7 October 2014 Optical and adhesive properties of dust deposits on solar mirrors and their effects on specular reflectivity and electrodynamic cleaning for mitigating energy-yield loss
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Abstract
Large-scale solar plants are mostly installed in semi-arid and desert areas. In those areas, dust layer buildup on solar collectors becomes a major cause for energy yield loss. Development of transparent electrodynamic screens (EDS) and their applications for self-cleaning operation of solar mirrors are presented with a primary focus on the removal dust particles smaller than 30 µm in diameter while maintaining specular reflection efficiency < 90%. An EDS consists of thin rectangular array of parallel transparent conducting electrodes deposited on a transparent dielectric surface. The electrodes are insulated from each other and are embedded within a thin transparent dielectric film. The electrodes are activated using three-phase high-voltage pulses at low current (< 1 mA/m2 ). The three-phase electric field charges the deposited particles, lifts them form the substrate by electrostatic forces and propels the dust layer off of the collector’s surface by a traveling wave. The cleaning process takes less than 2 minutes; needs energy less than 1 Wh/m2 without requiring any water or manual labor. The reflection efficiency can be restored > 95% of the original clean-mirror efficiency. We briefly present (1) loss of specular reflection efficiency as a function of particle size distribution of deposited dust, and (2) the effects of the electrode design and materials used for minimizing initial loss of specular reflectivity in producing EDS-integrated solar mirrors. Optimization of EDS by using a figure of merit defined by the ratio of dust removal efficiency to the initial loss of specular reflection efficiency is discussed.
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Malay Mazumder, Julius Yellowhair, Jeremy Stark, Calvin Heiling, John Hudelson, Fang Hao, Hannah Gibson, Mark Horenstein, "Optical and adhesive properties of dust deposits on solar mirrors and their effects on specular reflectivity and electrodynamic cleaning for mitigating energy-yield loss", Proc. SPIE 9175, High and Low Concentrator Systems for Solar Energy Applications IX, 91750K (7 October 2014); doi: 10.1117/12.2066328; https://doi.org/10.1117/12.2066328
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