Potential of brackish water and brine for energy generation by salinity gradient power-reverse electrodialysis (SGP-RE)

In the present work, a salinity gradient power-reverse electrodialysis (SGP-RE) unit was tested for theproduction of electrical energy by exploiting the chemical potential of real brackish water and exhaustbrine from a solar pond. A cross-flow SGP-RE module (REDstack B.V.), equipped with AEM-80045 andCEM-80050 membranes specifically developed by Fujifilm Manufacturing Europe B.V. within theEU-funded project REAPOWER (“Reverse Electrodialysis Alternative Power Production”), was able togenerate a maximum power density (expressed in W m2 membrane pair – MP) of 3.04 W m2 MP whenoperated with pure NaCl aqueous solutions (0.1 M in low concentration compartment – LCC, 5 M inhigh concentration compartment – HCC) at 20 C and at a recirculation rate of 20 L h1. However, adrastic reduction to 1.13 W m2 (63%) was observed when feeding the SGP-RE unit with artificial multiionsolutions mimicking real brackish water and exhaust brine. Further experimental activity allowed toidentify Mg2+ ion as responsible for the significant increase in stack resistance and consequent depletionin SGP-RE performance. Therefore, specific softening treatments of the real solutions should beconsidered in order to maintain the process efficiency at practical level.