multi-directional array

Started by EW Zuber, December 24, 2020, 04:54:19 AM

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EW Zuber

I have a customer that wants to put up 4 modules, one facing east, two facing south and one facing west. Rather than buying four MPPT controllers I was considering putting a schottkey blocking diode on each directional array and using a single controller.
Wondering if anyone sees any complications with this or has used this approach. Seems to me we used to do this back in the early 1980's on the Arco modules.Thanks
(6) Solar World 175 watt, (14) Arco Solar 33 Watt, (15) REC 250 watt, 2KW Whirlwind turbine on 85' rohn 25 tower, Outback VFX 3648, Outback FM80 and Midnite Classic 150 w/WBJR, ( 8 ) Trojan L-16REB, 
WL7BDK

ClassicCrazy

Why not just put all the PV in parallel - since they won't all be maxing out at the same time then just size the controller for voltage and anticipated max current.
You don't need any diodes that way - just a combiner box.

Larry
system 1
Classic 150 , 5s3p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system 2
 5s 135w Kyocero , 3s3p 270w Kyocera  to Classic 150 ,   8s Kyocera 225w to Hawkes Bay Jakiper 48v 15kwh LiFePO4 , Outback VFX 3648 inverter
system 3
KID / Brat portable

Robin

You cannot just put all the arrays in parallel. The arrays that are not putting out full power will drag the good ones down in power. The Classic or any other controller will average the MPPT and will get it wrong. I suspect the same will happen with diodes also.
Sorry.
Robin Gudgel

boB

Should not need to add diodes.

And you should be able also, to put the panels in parallel as long as the would-be Voc of all the panels are the same.

The only time one panel will drop down the other panel voltages is if either the panels have different voltage ratings or if one panel is at  MUCH different temperature than the other ones.  In particular, a  HOT panel might drag down a COLD panel.  OR if you have a shorted PV module of course.

Normally, panels outside will be pretty close in temperature.  AND the panels that ARE producing will have more sun on them and their operating voltage will be lower than those that are shaded and cooler...  So this makes it OK.

Now, if I have forgotten something obvious here, please let me know.  Who knows ?  I could have had a stroke during the night and could be in a completely different world.  I hope not.

Merry Christmas !
:) :)
K7IQ 🌛  He/She/Me

ClassicCrazy

Quote from: Robin on December 24, 2020, 03:00:27 PM
You cannot just put all the arrays in parallel. The arrays that are not putting out full power will drag the good ones down in power. The Classic or any other controller will average the MPPT and will get it wrong. I suspect the same will happen with diodes also.
Sorry.

yeah I meant like Bob said - if all the the pv strings are the same voltage.

Larry
system 1
Classic 150 , 5s3p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system 2
 5s 135w Kyocero , 3s3p 270w Kyocera  to Classic 150 ,   8s Kyocera 225w to Hawkes Bay Jakiper 48v 15kwh LiFePO4 , Outback VFX 3648 inverter
system 3
KID / Brat portable

EW Zuber

So the idea being that with panels in parallel any panel that has a drop in output voltage will just have it's cells reverse biased and appear as a very high resistance?
Will a KID MPPT controller will be OK with this?
(6) Solar World 175 watt, (14) Arco Solar 33 Watt, (15) REC 250 watt, 2KW Whirlwind turbine on 85' rohn 25 tower, Outback VFX 3648, Outback FM80 and Midnite Classic 150 w/WBJR, ( 8 ) Trojan L-16REB, 
WL7BDK

boB

Quote from: EW Zuber on December 25, 2020, 12:33:02 AM
So the idea being that with panels in parallel any panel that has a drop in output voltage will just have it's cells reverse biased and appear as a very high resistance?

Something like that.

Quote from: EW Zuber on December 25, 2020, 12:33:02 AM
Will a KID MPPT controller will be OK with this?

Should be just fine.

K7IQ 🌛  He/She/Me

mike90045

#7
I know several folks using multiple arrays (virtual tracking) and they are fine.
  Each string MUST be identical - panels & VOC, or the controller can get confused easily

Bruce - from another board, has lots of land, time and machinery, and has built many arrays
with harvest documentation about how they work with virtual tracking.

starting with post 25 in this long thread, it gets into the meat
https://www.solarpaneltalk.com/forum/solar-panels-for-home/solar-panels-for-your-home/13861-sun-hours?p=163376#post163376

(Of course the reason the Bruce gets some many hours of "producing sunlight" in one day is due the way he has set up his panels. One group is facing East, another South and a third West. So for most of the day at least one group is producing.
It is a very impressive system. Great job Bruce. )
http://tinyurl.com/LMR-Solar

Classic 200| 2Kw PV, 160Voc | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph )| Listeroid 6/1, st5 gen head | XW6048 inverter/chgr | midnight ePanel & 4 SPDs | 48V, 800A NiFe battery bank | MS-TS-MPPT60 w/3Kw PV