Aviation is a significant producer of greenhouse gas emissions, generating approximately 3.5% of total emissions in 2020, and has been steadily increasing over time [1]. As such, airports are seeking ways to make air travel greener. In a recent article we explored the opportunities to produce zero-emission aircraft, but another avenue airports are exploring, is supporting renewable energy generation developments on their aerodromes, such as installing solar panels. However, solar panels can cause solar reflections, often known as glint and glare. Solar reflections can impact pilots and cause safety concerns, and locating solar developments on airports can heighten this risk. In this article we will review a study examining methods to reduce the impact of on-airfield solar upon aircraft and facilitate more renewable energy generation.
The aim of the study was to establish whether altering the direction solar panels placed on an airfield can reduce predicted glare while maximising its energy generation potential.
Figure 1: Bright sunlight over the wing of an aircraft [3]
The Approach of the Study
The study [2], conducted by researchers at Seoul National University of Science and Technology, conducted simulations of glare produced by hypothetical solar panels placed alongside and between the runways at Incheon International Airport in South Korea. An approximate recreation has been mapped out and is shown in Figure 2 below, where the hypothetical solar panels are shown as blue areas:
Figure 2: Hypothetical Solar Development at Incheon International Airport (Image Copyright © 2024 Google)
Solar panels were arranged to maximise energy generation – which in the northern hemisphere entails facing panels to the south (an azimuth of 180°) – and the resulting glare was assessed using the Solar Glare Hazard Analysis Tool (SGHAT). SGHAT is a widely used tool in the industry for glare intensity calculations and is formally endorsed by the Federal Aviation Administration in the United States.
To measure the duration of reflections, “Solar Glare Time” – the total time during a year when glare of any intensity was predicted – was calculated. Simulations were then performed where the azimuth angle of the solar panels was moved away from 180°, changes in the glare duration and energy efficiency where then measured.
The Findings of the Study
When the solar panels were arranged with an azimuth of 180°, glare towards the flight paths of approaching aircraft was predicted. Changing the azimuth of the panels along the western runway from 180° to 225° eliminated the predicted glare while only reducing energy generation potential to 94% of what was produced at 180°. For the panels near the eastern runway, no glare was predicted under an azimuth of 157.5°, with only a 2% drop in energy generation.
These simulations represent the potential for simple layout changes (known as layout optimisation) to minimise or eliminate concerns from glint and glare while not compromising the efficiency or energy generation. This study focused on the azimuth angle of the solar panels, however the elevation angle (or tilt) of the panel is another specification upon which changes can be made. A more detailed discussion of layout optimisation is presented on our website.
What the Study Doesn’t Tell Us
While the study found a preferable layout for the hypothetical panels at Incheon International, this is specific to the layout of the airport. The positioning and direction of the runways vary between each airport and as such a bespoke solution must be found for each solar development for which significant glare is predicted.
The study focused upon glare towards the approach paths for the runways, however a thorough glint and glare study would assess reflections toward the air traffic control tower of the airport as well. Glare toward the control tower may prevent air traffic controllers from seeing sections of the aerodrome and hamper their ability to direct traffic safely. As such, layout optimisation must be conducted mindfully so as to avoid reducing glare toward one area, while accidentally causing glare toward another.
Figure 3: An air traffic control tower at dawn [4]
The solar panels within the study were mounted upon the ground, where changes to the azimuth and other specifications are quite feasible. However, the rooftops of buildings are another common place for solar panels to be located. For solar panels not placed on flat roofs, the opportunities for layout optimisation can be limited by the direction and tilt of the rooftop itself.
Finally, as the study notes, airports are often ideal locations for solar developments as they are located in wide open locations without many tall structures that could cause shadowing onto the panels. For solar developments in other locations, such as rural solar farms, changing the azimuth of panels may have a greater impact on the energy generation potential than as seen in the study, due to shadowing from nearby terrain or structures.
Why Layout Optimisation?
When an assessment of solar reflections predicts a significant impact, a common mitigation solution is the implementation of ‘screening’ – adding obstructions to prevent visibility of the reflecting panels. This works well for ground-based receivers, such as roads and houses, where the addition of a hedgerow or trees can easily obstruct reflections such that the road users or resident is no longer affected. A more detailed discussion of the role of screening in presented here.
For airborne receivers, including aircraft on final approach, the elevation of the pilot is such that they will see over any vegetation or fencing erected and still be subject to the glare. This is especially true when solar developments are on the airfield.
Without screening as a viable option in many cases, layout optimisation is used to reconfigure the panel design to minimise or eliminate the potential glare, thus allowing the renewable energy generation and aviation activity to happily coexist. An example of such a strategy succeeding is the solar development near Bournemouth Airport, located near the runway end and shown in the Figure 4 below.
Figure 4: Solar development near Bournemouth Airport (Image Copyright © 2024 Google)
While these solar panels are not as close to the runway as the hypothetical panels in the study, the development near Bournemouth underwent optimisation to find a layout that was both safe and productive.
How Pager Power Can Help
Pager Power is a leading provider of bespoke technical assessments, including glint and glare reports and layout optimisation, with its own in-house software for reflection calculations, cross checked with industry standard modelling for intensity calculations, its own guidance document to detail a methodology for the assessment of glint and glare that has been accepted by airports internationally, and strong relationships with many stakeholders including in aviation allowing for consultation to find solutions for developers and airports alike. For more information about what we do, please get in touch.
References
[1] Ritchie, H. (2024) What share of global CO₂ emissions come from aviation? Published online at OurWorldInData.org. Available at: https://ourworldindata.org/co2-emissions-from-aviation (Accessed: 8 April 2024)
[2] Kim, C. and Song, H.J., 2022. Glare-Free Airport-Based Photovoltaic System via Optimization of Its Azimuth Angle. Sustainability, 14(19), p.12781.
[3] Airplane Wing during Golden Hour (May 2018) from Pexels, Accessed: 9 April 2024. Available at: https://www.pexels.com/photo/photo-of-airplane-wing-during-golden-hour-1058772/
[4] Airport Sunset (October 2023) from Pexels, Accessed: 9 April 2024. Available at: https://www.pexels.com/photo/airport-sunset-18848159/
