PV shadow and midnite modes

fca1 · July 2013

Hi today was my first day of the midnite 150 +3000w PV system ...
I have 4 strings in parallel of 3 serial connected modules (Luxor 250w mono) 4p x3serial
Unfortunately 2 strings have one of their 3 panels in shade all morning by a chimney

And for what I see today in morning that 2 strings had almost zero output...
And in the afternoon with no shading batts were already charged ( I'm wasting power today, to test tomorrow

)

So my question is what can I do minimize this shadowing issues ( beside taking the chimney down. )

I see that the midnite have 2 modes legacy p&o and dinamic mode, can this modes help ?
I see that these settings can be tuned any suggestions ?

Regards

Vic · July 2013

Re: PV shadow and midnite modes

If some of your PVs are shaded, there is no CC mode that will make power from reduced/no input.

If you do not want to remove the chimney, then, of course, the next to consider is moving the array.

Sometimes, one can wire the array such that the shaded PVs tend to be in one string. But, as shadows move this is a balancing act, especially when you consider total output for the entire year.

Placement of PV arrays is very important for maximizing production. Opinions, Vic

NorthGuy · July 2013

Re: PV shadow and midnite modes

Assuming you're in the Northern hemisphere.

If the chimney is generally on the East side then things may get better during the Winter time. In winter, Sun moves more to the South. If your system is sized for winter (meaning you have some power to spare in the summer time), and shading doesn't last too long, it might be Ok as it is.

SolarMusher · July 2013

Re: PV shadow and midnite modes

Maybe you could rewire your pannels to have just one string shaded, better than nothing.
If you are 24V, you could also wire 2 series x6 and have a better efficiency, if it's not too far.
Erik

fca1 · July 2013

Re: PV shadow and midnite modes

Vic wrote: »

If some of your PVs are shaded, there is no CC mode that will make power from reduced/no input.
If you do not want to remove the chimney, then, of course, the next to consider is moving the array.

i understand that no CCmode will give me power where it doesn't exist im looking for a mode that minimizes the loss on strings not shaded because of the 1 or 2 being shaded...
Today i see one time that my voltage where at 55 volts and i can only understand that with the shadow pv affecting the other , for now this is ok because im still at 24v but i'm moving for 48v and this will be a problem...

Chimney can't come down, and pv array (no more roof) maybe i could move one of the string panels to other end but thats it one of strings will always have shadow..

what i don't want is to have a string of 750W that instead of giving power is taking power, so it would be better to turn off that one

yes this will be worst in summer as in winter the sun rises more to the right

fca1 · July 2013

Re: PV shadow and midnite modes

SolarMusher wrote: »

Maybe you could rewire your pannels to have just one string shaded, better than nothing.
If you are 24V, you could also wire 2 series x6 and have a better efficiency, if it's not too far.
Erik

6 x 37v =222V, classic can only go up to 150v...
luxor specs http://www.luxor-solar.de/root/img/pool/pdf/lx_db_ecoline60mono_full_black_240-255w_en.pdf
i have tough in 4x but was to close the 150v, but even so 3x37 voc or 3x31 vmp i should have ~93v and today i had see 5x volts coming in ...

logging is enabled now, so tomorrow (if sun collaborate) i will see what happens and later on i will test disconnecting the shaded strings and try to work out the midnite modes to see if i have some improve...
first day, so not conclusions just beginning...

Cariboocoot · July 2013

Re: PV shadow and midnite modes

You've got twelve panels total in an array that is all 'tight together'. There are four strings of three panels in series. One panel in each of two of these strings is getting shaded, effectively knocking out two of the strings. This is costing up to 50% of the power.

Rewires so that both of the shaded panels are in the same string. Then only one of the strings gets knocked out. This will cost up to 25% of the power. It does not matter the physical position of the panels; ones in two different rows can be wired to the same string (if you have enough wire).

There's nothing can be done with any charge controller to make up for a lack of power coming in from the array.

fca1 · July 2013

Re: PV shadow and midnite modes

Very hard the rewiring because of their position and always 2 on the shading , but i will put camera on the roof to analyse it well, i was counting with tha shading affecting those strings, but why is bring me down the voltage of all strings ?

regards

SolarMusher · July 2013

Re: PV shadow and midnite modes

fca1 wrote: »

6 x 37v =222V, classic can only go up to 150v...
luxor specs http://www.luxor-solar.de/root/img/pool/pdf/lx_db_ecoline60mono_full_black_240-255w_en.pdf
i have tough in 4x but was to close the 150v, but even so 3x37 voc or 3x31 vmp i should have ~93v and today i had see 5x volts coming in ...

logging is enabled now, so tomorrow (if sun collaborate) i will see what happens and later on i will test disconnecting the shaded strings and try to work out the midnite modes to see if i have some improve...
first day, so not conclusions just beginning...

I was thinking 2 serie x6 parallel something around 60V at your PV output to charge your 24V batteries, efficiency would be better.
Also 3kw PV is a little high for a CL150 on a 24V system you may need to limit it at 90A max or to check before with Midnite sizing tool.
As Coot said, try to re-wire with just one string shaded in the morning would be your best choice.
Erik

inetdog · July 2013

Re: PV shadow and midnite modes

Cariboocoot wrote: »

You've got twelve panels total in an array that is all 'tight together'. There are four strings of three panels in series. One panel in each of two of these strings is getting shaded, effectively knocking out two of the strings. This is costing up to 50% of the power.

Rewires so that both of the shaded panels are in the same string. Then only one of the strings gets knocked out. This will cost up to 25% of the power. It does not matter the physical position of the panels; ones in two different rows can be wired to the same string (if you have enough wire).

There's nothing can be done with any charge controller to make up for a lack of power coming in from the array.

If the shade is going to move across a panel or only cover part of the panel, look at the way the panel is wired and the orientation. If you can, have the shade cover all or most of the area protected by one bypass diode and none of the other one or two areas. During the time that the shade covers at least one cell in each of the bypass groups, there will be no useful output from the panel at all.

A CC or GTI with two separate MPPT inputs, or use of microinverters can both help optimize the total output from a partially shaded array.

fca1 · July 2013

Re: PV shadow and midnite modes

Hi there here quick photo of the problem
Attachment not found.

And here the graph that shows the amps going out of the midnite when the shadows stop at 12:45
Attachment not found.

As you can see it goes from 30amps to 72 amps in flash..
I think I can reorganize them with some messy in vertical strings instead of horizontal...

And like this I would only loose one string instead of 2 at least one string will be unshadow first ..

Question about shading, does the shadowed string affects the non shadowed I mean the loss is only from non power from the shadowed or by being paralleled with a non shadow will also make the non shadow loose power?

Regards

BB. · July 2013

Re: PV shadow and midnite modes

A shaded string should not affect the output of a parallel connected non-shaded string.

-Bill

Cariboocoot · July 2013

Re: PV shadow and midnite modes

With a shadow on one panel of string it will only affect that string: knocks out the current of the shaded panel. Voltage will stay high because of the illumination of the other panels. Similar to getting Voc from a panel with minimal illumination but it lacks the ability to produce significant current.

That chimney seems to be casting on three panels in a row there, and there's darkness on the next ones down as well. Looks like the shadows are costing you about 1/2 your array.

Can you do a pic straight on to the whole array for us to look at?

NorthGuy · July 2013

Re: PV shadow and midnite modes

You could try to move the top row of panels to the space below the chimney (if it's enough width).

Another idea, is to tilt the whole array relative to the roof so that the top row of panels would be entirely above the chimney.

fca1 · July 2013

Re: PV shadow and midnite modes

Cariboocoot wrote: »

Can you do a pic straight on to the whole array for us to look at?

Tomorrow will do a pic of all roof ... Like this I'm loosing half of the array until 13:00

If my idea will work I will hopefully have 3 strings major part of the time, instead of 2 ...

zoneblue · July 2013

Re: PV shadow and midnite modes

Alas the real world sometimes sucks. I think the primary problem is that the panels are badly located. I guess thats obvious, and i know roof space is finite. However if you reduce your expectations from them, then there isnt anything inherantly 'wrong' about it. For example some grid tie folk sometimes lean half there panels west and half east, that gives them a better day spread if a lower total output. But putting them some place else is a better idea if you want full output.

Its something you might contemplate, tipping them away from the shadow, toward the sun they *do* get.

Im not telling you anything you dont know. Is that space beyond the chimney not yours?

inetdog · July 2013

Re: PV shadow and midnite modes

zoneblue wrote: »

For example some grid tie folk sometimes lean half there panels west and half east, that gives them a better day spread if a lower total output.

Some off-grid folks do the same thing to get better battery charging. It goes without saying (so I say it) that all of the east panels will be in one string and all of the west panels in another string or set of strings. Do not mix east and west panels in a string.

fca1 · July 2013

Re: PV shadow and midnite modes

here you a "quick dirt" photo....
as is now...

Attachment not found.

I will bring the panels closer to chimney one goes down (where it was planned).. and the other on top of the roof window (will block my acesso to roof by this window..
also will create a string with panels more away from the chimney in vertical way ...

here a dirty photshop...
Attachment not found.

Cariboocoot · July 2013

Re: PV shadow and midnite modes

You really have a problem there. I see a lot of shading, not just two panels. I take it the space on the other side of the chimney is someone else's roof? And there appears to be a vent or hatch between the two sections? Those sat dishes aren't helping any either.

Moving them as you propose should help, but you can still see chimney shadow will be falling on some. Without a radical change that you no doubt can not make I don't see any way of improving it beyond that. Sorry.

fca1 · July 2013

Re: PV shadow and midnite modes

Cariboocoot wrote: »

I take it the space on the other side of the chimney is someone else's roof? And there appears to be a vent or hatch between the two sections? Those sat dishes aren't helping any either.

yes the other roof is from my neighbour, i could ask him to move panels to his roof

ehehhehe
yes roof window..

Cariboocoot wrote: »

Moving them as you propose should help, but you can still see chimney shadow will be falling on some. Without a radical change that you no doubt can not make I don't see any way of improving it beyond that. Sorry.

That shadow is really big on that 2 panels what you see in picture on bottom is more "mirror" defect than shadow... i have camera setup on the roof, tomorrow i will do fastmovie of day shadow..
already ordered additional mc4 cables for the move..
today even with that small shadow and in absorb mode (putting my inverter at maximum) i got 2000W 71 amps i was expecting a 30% loss over the 3000W that would be like 2100W..
So i'm almost at what i was expecting, just need to buy a bigger inverter so i can use all my pv, (still in doubt on the victron quattro or the sunnyisland)..

Regards

thanks

PV shadow and midnite modes

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