Glint & Glare: Aviation and Solar PV

Glint and Glare - this article explores the growing intersection of solar energy development and aviation safety in the UK.

It outlines why glint and glare pose a risk to pilots and air traffic operations, details the regulatory and planning frameworks that govern such risks, explains when and why assessments are needed, and describes effective mitigation strategies to ensure solar PV projects are both sustainable and air-safe.

Introduction: What is Glint & Glare and Why It Matters for Aviation?

As the UK rapidly transitions toward renewable energy, solar photovoltaic (PV) farms have become a familiar part of both rural and urban landscapes. While they contribute significantly to reducing carbon emissions, solar panels also introduce a potential hazard in the form of glint and glare—optical phenomena that can affect nearby sensitive receptors, particularly aviation infrastructure.

Glint is the brief, specular reflection of sunlight from a surface, typically occurring for a few seconds as the angle of reflection shifts with the sun’s movement.

Glare, on the other hand, is a more sustained, intense reflection that can cause discomfort or visual impairment. In aviation, both can disrupt flight operations, especially during critical phases like take-off, landing, or helicopter manoeuvres.

In the UK, safeguarding aviation from glint and glare has become an essential component of the planning and development process for solar energy projects.

Understanding the Risk to Aviation

Why Aviation is Vulnerable to Glint & Glare

Airports, airfields, heliports, and military installations are particularly sensitive to visual disruptions. Reflected sunlight from solar panels can:

Cause temporary visual impairment for pilots.

Disrupt the operation of air traffic control towers.

Affect the visibility of runway approach lighting systems.

Interfere with flight simulator or training operations.

These risks are most acute during low-altitude flight segments such as approach and departure, when pilots must maintain precise visual awareness.

Regulatory Framework for Glint & Glare in UK Aviation Planning

1. Civil Aviation Authority (CAA)

The CAA provides overarching guidance on safeguarding UK aerodromes. Although it does not currently publish specific national regulations on glint and glare, it mandates that planning authorities consult with aviation stakeholders, particularly when development occurs within the safeguarded zones of licensed aerodromes.

2. Ministry of Defence (MOD) Safeguarding

Solar farms proposed near MOD airfields or radar installations must undergo MOD safeguarding assessment. Glint and glare can compromise visual navigation or radar signals, and proposals affecting MOD operations are likely to be objected to unless satisfactorily mitigated.

3. National Planning Policy Framework (NPPF)

While the NPPF encourages the deployment of renewable energy, it also stipulates that developments must avoid unacceptable adverse impacts on the natural and built environment, including aviation safety. Paragraph 180 of the NPPF supports the prevention of visual impacts that could endanger air operations.

4. BRE Guidance: BR209 and Solar Dazzle

Though BR209 primarily focuses on daylight and sunlight in the context of planning and amenity, it acknowledges solar dazzle—a cousin of glare—as a consideration in developments with reflective materials. While not prescriptive for aviation, BR209 reinforces the need to assess reflected sunlight impacts where applicable.

When is a Glint & Glare Assessment Required?

A Glint & Glare Assessment is typically requested as part of a planning application for:

Solar PV farms (ground-mounted arrays).

Rooftop solar installations near airfields.

Glazed or reflective buildings in proximity to flight paths.

UK local planning authorities often require these assessments where developments fall within safeguarded zones of civilian or military aerodromes. These zones include:

Aerodrome height and obstacle limitation surfaces.

Runway protection zones.

Air traffic control (ATC) visibility cones.

Even where not explicitly required, many applicants commission a glint and glare study proactively to pre-empt objections from stakeholders such as:

CAA

NATS (National Air Traffic Services)

MOD

Local airport operators

Scope of a Glint & Glare Assessment

A robust Glint & Glare Assessment typically includes:

1. Solar Position Modelling: Annual and diurnal sun paths to determine potential reflection windows.

2. Receptor Mapping: Identification of all sensitive aviation receptors (e.g., runways, control towers, helicopter flight paths).

3. Geometric Visibility Analysis: Determining whether reflected rays intersect pilot sightlines or air traffic control zones.

4. Intensity Estimation: Assessing whether reflections exceed daylight luminance levels likely to cause discomfort or disability glare.

5. Duration and Timing: Identifying when and how long glint or glare would be experienced during operational periods.

6. Cumulative Impact: Where applicable, assessing multiple solar PV developments in the same airspace.

Mitigation Strategies for Glint & Glare Impact

Where a risk is identified, mitigation strategies may include:

1. Panel Reorientation

Adjusting the azimuth and tilt angle of solar panels to reduce reflectivity towards critical flight paths.

2. Anti-Reflective Coatings

Most modern panels use low-reflectivity glass (≤5% reflectance). However, specifying enhanced anti-glare coatings can further reduce risk.

3. Vegetative Screening or Earth Berms

Installing physical barriers between the PV array and aviation receptor locations, though this is generally more effective for ground-based receptors than elevated towers or aircraft.

4. Operational Restrictions

Limiting panel tracking or output during specific times when glint or glare risk is high.

5. Alternative Layouts

Reconfiguring the site design to remove or shift arrays that fall within critical visibility zones.

The Role of Local Planning Authorities

Planning officers rely heavily on expert glint and glare reports to determine whether a solar proposal is acceptable. Where an aviation stakeholder raises a safeguarding objection, planning permission may be refused unless the applicant demonstrates:

No unacceptable impact on aviation operations.

That mitigation measures will be effective and enforceable.

That relevant consultees (e.g. MOD, airport operators) are satisfied.

Case Study: Helicopter Approach Path Assessment

In a recent case study, we used our advanced analysis techniques to assess 360-degree approach path vectors for helicopters across a solar PV farm on behalf of airfield stakeholders.

By collaborating with airfield operators, we identified additional landing zones for the developer to review, ensuring safer aviation operations.

And in context we can understand the pilot eye view of a solar PV array and likely mitigating factors.

Expert Analysis from Anstey Horne

Anstey Horne offers independent, evidence-based assessments to help solar developers and airfield stakeholders navigate this complex intersection of renewable energy planning and aviation safety.

Our services include:

Glint & Glare Assessments for planning applications.

Aviation safeguarding zone analysis.

Stakeholder engagement with MOD and aerodrome authorities.

Custom 3D modelling and sunlight simulation.

Strategic site advice to avoid future objections.

Conclusion: Balancing Renewable Energy with Aviation Safety

The UK’s commitment to solar energy must be balanced with the imperative to maintain aviation safety. Glint and glare pose a real, albeit manageable, risk to air traffic. Through careful assessment and thoughtful design, developers can ensure their schemes are compliant, defensible, and approvable.

For developers, planning consultants, or airfield operators seeking expert advice on managing glint and glare risks—Anstey Horne is here to help.

Contact

With offices in London, Birmingham, Manchester, Bristol & Plymouth we provide advice on Glint & Glare on existing and new solar PV all around the UK.

For more information on all aspects of this service see the collection of articles on our blog page.

For further advice on Glint & Glare assessment of solar PV or any other aspect of Daylight and Sunlight for planning, please call our Daylight & Sunlight Enquiry Line on 020 4534 3138.

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