A floating vapor condensation structure in a heat-localized solar evaporation system for facile solar desalination

•An industrial-scale feasible method to condense vapor is proposed.•The desalination system is featured with cost effective, easy to mass scale.•The energy efficiency is analyzed based on a heat and mass transfer model.•The structure influence of the condenser is studied by experimental methods.•The seawater and outdoor tests confirm the high performance of the system. Solar evaporation by heat localization has drawn great interests for efficient and facile solar desalination since 2014. However, most of efforts have been put into improving the vapor generation performance in the last few years, with facile and efficient vapor condensation remaining a challenge. In this work, we propose a feasible method to condense vapor, featured with simple structure, cost effective, easy to mass scale and flexible operation. The energy efficiency in the solar-vapor-water process is theoretically analyzed based on the heat and mass transfer in our solar desalination system, to provide guidance especially for improving the vapor condensation process. The structure influence of the grid-trough condenser on the energy utilization in the vapor-water process is further investigated by experimental methods. Combining the optimal grid-trough condenser with a reversely-designed heat-localized evaporator, the new-designed system shows a great potential in facile solar desalination. It could achieve a freshwater production rate of 0.393 kgm-2h-1 and a vapor collection efficiency of 38.8% under one sun illumination by the relatively optimal condenser which strikes a balance between efficiency, cost and system complexity. The seawater tests and outdoor experiments confirm that this system still could perform well and float spontaneously on a lake to produce freshwater continuously. Additionally, the energy efficiency of this system has ample room for improvements through optimizing the system structure and employing new materials.