Daily pv production

irishchris

Only 2.8 kWh here today but cloud sat over sun all day and looks the same for the upcoming week. Probably spoiled prior to this as lots of 8-12kwh days the week before

ELCAT2009

https://www.boards.ie/discussion/comment/118338201#Comment_118338201

I was thinking the same thing! Galway here and 2nd worst day since install just over a month ago... grand total of 0.8kw for the day on 6.2kw system!

Jonathan

https://www.boards.ie/discussion/comment/118340736#Comment_118340736

https://www.boards.ie/discussion/comment/118339155#Comment_118339155

Yeah. Clouds never lifted here in Fingal. Not complaining though. December has been pretty decent so far, with 84kWh month to date. A pretty respectable 11.6kWh generated on 5th Dec.

bullit_dodger

https://www.boards.ie/discussion/comment/118341325#Comment_118341325

Another nice day here in South Dublin. 2.5Kwhr generated so far.

Trees across the road will kill me shortly, but happy to take what we can get. Your December stat so far is way ahead. Me = 33 Kwhr so far, but the expected forecast for my orientation/size for Dec in total is 53Kwhr, so it's looking on target to beat it a little. 53 units forecast at ~€0.20 each...... I'll take a tenner in my back burner :-)

THE ALM

awful dreary day here today, never got going

ELCAT2009

I thought yesterday was bad but today is officially worst day so far with only 0.3kw registered for entire day! On the plus I still made it to 4pm until battery hit 20% and required grid top up! I guess it's to be expected as we head towards shortest day of the year.

Screenshot_20211218-195257_SolisCloud.jpg

.

ECO_Mental

The last 10 days down here is Cork have been bad, this is what my 6.1 kWp system has only done. The weather hasn't been really bad just overcast all the time the sun has never come out.

Anyway there will be a stretch in the evenings after tomorrow......

bullit_dodger

https://www.boards.ie/discussion/comment/118350298#Comment_118350298

LOL - technically, to be pedantic :-) there's been a "grand stretch in the evening" since Dec 16th. No, Dec16th wasn't the shortest day, but rather the day which had the earliest sunset. So the evenings have actually been getting brighter since the 16th.....but the sunrises were still getting later and later. Since the morning change was greater than the evening change, Dec21 is still the shortest day. As an aside -the latest sunrise actually happens at around the 29th/30th

A good explanation, with a fair chunk of math is here. Equation of time - Wikipedia

In practical terms.... Sunrise and sunset times in Dublin (timeanddate.com)

Yeah, I didn't realize this too until a few years ago and it sort of surprised me that the darkest evening isn't Dec 21st like I've believed for 40+ years since I was a kid. Course for us solar panel users the 21st is still our day of least production, but it's an interesting quirk of how astronomy works.

Jonathan

https://www.boards.ie/discussion/comment/118350829#Comment_118350829

I wasn't going to be the one to point it out, so glad someone did. 😂

bullit_dodger

"Anyone, anyone" teacher from Ferris Bueller's Day Off - YouTube - LOL

Seriously though the whole "solar noon" thing is something to remember when looking at your daily pv production charts. It does move throughout the year, but if you look at the above, solar noon for me in Dublin is 12:23 today, and of course that would be later the more west you are by 4 mins per degree west you are from Dublin, or plug it into the website above.

So assuming due South facing array and the sun is shining that's the time that you will get max production, and of course when the hour goes forward in March, that would be 13:23. I don't think it's intuitive that at 13:30 or so that you could get "solar noon". It was only when I got the panels in that I started to think about that.

ELCAT2009

https://www.boards.ie/discussion/comment/118350298#Comment_118350298

Same here in Galway...lovely dry days but so dull and overcast with solar pv getting worse by the day...I got 0.1kw on 6.2kw system 😄🤣. I thought I wasn't going to register any up until about 3pm when it finally crept to 0.1! Looking forward to the spring and Summer

DrPhilG

Damn lol, 0.1 is bad!

bullit_dodger

It actually sounds kinda "wrong" even. No?

Smaller system me (5.3Kwp split due east/west). Not sure what your orientation is, but East/west splits are pretty bad this time of year due to the sun only being to the south and it was a cloudy day here in Dublin. Yet I managed a paltry 1.0Kwhr. Seems odd that I could be 10x times your generation?! Could it be that you simply don't register unless you go above a certain amount?

What was your profile for the day ? Here was mine.....

If you think about it logically it must be under-reporting it. If you did 40 watts (which is piss poor, being less than 1%) off a 6 kwp system for 6 hrs, you'd do 0.24Kwhr for the day. I'd say it's a reporting issue, or the fact that your panels may need a certain amount before they "activate".

DrPhilG

I've had as low as 0.3kWh, that was a record low I think.

irishchris

https://www.boards.ie/discussion/comment/118353560#Comment_118353560

Does sound a bit off alright as in Galway myself and day has been a shocker with fog early and then just heavy cloud all day but produced 0.95kwh with a similar sized system so something sounds not quite right

Jonathan

https://www.boards.ie/discussion/comment/118354053#Comment_118354053

0.2 kWh here again in Fingal. 🙄

bullit_dodger

Hmmm interesting. I'd guess it has to be either a reporting issue or your panels don't "activate" unless you get to a certain threshold. You should be beating me as your south facing Jonathan and similar sized to my own (~5Kwp). Hard to believe that it only registered 0.2Kwhr today in Dublin when I got 1.0Kwhr. Maybe I'm wrong and over reporting ? Something seems off anyway.

Just doing some quick math, lets call it 6 hrs of daylight, 0.2Kwhr would be an average of 35 watts per hour. Even on an overcast day like today you should pop above 200watts? (5%). Do you have the solar breakdown chart of PV power verses time for today?

ELCAT2009

Here's a couple of screenshot from the solis cloud and solis home app from today. It really was just so dull and overcast today with fog this morn. My system is split 50:50 on SE and SW roof.

Jonathan

https://www.boards.ie/discussion/comment/118354178#Comment_118354178

Solis Cloud acting the mess and my export job won't process, but in summary: System only started generating at 10:21, and stopped generating at 13:59. Average generation 60W, max generation 90W. 🙄

ELCAT2009

I had actually reached 0.1 just before 1pm...looking at rest of the graph I probably wasn't far off getting to 0.2kw

bullit_dodger

Thanks mate. Weird one. The stock answer anywhere you look on the web is that on cloudy days a solar panel will generate between 10-25% of it's max rated output. E.g. Do Solar Panels Work on A Cloudy Day? – Solar Website (diysolarshack.com)

So if you have ~5Kwp, you should be hitting 0.5Kw-1.25Kw on a cloudy day. Of course that's the sun shining directly on the panels, so this time of year you'd have to factor in the roof orientation of the panels, and of naturally defining how "thick is the cloud" is like "how long is a piece of string", but still your 90 watts "peak" is something like 1.8% of your max. Seems a bit too low to be right, esp since your actually south facing.

Couple of miles away from you with the same weather, I maxed out at 280 Watts and I've a east/west split so my panels are facing away from the sun at noon. Doesn't seem right that I could be generating 300% more than you. Sure you'll always have some deviation(30-40% maybe) but 300% is a lot.

I take it on a sunny day like Dec 5th or the 14th you got good production. (5kwhr+) ?

Jonathan

https://www.boards.ie/discussion/comment/118354538#Comment_118354538

Clouds were just low, thick today and never moved. My system generated 11.6kWh on 5th Dec. 9.6kWh on 14th Dec.

bullit_dodger

Yeah, your production on the sunny days seems fine and beats the crap out of my East/West orientation....as i would expect this time of year when the sun is just to the south .

My generation was Dec 5th=3.3 Kwhr and Dec 14th also 3.3 Kwhr

Basically I had the same weather today as you. I'm only over in Knocklyon. What's that? 10 miles as the crow flies? Overcast all day here too. Doesn't seem to be a good explanation as to why you would produce so little on a day like today. I wonder if it's a Solis thing that they aren't great at reporting low power. Irishchris mentioned he got 0.95Kwhr on a similar sized system and he even had fog this morning. (No fog here)

Jonathan

https://www.boards.ie/discussion/comment/118354602#Comment_118354602

What inverter do you have? Quite possibly is a Solis thing.

DrPhilG

I have a 6.2kwp with Solis inverter. Awful fog til lunchtime here. Ended up with 1.4kWh

bullit_dodger

My inverter is Givenergy.

With south facing panels and a similar sized system, you should be beating the crap out of me everyday this time of year. From from the sunny days, it's clear that you do at least on those days, but it's odd that you don't on the cloudy days. Would you have optimizers by chance? To help here's the daily production for me for the month....

From https://re.jrc.ec.europa.eu/pvg_tools/en/#PVP%20that's%20the%20calculator%20for%20Europe,

My forecasted generation for Dec would be 53Kwhr and I'm at 36Kwhr now (dec 20th) - so I'm generally on track to get pretty close or slightly above my expected generation. For November I got 99Kwhr (actual) out of 93Kwhr (forecasted).

Might be a useful exercise for you to plug in your details for Nov and see how well you compared to forecast. Why do I care? Well, I think you might be missing potentially 20-30 units/month as far as I can tell.

idc

North dublin with 4.65kWp SE/SW split (SW has shading in winter but on completely cloudy day like yesterday i don't think that makes any difference !!)

9:25 0.01kW --> max at 12:15/12:20 0.17kW --> 15:05 0.02kW with a total of 0.7kWh so similar to some of the recent posts

For comparison generation on Dec 5th=4.7 Kwhr and Dec 14th also 4.2 Kwhr

bullit_dodger

Yeah, for those people getting 0.1Kwhr or 0.2 Kwhr, that's not cloud that's doing that. Not sure why the production is so low but pretty sure it's not cloud. It could simply be a reporting issue with Solis cloud, or the inverter isn't great a measuring low wattage, or perhaps you are actually getting more units than it's saying your getting.

Another way to look at it, is if you take your daily production for the month like my chart above and then compare the daily max for the month with the daily min, your minimum production should (roughly) be in about 10-20% of the max. This should work for any month of the year.

For example in my case my max was 3.3Kwhr, and my min was 0.6Kwhr, so for me 18%. You can only compare within a week or two of each other as the sun is getting lower/higher as the date difference increases - but within a week it's fairly negligible. Yours on the other hand (~11.6Kwhr to 0.2Kwhr) is 1.7%

That daily min of 0.6Kwhr I had was during storm bara co-incidentally, so you can imagine the cloud cover :-)

Not sure what if anything you can do to improve/fix those low generation figures, but at least you know about it now.

Jonathan

https://www.boards.ie/discussion/comment/118355545#Comment_118355545

0.1kWh today. It is quite possible that the Solis MPPT isn't the most efficient at very low power levels, but I don't think there is anything wrong with the PV system itself.

The issue is the cloud. My solar thermal system (also south facing, 20° slope) only managed to raise the collector temperature from 7°C to 14°C. Not enough for the pump to kick in even once.

bullit_dodger

Agreed Jonathan - I don't think there's anything "broken" with your installation either, your excellent production on the sunny days sort of proves that. Although it does seem to be under reporting on days like today. For comparison purposes, I generated 1.7Kwhr only 10 miles away from you. Mostly cloudy all day. Worse in the morning and sort of somewhat cleared up afternoon. To give you a like-for-like I took a picture at 13:40 it was....

https://www.dropbox.com/s/fecms3rrdhamsws/2021-12-21%2013.40.38.jpg?dl=0

and then looking at the profile for the day, at 13:40 this was generating

~640 Watts at the time.

Do you have optimizers by any chance? Just wondering if the optimizers need a certain power before they become active. Sadly I don't know much/enough about them to speak knowledgably on them.

My 1.7Kwhr on a East/west split array shouldn't be 1700% (yikes!!) more effective that yours on a South facing array of similar'ish size today.

Interesting problem....