Conceptual design and experimental investigation involving a modular desalination system composed of arrayed tubular solar stills

A novel conceptual design of a low temperature multi-effect desalination (LT-MED) system is presented in this paper. The LT-MED system operates at vacuum pressure and is composed of several modules of tubular solar still (TSS) cells, each of which can independently produce freshwater. To verify the performance of the modules in different stages of the system, an experimental TSS was fabricated and tested under different vacuum pressures and heating conditions from 20 to 80 kPa and 100 to 300 W, respectively. The results showed that the energy utilization efficiency exceeded 0.7 in most cases, with a maximum value of approximately 0.81, which was nearly double that of a basin still operated at normal pressure. A 5-effect modular MED system for practical application with a capacity of 86 kg/d was proposed according to the presented theoretical and experimental work. A structural design and control scheme were also presented. Performance and economic analyses indicated a wide applicability of the system, especially for remote and desert regions.