Solar panel cleaning is one of the most important – yet most overlooked – part of solar PV system maintenance.
The primary role of a solar panel is to convert light into electricity; therefore it stands to reason that a clean panel will generate more power than a dirty one. However, cleaning your solar panels isn’t just about getting the most amount of power from them, it’s about ensuring that they will continue to perform correctly well into the future.
To understand why solar panels need to be cleaned – and why ‘self-cleaning solar panels’ are a myth – it’s important to understand the physical characteristics of a solar panel. Firstly, the surface of a solar panel is not completely smooth; all solar panels have an anti-reflective coating (ARC) applied to the glass during production. This ARC ensures that sunlight is absorbed into the panel rather than bouncing off. The downside of this is that the lightly-textured surface allows certain contaminants – bird mess and lichen for example – to ‘latch-on’ to the panel making it tricky for rainwater alone to remove.
‘If the operating current of the overall series string approaches the short-circuit current of the “bad” cell, the overall current becomes limited by the bad cell. The extra current produced by the good cells then forward biases the good solar cells. If the series string is short circuited, then the forward bias across all of these cells reverse biases the shaded cell. Hot-spot heating occurs when a large number of series connected cells cause a large reverse bias across the shaded cell, leading to large dissipation of power in the poor cell. Essentially the entire generating capacity of all the good cells is dissipated in the poor cell. The enormous power dissipation occurring in a small area results in local overheating, or “hot-spots”, which in turn leads to destructive effects, such as cell or glass cracking, melting of solder or degradation of the solar cell.’
Lichen is a composite organism that thrives in bright, warm and wet conditions; additionally, lichen growth is particularly problematic on surfaces that it can latch-on to.
It is recommended – in order to avoid the challenges described in this article – that you have your solar panels professionally cleaned at least once a year.