MPPT AND PANEL ORIENTATION

11JAGAN

Hi,

i would like to install solar panel of 1600w total (8x200w),but my roof is facing east and west direction,i am living in the south of equator.instead of facing North direction i am obliged to put it in four panel facing east and four panel facing west . 

My question is ,should i use 2 x Mppt (1 Mppt /direction ) or can i use a single Mppt for the panel facing both direction ?

i am gonna use Victron Energy Mppt 150 /35-35A  SCC.

 

BB.

The technically correct answer has always been to use two MPPT controllers. One for each panel group orientation. The Vmp of the panels depends on the temperature of the cells. Different orientations means that each array has its own Vmp-array optimum operation point.

However, MPPT controllers are not cheap. You can try a single MPPT controller with the two arrays in parallel and see if you collect a reasonable amount of power. If the "loss" is less than 10%--Is it worth a second charge controller for you or not?

-Bill

DConlyGuy

im pretty sure you gonna need bigger charge controller my 100/30 mppt will only take 800 watts of solar in 24 volt system

BB.

Is this the controller?

https://www.victronenergy.com/upload/documents/Datasheet-BlueSolar-charge-controller-MPPT-150-35-EN.pdf

Maximum PV input: 12V: 500W / 24V: 1000W / 36V: 1500W / 48V: 2000W

And what voltage battery bank are you looking at?

-Bill

11JAGAN

mine is 36V !

softdown

In theory, panels split to the east and west should almost double the capacity of the MPPT.

What if the panels are at 10 degrees on June 23rd? With the sun almost directly overhead?

Do excessive amps really hurt an MPPT? Funny I don't know the answer to that....

westbranch

If you are not constrained for location a split array does not necessarily give you more power in total, lots of little things to consider like shade, but mainly what it will do is give you input over a  longer time  frame each day.  say 12 hours vs 8 hrs on a mono direction array.  The benefit of this is if you need a longer absorption charge to complete a FULL charge (Bulk, ABS, Float) which you might not get with the mono direction array... Over sized arrays are at an advantage here.  There would be 2 power peaks, the first one occurs when the E array is at its optimal angle to the sun, the second when the west array is at its optimal angle.  At that time depending on the tilt angle and the height of the sun in the sky, there may or may not be much input from the other array...  It varies throughout the year with your latitude.  For me a virtual array would not work in the winter ~52* North

BB.

Excessive Vpanel (input) voltage will kill a charge controller...

Excessive power for a good quality MPPT controller (within design limits) will not kill the controller. MPPT controllers will limit their output current to nameplate rating (i.e., 60, 80 amps) and many will reduce output current as their internal heatsink temperatures rise.

In general, you can efficiently drive a MPPT controller to 1/0.77 of its rated capacity (~30% over rated power) without losing hardly any actual output (clipping).

Of course, with any electronics, the hotter they run, the shorter their life. Raise operating temperature by 10C, you cut the life by 1/2 (by each 10C rise). Keeping your controllers cool/shaded (and avoid large temperature swings) will extend the life of your hardware/batteries/etc.

-Bill

softdown

westbranch said:

If you are not constrained for location a split array does not necessarily give you more power in total, lots of little things to consider like shade, but mainly what it will do is give you input over a  longer time  frame each day.  say 12 hours vs 8 hrs on a mono direction array.  The benefit of this is if you need a longer absorption charge to complete a FULL charge (Bulk, ABS, Float) which you might not get with the mono direction array... Over sized arrays are at an advantage here.  There would be 2 power peaks, the first one occurs when the E array is at its optimal angle to the sun, the second when the west array is at its optimal angle.  At that time depending on the tilt angle and the height of the sun in the sky, there may or may not be much input from the other array...  It varies throughout the year with your latitude.  For me a virtual array would not work in the winter ~52* North

East and west arrays work pretty well...until one gets too far north and looks for strong production from Nov-March. Not going to happen. I am only at 37 degrees north yet still suffer low east and west production within two months of the winter solstice....Dec. 23rd. Good thing I also use a couple panels pointing south.

The cut off for good winter time production from the east and west may happen pretty early...maybe around 25-30 degrees north.

westbranch

Softdown, I noticed that this year we had a significant drop that started about Nov 1 mainly caused by the sun moving to a lower angle rather tan dropping behind a mountain or 2...  Did that happen at your lat too or was it a bit later?

Desert Rat

I have two similar-sized arrays; one south-facing and one split between east and west. The south-facing array is on one charge controller, and the east/west on another single controller. In the summer I get more watt hours from the east/west array, but that changes in the winter. I just installed the east/west array this past summer, so I haven't gone through a full year to compare the two arrays yet. I neglected to note when the daily watt hours from the south-facing array began to exceed that of the east/west array this fall.
I'll be watching closely after the winter solstice to compare the two arrays as the days get longer. I'm at 29⁰ N.

softdown

westbranch said:

Softdown, I noticed that this year we had a significant drop that started about Nov 1 mainly caused by the sun moving to a lower angle rather tan dropping behind a mountain or 2...  Did that happen at your lat too or was it a bit later?

I do not have exact numbers from my own production. pvwatts.nrel.gov presents pretty striking numbers for the poor cold weather production of east/west arrays in northern climes. During the warmer months, east/west is almost competitive with south.