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Where salt & sweet water transform into energy

Bijgewerkt op: 8 nov. 2023

Text by Peter Scheijgrond, Bluespring

Photos by Sia Windig, Bluespring

Today we visit one of the most captivating forms of renewable energy, literally at the intersection between seawater and freshwater from the lake, located at the Afsluitdijk: REDstack.

Technical marvel: reverse electro-dialysis

It looks mysterious, REDstack's method of generating clean energy by delicately mingling fresh and seawater as each passes one side of a thin membrane. This separation takes place in very narrow channels, packed closely together, thus creating many square meters of 'interaction' in a very compact STACK. As we all know, there is a natural force for the less concentrated fluid to dilute the more concentrated one. Separated by a membrane, this natural force creates a potential differential much like you find in ordinary batteries. The process to tap the energy is called Reverse Electro-Dialysis. Combined this with the stacks, and you arrive at the company name REDstack.

Fieldlab: a mix between a modern gin distillery and a medical lab

At their impressive field lab in Breezanddijk, each stage of the process undergoes testing, including testing of the intakes on both sides of the barrier, the filtration process, and the testing of different types of stacks that have been developed over the years. As you walk around inside, you feel like you are in some kind of mix between a modern gin distillery and a medical lab.

As we nibble on delicious Dutch speculaas cookies, Rik Siebers and Michael van Oostrom explain how a smart filtration process helps to extend the life of the membranes and at the same time increases the power output of the stacks, and many more technical details that we try to digest :). Time to have a look outside.

The world's largest inshore wind farm

First we see a cluster of wind turbines majestically dooming up in the misty sky. Although clearly installed in water, they are not located at sea. This is a wind farm on the lake, in the IJsselmeer to be precise. The turbines are so close to the shore, you really feel their grandeur. The wing span is a whopping 130 meters tip to tip. This is the world's largest inshore wind farm that we see from the bus, with 89 turbines and a combined installed capacity of 360MW.

Scaling up & energy security

As we walk around the plant, Michael and Rik passionately give examples of suitable locations anywhere in the world where fresh water from rivers flows out into the sea. Usually, these delta's are densely populated and thus have high energy demands. With increasing sea levels and storms, barriers and dikes are built to protect the population. These sites form ideal conditions for salinity gradient power (SGP), also dubbed as osmotic power or simply Blue Energy. Another big plus is that with salinity gradient power, you can produce virtually 24/7 and 365 days a year. For renewables, this is a unique selling point in our goals to reach a secure and sustainable energy supply for everyone.

Site investigations are taking place in India, France, central-America, and many other locations. The main challenge is to minimize the filtration needs, to keep the cost down. Scaling up to MWs is relatively easy because the stacks are so modular.

Interested in energy security modeling?

Energy security modeling for offshore renewable energy will be a focal point in the newly initiated Offshore For Sure project. Additionally, various business cases will be investigated and validated by diverse launching customers, including governments, cooperatives, and project developers. If you want to become involved, please fill in the form.

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