Solar farm developers should carefully consider the impact of reflections and glare from photovoltaic (PV) panels, especially before construction near towns and cities. Sunlight reflected from photovoltaic panels can cause bothersome visual discomfort and even dangerous glare to surrounding receptors such as residents, motorists or pilots.
Sunlight reflecting off solar panels can be experienced in two forms: glare – a momentary flash of bright light and glare – a continuous source of bright light. Reflection and glare can result in afterimage which is a visual illusion in which an image persists after exposure to the original image has ceased. Passing motorists can be affected, for example, posing a potential traffic hazard, while nearby communities could be disturbed by glare from the sun.
Developments can increasingly be located close to urban areas
Recent changes to regulations for licensing independent power producers have opened the door to private renewable energy projects of up to 100 MW. While most commercial solar projects to date have been located in remote areas, these developments can now increasingly be located closer to urban areas, according to Chris Dalgliesh, partner and principal consultant at SRK Consulting.
“We have seen a few solar projects being established quite close to cities, and there will be more to come,” Dalgliesh said. “This increases the likelihood that reflections and glare will affect human settlements and other receptors more often.”
Sue Reuther, Partner and Principal Consultant at SRK Consulting
Sue Reuther, partner and principal consultant at SRK Consulting, pointed out that while there is generally a high level of public support for renewable energy projects, the growth of solar farms has shown that reflections and glare could have significant visual impacts. As such, these aspects have become an essential component of the Visual Impact Assessments (VIA) that SRK Consulting performs for Environmental Impact Assessments (EIAs).
Kelly Armstrong, an environmental consultant at SRK Consulting and a specialist in visual impact modeling, said developers need accurate scientific predictions of how their solar installations might affect the local environment.
“A range of parameters are loaded into the glare and glare modeling software to assess whether glare or glare from solar panels impairs vision or causes discomfort,” Armstrong said. “This includes the precise location of the project, the local topography and the height of the mounted panels – as well as the axes and aspect of the photovoltaic generators.”
Exact longitude and latitude determine the sun’s position through the seasons, allowing the model to account for how the sun looks every day of the year. This is important to measure not only the occurrence of reflections or glare, but also to quantify the exposure (minutes per day) to this impact.
The model requires specific parameters
Chris Dalgliesh, Partner and Principal Consultant at SRK Consulting
The photovoltaic panels of a solar power installation can be fixed or can rotate on a single axis or on two axes, she noted. The model requires specific parameters of the proposed PV generator, among others the maximum following angle of the panels, the angle of repose and if rollback technology is used.
The position of the receivers in relation to the solar energy installation is also critical. Typical receptors could include buildings, houses, roads and flight paths, with dozens of different points around the project all needing to be assessed to understand the potential impact. Topography is important, as elevated areas around a solar farm could be more prone to reflections and glare. Dalgliesh noted that a field of view is usually an essential part of visual impact assessments and shows the areas (receptors) from which the solar farm would be visible.
“This spatial map guides our understanding of who or what will be visually affected by a development,” he said. “We can then identify receptors that are likely to be most sensitive to visual impacts, including reflections and glare.”
Accurate reporting for strategic decision making
The result of the modeling, Armstrong explained, is to accurately predict exposure and duration of glare and glare impacts down to the minute every day – for each key receptor.
Kelly Armstrong, environmental consultant at SRK Consulting
“The accuracy of these models allows us to report very detailed glare results,” she said. “For example, we can predict that a particular receptor will experience glare for up to 15 minutes between 4:30 p.m. and 6:30 p.m. during the summer months.”
This provides the basis for strategic decisions, either on the precise location or orientation of the solar farm, or on the appropriate mitigation measures. While there are currently no legally specified thresholds for reflections and glare, she pointed out that there are international best practice guidelines to follow.
“These guidelines incorporate tolerable exposure thresholds, i.e. maximum 60 minutes per day, for more than three months of the year, beyond which mitigation measures must be put in place,” he said. she said “Our reports include mitigation measures, aimed at avoiding any glare affecting receivers.”