Prevention is better than a cure – the application of dust control in solar farm developments

Different forms of inhalable, respirable or nuisance dust can be generated from various natural and man-made sources. These sources vary from wind erosion, mining activities, stockpiles, industrial activities, haul mining and rural roads just to mention but a few. The dust produced from these activities can travel over long distances and one of the common sinks for transported fugitive dust are solar panels. However, in as much as transit of dust is a possibility in some instance’s activities within the vicinity of solar panels also contributes to the effect of dust on solar panels hence the conditions of dust deposition on solar panels depends on the nature of application the solar panels are utilized for. This then leads us to the most pertinent question in the context of our discussion, which is:

• What is the best method for managing dust and soil erosion for solar panels? 

Before the article gets into unpacking the answer, let’s also first cover some groundwork on:

• Solar panel technology – what are they and how do they work?  
• What are the different applications that utilize solar panels? 
• How does dust affect solar panel performance? 
• And to sum up – what can GRT do to reduce or eliminate dust in solar farms and thereby maximize their power generation? 

Consolidating all these important answers will build a better basis for the constitutive answer to the initial question posed. 

A bit of background…

Solar panels consist of an array of photovoltaic (PV) cells that convert sunlight into electricity through the photovoltaic effect. At the very least, two semi-conductive materials, such as silicon, with prerequisite of one having a positive charge while the other is negatively charged. Exposure to sunlight enables absorption of photons by the negative semiconductor atoms freeing electrons to flow back to the positive semiconductor. Individually, the solar cells are connected in series strings to build voltage whereas the strings connected in parallel build current.  Sealing or lamination occurs with eventual placing on a rigid frame making up the PV module or more commonly known as a solar panel. Solar panels are available in various sizes, power outputs, and materials and using the right conversion equipment enables power generated from solar panels to be used for almost any appliance that requires electrical power to operate. The timeline for utilization of solar energy in general spans across centuries. The incentive in use of solar energy is that it harnesses thermal energy carried by radiation for heating air and water in residential and industrial properties. In electricity production, they are many applications using solar energy and hybrid systems including solar chimney, concentrated solar power plants, and PV cells.

Mechanisms and impacts of dust deposition

The inherent material properties of the semiconductor determine the efficiency of the PV system. Transit of solar radiation through the atmosphere experiences interferences from pollutants such as dust and in the process scattered backward. The effects of scattering by dust decreases the direct component of solar radiation which increases the diffuse irradiance. The electrical behavior of PV modules depends on incident irradiance and when solar insolation on the panel surface decreases as result of dust, less power can be obtained which results in reduced efficiency. Size, geometry and chemistry of dust particles affect the performance of the solar panel. The mechanisms of soiling of the PV cell involve dry deposition where airborne particles are transported to the PV surface in the absence of water content. In wet deposition, atmospheric dust is contaminated with various forms of precipitations such as fog, rain and snow. The intermediate form of deposition between the two is known as shadow deposition which happens when clouds and fog containing water droplets are mixed with dust air before deposition. The factors influencing dust accumulation on a solar panel include; dust properties, surface property, local environment, wind, temperature and relative humidity, tilt angle and azimuthal orientation. The four primary soiling mechanisms of solar panels include cementation by water soluble salt, deposition of organic materials, surface tension and particle energetics. 

A focus on dust removal

Methods that have been used for dust control in solar panels include nightly stowage positioning which has been found to be very effective in protecting the mirrors during times when they are not in use. The most effective way of cleaning has been found to be washing using treated water sprays although the acrylic-protected surfaces are more difficult to clean than glass-face mirrors even when using the treated water sprays. Owing to dust retention on acrylic surfaces dust accumulation is much more rapid which is attributed to attractive forces and probably roughness. The degradation rates depend vastly on weather conditions for both glass and plastic surfaces. It has also been observed that surfaces in the dry climate demand more cleaning and maintenance to avoid substantial performance losses as there is no natural cleaning from precipitation. To categorize, the methods used to control dust in solar panels involve deterrence through keeping dirt from settling and adhering to surfaces, washing dirt with water or low surface energy detergent-type solutions before strong chemical and mechanical bonding can develop, cleaning through use of chemical or mechanically active techniques capable of breaking the chemical and mechanical bonds and surface modification achieved via treatments, coatings, films so that strong bonds cannot develop. Deterrence and surface modification are more preventative measures whereas washing and cleaning are more restorative measures. Effective cleaning solutions employ chemicals that possess attributes  ability to reduce surface tension, low cost in their solution volume, capability to be handled and mixed in automated equipment and non-toxicity, safety to the environment and biodegradability are preferred. 

Refocus – stopping dust and erosion at the source

The above methods of cleaning panels, or coating them to prevent dust or other deleterious materials bonding to them have been a big focus of solar panel management. This has even seen the rise of automated, robotic systems installed at great expense. It is our contention that a greater focus on dust prevention and erosion control should be taken. Due to the size of these installations, investment into concrete or traditionally sealed hardstands is rarely economically feasible. Many sites have then moved to a vegetated solution – which can be effective, however you get what you pay for. An effective vegetated solution needs investment into the soil, the right seed mix, fertilizers and a watering regime to establish. If on a slope, the treatment needs to be able to handle not just wind, but water erosion as well. As you can see from the images below, a sea of green grass can actually be hiding significant erosion problems – in this case leading to damage to solar infrastructure and parts of the farm going offline.

GRT has two key technologies proven to eliminate dust and erosion:

• GRT: Enviro-Binder – long-term, low-cost erosion control that can handle high rainfall impact and overland flow events. This is a proven technology across a wide range of industries with specific proven success in solar farms in the tropics. 
• GRT7000 – a clear drying polymer seal that 100% eliminates dust and erosion and can handle traffic, making it perfect for access/service roads. It also can provide a higher reflectivity result than exposed earth or vegetation – making it perfect for double-sided panel installations.

As opposed to vegetation, which can take months to fully establish, both of these products are 100% effective within hours of application.

Prevention is better than cure

The methods used for dust control in solar panels employ preventative and restorative measures on the solar panel surfaces. Employing both processes is critical to optimizing power production. Having a hard, dust repellent panel surface which less susceptible to embedding particles and their possible damage, smooth hence less likely to trap particles, hydrophobic hence inducing repulsion to ionic species, adsorption of solids and retention of water, lower surface energy therefore lower chemical reactions, chemically clean of water-soluble salts with the potential of combining with other soiling agents. Solar panels photovoltaic cells whether arranged in a series or in parallel have the sole intention of converting photochemical energy to electrical energy via the photovoltaic effect – dust impacts this efficiency significantly. As their use expands into base load power generation, whether for use in in mines, industry, or community supply dust affects their performance through soiling of the PV cells which can occur through dry, shadow and wet deposition. GRT’s proven technologies for dust and erosion control – even under heavy traffic, or on steep slopes, are perfectly suited to help optimize power generation.  

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REFERENCES 

• Chanchangi, Y.N., Ghosh, A., Sundaram, S., Mallick, T.K. 2020. Dust and PV Performance in Nigeria: A review. Renewable and Sustainable Energy Reviews. 121:109704. 1-14. 
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• Sarver, T., Al-Qaraghuli, A., and Kazmerski, L.L. 2013. A comprehensive review of the impact of dust on the use of solar energy: History, investigations, results, literature and mitigation approaches. 
• Syafiq, A., Pandey, A.K., Adzman, N.N., and Rahim, N.A. 2018. Advances in approaches and methods for self-cleaning of solar photovoltaic panels. Solar Energy. 162. 597-619. 
• Zaihidee, F.M., Mekhilef, S., Seyedmahmoudian, M., and Horan, B. 2016. Dust as an unalterable deteriorative factor affecting PV panel’s efficiency: Why and how. Renewable and Sustainable Energy Reviews. 65. 1267-1278.