Horizon Profile

Answer: A horizon profile records obstruction elevation against direction as seen from a defined location. Comparing it with solar position helps identify when direct sunlight is blocked. A production model must also account for diffuse light and its own assumptions. A single far-horizon profile cannot describe every nearby object’s different shadow across an array.

Read the angular coordinates correctly

Each point pairs an azimuth with an elevation angle above the observation point’s horizontal plane. Record the observation coordinates and height, direction reference, rotation convention, capture date and data source. A curve imported with the wrong azimuth convention can put the obstruction on the wrong side of the site.

Under a north-zero, clockwise convention, north is 0°, east 90°, south 180° and west 270°. Other software/file conventions differ. PVsyst’s current import documentation explicitly provides controls for rotation direction and the north reference. Check the imported curve against a known landmark before simulation. See azimuth.

Far horizon versus nearby shading

A distant ridge may be represented as approximately the same angular mask for the whole PV field. A nearby chimney, parapet or tree may cast a shadow on some modules while leaving others illuminated. These need a spatial treatment appropriate to the model, not merely one skyline captured at the center of the roof.

PVsyst’s far-shading documentation limits its horizon treatment to sufficiently distant objects acting globally on the field and directs nearby objects to its near-shading model. Its direct-beam visibility treatment differs from its assumptions for diffuse and ground-reflected contributions. Those are model-specific treatments, not a guarantee that blocking direct sunlight eliminates all incident irradiance.

The skyline is a geometry input. It does not by itself establish electrical mismatch, bypass-diode behavior or annual AC-energy loss. Use shading analysis for the broader modeling process and a sun-path diagram to interpret the solar positions.

A geometry example

Assume an obstruction top is 10 m above the observation point and 30 m away horizontally. Its elevation angle is:

arctan(10 ÷ 30) = 18.4°

If the sun is at the same azimuth and below that angular outline, an opaque obstruction blocks the direct line of sight under this simplified geometry. The angle does not establish how many winter hours are shaded or what percentage of annual energy is lost. Those require the site’s solar positions, obstruction width, weather and model.

Moving the observation point changes both the vertical difference and horizontal distance. A profile measured at ground level should not be copied to a rooftop without checking that geometry.

Capture, validate and use the profile

1. Choose representative points: identify which arrays can share a far-horizon approximation and which need separate spatial shading information.
2. Collect evidence: use suitable survey instruments, photographs or documented terrain/3D data. Follow a qualified safe-access plan; a phone compass or old imagery is not automatically survey-grade.
3. Check the source: record resolution, date, coordinate reference, observer height, omitted vegetation/buildings and angular sampling around significant changes.
4. Import and inspect: verify direction conventions, elevation units and recognizable features. Compare current site evidence with the digital skyline.
5. Review weather treatment: determine whether the weather source already reflects obstruction effects. PVsyst’s weather-horizon note explains why station and project horizons can differ and why monthly corrections require careful handling. Do not blindly apply a second generic loss or simply disable the site horizon.
6. Compare controlled runs: hold the weather, design and other losses constant when testing the horizon’s effect. Report the modeled energy boundary and assumptions.

For example, hypothetical otherwise-matched annual AC estimates of 12,000 kWh without the profile and 11,400 kWh with it differ by 600 kWh, or 5% of the unmasked estimate. This is a declared comparison, not a measured site result or universal loss rate. Verify that near and far shading have not represented the same obstruction twice.

Vegetation changes, construction and revised layouts can trigger an update. Designers should retain the profile and model revision; installers can document discrepancies; sales teams should explain the actual estimate’s limitations rather than promise a fixed accuracy or savings outcome.

Frequently asked questions

Is a horizon profile the same as a sun-path diagram?

No. The profile represents the angular skyline from an observation point. The sun-path diagram represents solar positions; comparing them helps interpret direct-beam visibility.

Can one profile represent an entire roof?

Only when that approximation is appropriate. Nearby objects and changes in observation point can create different shading across roof areas and modules.

Can a profile give annual energy loss directly?

No. Geometry must be combined with weather, irradiance treatment and system modeling. State the energy boundary when comparing simulation outputs.

Does satellite or terrain data remove the need for validation?

No. Check the data’s date, spatial resolution, omitted objects and coordinate/height basis against relevant current site evidence.