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Solar calculator as a tool to evaluate glare effect

Solar calculator can be a perfect tool for financial analysis of PV project, getting solar radiation data or even for glare analysis. Thinking about the latter one, we wonder if reflected sunlight from roof-mounted PV could adversely affect residential neighborhoods?

Modules can reflect some sunlight but since they use low-iron and high-transmission glass, their reflectivity is highly reduced and glare is generally not produced. What’s more, light-trapping techniques and anti-reflection coatings are used by module manufacturers. In consequence, solar module (depending on the angle of incident solar rays) reflects less than concrete, vegetation or even soil.

Nevertheless, modules are considered smoother and more polished than surfaces like roads or plants, and reflected light is more concentrated compared with tough surfaces.

Residential solar vs. airports

When it comes to residential sector, sunlight reflected off a roof-mounted PV array will most likely travel skyward. Even if a PV array generates some glare, a neighbour is unlikely to see that glare from the height of a residential building. Airports are different case. Although there shouldn’t appear any hazard for navigation, modules installation on the airport requires a geometric glare analysis.

Glare analysis

The surface reflectance depends on different materials (e.g. fresh snow reflects 80-95% and black asphalt only 5-10%). In case of reflectivity of a PV array, it will be a function of its albedo as in case of any other surface. The higher the albedo, the higher is the rate of reflected sunlight.

The distance between a PV array and neighboring properties also important in glare analysis. When the angle of reflectance is high, reflected sunlight travels above neighboring residences, even those located close to the array. Therefore, the more distance there is between a PV array and a neighboring home, the more likely the reflected sunlight is to travel over the top of that building.

Glare evaluation can be performed using any solar calculator. Tools like that are available for instance on University of Oregon website or on Sandia National Laboratory website.

To evaluate solar radiation data, you can use EasySolar app. You can also use this tool to design PV and to prepare customer proposals.

Based on Roger’s Colton article on SolarPro.