Solar Power plants are essentially maintenance free as they do not consist of any moving parts. However, panel cleaning is one aspect of solar panel maintenance that should not be taken lightly. When Google conducted a groundbreaking experiment at their 1.6 MW solar farm in Mountain View, California, it was found that solar panel cleaning was “the number one way to maximize the energy they produce.” Cleaning solar panels that had been in operation for 15 months almost doubled their output of electricity (1).
Why periodic solar panel cleaning is necessary ?
Solar panels work by converting sun-light that falls onto solar panels into electricity. The more light that hits a panel, the more power it will generate. During the course of time, when dust and other materials deposit on the solar panel surface, it essentially reduces the amount of light hitting the panel and so reduces its output.
When Solar panels are cleaned, direct sun rays falling on the solar panels increases and it corresponds to increase in units of electricity produced by panels. According to an estimate, regular cleaning of solar panels has potential to increase power output by as much as 30%.
How to clean solar Panels ?
Solar Panel Cleaning Guidelines:
While cleaning solar panel is no rocket science and can be equated with regular washing of your car. There are certain things that need to be remember to guarantee elongated service life and efficiency of the system. Wrong cleaning practices, bad quality water and use of inappropriate cleaning agent may damage modules and other array components and lower system performance as well. It is also essential to train the cleaning personnel on proper cleaning methods and use of appropriate cleaning tools.
Safety of personnel:
- Solar modules are connected in series and it generates upto 800V DC. Cracks in modules or damaged cable or joints in a string are extremely dangerous for cleaning person particularly when the modules are wet. Even during low level of sunlight the array will generate lethal voltage and current. Therefore, it is important to inspect modules thoroughly for cracks, damage, and loose connections before cleaning. Cleaning personnel shall wear appropriate electrically insulating Personal Protective Equipment (PPE) during cleaning.
- The recommended time for cleaning modules is during low light conditions when production is lowest. However, when sun shines during the day, the panels also get heated up and cleaning solar panels with cold water in evening may result in thermal shock for panel which can permanently damage them. Hence, the best time to clean Solar Panels is early mornings, when the plant is not in operation, risk of electrical shock hazard is minimum and also temperature of solar panels is not high.
Quality of water:
- De-ionized water should be used to clean the modules. If de-ionized water is not available, rainwater or tap water can be used. Tap water must be of low mineral content with total hardness less than 75ppm. Water must be free from grit and physical contaminants that could damage the panel surface.
Use of cleaning agent:
- A mild, non-abrasive, non-caustic detergent with deionized water may be used. Abrasive cleaners, Acid or alkali detergent must not be used.
- Don’t use metal objects or harsh abrasive products for removing caked on materials – scratching the glass on a solar panel can affect its performance as scratches will cast shadows.
Removing stubborn marks:
- To remove stubborn dirt such as birds dropping, dead insects, tar etc., use a soft sponge, micro-fiber cloth. Rinse the module immediately with plenty of water.
- Water pressure should not exceed 35 bar at the nozzle. Use of high pressure hoses for cleaning may exert excess pressure and damage the modules.
- Temperature of water used for cleaning should be same as ambient temperature at the time of cleaning. Cleaning should be carried out when the modules are cool to avoid thermal shock which can potentially cause cracks on the modules.
Why Rainwater Will Not Clean Your Solar Panels
A good way to illustrate that why rainwater will not clean solar panels is by considering example of your car windscreen. If you leave the car in rain for cleaning, does it really get cleaned. The answer is “NO” why? . Because, rain water contains airborne dust particles that settle and attach to the surface after the rainwater evaporates. Hence, you see small round dirt circles when the car windscreen dries after rain. Same principle applies in Solar Panels.
When Solar Panels are washed by rain water, though it does clean the solar panel to some extent, however, when panel gets dried, the water evaporates leaving small circles of dirt on the solar panels.