Measuring the Glint and Glare - Simulation versus Reality
In the context of a Solar Glare Assessment we had a chance to investigate the glaring effect of an existing roof-top PV plant in detail and measure the glare at several points of interest. The duration and the effect of the reflections were compared with simulation results. The glare duration, direction and the spatial angle of the reflections in the simulations were exactly in accordance with reality as documented in the video below.
The objective of the assessment was the calculation of glare over a yearly cycle. In order to verify, that the observed glare is more than just a temporary phenomenon, the glare calculation had to be done for a whole year. In this process a glare duration of more than 4 hours per day was computed, which had to be rated as unresonable nuissance. Consequently the PV plant was modified and prective fences were built. Read more about the details of a solar glint and glare calculation.
New algorithms for Solar Glare Assessment now allow a detailed simulation in three-dimensional space. For the first time not only mirror images of the sun, but also scattered rays of lights are taken into account when computing the glaring hazard. PV-panels and solar thermal panels often have a rough, structured surface in order to absorb more light. This prolongs the duration of reflections from the sun passing by over the sky. In addition, it makes the reflection of the sun appear larger.
The new algorithm for reflection calculation guarantees a higher, minute-fine resolution during the day and a daily resolution over the whole year. Now that the point in time and the duration of a glare from simulation correspond exactly with the measurements in nature, better evidence is provided for the assessment of the reasonableness of a glaring hazard. Line of visions to the glaring surface are also calculated exactly, which is especially relevant in glare assessments for road traffic. Finally, the complete representation of all scattered sunrays allows for a precise 3D-rendering, so that the simulated images and videos of the planned installation provide a realistic impression of the structure and its glaring hazard even before construction.