The soiling of solar photovoltaic systems from dust and snow could lead to a loss of €4-7 ($4.3-7.6 billion) in 2023 which is equivalent to a 4-5% loss in energy production worldwide, a technical report by the International Energy Agency (IEA) said.

The report elaborated on the leading factors in efficiency losses due to soiling and proposed measures that can be employed during and after the installation of solar systems to minimize the impact of dust.

The report said that more PV modules are installed in high-insolation regions, such as China or India, which are also more exposed to soiling.

Further, the lower tariff in many areas does not provide any incentives for developers to spend capital on cleaning the solar modules.

“And, lastly, under identical soiling conditions, more efficient modules are subject to larger energy losses compared to less efficient PV modules,” the report said.

The IEA report identified that the extent and nature of soiling are highly variable and depend on various factors including the climate.

Moreover, soiling does not always occur homogeneously over the whole module surface or plant and tends to accumulate in the lower parts of modules.

“If soiling is not distributed uniformly, the short circuit current measurements may underestimate the actual impact of soiling on PV power,” the report said.

It added that mitigating the losses due to soiling can be classified into preventive and corrective measures.

Preventive measures fall into the responsibility of engineering, procurement, and construction, in terms of site and module selection, anti-soiling coating applications, and site adaption.

Corrective measures fall into the competence of operations and maintenance such as choosing the right cleaning technology.

Fig: Illustration of soiling mitigation technologies.

Source: IEA

Under the preventive measures, site planning for the PV system becomes crucial. Knowledge about local meteorological conditions like main wind direction, rain frequencies, relative humidity, and dew occurrence will help in adapting systems to minimize soiling.

“For example, nearby dirt roads can be lined with vegetation to deflect dust gusts. Frameless modules may make it easier for soiling to be removed, and an optimized module design with bypass diodes can minimize the effect of partial shading by heterogenous soiling,” the report said.

Further, anti-soiling coating of various types such as hydrophobic, hydrophilic, or photocatalytic can help in cutting down soiling-induced efficiency losses.

Anti-soiling coating aid natural processes like rain and dew in cleaning the systems. However, the advantage is contingent on the type of coating most suitable for extant local conditions.

Additionally, experiments have shown that maneuvering the tilt angle of the PV modules depending on whether they are bifacial or monofacial can also reduce their ability to attract dust.

On the prevention of soiling, the study elaborated on various types of cleaning methods. The summary is the chart below:

Fig: Proposed PV cleaning techniques based on weather conditions

Source: IEA

Additionally, the report said that the solar power industry needs a more cost-efficient, fully automated, water-saving, and time-saving solution to clean dust and sand off PV panels.

It added that the Electrodynamic Cleaning System (EDS) is a promising technology that fits the bill for cleaning dust off solar panels, solar reflectors (mirrors), and glass surfaces, especially in arid regions.

The EDS consists of a contactless cleaning solution using an electrodynamic cleaning based on the charging of sand particles. Dust particles are evacuated from the module surface via traveling waves controlled by high voltage (in the order of kV) electric pulses applied in dedicated electrodes integrated below the front glass of the solar panel.

The market for robotic cleaning of solar modules has been growing in India as it has proved to be effective in increasing yield and cutting O&M costs.

In a recent interview, Nalin Kumar Sharma, the President of Ecoppia for the Asia-Middle East & Pacific regions, said robotic cleaning of modules can increase generation by up to 5% a year.