Question about shaded roof to pv owners

Solar Photovoltaic (PV)

Last Post by prjohn 3 years ago

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Andris

(@andris)

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Topic starter 23/02/2022 12:25 pm

I am thinking about Solar panels to help with carzy electricity prices. I have a South facing roof. As u can see in the picture I will have some shading on when the leaves grow back on two trees that are casting shdowes on my roof. This gets better as we go towards the summer as the sun gets up above them.

My question is: Is it true that new panels need day light to work not necessary sun? Do they still produce energy if sade is on them? I am think about 6-8kw system

16kw Samsung TDM ASHP. 8.4kw PV, power optimizers 20×420watt panels 6kw SolarEdge inverter.

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Majordennisbloodnok

(@majordennisbloodnok)

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Posts: 804

23/02/2022 1:16 pm

I'm only an owner, not an expert. However, I have a PV array that's rated at about 6.5kW, so should give you some context.

What I can say is that during February when the sun was fairly low in the sky, and with a useable time range of around 9am to 16:30, I have seen my array generate up to about 15kWh. That has needed pretty much constant sunshine and a really clear day. Days like that this year have been interspersed with days of complete cloud throughout, and the same timespan on those days has seen my array producing around 2-3kWh.

As you can see, I'm not answering specifically about shade. However, it's obvious from this that a solar panel will definitely generate electricity without bright direct sunlight, but that efficiency tails off rather dramatically. It looks in the photograph as if you have a second (smaller) South-facing roof that does get full sunlight, and I suspect a few panels on that would likely generate a similar amount in full sun to the larger roof covered in solar panels when in shade.

Naturally, the sun doesn't stay still, so I don't know if the shade from the trees is all day long or just for a certain number of hours. That will also influence your decision.

Hope that helps.

105 m2 bungalow in South East England
Mitsubishi Ecodan 8.5 kW air source heat pump
18 x 360W solar panels
1 x 6 kW GroWatt battery and SPH5000 inverter
1 x Myenergi Zappi
1 x VW ID3
Raised beds for home-grown veg and chickens for eggs

"Semper in excretia; sumus solum profundum variat"

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prjohn

(@prjohn)

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Posts: 125

23/02/2022 1:47 pm

Here is an image of energy production over the last month with a 4kw solar array. You can see the effect of shading from a tree on the bottom four panels. This has less of an effect in the summer but as the tree grows it will become a greater issue.