Schottky Diodes

[tecnodave]

boB,

Stumps me but in my original setup with two tracers with 3 sets of panels on each controller (2 strings of 4 Siemens panels in series, 440watts and one set of 5 First Solar panels in parallel, 375watts) Two controllers I made a logic board which looked at controller v. in that would switch the first solar panels off the controller and on to the dummy loads at 76 volts.  Probably too cautious on my part but I depend on these panels to power me through the foggy season

They do not really push these panels for off grid use. First Solar has built about 8 gigawatts of utility scale plants and just landed a major contract to replace the lost power at Fukushima with PV plants with a $100 million investment in Japan. I visited two of their facilities in Topaz, San Luis Obispo County, California (550 megawatts)and one in northern Arizona, truly impressive.

I read every bit that I can as solar is our future, sometimes I wonder just how much is baloney so I do further research on the subject. I studied nuclear so that I will know better how to oppose it.

tecno

[dgd]

"Open circuit exposure may accelerate module efficiency loss and should therefore be minimized. First Solar requires that
modules not be operated in open circuit conditions for more than ninety (90) cumulative days to avoid a potential reduction
in energy output over the life of the modules.
"

My question is, how close to Voc do you not have to be in order for the efficiency not to be reduced ?

If operating just near to Voc is not good for them, then this means that you should NOT get your
batteries full because the controller will run them near Voc when batteries are full if you have enough
power from these PVs.

boB,
Would the KID not be an ideal controller for these PVs?
With the load used as a voltage Clipper that increases a resistive PV load as the battery gets full and pv voltage rises.
dgd

[tecnodave]

boB,

I just sent you 2 data sheets on the FS-2 Modules. The one in English is close but the one in Dutch or German has the exact electrical specs as the most of the ones that I have that were made in USA but I have one made in Asia that has slightly different specs.

I can not find any I-V curves in my data collection or on their website.


There is an abnormality in their data as follows:

Panel type.                   V.max.         # cells.        V/cell
FS-2 series.                    69.6                116        .600
FS-3 Series.                    47.5                154       .308

For comparison

Siemens.                         17.4.               36         .4833
Suntech.                          35.2                72         .4888

Now if they reversed cell count

FS-2.                               69.6                154         .45
FS-3                                47.5                116         .41

Basic physics: the voltage of a cell is directly dependent on the junction in that cell.

No proof but I think I count 154 cells in the panels in the panels that I have, real hard too see as the panels are black and cell traces are hard to see, ah the mystery of it all.

First Solar is not real responsive to data requests.

FS-2 Imp is 1.04    Isc is 1.20

I went and looked for that white paper but I could not find it.

td

[tecnodave]

boB, dgd, vtmaps, & others

Results of a side by side comparison

System One:
Two strings Siemens M-55 mono in series    69.8 v.max.  440 watts
Tracer 3215RN controller. 30 amps 150 volts max
4 X L-16 battery at 60% S.O.C.

System Two:
5 ea. First Solar FS-275 in parallel.             69.6 v.max.   375 watts
Tracer 3215RN controller.   30 amps.  150 volts max
Same battery set as above. (Controller outputs in parallel)

Conditions , heavy ground fog, cannot locate sun in sky, noon, no shading, 100 % humidity

System one.       Net   78 watts.          % of STC.   17.7%
System two.       Net    116watts.        % of STC.   30.9%

This is why I futz with these cantankerous panels

tecno

[tecnodave]

I think that what I actually did in my in the fog comparison I swapped the setups where I normally  have two sets of Siemens (440 watts) and one set of First Solar (375 watts) on each controller to the test setup where I had all 4 banks of Siemens (880 watts) on one controller and both banks of First Solar (750 watts) on the other so that skewers the % of STC  values to half of the values in the previous post, 8.8 % for the Siemens and 15.5% for the First Solar. This was done last May during our foggy season, aw the value of good notes, I should have been documenting more.

I struggle for every watt through the foggy three months here, need to top off every week with the Onan. I was running the Suntech panels on a Tracer 4210RN controller 40 amps 100 max volts, 1080 watts. Don't have the notes on their output as the panels were in parallel and a different controller used with these panels with a different conversion ratio was used for them.

[boB]

boB,
Would the KID not be an ideal controller for these PVs?
With the load used as a voltage Clipper that increases a resistive PV load as the battery gets full and pv voltage rises.
dgd

Yes, you're probably right here.

That should work just fine.

boB