Unusual Generation in the Morning

[BaldDave]

I have a string with 6 panels facing east and 6 west. All are optimised. In bright sun in the morning - before around 9am typically, with no shadows - the whole string produces around 20W instead of well over 1000W. By noon, the string is generating 3000W…the same as a fully west facing string of 12. At low generation times, the voltage of that string is over 400…and falls when lots of power is generated. Any ideas of what’s going wrong?

 

[chrisski]

I have a string with 6 panels facing east and 6 west. All are optimised. In bright sun in the morning - before around 9am typically, with no shadows - the whole string produces around 20W instead of well over 1000W. By noon, the string is generating 3000W…the same as a fully west facing string of 12. At low generation times, the voltage of that string is over 400…and falls when lots of power is generated. Any ideas of what’s going wrong?

Nothing may be wrong. A lower voltage when producing near max production is hitting the lower Vmp on the panel. A higher voltage (VOC) is natural in good sunlight when there are not enough photons hitting the panel in the early morning sun.

With panels in direct sun, I'm puzzled why so far north with east facing panels it is only 20 watts until 9 am. Are the panels shaded at all in the morning?

 

[BaldDave]

Nothing may be wrong. A lower voltage when producing near max production is hitting the lower Vmp on the panel. A higher voltage (VOC) is natural in good sunlight when there are not enough photons hitting the panel in the early morning sun.

With panels in direct sun, I'm puzzled why so far north with east facing panels it is only 20 watts until 9 am. Are the panels shaded at all in the morning?

No. That’s the strange thing. The west 12 can be producing 600W early so the 6 east on that east/west should be doing about 300, the east 6 should be around 1000. But instead of a total on the string on 1300…it’s 20!

 

[BaldDave]

Nothing may be wrong. A lower voltage when producing near max production is hitting the lower Vmp on the panel. A higher voltage (VOC) is natural in good sunlight when there are not enough photons hitting the panel in the early morning sun.

With panels in direct sun, I'm puzzled why so far north with east facing panels it is only 20 watts until 9 am. Are the panels shaded at all in the morning?

Sorry typo…with the west 12 doing 600 the west 6 should be doing 300….total of east/west split string should be around 300+1000=1300, but it’s only 20. The east panels have no shadows on them until 4pm this time of year.

 

[timselectric]

All panels on a series string should face the same direction.

east/west split string

This is the problem.

 

[BaldDave]

All panels on a series string should face the same direction.


This is the problem.

I wondered that but have found some folk with east/west split in my area with great results.

 

[Brucey]

I wondered that but have found some folk with east/west split in my area with great results.

You can do an east west split but combine them at a combiner box don't connect it all as one continuous string.

 

[timselectric]

I wondered that but have found some folk with east/west split in my area with great results.

They are probably two separate strings in parallel.

 

[BaldDave]

They are probably two separate strings in parallel.

I’ll check that, thanks. But they said they had 3 east and 9 west on one string.

 

[BaldDave]

You can do an east west split but combine them at a combiner box don't connect it all as one continuous string.

Thanks. I’ll look into that…never heard of a combiner box…just used optimisers on all.

 

[SeaGal]

I have a string with 6 panels facing east and 6 west.

with the west 12 doing 600 the west 6 should be doing 300

Bit confused how many panels you have in each direction.

How are the East and West strings wired? You will need two strings, one for east and one for west, each attached to a separate MPPT input on your inverter for that configuration to work successfully.

Can you also confirm what inverter you have?

Is this a DIY install or has it been installed for you?

 

[timselectric]

I’ll check that, thanks. But they said they had 3 east and 9 west on one string.

It sounds like they don't really know what they have.
As that would perform very poorly.

 

[Sergio95050]

All panels on a series string should face the same direction.

I'm curious about your technical explanation of my setup (done by local company): one string with 18 panels, each equipped with own optimizer and connected to 1ph inverter (SolarEdge's OPs and the inverter).
The string spitted to east faced slop (2 panels), south slope - 6 panels and west slope - 10 panels.
Here is a sample of energy produced during one sunny day.

 

[timselectric]

The string spitted to east faced slop (2 panels), south slope - 6 panels and west slope - 10 panels.

If a company actually installed it this way. They have no business doing solar system installs.
You didn't say what panels you have. But I'm sure that they could be producing a lot more if installed correctly.
18 panels seems like a lot for one string.

 

[Sergio95050]

It's a mix of 205W [Dasol DS-A3-205], 250W [Aventia AVN250EP-60] and 260W [Amerisolar AS-6P30] panels with own SE optimizers (MPPT). Total Vdc of the string is around 360VDC and 450VDC during clipping time as the inviter [SE3000] limited to make 3kWp.
I'm looking for technicality...

 

[timselectric]

It's a mix of 200W, 250W and 260W panels

This just keeps getting worse.
Who is this crap company? People should be warned about them.

 

[Sergio95050]

You do scare me !
I'm listening to technical details ...
Personally, I don't see any problem - each one is producing as much as the optimizer can pull from it; then the invertor is orchestrating the OPs to keep the string parameters. Total power/energy is correlating with sunlight direction and intensity ...
Where is the issue ?

 

[hwy17]

We might not understand the weirdness solar edge does with Optimizers. They're very uncommon in DIY.

 

[Sergio95050]

the weirdness solar edge does with Optimizers

That's what I'm still curious last 8 years

 

[BaldDave]

Bit confused how many panels you have in each direction.

How are the East and West strings wired? You will need two strings, one for east and one for west, each attached to a separate MPPT input on your inverter for that configuration to work successfully.

Can you also confirm what inverter you have?

Is this a DIY install or has it been installed for you?

Thanks
Installed by a contractor.
PV1, 12 West
PV2, 6 West 6 East
PV1 is superb
PV2 doesn’t ’wake up’ in bright sun until around 9am, then jumps from 20W to around 300W then later, say 10:30 is fine until around 16:00. This time of year.
Inverter is 8KW but export limited to 6KW

In bright cloud, PV2 works better than bright sun before around 9am

I think there must be an intermittent optimiser failure. At 08:00 today, unusually good results….as you’d normally expect….PV2 (east 6 west 6 split), 2000 , PV 1 all 12 west 500. So that means 6 east approx 1750. Pretty good. But that’s very rare!

 

[timselectric]

You do scare me !
I'm listening to technical details ...
Personally, I don't see any problem - each one is producing as much as the optimizer can pull from it; then the invertor is orchestrating the OPs to keep the string parameters. Total power/energy is correlating with sunlight direction and intensity ...
Where is the issue ?

I don't mean to scare you. I'm not saying that it's dangerous in any way. (Unless 18 panels exceed the VOC limit of the inverter)
It's just a very inefficient design. I hope you didn't pay too much for what you ended up with.

 

[BaldDave]

It sounds like they don't really know what they have.
As that would perform very poorly.

It performs well!

 

[Sergio95050]

I think there must be an intermittent optimiser failure.

Is that means each panel have own OP or each string ?

 

[timselectric]

It performs well!

Then, they probably don't know what they actually have.

 

[timselectric]

To clarify.
When panels are connected in series. (A string)
They act as one.
Placing them at different angles to the sun, is the same as shading some at all times.
Optimizers can help with shading. But should not be used to correct a bad design.
And mixing different panels only makes things worse. As all panels in a string can only be as good as the worst one.
(A chain is only as strong as its weakest link)