Profiled membranes in Reverse Electrodialysis

Profiled membranes in Reverse Electrodialysis

Reverse Electrodialysis (RED) produces electrical energy from the mixing of salt water and fresh water. Positive and negative ions are separated by using ion selective membranes. The transport of positive and negative ions is driven by the concentration difference between salt water (for example from the sea) and fresh water (for example from a river).

Salt water and fresh water flow on every side of the membrane through very thin channels. To keep the membranes separated from each other, nylon spacers are used normally. Recently, a method was developed to create structured, profiled membranes which can act as membrane and spacer and replace the conventional spacers.

Recent measurements indicate that profiled membranes give rise to a significant better performance of RED or ED, although results are strongly dependent on flow rate and water concentrations. Stacks with profiled membranes have several differences with respect to stacks with spacers. For example, the spacer shadow effect (due to the non-conductive spacer) is absent for profiled membranes. Also the resistance of the fresh water compartment can be reduced since the membrane material is better conducting that fresh water. Furthermore, the hydrodynamics changes, with possible positive and negative effects on the performance.

In order to make further improvement, it is desired to distinguish the importance and effect of all aspects related to the use of profiled membranes in comparison to conventional spacers. Laboratory experiments at the Wetsus laboratory in Leeuwarden can be performed to estimate the quantitative effect of each aspect.

Preferable background: Chemical Engineering, Mechanical Engineering

Use of project: MSc-thesis or MSc-internship