Updated: Aug 12, 2020
Water is nature's best cleaning agent.
Listed below are important factors to consider before setting out to clean your solar panels with water, even if you intend to outsource the cleaning to professionals.
1. Type of water:
Reverse osmosis (RO) water is the ideal option.
If RO is not available, rainwater or tap water with low mineral content and a total hardness that is less than 75 mg/L may be used.
Water with a significant amount of dissolved minerals, often known as hard water, leaves behind a residue on the glass. This causes the formation of stains or scaling on the glass that damage the glass and reduce the amount of sunlight going through.
Hence before you clean your panels, you should consider water availability.
Water pressure should not exceed 35 Bar at the nozzle.
The water pressure being referred to here, is the force with which the water will exit the pipe being used to clean the panels. It is also an indication of the force with which the water will hit your solar panels.
A nozzle is used at the end of the pipe to control the water's pressure. Nozzles come with a variety of added features like attachments for cleaning fluid and are capable of a wide range of pressure settings.
The temperature of the water being used for cleaning should ideally be the same as the solar panel temperature at the time of cleaning.
A maximum difference of 20 degrees is acceptable. The grater the difference between the water and the solar panel the greater the chances of the glass cracking due to a sudden temperature change (thermal shock).
4. Time of the day
Solar panels should be cleaned only during low light conditions.
After sunset and before sunrise, when the production of solar power is at its lowest, is the ideal time to clean panels. This is because when the panels are not generating power the risk of an electrical shock hazard is minimum.
The panels will also be cooler at these times and thus closer to ambient temperature so they are less likely to be at a very different temperature from the water being used to clean it.
5. Stubborn Stains:
Soak the stain in a stream of water. Use a soft sponge or micro-fibre cloth or a very soft bristle, non-conductive, non-abrasive brush. Rinse the module subsequently with plenty of water.
Never, ever scratch/ scrub the surface of the solar panel to remove stains.
This irreversibly damages the ARC i.e. 'Anti- Reflective Coating' on the glass of the panel.
If the stains have been on the panels for a while, we recommend contacting your panel installer/manufacturer for options of approved cleaning agents.
6. Panel Back-side
The back surface of the solar panel doesn’t require routine cleaning like the front surface.
Specific cleaning of dirt or debris may be carried out if dirt is observed on the back sheet. Only a soft sponge or micro-fibre cloth may be used.
While cleaning the dirt on the backsheet it is important to avoid the use of any sharp object, which can damage the material cause a slit.