Optimization Study on Salinity Gradient Energy Capture from Brine and Dilute Brine

Abstract

The direct discharge of concentrated brine from seawater desalination waste the salinity gradient energy (SGE) and impair coastal marine ecologies as well. The energy can be captured for power production by drawing the brine and seawater into the reverse electrodialysis (RED) stack, by which the concentrated brine is also diluted efficiently. The performance of the stack is strongly correlated with the feeding parameters and stack size, however, which is still an unclarified subject in the SGE utilization. Here ions migration models considering the migration of water molecules for a RED stack harvesting the SGE between the concentrated brine and seawater are constructed, with correlation coefficients determined and verified by experiments. Principal feeding parameters (concentration, flow rate, and temperature) and the stack size are optimized to enhance the stack performances. Results show that high power density and energy conversion efficiency can be achieved simultaneously by adjusting feeding parameters and shortening the length of the stack. The constructed models and the optimization method could conduct optimal design of structural parameters and the adjustment of feeding parameters for the RED stack recovering more SGE.

Keywords: Power production, Concentrated brine, Salinity gradient energy, reverse electrodialysis