Glint and Glare study in Bavaria verifies glaring hazard for Deutsche Bahn

PV LandshutThe department for city-planning and -development Landshut / Germany asked for a Solar Glare Assessment according to the Notes about Measuring, Assessment and Reduction of Immissions of Light (Hinweise zur Messung, Beurteilung und Minderung von Lichtimmissionen) - LAI-2012. The authorities saw the potential that the railroads passing by north of the PV park could face a glaring hazard when travelling east or west of the plant. Additionally, it had to be verified, if the neighbouring land parcels (for which a housing development is on the way) would be subject to a glare nuisance.

The Glint and Glare study according to guideline LAI-2012 was straight forward - the reasoning for the (negligible) glaring reflection proofed to be more difficult. As the glaring calculation showed, reflections could not be completely ruled out, however these were not "considerable" as defined by the LAI-2012. On the one hand the small angle between reflecting area and the position of the sun lead to an attenuation of the computed glare duration, on the other hand it had to be shown that the front side of the PV panels were not visible from all locations, but only parts of the plant. Fortunately these attributes are already implemented in our simulation-software (which we continuously improve), so that the exact angles of the line of vision as well as the attenuation factors could be calculated with ease.

 The discussion with the German Länder-Arbeitsgemeinschaft für Immissionsschutz (National Work Group for Immission) unfolded that German guideline LAI-2012, even though not obligatory, still is the state of the art for the assessment of solar glare reflections and had already been used as a reference in several court trials. This makes the LAI-2012 a useful tool for the difficult assessment of the reasonableness of glaring. It provides clear limits for the maximum tolerable glare duration during a day or during a year.

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