This standard operating procedure (SOP) is based on general industry guidelines for cleaning photovoltaic modules, with specific attention to the requirements often specified for Trina Solar bifacial dual-glass modules

 

Based on typical photovoltaic (PV) module cleaning guidelines for anti-reflective coated glass, including recommendations often cited for high-quality modules like those from Trina Solar, the following water quality standards should be met to prevent damage and optimize performance. 

Recommended Water Quality Parameters

 pH Range: 5.0 – 7.0 (Note: Some guidelines accept slightly broader ranges of 6.5–8.5, but lower, near-neutral, or slightly acidic water is safer for coated glass to prevent scaling).

Total Dissolved Solids (TDS): \ 1000 mg/L. For optimal results, lower is better (e.g., \(<30\) mg/L) to prevent mineral deposits.

Water Hardness (Calcium & Magnesium ions): 0 – 40 mg/L (soft water).

Chloride/Salinity: 0 – 3,000 mg/L.

Turbidity: 0 – 30 NTU. 

 Cleaning Requirements Water Type: Non-alkaline water must be used. Demineralized or Reverse Osmosis (RO) water is highly recommended to avoid residues.Hard Water Caution: Use of hard water (\(>75\) mg/L - \(180\) mg/L) is prohibited on Anti-Reflective Coated (ARC) modules as it can cause scaling, which reduces efficiency.Water Pressure: Maximum water pressure at the nozzle should not exceed 4 MPa (40 bar).Water Temperature: The temperature of the water should be close to the ambient temperature of the panel to avoid thermal shock.Cleaning Time: Early morning or late afternoon (dusk/dawn) when panels are cool.Avoid: Do not use alkaline or strong acid solvents.  — Water quality: The quality of water is crucial when cleaning solar modules. High mineral content water may cause mineral deposits on the glass surface, reducing. 

This standard operating procedure (SOP) is based on general industry guidelines for cleaning photovoltaic modules, with specific attention to the requirements often specified for Trina Solar bifacial dual-glass modules.

1. Pre-Cleaning Preparation

Time of Day: Clean only during low-light conditions (early morning, evening, or overcast days) to avoid high electricity generation (safety) and to prevent thermal shock.

Personnel Safety: Wear personal protective equipment (PPE), including insulated gloves and safety glasses.

System Status: Turn off the PV system before beginning the cleaning process.

Do Not Walk/Stand on Modules: Do not stand, step, or sit on the modules to avoid breaking the glass, especially with delicate dual-glass bifacial modules.

2. Water Quality Requirements

Using improper water can cause mineral deposits (scaling) or scratch the Anti-Reflective Coating (ARC) on the glass. 

Preferred Water Type: Reverse osmosis (RO) water or deionized water.

Alternative: Clean rainwater or tap water with low mineral content (Total Hardness < 75 mg/L or < 60 mg/L).

Total Dissolved Solids (TDS): Should be less than 400 mg/L (some guidelines suggest < 30mg/L).

pH Level: 6.5 to 7.5 (near neutral).

Forbidden: Do not use high-pressure, hard water, or water containing harsh chemicals (acids, alkalis, acetone).

3. Module Temperature and Thermal Shock Prevention

Temperature Differential: The water temperature must be similar to the module temperature at the time of cleaning.

Maximum Difference: The water should not be more than 20°C warmer or colder than the module surface temperature to avoid breaking the glass due to thermal shock.

Avoid Hot Panels: Do not spray cold water on hot, sun-exposed panels. 

4. Wet Cleaning Method (Step-by-Step)

Remove Loose Dirt: Use a low-pressure water spray to remove dust and loose dirt.

Apply Water/Detergent: If stubborn dirt remains, use water mixed with a mild, non-abrasive detergent or, preferably, just water.

Scrubbing: Use a soft-bristled brush, sponge, or soft microfiber cloth to clean the surface.

Cleaning Direction: Start from the top row and work downwards.

Stubborn Stains: Soak the stain rather than scrubbing harshly to avoid damaging the Anti-Reflective Coating (ARC).

Backside Cleaning: For bifacial modules, the back glass should be cleaned using the same gentle methods to maintain high energy yields.

Rinse: Rinse the modules thoroughly with plenty of water.

Drying: Use a squeegee or lint-free cloth to remove excess water and prevent streak/spotting. 

5. Water Pressure

Maximum Pressure: Water pressure should not exceed 35 bar (or 4 MPa) at the nozzle.

Equipment: Use a soft nozzle or low-pressure spray attachment. 

6. Post-Cleaning

Inspection: Inspect modules for cracks, scratches, or damage.

Documentation: Record the cleaning date, water type used, and any noted damage.