Five videos that highlight the problem of glint and glare

By Danny Scrivener

Glint and glare is often overlooked, misunderstood or underestimated when projects are in the design stage. Here are five videos that help illustrate the problem of glint and glare, and why it should be an important consideration for building developers and planners.

Solar farm glint and glare

This video demonstrates a typical glint and glare issue arising from a solar development. The duration and intensity of reflections from a solar farm 3.75km away are evident.  A glint and glare assessment would provide the developer with the information to determine what receptors are likely to be affected before construction. What do we mean by receptors? This can be surrounding dwellings, road users, local points of interest or aviation activity. A glint and glare report will give the developer a detailed assessment of:

  1. The likelihood of a receptor receiving reflections from the solar farm or development throughout the site geometrically.
  2. Consider terrain, buildings, vegetation and other mitigating factors.
  3. The proportion of panels within the site that would be illuminating particular receptors.
  4. The date, time and duration to which those reflections would occur.
  5. The height and length of screening required in order to mitigate reflections as far as reasonably practicable.

Rooftop photovoltaic (PV) glint and glare

Rooftop solar developments are not immune to glint and glare issues either.  Rooftop installations can often cause issues regarding glint and glare. This is due to the height and angle of the panels compared to the surrounding environment and proximity to receptors. In the case of this video, the effects are unlikely to be able to be mitigated through screening. In this instance, quantification and assessment of reflections would bring clarity to planners or local stakeholders as to the relative short duration of reflections. Anecdotal evidence about glint and glare issues are best countered by a glint and glare assessment.

Solar reflections from "Walkie-Scorchie"

This well publicised occurrence is a perfect example of glint and glare from a newly constructed building. Originally, the now infamous ‘Walkie Talkie’ building on 20 Fenchurch Street had an exposed glass façade, on both the north and south elevations of the building. The unintended consequences of the concave southern façade were solar reflections that affected road users, pedestrians and businesses on Eastcheap street below the building. The concave shape of the structure allowed solar reflections to be reflected, converging and intensifying towards receptors below. The solution to this issue was a costly retrofit of the buildings south façade to prevent reflections occurring. If a glint and glare assessment had been undertaken as part of the design process, the effects of the building’s façade could have been determined, and the design altered before construction. An assessment could have scuppered the building’s popular nickname, the ‘Walkie Scorchie’.

Vdara hotel "Death Ray"

This video shows the same phenomenon, as described above, occurring at a hotel in Las Vegas. The concave shape of the building, combined with the reflective façade, caused particularly intense reflections towards the pool area of the hotel. After reports of concentrated reflections burning hotel patrons, the media quickly dubbed it the ‘death ray’.  The cost of mitigating these effects post construction far outweigh the costs of a glint and glare assessment and changes at the design stage. Negative reaction to a project with regard to solar reflections can be easily assessed with a glint and glare assessment.

Glint and Glare effect on aviation

The video highlights the case of a solar thermal energy plant in the Mojave Desert, south-western USA. Pilots in the vicinity of the plant are reporting the plant as a major distraction during the flight. The video highlights two important points. The first is that aviation receptors can become a consideration for a solar development even in areas not in close proximity to airports. Often, aviation receptors are only considered in locations that are close to airports, as take-off and landing are the most critical phases of a flight where distractions cannot be tolerated.

The second important point is that it isn't just a traditional PV cell solar development that can affect receptors. The 360 degree orientation of heliostats (mirrors) around the site allows reflections to occur for a much larger range during the year. The highly reflective surface of the heliostats increase the effect for aviation receptors, as a much higher percentage of light is reflected off of the surface of the heliostat compared to a PV cell.

From £1195 - Comprehensive Glint and Glare Assessments are available from Pager Power

Posted By: Danny Scrivener

on 09 November 2017

danny@pagerpower.co.uk

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