Optimization of optical performance and dust removal efficiency of electrodynamic screen (EDS) films for improving energy-yield of solar collectors
Rabi Bernard, Annie Arokiaselvi
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In 2018 alone, the global energy demand grew by 2.3% and will rise by 1.3% each year to 2040  making it the fastest growth rate in the last decade predominantly driven by a robust global economy and increased heating and cooling needs. This tremendous need resulted in using fossil fuels to meet nearly 70% of the growth, but also promoted solar and wind generation to have a double-digit growth pace, with solar alone increasing by 31%. Terrestrial solar energy at AM1.5 is generally given at 1kW/m2, which is a vast free source of energy that can be harvested to meet the global demand for electricity . A major obstacle for large scale solar power production is obscuration of sunlight on solar collectors caused by dust deposition or ‘soiling’ as the power plants are located in semi-arid or desert regions. Soiling could result in energy-yield output losses of about a third of the total power output of the installation  as water is a scarce commodity, resulting in lesser cleaning cycles of the solar collectors. Electrodynamic Screen (EDS) films can restore the efficiency of solar power installations without the use of water, manual labor or robots and can be retrofitted onto the sun facing surfaces of solar collectors, including concentrating solar power mirrors (CSP) and photovoltaic (PV) modules. Applying a low frequency pulsed voltage to the electrodes which form the central unit of the EDS films charges the dust on the collector surface and ejects it using a travelling wave. The electrodes are of paramount importance to the EDS film as they are the primary working unit of the device. Copper is the current choice of electrode material but it is susceptible to electromigration and has serious environmental disadvantages with respect to corrosion and instability. Copper electrodes also do not meet the transmission efficiency (TE) requirements as the opaque electrodes absorb and obstruct the incident sunlight through shadowing, hurting the output efficiency of the photovoltaic modules. Hence for the EDS film to be a strong candidate as a cleaning technology, it must have environmentally durable electrodes that meet the TE needs. For this purpose (1) I have developed a screen printable ink with zinc oxide (ZnO) and silver nanowire (AgNW) that is transparent in nature which satisfies the TE requirements of the EDS film which were previously unmet; this ink referred to as AgNW_ZnO Hybrid Ink throughout this document is my original contribution for the optimization of the optical performance of the EDS film technology. (2) I have established the environmental durability, stability and functionality of the electrodes of the EDS film through standardized, vigorous testing which were not performed before. To do so, I have followed the testing standards specified under the Accelerated Weathering (QUV) ASTM G154 tests which are used to validate the environmental viability of materials (3) My study and findings on the top surface component of the EDS film proposes measures of action that will enhance the removal of dust and suggests alternative, more cost efficient replacements for the ultrathin glass layer which serves as the current design’s top layer (4) My experiments and results on the charging mechanism/behavior of dust particles upon EDS film activation contribute to optimizing the design parameters used for both the EDS film and the power supply unit used to power it. These contributions allow for increasing the output power restoration of PV modules and specular reflection restoration of CSP mirrors that have the EDS film on their optical surfaces.