Blue Energy (or salinity gradient energy) is a renewable energy source mentioned in the literature since the 1950s. In a reverse electrodialysis system, a number of cation and anion exchange membranes are stacked in an alternating pattern between a cathode and an anode (Figure 1). When a concentrated salt solution flows through the alternating cells and fresh water flows through the others, a voltage is generated over each ion exchange membrane. The total voltage equals the sum of the voltages over each cell pair, which are additive. At the electrodes, the useful power can be obtained.
Figure 1: Schematic representation of reverse electrodialysis; C is a cation exchange membrane and A is an anion exchange membrane.
RED or Blue Energy is currently being realized at the Afsluitdijk with a pilot plant (Figure 2), where large scale testing with real conditions is planned for 2014. Companies involved in this project are Fujifilm (for membrane development) and REDstack.
Figure 2: (left) photograph of the pilot plant at the Afsluitdijk and (right) Artist impression of the pilot plant operation.
However, there are some challenges to overcome before RED can be economically attractive. This research focusses on the membranes used in this process via optimization of membrane chemistry and structure and via understanding structure-property relations. The following membrane properties are evaluated:
• Monovalent-ion selectivity
Timon Rijnaarts, MSc email@example.com
This work is a collaboration with Wetsus, Centre of Excellence for Sustainable Water Technology, located in Leeuwarden (NL).