Given this house of my friend that is not facing North, what is the best configuration - all 10 panels West, or 5 East and 5 West on separate MPPT's?

He has x10 Canadian Solar 605W's

Given the fact that his optimal azimuth angle is slightly east it makes more sense to put all 10 panels on the eastern side of the second storey?

 

 

Edited August 2, 20233 yr by L_D
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If that big chimney shadow misses the roof then I would put all on that north/east side. but afternoon production may be on the lower side, which does not matter too much if the batteries are not being used too much in the afternoon.
Maybe aim for more panels and add those extra to the west side to compensate/boost the afternoon production.

Those panels are VMPP: 34.9 V and Voc 41.3 V so 10 in series on one mppt maybe just on the safe side and depending on the inverter? may have some clipping of the current produced. Those panels are about 17amps.

Edited August 2, 20233 yr by WannabeSolarSparky

If the budget isn't a major factor (just kidding), I would split up the panels between east and west and incorporate adjustable frame structure with tracking. (Just me being courageous here 🙂 )

What is the % drop in productivity from North to East and West in SA?

1 hour ago, L_D said:

What is the % drop in productivity from North to East and West in SA?

It was indicated as 15% by @TaliaB

46 minutes ago, Scorp007 said:

It was indicated as 15% by @TaliaB

 

Took my neighbour up the street's stats from his setup that is pointing N, E & W on separate MPPT's.

The drop in efficiency if you take North as optimal with no loss is larger than 15%.

 

East was 40% and West 47% which is in line with the azimuth angle at 19 degrees.

 

58 minutes ago, L_D said:

The drop in efficiency if you take North as optimal with no loss is larger than 15%

This is where true facing direction come in. If east "facing" panels are more south east than north east you will get n bigger loss the same applies for west facing roofs. It is very seldom that a building faces true north(magnetic north0°) and same for east and west. The most accurate way to determine this is using a compass. 40% and 47% loss tend to let me believe the panels are not facing east or west but leans more to south/east and south/west

Edited August 2, 20233 yr by TaliaB

1 hour ago, TaliaB said:

This is where true facing direction come in. If east "facing" panels are more south east than north east you will get n bigger loss the same applies for west facing roofs. It is very seldom that a building faces true north(magnetic north0°) and same for east and west. The most accurate way to determine this is using a compass. 40% and 47% loss tend to let me believe the panels are not facing east or west but leans more to south/east and south/west

Thanks for the reply. Now the question can be taken further. With magnetic north out by a number of degrees does the sun true east and west "work" on  true east and west? 

@L_DThanks for the measured values. Never looked into this but my gutt also told me that east produces more than west. 

Less of a problem for US but more as we move east from ZA. 

 

 

Edited August 2, 20233 yr by Scorp007

 

Here is an extract from Green Energy solutions:

 

"Based on a solar system installed in Johannesburg, at a 25 degrees incline, the following table illustrates the different yearly energy production" 

North 0°              1 730 kwh/kwp

North East 45°    1 650 kwh/kwp

East 90°                1 474 kwh/kwp

West 270°             1 516 kwh/kwp

North West 315°   1 673 kwh/kwp

Edited August 2, 20233 yr by TaliaB

22 hours ago, L_D said:

What is the % drop in productivity from North to East and West in SA?

It depends very much on the season. In winter when the solar day is short and you want your panels to be performing optimally, you really really want them to be pointing north.

Looking at an annual average doesn't give you the whole picture.

34 minutes ago, PierreJ said:

It depends very much on the season. In winter when the solar day is short and you want your panels to be performing optimally, you really really want them to be pointing north.

Looking at an annual average doesn't give you the whole picture.

Yes i very much agree with you on North facing been the most effective, but it is not always possible due to roof orientation and space so it is good to know what secondary directions will yield for an informative decision on solar array design. I quoted on a system for a client where he actually agreed to face 16 panels North in 2 rows behind each other, front row at 6° inclination and the back row at 26° inclination then we might have best of both worlds.

Edited August 3, 20233 yr by TaliaB

16 hours ago, TaliaB said:

Johannesburg, at a 25 degrees incline, the following table illustrates the different yearly energy production" 

N 0°         1 730 

13.5kWh

N E 45°    1 650 

12kWh

E 90°     1 474

8.8kWh

W 270°  1516

8.8kWh

N W 315°   1 673 

12.1kWh

Expand your quote to see my figures for my location for a specific array at 28 degrees for the actual forecast weather for today. Mine directly below your annual figures. 

These figures from a forecasting APP taking into account the weather. 

The problem comes in the data used for forecasting. Below is the weather from 2 different APPS for my actual location. Top one shows full sun. 

No wonder the results always vary so much from 1 APP to the next. So far my trusted APP in the 2nd picture is spot on.

 

Edited August 3, 20233 yr by Scorp007

1 hour ago, PierreJ said:

It depends very much on the season. In winter when the solar day is short and you want your panels to be performing optimally, you really really want them to be pointing north.

Looking at an annual average doesn't give you the whole picture.

Here are my figures for 2022. I have no wasted PV. Winter short days are treating me well. In summer clouds affecting me more than what one would think. Don't laugh at the low values per month. 

I have a friend with a similarly oriented roof.  The panels on the WSW side will do very close to nothing in the winter.  They help for late power in the summer because of where the sun sets.  If your battery is big enough, everything on the ENE side would give you biggest yield, otherwise maybe a 80/20 or 70/30 split might be better.  I would definitely not go 50/50.  Use https://pvwatts.nrel.gov/ to run some simulations...

2 hours ago, Scorp007 said:

Here are my figures for 2022. I have no wasted PV. Winter short days are treating me well. In summer clouds affecting me more than what one would think. Don't laugh at the low values per month. 

At a quick glance from Jan - Apr + Sept-Dec( Summer) your total was ~ 1500 kwh and from May- Aug(Winter) your total was ~800kwh very well balanced like you say cloud cover and higher temps affects the output in summer but winter helps due to clear colder days more effiecient panels. You had a nice boost in Aug though.

 

1 hour ago, TaliaB said:

At a quick glance from Jan - Apr + Sept-Dec( Summer) your total was ~ 1500 kwh and from May- Aug(Winter) your total was ~800kwh very well balanced like you say cloud cover and higher temps affects the output in summer but winter helps due to clear colder days more effiecient panels. You had a nice boost in Aug though.

 

Yes Aug and Sep we tend to have less clouds and lower temps. In the year shown we had that heavy rain over the whole Easter which also made a dent as can be seen. 

Year to year it can vary so much. This year the high LS is also taking its toll if 10h-14h like today having LS 10-12h.

But hey my system has long gone paid itself of. Only 4yrs. So every kWh from PV is free.