May I ask whether the coefficients (sky clearance and brightness) of the Perez model would be adjusted when I chose a different location (weather profile)? 

Or only the sun hour and other climatic profiles would change if I chose a different location. 

Thanks.

Views: 27

Reply to This

Replies to This Discussion

Hi Ivan,

We call the gendaylit program to handle all of this. The link describes all of the assumptions in the model parameterization reasonably well.

Best,

Alstan

Thanks Alstan, 

I have tried to read the document you mentioned. However, I cannot find the part that explains whether the coefficients are adjusted according to the location. It only stated that the data are from radiometric measurement centres. 

Ivan

Hi Ivan,

I think the relevant part is here:

The  atmospheric  conditions  are  modelled  with  the  Perez  et  al.  parametrization  (see  Solar  Energy  Vol.  44, No 5, pp. 271-289, 1990), which is dependent on the values for the direct-normal and the diffuse-horizontalirradiances. The three parameters are epsilon, delta and the solar zenith angle. "Epsilon variations express the  transition  from  a  totally  overcast  sky (epsilon=1)  to  a  low turbidity clear  sky (epsilon>6);  delta  varia-tions reflect the opacity/thickness of the clouds". Delta can vary from 0.05 representing a dark sky to 0.5 for a very bright sky.

Best,

Alstan

Reply to Discussion

RSS

© 2017   Created by jeff niemasz.   Powered by

Badges  |  Report an Issue  |  Terms of Service