Page 49 - Energize October 2021

TECHNICAL

affect the panel in several ways: in large installations the decision Cleaning methods
to clean is taken by comparing the cost of cleaning with the value For rooftop PV systems there are two common methods, manual
of lost energy. cleaning and mechanical cleaning. Robots and other automatic devices
are more commonly used on large utility scale groundmount systems.
The purpose of cleaning is to remove accumulated dirt, without There are a variety of manual solar panel cleaning systems available
damaging or otherwise affecting the panel. Cleaning operations can in South Africa; most consist of water-fed fixed or rotating brushes
affect the panel in several ways: attached to the end of extendable poles.
• Physical damage to the panel Mechanical systems are available for cleaning panels, but the shape
• Retention of cleaning material residue, which can stick to glass and and pitch of many roofs and the irregular PV structure excludes their
be difficult to remove. use. These systems are not permanently attached to the structure,
• Build-up of waterborne grime at the edge of the frame whereas automatic systems are a feature of the systems. Mechanical
• Damage due to temperature difference between panel and systems need to be tethered to the mounting structure and operate
cleansing medium under remote control and require the attention of an operator. n

Airborne and waterborne (rain) pollutants in urban areas consist References
mainly of dust. 1. K Naicker: “Investigating the operations and maintenance strategy of
Common practice now is for RTP to be installed on factory rooftops solar photovoltaic plants in South Africa”, MBA dissertation. May 2018.
in industrial areas and mining plant, which means they are exposed 2. J Gallon, et al: “PV Module hotspot detection”, NREL.
to a higher concentration of airborne pollutants which are more 3. JA Solar: “How to clean your PV solar panels”, ESI Africa, February 2021.
problematic than simple dust. Rain has a cleansing effect, but raindrops 4. S Ansari, et al: “A review of Monitoring Technologies for Solar PV
can also contain dissolved pollutants, dust and other grime. Systems Using Data Processing Modules and Transmission Protocols:
Concentrated pollution, due to avian, animal or insect causes, is a Progress, Challenges and Prospects”, Sustainability 2021, 13, 8120.
more serious problem, as it not only affects the output of the panel but
can result in the formation of hotspots which can damage the panel. Send your comments to rogerl@nowmedia.co.za

(a)

(b)
Figure 9: (a) The pitch and the shape of some rooftops makes cleaning difficult, while regularly shaped arrays (b) favour mechanical cleaning (Author)

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