Solar PV shading issue opinions please

mickyduck55

I know shading is an issue bringing the complete string down unless using something like solar edge.  This is a photo taken when the panels were delivering 256W, the previous couple of hours producing over 2kW.

Would this shading from the soil stack be enough to bring the whole array down?

This NOT my system as described in the signature .. its my sons installed about a month ago

Martyn1981

My gut feeling is that it shouldn't / couldn't do that much 'damage'. But if you are relatively competent at DIY and with ladders then you might want to shorten it a bit, especially as the roof pitch is towards the safer end for working. But please, please be careful and have a buddy to help / keep an eye on you / ring the ambulance / film it for a laugh!

My install was also Summer 2011, and back then I might have thought differently, but my ESE panels butt up against a chimney to their south, and they still performed roughly at PVGIS, though they are a tad better now that they've been Solaredge'd, but only a bit better than the difference in inverter efficiencies, so no great boost.

Of course I'm only guessing, but perhaps there may be another explanation for the drop off in gen???

mickyduck55

Martyn1981 said:

My gut feeling is that it shouldn't / couldn't do that much 'damage'. But if you are relatively competent at DIY and with ladders then you might want to shorten it a bit, especially as the roof pitch is towards the safer end for working. But please, please be careful and have a buddy to help / keep an eye on you / ring the ambulance / film it for a laugh!

My install was also Summer 2011, and back then I might have thought differently, but my ESE panels butt up against a chimney to their south, and they still performed roughly at PVGIS, though they are a tad better now that they've been Solaredge'd, but only a bit better than the difference in inverter efficiencies, so no great boost.

Of course I'm only guessing, but perhaps there may be another explanation for the drop off in gen???

Hi Martyn

This is not my system so have edited post above.. I have already decided it needs chopping but will sit there and watch one day as the sun moves and watch the generation before I risk my life up there LOL

Thanks

pinnks

I think it is possible that the sewage stack shadow is the cause.  I have shading from my chimney on my SSE array (1750Wp).  When in full sun it generates about 1600W but as soon as the chimney pot shadow, not the chimney stack, just the pot on top, hits corner of one of my 7 panels, generation drops by about 90%.  That seems to be similar to what you are seeing.
A point to consider is that the sewage stack exit must be a defined height above any window (80 or 100cm I think), so you might want to consider running it at tile level up and under the panels, or re-routing in the attic and exiting the roof via a mushroom tile.  This is what we have (pre-PV install) and the mushroom tile is now under one of the panels.

ABrass

One way to test it would be to hop up a ladder with a bit of pipe, just before the shade from the soil stack hits it, then poke a pipe up to replicate the shadow and get someone to check the output. Then remove it and see if it springs back. Usual advice about working at height applies.

thevilla

Personally I won't be hopping up any ladders until the current emergency is over.  Why risk an A&E visit or worse.  Do you need the ventilator priority call?  Be safe and put up with a few kwh loss for a few months.

Martyn1981

mickyduck55 said:

Martyn1981 said:

My gut feeling is that it shouldn't / couldn't do that much 'damage'. But if you are relatively competent at DIY and with ladders then you might want to shorten it a bit, especially as the roof pitch is towards the safer end for working. But please, please be careful and have a buddy to help / keep an eye on you / ring the ambulance / film it for a laugh!

My install was also Summer 2011, and back then I might have thought differently, but my ESE panels butt up against a chimney to their south, and they still performed roughly at PVGIS, though they are a tad better now that they've been Solaredge'd, but only a bit better than the difference in inverter efficiencies, so no great boost.

Of course I'm only guessing, but perhaps there may be another explanation for the drop off in gen???

Hi Martyn

This is not my system so have edited post above.. I have already decided it needs chopping but will sit there and watch one day as the sun moves and watch the generation before I risk my life up there LOL

Thanks

Cheers, that makes sense as I did wonder why you hadn't asked in the past. Classic case of me adding 2 and 2 and getting 5.  ;-)
Regarding the vent, you can install an internal cap (air admittance valve) instead if you have access to the pipe, remember these aren't mainly to 'ven't' the soil pipe, but to allow air in to prevent a syphoning effect that will empty the toilet bowl and other bathroom traps of water when flushed and allow smells to enter the property.

Pile_o_stone

Regulations state that vent pipes that are situated within 3m of an opening window must terminate at least 900mm above the eaves (i.e. gutters). You may be able to cut down the soil stack, but make sure you are within the regs. If you can reduce the pipe so it doesn't cast a shadow, that'd be the best solution.

If you can't cut down the pipe and all of the panels are in a single string (likely), then one panel being shaded will bring down the output of the other panels. This does not happen If you use solar power optimiser (i.e. Solar edge, Tigo, etc.). These isolate a panel so that if it is shaded then the loss of power only impacts that panel and not the others in a string.

I have SMA tigo optimisers on my panels and they cost about £50 each. They fit onto the back of the solar panels and work with any inverter. The great thing is that you only need to add then to the panels that need them (i.e. the ones that are shaded). https://www.sma.de/en/products/smart-module-technology/ts4-r.html

In your case, you may get away with adding them to the bottom 1, 2 or three panels in the array.

EricMears

That stacks looks as though it's a 4" diameter pipe (more likely 100mm these days !).  Since it's only there to admit air,  you could consider fitting a reducing collar at or just below level of panels then continue upwards to whatever height is mandated in a much narrower pipe (1" ?)

FoldPV

What about replacing the pipe with something like a curve pipe 45°? It delivers air in a similar way

pinnks

You can absolutely have a bend in the stack but it must terminate 900mm above the eaves as stated.  It matters not whether you make the changes externally of internally, though for aesthetic reasons internally may be better.
When we extended our house the stack pipe had to be re-routed as we built on the back of the house with a pitched roof at 90 degrees to the main roof just where the original pipe exit was.  The pipe now does 2 x 90 degree bends in the attic and then has a vent tile as its outlet to the environment appropriately high up the new roof (building control signed off on it) - something like this, which has a flexible pipe to connect to the stack pipe :
 
This vent tile is now under one of my panels, though that is easier to achieve then the panels are installed after the tile of course.