ForgeSolar Glint and Glare Methodology Explained

What Is ForgeSolar?

ForgeSolar is specialist software developed specifically for solar glare impact assessment. It is the most widely used tool for glint and glare modelling in Ireland and the UK, and its methodology is accepted by An Bord Pleanála, all 31 Irish county councils, and the Irish Aviation Authority.

ForgeSolar models the reflection of sunlight from solar PV panel surfaces and predicts when and where reflected glare may be experienced at specified receptor locations. It accounts for sun path, panel geometry, array layout, and receptor positions to determine glare occurrence on a time-of-day and time-of-year basis.

How ForgeSolar Works

Inputs

ForgeSolar requires the following site-specific inputs:

**Panel geometry**: tilt angle, azimuth orientation, panel dimensions, and height above ground

**Array layout**: the position and extent of each panel row in the array

**Site coordinates**: latitude and longitude for accurate sun-path calculation

**Receptor positions**: the precise locations and heights of all identified receptors (dwellings, roads, aviation, etc.)

Modelling Process

ForgeSolar calculates the path of reflected sunlight from each panel surface using sun-path algorithms for the specific site latitude and longitude. For each receptor, it determines:

Whether reflected light from any panel in the array can physically reach that receptor

If so, when during the year and at what time of day reflected light would reach the receptor

The intensity of the glare (expressed as retinal irradiance or as a green/yellow classification)

The modelling is carried out under worst-case clear-sky conditions — that is, assuming maximum available sunlight without cloud attenuation. This is conservative: real-world glare will occur less frequently than the model predicts due to cloud cover.

Green and Yellow Glare Classification

ForgeSolar outputs glare results using a two-category classification system:

**Green Glare**: Low-intensity reflected light that is below the threshold for significant discomfort. Green glare results are generally acceptable to Irish planning authorities without mitigation.

**Yellow Glare**: Higher-intensity reflected light that exceeds the green glare threshold. Yellow glare at sensitive receptors (particularly road users and dwellings) requires consideration and potentially mitigation.

Important Note on Yellow Glare

Yellow glare does not automatically mean a problem. The assessment must consider:

**Duration**: How long per day and how many days per year the glare occurs. Brief, infrequent glare events are treated differently from prolonged daily occurrences.

**Receptor type**: Yellow glare at a public road is more significant than yellow glare at a distant field boundary.

**Context**: Anti-reflective panel coatings, panel orientation adjustments, or landscape screening may reduce yellow glare below the threshold.

What Happens When Yellow Glare Is Identified?

Where ForgeSolar identifies yellow glare at a sensitive receptor, the assessment report will include mitigation recommendations. Common mitigation measures include:

**Anti-reflective glass**: Panels with anti-reflective coatings reduce surface reflectance from approximately 8% (standard glass) to below 4%, which can eliminate or significantly reduce yellow glare results.

**Panel tilt adjustment**: Reducing or increasing tilt angle changes the angles at which reflected light is directed and can eliminate glare at specific receptors.

**Panel azimuth adjustment**: Rotating panels slightly from due south can redirect reflected light away from sensitive receptors.

**Landscape screening**: Hedgerow or tree planting between the array and receptor can screen reflected light at ground-level receptors.

Aviation Glare Assessment

For sites near airports, aerodromes, or ILS (Instrument Landing System) approach paths, ForgeSolar includes aviation-specific receptor analysis. The Irish Aviation Authority (IAA) has published guidance on acceptable glare levels for aviation receptors, and our assessments are prepared in accordance with this guidance.

Aviation glare is assessed at air traffic control tower viewpoints and along approach corridors. The assessment considers whether glare would occur during aircraft approach and departure — the most critical phases of flight.

Glare Pre-Simulation

Before finalising a solar farm layout, we offer a glare pre-simulation service that tests different panel configurations to identify which design minimises glare risk. This is particularly valuable for sites near roads or dwellings where yellow glare is likely if the standard layout is used.

See: [Solar Glare Pre-Simulation](/solar-glare-pre-simulation) | [Glint and Glare Assessment Ireland](/glint-and-glare-assessment-ireland)

Get a ForgeSolar Assessment

[Contact us](/contact) with your site layout drawings and panel specification for a fixed-fee glint and glare assessment. We deliver within 2–4 weeks of receiving complete site information.

Related Services

Glint & Glare Assessment Glint & Glare Report Ireland Solar Glare Pre-Simulation

Frequently Asked Questions

What is ForgeSolar and why is it used in Ireland?+

ForgeSolar is specialist ray-tracing software for solar glare assessment. It is the accepted standard tool for glint and glare modelling by An Bord Pleanála, all 31 Irish county councils, and the Irish Aviation Authority.

What does "green glare" mean in a ForgeSolar report?+

In ForgeSolar output, green indicates glare that is below the threshold of concern — equivalent to or less intense than blue sky. Yellow or red indicates glare that may require mitigation or further consideration.

Do I need ForgeSolar for a rooftop solar application?+

ForgeSolar is primarily used for ground-mounted solar farm applications. Small rooftop solar installations on commercial buildings may not require full ForgeSolar modelling, depending on the planning authority's requirements.

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