How is solar power defined?

[dguest]

Obviously W/m^2 is a standard unit of flux, but flux is usually defined as the flow of energy through a surface with a specific orientation. Is the surface defined to be normal to the sun? Or normal to the ground?

[idefix37]

@dguest
You will find the answer in this related topic :
https://community.windy.com/topic/30978/any-place-to-find-cumulative-radiation-forecast-not-irradiation?_=1709327479252
… It is said that the parameter is “the solar radiation that reaches a horizontal plane at the surface of the Earth”.
So it is not normal to the sun.