Salinity gradient power by reverse electrodialysis: effect of model parameters on electrical power output

Abstract

Salinity gradient power (SGP) is based on the chemical potential difference between concentrated and dilute salt solutions. Reverse electrodialysis (RED) can thus be used to produce electricity by a SGP-RED unit. In principle,a highly concentrated solution can be recovered from a seawater desalination unit (SWDU) and its concentration further increased using solar energy. The SWDU itself can be based on (solar) evaporation, reverse osmosis or other methods. When thus combining a SGP-RED unit, a SWDU and solar energy, a hybrid system can be considered which involves the concentrated salt solution and seawater (/brackish water) as the "dilute" solution. However, key to the sucess of the hybrid concept is an adequate design of the SGP-RED unit. A basic SGP-RED process model has previously been published. This model was expanded by two distinct dilute and concentrate compartment thicknesses and implemented in a solver to investigate the effect of specific parameters. From these simulations, first recommendations have resulted with respect to the design of the SGP-RED unit (membrane and dilute compartment thickness, temperature) and were reported. Final specifications regarding an optimal SGP-RED unit can only be obtained through a dedicated research program. This would enable the evaluation of the overall technical feasibilities releated to the production/performance of thin ion-conductive membranes, an adequate SGP-RED stack design and the experimental verification of the model simulations.