How to make homemade solar panels

I found this web on how to make your own homemade solar panels.

http://www.thebackshed.com/Windmill/articles/OzSolarPanels.asp

Make your own Solar Panels!

By Oztules

It's something I said I would never do..... but now I have.

If you have no value on your time, and want to do your own DIY solar cells, then it has always been possible to cobble

some cells together, stick them to a surface, and place plastic or glass over them, measure the output..... and

generally feel good.

A fancy frame helps with the karma... but you know in the end it is only temporary.

As the water vapour creeps into the sealed wooden framed ones, or the window glass you scrounged up...breaks

because of the heat/cold and localized heating in particular cells, and it all falls in a heap. It can get pretty sad for a lot

of devotees that have tried.

There are plenty of youtube stories and how too's...... but all (but the ones using sylgard (or whatever it's called)) are

doomed to failure)...... except those who have tried to use EVA (ethylene vinyl actetate).

I viewed a few treatments on the youtube sites, and none of them inspired a great deal of comfort. They all revolved around using a heat gun and a heap of good luck to melt the EVA around the cells, and onto the glass.........

Why I thought, did they make solar cells 30 years or more ago, and still basically the same today...and yet the

amature panel maker comes up with lots of bad ways to do it??

I pondered this for a while, and in the meantime, a plumber friend turned up with a few solar hot water panels..... also 25 or more years old..... they were stuffed..... but they did

use tempered glass, and it was iron free glass.... and it was free glass ( this was the clincher).

So I sat and looked at a few 2 sq meter panels (1x2m).......... yep, had to have a go too.... but it cant be cut!

This is where I decided to look around the world at the current state of play. This was sobering, no real effort at

making proper panels like the big boys built without the big boys price tags... why not?

It appears that folks thought you needed a laminator style of machine, which were very expensive, and a barrier to making your own. But if you look at what needs to be achieved, it

is really only a few simple steps.... so lets look at the how and why.

Traditionally they use a sheet of glass (iron free tempered if you can get it), a sheet of EVA, the cells themselves, another sheet of EVA, and whatever your having yourself. After the last EVA sheet, you only really need to put something there that

will not wick, and will give you something for the very very sticky EVA to bond to that is not your "jig" It can be painted later if you want more protection. Usually they use tedlar, but really any inert permanently waterproof material will do for

protection.

The simple theory of what we are trying to achieve is this:We need to get the cells fully encapsulated in a UV stable envelope, that resists water and air from denaturing the cells. It

must allow for differential expansion rates to occur between the silicon wafers, the glass and the medium itself....... and no bubbles.

Ethelyene vinyl acetate is a plastic sheet .5mm thick. It is soft plastic in texture and seems innocuous enough....... however, when it gets to only 65 degres C, it melts. This means that we need not get to very high temperatures to get something to

happen.

I'll bet there are plenty of hopefuls ( like me for instance) that grabbed some EVA, some glass, and the wifes oven, and made a prototype cell......but it is filled with bubbles!..... It does stick to the glass and, it envelops the cells well, but it is

useless because of the bubble population.

It is at this point that you start to get a bit anxious about where to get a laminator...... but you don't really need one. We just need to emulate what it does.

Next thing we look at is what happens when it melts. To get the EVA to be useful, we need to get enough energy into the stuff to cross link the molecules. It changes the way the material behaves, and increases the melt point considerably as well. At low temp (65C-80C) it melts to itself very well, but is only slowly converted into the final product, so we have to keep it at these temperatures for long periods..... but as we increase temp, things happen a whole lot faster, and 5 mins

may be enough at 145C to get it to cross link, and stick very strongly to the glass and the cell itself.

It also needs some encouragement from pressure..... or a vacuum perhaps, and use the air pressure to do the job of supplying the pressing force.

Now we know it works perfectly well without vacuum, but you will have myriads of fine bubbles.... blocking out the sunlight.... well, not so perfect after all.

So we need a vacuum pump. Ideally one that can draw a near perfect vacuum. The vacuum you can achieve sort of directly relates to the bubbles you will get left with. High vacuum.... no bubbles. It's that simple. The vacuum will also press the

cells very firmly (200 plus pounds per cell for the 6x3 ones) against the glass, and this will help the glass bond, and make for a very flat cell, with no voids in the plastic envelope.............as always there is a but:... you must have NO leaks at all, or you will get uneven vacuum in the sheets, and you will get bubbles forming.... probably in the inter cell space, but bubbles

all the same.

The heating profile I will use is like this:

15 mins at around 50C with full vacuum15 mins at 65C with full vacuum

70-80 mins at 100C-120C (or hopefully more) with full vacuum

This last bit is dependent on the EVA you get. Low temp EVA is used for window lamination, where electronic components may be incorporated into the glass matrix....

For “normal” EVA if we can get the temp to rise some more.... then good. Even if the containment bag (ok garbage bag) fails at this point, it's work is done for all practical purposes... better if it does'nt.......but we get what we can.

So all in all.......it looks doable.

First step for me was a BIG oven.

An oven that would handle the 2 meter by one meter panes of glass that came from out of the solar water

panels. (it turns out that for some quirk of history, there are plenty of these old solarhart type panels laying around

over here).

We know that the temperatures involved are not terribly high in order to achieve the bonding and cross linking that

is required to get the cells to be protected, and pressed against the glass without any bubbles..... so I started with a

wooden construction..... yes for an oven.

I had recently pulled down a wool shed for a fellow, and I was given the wood.... lots of old 4x2 hardwood.... so this

was to be the frame It looks like this >>

I was also given some packing material in 8x4 foot sheets of low grade 3/4" pineboard.(someones kitchen apparently turned up in them). These would serve for the bottom and

lid of the oven. For the sides I just used some of the old floor boards from the shearing stand.....

The whole thing is lined with ceiling roof bats insulation and then all held in the walls with a sheet of TYVEC

building wrap material.... could be anything really.... even paper.

Ok, that gets us the oven walls and floor, and the lid was just a sheet of the 8x4 pineboard with insulation laying on the top.... Now we have an insulated container that will take our panel.

What this means to the 60watt panel builder.....is that even an insulated cardboard box will do for an oven (I used one with a fan heater blowing from in front for the initial trial, with blankets and dooners for the insulation...... perfectly good for a 60

watt panel)

Next step is a heating element.

This was simply solved by destroying a fan heater/radiator. These things draw about 2000 watts and incorporate a fan and a nichrome heating coil. They spill out a fair stream of not too hot air, so are unlikely to melt our plastic bags (comes later)

when we bring the oven up to temperature.

I built the heater body out of a "think safety" sign (ironic really), which housed the heating element at one end, and the fan motor at the other. The fan blades were plastic, and would melt in this environment (proximity to the glowing element), so I

stole the aluminium blades from my big MIG welder, and put the plastic ones back in that.

This gives us a 2000w heater that blows warm air..... but not too hot,and will allow us to gently heat the oven up to about 100-120 degrees, without any cunning trickery required to temp control it. Because the oven is so well insulated...... we just

keep adding watts from the heater until we get to where we want.

Finished it looks like this:

Perhaps finished was too strong a word to use...... but it does work.

Eva onto toughened glass has a track record, and most folks know of panels that are at least 1/4 of a century old and still running fine. The EVA of today is better than the EVA of yesteryear, and will be less likely to change colour than the older material. I have some BP panels 15 years old, which have clearly changed to a brownish tinge over the cells... from the

heat, not the UV alone. The inter-cell spaces are still clear, as are the last 1/2 inch of the outer perimeters of the cells.... but even then, the performance is probably only 10% less than stated on the stickers.

If you build the panels for 50c per watt, and they only last a few years.... then it would have been cheaper to buy them made.... as they should have lasted at least 12 times longer.... so to keep replacing is $6.00/watt......??

To reiterate the preliminary vacuum stage.

With large cells, the metal tab on the front will try to take the pressure of the air when the vacuum is pulled on. It can then try to push the tab wire into the eva, to spread the pressure load. When the air temp is cold, the EVA won't give easily

enough, and the silicon cell will try to wrap around the tab wire so it can press against the eva as well.......not being flexable, it will instead split along the tab.

This is easily mitigated by raising the temp up to 50C or more (less than 65C though) for the prevacuum, rather than room temp.

I found room temp fine on a hot day, but too cold at night...... so now use the oven to get 50C. This softens the eva, and makes it easy for the tab wire to sink into the eva, so the silicon presses evenly against the "glass".

Moving right along, we now have an oven to cook the panel in.... we have bought the vacuum pump, and are now prepared to make a test panel/cell..... just to see if it is true.

I decided that it would be best to do a show and tell for a single cell at this point, in a step by step approach.

So here we go:

First get a piece of glass that will fit your cell on. Wash/dry the glass with alcohol (Methylated spirits).

Grab the bit of your EVA your going to use, I have chosen to build a single 6x3 cell, with some other bits

thrown in just to give an interspace between cell and cell bits..... like this:

Next throw on the top EVA piece:

Now a piece of tedlar, or even just sheet plastic ( I used white building wrap this time) anything you want the rear of the cells to wear. It must be non-porous, rot proof, water proof and everything else proof. It only

performs the role of keeping the EVA away from anything that may want to harm it.... and to allow you to

get the panel away from the vacuum bag.

The EVA cross links into something a bit like silicon. It is rubbery, and not especially strong..... although try

getting it off the glass once cross linked and bonded properly and you may decide that it is very strong.

Here we are with a piece of building wrap on the back. (The wrap is porous but the EVA will soak into it and fill the pores.... it has been found to be better to just use plastic sheet... the EVA when heated initially will be a

runny liquid.)

Now we have all the ingredients to make it work, we just need something to allow the vacuum to suck the air

through..... an air wick if you will. This can be any porous material you can get hold of. I find for small 60watt

panels, that a few thick teatowels covering the back do ok, for bigger panels, it is best to find something a bit

better.... beach towels? Glass matting would be good if you have it, I tried shade cloth on the 2mx1m panel, but

found that it shrinks a little when it gets heated. Not enough to damage anything, but enough to make the

cells not line up as I had placed them. For this show and tell I just folded up a rag that was lying around near

me... and it looks like this:

Next we need a plastic bag big enough to place our panel in. Unless your into building big ones like I have, most likely a big garbage bag will be the best for the

job... cheap, plentiful, and plenty strong enough for the job. Here I used a transparent one for demonstration of

seeing the stuff in the bag

Next we poke a hose into the bag and seal it up I use plastic wire ties. This seems to hold the bag opening onto the vac hose pretty well.... except for this time. The plastic bag must have a hole in it, as I could not get down to max vacuum......

Do NOT place the rubber suction hose over a cell. It will crack that cell, so just place it between your airwick

material and the glass... or inside the folds of the material, but away from the cells themselves, and let it suck from there. Provided there are no leaks, all the air

will all eventually seep through the wick. If there is a tiny leak, your wick will need to be very very porous to still work. If it is a bit difficult for the air to move through, a

leak will kill this project.... if it is a very free wick material, a leak may be tolerated.... best without

though.

So I have replaced the clear leaky bag with a trusty black garbage bag....

Note the wire ties:

Now for this exercise I won't use the big oven, but instead will show just how simple this can be.......

Here is the latest you beaut high tech laminating machine...... or the build it in 1 minute oven..... and it will work every bit as well as an expensive laminator

Of course we know there is more to it than this ......like the heater.For this size ... and up to at least a 60W panel, a fan heater pinched straight from the loungeroom would do to get it up to 80-100C..... or if you wanted to prove a point, perhaps broil it in boiling water.....ie half a 44 gallon drum parked over the

camp fire........simmer till cooked.

Well I guess that would work too, but I'm trying to make clear that this does not need to be high tech, to get a perfect result.... just temp time and vacuum

.If you are going with very low temp, then it will take a very long time... ie 80C for 80 minutes, or 140c for 5-10mins

I have toyed with the idea of using the sun... ie use the some of my spare solar glass from the hot water heaters, and make a solar oven... very similar to the solar panel itself... as the oven.... I haven't tried it as yet, but if you can boil water on a

hot day with a sheet of glass and the black backing..... then , it can crosslink the EVA easily too.

Note the solar cooking has now been done in Africa to do it similar to this.... but without the vacuum...... they were still happy.

Your trial one will give you an idea of how long to cook it with what equipment you have to get your brand of EVA to crosslink properly and stick to the glass VERY well.

If it has not been left for long enough, you will be able to peel it off the glass, we don't want that..... try just

putting it back in and cook some more... noting how many minutes gets the required bonding... if it is too poor this extra cooking may not be enough, but has

worked before.

Our trial one looks like this

and the whole sophisticated arrangement looks like this:

And yes, it got to .....and stabilized at about 112c... so I cooked it for 45mins anyway. Note the improved

insulation (brown towel) pushed the temp up another 20 degrees from the picture first showing the box oven

without this high tech improvement.

I don't think you can overdo the time on these low temp crosslinking exercises, although it is probably worthwhile

exercise to use a normal cooking oven with a good thermostat to get an accurate picture of how the stuff bonds to the glass... how long for how well. That is the only critical figure in all of this.... and theoretically then

you can always put it back in the oven without any problems at all..... but I haven't had to as yet

And here is what we have got ourselves.:

So it does work, and it is dead simple, and very easy to get right.... just test your EVA until you get to know how

it works for you.

The only difference to doing this size

or this size:

It is how much time you have, how many cells you have, and how much glass you can scrounge up

I bought the EVA from here: http://www.aliexpress.com/product-gs/317352087-Solar-EVA-Film-wholesalers.html

They got it here pronto, and free shipping. Minimum order is 10 meters with free shipping to even here (remote island).

The base EVA material is combined with additives via catalysts with added curing agents, UV stabilizers, anti-oxidants etc.

Also glass primers to aid adhesion to the glass substrate.

Note we said curing agent. This tells us that we start with one material, and it CURES into another. Thats the crosslinking we talk about. We are not just melting and resetting, otherwise we would not need to hold it at certain temps for certain

periods of time... We are melting, and holding it in that state, while the gell changes it's characteristics.

If we were to take samples during the curing, we could weigh them, wash the uncured gell out with hot toluene solvent, and weigh again.

What is left to weigh is the final material, the toluene will disolve out the uncured gell. We could use this technique to see if we had finalised the curing or not in a scientific way if we so chose..... or we could use differential scanning calorimetry to acsertain the remaining gell content..... or just have a look and see if it has stuck to the glass yet....just keep testing until

you get the ball park timing right.... simple stuff indeed.

One thing that does not sit right with me is some comments made that the cells only get as warm as they would in open circuit condition.... ie don't heat up under load, but in fact should cool by the amount of energy they transport from the cell

to the load.... sounds right..... but in a panel.....

I have not found that to be the case. In all instances I have tried, commercial and home brew, there will be some cells in the matrix that get very very hot, and those that don't.

Those hot cells will certainly cure the EVA around them if it was not fully cured before. I assume that as all cells are not created equal, different resistance cells will handle the current differently. Those with the highest resistance will get

hottest, and so get hotter as they get thermal runaway (ish), and they end up very hot indeed. ...... but I have never seen any sign of remelt in those instances..... even in the home brew ones.

Well it's time to ramp it up a bit. Up until now I have attempted to show how simple it is to work with the EVA, and make a single cell panel with very little tools at all..... yes even with a cardboard oven etc.

Time 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 have 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 solar 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 has prisms on one side and flat on the other.... like frosted shower glass almost.... I have tried bot the rough side and the smooth side to put the cells on..... I think I prefer the smooth side and get a rough outside..... slightly better when the light is diffuse....... however, in latitudes where the panels are flatter, then cleaning becomes a problem where the dust settles in the rough valleys.... so in those latitudes, perhaps put the cells on the rough side with the smooth side to the

sun.... your choice really.

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 rarely 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 (to stop the Al draining the heat from the cell too fast when soldering), 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 labouring 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 (building wrap this time for me, later I will use plastic sheet (ran out of

the white stuff), and whatever else for you).

Later I turned the sheet over ...... with mixed results. The logo writing wrecks the visual impact because of the blue and red .... oh well too smart too late.

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.... (hot house plastic I think it was designed for) so I cut off 2x 2.5M bits of it and laid them 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 heat 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 a 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... avoid shade cloth is the moral here.

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. NOT

on the cells themselves....... yep, it's all starting to happen about now.

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

NOTE WELL: the weather was hot, and the cells small, so this did not crack the cells. If it is cool, or the cells big, or your tabbing is less than flat..... do this stuff in the oven

after heating it up to about 50C..... not just the air to 50C, but the glass..... slow is good. I put the temp probe against the glass (underside between the glass and the

rails holding the glass up in the oven)

Here is a close up of the hose going into the cloth:

Now we have to manoeuvre 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 bag and

free the dooner as soon as practical. The eva will still be a bit soft at this stage... be careful, as you can upset the glass adhesion if your not careful at this point... and you can remove some from the edge or whatever. When it

cools and the curing is finished.... It is tough stuff, and if cured will have stuck to anything within reach

So now 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

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. Now I use the 6x6 cells. 66 cells per panel. These are pretabbed front and back (short tabbed).... with these 500watts per day is achievable

Lets not loose sight of what we are trying to achieve..... we want power and we want it cheap. If we have to buy too much exotic stuff, we may as well by commercial panels as the cost spirals away very quickly.

The output difference will have more to do with the quality of your cells (when you sort them out) than the quality of the glass substrate. My tests showed that a 10-15% loss would result in using normal window glass... Now if one is free (say

window for instance) and available, then it beats the bonox out of buying glass that may give you less improvement than buying and sorting the cells properly.

If you bang the cells in without sorting you may degrade performance of a panel by more than 30%....... and waste the better iron free glass.

So, even without the iron free glass, we can make panels within 10-15% of a commercial variant, and there will probably be a no-cost component for the window glass. With the money not spent on exotic glass we can probably build another panel,

and have 170% more power for the same money.... even using very ordinary glass......Glass thickness is also a factor with transmission loss, and the thicker the glass the worse things get..... but again this needs to be balanced out with advantages of strength and availability. The latter is the killer over here. It is just our

Government in their wisdom are virtually paying folks to ditch their solar hot water for the new complex heat pump things . So there are lots of 25 year old panels (and younger too) just there for the taking....with the aluminum back as well.

It is of course up to you as to your final cost per watt... but this can be can be very low if you don't try to use all perfect stuff....

Waffle and some more pictures of panels:

As I had the meter out, I decided to check the latest panel again for short circuit current ....

Just to make sure the meter was pretty close to right I used 2 amp meters in series as a rough cross check.

There was a difference, but not enough to excite me unnecessarily...... here they are:

They are a bit better than the other day, which was a bit hazy ( big winds seem to get a hazy look to an other

wise clear day in the ocean environment)

In this setup. You can see by the shadows, that this was not the noon sun by any means. I did see a few

moments of over 9Amps, but this was caused by small clouds near the sun I think.

CELLS:

The strangest things happen with new cells. I built a quick and rough cell tester from a 150w flood light etc etc. I sorted the cells, and was disappointed that there were so many less than good ones.... ie 2.0-2.8A cells.... a good amp less than the "normal" 3.8 + ones. Now putting 2A ones in series with 4A ones gives you a 2A panel... bummer... so thats why we test

them. We want to see mostly full power panels, and all the duds in a feeble panel.... not mixed.

The odd thing is, when taken outside into the real sun, strange things happen. Most all of the 2A+ cells came up to 3.4-3.9A The really good ones didn't change at all, the reasonable ones improved a bit.......... but the baddies mostly came up to

spec or close. There are still some that didn't, and will be made into window glass electric fence panels.....

So now I always test the cells in true sunlight.... twice..... lab conditions does not seem to tell the real story..... I don't understand this at all.

BIGGER CELLS:

For the panels built with the 6x6 cells, and they are fantastic to work with, and perform very very well.I have seen well over 9A short circuit.

Direct into a 24v battery bank from a single panel over 200 watts....not bad without MPPT or some other

electrickery

No that was not the max reading, but was what it was doing when I finally remembered the camera.

It had gotten to 7.5a@ 27.8v..... but the current dropped a tad when it got over 28v This is only a 66 cell panel (6

rows of 11 6x6 cells)

I have run out of building wrap, and now use the same plastic sheet I use for the bag as a backsheet. It makes

for a nice clean back, which is transparent and very tough as well.

and a close up picture.

Here is the layer formation:Glass-eva-cell-eva-plastic sheet.

So it is possible to make decent panels for 60c/watt on a remote island in the middle of nowhere.

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

I asked Oz if he could suggest a supplier for the bare cells, below is his reply. Sources may change in time.

http://shop.ebay.com.au/fred480v/m.html?_trksid=p4340.l2562 is the ebay shop for fred480v. He has the best cell deals when he advertises the 6x6 tabbed front and back (short) for 35 cents per watt. This is hard to beat price wise, and ease of use wise. With these 500w/day is easy. With untabbed 6x3 cells, 500w/week is more like it. I haven't tried tabbing 6x6 but

assume it is a nightmare for any quantity.

He does not sell the 6x6 tabbed ones all the time, you have to keep checking. When he does, it will be for a limited number, then nothing again. I have bought 3kw of these cells, and are a dream to use, and all full power. As a rule, if they got to tabbing stage, they have been accepted as A grade output by the factory.... but a breakage or tab fault will ruin the

entire 19 cell string..... fred gets these... I love em. They come from Shott Ssolar AG in Germany.

Plenty of other places sell good stuff, but not fully tabbed at 35c/watt.. For making big panels, 6x6 are the go, as there is less cells to string for the same power (1/2). In my panels this means only 66 instead of 138 6x3's.

Untabbed cells are a pig in a poke situation. They were never good enough to get tabbed for a host of reasons. Dye color, power out, etc etc. Thats why I would steer clear of untabbed cells, as it is more work, and I have found far less reliable

feed stock. I tabbed 1000 3x6 untabbed for 800 useful ones........ the ones I got from mlsolar. mlsolar is a fine fellow, and sells tabbed unsorted ones. If I needed more I would consider these, but still dearer than the 6x6 tabbed ones from fred.

(when you can get them).