When maintaining polycrystalline solar panels, water quality isn’t just an afterthought—it’s a critical factor that directly impacts performance and longevity. Total Dissolved Solids (TDS) in cleaning water can make or break your maintenance routine. Let’s break down what you need to know.
First, TDS refers to inorganic salts, minerals, and organic matter dissolved in water, measured in parts per million (ppm). High TDS levels leave behind mineral deposits after evaporation, creating stubborn streaks or films on panel surfaces. These residues reduce light transmission, leading to efficiency losses that compound over time. For polycrystalline panels, which rely on uniform light absorption across their silicon crystals, even minor shading or surface contamination can disproportionately affect output.
Industry standards recommend using water with a TDS level **below 50 ppm** for routine cleaning. This threshold minimizes mineral buildup while balancing practicality—ultra-pure water (0-10 ppm) isn’t always feasible for large-scale installations. In regions with hard water (TDS exceeding 150 ppm), untreated water is a hard no. For example, calcium carbonate deposits from hard water require acidic solutions for removal, which can degrade anti-reflective coatings if used repeatedly.
To achieve optimal TDS levels, many operators use reverse osmosis (RO) systems or deionized (DI) water. RO systems reduce TDS by 90-99%, depending on feedwater quality, while DI systems use ion-exchange resins to strip minerals completely. However, both methods require infrastructure investments. A cost-effective alternative is blending tap water with purified water to hit the 50 ppm sweet spot.
Here’s where it gets technical: The relationship between TDS and cleaning frequency isn’t linear. In arid environments with frequent dust storms, panels may need biweekly cleaning. If your water’s TDS is 100 ppm, you’d risk accelerated mineral buildup, forcing you to either increase water purity or shorten cleaning intervals. Field studies from solar farms in Arizona showed that using 75 ppm water instead of 30 ppm water led to a 2.1% annual efficiency drop—a significant margin in utility-scale projects.
Some installers overlook pH balance, but it’s equally crucial. Water with a pH outside 6-8 can corrode aluminum frames or react with panel surfaces. Pair low-TDS water with a neutral pH to avoid chemical reactions that weaken structural components.
For installations near coastal areas, salt deposition adds another layer of complexity. Seawater has a TDS of ~35,000 ppm, so even airborne salt particles can spike local water TDS. In these cases, combining low-TDS water with soft-bristle brushes prevents micro-scratches that trap contaminants.
Maintenance teams should test water quality quarterly using handheld TDS meters—a $50 tool that pays for itself in avoided downtime. If readings creep above 50 ppm, recalibrate your filtration system. For polycrystalline solar panels, manufacturers often specify TDS limits in their warranties. Ignoring these could void coverage for surface damage.
One pro tip: After cleaning, inspect panels under angled sunlight. Mineral streaks become visible when light reflects off residues—a simple quality check that avoids costly energy audits.
In summary, TDS isn’t just a number on a lab report. It’s a variable you control to maximize ROI. Stick to sub-50 ppm water, monitor pH, and adapt to local conditions. Your panels—and your energy bill—will thank you.