Solar PV advice

[Countrypaul]

You would normally expect a 2.58kWp array to produce upto 2.58kW. The temperature of the panels would have to be as specified in the panel documentation and the insolation usially 1kW/m2. If the weather is very cold then you might get slightly more, if very warm less - again the panel documentation should give you an idea of temperature degradation.

Getting 663W out of a 2.58kW array looks like it gives you the 25.7% figure you are seeing.

[Richard77]

You would normally expect a 2.58kWp array to produce upto 2.58kW. The temperature of the panels would have to be as specified in the panel documentation and the insolation usially 1kW/m2. If the weather is very cold then you might get slightly more, if very warm less - again the panel documentation should give you an idea of temperature degradation.

Getting 663W out of a 2.58kW array looks like it gives you the 25.7% figure you are seeing.

Thanks Countrypaul...

I was thinking (wrongly I suppose) that as the solar panels efficiency is around 23% I would only be able to generate 23% of the 2.58kw

So if everything is perfect I should be able to generate the full 2.58kw (never going to be perfect in NW England though!)?

[MrPablo]

You'd be surprised what the panels can push out. I've seen peaks of 5kW from a 4kW array, all depends on panel temps and things like cloud edge effect.

[Richard77]

You'd be surprised what the panels can push out. I've seen peaks of 5kW from a 4kW array, all depends on panel temps and things like cloud edge effect.

Cheers MrPablo...

I'm not expecting much from these...

Low pitch 12° ish
2x 645w on south (1.29kw)
2x 645w on north (1.29kw)

See how they go.

It did go over 1kw for a bit before...

[MikeNovack]

I never thought of max power f my solar array being of much interest. Max energy over the day, yes. And especially energy produced over the year, with consideration of energy by month. The siting of the panels, angle, alignment, and especially any parts of the day when might be shaded are going to affect that. Back when our site was evaluated (the roof of the barn-garagee) they had a little device known as a "sun eye" which got placed up at what would be the center of the panels which "pictured" that and did the calculation. I say "pictured" because you COULD edit the in=mage to remove a shadow factor so could evaluate "and if THAT tree were cut down".

[sharpener]

So if everything is perfect I should be able to generate the full 2.58kw (never going to be perfect in NW England though!)?

Tagging on, yes and so as a rough guide you could ordinarily expect 1000hrs hence 2.58 MWh per year in the S of England, perhaps a bit less where you are, for fine detail PVGIS and solcast are your friends.

[MikeNovack]

Tagging on, yes and so as a rough guide you could ordinarily expect 1000hrs hence 2.58 MWh per year in the S of England, perhaps a bit less where you are, for fine detail PVGIS and solcast are your friends.

That I do not understand al all. Is 1000 hours meant to be a rough average of "aligned and angled for full power"? For a fixed array? For a tracking array, no obstruction (in the open in flat area, no nearby trees or buildings) more like 4000 hours with that then needing adjustment for thicker atmosphere at low sun angles, morning, evening, winter, etc.

Generally trackers do not "pay" if enough space to install a larger fixed array, and especially if fixed just alignment but angle seasonally adjusted. Trackers are costly and needing frequent repairs (we know people who have them). The situation is similar to GSHP which are far more effective in my climate but costly (again, we know people who have).

With reference to general info like "PVGIS" I take it then that devices like a Solmetric SunEye 210 not being used? << that may be an obsolete model, but the only one I know maker/model info for >>

[Richard77]

I never thought of max power f my solar array being of much interest. Max energy over the day, yes. And especially energy produced over the year, with consideration of energy by month. The siting of the panels, angle, alignment, and especially any parts of the day when might be shaded are going to affect that. Back when our site was evaluated (the roof of the barn-garagee) they had a little device known as a "sun eye" which got placed up at what would be the center of the panels which "pictured" that and did the calculation. I say "pictured" because you COULD edit the in=mage to remove a shadow factor so could evaluate "and if THAT tree were cut down".

I'm a novice to all this so was just wondering if they were performing the way they should be and what would be a good generation target. I stupidly thought that as solar panels are around 20% efficiency that I would max only be able to generate 20% ish of the 2.58kw array. It is nice to know that I can theoretically generate the full 2.58kw and more if conditions are perfect.

The most I have managed to hit today is a few spells of around 1.2kw it's been quite sunny and cold (that's good I think!), but with it being March I wasn't expecting much.

When I used pvgis in the past it gave me an estimate of around 2000kWh annually I think, but the majority of that would be generated later on in the year during the summer months.

That sun eye seems useful... Do get a bit of shading from neighbours trees later in the day. There should be 4 tigo optimisers installed on each of the 4 panels so should help.

Shame I can't see if they are working through the SunSynk software or anything. Maybe there is other software that give more detailed info?

[Richard77]

Noticed there are quite a few smudges dirty fingermarks all around the outside of the panels from yesterday's install.

I suspect they won't be helping the generation?

[sharpener]

That I do not understand al all. Is 1000 hours meant to be a rough average of "aligned and angled for full power"? For a fixed array? For a tracking array, no obstruction (in the open in flat area, no nearby trees or buildings) more like 4000 hours with that then needing adjustment for thicker atmosphere at low sun angles, morning, evening, winter, etc.

Yes and no. 1000hours is about the full-power-equivalent running time for an array in S England, a bit more in the extreme SW.

As per my sig below the older array has an installed capacity of 3.68 kW on a roof which is fortuitously facing due S and nearly the optimal angle, and I get just under 4 MWh per year from it which has varied very little year on year since Dec 2011.

PVGIS enables you to predict generation by site/orientation/pitch, I don't know the underlying theory exactly but I think it is based on geometry not measurement. Solcast makes short term predictions based on weather forecast, Victron use it in their adaptive ESS algorithm but ATM I have got it turned off.