Global Horizontal Radiation

also called Global Horizontal Irradiance; totalsolar radiation; the sum ofDirect Normal Irradiance (DNI),Diffuse Horizontal Irradiance (DHI), andground-reflected radiation;however, because ground reflected radiation is usually insignificant compared to directand diffuse, for all practical purposes global radiation is said to be the sum of directand diffuse radiation only:

&#160 &#160 &#160 GHI = DHI + DNI * cos (Z)

&#160 where

&#160 &#160 &#160 Z is the solarzenith angle.

Click Shining On (Figure 3) to see solar components