Horizon shading calculation

[Jean]

Hello,

In the hourly output, we can see that when sun elevation lies between horizon elevation +-5°, beam horizon shade can be strictly smaller than beam incoming even when the sun is under the horizon, and also strictly positive even when the sun is over the horizon. Does anyone know the formula used for that, and why it is not as simple as "sun under horizon implies no beam light, sun over horizon implies no beam horizon shade" ? Is this formula used in the integral calculation for diffuse horizon shade ?

Thank you,

Jean

[André Mermoud]

The beam is an average irradiance over for the whole hour.

Therfore PVsyst calculates the duration for which the sun is below the horizon line, and the duration over. The beam component is accounted for the duration above the horizon.