Hydrophilic Nano-coating based on Waterborne Polyurethane & Oxidized Graphene Nanoplatelets for Solar Panel Application
Malaysia has great potential transition from fossil fuel to low-carbon substitutes by converting solar radiation into direct current using photovoltaic panels. However, efficiency of solar panel is known to decrease due to dust accumulation, resulting in an average of 20% energy efficiency. Studies have shown that dust deposition reduces glass cover transmittance causing decreased power output and amount of solar irradiation reaching the cell. Incorporation of oxidized graphene nanoplatelets (GNP) into waterborne polyurethane (WPU) as adhesive layer was proposed to fabricate hydrophilic-nanocoating and minimize dust accumulation. However, the optimal weight percentage of GNP to be incorporated into WPU coating to result in the film’s maximum wettability and transparency characteristics, is unknown. This study will utilize casting method to prepare WPU/GNP coating film samples, where 0-0.025 wt% of oxidized GNP will be dripped into 100 ml of WPU aqueous solution, stirred mechanically, poured onto release paper and dried overnight. The effect of incorporation of oxidized GNP into WPU on wettability and surface energy, surface roughness, conductivity, transparency, chemical resistance, chemical bonding and thermal stability of fabricated film will be analyzed. The contact angle (CA), wettability and film’s hydrophilicity characterization unit, will be measured using CA goniometer, with probe liquid (redistilled water, glycerol and diiodomethane) deposited onto surface. The surface energy will be calculated using Fowkes, Owens and Wendt equations. Furthermore, film’s electrical resistance will be measured using a four-point probe meter, while each sample’s conductivity will be calculated as a ratio of film’s thickness over resistance and film’s area. Atomic Force Microscope will be used to characterize the topography and dispersion of GNP on film’s surface, while film’s transparency, transmission and absolute reflection parameters will be analyzed using an UV-Visible spectrophotometer. Chemical immersion contact test will be further conducted, where film’s resistance to chemical attacks (i.e. acid rain) will be evaluated using sulfuric acid and sodium hydroxide respective reagents. Moreover, Fourier Transform Infrared Spectroscopy in wavelength region of 525-4000 cm-1 will be used to identify the functional groups and chemical bonding on film’s surface. Lastly, film’s thermal stability will be studied using Thermogravimetric analyzer at 25-800℃. The contact angle is expected to be less than 90o due to hydrophilic properties of the WPU compound. In addition, the WPU/GNP coating is expected to have high surface energy due to strong WPU-GNP molecular attraction and low surface tension. Film’s inter-particle gaps are expected not to be filled by excess of oxidized GNP, resulting in smooth (planed) surface. Fabricated film is expected to be able to conduct electricity to PV cell and create electric field to convert solar energy into electricity due to incorporation with oxidized GNP. Furthermore, even dispersion of GNP in WPU film and no oxidized functionate groups are expected to be present on the coating’s surface. Also, film is expected to have maximum transmission due to high crosslinking density of film. The nano-coating with improved barrier properties, preventing chemical attacks, is expected to be fabricated. Thermal stability is expected to reach optimum point with 0.015 wt% of GNP incorporation due to higher initial degradation temperature of GNP compared to WPU. Lastly, it is expected that 0.025 wt% of oxidized GNP will lead to higher collision frequency between particles, reducing light absorption. Hence, the optimum GNP concentration to perform stable oxidized GNP dispersion, water contact angle of less than 90° and increased sunlight absorption of the solar panel, is expected to be achieved at 0.015-0.020 wt% oxidized GNP loading.