Page 38 - Energize September 2022

VIEWS AND OPINION

Keeping an eye on PV glint and glare

By Chris Dalgliesh, Sue Reuther and Kelly Armstrong, SRK Consulting

ith more solar farms likely to
be constructed near towns and
Wsettlements, developers will have
to carefully consider the impact of glint and
glare from photovoltaic (PV) panels before
they proceed.
Global experience shows that sunlight
reflecting off solar panels can cause
annoying visual discomfort and even
hazardous glare to residents, motorists or Chris Dalgliesh Sue Reuther Kelly Armstrong
pilots. Sunlight reflecting off solar panels can
be experienced in two forms: glint which is solar installations might affect the local environment. “A range of parameters are loaded
a momentary flash of bright light; and glare into glint and glare modelling software to assess whether the glint or glare from solar panels
– a continuous source of bright light. Both will impair vision or cause discomfort,” Armstrong says. “This includes the project’s precise
glint and glare can result in an after-image, location, local topography and the height of the mounted panels – as well as the axes and
which is a visual illusion where an image aspect of PV arrays.”
persists after exposure to the original image The exact longitude and latitude determine the position of the sun across the seasons,
has ceased. Motorists passing by may be allowing the model to account for the aspect of the sun on each day of the year. This is significant
affected, for instance, posing a potential in measuring not just the occurrence of glint or glare, but to quantify exposure (minutes per day)
traffic hazard – while nearby communities to this impact.
could be disturbed by sunlight reflections. Photovoltaic panels in a solar energy installation can be fixed or can rotate on a single
Recent changes to the licensing axis or double axis, she noted. The model requires specific parameters of the proposed PV
regulations for Independent Power array, such as the panels’ maximum tracking angle, resting angle and whether backtracking
Producers have opened the door for private technology is used.
renewable energy projects up to 100 MW. The position of the receptors relative to the solar energy installation is also critical. Typical
While most commercial solar projects receptors could include buildings, homes, roads and flight paths, with dozens of different points
to date have been located in remote around the project all having to be assessed to understand the potential impact. Topography
areas, these developments may now be is important, as elevated areas around a solar farm could be more exposed to glint and glare.
increasingly located closer to urban areas. A viewshed is typically a vital component of visual impact assessments and shows those areas
We have seen a few solar projects (receptors) from which the solar farm would be visible.
being established fairly close to towns, This spatial map guides our understanding of who or what will be visually affected by a
and there will be more of these to come. development. We can then identify those receptors which are likely to be most sensitive to visual
This increases the likelihood of glint and impacts – including glint and glare.
glare impacting more often on human “The outcome of the modelling”, explained Armstrong, “is to accurately predict the exposure
settlements and other receptors. and duration of glint and glare impacts down to the minute each day – for each key receptor.”
Sue Reuther, partner and principal “The accuracy of these models allows us to report very detailed glare results,” she says. “For
consultant at SRK Consulting, highlights example, we can predict that a particular receptor would experience glare for a maximum of 15
that while there was generally a high minutes between 16h30 and 18h30 during the summer months.”
level of public support for renewable This provides the basis for strategic decisions, either on the precise location or orientation
energy projects, the growth of solar farms of the solar farm, or on appropriate mitigation measures. While there are currently no legally
had shown that glint and glare could specified thresholds for glint and glare, she pointed out that there are international best practice
be significant visual impacts. As such, guidelines to follow.
these aspects have become an essential “These guidelines incorporate tolerable exposure thresholds, viz., maximum 60 minutes
component of Visual Impact Assessments per day, for more than three months of the year, above which mitigation measures must be
(VIAs) that SRK Consulting conducts for implemented” she adds. “Our reports include mitigation measures, aiming to avoid any glare
Environmental Impact Assessments (EIAs). affecting receptors.”
Kelly Armstrong, environmental Reuther highlighted that, as a leader in the field of EIAs, SRK is among only a few
consultant at SRK Consulting and a consultancies with advanced in-house expertise in glint and glare modelling – a niche likely to be
specialist in modelling visual impacts, in growing demand.
says that developers need accurate,
science-based predictions on how their Send your comments to rogerl@nowmedia.co.za

energize | September 2022 | 36