shading - not sure

rosythfifer

Hi all

I am not sure if i have a shading issue or not. The sun is out but at 1640 its low and to the west. My house is due south but has a small ridge over 1 bedroom. I have a single panel close to this. My generation is sat at 0.4 KWh. With hoe bright it is i would expect more.

Now looking at the roof its hard to tell if the ridge is casting a shadow on the single panel. If it is then it can only be a small one.

Should i be concerned? Is their anyway to check?

rosythfifer

Ill try another question

On a string of say 9 panels, if 1 panel was to become partially shaded I know it can drag the string down. Would a point ever be reached where its better to have 8 unshaded at all times as opposed to 1 partially shaded in the later part of the day.?

Thinking about it I suppose its hard to answer as the output of the single panel may boost the overall gain during early to middday production, and cost in the later day. If we assume max from the single panel to boost then say 6hrs x 270 = 1620.
If this panel then dropped the whole string ( but I dont know by how much it would, so ill go for 3/4s) for the last 2 hours.
9 x 270 panels = 2.43 kwh x 2 = 4860/4 = 1215.

So by my maths the partial shading would be better to have than the lower panel number, especially as max output would not be seen in the latter part of the day anyway.

Problem is I dont know if a 3/4 drop is what shading would cause, could it be much more?

pinnks

While shading is an important consideration, I wouldn't have thought 400W was unreasonable about an hour before sunset on a south-facing array of 2.4kWp I have 1.75kWp facing just eat of south but get shading on one panel from about 2pm at this time of year which quickly brings production down to a couple of hundred watts. By 1640 I am pretty much at zero - darn chimney...

tunnel

Believe me, shading is an issue. Before I retro fitted my SSW with solaredge I could watch the power drop from 1.6kWh down to 200W within 5 minutes once the first panel had shading of around 15-20%.


Its one of the main reasons I ask anyone looking for advice on solar if they have any shading at all, I've seen first hand the effects of it.

theboylard

Tunnel's on the money there, just had SolarEdge retro fitted at the end of January.

Today my panel that causes me most shading problems put out 650 Wh, the next one 960 Wh, but then I have 14 panels with 1140 Wh each, +/- 35 Wh.

Shading is a killer, multiply potential losses over 20 years... It's scary!

pinnks

I agree shading is a big issue. Out of interest what is the process and approx. cost per system/ panel or whatever of going Solaredge?

rosythfifer

It would be nice to be able to disconnect the panel and see if anything changes. Another consideration is the factI have only had the panels since jan (was due to be installed december before fit drop but every weekend was high winds, so lost 20 years of a little extra). So sun has been low. Summer and any shading may go, so giving a better gain.

theboylard

You can fit standalone solar edge optimizers, they don't need the full inverter change that I did.
Basically just a box for each affected panel, so you'll need to consider how many you need plus the cost of installing them.

The IndOp optimizers from or favourite shop are £32 each plus the dreaded. Then it's the cost of access to the panels, which can vary wildly based on method! Ladder (seen it done with my own eyes), access tower or proper scaffold.

Martyn1981

pinnks wrote: »

I agree shading is a big issue. Out of interest what is the process and approx. cost per system/ panel or whatever of going Solaredge?

Hiya.

During the install it's not too bad, it adds about £30 to £40 per panel for each PO (power optimiser), but the inverters are a little cheaper (around the cost of the cheaper Chinese units) as they are more 'dumb', and have very high efficiencies and long life expectancies - 12 yr warranty from the start.

So SE probably adds about £300 - £500 to an install.

But ..... for retro-fit it's pretty expensive. You'd have to have the scaffolding up again, pay the labour for each panel to be removed and have the PO fitted (this is quick and easy, but still ....). You'll also need to buy a SE inverter and sell the old one on fleabay.

SE do produce kit now that can work with regular inverters, but you'll still need to buy a monitoring add-on thingy for a couple of hundred, so maybe best to get their inverter.

PO's, labour, scaffolding, inverter - retro-fit probably £2k?

[theboylard beat me to it!]

Mart.

pinnks

Thanks. Good to know it can be retrofitted without a new inverter if need be.


I doubt SE is needed on my larger WSW-facing system as the shadow of the chimney is pretty much gone by the time panels get into direct sunlight but on the smaller SSE-facing system it's that chimney which casts its shadow on the first panel anything between 14:00 and 16:00 depending on the time of year. Yesterday it was 14:00 and almost instantly knocked 90% (1 - 1.2 kW I should think) off the production. In the summer it is not until 16:00 but then sunset is later too. My guess is that could have amounted to about 3kWh yesterday.


If you assume you might suffer something similar for say 180 days a year, then you get about 550kWh per year at my rate for that system of just over 16p including export tariff. So, something around £100 per year, or in today's terms, about £2,400 over the remaining FiT period.


I have 7 panels feeding into an SMA 1600TL on a 45 degree roof, so scaffolding rather than tower probably required/sensible. With labour therefore unlikely to come in below £1,000 to £1,500 I guess. Looks like the economics is not working in my favour.


What is slightly annoying is that shading was at the forefront of my thinking when seeking quotes and one firm was a fan of SE but not from my shading perspective, just a fan... The consensus view of all quotes was that there would be little benefit overall from going SE or micro inverters given the extra cost and fault risk on the roof etc, so I ended up not going for SE and using the firm recommended by a friend, whose price was good and workmanship known. Don't get me wrong, I would still recommend them but would now have a different conversation with them...


Oh for the benefit of hindsight and finding this particular forum, which has a lot more practical advice and expertise through experience than the places I landed when doing my initial research.

rosythfifer

Well I have confirmed shading today. Probably just under a third on one panel and a very slight amount on another. Solar plummets about 1730.
I guess its something I will have to live with really as I think the cost of fitting anything would outweigh the benefit.