Different solar data for the same case


#1

Hi, I downloaded solar PV data for year 2014 for a place with specific parameters almost 3 months ago, but now it gives different results for the same case. Even the temperature data are different. Can you please tell me how it is possible?
To clarify the case, I used interface two times to download data for Helsinki, Merra with Capacity 12000 (kW), year 2014, loss (10%), tracking none, tilt 35, azimuth 180. All direct, diffuse and temperature are different from 3 months ago data.


#2

Thanks for raising this issue. I would expect a small discrepancy (~0.1%) in PV electricity generation and irradiance due to us pulling in a fix to the PV model addressing negative irradiance values at low sun angles. However, this should not affect temperature, and I am unable to replicate any additional discrepancies in my tests.

Assuming that you have output CSV files and the exact parameters you used in both cases, can you send us that data to [email protected] so that we can investigate further?


#3

Thank you for your reply. I sent them in excel file.


#4

Great. We will investigate and get back to you.


#5

As indicated by email, we can confirm that the API is operating normally and that apart from a possible mix-up of result files, the discrepancy is only being caused by the update to GSEE to fix negative irradiance values occurring during low sun angles. A comparison of a sample day at the specific site (Helsinki) in this case, showing the minor change in results during morning and evening hours:

Do let us know if you run into any other issues!