Seawater: a resource of interest for renewable hydrogen production

28 March, 2023

The energy sector is making steady progress towards finding alternatives to help achieve the decarbonisation targets set for the coming decades. As far as renewable hydrogen production is concerned, there are also many innovations in this field, such as the possibility of producing this energy vector from seawater. Although it is still at very early stages of research and development, it has some advantages but also a number of challenges. Will it become a real option?

Renewable hydrogen is mainly produced from wind or solar energy and water in a process in which water is broken down into hydrogen and oxygen in a technique called electrolysis.

This totally clean form of production requires, among other things, water and space for wind farms and solar panels. Although at an early stage of development, the sea is an ecosystem with several advantages for the production of green hydrogen. Among the most prominent:

1. Seawater makes up more than 95% of all the water we have on our planet. The use of seawater to produce hydrogen protects inland waters, i.e. waters containing fresh water, which are an easily exhaustible resource.

2. The offshore location of the plants means that it is not necessary to transport water for hydrogen production because large quantities are available on site.

3. More space is available. This creates greater opportunities for the installation of offshore wind and solar farms. Not only in quantity, but also in size and power. The European Union aims to take advantage of this condition to increase offshore wind energy production by a factor of 25 by 2050.

4. Renewable energy sources involved in the hydrogen production process can be produced more consistently at sea because:

• • • In general, the wind blowing offshore is stronger and more constant, allowing up to twice as much wind energy to be produced compared to an onshore installation.
    • Solar radiation is also higher at sea as there is more sunlight. Accordingly, offshore solar panels can be more productive (a study by the University of Utrecht found a 12.96 % higher yield).

The result is green hydrogen that can be used for a wide variety of applications, from industry to transport or electricity generation.

Advantages and challenges of producing green hydrogen from seawater

The electrolysis of seawater – a process in which water is broken down into hydrogen and oxygen – has some advantages over the use of fresh water. The main one is the availability of raw materials. Sea water is abundant, while freshwater is scarce and essential for life on the planet.

Although at an early stage of development, the sea is an advantageous ecosystem for the production of green hydrogen

To produce renewable hydrogen from salt water, coastal locations and proximity to renewable energy plants are needed. For this reason, countries surrounded by the sea are the “favourites” for developing this type of project. This is the case of Spain, which could be in a privileged position to take advantage of the sea’s potential for hydrogen production:

• It is one of the 15 countries with the longest coastline in the world, with almost 8,000 kilometres and about 40% of the country’s population living in a coastal municipality.
• It is a renewable energy powerhouse with plenty of sun and wind, being the second country in Europe in terms of solar and wind energy production. It also has a Roadmap to promote the production and use of hydrogen and has several projects underway, including the European Union’s first renewable hydrogen corridor: H2Med

However, to turn green hydrogen production at sea into a large-scale alternative, technologies and processes need to be adapted. This is due to the composition of salt water, which contains dissolved salts and organic matter that are corrosive to electrolysers (device used in electrolysis). It is therefore necessary to remove impurities and desalinate it before using it to produce hydrogen.

Turning green hydrogen production at sea into a large-scale alternative requires the adaptation of technologies and processes

New techniques and developments are also emerging so that desalination and new electrolysers are no longer required. This is already being researched at universities such as Australia’s RMIT, the US universities Stanford and Houston, and China’s Nanjing Tech.

Finally, there is also a need to manufacture more robust and efficient components that are resistant to corrosion produced by saltwater.

Pilot projects

The use of seawater to produce renewable hydrogen is a possibility that is still in its infancy, but we may soon start to see this market grow. In fact, some pilot installations already exist, such as the Texel and Saint-Nazaire plants.

In the former, on the island of Texel (Denmark), the German company Schaeffler has demonstrated the feasibility of its technology for producing green hydrogen from desalinated seawater and wind energy. And, in the French town of Saint-Nazaire, there is already a pilot plant on the quayside which, after testing all the systems, will be moved to the high seas to produce hydrogen.

In addition, a group of researchers from the University of Cantabria are leading the S2H project to obtain hydrogen using sunlight and seawater as raw materials.

The use of seawater and marine renewable energies for the production of green hydrogen could be another way to boost this energy vector. This is a further alternative to diversify sources, develop new technologies and create a more sustainable value chain.