Cleaning PV Cells

When it comes to cleaning your photovoltaic system, the “why” is easy. Anything that blocks sunlight from the panel is reducing the effectiveness of the photovoltaic system. Dimming of light through dust or other agents like tree sap, bird droppings, or environmental pollutants, will result in a decrease in energy production. The sun shines bright in Hawaii – but it can’t shine through dirt. Some sources indicate that a diffuse layer of dust can actually reduce solar absorption by 5%. Opaque pollutants like sap, droppings, or leaves which fall and adhere to the panels can reduce absorption by even more. It’s easy to imagine how much when you realize that a cloudy, stormy sky can reduce solar uptake by 50%. Dirt that blocks all light in segments of the panel could have an even more significant effect. 

The answer to all of this is simple, of course. Keep your system clean, and keep it operating at maximum efficiency. But how is this accomplished? No one wants the cleaning of a solar installation to be a “hidden cost” of ownership, so understanding the cleaning requirements up-front can go a long way toward planning the cost effectiveness of a PV installation.

First, the natural approach. Researchers at Stanford have determined that in any environment in which a moderately heavy rainfall occurs at intervals of less than 12 days, the cells will usually lose no more than 3% power to detritus and solar obfuscation. Of course, there are several problems with this ideal, experimental scenario. Rainfall may not occur so frequently. If it does, it may carry with it a large quantity of dust and pollutants. Fortunately in Hawaii, most areas of the state get some level of frequent heavy rainfall, and the air in the middle of the Pacific tends to be free and clear of a lot of the dust and other particulates that occur in high solar areas of the mainland like the desert southwest. In some parts of the country, rain will contain pollen, dust, and other particulate matter which will actually accumulate on the panels. Finally, even if the rain is clean and occurs at regular intervals, a 3% drop in production capacity is, after all, wasted money. This may be unacceptable for solar owner owners seeking peak efficiency. We are lucky enough in Hawaii to have regular strong rainstorms of the sort that provides a fairly optimal natural cleaning pattern. However, it may still be a good idea to give Mother Nature a little help now and then.

This is where cleaning systems come in. Some products such as “SolarWash” by OCS Energy provide a computer-controlled automated shower for solar panels. Similarly, the “Automatic Solar Panel Cleaning System” by Heliotex provides a hands-free option for simulating the cleaning effects of rain on dusty panels. Both of the previous mentioned products are designed more for large scale commercial installations and low rain environments. Another product that has more of a residential application is the solar panel cleaning system by ProCurve Solar. It’s basically an extendable-handle manual soft brush and cleaning squeegee. It connects to a garden hose and delivers clean water directly to the area being cleaned. Of course, a cleaning system would defeat the purpose of living “green” if it were wasteful, and so each of these systems utilizes some form of water reclamation so that it is as ecologically friendly as the PV system itself.

No matter what cleaning system you choose for your Hawaii solar installation, be sure to use a mechanism or process that will avoid scratching the panel glass, and be sure that you never step on the panels while trying to clean them. Beyond that, whether you choose a system with computer automation or a bucket and a brush, the important thing is that the panels operate at peak efficiency. A clean panel is a happy panel!