Solar now seems much less efficient

Rheumatoid

defaultdriver wrote: »

Mine was topping out at 3.1kW against the usual 3.2kW
I have not seen my system go over 3.2kW, is your 3.7kW a short burst or for a long period of time
I had one day in May in which I had 3.2kW for just over 3 hours.
I was expecting the same today but it was slowly moving upwards during the day till it topped out at 3.2kW 2.15 till 2.45 from which point it slowly started heading down again

I have regularly been having 3.7 for long periods during sunny cold days between October and May. Last couple of days have got nowhere near though (3.2 max) hence me wondering if something was wrong but it seems I am not alone. There has been some haze and my panels are a bit dusty but think the main factor is probably reduced efficiency with temperature. What are the symptoms of having a panel down or could any other malfunction cause a sudden drop in output like this?

EricMears

I thought I'd try and see what happens if you actually try to cool panels.

Afraid it wasn't a rigorous scientific experiment but certainly better than any theorising.

I used a pressure washer to spray water onto the lower set of my panels. (the upper & lower sets are measured separately with a dual string inverter). There was a little overspray onto the upper set but not very much.

After a couple of minutes of this I checked the individual string outputs and found only 20W difference between the two (total output was 2.4kW at the time).

No obvious effect on the graphical output (of both sets combined) - if anything the total output fell a little but it was at a time when it should have been dropping anyway.

Ten minutes later, the difference between sets had dropped to 2W


Have just repeated the experiment. This time I abandoned the pressure washer and climbed up almost level with panels holding a conventional spray on the end of my hose. This of course delivered a lot more water albeit at lower pressure and I was better able to ensure that only the lower set were wetted. Result here was that there was a difference of 40W between panels (total had dropped to 2.3kW). There was a very small 'kick' in the total output trace of perhaps 100W - but I've been haing similar sized peaks & troughs all day so doubt that one was significant.


Not really part of the same experiment but because the hose was set out and sitting on the roof I went up a bit higher to clean all the panels off a bit (they did seem a bit mucky). On the way up I tried feeling the panels to get an idea of the surface temperature (nothing as fancy as a thermometer ) - all were warm to the touch but not particularly hot and no significant difference between the ones I'd tried to cool and those I'd avoided. There was a spike of around 300W in the total output graph at what might have been the crucial time but OTOH there was another spike of 200W a few minutes later.


Conclusions ? None really - I ought to have noticed some improvements but really didn't. My spikes might have been from correcting a 10% loss but I'm not convinced that's true. Absolutely no chance that my output had dropped 25% over last few days - if it had happened (whether due to temperature or dirt or both) my actions should have shown some improvement..

Rheumatoid

EricMears wrote: »

I thought I'd try and see what happens if you actually try to cool panels.

Afraid it wasn't a rigorous scientific experiment but certainly better than any theorising.

I used a pressure washer to spray water onto the lower set of my panels. (the upper & lower sets are measured separately with a dual string inverter). There was a little overspray onto the upper set but not very much.

After a couple of minutes of this I checked the individual string outputs and found only 20W difference between the two (total output was 2.4kW at the time).

No obvious effect on the graphical output (of both sets combined) - if anything the total output fell a little but it was at a time when it should have been dropping anyway.

Ten minutes later, the difference between sets had dropped to 2W


Have just repeated the experiment. This time I abandoned the pressure washer and climbed up almost level with panels holding a conventional spray on the end of my hose. This of course delivered a lot more water albeit at lower pressure and I was better able to ensure that only the lower set were wetted. Result here was that there was a difference of 40W between panels (total had dropped to 2.3kW). There was a very small 'kick' in the total output trace of perhaps 100W - but I've been haing similar sized peaks & troughs all day so doubt that one was significant.

:T:T:beer:

Beyond the call of duty. Presume they also got washed and that didn't alter much? Maybe it is just haze / atmospherics messing with the path of the sun?

EricMears

Rheumatoid wrote: »

:T:T:beer:

Beyond the call of duty. Presume they also got washed and that didn't alter much? Maybe it is just haze / atmospherics messing with the path of the sun?

You gave up too soon - should have waited for conclusions (even though it's really lack of conclusion ). But thanks for the beer :drool:

I'm pretty well convinced that true cloud-free skies are pretty rare at this time of year; there's nearly always some sort of high level haze or even dust around.

My wandering around on roof is less brave than most people would assume - the bit of roof I was walking on is a bit steeper than the panels but still well below a 30deg slope.

michaels

organum wrote: »

I have been checking my previous year's logs and find that I am wrong and that the daily output is the same as last year!

Sorry to put folks to a wild goose chase.

However my concern is that the 4kW system is only giving out 2.1kW with both sets of E/W panels being fully illuminated by brilliant sunshine. This has clearly been the same as when the unit was installed and I cannot find the original estimates.

I understand that E/W systems are not as good as fully S but nevertheless?

Any pearls of wisdom on this chaps/chapesses ;-)

TVM

Our panels are only just S of W and I was looking at adding soem E panels and PVGIS seemed to suggest that I could almost get away with keeping just the 1 4kw inverter because there wasn't that much overlap in output.

I didn't get the extra panels in the end cos TP (Paul Page) who did the first install decided to take my deposit and disappear which explained why they were slow to send me the promised deposit guarantee certificate At least the total cost including the lost deposit was still cheaper than any other quotes I had on the first install.

Oneday77

I was getting troubled by my output until I read a comment on here last week, in the talk about generation thread.
Last month my 3.99kW system was maxing out at 3.96kW, which I am more than willing to take as it's max. This month and the tail end off may it was only giving 3.60kW max and I knew it was better and longer days.


I have a Solaredge system and micro-inverters with my 14 x 285W panels. Checking the app, none of my panels were down. I though maybe the dry days had dusted over the panels, my car was minging after all. So I hosed down the roof. No good sun for about 3 days afterwards, so I didn't really see any benefit.


Then last week we had strong sun again, immediately after a day of rain. So ruled out dust. I am now firmly on the, the heat is causing a 10% efficiency reduction on my panels. Though I can't complain I've had a 31.86kW day and several 28-31kW days.


My generation plots from the app are pretty smooth, so again no cloud cover has been creeping about. Which for the Aberdeen Area can be very rare


I should add, I saw a 3.96kW spike one day this week, but it was 11degrees outside.
We hate the cold, we hate the warm, what do we actually like

Rheumatoid

Oneday77 wrote: »

I was getting troubled by my output until I read a comment on here last week, in the talk about generation thread.
Last month my 3.99kW system was maxing out at 3.96kW, which I am more than willing to take as it's max. This month and the tail end off may it was only giving 3.60kW max and I knew it was better and longer days.


I have a Solaredge system and micro-inverters with my 14 x 285W panels. Checking the app, none of my panels were down. I though maybe the dry days had dusted over the panels, my car was minging after all. So I hosed down the roof. No good sun for about 3 days afterwards, so I didn't really see any benefit.


Then last week we had strong sun again, immediately after a day of rain. So ruled out dust. I am now firmly on the, the heat is causing a 10% efficiency reduction on my panels. Though I can't complain I've had a 31.86kW day and several 28-31kW days.


My generation plots from the app are pretty smooth, so again no cloud cover has been creeping about. Which for the Aberdeen Area can be very rare


I should add, I saw a 3.96kW spike one day this week, but it was 11degrees outside.
We hate the cold, we hate the warm, what do we actually like

3.96 is good. I have never seen over 3.75. Presume its the solar edge system that makes the difference? Not that I have any idea what that is

Martyn1981

Oneday77 wrote: »

Though I can't complain I've had a 31.86kW day and several 28-31kW days.

7.98kWh/kWp :shocked: ....... PV !!!!!!!

(Am I allowed to say that?)

Mart.

Rheumatoid

Back to 3.7kW on occasions today . Whatever caused the drop is not here today even though its a fairly cloudy day with only the odd bit of sun breaking through. Might have been atmospherics or dirt as we have had some torrential rain over the last couple of days.

ASavvyBuyer

We had a peak of 3.927 kW yesterday, just after a torrential downpour of hailstones. The highest peak recorded since the system was installed. Maybe the hailstones gave the panels a good clean or it was the cooling effect ? Not too bad a day at 4.224 Os seeing it was cloudy & raining most of the day.