In brief
Glare occurs only if the sun reaches the module surface and the path from the surface to the observation point is clear. Obstacles, the horizon line of far-field shading and, if enabled, the terrain are checked. Occluded reflections are flagged, not deleted; the filters in the report decide whether they count.
A hit alone does not mean glare. Glare only occurs if two paths are clear:
- Sun → PV area: Does direct sunlight reach the area? If it is shaded, no directed reflection arises.
- PV area → observation point: Does the reflection reach the observer, or is something in between?
Both paths are checked with spatial resolution: if a row of trees blocks only part of the area, only the reflection of that part is lost. The check removes nothing from the stored data; it sets the attributes "shaded" and "blocked" per cell, which are evaluated by the filters "PV area shaded" and "Reflection blocked by obstacle" (Ch. V.8).
| Occlusion | Path | Basis | Chapter |
|---|---|---|---|
| Obstacles | sun → PV area and PV area → observation point | polylines entered in the editor | Ch. 10.1 |
| Far-field shading | sun → PV area | horizon line per PV area from PVGIS | Ch. 10.2 |
| Terrain occlusion | sun → PV area and PV area → observation point | horizons at sampling points above each PV area and near horizon per observation point from the terrain model in the project | Ch. 6 |
V.4.1 Obstacles
Each obstacle produces vertical walls between consecutive points. An above-ground obstacle extends at each point from GL to GL plus height above ground and occludes only this height band; rays above and below remain clear. An obstacle of the type topography (deprecated, only in older projects; Ch. 10.5) has GL as its top edge and is closed downwards. Which occlusion acts on which path is summarised in Ch. 10.
- Sun → PV area: For each hit cell, a ray from the centroid of its calculation points towards the sun is intersected with all walls. If it pierces the height band of a wall at the intersection, the cell counts as shaded in this time step.
- PV area → observation point: For each observation point, a silhouette of the obstacles is precomputed in azimuth steps of 0.05°; for each step, the top and bottom edge of each wall and its horizontal distance are stored. A calculation point is blocked if a wall covers its elevation in its direction and is closer to the observation point than the point. An obstacle behind the PV area does not block.
V.4.2 Far-field shading
For each PV area, a horizon line from PVGIS (Joint Research Centre of the European Commission) can be activated in the editor menu "Far-field shading (horizon)", retrieved at the centre of the area's corner points. It describes the height of the surrounding terrain in 48 directions (7.5° steps); values in between are interpolated linearly. If the solar elevation in the sun's direction is on or below the horizon line, the whole area counts as shaded in this time step.
The horizon line acts only on the path sun → PV area; it does not block lines of sight to the observation point. Data basis, resolution and limits are described in Ch. 10.2.
V.4.3 Terrain occlusion
If the switch "Terrain occlusion" in the "Terrain occlusion" menu is on (without an explicit choice: as soon as a terrain model is activated), the terrain model in the project acts on both paths: it blocks reflections on the path PV area → observation point and shades the PV areas on the path sun → PV area. At simulation start, the horizons for this are calculated and stored in the simulation request; the result thus remains reproducible even if models change later.
The near horizon contains for each direction not only the highest terrain angle but the steps along the ray with their distances, for example a near low crest and a distant high slope. A calculation point is blocked if a terrain step that is closer than the point reaches its elevation angle. Terrain behind the PV area does not block. The steps are merged with the obstacle silhouette; in the report, terrain occlusion therefore appears under the filter "Reflection blocked by obstacle".
Sun → PV area. For each PV area, the highest terrain angle per direction up to 2 km away is calculated at sampling points above the area (corners, edges, a 25 m grid inside; coarser for large installations, at most about 600 sampling points per simulation), at the height of the module top edge. Each cell uses the nearest sampling point; if the sun is not higher than the terrain in its direction, the cell is shaded. A hill thus shades only the part of the area that lies behind it. In the report this appears under the filter "PV area shaded", together with obstacles and far-field shading. Simulations started before this extension calculate only the path to the observation point.
The terrain model contains neither buildings nor vegetation; these can only be taken into account as obstacles.
Deep dive: calculation of the near horizon
| Quantity | Value |
|---|---|
| Data basis | terrain models in the project (loaded from official sources or own file); the first source wins, later ones fill gaps |
| Calculation grid | 2 m, heights interpolated bilinearly |
| Azimuth step | 0.5°, three rays per step (at 1/6, 3/6 and 5/6 of the step width), the lowest counts; from eye height above the GL of the observation point, as in the simulation |
| Sampling along the ray | at the grid spacing |
| Earth curvature and refraction | taken into account, effective Earth radius 6,371 km × 1.13 (refraction coefficient 0.13) |
| Steps | each new height level of the running maximum in steps of 0.05° |
| Range | distance of the farthest PV corner × 1.05 + 20 m, at most 10 km |
| Cropping | only in the azimuth ranges of the PV areas (±3°) and from 1° below the lowest PV edge |
| Gaps | if a ray hits a gap in the model within the azimuth ranges of the PV areas and before the farthest PV corner, its azimuth step counts as incomplete; the report states per point the number of such steps out of those evaluated |
If the observation point lies outside the model, the horizon is calculated from its own height; the available terrain occludes, the missing directions count as incomplete. In an incomplete azimuth step, the existing terrain before and behind the gap blocks; only the gap itself does not. If the eye would lie below the model terrain, the simulation does not start. If the GL of the point deviates by more than 0.5 m from the model, the report states the deviation.