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Anti-glare PV modules

How to prevent the solar system from glare for the neighbours?

As sensible as the use of solar energy is, this technology sometimes brings with it difficulties. One problem is glare from solar modules.

Like any type of energy generation, electricity production from sunlight is also associated with emissions. Some of the sunlight is reflected off the surface of solar modules. These reflections can lead to significant nuisance in residential areas or to safety risks in transport infrastructure.

Typically, glare problems occur primarily with PV systems that are not orientated to the south. In addition to east and west-facing roofs, solar modules on north-facing roofs in particular are associated with a high risk of glare, as the sunlight tends to fall in such a way that it is reflected obliquely downwards onto the neighbouring property, where it can temporarily impair the use of the terrace, dining room or study. In mountainous terrain, however, south-facing roofs can also be problematic if, for example, the neighbour lives much higher up.

Whether the reflections also represent problematic glare emissions depends on various factors. In residential areas, the duration and frequency of the glare times are generally used to decide whether it is still a reasonable level of immissions at a particular viewing point. If the glare lasts for more than 30 minutes at a time on more than 30 days a year, the German Federal/Länder Working Group for Immission Control assumes that the glare situation is unacceptable and the system operator is obliged to take remedial action.

The data on glare duration and intensity is usually determined by simulations carried out by glare assessors. In addition to the orientation, size and position of the system and the location of the observer, the quality of the solar modules is also taken into account in high-quality reports. In particular, the glass surface of the modules defines how high the reflected brightness is.

Although conventional solar modules usually have an anti-reflective coating, this is primarily used to increase yield and is far from being able to reduce the reflected luminance to a level that is tolerable for the human eye. For this reason, there are specially texturised glasses that are used for so-called ‘low-glare’ solar modules. The aim of texturing the glass surface is to spread out the reflection of the incident light and thus reduce the brightness. Unfortunately, due to the manufacturing process, the textures in the glass are not sufficiently pronounced to fulfil their task. As a result, neighbours often complain about unacceptable glare despite the use of such modules.

However, the anti-glare coating from Phytonics, which is based on bionic microstructures, represents a safe and simple solution. This can be applied as a self-adhesive film to any modules with standard glass, meaning that existing systems can also be retrofitted with anti-glare coatings. It is also possible to purchase new modules that have already been coated with film ex works. The extremely robust film not only protects neighbours from annoying glare, but also increases the modules’ resistance to hail and UV-induced ageing. And thanks to the improved coupling of flat incident light, the owner can look forward to a higher electricity yield at off-peak times.