Erbs Model

This routine estimates the direct normal and diffuse horizontal irradiance using the Erbs correlation.

Inputs

 

Outputs

Erbs Outputs

Algorithm

1.) Find the piece-wise correlation of the diffuse fraction fd :

    1. If 0 ≤ Kt ≤ 0.22:

Erbs Algo18

    1. 2.If 0.22 < Kt ≤ 0.80:

    1. If 0.80 < Kt:

Erbs Algo20
2.) Compute the diffuse irradiance:

Erbs Algo21
3.) Compute the direct normal irradiance only if GT > GD, as follows and if θz < 89°:

Erbs Algo22

Reference

Erbs, et al, Estimation of the diffuse radiation fraction for hourly, daily and monthly-average global radiation. Solar Energy, 28:293-302, 1982.