Hydrophobic–Hydrophilic Surfaces Exhibiting Dropwise Condensation for Anti-Soiling Applications

Soiling of solar cover glass is a significant challenge that increases the levelized cost of electricity of solar photovoltaic energy through loss of electrical output and/or increased operation and maintenance costs. Hydrophobic coatings can reduce the cost of cleaning, but an external source of cleaning water is still required. Dew, however, can be harnessed to create a self-cleaning glass surface. To efficiently use condensation (i.e., natural dew) to create a self-cleaning glass surface, we fabricated a hybrid hydrophobic-hydrophilic coating, with an array of isolated hydrophilic circular rings. Water roll-off collection rates were measured in a simulated dew environment. The effect of hydrophilic ring geometry (location, arrangement, diameter, distance, and count) was studied to determine the optimal cleaning efficiency. The hybrid surface increased water collection rates by 95% over an uncoated (bare) glass surface and 51% compared with uniformly coated hydrophobic low-iron glass.