The effects of shading on solar PV

theboylard

If you have windows 7 (dunno about 8), then you have "snipping tool" in all programs/accessories.

Get whatever you want on your screen, launch snipping tool and expand the screen area to desired shape. Then save or copy it to wherever you need to.

In true blue Peter style, here's one I prepared earlier...

Martyn1981

pinnks wrote: »

The system went in in March last year and was projected to produce 1,621kWh. It actually produced a few kWh more than that despite the impact of the TV aerial mentioned in the first post in this thread.

Using default settings in PGVIS for Swindon, 1.75kWp, -20 orientation and 45 degree slope it returns 1,670, so a mere 50 more than I achieved with that TV aerial shading for the first 3 or so months from memory.

Not sure what to conclude from that...

To (partly) account for weather, which as Eric points out will impact on annual figures, have you also PVGIS'd your other system? Seeing how the WSW compares to PVGIS may give you a better idea as to how the SSE performed, since last year was quite a good year (for me) at 108% of target.

Obviously weather can throw this out a bit, since morning and afternoon weather can be different, but for my systems, I've generally found that this balances out a lot over a month, and doesn't seem to have any significant effect over a year.

Not sure that makes any sense having moved from my brain to my fingertips. So here's another go:
If the ESE performed roughly at 100% of target, then it may look fine, but if the WSW performed at 110% over the same period, then that might suggest a shading impact hidden by good weather during the time period.

Mart.

Waywardmike

I found this thread incredibly interesting...

I'm in my eighth month since install and the things I knew would cause shading have little impact (too late in the day to have any significant reduction in generation) and there is shading I didn't expect.

There is a lamp post outside my neighbours house that in dec-feb casts a shadow across the bottom corner of the panels in the afternoon, and the impact is huge, sadly there's nothing I can do about it, although I have asked the neighbour nicely to back into it when pulling out his drive with his truck.

Also and something I didn't account for is there is a chimney in the centre of my roof which has had no impact up to now but as we go into my first summer months since install I'm certain it will. Thankfully it's not used and we planned to pull it down anyway so that may happen sooner rather than later.

Currently we have an open field in front of our house so I get no shading from any thing else from sunrise to sunset in the winter months which probably accounts for the fact that I've been above PVGIS for 6 out of the last 7 months (142% and 137% for Dec and Jan) even with the lamp post.

I'm actually looking forward to seeing what affects the panels at every point in the year when I get to year end, but I'm a research scientist so am a bit of a data geek and make a living out of observing such things!

theboylard

I have data from my install last year which will be a nice comparison with the retro install of solar edge in January. I'll see of I can get a similar day graph for April last year, so you'll be able to see the effect from the chimney.

That's for later though, out working now

silverwhistle

I don't monitor my ssytem very closely: apart from checking that the hot water tank is full and whether it's OK to put the washing machine on.

So I'm really not going to be able to tell if this second year of generation will be better... Last summer I had a chimney liner put in, so I asked the guys to remove my TV aerial as I don't watch it. The pigeons no longer have a convenient perch over my panels pointing SSW to Rowridge, and last year's liberal splattering of guano is now just an occasional in-flight evacuation.

Will this make much of a difference, I ask myself?

pinnks

Mart,

Good point and I did follow your brain dump.

Installer projection for the other roof WSW, was 2790; PVGIS 2870; actual 2930, so produced more than forecast by about 2%.

Installer projection for SSE roof was 1621; PVGIS 1670; actual 1615 (actually checked over the same periods). This is about 3.5% down.

So, one could perhaps surmise that, all things being equal, the SSE array is 5.5% down? That would be rounded to about 100kWh per year.

If that is a reasonable way to guess then even a DIY install, hanging off the ladder and hoping not to drop the panels while fixing the PO would never repay itself - lol.

1961Nick

The effects of shading are explained in this article (not too geeky).

http://sargosis.com/articles/science/how-shade-affects-a-solar-array/

zeupater

pinnks wrote: »

... So, one could perhaps surmise that, all things being equal, the SSE array is 5.5% down? That would be rounded to about 100kWh per year ...

.... or that for your location, mornings are generally cloudier than afternoons ! .... without detailed information you couldn't really say how much of the reduction is due to the shading, but that's where your SMA inverter's stored data comes in handy. Sunny Explorer software (free to download from SMA) has the ability to download data in .csv format, so comparing actual output to a smooth curve within a spread-sheet would allow a rough estimate of losses to be made. If you have the remote Sunny Beam display you should also be able to download data from that directly via USB.

Anyway, back to your issue .... you mention that the inverter is a 'SunnyBoy 1600', so check whether the model (?SB1600TL?)has OptiTrac Global Peak shade management and, if so, whether the installer enabled it .... If the combination is 'Yes' & 'No', get it turned on (Sunny Explorer), make a coffee and sit back & relax ...

HTH
Z

pinnks

You are of course correct re the morning v afternoon weather and probably a whole load of other variables.


I do indeed use Sunny Explorer via Ethernet and download the data regularly already - bit of a data geek. If I have a bout of insomnia I might have a go at that...


Unfortunately the 1600 does not have Optitrac. I came across it recently and enabled it on the 4000 inverter. Seems to help for the minimal shading that one gets. I mailed SMA and they confirmed the 1600 does not have Optitrac - shame. The 2100 has it tho...


So, still between a rock and a non-soft place.

pinnks

The shading article is certainly interesting.