Deciding the exact time to clean the photovoltaic modules at a medium- or large-scale power plant (utility-scale) is an operational management decision that aims to optimize the balance between maintenance costs (OPEX) and the financial return on generation (ROI).
Cleaning too early generates unnecessary costs; delaying cleaning compromises the plant’s revenue. So, how do you make the best decision? Below, we present a practical guide to help guide decision-making in the field.
1. Ideal Cleaning Frequency by Climate and Land Use
Since dirt accumulation depends directly on the environment surrounding the plant, the maintenance schedule should be adjusted according to the region’s rainfall patterns, relative humidity, and sources of contamination:
Semi-arid and Northeastern Regions (Water Stress and Mineral Dust):
Recommended frequency:3 to 4 times a year (concentrated during the dry season).Dynamics:High rate of fine, dry mineral dust deposition.
Agricultural Regions (Central-West and Inland Southeast):
Recommended frequency:2 to 4 times a year (synchronized with the agricultural calendar for soil preparation, planting, and harvesting).
Dynamics:Heavy organic dust and soot from seasonal burning.
Coastal Regions:
Recommended frequency:2 to 3 times a year.
Dynamics:Constant deposition of salt spray (sea mist) mixed with sand, forming a hygroscopic crust on the surface.
Urban and Industrial Regions:
Recommended frequency:1 to 2 times a year.
Mechanism:Deposition of fine particulate matter, combustion soot, and greasy/oily residues.
Humid Regions with Regular Rainfall (South and Southeast):
Recommended frequency:Once a year (or via predictive maintenance).
Dynamics:Rain washes away surface dust, requiring intervention focused on edges and localized accumulations.
2. Decision Checklist: When to Take Action?
Instead of simply following fixed dates on the calendar, the decision to call in the cleaning team should follow this analysis process:
1. Metrological and Analytics Assessment (DATA)
[ ] Has the plant’s Performance Ratio (PR) dropped by more than5% to 8%compared to the theoretical model under the same irradiance?
[ ] Does the financial calculation of the energy that was not generated exceed the total cost of the cleaning operation?
2. Technical Inspection and Thermography
[ ] Does the module show a continuous buildup of dirt on the lower frame (frame) covering the photovoltaic cells along the edge?
[ ] Is there a confirmed presence of concentrated pockets of dirt (such as bird droppings or organic stains)?
[ ] Did the thermographic inspection (via drone or manually) identify critical temperature variations (sharp temperature differences) on the surface of the cells?
3. Climate Opportunity Cost Analysis
[ ] Does the weather forecast indicate no heavy rainfall (exceeding ) for the next 10 to 15 days?
[ ] Is the plant operating during a favorable rate period, in which maximum generation capacity is critical for revenue?
3. Technical Implementation Guidelines
When determining whether the panels need to be washed, the following technical standards must be followed to preserve the integrity of the equipment:
Thermal Equilibrium (Prevention of Thermal Shock):Cleaning must take place exclusively in the early morning or late afternoon, when the glass surface is cool (< 40°C), to avoid the risk of microcracks and breakage due to thermal stress.
Water Parameters:When washing with water, use water with a neutral pH (6.5 to 7.5) and a low concentration of total dissolved solids (TDS < 200 ppm) to prevent mineral deposits (such as lime scale) on the glass.
Operational Sustainability:In line with ESG practices, prioritize automated technologies, dry robotics, and sustainable surface protection solutions to reduce the need for frequent maintenance.
📌See also:Want to understand the biological and physical causes behind efficiency loss in power plants?Read our full article:Soiling: The Silent Pathology That Threatens Photovoltaic Efficiency.