Solar-Thermal Desalination with Reduced Graphene Nanocomposites and Hydrophobic Polymers for Enhanced Evaporation and Dropwise Condensation

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2024

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Interfacial solar-thermal desalination is an off-grid passively operated method of producing pure drinking water. It shows especially high promise in providing an inexpensive sustainable desalination solution for currently underserved dispersed communities who are unable to adequately secure drinking water and lack the infrastructure to justify traditional large scale energy intensive desalination plants. The aim of this thesis is the fabrication of an inexpensive high efficiency interfacial solar-thermal desalination prototype capable of producing pure drinking water. To meet this aim, the independent development of both a high efficiency evaporator and condensing surface were approached utilizing benign fabrication methods. Improving upon previous solar-to-vapor efficiencies through improved substrate wettability and coating photothermal absorption efficiency, a carbon based solar-thermal evaporator derived from an Aquazone dip coat of reduced graphene oxide (rGO) and polydimethylsiloxane (PDMS) nanocomposite achieved an average solar-to-vapor conversion efficiency of 69.7%. To capitalize on the high vaporization efficiency, a polyvinyl chloride cover treated with a hydrophobic polymer coating for enhanced drop wise condensation was employed for water collection with a measured condensation efficiency of 86.0%. The resulting prototype demonstrated high efficiency through improvement of both condensation and evaporation. Further, the prototype successfully produced pure water from local seawater, meeting water quality standards provided by both the Environmental Protection Agency National Primary Drinking Water Regulations and the Standards and Guidelines for Contaminants in Massachusetts Drinking Waters. Based off this investigation it was also found there exists great potential with bridging the gap from in-situ prototypes productivity to the potential efficiencies of promised from lab values.

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Mechanical engineering, Engineering, Materials Science, dehumidification, drop wise condensation, interfacial water evaporation, polymer nanocomposites, solar desalination

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76 pages

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