7.4 Scale-up of novel redox free concepts for generating salinity gradient energy

There is a great societal need for clean and renewable energy, to replace the use of polluting fossil fuels. An energy source gaining increased attention, is the mixing energy released when mixing river water with sea water, the so-called Salinity Gradient Energy (SGE). This energy source has a similar potential as conventional hydropower.
Reversed Electro Dialysis (RED) is a very attractive technology for the production of power from SGE. In RED, sea water and fresh water flow through a pile of alternating stacked anion exchange membranes and cation exchange membranes. The membranes separate the sea water from the fresh water, and only ions can pass through the ion selective membranes. The concentration difference between the two solutions creates a membrane potential, which is the driving force for ions to flow from the sea water to the fresh water. At the both ends of the membrane pile electrodes are placed that use a redox couple to convert the ion flow into an electron flow.

The RED system is not only capable of harvesting the salinity gradient energy but also can play an important role in energy storage and electricity production from waste heat.

Research challenge
As result of Wetsus research, RED has been brought from idea to working at pilot scale on site. Building on this track record, this project will develop and scale-up novel, redox free, concepts for RED.
Current RED stacks use a redox component at the electrodes enclosing the membrane pile. A system without chemicals, and possible unwanted by-products, would be both more sustainable and economical. The first direction for achieving redox free operation is the use of capacitive electrodes. Suitable electrodes will be developed and the optimal operation determined. Scale-up will aim at optimizing the performance under real-life conditions.
In scaling-up novel concepts for RED, not only the performance of the stack will be taken into account. But also the impact on the total system, from intake to discharge, will be included in the evaluation. Up to now, most research has focused on single pass continuous operation of RED stacks. To overcome limitations in RED performance, novel modes of operation will be developed. Models will be used to optimize the performance and real life validation at the pilot site is performed where possible.
New concepts will not be only evaluated for salinity gradient energy generation, but also applications for battery operation will be considered. A combined experimental and modeling research approach will be used.

We are looking for a candidate with an MSc degree in the field of process engineering or environmental engineering with both modeling and experimental skills. A driver’s license is required.

The research project is part of the Wetsus research theme Blue Energy.
The following companies are part of the theme: A. Hak Construction (, Alliander (, AquaBattery (, Fujifilm (, Landustrie/Desah (, REDstack ( and W&F Technologies (

Promotor: Prof.dr. S.R.A. Kersten (University of Twente)
Co-promotor: Dr. Annemiek ter Heijne (Wageningen University)
Wetsus supervisor: dr. Michel Saakes

For more information contact:

Please do NOT send your CV directly to this email address. Only complete applications sent via the website will be evaluated (How to Apply).

Wetsus, Leeuwarden, The Netherlands

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