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Generating eight gigawatts of electricity from hydrogen: that’s the government’s goal for 2032. This is a staggering task, since the current method is far from ideal, says Irma Steemers-Rijkse of Wageningen University & Research. In the SeaHydrogen project, she aims to combine various processes into a single, total concept that will be used to produce drinking water, salt and energy.
To understand the concept behind SeaHydrogen, Irma Steemers-Rijkse, programme lead of Circular Water Technology, first explains the method used to produce the intended eight gigawatts. To produce hydrogen, you need an electrolyser that separates water into hydrogen and oxygen. This electrolyser uses significant quantities of fresh water: the planned production requires no less than 11 million m³ of pure water per year, which equals 1% of the total drinking water capacity of the Netherlands. ‘This significantly impacts the available fresh water supply, especially in dry periods, and will increase the likelihood of shortages. On top of that, electrolysis generates lots of residual heat, which means even more water is needed to cool the installation. As such, it is not the most sustainable method,’ she says. The risk of drinking water shortages due to hydrogen production can be reduced by tapping into a different source: seawater. Through an existing process called reverse osmosis, seawater can be turned into fresh water. The problem is one of efficiency: half a litre of fresh water costs a full litre of seawater. Steemers-Rijkse: ‘Moreover, reverse osmosis requires power, which is not ideal when you’re trying to generate sustainable energy.’ On top of this, the production of fresh water also creates a residual flow of highly salty water, called brine. ‘On land, brine leads to salinisation. This causes problems for crop cultivation. Offshore, excessive salt concentrations are harmful to marine life. In short, using salt water for hydrogen production has several disadvantages.’
'To reduce the risk of drinking water shortages, an alternative water source can be used: seawater'
Using residual heat from the electrolyser, pure water (free of salts) is produced from seawater on Texel. Photo: WUR
That’s why Steemers-Rijkse and her colleagues first looked for a method that could make the production of fresh water for the electrolyser more efficient. The application of membrane distillation, a process in which water is heated, seemed promising. This way, the residual heat issue could be turned into a benefit. The heating process produces vapours that are separated from the liquid water using a membrane. The salts from the seawater remain in the liquid, while the vapour consists of pure water. ‘Membrane distillation supplies more than enough water for the production of hydrogen, and even more. That water can be used as drinking water, or for agricultural or industrial applications. The amount of residual brine is a lot lower. What’s left is a highly concentrated flow of salt water,’ she explains.
Extracting table salt and other salts for industrial applications
By the end of 2023, the membrane distillation study was concluded successfully. However, Steemers-Rijkse and her colleagues still felt like their work wasn’t done. They hadn’t found a solution for the residual brine, and the hydrogen production still produced residual heat. ‘You can persist in the view that brine is something negative, but you can also see if this salt can be used for other applications,’ she explains. ‘We eventually got the idea to add other technologies. The resulting combination had now become a total concept: SeaHydrogen.’
Hydrogen production for our future power supply isn’t quite as sustainable as it seems. SeaHydrogen shows that it can be. In this project, researchers of Wageningen University & Research combine various process to form a single solution that can produce drinking water, salt and energy from seawater. But how does it work?
The researchers even have a proof-of-concept for the extraction of salt from brine. This method, wordily referred to as membrane distillation crystallisation, uses the residual heat of the electrolyser. Membrane distillation crystallisation combines the membrane distillation with the crystallisation of a salt, like NaCI also known as table salt. This is achieved by adding a more soluble salt to the mix. As a result, the salt the researchers aim to extract will form crystals that can then be harvested.
Over the next three years, the researchers want to continue the development of this salt extraction method. They will start with the salt that has the highest presence in seawater, and, in turn, brine: NaCI. Steemers-Rijkse: ‘For example, we would like to know if the salt accumulates in the wrong parts of the installation. It also remains to be seen whether it’s possible to extract pure table salt rather than a mixture of different salts.’
Left: Linear approach using electricity for pure water production. Right: Circular approach using residual heat for the production of pure water, minerals, and electricity. Images: WUR
If the researchers succeed in extracting table salt, they will also attempt to extract other salt types from the brine. ‘You can use the same trick for other salt types, but we can only start doing that once the first step, extracting table salt, works properly and yields a profit.’ Steemers-Rijkse’s wish list also includes minerals for other applications, like phosphorous for the horticulture sector, magnesium for the pharmaceutical industry and lithium for mobile phones.
Residual heat and seawater = drinking water and salt
‘What’s so great is that there are multiple ways to make the SeaHydrogen total concept profitable’, the circular water technology expert says. ‘It all depends on the goal of your organisation. If you want to produce as much fresh water as possible, you can simply use most of the residual heat from the electrolyser for this. If you aim to extract salt, you can either prioritise table salt or extract various different types. The more steps you take in the extraction process, the more of the residual heat is used. The heat that remains in the end can still be used to generate electricity. To make this possible, the membrane distillation process does require further development, however. You shouldn’t see this as a set of separate technologies. Combining them allows you to use them optimally to achieve maximum profitability.’
'What’s great about it is that there are multiple ways to make the SeaHydrogen total concept profitable'
Aerial view of farmland affected by salinization. Photo: Shutterstock.
The SeaHydrogen researchers expect that a combination of these technologies could be an interesting prospect for various organisations. ‘Take factories with low-grade residual heat, for instance, that cannot be used for anything else, or the heat produced by data centres. Or waste water resulting from the production of foodstuffs.’ For example, they started a partnership with Aviko with the aim of reusing all of the waste water from their factories. Circle Infra Partners, a company that processes the waste water of the factories on the Limburg industrial estate Chemelot, has also joined the project, aiming to cease discharging waste water to the river. Circle Infra Partners wants to explore reduction of discharging waste water into the river Maas. Finally, salt producer Nobian is also involved in the project. Under the Grow Greener Together initiative, this company wants to further improve the efficiency and sustainability.
Environmental benefits combined with profit
In cooperation with these three companies and various other parties, the researchers have launched the Combrine project, referring to the processing of brine. ‘We will soon start building laboratory setups that allow us to test water provided by these various partners, followed by on-site pilots. In three years, we hope our technology has developed sufficiently to enable practical application. The funny thing about the SeaHydrogen concept is that you can determine the issues and required solutions for each individual situation. Eventually, we’ll have a total package that will offer environmental benefits as well as profits. That is an important factor, too.’
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