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Understanding PV energy production variations


Marvin

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Energy production is as variable as the weather. 🙄 But how much does it change the results in a month or year?

 

Based on calculations using the PGIS data over 10 years I thought I would share the results.  In one calendar year the energy produced can vary from the average by +/- 5%.  In one calendar month the energy produced can vary quite widely!  From +24% to -28% from the average!

 

 

Here's my summarised results:

 

                        Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yearly
hi/mid percentage 12.73% 24.94% 20.62% 12.17% 17.89% 9.83% 10.29% 10.72% 15.01% 21.15% 17.98% 10.59% 4.18%
Mid/ low percentage -15.0% -20.7% -20.6% -12.7% -13.9% -13.0% -8.6% -13.6% -12.9% -20.1% -28.8% -17.6% -4.4%

 

Worth considering when relying on PV results.

 

 

4 Comments


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Is the month tested included in the period mean it is tested against.

This is really a problem with using a statistical mean as it includes the extremes.

It is why the median is often used.

 

When looking at sunlight data, it is usual to create two sets of data, one that includes the night, and the other that excludes it.

 

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Hi @SteamyTea This is not sunlight data, only PV energy production based on my set up over the years 2011 to 2020 using PGIS data. Figures are kWhs

 

  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
2011 179 241 600 800 856 773 780 690 569 420 248 180 6,337
2012 221 286 612 689 775 702 812 647 585 310 258 185 6,083
2013 182 269 426 695 764 801 920 782 522 393 251 182 6,187
2014 222 353 647 679 795 886 931 744 573 382 228 188 6,627
2015 237 274 546 787 710 843 777 624 662 401 174 155 6,190
2016 207 312 538 707 826 706 805 785 528 460 272 190 6,337
2017 236 264 474 736 795 852 771 727 501 372 267 171 6,167
2018 191 380 431 635 883 879 927 685 611 470 289 147 6,528
2019 235 379 514 731 862 807 911 800 582 327 225 197 6,570
2020 195 286 576 816 971 821 806 737 620 341 235 184 6,588

 

For someone who has no PV you take a great interest...

                           
                           
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1 minute ago, Marvin said:

or someone who has no PV you take a great interest...

What I did my BSc Dissertation in.

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Inteeresting data - I suppose the size of the variations will depend on where you are in the UK and how changeable the weather/cloud cover is in your area. (coming from the Chilterns to West Yorkshire, weather  is like being on a different planet)

 

Here's a calculator for those interested in seeing what they can expect to generate depending on where they are on the planet

 

https://pvwatts.nrel.gov/

 

and enter your postcode and size and tilt etc..

 

 

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