The Research On Solar Desalination System With Flat Plate Collectors

The21st century is the century of water, the problem of fresh water resources scarcity worldwide has caused great attention around the world. Currently conventional desalination technology has made some progress, but consumes a lot of fossil fuels, bring greenhouse effect, atmospheric haze and other environmental problems. Many scholars conducted a study about this, and solar desalination technology is considered to be a sustainable development technology.In this paper, a solar-powered low temperature multi-effect distillation(LT-MED) desalination system with flat plate collectors(FPC) is as the research object. The flat-plate collector has a large lighting area, an easy building integration and other advantages, which is in line with the future development trend of solar energy utilization, LT-MED system does not require a high heat source, is easily coupled with solar flat plate collector system. Based on the laws of energy and mass conservation, the mathematical and economic models of solar-powered LT-MED desalination system are established, and the system models are programmed and solved by utilizing MATLAB.The heat-collecting capacity and efficiency of FPC are analyzed in different monthly average day, and the collector load where fresh water is least is as the collector design load. On this basis, the influence on system thermal and economic performance by area of FPC, collector outlet temperature, effects number of MED system and first effect heating temperature are analyzed. Under the calculation conditions of this paper, with collector area increasing, personnel cost remains constant, the other subsystem costs all increase, fresh water production increases, fresh water production per unit of collector area decreases, fresh water cost reduces slowly; with collector outlet temperature increasing, storage tank cost reduces slowly, the other subsystem costs almost remain the same, fresh water production and fresh water production per unit of collector area remain unchanged, fresh water cost reduces slowly; with effects number of MED system increasing, evaporator and civil installation and auxiliary equipment cost both incresae, the other subsystem costs almost remain the same, fresh water production and fresh water production per unit of collector area increase, fresh water cost gradually reduces, when effects number reach a certain value; with first effect heating temperature increasing, storage tank cost increases, the operating cost of electric auxiliary system increases then almost remains unchanged, evaporator cost gradually reduces, the other subsystem costs almost remain the same, fresh water production and fresh water production per unit of collector area increase then reduce gradually, fresh water production reduces then increases gradually.The system performance is analyzed in varying load for the fixed device without electric auxiliary subsystem, the system load rate is between40%and110%, the fresh water cost in a varying load system is under the rated load system with electric auxiliary subsystem.Finally the thermal and economic performance of solar desaliantion system with ETC and FPC is contrasted and analyzed. Under the calculation conditions of this paper, for the same collector area, the heat-collecting capacity of FPC is more than that of ETC, and fresh wanter production of solar desalination system with FPC is bigger, fresh water cost is smaller. But because of the great fluctuation of the heat-collecting capacity of FPC, the operating cost of electric auxiliary system is more bigger, the solar desalination system with FPC is not well energy saving from the point of energy utilization.