In the PV cleaning market many different methods are available for cleaning PV modules. Which cleaning system should be chosen depends, among other things, on the local conditions, the size of the installation, the module type and the degree of pollution. In this article, the most frequently used techniques are described and instructions given, which should be obeyed in every case.
1. Cleaning with a brush and a telescopic rod
Cleaning with a brush and a telescopic rod is the most common method for cleaning photovoltaic modules. This method is used especially on easily accessible PV systems on house roofs or cowsheds. The water is fed by the telescopic rod to the top of the module array and sprayed onto the modules by means of nozzles. With rotating brushes, the water pressure also drives the brushes at the same time.
2. Cleaning from the roof ridge
Another method for the cleaning of rooftop systems is cleaning from the roof ridge. The usual way of doing this is by letting down a rotating brush attached to the ridge with a rope. This procedure is often used, particularly in the case of larger roof systems.
3. Cleaning robot
For larger photovoltaic installations or solar parks in remote regions cleaning robots are attractive. The systems are usually run on rails and traverse the module array automatically. Systems have been developed that even clean without water. These are particularly attractive for arid regions. Other systems start cleaning as soon as it starts to rain, triggered by sensors. Whether the installation of a permanently integrated cleaning system is technically feasible and financially viable should be carefully investigated by the technical management. When using cleaning robots, care should be taken to ensure that the PV modules used are certified for this purpose. The cleaning process can damage the surface of the modules over time and cause a reduction in yield.
An often recurring question is whether it is also possible for a photovoltaic system to clean itself. It is theoretically possible, but this is very time-consuming. Firstly, some rules must be followed when cleaning. Intensive examination of the subject matter is thus always a prerequisite. Secondly, in most cases, it is not economically viable for an installation to clean itself, since the purchase of the cleaning systems is very expensive. In addition, a residual risk remains that the system will get damaged or, in the worst case, will harm itself.
Most important information
- Ordinary cleaning agents should not be used. There is a risk that the module’s surface or its seals may be damaged.
- Demineralised water should be used to avoid deposits. Limescale residues can lead to reductions in yield.
- Use only specially designed cleaning brushes. Never use hard or pointed objects.
- The PV installation must not be entered under any circumstances; otherwise there is great danger for the individual and the system.
- Always work from top to bottom.
- The module manufacturer’s instructions must be observed.
- The PV installation must be tested for exposed cables and defective modules before cleaning. There is a risk of electric shock, particularly in wet conditions.
- Cleaning should be carried out early in the morning or late in the evening, especially in hot regions.
- The maximum permissible water pressure (module assembly instructions) must be observed.
Anyone who decides to have their system cleaned by a photovoltaic cleaning company should pay attention to the method used as well as the price. Because, as the list of the most important information shows, there are many factors that need to be taken into account when cleaning.
In the next article in the series “Cleaning solar installations”, we describe ways of recognizing and calculating yield losses with the help of PV monitoring.
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