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'Sea hydrogen' produces hydrogen, drinking water, electricity, table salt and minerals

By: André Oerlemans
Making green hydrogen from seawater and clean drinking water and electricity at the same time. And also filter valuable minerals such as lithium and table salt from the same seawater. Researchers from Wageningen University & Research (WUR) show that it is possible with the Sea Hydrogen method (SeaHydrogen). “In this way we keep the hydrogen economy environmentally friendly and feasible.”
The Netherlands needs large quantities of green hydrogen to achieve its climate goals. This is hydrogen that is made from water using green electricity through electrolysis. When this is burned, only water and oxygen are released, so no CO2. Green hydrogen can be used for processes in the (chemical) industry, for trucks, buses, trains, cars and in the future perhaps also for heating buildings and homes. In addition, it can play an important role in the temporary storage of excess green energy from solar and wind energy. The government has tightened its goals for the hydrogen economy in 2022. By 2032, electrolysers in the Netherlands should be able to produce 8 gigawatts of green hydrogen.

Sea hydrogen
WUR's SeaHydrogen method combines existing and new water technologies in an integrated total system. This overcomes the current disadvantages of the production of green hydrogen and at the same time provides various benefits that are useful to society, such as producing clean drinking water, electricity and valuable minerals. “We combine seawater with hydrogen and are left with fresh water in the middle. That is why we call the method sea hydrogen,” says Irma Steemers-Rijkse, program manager for circular water technologies at Wageningen University & Research (WUR).
Green hydrogen increases drinking water shortage
A problem that is often overlooked is that green hydrogen is currently still made from fresh water. The production of those 8 gigawatts in 2032 requires an estimated 11 billion liters of pure water. If electrolysers use drinking water for this purpose, they consume 1 percent of the annual drinking water capacity in the Netherlands. While drier summers and long periods without rain are already leading to water shortages. According to the RIVM, all ten Dutch drinking water companies will face shortages by 2030 if users do not use water more efficiently, rainwater is not collected better and no new sources are tapped. The use of fresh water for hydrogen could therefore lead to additional drinking water shortages, experts warn. “With all the plans for hydrogen production, the government has somewhat forgotten that you need lots of water for this and that it puts enormous pressure on your drinking and freshwater sources,” says Steemers-Rijkse. “We want to help solve that problem by eliminating shortages.”

Disadvantages of salt water
This can be done by using seawater. There is enough, but so far it has hardly been used because the salt attacks the electrolysers. With reverse osmosis (RO) you can turn seawater into fresh water - as is already happening a lot in the Middle East and increasingly in Europe - but that also has disadvantages. The method requires a lot of electricity and the remaining brine (brine) is too salty and contains too many chemicals to be discharged into the sea, surface water or into the soil. “Discharge on land is a major problem. That's not possible just like that. Working up and removing the salts takes a lot of energy. You can discharge it at sea, because it is already salty. But you do see in areas such as Spain and the Middle East that the use of many reverse osmosis systems causes additional salinization. This creates a kind of Dead Sea effect, which means that maritime life no longer has a chance,” Steemers-Rijkse explains.
Residual heat unused
An important disadvantage of making hydrogen via electrolysers is that a lot of residual heat is released. It has a temperature of approximately 80 degrees Celsius and no application has yet been found for it. In fact, water is needed to cool electrolysers and remove residual heat, which increases the demand for water even further.

Economically viable solution to problems
WUR's proposed Sea Hydrogen method solves all these problems. It uses salt water and residual heat and not only produces green hydrogen, but also fresh water and electricity. Furthermore, valuable minerals are extracted from the brine. “What we see in our prosperous economies is that you take what you need and throw away what you don't want anymore. The same with water. We think things can be done very differently. That you can use everything internally, making it economically feasible and interesting as a business model,” says Steemers-Rijkse.

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Membrane technology
The method uses membrane technology and residual heat to distill water. Six years ago, a former TNO department was transferred to WUR, which conducts a lot of research into water technologies, including purifying water and recovering substances using membranes. For example, WUR experts contributed years ago to the development and upscaling of membrane distillation technology (MD). Unlike reverse osmosis, this technique hardly requires electricity. Using the residual heat from the electrolyser, salty seawater is turned into clean drinking water by allowing it to evaporate and condense again. That's the first step. The method uses no chemicals and has little impact on the environment.

More fresh water than needed for hydrogen
That pure water is used to make green hydrogen in the electrolyser. This releases residual heat that can be used to desalinate water via membranes. A pilot test on Texel showed that the method allows you to produce much more pure water than the electrolyser needs. “You can even use that fresh water to solve water shortages and turn seawater into drinking water. Ideally, you have these types of systems on the coast, where on the one hand you draw in seawater to make hydrogen and on the other hand you lay a freshwater pipeline to the interior," says Steemers-Rijkse. “In this way we keep the hydrogen economy environmentally friendly and feasible.”
Table salt and lithium from brine
The second step is to upgrade brine using this process. This is automatically left over after desalination. Valuable minerals and salts can be extracted from this through a combination of crystallization and membrane distillation technology. “Normally you will not extract valuable salts from seawater, because the concentrations are far too low to make this economically viable. But because you have already taken a step here with the production of pure water, it may now become profitable. Especially in combination with the available residual heat,” says Steemers-Rijkse. “For this we have to thicken the brine further. We have a patent on this and this year we are starting a project to extract these minerals as concentrated as possible. First we extract ordinary table salt from it. Then you are left with a concentrated salt solution with valuable other components. For example, lithium, which can be used in batteries.”
Ready for the market
The elaboration of this new method will be published at the end of 2023. Now it is time to apply the technology in practice, among other things to reduce the pressure on drinking water supplies. Governments, private and commercial parties can already get started with the first step of the Sea Hydrogen method. WUR will be working on the second part for mineral extraction this year through a project. The third part with MemPower requires further development before the method is ready for the market.

Electricity from residual heat
In the third step, the residual heat is used to convert seawater into not only fresh water, but also electricity. This could be a good solution for offshore electrolysers, for example. Another form of membrane distillation is used, called MemPower. “Then you make water for your electrolyser, but you convert the surplus into electricity with your residual heat,” says Steemers-Rijkse. In winter, when there are fewer water shortages due to excessive rainfall, onshore installations can be configured to produce less fresh water and more electricity.

See how the MemPower technology works here:


  • Abraham Jok Atem

    14 w

    Sea hydrogen has multiple uses therefore we need to utilize it

    • Munene Mugambi

      14 w

      With the right systems we could get a lot from the sea including power, food and energy.

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