I recently install an extra string of 2s panels facing east to compliment the north facing string of 2s2p.
The result is 50min. extra sun in the mornings before the north string starts up.
I still have to add the west facing string.
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Is this on the same MPPT? If so, do you find that your overall peak is much reduced due to you having East and North panels on the same MPPT?
No these are on separate MPPTs. You’ll see the top one called North and the bottom East/West.
The West string that I still have to install will join the east string. I’ll be able to give you some data when that string is installed that should answer your question.
Ah yes, I noticed that a little too late.
Thanks, I’m quite interested in that. I have two WWNW facing arrays. Now I didn’t want to add panels on the roof behind them initially, because it is EESE, but maybe it is viable to just pop a few up there to kickstart the day, even if it will be a little inefficient.
From what I am seeing since installing them last Sa. I should have put all my panels East and West and nothing North. It works very well.
My panels are mounted at 30deg
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I finally connected the west facing string late yesterday and while there are some clouds today I can say that the west string does not pull down the east string, but rather just add. Previous max watts for only the east string on the MPPT was 850W while this morning it was over 1kW at 8:30am already.
I’ll wait for a better day with no clouds before posting some graphs.
This is great news. Then it would make a lot of sense for me to put East and West panels together on the same MPPT.
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I initially had East and West on the same MPPT, not that I think it was a big “loss”, but I split them to separate MPPTs and had better yield. Obviously the expense is something to consider, I was lucky to trade the bigger MPPT for two smaller ones, with no additional cost.
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see article above regarding panels with different orientations on one mppt
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I oversized my panels a bit for the east and west strings.
My 2 MPPTs can each do 1050W (actually 1160W according to the specs, but that is only if you have a 16s battery, not 15 like mine).
So for the North MPPT I have 2s2p consisting 335W panels, all 4 looking north.
For the North MPPT I have 2s2p consisting 400W panels, 2s looking east and 2s looking west.
The idea is that when the east side is at optimum angles to produce their 800W the west side is at a very bad angle for producing peak power, and vise versa.
Nice article. Seems to mirror what I am seeing as well.
Conclusion
Best practices dictate that installers should make the best attempt to optimize panel orientation, and minimize discrepancies between sub-arrays. This cannot always be achieved given real-world demands and constraints. Using a single inverter with strings of multiple orientations is a practical solution to reduce capital, installation, and O&M costs. Energy yield losses are minimal and should not exceed more than 1% due to this effect alone.
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I tried to get a similar picture to the OP where the North panels are at 50W.
The East/West are at 209W vs the 277W from my original picture, but that power is already 20min earlier in the day as well, so I am not sure how much that influence the values.
Still, adding the West string did also add an extra hour or more of solar time in the evenings, so I will say it was worth it.
Why due East/West and not angled to the north?
During the year the location that the sun rises and sets change every day. It’s got to do with the tilt of the earth’s axis, which give the seasons. All those high school stuff. So what happens is that in middel of summer the sun actually rises in the south east in some places and sets in the south west. So this is not a fixed thing. It all depends on your location, how far you are from the equator and all that.
The best might be a picture, but a live picture is even better.
On the site http://suncalc.net/ you can go play with this. zoom into your location. Set the date to 24 Dec. and play with the timeline. Now set it to 24 June and play with the timeline again. Check where the sun rises (yellow line) and sets (red line).
Here I picked Struisbaai (the most southern point in SA)
Dec 24
vs Jun 24
So due East/West is a better avg. for the full year, trying to get the longest sun time that you can and leaving the batteries for when the .
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and
Thanks for this Louis, over time I have picked this up at some clients and recommend east west to as many clients where the roofs allow it.
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Thanks a lot Louis, really appreciate this. So leaving panels due East/West creates a better average during the entire year.
This is what threw me a bit, everybody just dissing slightly North orientation in the mix and I couldn’t understand why. In the Southern hemisphere, in winter a slight North orientation would thus definitely assist, and vice versa - in summer change to slight South orientation.
But I get it, fixed installations and depending on your roof type don’t allow for this which is why we should work in the average of straight East/West.
But in my particular case, because my panels are not fixed yet, changing the orientation will take me 20 minutes at most and I can do this.
Heck, I’m even thinking about a frame design now that will allow me to lever a panel at the sides up or down with different level settings which will give me the versatility to cater for both seasons.
Has no one done something line this before?
My array is slightly West of North, good for longer afternoon till a hill blocks the sun going down.
Now I CAN add more arrays facing for E/W but I chose to add a couple more panels to get longer peak hours from the slightly West of North facing array.
My point, many ways to skin these cats I tell you!
Very interesting thread.
Actually I was planning to have the same layout (2S2P) - two in series facing east and the other two - facing west connected to a single MPPT (SmartSolar 150/35) After reading Louis’ observations I feel encouraged this shall be OK and be able to achieve smoother yield throughout the day.
What should happen if both parallel strings are facing more unbalanced conditions - like the first one facing east-north, the second west-south. My assumption is that as soon as both reach the Vmpp voltage (which should be achieved easily after sunshine) the rest thing would be just summing the currents provided by each one that would vary during the day. Some of the articles state that this unbalancing degrades MPPT performance, inducing some losses due to different factors.
What are your observations on this?
Here I found a good case study of the topic from the far 2013, however very detailed and well-argumented.