GHI, DHI to DNI

Dear All,

Im using SAM for calculating the long term yield of a PV plant here in Chile.

We only have long term satellite data for GHI and DHI (diffuse horizontal).

I know there is a mathematical relashionship between GHI,DHI and beam (DNI. Is it possible to calculate DNI from these two straight forward? What about low elevation angles, since there might be a division by zero.

Do you have a recomended method in order to get DNI from the other two and use SAM?

Best Regards.

Sebastian.

Dear Sebastian,
There are a couple of discussions on this topic that might help:

• 
  Is it possible to estimate GHI or DHI from only DNI
• 
  DISC model occasionally throws odd DNI

Best regards,

Paul.
 

Dear Paul,

I've forgot to mention that I was looking at the DISC model as an alternative for estimating DNI. Nevertheless this way I'm leaving the DHI data out, and doing an assesment just based on GHI.

I would like to have some insight from more experienced engineers if its better to do this and use only GHI or estimate DNI through mathematical formulas.

Bests