Steve Williams, Managing Director, Clean Solar Solutions
Solar panels are generally self cleaning, but in dry areas or where panel tilt is minimal, dust and other substances accumulate over time and impact the amount of electricity generated by a module. This is where the need to clean solar panels arises.
We caught up with Clean Solar Solutions, Managing Director, Steve Williams, during his stay in Dubai, U.A.E. Steve is a global solar panel cleaning consultant, having written for many renewable energy magazines across the world and conducted world-first research into lichen growth on solar panels. He has also spoken at solar conferences across the world about solar panel cleaning, from Milan to Mexico. He is the chairman of the Rooftop O&M Working group for the U.K. Solar Trade Association. He created Clean Solar Solutions and turned them into an international, award-winning O&M company and was given an award in late-2019 and named U.K. Solar Industry Innovator of the Year.
What brings you to Dubai?
I have come to Dubai for a month to research the scale of the solar panel cleaning market here in the U.A.E. and to understand how we can address the challenges that desert solar panel cleaning can bring. We are actively seeking partners across the Middle East whom we can train for solar panel cleaning and expand our global reach.
Please explain why solar panel cleaning is important.
In more mature markets such as the U.K., solar panel cleaning is now firmly established as a core element of Operations & Maintenance (O&M) on a solar array. Soiling of all kinds accumulates on solar panels, from sand to traffic film, all of it reduces the output of the solar array and depending on soiling type, can create hotspots on the modules too. Hotspots are to be avoided as they not only reduce output, but can also cause permanent cell failure within modules.
What are the benefits of solar panel cleaning?
The benefits of solar panel cleaning are manifold. You increase output, which results in increased output and revenue. You also reduce hotspotting, which will maintain the life of the solar panels. In many cases, regular solar panel cleaning is required in order to maintain the terms of the Original Equipment Manufacturer’s (OEM) warranty.
What is the best way to clean solar panels?
There are multiple ways to clean solar panels, and each has advantages and drawbacks. Above all, your chosen cleaning method must maintain the terms of the OEM warranty. Water quality is also very important. Solar panels should be cleaned with ‘ultra-pure water’, meaning water that has been purified to a level of 10 parts per million (PPM) or less. This will leave a streak and spot-free finish on the solar panels. Cleaning with mains or tap water can result in streaky or spotty finishes, which result from mineral deposits being left on the glass after the water has dried. This is not providing a high-quality clean.
One method on small, residential systems is manual cleaning. This usually involves cleaning via telescopic water-fed poles. This can be the only effective way to clean small systems.
On utility-scale ground mounted solar farms, tractor cleaning has been the preferred method of cleaning. However, while the machines clean to a high standard and can clean a lot of modules per day, they can also damage the framework and solar modules if the tractor is not driven very carefully. Due to the weight of the tractors, they can also create soil compaction, which is not desired.
Robotic cleaning is fast becoming the accepted method of cleaning. Robots provide a lot of flexibility, being able to clean both ground, roof mounted and floating solar arrays of all sizes. It provides an even finish, whereas manual cleaning leaves room for human error. The robots do not create compaction, and it is very difficult to cause damage on a solar array with a solar panel cleaning robot. Technology is developing every year on solar panel cleaning robots and I believe that this will be the preferred method of solar panel cleaning in the long term.
How costly is solar panel cleaning?
Solar panel cleaning costs vary hugely from country to country and from site to site. However, there are some general rules of thumb. Firstly, ground mounted solar panel cleaning is cheaper than roof mounted cleaning and cleaning floating solar arrays is the most expensive. Secondly, the bigger the solar array, the cheaper the cost/KW or MW will become. Currently, the cheapest method of cleaning is tractor mounted cleaning, followed closely by robotic cleaning, with manual cleaning being the most expensive.
If we were looking to appoint a solar panel cleaning contractor, what should we look for?
Their approach to health & safety should always be the most important consideration. The contractor should be able to provide you with a detailed Risk Assessment & Method Statement (RAMS) which will highlight the risks of solar panel cleaning, including electrocution and explain how each risk will be mitigated and managed.
Next should be the equipment that they will be using. Any contractor looking to pressure wash the solar panels should not be used. Pressure washing invalidates very many OEM warranties, so should not be viewed as an acceptable cleaning method. Beyond this should be their reporting.