Guidelines for module cleaning in solar projects
Cleaning of modules is very important for achieving desired yield and performance ratio in solar power project. It is observed that many times the plant performance is inferior just because the PV modules have not been clean properly and if they are clean the water used for cleaning is not good water. Dirt and bird excreta are two major factors which affect the module output. Therefore, it is recommended that following precautions should be taken while cleaning PV modules.
- Module should be clean in late evening night or early morning hours in order to avoid thermal expansion and cracks because of temperature difference between the water and module surface temperature.
- The water used should be not too cold as well as not too hot. Its temperature should be Luke warm water. The water used should be free from dirt and mud. Typically, the water used should be de-mineralized water so that, salt preposition of module surface do not take place. Salty water may also lead to corrosion on module frame as well as the mounting structures. Now days, Establishing RO plant for the cleaning water requirement, is becoming a common practice.
- Many times the module cleaning is done by water spray jets. The pressure of water spray should not be very high in order to avoid damage on the glass surface due to high pressure of water.
- Many times it may also require using a soft cloth/ sponge/ micro-fiber cloth to clean the glass surface.
- Many times it is observed that some of the dirt/ other marks still remain on the module surface. This will leads to hot spot on the module cell and further it will damage the complete module. It should be cleaned through a chemical liquid which is bio-degradable in nature in order to avoid contamination of soil beneath the PV module. If any of the cleaning agent is used the module should be immediately rinsed with plenty of water to remove the chemical agent on the module surface. Acid or alkaline detergents should be avoided to use for cleaning the PV modules as they may cause corrosion and erosion of the module frame as well as the mounting structure.
- While cleaning the modules people should not be climb of walk on module surface as it may cause damage / micro cracks in the PV modules.
- Now days, automatic machines are available in the market for the module cleaning purpose. It is a tradeoff between the cost of cleaning the PV modules and energy yield. A proper analysis should be conducted to decide the cleaning cycle of PV modules so that the energy yield can off-set the cost of cleaning. Typically, a 5 WM solar PV plant improvement in energy yield by one percent generates about 25 lac / year as additional revenue. Hence, it is possible to increase the energy yield in large plant and increase the plant profitability by maintaining proper cleaning strategy and optimum cleaning cycle.
- The cleaning wiper used should be non- adhesive and the water should be removed from top to bottom approach.