Design and optimization of hybrid seawater reverse osmosis-solar-driven desalination-pressure retarded osmosis system for energy efficient desalination maximizing economic potential

Seawater reverse osmosis (SWRO)-pressure retarded osmosis (PRO) hybrid desalination system is being actively researched to reduce energy consumption by generating energy in the PRO. However, the SWRO-PRO hybrid system still faces the following challenges: low freshwater recovery and low energy generation. To resolve these challenges, this study first proposes a novel SWRO-Solar-driven desalination (SD)-PRO hybrid system for energy-efficient desalination. The proposed system comprises three major processes: SWRO for freshwater recovery, SD for freshwater recovery, and PRO for energy generation. First, the pressurized seawater passes through a semi-permeable SWRO membrane to produce freshwater, and the remaining concentrated brine enters the SD system. Second, an evaporator, that absorbs solar energy and quickly evaporates water floats on the SD system to recover additional freshwater. Third, the highly concentrated brine that remains unevaporated is used as a draw solution in PRO to generate energy. Consequently, the total freshwater recovery is increased by 14.54%, the specific energy consumption is reduced by 38.86%, and the levelized cost of the freshwater is reduced by 16.67% compared with the conventional SWRO-PRO system. Furthermore, the life cycle assessment results demonstrate that the proposed system is environmentally friendly. These results indicate that the proposed system is a feasible solution for sustainable desalination.