Each panel
Unusual Generation in the Morning
- Thread starter BaldDave
- Start date
With all due respect, you have just jumped in and hijacked someone else's thread; suddenly making it difficult for me to answer the OP's questions.
Can you please start a new thread of your own and let me get back to @BaldDave 's issue
Last edited:
As @timselectric has said, this installation has been done incorrectly. You can't successfully mix east and west on one string.
The behaviour you describe is as expected for that configuration.
Get the installer's back to resolve it.
Okay thanks
Sergio95050
New Member
OK, I'll stick with OP topic and ask about technical details of the statement. Counting each panel in the [split] string have own OP, eg isolating from each other ?
timselectric
If I can do it, you can do it.
- Joined
- Feb 5, 2022
- Messages
- 19,853
Optimizers don't isolate panels in a string. They just try to keep them from pulling the rest down as much.
They Optimize each panel to minimize the losses as much as they can.
They Optimize each panel to minimize the losses as much as they can.
A bit more detail. The idea being that when the sun is rising on the East, the West panels in the shade of the roof do not limit the generation of-the East panels which are in bright sun with no shadows. So in the afternoon, the opposite. But what happens is that in bright sun (which this time of the year the East panels get from 5am) neither the west 6 or the east 6 on the string do much at all (around 20W total) Until the sun is much higher around 9am.
Today was an exception but should be normal….at 8am calculations show East 6 doing about 1700 when West 6 doing 250. Each panel has rating max output of 400W.
Comparing actual output to SolCast ‘estimated actuals’ on bright sunny days shows mostly that the PV2 doesn’t start to wake up until around 9am and operates well from around 10am. Then SolCast and what really happens are very close until sunset.
Today at 08:00 was a welcome exception. So I don’t think it’s a design fault but an intermittent issue
Sorry, my poor use of words.
Was it partially cloudy this am?
I have and E-W configuration (albeit correctly on 2 strings). When it is cloudy both strings will generate the same amount. If sunny and clear skies, the sun-facing string will generate more power.
AFAIAA, optimisers are designed to resolve partial shading issues, not fix a poor design.
What inverter do you have and what is Voc of your panels? Just trying to think of other configuration options.
I’m afraid I don’t know the answers to your last two paragraphs. I’m just an old bald homeowner!
In cloud, mine are the same as yours. In bright sun it’s all fine this time of year after around 9am.
Today at 8am was as you’d expect a good system in bright sun. Most unusual for mine! Per panel, the east doing about 7 times the west. That’s why I don’t think it is a poor design, but some kind of equipment failure.
Over a whole day I think it’s good. Recently it yielded 53 KWh in a day…but could have been around 60KWh if PV2 had worked well from sunrise.
So far in May 920 KWh
Summary: PV1, 12 West Panels
PV2, 6 east 6 west
Inverter 8KW, limited to 6KW export.
The only shadows this time of year is the apex of the roof itself.
Thanks for your input! I’ll look up your AFA stuff.
TomC4306
Solar Obsessive
No.
You misunderstood.
Sergio95050
New Member
Making max output of a panel's power when its voltage and current are variable (include shading) is main task of OP, IMO.
I'm still waiting for definitive technical note about poor design E-W positioning panels in one string, when OPs are there.
I’ll check!
Thanks! I’d love to have it. I know that about 8 years ago it was poor for inclinations above 15 degrees…but optimiser tech probably improved since then.
My 8am figures from today suggests it’s OK
Not sure what make of optimisers you have have, but Tigo is one of the most commonly used in the UK...
Hence, from Tigo themselves, they state... "If your PV modules are wired in series, and your design includes a hard angle (some facing east, and some facing west), the early morning and late afternoons may see a short period where there is a complete drop-off of production for the heavily shaded PV-Modules. This is a normal function of Optimization.
Tigo Optimization allows the strongest modules to produce at their best, through impedance matching. If there is light shading, the units will optimize for more current. However, if modules are heavily shaded, their output will be reduced so that the lack of current will now no longer affect the entire string's production."
See more info here.. https://support.tigoenergy.com/hc/e...em-for-different-tilts-angles-and-orientation
Their explanations in that article concur with the performance you have observed.
IMHO Optimisers should not have been used to try and get panels that are facing in 180 degree different directions to work on one MPPT string. The inverter will not be able to work properly in that manner. Hence my recommendation in post #28, "Get the installer's back to resolve it."
Hence, from Tigo themselves, they state... "If your PV modules are wired in series, and your design includes a hard angle (some facing east, and some facing west), the early morning and late afternoons may see a short period where there is a complete drop-off of production for the heavily shaded PV-Modules. This is a normal function of Optimization.
Tigo Optimization allows the strongest modules to produce at their best, through impedance matching. If there is light shading, the units will optimize for more current. However, if modules are heavily shaded, their output will be reduced so that the lack of current will now no longer affect the entire string's production."
See more info here.. https://support.tigoenergy.com/hc/e...em-for-different-tilts-angles-and-orientation
Their explanations in that article concur with the performance you have observed.
IMHO Optimisers should not have been used to try and get panels that are facing in 180 degree different directions to work on one MPPT string. The inverter will not be able to work properly in that manner. Hence my recommendation in post #28, "Get the installer's back to resolve it."
Thanks. I will.
But what can they do?
I know almost nothing about MPPT strings and thought they were just about battery charging. What are they - simply?
see https://en.wikipedia.org/wiki/Maximum_power_point_tracking
Essentially a technique inverters use for extracting the maximum power for any given light condition by adjusting current drawn from the panels. But this relies on all panels in the string having the same maximum voltage/current point as each other, which won't be the case when they are facing opposite sides of the earth.
What can the installers do? Thoughts that spring to mind include:-
a) Reorganise the configuration to have two west facing strings of 9 panels each on one MPPT and the remaining 6 east-facing on the other MPPT input? But that will depend on max voltage / current supported by your inverter.
b) Deploy an additional inverter so you can configure your system with 3 strings
c) Give you a refund for their incompetence and put up with the loss of generation
Essentially a technique inverters use for extracting the maximum power for any given light condition by adjusting current drawn from the panels. But this relies on all panels in the string having the same maximum voltage/current point as each other, which won't be the case when they are facing opposite sides of the earth.
What can the installers do? Thoughts that spring to mind include:-
a) Reorganise the configuration to have two west facing strings of 9 panels each on one MPPT and the remaining 6 east-facing on the other MPPT input? But that will depend on max voltage / current supported by your inverter.
b) Deploy an additional inverter so you can configure your system with 3 strings
c) Give you a refund for their incompetence and put up with the loss of generation
On closer reading, that’s not what is happening though…..
When in shade, (before around 08:30 on the westward side) the west side are generating very little if anything (as in the Tigo article)….and the ones in direct sun are also generating very little if anything (not like the Tigo article)! The whole string is only producing 20W.
It was like that today until 8am…then the string suddenly ramped up, the westward may have been producing a little - I can’t tell - but the east certainly at least 1700
Thanks for your thoughts! I’ll talk to them next week.
Hmmm, their wording is not very clear, but they specifically say "If your PV modules are wired in series, and your design includes a hard angle (some facing east, and some facing west), the early morning and late afternoons may see a short period where there is a complete drop-off of production for the heavily shaded PV-Modules. This is a normal function of Optimization"
I take that to mean complete drop off of the string that contains the "heavily shaded PV-Modules"; I could be wrong, but if they didn't mean that, all they are saying is that heavily shaded panels won't produce power (which is kind of obvious).
But looking at the article I linked to, in example 2, where there are is one string of 12 panels, 6 south and 6 west, they specifically say...
"Tigo recommends dividing the string into two separate strings in series going into separate MPPTs"
Sergio95050
New Member
In post#26 @BaldDave replied: each of panel in the string have own optimizer.
Yes indeed. Thank you. That’s a strong recommendation. I think my optimisers are Tigo.
I’ll talk to the installers next week.
I only have my data to go on… but think 53 KWh on a sunny day in May is pretty good…but 60 would be better!
What do you think of my yield?
I’ll talk to the installers next week.
I only have my data to go on… but think 53 KWh on a sunny day in May is pretty good…but 60 would be better!
What do you think of my yield?
Yes, I understand that... how does that relate to their recommendations though?
Sergio95050
New Member
That's seems OK for me , if you have one optimizer/MPPT for whole string .
Similar threads
