and became sticky.
When the glass cooled down, the EVA piece removed very easily, but all of the other things were solid and they could not be removed from it.
Before, these pieces were heated on 120 degrees for 75 minutes.
And I think that the piece should not be sticky that much ?!
 To which max temperature can the panel be heated when put on a strong sun??"

90 degrees for 10 min will not do much... and you observed this.
If I read you correct, you had other bits of 120C for 75 minutes. These stuck to the glass well?

Thats all you want. If you achieve good adhesion, your probably good to go. Any further hot sun, will only help finish crosslinking if there is any to go I suspect. If it sticks to the glass tightly, your done as far as I'm concerned.... all good.

Good info thanks ibdilbert. all helps 112c for 15 mins is a lot less than I use time wise, my max temp is usually only about 110 as well.

Harold, good vac pumps from China for about $100. can't go wrong. (aliexpress). The panels are so cheap to make, and trackers contribute so little (<30% without clouds... far less with)), that it is cheaper and easier to double your intended panel area and fix it permanent. (38 cents per watt from fred480v is hard to compete with for a tracker..... thats only  $380/kw. (plus EVA .... .cheap as) What sort of tracker can you make for this type of money...... that never breaks down.)


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

[dave ames]

It's great to see even more folks giving this a try..

dimeski, I may have missed it..you have not made mention of your vacuum system? the vacuum pump and the resulting pressure differential is a huge part of the process. I dare say that it may go deeper than just the pressure and bubble removal..I believe a big part of this method is the removal of water while sealing everything up.

When we create a deep(ish) vacuum, moisture simply does not stand a chance. Even at these lowish initial temperatures, when we get below 29" of Hg any moisture present will "boil" away and be removed by the pump.

I've probably been doing overkill with the final (no vacuum)cure (135*C /275*F) and the time (a full hour at those temps)..don't see any way of hurting the cells at these temperatures just need to be sure that your other stuff (backing) will hold up.

EVA thickness: hard to get a proper reading (like trying to mic up a marshmallow) but seems to be approx 0.015" or so..not very thick at all.

Vacuum: This pump I have is a cheap single stage that goes to a max of 10 Pascale (only four nines 99.99% vacuum) looks like others here are doing better than five nines..about 3 Pa..those last few thousands of a percent can get expen$ive.

cheers, dave

[dave ames]

Harold,

 A correction on that EVA thickness..was doing an archaeological dig on my coffee table looking for a tap and found a scrap of that EVA..happen to have a mic as well among the buried treasures.

looks more like 0.032"  the Tedlar was the 0.015" size..




A miniature Brown and Sharpe No.4  <-This would have been the Gold Standard of Jewelers Micrometer. circa 1895-1920ish.

cheers, dave

[dimeski]

Hi all
ibdilbert, using a digital instrument with a temperature sensor, but I think the measurements are accurate + / - 1-2 degrees.
We in Europe have only SI-system, so just use degrees Celsius.
Oztules, the test sample first it was cured on 120 degrees during 75 minutes, then cooled.
After several hours the test is made​​.
The sample is again heated to 90 degrees for 10 minutes and the above results of the test.
Why me all this important?
The panels are heated in the sun, surely 70-90 degrees.
Let us not happen after several times heating and cooling, the entire sandwich of EVA,
 and the cells to move away from glass and under its own weight to fall?
That's my main problem, why I want to make a bigger production of panels, about 10-20 kilowatts ...

[Harold in CR]

 Thank you, Dave.  I still have to carry this stuff on the plane, so, have only peeked into the roll. Might just be the edges are thin ??

 Oztules, you are probably correct about more panels. I don't have sufficient funds to make more, unless my wood business picks up. I can build the tracker frame and all from wood. It's damn hard and doesn't move from weather.

 Where I live, I get the sun about 6 minutes after it clears the Horizon, and, it goes over the house at near straight up, maybe a few degrees off. I have clear access until it drops almost to the Horizon, again. Mind you, we live in a rainy country, so, I'm thinking a tracker is much cheaper. I can channel money into the Hydro system, and, into the wind system. A wooden tower will be me fine, IF I can get it stood up.

 It's not rained much this season, which started around April 20, traditionally. Once I get the panels built and in position, I expect heavy rain every day, for at least 6 months.    I have a diaphragm compressor for airbrushing. I'm going to see about trying that today, maybe. Should be the same type as yours, but, a much better piece of equipment.  I'm having trouble finding a vacuum gauge for inexpensive, and a vacuum valve. I'm going to get a SS Ball valve with Teflon seat. Being as I'm only planning on, probably, 6 panels total, I need to spend money very wisely. 

 Once the USA goes into the toilet, my income SS will be non-existent, so, planning to conserve as much as possible and work with people in the area, so they can reduce the E-bill.  We pay 24 cents per KWH in a country with Hydro and a little wind turbine array. 

[oztules]

Ok dimeski
I finally got around to making a few more panels. As promised I tried a few with the prism side out. If your latitude is far enough from the equator to give you a fairly steep angle on the panel.... ( to mitigate cleaning ) then this is not a bad thing to do ... it looks very much the same, but it does exhibit different results in different light.
 Here it is



It looks fine, it's adhesion is very very tight, and it gives a wide angle range when it is overcast... you can move the panel 40 degrees without hardly changing the current out. When the sun is out nearly fully, it behaves like the normal style does.. I will do  few more like this I think.

Here are a few of them mounted:



and completely off topic..... this is what it looks like when the sun behaves badly for solar panel work:



and



Both ends of the rainbow are in my place, but I could not find any pots of gold at the ends.....


7 kwh today with only the 1 aerosharp 1000w inverter..... need a few more inverters when I'm done building the array. Good for a short 9hr day in winter I guess.
Currently only 8 panels are connected....  the inverter is way over powered..... but it spends a lot of the time over the 1000w limit... even when the sun is not full. There are more inverters coming to soak up the excess.



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

[Harold in CR]

 So Oztules
 You reversed the EVA so the rough side is exposed to the glass ??  Sounds worth a try as soon as I return home, which will be this coming Friday.

 You are slowly putting together a grand display of Panels. 

  Harold

[oztules]

Sorry Harold.
I have led you astray. It is the glass that is reversed for dimeski. He has the same kind of hardened glass as me.... rough prism's on one side and smooth the other.... sort of frosty on one side. Normally I put the EVA on the prism side, and this leaves the smooth side to the elements... and it self cleans very well.

This time, it is smooth side in, and rough prism side to the elements. My EVA is rough both sides.... so no matter which way I put it, it is the same (Just ordered another 60 meters).

Yes, in theory, (and practice actually) there is already 3kw of panels, but due to the constraints of my inverter, it don't use the last amp or so of the output ( current limited input. Due to the low cost of the panels, it does not bother me, and also gives me a much inflated kwh for the inverter in the winter..... about 1.8kw of panel to 1 1000w inverter. (It can peak .... and does very regularly... at 1247watts)..... sheer waste.... but at this cost per watt..... not bothered at all.

So we are talking about the glass itself... not the EVA.

Keen to see how it goes for you Harold.


Dimeski. Do your tests with the vacuum and a backing of some sort. Hot (or cold to a lessor extent) eva is sticky. You may not be seeing what you think your seeing. It may be fine, but seems gooey. The backing changes all this I think..... even if you just use plastic.


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

[kotheinwin]

To/ Oztules,


       Very nice pictures of your land with rainbow end to end. I finished 1 kg off my solar panel and will post pictures of them and some are on top off old lawnmowers to move around. Here in California summer start very soon. Last week it was raining and last a few days very sunny. We will be warming up next week and so on. My home used before 20 kg a day and more. Now with solar panel , 8 batteries and 2000 watts inverter I can turn on 14 hours of all electricity, now I am using below 10 Kg a day heading to 5 kg a day next week.  I took a lot of pictures of my setting for this and wanted to post on Youtube which  some of the persons I learned from.


       Thanks for all your posting of all details about Making very nice solar panels.


        Mg Win
   

[Ovais]

Oztules,

Can you elaborate on your solar cell tester and the procedure you follow. I would like to make one and test my cells before putting them on the panel.

Thanks.

Regards,
Ovais

[oztules]

Hmmm
Not much to elaborate on.
I simply choose a day where there are no clouds. Sit at a table outside, hook up a bare copper plate (unused pcb board) with a connector soldered to it. This will act as our positive terminal..... then simply place the cell on this plate and put a probe on the tabbed front tab.... into a multimeter with decent leads, and measure the amps (short circuit amps)..... the figure is not as important as the difference between cells.

It won't be accurate amps, as you will probably use just one tab.... but it allows you to quickly get an idea of each cells performance relative to each other,

The glass, the EVA, the angle and a host of other things will interfere with getting an accurate empirical  reading of what it will do in the finished product.


I get the wife to write the cells amps on the back, and were good to go.
Using artificial light does not seem to yield the same data for me.... I don't know why.



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