Karthik R
Administrator
Hello You should be able to specify the Sun Direction Vector of the sun.
Regarding the definitions of Direct and Diffuse Irradiations, please take a look at the following link.
https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v211/en/flu_ug/flu_ug_Radiation_Model.html?q=solar%20radiation
I hope this helps.
Karthik