Model step
Far shading (horizon)
Irradiance blocked by the horizon
Inputs used: Horizon profile, Apply horizon shading, Fraction of albedo taken into account
What it is
Distant hills and buildings hide the sun in the early morning and late evening and hide part of the sky all day. This step applies the horizon profile: it removes the direct sunlight while the sun is behind the skyline and, under the crossing-fraction option, reduces the diffuse light by the share of the sky the skyline hides. The step does nothing without a horizon profile.
Options
- Crossing fraction + diffuse integrals: the beam is scaled by the fraction of the timestep the sun spends above the skyline
- Hourly beam gate: the beam kept or removed by the sun's position at the middle of the sunlit part of the timestep
- Do not model: a flat horizon
References
- Quaschning & Hanitsch 1998, Irradiance calculation on shaded surfaces, Solar Energy 62(5) 369–375
API
site.use_horizon = true | false, options.far_shading_model = crossing_fraction | hourly_gate