Changed irradiance with update

[jamesbm]

HI,

 

I have noticed that 2 projects run using the same postcode with "create climate data for new location" have given very different irradiance values.

 

The 995kWh/m2 value was produced on Friday with R5, the 876kWh/m2 was run today since the R6 update. Everything else is the same, as you can see it is the same Latitude and Longitude. PVGIS gives a value of 1030kWh/m2 so I am hoping it ends up being the higher of the 2 numbers.

 

I have recently noticed values going up when rerunning projects after previous updates without any changes.

 

Such large changes obviusly make a big difference to project economics, it is hard to be confident in the outputs.

 

Are you able to explain what has changed since the update?

 

Thanks

 

James

[developer_mh]

Hi James,

I tried to reproduce the change of the irradiation values, but here I also get around 875 kWh/m² in a fresh install of PV*SOL premium 2018 R5. So I suppose that the climate file might perhaps date back to PV*SOL premium 2018 R4, which was before we updated MeteoNorm to version 7.2. MeteoNorm is the climate data provider we use in MeteoSyn. When I create a new climate file with a fresh install of PV*SOL premium 2018 R4, I also get around 950 kWh/m².

In MeteoNorm 7.2 there are a couple of changes that also affect global irradiation sums. If we have a look at the map with the differences of the global irradiation in the region where Scunthorpe is located, we can see that there is an area of negative deviation of around -50 to -100 kWh/m²:

http://www.meteonorm.com/images/uploads/demo_uploads/diff_ghi_v72_vs_v715_europe.png

On their website you'll also find the changelog that lists the changes of the data and the models they use:

http://www.meteonorm.com/en/support/changelog

I hope that helps and re-establishes the confidence in our product If you have further questions, please don't hesitate to ask.

Kind regards,

Martin

[jamesbm]

Martin,

Thanks for such a comprehensive reply.

It isn't great for us for ongoing projects but I obviously understand the need to use the latest information. I'm still not sure how it could be so much lower that the PVGIS number but I guess Meteonorm know what they are doing.

All the best

James