Augmented performance of solar desalination unit by utilization of nano-silicon coated glass cover for promoting drop-wise condensation

Solar energy based desalination using solar still is considered as the low-cost efficient method for achieving clean water and the condensation behavior of the still glass cover plays an important role in augmenting the yield. This study aims to improve the water yield and thermal performance of solar still by changing the glass cover wettability using nano-silicon coating through spray technique. Transmission Electron Microscopy image revealed that silicon particles are interconnected and creates a nano-network like structure, whereas the surface area of 45.37 m²/g was exhibited by silicon, signifying its mesoporosity nature. The results showed that the silicon coating changed the condensation behavior of glass cover from film-wise to drop-wise, which augmented the water yield of coated glass solar still by 15.6% as compared to bare glass solar still. Coating durability and ageing analyses revealed marginal reduction in performance and water contact angle of coated solar still even after 100 working days, signifying the durability of coating. The evaporation efficiency of coated glass solar still was 3.6% higher than the bare glass still, owing to the higher heat transfer achieved through drop-wise condensation. Cost analysis of coated solar still revealed freshwater cost per liter of 0.013 US $ with pay-back time of 88 days. Moreover, the water quality analysis of the desalinated water demonstrated excellent quality that is highly suitable for drinking purpose. It is concluded that low-cost and prolonged durability of nano-silicon coating would be highly beneficial in augmenting the overall performance of the solar desalination unit.