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
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
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.
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 !
:) :)
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
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?
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.
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. )