As the solar panel cleaning industry progresses in the UK, we are occasionally presented with a new challenge that not many people saw coming. One that has become more prevalent during 2017 and that will present nightmares to many solar panel owners in 2018 is lichen (pronounced 'Li-Ken') growth. As more and more solar panels all over the UK are being blighted by this growth, how to remove lichen from solar panels is becoming discussed more.
Clean Solar Solutions Managing Director Steve Williams is Europe's foremost expert on lichen growth on solar panels. He has engaged in reserach on this subject for four years and has released a document explaining in some detail why lichen grows on solar panels. Below is a summary of his work, but you can read his published document in full here: Eutrophication & Lichen Growth On U.K. Solar Panels
Why Does Lichen Grow On Solar Panels?
Finding out why lichen grows on solar panels is a good place to start. Lichen is an organism that is different from algae, but arises from algal growth. Algal growth starts off on a microscopic level and only becomes visible to the naked eye when it is present in great volume. It is the green line that we frequently see along the bottom edge of solar panels. By the time we see that green line, conditions are ripe for lichen to grow. Lichen lives alongside algae in a symbiotic relationship.
Lichens are not plants and do not need a continuous flow of water to survive like other plants. Because of this they can grow in locations impossible for most plants, such as bare rock, sterile soil or sand, and various artificial structures such as walls, roofs, monuments and even the glass of solar panels. They grow their own food via photosynthesis and this explains why they can grow on the glass of solar panels in the first place.
Lichen growth on solar panels was likely not a consideration of many panel manufacturers and even more likely was not a consideration of installers when deciding where to put solar panels. There is an ongoing lichen growth problem on Mount Rushmore National Memorial that requires the employment of mountain-climbing conservators to clean the monument. Likewise, it seem that now we have a similar battle to wage against lichen growth on solar panels in the UK.
The lichen that you see in the picture below has 3 layers. The top layer is visible, the bottom layer forms a crust that strongly adheres to the substrate (soil, rock, tree bark, etc.), making separation from the substrate impossible without destruction. Like much organic matter, the growth is accelerated in sunny, warm, wet conditions and solar panels in the UK provide such an environment.
A major ecophysiological advantage of lichens is that they are poikilohydric, meaning that though they have little control over the status of their hydration. They can tolerate irregular and extended periods of severe desiccation. Those of you hoping that the lichen will dry out and fall off the solar panels will be severely disappointed. Upon desiccation, lichens enter a metabolic suspension or stasis (known as cryptobiosis) in which the cells of the lichen symbionts are dehydrated to a degree that halts most biochemical activity. In this cryptobiotic state, lichens can survive wider extremes of temperature, radiation and drought in the harsh environments they often inhabit. Put simply, lichen will survive extreme cold and extreme dryness and start growing again when either the temperature increases or within a few minutes of raining again.
Why Is Lichen Growing On Solar Panels a Problem?
There are over 28,000 lichens worldwide, 2,000 of which are in the UK! Clean Solar Solutions have observed 2 growth types of lichen growing on solar panels. The 2 types we have seen have a growth rate of between 2mm – 4mm per lichen growth, per year. While this may not sound much, when you have an infestation of hundreds of lichen growths on your solar panels, they can quickly start to create hard shading on the solar panels. This will have the effect of both reducing output and creating damaging hotspots on the solar panels. Surface area also influences photosynthetic rates, so the more lichen you have, the quicker it will grow. So prevention rather than cure is very much the key.
Can Lichen Be Prevented From Growing On Solar Panels?
Yes. Lichen growing on solar panels needs the symbiotic relationship that it enjoys will algae. Take away the algae and lichen does not have the chance to grow. Algae on solar panels is not given the opportunity to grow if the solar panels are not cleaned regularly. As mentioned earlier, when the thick green line of algae is along the bottom edge of the panels, then conditions are ripe for lichen growth, as illustrated in this picture.
By removing the algae from solar panels, you are removing the symbiotic partner needed for the lichen to grow.
Can Lichen Be Removed From Solar Panels?
Yes, but removing lichen from solar panel is not a straightforward as one might think. Glass may feel very smooth to touch, but is in fact, pitted and very rough when put under a microscope. Lichen makes the most of this and attaches itself into the pits in the glass. Because of the way it forms a strong bond with the glass, conventional panel cleaning methods, both manual and machine, do not remove lichen. The only way to remove lichen, as mentioned earlier, is by total destruction, be that removing the lichen by hand or by chemical.
Clean Solar Solutions are able to provide both solutions at utility ground mount scale, residential rooftop scale and everything in-between. We have a lichen removal chemical, designed by American chemists, specifically for removing build-up of lichen and bird droppings from solar panels and this has been approved for use by a number of solar panel manufacturers, including Solarworld and Canadian Solar. If chemical removal is not your preferred method, it may be that we need to remove the lichen by hand. This is the most labour-intensive option and as a result, is the most expensive.
- Lichen will grow on solar panels if left uncleaned
- Lichen binds strongly to the glass and total destruction of the lichen is the only cure
- Preventing lichen growth is better and more cost effective than trying to remove lichen once it has set in
- Removing lichen can be a time consuming and costly process
For the purpose of this article, we have kept our explanations of lichen relatively straightforward, but we are able to speak about lichen more in depth from a scientific viewpoint if needed. Regardless of your level or need for knowledge, Clean Solar Solutions are happy to provide advice to you about how to remove lichen growing on your solar panels. Please feel free to contact us.