Hi @ahad ,
You will have to be specific about what criteria your analysis needs to meet. Do you just need the incident clear-sky radiation or do you also need to account for bounces of radiation off surrounding context surfaces? Do you just need the total annual clear sky radiation or do you need it on an hour-by-hour basis?
Also, are you using the new LBT Grasshopper plugin that was released last week or do you need a solution that uses the Legacy plugin?