REDstack produces energy out of fresh and salt water


There is an enormous energy potential at the interface between fresh and salt water. With a technique known as reverse electrodialysis (RED), it is possible to harvest the energy potential of the partial flows. REDstack joins the Dragons’ Den of Transition and will ask the dragons to fund the upscaling of the pilot plant as well as the stackproduction.

Worldwide, there are many delta areas where fresh water from rivers flows into the salty sea. In addition, many sewage plants discharge their fresh water into the sea. As far as REDstack is concerned, these are all potential sources of energy. Director Pieter Hack has already calculated that one terawatt of blue energy is available worldwide. It only needs to be harvested. Theoretically, the energy potential of a square metre of membrane is two watts. This means that a cubic metre of fresh water flowing into the sea could generate one megawatt per second’, says Hack.


Hack: ‘We have achieved significant results with the stack technology. We not only know how to design the stacks, but also how the processes around them should be organised. After all, you have to take in water, pre-filter it and channel it into the stacks. The next step for us is to start up scale-up projects so that we can demonstrate the industrial operation of blue energy to potential customers. This is a very interesting technology for renewable energy producers because it provides a fixed base load.’


To supply on a larger scale, we do need to set up a membrane production line. And if we can produce the stacks on an industrial scale, they will become cheaper and cheaper. And for that we mainly need money.

Request for help

With 17 million euros, REDstack will be able to scale up in the next three years until it can stand on its own two feet. Hack: ‘We already have a lot of interest, not only from some European countries, but also from Colombia, South Africa and South Korea. Moreover, there is already a five million euro grant waiting for us. However, we can only make use of that if we can invest three million euros of our own money. Our business case is therefore very attractive to an investor with a mature technology and a market that would rather use both desalination and energy generation possibilities today than tomorrow.’


Dragons’ Den of Transition is the closing event of European Industry and Energy Summit 2021 (EIES2021). More information on the event on 7 and 8 December in Rotterdam Ahoy.