Renewables: "talking 'bout my generation"

John_Pierpoint

Near perfect curves on the graph.
Thursday = 19
Friday = 20
Saturday = 20
That might well be the last 20 this year.
An amazingly still day and presumably moisture gathering in the higher atmosphere - in the approaching sunset I counted more than a score of vapour trails in the sky and the other high cloud could well have been the remains of jet activity.
Normally vapour trails clear in about 15 - 20 minutes.

John.

3.6 "Aurora" inverter for panels on 30 degree SE roof.

Martyn1981

John_Pierpoint wrote: »

An amazingly still day and presumably moisture gathering in the higher atmosphere - in the approaching sunset I counted more than a score of vapour trails in the sky and the other high cloud could well have been the remains of jet activity.
Normally vapour trails clear in about 15 - 20 minutes.

John, semi-joking, but maybe aircraft activity could be added to PVGIS climate. I'm sure vapour trails have been linked to weather and temp differences on the ground in some areas, so bound to have a small but noticeable (?) effect on PV if you live in 'the wrong place'.

Average day yesterday, but still nice, and holding a few percent ahead of target. A novelty to be ahead here at the beginning of the month, since March.

Mart.

jkpaul

Following the recent discussions on here about PVGIS changes, I thought I'd reinvestigate to see whether our predictions had changed.

Our MCS certificate states Declared Net Capacity as 4kW and the Estimated Annual Generation as 3434 kWh.

Now although we do have a net capacity of 4kWp in the panels (16 x 250W), the inverter has a name of Fronius 3.6 TL which I believe refers to the net capacity. Presumably this is then a (marginally) limiting factor which means 3.6 should be the figure I enter into PVGIS, not 4.

For our location (WF8, West Yorkshire) I entered the following details:

Solar radiation database used: PVGIS-CMSAF
Fixed system: inclination=30°, orientation=15°
Building integrated

Nominal power of the PV system: 3.6 kW (crystalline silicon)
Estimated losses due to temperature: 11.4% (using local ambient temperature)
Estimated loss due to angular reflectance effects: 3.1%
Other losses (cables, inverter etc.): 14.0%
Combined PV system losses: 26.2%

Total annual electricity production - 3090 kWh


If I enter the same details but with 4kWp as the Installed peak PV power, I get the following:

Solar radiation database used: PVGIS-CMSAF
Fixed system: inclination=30°, orientation=15°
Building integrated

Nominal power of the PV system: 4 kW (crystalline silicon)
Estimated losses due to temperature: 11.4% (using local ambient temperature)
Estimated loss due to angular reflectance effects: 3.1%
Other losses (cables, inverter etc.): 14.0%
Combined PV system losses: 26.2%

Total annual electricity production - 3430 kWh

With 10 weeks to go to the end of our first year, we've reached 3161 kWh - 92% of the higher PVGIS Climate figures (3430kWh), based upon a 4kWp system.

If the lower figure is right, 3090 for a 3.6kWp system, then we've beaten it by 2% with 72 days to go.

Incidentally with the Classic PVGIS figures, the expected generation is 260-290 kWh lower for the 2 sets of data.

Either way, I'm happy :beer: but it would be good to know which figures I should be watching [=celebrating shooting past again] next year - can anyone put me out of my misery?

don0301

22.7 kWh for me yesterday

129.4 kWh for last 6 days :j

My understanding is you put in the panel size not the inverter size to the estimater

Bizarrely for me, my estimate for Climate PVGIS has reduced from 4030 last Jan, to 3850 now

My spreadsheet is estimating 4045.7 for the full year at the moment

I understand panels lose (sustained in sunlight) about 10% of their peak power through heating up, that's why most people have undersized inverters in this country

I also read somewhere that in the UK you will only get peak generation for 3% (timewise) in the year, so it's more efficient to have a slightly smaller inverter that's more efficient overall

I'm sure someone will come along and contradict me

don0301

http://www.bbc.co.uk/news/world-europe-19508906

Apparently, the effect will be wetter and more unsettled summers for the UK

Another reason I'm chuffed I've got such a steep roof

Martyn1981

jkpaul wrote: »

Following the recent discussions on here about PVGIS changes, I thought I'd reinvestigate to see whether our predictions had changed.

Our MCS certificate states Declared Net Capacity as 4kW and the Estimated Annual Generation as 3434 kWh.

Now although we do have a net capacity of 4kWp in the panels (16 x 250W), the inverter has a name of Fronius 3.6 TL which I believe refers to the net capacity. Presumably this is then a (marginally) limiting factor which means 3.6 should be the figure I enter into PVGIS, not 4.

Either way, I'm happy :beer: but it would be good to know which figures I should be watching [=celebrating shooting past again] next year - can anyone put me out of my misery?

No idea if there is an 'official rule', but I agree with Don, and would describe your system as 4kWp, since that's what you can catch, even if your inverter can't process it all, so you could increase the default losses bit if you wanted. But ......

Loads of pluses first:

Looking at the specs for that inverter, it's actual output limit is 3,680W (not 3,600), so that's a plus. Also it states 16A limit, which at the UK max of 253V could be over 4kW, but I suspect it is a genuine 3.68kW limit.

Next you have to include inverter efficiency ratings (Euro rating) which pulls it down, but since that is a high efficiency inverter at 97.2% = 3,888W, it would still suggest a small loss, but we're getting closer.

Next, how many people have systems peaking for very long. Given that most panels lose approx 0.4% for each 1C rise in temp, strong sun usually means peaks only last a few seconds to a minute or so, so 90% sustained peaks are more realistic, which for yourself would be approx 3,600W from the panels. Though cold weather peaks (ask Don) can be impressive.

Lastly, for countries like the UK where 'less than perfect' weather is the norm, having a slightly undersized inverter (circa 10%) may, and I stress may, generate more per annum, due to higher efficiencies at lower levels, like a small car engine driven gently.

Apologies for the boring lecture, but your system, in my opinion, ticks all the right boxes, and may be close to perfect. So slap in a 4 and chase the target with a smile on your face. :T

Oh, lastly, this was pointed out to me some time back, that I wrongly recommend using 'building integrated' not 'free standing' on PVGIS in the FAQ thread. I am wrong, but use the 'innacuracy' to help ensure that generation isn't overestimated by those considering PV - possibly better to be happy with the investment, and maybe get a little more if the set up is ideal with no shading.

Mart.

KevinG

Martyn1981 wrote: »

Oh, lastly, this was pointed out to me some time back, that I wrongly recommend using 'building integrated' not 'free standing' on PVGIS in the FAQ thread. I am wrong, but use the 'innacuracy' to help ensure that generation isn't overestimated by those considering PV - possibly better to be happy with the investment, and maybe get a little more if the set up is ideal with no shading.

Hi Mart,

Can you explain a little more, I must have missed the original conversation. Are you saying we should be using free standing rather than building integrated for normal domestic PV panels installed on the roof?

Martyn1981

KevinG wrote: »

Hi Mart,

Can you explain a little more, I must have missed the original conversation. Are you saying we should be using free standing rather than building integrated for normal domestic PV panels installed on the roof?

Hiya Kev, basically yes, but just keep it between ourselves! The difference between the 2 is about 4% to 5%, with the cooler 'free standing' outperforming the slightly warmer 'building integrated' which sit in the roof replacing the slates/tiles.

But, 5% can easily be lost in the roundings, and inverters vary from around 91% efficient (my SB1200) to 97%+ (my SE2200), so, in my defence I'd always use, and recommend, the building integrated. Also, that's a best situation whereas many folk may underestimate a small amount of shade, maybe a particularly tricky aerial or soil pipe.

Also panels do have performance tolerances, though many these days seem to only have zero to plus tolerances, not so many -/+ tolerances.

Of course it's not for me to interfere, but I'd hate for someone to buy PV after overestimating income. And anyone put off by that small a difference, maybe needs to just take some more time before deciding.

Well that's my excuse, and I'm sticking to it!

Mart.

Edit: PS Kev, I think you may have inadvertently offended Doc N on the 'So now I have ...' thread when you removed your mispost. Damned if you do, damned if you don't! The fun of short sentences. M.

KevinG

Martyn1981 wrote: »

Edit: PS Kev, I think you may have inadvertently offended Doc N on the 'So now I have ...' thread when you removed your mispost. Damned if you do, damned if you don't! The fun of short sentences. M.

So I did. I have probably now made matters worse on the other thread!

shafeeq

Hi

*Lowest of the month 7.33 KwH


* sorry that is wrong, it wasn't lowest of month,2nd sept was lowest