Renewables: "talking 'bout my generation"

EricMears

Oscargrouch wrote: »

Anyone else having a problem getting on the Metcheck site without just getting an advertising site instead?

Metcheck now seems to have sorted itself out.......

Metcheck is a very strange site ! It has in the past worked well for weeks at a time and produced some far more reliable forecasts than competitors. Particulary useful that they give actual numbers for %ge cloud cover and expected mms of rainfall and I've generally found those reasonably accurate.

However, for last few weeks I've found I can only access the site early in the morning or late at night. Attempts to refresh screen (or even zap it and load a fresh copy) in 'sensible hours' just produce a screen full of error messages. Reporting them to Metcheck gets an automated response but never any improvement.

For the last couple of days they've also been getting forecasts wrong - e.g. % cloud cover was vastly overestimated and the 10mms of rain they promised yesterday afternoon & overnight never happened at all. Today I see they're promising me 5mms of rain compared to BBC & Met Office sites suggesting nine hours of 'heavy rain'

18.9Kwh yesterday - Not brilliant but far more than any of the so-called weather forecasts had led me to expect.

pvgis forecast for May 456 Kwh. Actual 504 plus whatever we get today (next to nothing if weather forecasts correct so possibly another 30 :rotfl:)

The_Green_Hornet

There are a number of independent weather stations located across the UK which may give you a more accurate forecast depending on where you live.

http://www.weatherstations.co.uk/aws_map.htm

davidanddeirdre

KevinG wrote: »

Yes, my 2kWp SSE facing system has never quite managed to exceed 13kWh. What's the rating of your inverter? I'm fairly sure mine is limiting the output as although it's rated for a maximum of 2kW of panels, its rated maximum output is 1575W and I have only occasionally seen higher than this.

We face slightly E of SE (little or no direct sun on roof after about 4.00pm at this time of year), with a 1.75kW system, 10 X Sharp panels at around 40deg inclination and Sunny Boy SB1700 inverter. The highest continuous output I have seen with sun directly facing and a cloudless sky is just over 1500W, but it can be 10% less. It took me quite a while of comparing totals for cloudless or nearly cloudless days and considering other weather factors to realise that output is significantly raised when there is a cooling breeze, especially from the SE. So our biggest day ever (so far) since the March 3 2011 start was May 26th this year at 12.17units. The maximum shade temperature that day was around 23C, but there was a fairly stiff breeze from the SE all day. Presumably this prevented the panels heating to any significant degree.
Apart from the possibility of mismatched inverter, a factor which can depress total output considerably is partial shading. The first week of operation we had scaffolding still up, & the handrails made a tremendous difference to sunny day output as we found when removed. So any poles, cabling, chimney stacks, trees or snow on the panels etc which give any shade whatever are bad news.

KevinG

So that's another month down and I actually managed to beat PVGIS by 7.2%, half of the total being in the last 10 days of the month.

sly_dog_jonah

A grey day today to finish the month but surprised to say we just made it into double figures.

May figures are as follows:

Generation: 443.4kWh
PVGIS estimate: 390kWh
Performance vs PVGIS: +14%
Normalised generation: 120 kWh/kWp
Record Day: 24.4kWh (26th)

We generated over 20kWh on 8 days, but didn't make it into double figures on 10 days. Average generation was 14.3kWh (3.9kWh/kWp).

Since installation late October we're running 21% ahead of PVGIS.

Martyn1981

System: 3.58kWp

Slope 27°, 110° (South -70°), Lat: 50.5

Total generation: 443kWh

Target PVGIS Climate: 395kWh

Daily average: 14.29kWh

Generation per kWp: 123.74kWh

Daily average per kWp: 3.99kWh

Mart.

Edit: SDJ - You beat me by 0.4 Grumble, grumble, grumble!

EricMears

None of my weather forecasts were really accurate. Pretty cloudy most of day but very little rain. Certainly not the 9hrs of heavy rain and I don't think we even got the 5mm.

My (joking) forecast of 30Kwh on the day was of course wrong. Actually 6.02 Kwh. Not a huge amount but twice what I need to break even with ISA rates.

pvgis estimate for May : 456 Kwh
Act generation for May : 509.8 - or 11.8% better than pvgis
Since 1st Sept, system has been 16.7% better than pvgis

GaryMo_2

PVGIS estimate for May - 470kWh
Actual generation for May - 567kWh / 120% of PVGIS estimate
Generation per kWp - 141.75kWh (based on 4kWp panels)*
Generation per kWp - 154.08kWh (based on 3.68kW cap of inverter)*
Low - 4.52kWh
High - 28.73kWh
Average - 18.294kWh

Pretty happy with that considering the poor start to May.

*Should I based generation/kWp on the rating of my panels (4kWp) or the rating of my inverter (3.68kW)?

jimjames

GaryMo wrote: »

*Should I based generation/kWp on the rating of my panels (4kWp) or the rating of my inverter (3.68kW)?

I'd say base it on the panels. In most situations you won't be achieving the output near the panel total so the inverter won't be limiting the generation. You can see the difference from the peak and panel potential in this graph.

http://uk-solarpanels.blogspot.co.uk/2012/05/solar-panels-low-peak-output.html

The panels total 3kWp, the inverter is 3kW yet on a sunny day the maximum peak output is only 2.3kW due to the drop from the temperature.

I'm surprised how well we have done this month. Despite the poor start we still got 365kWh compared to the PV-GIS estimate of 347kWh and the SAP2009 figure of 334kWh.

Oscargrouch

whoops, cannot compete with the statistics of the other
Anoraks’ here but here goes:-
5.6 today
Total for May 324
Average for this Month 10.61 :rotfl: