Finding watts

[Takis]

Hello friends

in the summer time, i've doubled my solar panel array and now i have 1980w for my 24v system.

At the first time of setting the system up, the watts were 1680w which was great. (Clear sky, great sun angle).

I had the system turned off for about a month, and when i turned it back on, the max watts (also with clear sky/ perfect sun angle) were sometimes 1400 (barely 1480). I've tried to draw the maximum many days-times (different temperatures - any kind of ambient). Panels are clean, no external damages, no hot spots etc, and it's has been rained.
I know that the maximum you can get from your system is about 80%. But that would be ~1600. Now days with cloudy weather i get 500w and today with very cloudy weather i got 200w out of 2000.

In the attached photo i have draw my system and some weak (in my opinion) points A,B,C
IMG_20211014_185730.jpg

[Mike90250]

With hardly any sort of cloud cover, expect 10% or less of rated output. I have 5Kw of panels and in cloudy weather, I get 300w. That's why I have 2, diesel generators for winter use,

If your batteries are full, they will not draw power from panels in full sun.

[Takis]

With hardly any sort of cloud cover, expect 10% or less of rated output. I have 5Kw of panels and in cloudy weather, I get 300w. That's why I have 2, diesel generators for winter use,

If your batteries are full, they will not draw power from panels in full sun.

But what caused to get 1600w at the first days and a month later (also summer time) it was ~200w lower ? That's the hard to find out !
All tests had been done with full batteries and full load to the inverter 3000w

[J.P.M.]

Back to basics.
To a rough 1st approximation, the output of an array is roughly proportional to the irradiance it receives.

You do seem to know that the output of an array or a panel varies with many inputs, but maybe you don't know that one of those variations - which is annual - is caused by the annual apparent movement of the sun to the north and back south again (or south to north in the southern hemisphere) which is due to the earth's axis being tilted relative to the plane of its orbit around the sun ?

Without knowing any more than you've written/included so far, it reads to me like what you're seeing under clear skies is pretty normal seasonal variation due to that annual variation in solar incidence angles.

As for output under cloudy conditions, as Mike writes, that will vary from minute to minute, but when it's cloudy, it'll be close to zero at sunrise/sunset and maybe/often between maybe 5 % to 20% of full output around midday or more, depending on atmospheric conditions.

[SunEagle]

It is October and depending on if you live in the Northern hemisphere it is Fall and in the Southern it is Spring time. Based on what I understand most pv panels will not produce anything close to nameplate wattage during those times even at high Noon.

Unless you have made some changes to the wiring or parts of the panels are no longer producing due to component failure or shade I would say the lower output is normal.

[Mike90250]

Simply leaving the system turned off, would not reduce the output when powered back up. Unless there was a bad wire or connection. But testing has to be done in bright clear, haze free skys, any clouds and it's all over.

[bcroe]

But what caused to get 1600w at the first days and a month later (also summer time) it was ~200w lower ? That's the hard to find out !
All tests had been done with full batteries and full load to the inverter 3000w

That is the way of renewable energy, you take what you can get, when you can. If
the noon sun is lower than another month, it must pass through more dust. The smoke
from fires half a continent away has had a severe effect here.

With the panel cost now a small part of the total, I have compensated by more than
doubling the number of panels. The equipment has something to do under clouds,
and I have arranged panels (facing E and W) to maintain about the same peak as before,
but over a longer day. good luck, Bruce Roe

[Takis]

Today, finally since July, I have got 1550w with partial clouds. That's almost 80%.

i live in North hemisphere and now it's autumn.

Thank you all for your answers.

[Ampster]

Good to hear that the Watts found you.