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Why do solar panels need cleaning?
Unlike windows the panels on your roof need to have a clean and clear surface to ensure they are working at their maximum efficiency. If they are not at their optimum performance it means they are not producing the amount of electricity that they could be.
Bird droppings do not wash off easily with just rain. This will affect the panels performance. To reduce the problem of bird droppings you can put a plastic mesh over your TV aerial to stop birds using it as a perch and messing on the panels below.
On the roof and angled skywards the panels will attract dirt, dust, soot, pollen, tree sap and salt crystals in costal regions creating a fine layer of grime. This layer reduces the amount of light reaching the silicon cells under the glass surface and reduces the panel's effectiveness. A solar panel that has never been cleaned could be producing almost a third less power than it otherwise could be. Some have reported a ten to fifteen percent loss of solar output due to dirty panels. Boston University in the States have done some research on this and claim that as little as a few grams of dust per square metre can halve their efficiency.
From the ground the panels may appear to be clean, just like your windows. Up close however you can see the grime that has built up from the dirt and pollution in the air. A more noticeable deposit that can be left on panels is bird droppings. These tend to completely block the light from areas of the photovoltaic panel and can considerable reduce its effectiveness.
How to clean solar panels
Some people may try to clean them themselves although this is not recommended. Firstly it can be dangerous trying to reach your roof without the proper equipment. Secondly you may end up damaging the panels either accidentally or by attempting to clean them yourself.
It is recommended that you hire a cleaning company that provides a solar panel cleaning service that know how to clean solar photovoltaic panels properly. Do not just hire a window cleaner unless they have specific knowledge and experience in this area. They may end up at worst damaging the panels or not effectively cleaning the panels so you end up no better off.
Hire a company that has the proper solar panel cleaning equipment
A company who is experienced in cleaning PV panels will have the proper equipment. Using standard windows cleaning tools means that they will end up leaving soap residue behind and hard water spots as any water on the panels surface evaporates.
A professional cleaner will use a water fed pole system that can reach the panels on your roof from the ground. They will use a pure water system that uses de-ionised water and a soft head brush attachment so as not to damage the panels. No chemical should be used as these can cause damage.
How often should I clean my solar panels?
In the UK this is something that we do not have much experience or knowledge with. Luckily solar panel cleaning services in other countries have been established for many years and many recommend getting them cleaned twice a year. Some suggest you get them cleaned every couple of months.
For the best results the first clean should be at the start of spring as the days lengthen and the amount of sun reaching the panels increases. Later in the summer they should be cleaned again. For the UK climate this seems to be the best solution.
If you have free solar panels installed or are thinking of getting them you should check with the installer to see if they pay for getting the panels cleaned. It is in their interest to keep them running at optimal efficiency.
Won't the rain wash the dirt off the panels?
During the summer there may be long periods where it does not rain and the summer is when photovoltaics produce the most electricity. When it does rain some of the loose dirt is removed but more is deposited in its place. Some types of soiling such as that from birds will remain for many weeks and even months if they are not cleaned.
Does cleaning a solar panel really improve its efficiency?
The best way to prove this is to record the amount of power being generated before the panels are cleaned. Get the panels cleaned and then compare the new reading with the ones that you took earlier. It is best to do this on a sunny day where the weather is pretty constant as the sun disappearing behind the clouds intermittently is going to affect the results.
Is there a way to prevent my solar panels from getting as dirty?
At the moment for residential installations the most practical and proven method is to just get them cleaned regularly. There are special coatings that can be applied to the surface of the panels which claim to prevent dirt from sticking. If you are going to go down that root you need to make sure you check with the panel manufacturer first.
There are other systems that are not really practical for residential systems such as spray systems built into the roof that regularly hose down the panel. There are even solar panel cleaning robots that can clean them. There is also a system that uses an electric charge to lift the dust of the surface of panels.