Conclusions pilot plant

Recent achievements in Blue Energy developments

• The original calculated and modeled performance, validated by Wetsus and KEMA, is achieved with “real world” fresh and salt water at TRL 7.
• The influence of temperature and salt concentrations of the waterflows have to be considered as being important.
• The stacks have been upscaled with a factor 1000, from labscale 0.25 m2 to 250 m2 pilot scale.
• This upscaling of the membrane stacks from 0.25 m2 up to 250 m2 of membrane per stack did not have any negative impact on the power-generating-efficiency, neither per m3 of water nor per m2 of membrane, the efficiency remained the same during the upscaling.
• CFD modelling shows that further upscaling to 2000 m2 of membrane per stack (TRL 8) will not lead to a reduced efficiency. This will be proven in the upcoming period.
• Fouling of the water intake is prevented by special water intake equipment and coatings.
• The biofouling and scaling in the membrane-stacks is under control and minimal; it does not have a negative influence on the energy generating performance thanks to the unique stack design and mode of operation.
• A long term continuous operation of the plant is possible and proven.
• Studies by independent parties (e.g. Deltares and NIOZ) proved minimal ecological impact of the Blue Energy pilot plant.
• The ecological impact of a full-scale RED Blue Energy power plant, even in a sensitive ecosystem as the Waddenzee (UNESCO protected area), is assessed and considered as minimal as long as the same design criteria are used as at the pilot-plant Afsluitdijk

In more detail and looking ahead
Over the past decade, starting with the construction of the Blue Energy research facility on the Afsluitdijk in 2013, all individual pieces of the puzzle that together will form the blueprint for the commercial application of Blue Energy Power Plants have been studied and developed.

After the commissioning in 2014 of this installation, the Reverse ElectroDialysis (RED) technology was tested – worldwide for the first time - on a relevant scale in a relevant environment. The complete technology, from intake to supplying the power to the grid has been studied during the first four years. Meanwhile, upscaling stacks the stacks thousandfold in size, from 0,25 m2 of membrane area to 250 m2 membrane area per stack without losses in performance.

Valuable lessons have been learned regarding the fouling of the system and effective countermeasure were developed. Like the wedge wire screens with an anti-fouling coating on the intake point, to prevent the blocking of the intake by the growth of barnacles and to prevent the intake of juvenile fish, and larvae / eggs from fish and shellfish. And the development of an effective combination of pre-treatment with rapid sand filtration, air sparging as cleaning in place, and the application of profiled membranes, to prevent fouling of the RED stacks.

After demonstrating the technological feasibility of the RED technology using natural waters, the focus shifted to other pieces of the puzzle that needed to be developed. To anticipate on a future environmental effects study, that would be needed for a large-scale RED installation, REDstack initiated a project together with independent research partners Deltares, Netherland Institute for Sea Research (NIOZ), Wageningen Marine Research and Ziltwater Advies. Focussing on the potential effects of the intake, pre-treatment and return of the mixed waters on the survival of small organisms like zooplankton and eggs / larvae of fish and shellfish. And how to mitigate these effects. The outcome of this project demonstrated that when properly designed, the ecological impact is minimal, even when a 60 MW full-scale plant would be operated in sensitive ecosystems as the Waddenzee (UNESCO World Heritage).

To further boost the performance of the process on the road to commercial application, a significant amount of research and development has been put into designing the optimal process configuration for a simultaneous high power density (≥1 W/m2) combined with high energy efficiency (≥80 % of the technical possible amount). Resulting in an optimized process configuration in terms of the feed water ratio and residence time for a configuration with two stacks in series.

For the economical feasibility of the process the production cost of the RED modules is crucial. This required a complete conversion of the stack design as develop during the years of research, to an industrial design that allows for large scale automated assembly. To facilitate this development, the engineering team of REDstack was expanded, and together with renowned partners like Demcon Industrial Systems, BPO and AM-team, a complete new industrial stack design was developed, suitable for large scale automated assembly. With AM-team the fluid distribution inside the stack was optimized using CFD modelling for stacks upscaled tenfold in size, up to 2000 m2 of membrane area. The designs were made for the required parts, ready to be produced using injection moulding. And the concept design of the automated assembly station for RED stacks has been developed.

Starting this year, REDstack will put all of these components together into a full industrial design in order to demonstrate and prove the application of Blue Energy on real surface waters to be technologically, ecologically, and economically feasible.

Within a newly funded project, the Research Facility on the Afsluitdijk will be converted into a full-scale Pilot, incorporating all the individual process units that have been developed, applied, and tested. Upscaling and finetuning the intake and pre-treatment method to mitigate potential negative environmental effects. And to go even a step further, by researching the possibilities to create added value for the ecology. The stacks will be converted in to industrial process units, designed with 2000 m2 of membrane area, forming the basic building block for future commercial installations. Twelve of these large-scale RED stacks will be produced in the developed assembly infrastructure and will be incorporated in the pilot. These twelve stacks will be used to demonstrate the economic, technical and ecological feasibility of the process, producing continuous Blue Energy.

REDstack, May 2023