Daily pv production
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Well you can expect another 42kWh tomorrow with your array (roughly) if the forecasts are right.
Me? I got a solid 32.6kWh on the main roof and another 13.8kWh off the shed, bringing me to ~46kWh in total. Solid figures. But still I've a fair bit to go for all time high for me, which is mid-50's (east/west split still getting better for another few weeks)
Sunday looks solid enough too, but monday is a return to …. meh
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I never see anyone monitoring the solar radiation which met eireann publish daily to give a good feel of the effect of cloudy/sunny days on panel efficiencies. I have a modest self installed solar (3.84M2) thermal which, based on the roches point solar radiation of 2761J/m2 gave a efficiency of 30.2%. solar radiation, 2761*0.0027777*3.84, 29.45Kwh, flat plate output, 8.9Kwh, efficiency, 8.9/29.45, 30.2%, on cloudy days, this can fall to 8% or less but both the yearly solar radiation and the panel output have remained remarkably consistent over the past 13 years at ~ 1000kwh/m2 (radiation) and panel(s) output of 260kwh/m2, to give a consistent overall efficiency of 26%.
Applying the above to your solar PV and assuming 6m2/KWp?, suggests you have 64.5m2 installed so solar radiation was 64.5*2761*0.0027777, 494.54KWh, output, 68.1KWh, efficiency, 68.1/494.54, 13.77%. The 72.6KWh "Mayo Man" above using 2651J/m2 (average of Belmullet&Claremorris) gives a efficiency of 14.67%.
It would be very interesting (to me anyhow) to monitor both the solar radiation and PV output over a few weeks to see how the fall off in output compares with the solar thermal on cloudy days, I suspect not as much.
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I monitor it and occasionally publish some analysis on the daily yields. Eg.
The problem with what your suggesting is that it's not as trivial as it would seem on the surface. Yes, Met Eireann publish solar forecasts, and I take those numbers and apply a weighted algorithm to it based on historic yields to give estimates as to what I'll generate in the future. I don't "need" the estimates, but it's a fun project.
What's important to realize though is that the Met Eireann solar radiation forecasts are in fact forecasts. They are generally ok, but there are days where whatever reason, they are well off. Comparing one days numbers with another is tricky and prone to pitfalls. They say your due to get 6,000 "rads" (lets call them :-) , but did you actually get 6,000 rads? Who knows? I know the page you linked is "actuals" , but even with them…there are problems.
Some examples -
- A solar irradiance of (say) 6,000 on a day where it's 21c is a lot different to 6,000 on a day where it's 10c outside. Your panels will operate better when it's cold even though the watts/sqm is the same.
- Then there's the time of day problem. I have a E/W split (2.2Kwp East and 4.4Kwp west). Let's say it's generally a cloudy day, but there is 3 hrs of bright sunshine in it. If I get 3 hrs of bright sunshine before noon, or 3 hrs in the afternoon, I'll get (substantially) two different yields, even though the total irradiation for the day is generally the same with it sunny in the morning verses afternoon. Basically the bright spell in the afternoon will hit my bigger arrary so bigger yield.
So comparing as your suggesting is ….. complicated. You can do it, but you need temperature coefficients, map the yield to the hour and that back to the installation profile (E/W, South, etc) and size of arrays.
A year or two back we had a good thread on this in the forums - but I can't find it.
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