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Sulaiman

Tue Apr 09 2013, 05:43AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

I'm about to make 2x 1m x1m (6 x 6 cells, 6" x 6" each) c120 W per panel
and one 0.8m x 0.8m (6 x 6 cells, 5"x 5" each) c80W per panel

They will maintain multiple (2x 12V) lead-acid batteries for a 950 W UPS I have.

IF it seems worthwhile I may have a go at a larger installation for the house.

Is it worth 'blogging' it here or is it so common that it's not worth it?

klugesmith

Tue Apr 09 2013, 05:57AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1714

Yes, please tell us the story as it evolves.
Are you going to make or buy a DC:DC converter that keeps the PV panels at maximum power point, under changing illumination, while battery bus voltage remains constant?

Steve Conner

Tue Apr 09 2013, 07:45AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Solar installations might be common now, but DIY ones aren't. (To qualify for the subsidy, the system needs to be put in by an approved installer.) So I'd certainly be interested to read about your system.

Sulaiman

Tue Apr 09 2013, 12:26PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

START:
Browsing eBay I saw (20x) 6" x 6" pv cells and put a bid, which won.
Then I realised that 20x 0v5 = 10v = not very useful so I started to collect more pv stuff,
bidding low on 20x and 10x lots of 6" and 5" polycrystalline cells.
That's when I realised the 'extra' costs
... tabbing wire, glass, and worst of all Silicone sealant.
This is not a thought-out plan!

At the moment I'm waiting for the first 1.1 kg of 2-part silicone and two more lots of cells to arrive from eBay sellers
and in two days I expect (2x) 1m x 1m and (1x) 0.8m x 0.8m 4mm thick low iron toughened glass.

The (present) plan is for (2x) 6x6 6" cells (36x <0v5 @ <8A), two panels in series to charge 24V battery bank for my UPS
Initially I shall just make a simple shunt regulator, MPPT if I obtain enough battery storage.
and (1x) 6x6 5" cells (36x <0v5 @ 5A) to maintain a 12V 24A.h battery for my amateur radio stuff.

When I bought the cells I thought that would be the major cost ... WRONG !
So, even before I start I've made a mistake, monocrystaline cells although a little more expensive should be used
for (theoretically) longer life and better output during less than full sunlight (pretty much all the time in UK)

By this weekend I hope that all of the component parts for the panels will be available for photo's.

The battery bank is another MAJOR cost ... new 12V 110 A.h batteries costing cÂ£100 each
... I'll be visiting scrap yards looking for usable car batteries!

NOTE: THIS IS NOT A TARRIF EARNING SYSTEM, JUST A SYSTEM TO HAVE MY SHED 'OFF-GRID'
ONLY IF IT SEEMS WORTHWHILE I WILL GO FOR FEED-IN TO THE NATIONAL GRID.

'off-grid' is overstating it a bit,
. my UPS needs 240 Vac initially, it should run as long as the batteries (two internal and as many as practical external) have solar charge
. there is a chest/deep freezer in the shed, I'm hoping that the UPS can handle the compressor startup.

I shall list suppliers and prices as a guide, (GBP incl. tax, p&p, freight etc.)
(QTY) ITEM (COST) SUPPLIER
(20) 6" x 6" polycrystalline cell (20.51) eBay ledsolar
(20) 6" x 6" polycrystalline cell (24.00) eBay ledsolar
(20) 6" x 6" polycrystalline cell (20.34) eBay passionjiayou
(10) 6" x 6" polycrystalline cell (07.50) eBay misol03.2012
(20) 6" x 6" polycrystalline cell (20.90) eBay ledsolar
(40) 5" X 5" polycrystalline cell (23.09) eBay ledsolar
(10') 5mm x 2mm 'bus' wire plus
(100') 2mm x 0.16mm tabbing wire (07.81) eBay powerinverter-it
(48m) 1.5mm x 0.2mm tabbing wire (12.27) eBay mini_vini_vinci
(1) Flux pen (01.36) eBay misol999
(1) 1.1lit. Silicone Encapsulant (49.99) eBay amyrla
(2) 1mx1mx4mm low iron toughened glass (42.28) Brownhills Glass Co.
(1) 0.8mx0.8mx4mm low iron toughened glass (13.53) Brownhills Glass Co.
(4) 20mmx20mmx3mm x900mm aluminium (13.32) eBay brilliant2buy

Total so far (256.90) ..... don't tell the XYL !
Still to buy ;
Frame for 2x 1m panel
More Silicone Encapsulant or EVA film
AND THIS IS JUST FOR THE PV PANELS.

2Spoons

Tue Apr 09 2013, 09:59PM

Registered Member #2939 Joined: Fri Jun 25 2010, 04:25AM
Location:
Posts: 615

Which silicone did you buy? Sylgard 184 has been used for a long time, but I recently saw a product brief from Dow for a PV specific encapsulant (sorry can't recall product code).

Sulaiman

Wed Apr 10 2013, 12:17PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

The Silicone hasn't arrived yet and I DON'T EVEN KNOW WHAT BRAND IT IS!
It was advertised in eBay under solar encapsulant, it's the cheapest I could find (possibly another mistake)
It is supposed to be equivalent to the most common solar cell encapsulants;
GE RTV 615
Dow Sylgard 184
OptiTec 7020
QSIL 216

I looked carefully at the QSIL 216 datasheets and others from Acc Silicones,
clarity, yellowing in u.v., adhesion and viscosity are all variables.
Hopefully by this weekend I will start on the 0.8m x 0.8m panel (test/trial run panel) and can give better info.

Sulaiman

Sat Apr 13 2013, 08:16PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

The weekend is here but the flux pen did not arrive yet so no 'tabbing'

Measured the resistance of tabbing wires in mOhm/m @ 2Adc;
5mm x 2mm = 22.2
2mm x 0.16mm = 71.1
1.5mm x 0.2mm = 59.0

So, for 6x6 5"x5" cells Rdc = 36x71x0.126 /2 = c 162 mOhm ... say 0R17 warm
And for 6x6 6"x6" cells Rdc = 36x59x0.157 /3 = c 111 mOhm ... say 0R12 warm.

So for the smaller panel there would be a volt drop of 0V82 @ 4A8 (max)
and the larger panels 0V86 @ 7A2
which seems ok

Silicone encapsulant arrived .. made in Poland, specs. look good

NOTE: The silicone looks as though it would be good for 4HV-type potting;
10kV/mm, tanD = 0.005 @ 1 MHz ('Q'=200), cP = 2000.

Update: Now bidding on micro grid tie inverters on eBay !

Sulaiman

Sat May 04 2013, 02:32PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Today started soldering tabbing wire to the 5" x 5" cells,
a hard, flat surface is required under the cell being soldered
or the 0.2mm thick silicon will crack,
I started with a ceramic wall tile but it absorbs too much heat so
a ceramic wall tile with a thin sheet of fiberglass is what I'm using now.
This job is tedious.

Based on current eBay prices (as low as GBP 0.50 per watt, framed monocrystalline)
I would say to anyone contemplating a similar project...
DON'T... a lot of time and concentration and I'm not even saving money!
Since I've bought all the stuff I'm commited to finishing
but I honestly wish that I hadn't started.
_________________________________________ ______________________
Update: 4 1/2 hours later ........... 36 tabbed 5" x 5" pv cells.
Next; testing of individual cells and cutting Aluminium 'L' sections to make frame
and some photo's.

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