dirty solar panels, warm weather, lower power output?

diystarter7

EricMears said:

diystarter7 said:

Sorry, but reading this just makes me cringe as I hate solar panels as they make the area look run down as do wind turbines, dirty or not.
I'm same with those tv dishes.

Re the sun pannels, watch out for the dead pigeons under them or roof leaks as it cost  lot more to get the roof seen to etc.

Yes and building houses rather than leaving road (or even field) empty probably offends you too.

I assume you do live in a cave somewhere ?

Intially I was not going to respond to that. However, me being a reasonable man and it was me that took this OT, my mistake and I apologise for that. I was merely stating my total dislike of these things.

I don't mind new houses etc as long as they are not those lego type estates where many of them ar HA rentals or part own and buy.

FYI, I hate caves, lol but I can't disagree that solar panels/wind turbines do contribute toward a greener earth but NIMBY,

Just being honest and I don't mean to offend.

I will leave you guys to it.

Martyn1981

Just to say, and I hope I have this right, the performance drop of PV panels is not related to the change in ambient temp, but to the panel temp. In direct sun I believe they can reach something like 70C, a bit like the difference between touching a white or black car that has sat in the sun.

When there is very little wind I assume (again, apologies if I have confused things here) that the panels will be warming up the air around them, and losing less and less heat, v's a windy day where the air moves more and can carry more heat away.

On a still sunny hot day I expect panels to drop to say 70% of rating, whereas on a cooler windy day, maybe 80-85%, and in April / October, when we can get very clear skies, but cold and windy days, then 100% is possible. A month ago my 2kWp system held above its rating for about two minutes, and hit 2.22kW, much to my surprise.

2nd_time_buyer

Good point Martyn regarding ambient temperature. That was me confusing things. I was thinking that if the other things were held constant (clear sky, time, wind speed), then the variable would be ambient temperature. But of course the panel temperature could vary more than the ambent temperature even if the other variables stayed there same.

I should stop now before I dig an even deeper confusion hole.

Mikeyboy01443

Martyn1981 said:

Just to say, and I hope I have this right, the performance drop of PV panels is not related to the change in ambient temp, but to the panel temp. In direct sun I believe they can reach something like 70C, a bit like the difference between touching a white or black car that has sat in the sun.

When there is very little wind I assume (again, apologies if I have confused things here) that the panels will be warming up the air around them, and losing less and less heat, v's a windy day where the air moves more and can carry more heat away.

On a still sunny hot day I expect panels to drop to say 70% of rating, whereas on a cooler windy day, maybe 80-85%, and in April / October, when we can get very clear skies, but cold and windy days, then 100% is possible. A month ago my 2kWp system held above its rating for about two minutes, and hit 2.22kW, much to my surprise.

Thanks martyn,

Just outside Cardiff myself so probably shared the same weather today
I was just interested to see if you guys were seeing a difference today vs a month ago...
Martyn if you can look back to the days / times i hit higher pv power correlate with yours

QrizB

I'm sure I replied to this thread mentioning "cloud edge effect" but I can't see it anywhere. Wonder where that went?

thevilla

Without feeding the troll.....

Our best day PV production was last June, 4 years after install and with no cleaning other than rain.  It was on a very sunny day but one with quite a lot of light fluffy clouds.  The reflected light from them seemed to tip the generation into world record (for my house) territory despite occasional shading.  Ah the memories.

Edit:  Posted before the end of the thread.  So cloud edge effect seems to explain it 

silverwhistle

Whilst you're all here and to save me a search, does anybody know what the last percentage increase was for FITs? My last payment was very good due to production but the next one will benefit from the the annual increase.

To be honest I'm not sure what my daily production is, except today a full tank of very hot water and charging the car from 80 to 100%. Exporting as well from 08.00 to 20.00 as a reminder we're at the solstice.

Mikeyboy01443

imagine if i peaked within the first few days of solar generation and it was all downhill from there... i will still be looking back at that day in years to come

QrizB

silverwhistle said:

Whilst you're all here and to save me a search, does anybody know what the last percentage increase was for FITs? My last payment was very good due to production but the next one will benefit from the the annual increase.

December's RPI, which was 7.5% IIRC.

Next year should also see a decent increase, since the Index is already up 6.1% since December (from 317.7 to 337.1) and there's still seven months to go!

Martyn1981

Mikeyboy01443 said:

Martyn1981 said:

Just to say, and I hope I have this right, the performance drop of PV panels is not related to the change in ambient temp, but to the panel temp. In direct sun I believe they can reach something like 70C, a bit like the difference between touching a white or black car that has sat in the sun.

When there is very little wind I assume (again, apologies if I have confused things here) that the panels will be warming up the air around them, and losing less and less heat, v's a windy day where the air moves more and can carry more heat away.

On a still sunny hot day I expect panels to drop to say 70% of rating, whereas on a cooler windy day, maybe 80-85%, and in April / October, when we can get very clear skies, but cold and windy days, then 100% is possible. A month ago my 2kWp system held above its rating for about two minutes, and hit 2.22kW, much to my surprise.

Thanks martyn,

Just outside Cardiff myself so probably shared the same weather today
I was just interested to see if you guys were seeing a difference today vs a month ago...
Martyn if you can look back to the days / times i hit higher pv power correlate with yours

Hiya, happy to help, let me know which days and I'll give you my gen. Looking back my highest gen for May (and the year) was the 27th May with 23kWh on the ESE and 11.6kWh on the WNW. The next day was also high with 21kWh on the 28th, but showing how weather makes a difference, the WNW was only 7.7.

Now I'm getting highs of 21 and 22 on the ESE but the days are longer, clearer, and hotter. The WNW is peaking at about 10 each day, and due to it's 'extreme' orientation, benefits greatly from longer days as the sun travels further and higher through the west and north west. Hitting a total of ~32kWh per day is really right up there with the best for me, with best ever days peaking at 34-35kWh since install.

I'm used to seeing gen (combined) at around 3.5-4.2kW sustained mid day on cooler summer days, but lately I'm seeing 2.5-3kW, but long and sustained. Noticeable because I can alter the Amp rate on the BEV when charging, and I'm only managing 10-12A max, which is noticeably low peak power, but as totals for energy go for a whole day, I'm pretty much hitting the best I can expect, day after day (14th to 17th June & 20th to 22nd June).


Boring drivel time, but for the UK, south facing, annual PV gen is about 1,000kWh / kWp. But the best you'll see Worldwide (ignoring any tracking systems) is probably 2,000kWh/kWp, with southern Spain, southern USA and Australia showing about 1,600-1,800kWh/kWp. The reason the UK isn't far worse (proportionately) v's much sunnier climes, is the impact of heat on PV generation efficiency.


Edit - Thought struck me, if you are looking back on the 27th May, then I posted this on the generation thread on the 28th:

Some years I don't get a Maiden as gen tops out at high 5's, but yesterday brought a totally unexpected 6.2 O's, possibly thanks to some cold winds.

Around that time it was noticeable to me when out walking the Doggo, that the local wind turbine was facing 'the wrong way', so the winds were coming from the NE, when usually in the Spring they come from the SW. So unusual circumstances, but no complaints from me.