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Discussion Starter #1
While things are generally quiet on the forum, I thought I might take advantage of the experience of those here with solar panels?

For various reasons (trees, roof positions etc) I can’t fit solar panels on the south side of the house, and even the clearest spans of roof I have (facing due East and due West) are going to get some shade during the day from trees, an extension roof, etc. However, I do have a north facing flat roof about three garages in size (over a double garage and entrance porch).

During the summer, the sun Is high enough for most of it to be in full sunshine. In winter it’s mostly shaded. Today, at 2.30, it was like this:
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The shadow is from the gable end of the house, so parts of an array at the far end would have been in shade for two or three hours, but probably not all of it at any one time.

i had thought that the shade meant solar panels couldn’t work there, but having read what some of you say about not getting much energy anyway in winter months, I’m wondering whether they might. Any thoughts? I’ve got a Leaf 40, so a reasonable soak for excess generation in the summer. I’m retired, so around to turn things on and off, though mileage is now down to about 6000 a year, so I won’t be using ridiculous amounts. Not looking for massive savings, as I’m as interested in the ecological considerations as anything else, but am not going to get it past the domestic finance committee unless it makes some financial sense long-term.
 

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The cheapest form of install is with a single inverter. Because the panels are in a string if one of them is in shade the output of all of them is throttled down. But if you install the more expensive option of micro inverters (i.e. each panel has a small inverter) then only the panels in shade cut back their output. There is an added bonus with micro inverters in that you keep DC cables outside the house. AC has a much lower fire risk under fault conditions than DC.
East West can generate more per day than south facing, the peak is lower but the length of time regenerating a reasonable amount is longer. Ideal for trickle charging an EV.

Since about 25% of the total cost is for scaffolding, with an good installer who does not cut corners by not using it, then do consider putting out a higher peak capability system if you have sufficient space.
 

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I have micro inverters since my system is split South facing, East facing, West facing.

Enphase is really the brand/system to consider. Extremely reliable and easy to instal. No DC switching or wiring other than from the panel to the panel mounted microinverter.
 

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Discussion Starter #4
That’s very useful, thanks. Any thoughts about whether having the system in shade for say three winter months, and partial shade during the day for say another three months in late Autumn /early Spring is going to make a significant difference to how much I’d generate over a year?
 

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I have a small amount of shading on the South Panels which changes in a mid winter dat, panel by panel. The East an West panel output is of course very restricted in winter at 57 degrees North.

Best thing to do is to put your proposed system into a simulation calculator and that should provide you with a month by month panel by panel prediction.
 

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Micro inverters are not the best solution now... A better way is to use optimisers. An optimiser on each panel ensure that only that panel's output is affected by shade. You then have a single inverter but without an optimiser. This is by far the best way to install any residential system now IMO.

I recommend solarEdge inverter with solarEdge optimisers. They aren't the cheapest but they work really, the software is superb and their warranty and backup excellent.
 

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A description of your proposed system would help.

Lat/,long
For each bank of panels, azimuth, inclination, notional rated output, degree of shading by panel if localised.
 

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I've had enphase microinverters on my 4kW East facing 25 degree roof minimal shading for 4 years, have been excellent. But they maxed out at 3kW. East facing is great for early hot water, and my wife likes to put laundry and dishwasher on asap, so for us it fits better than identical output west facing would. East + West gives a lower output than South, but I'd argue you get a much better, flatter power curve that's more useable as it's better at start and end of day. South gives you fantastic output at noon, when you may not be able to use it all.
2 years ago I added a South facing 1kW triplet on garden shed, no Fit on that bit, and with the microinverters it was a simple job. I have 2 enphase transmitters in the gge each sending info to enphase's server so I see a single chart. Output drops a lot when no sun on panel. If it's cloudy but bright today I'll get 1kW maybe, but 3 if sun's shining. I get 4000 kWh solar pa, 1500 goes into my 10 kWh EV, 1000 reduces house bill, and 1500 gets exported. So that's 6000 miles EV driving, rest is petrol.
Economically the Fit on 3kW is useful, and I save 1500 grid units via EV, also about £150 pa on reduced gas bill as I have Solic 200 diverter which is now just about doing all our hot water. Ancient and inefficient boiler will soon be turned off for 6 months.
 

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Discussion Starter #9
Freddym, that would assume I have got a whole lot further in this exercise than I have...

I suppose what I’m really asking, from those who don’t have more shading at different times of the year, is for a rough idea of your relative output in the three midwinter months to the three midsummer ones - half? Quarter? And if you can give me some idea of the comparison with the spring and autumn months, even better.
 

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The ratio of summer output to winter output (3 months for each) depends on your latitude, location ( some areas of the UK are much cloudier than others) and the orientation.

For me, the ratio would be about 10:1.
 

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The ratio of summer output to winter output (3 months for each) depends on your latitude, location ( some areas of the UK are much cloudier than others) and the orientation.

For me, the ratio would be about 10:1.
Ok, downloaded the Enphase Enlighten reports for 2019. For my system the summer/winter ratio was 7.3:1 and for autumn/spring the ratio was 5 5
 

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@Astolat We do solar quotes for free and would be happy to look at different options for you - they obviously include calculating what actual generation you would get in each case. Just fill in our form.

Or, if you're happy to, PM me your address and we can go through the rest of the process of calculating your generation here publicly which other forum members may find illuminating.
 
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