Calculating the yield of solar panels

I was inspired by a tweet from Karin van der Wiel where she plotted the yield of her solar system to a theoretical value.(*) I wanted to see if I could replicate it with the yield of solarpanels of a friend.

I took the daily weather data of the KNMI from their site(*) and used the yield of the solar panels of a friend.

If you only use “global radiation” then there is a deviation. This is due the fact that the yield lowers when solar panels heat up.

Thus I calculated the theoretical value as described in this article. I had to take care that some values in the weather report are in tenths, so I had to divide them by 10.

I didn’t take daylength in account as described in formula 1 of the article of van der Wiel, since the KNMI value of global radiation is already per day.

The result of the exercise:

Now we take the averages per day, calculated for each month

Discussion

Assumed in the formula is that the solar panels are on a flat surface. This is not the case

The windspeed should be the value on 10m heigth, unknown which value KNMI gives

Links

Interactive version: https://rcsmit-streamlit-scripts-menu-streamlit-fiaxhp.streamlitapp.com/?choice=10

Source code: https://github.com/rcsmit/streamlit_scripts/blob/main/zonnepanelen.py

K.van der Wiel et al. Meteorological conditions leading to extreme low variable renewable energy production and extreme high energy shortfall, Renewable and Sustainable Energy Reviews. 2019 (111), Pages 261–275