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Does the Rain Clean My Solar Panels?


Does the Rain Clean My Solar Panels?

Many people believe that rainfall provides cleaning of solar panels. Homeowners of solar powered houses will, in most cases disagree. Solar panels are built to create electricity to power your house, business, school or even electric car, but they don’t have the self-cleaning and maintenance free ability. We met JK, the founder and co-owner of ProSolarClean of Glen Ellen, CA, company specializing in solar cleaning services to discuss how to properly clean solar panels.

SCG: Jan, before we will discuss that topic, please take us back and tell me how you came up with your startup idea? 

JK: Back in 2008 I was working as a designer for a small solar company. With every solar installation sold, I got the same question from my customers: How will I maintain the cleanliness of my solar panels? The very common answer at those solar pioneer times was: The rainfall will keep your solar panels clean. One customer said: Rain does not wash all the dirt and grime away from my car, so why would I expect the same with my solar modules? The next day I went to my office and did deep research. There was not much information about that problem at that time, some of the information was misleading, but one thing was clear and obvious from the beginning. Proper maintenance and regular cleaning keep the energy output at the maximum level and also prolongs the life span of solar modules.  

SCG: Did you start your company right away at that time? 

JK: Not at all. I thought it is a good idea but I needed more time and more information. It took me one year, but I learned why, how, when and especially what kind of cleaning device fits best for this kind of job. 

SCG: Why do I need to clean my panels? 

JK: Besides the esthetic point of view, solar panels have to be cleaned regularly in order to keep them functioning at optimum level and to ensure their longevity. Over time dust, dirt, pollen, mold, bird droppings, leaves or all kind of debris can accumulate on the glassy surface of your solar panels. Anything that blocks the light transmission to your PV (photovoltaic) or thermal panels has the potential to lower the performance. 

SCG: What is the percentage of energy loss due to dirty solar panels? 

JK: That all depends on the area, design of the photovoltaic system, type of dirt and length of the time in between services. Usually we see 10 – 25% increase after cleaning service in a residential solar installation and 15 – 35% increase in commercial solar arrays. Almost all wineries with flat rooftop solar arrays are extremely sensitive to the soiling and also to the black mildew covering the solar panels. The energy output loss can reach up to 55% if cleaning and maintenance has been neglected. 

SCG: Can you describe the cleaning system your company is using? 

JK: We are using a German made mobile brush roller system purely driven by pressurized water. The soft bristles of this 39” wide brush have been developed and designed for solar modules cleaning only. We have our own de-ionizing and de-mineralizing system to purify the water being used for cleaning of solar panels. This is the key to properly clean the surface of solar installations.   

SCG: Why do I need mineral free water? 

JK: Using municipal or well water for cleaning will leave water spots due to naturally occurring minerals present in the water. If minerals are not remove from the water the sun will literarily bake the minerals into the glass surface and cause permanent damage. 

SCG: Rain water does not have any content of minerals so explain to me why rain is not enough to clean solar panels?

JK: Rainwater will provide a limited amount of cleaning to your solar panels. It will remove free dusty particles if panels are tilted, but rain does not remove the grime or bird droppings. In fact, water (light rain or morning dews) is one of the main reasons solar panels get dirty. On commercial flat rooftop solar installations, where panels are tilted at about 5 degrees or less, rain can lead to dust accumulating in the lower row of cells of each panel, which can cause significant heating. In a string of photovoltaic cells in a panel, if one cell is shaded the others will force current through it, which makes the cell heat up. This is causing significant decrease of the output and greatly reducing the lifespan of the panel. 

SCG: Can I use any soap or chemical to clean the solar modules? 

JK: There are several reasons why it is generally not recommended to use any chemicals to clean your panels. You can void the warranties that panel manufacturers provide, the chemicals can damage the sealant between the metal frame and glass and cause a corrosion of aluminum frames as well

SCG: How do I know my solar modules need to be cleaned?

JK:  Every solar owner should have a solar monitoring system, but if you don’t have it, use a visual check. If your panels are matte rather than shiny, then it’s time to clean them. I would highly recommend the use of a solar monitoring system.  All data is accessible from the computer or smart phone. The monitoring system provides instant information on the performance of the solar power system, inverters and individual solar panels. This is the best way to detect any underperformance problems. Issues can be efficiently diagnosed and resolved with minimum cost. 

SCG: How often and when should I clean my solar panels? 

JK:  It depends on the design and area where the solar installation is located. Residential solar modules we recommend to clean 1-2 times a year, commercial photovoltaic systems 2-3 times a year. The best months for first cleaning are March-May, second cleaning should follow between July-September.