Far horizon and albedo
Far horizon
Distant mountains or buildings block the Sun at sunrise and sunset. The horizon is defined as a list of azimuth, elevation pairs (in degrees; 0 = north, 90 = east, 180 = south, 270 = west). When the Sun is below that profile, the direct radiation is set to zero.
Two ways to define it:
- Get the horizon from PVGIS: downloads the profile calculated by the European Commission from a digital terrain model. You can edit it afterwards.
- Type it by hand, one pair per line:
90, 8
180, 15
270, 5
If the horizon is clear, leave it empty.
No double counting
With a horizon defined in Radiaris, the PVGIS data are downloaded without their own horizon, so that terrain shading is not counted twice.
Nearby objects (chimneys, trees, neighbours) are defined in the roof editor: see Objects and shading model.
Albedo
Albedo is the fraction of the radiation reflected by the ground or roof surrounding the modules. It adds reflected radiation to tilted planes and is the basis of the rear-side gain in bifacial modules.
You choose the surface type or type the value (between 0 and 1). Priority: explicit value > surface type > 0.20 by default.
| Surface | Albedo |
|---|---|
| Default value | 0,20 |
| Grass / lawn | 0,25 |
| Bare earth / dry soil | 0,17 |
| Gravel / aggregate | 0,20 |
| Concrete | 0,30 |
| Asphalt | 0,10 |
| Clay tiles (roof) | 0,20 |
| Metal sheet (roof) | 0,30 |
| White membrane (flat roof) | 0,65 |
| Fresh snow | 0,80 |
| Water | 0,07 |
The values are indicative and come from the usual literature (NREL, Duffie and Beckman, PVsyst). If you know the real albedo, type it.