Operational strategy preventing scaling and wetting in an intermittent membrane distillation process

The solar-powered membrane distillation (SPMD) process can improve the energy efficiency by using solar energy as a heat source. However, the SPMD process can only be intermittently operated due to the variation of the daily solar irradiation. In this study, effects of intermittent modes (IMs with/without temperature variations (IM-1/IM-2)) and continuous mode (CM) on scaling and wetting are investigated according to three types of shutdown protocols (P1: non-draining, P2: draining, P3: flushing after draining). A direct contact membrane distillation coupled with a real-time visualization system using the normalized light intensity and SEM-EDS are used for analysis of the MD performance in each condition. Consequently, scaling and wetting tendencies of SPMD at P3 are lowest among the tested shutdown protocols. Furthermore, scaling and wetting in CM and IM (IM-1 and IM-2) at P3 show low differences, indicating that shutdown protocols have a more profound effect than temperature variations and operation mode.