This routine implements the DISC correlation function, which is not included by itself as an option in PlantPredict; however, it is used by both the DIRINT decomposition and Hay transposition models.

Inputs

Outputs

 

Algorithm

1.) Compute the clear-sky normal transmittance for all solar zenith angles.

2.) Compute coefficients a, b and c for the beam transmittance equation.

1. 1. If K_t ≤ 0.60

1. 1. If K_t > 0.60

3.) Compute the direct normal transmittance.

4.) Compute the DIRINT direct normal irradiance.

5.) Set G_b,n,DISC to 0 if θ_Z > 87°, G_T < 1, or G_b,n,DISC < 0

 

Reference

Maxwell, E. L., A Quasi-Physical Model for Converting Hourly Global Horizontal to Direct Normal Insolation.

Technical Report No. SERI/TR-215-3087, Golden, CO: Solar Energy Research Institute, 1987.