Solar radiation terms#
Direct Normal Irradiance (DNI)#
The direct or beam irradiance is the irradiance that directly from the sun, i.e., unscattered. DNI is measured with a pyrheliometer, which typically has a 5 degree opening and is mounted on a solar tracker to always point at the sun.
Global horizontal irradiance (GHI)#
The global horizontal irradiance is the total hemispherical irradiance received on a horizontal plane. GHI is measured with a pyranometer with a 180 degree view to the sky.