Optical and adhesive properties of dust deposits on solar mirrors and their effects on specular reflectivity and electrodynamic cleaning for mitigating energy-yield loss
2014
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 ( 2
). 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/m 2 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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