Field Test Setup for Hydrophobic Coatings and their Analysis in the Macro- and Nanoscale

Abstract

One of the major drawbacks of solar power plants in humid and desert regions is the water needed for cleaning the solar panels or mirrors. By reducing the amount of water consumed during the cleaning process of solar power plants, their efficiency can be increased. Several so called self-cleaning coatings are available in the market today [1]. Hydrophobic coatings use the lotus effect and do not need any activation energy. The lotus effect consists of forming a droplet in the presence of sufficient water. This droplet picks up the dust as it rolls down a tilted surface [2]. In addition, due to an inhibition of water adsorption, the adhesion force between hydrophobic surfaces and the accumulated dust is lower when the former are functionalized [3]. In this thesis a hydrophobic coating is investigated in terms of its functionality in reducing the dust accumulation and the amount of water needed to clean it. Here, a field test setup for coated photovoltaic panels is proposed were the power output of the panels is compared, and related to, the functionality of the coating. A DC/DC maximum power point tracker including a data logger is developed for the field test of the photovoltaic panels. The coating is also characterized by using contact angle measurements, transmittance tests, ultraviolet-visible spectroscopy (UV-Vis) and atomic force microscopy (AFM). A detailed description of the experiments and the maximum power point tracker is given. The most general outcome of this work is that the hydrophobicity of the surface has no apparent effect on the amount of dust accumulation. The lack of rain in the region implies that self-cleaning methods are not suitable here. Furthermore, the dew accumulating in the morning is too little to sufficiently clean the surface with the rolling effect. If the coating is clean it shows some anti-reflective behavior. Atomic force microscopy roughness measurements indicate that the coating is very smooth in the nanoscale and, therefore, that hydrophobicity is related to chemical composition, i.e. reduced free energy of the surface, in this case rather than to roughness or morphological and topological heterogeneity.

Date of Award	2013
Original language	American English
Supervisor	Matteo Chiesa (Supervisor)