Ultrapure Water Use in Solar Cell Manufacturing: Rinse Water per Wafer

… more less Ultrapure water use in solar cell manufacturing is mostly rinse water. After every wet step, such as cleaning, texturing and HF etching, wafers are rinsed. A trace of salt or metal left on the surface would trap charge and lower cell output. So the rinse water must be far purer than tap water. Plants make it in stages. Reverse osmosis pushes water through a membrane that holds back most salts. Ion exchange resins then swap any leftover ions. Ultraviolet light and fine filters remove organic matter and particles. Purity is often checked as electrical resistivity, since pure water conducts very poorly. Making this water uses power and chemicals, and the resins are cleaned with acid and base, adding to the waste stream. A cell plant can draw a large volume each day. In dry regions that competes with farms and towns. Plants cut demand by recycling lightly used rinse water, by rinsing in several stages so the cleanest water is used last, and by moving some steps to dry processes. The trade-off is that recycled water needs more treatment. After this Concept you can explain why cell factories need ultrapure water and judge a water figure in a panel's environmental declaration.