Experimental study on salinity gradient energy recovery from desalination seawater based on RED

Recovery on salinity gradient energy (SGE) usually existing at the junction of rivers and sea, have attracted a large amount of researchers. However, recovery and utilization of the SGE between desalinated seawater and seawater discharged from desalination plants, is relatively unexplored. In this work, a reverse electrodialysis (RED) approach is introduced to recover the SGE and convert it into electric energy. The objectives of this work are: i) exploring the feasibility to recover the SGE by adopting the RED method; ii) investigating the influence of different inlet parameter on the performance of a RED stack. On the basis of above aims, comparative experiments are implemented to verify the feasibility. Then the factors affecting the performance of the RED stack are analyzed. Results show that the power density of desalinated seawater (3.0 mol/L)/seawater (0.50 mol/L) is slightly higher than that of seawater/freshwater (0.060 mol/L), and lower than that of desalinated seawater/ freshwater. A high concentration, temperature, and flow rate can improve efficiently the performance of the stack. For a RED stack composed of 10 membrane cells with desalinated seawater in the concentration range of 1.5 mol/L-3.0 mol/L, the open-circuit voltage and the maximum power density can reach 0.966 V and 0.372 W/ m2 respectively. This study can provide some guidance for the recovery of SGE between desalinated seawater and seawater.