Offshore hydrogen production and treatment using electrolysers: a case study on a pilot project in Nantes, France, to tackle ocean dissolved oxygen

Given that hydrogen production and water use are inextricably bound, it is unlikely that water supply will continue to be omitted. The inconvenient truth, say both Brouwer and Rosa, is that solar energy is the cheapest source of low-carbon power available to produce hydrogen, but the regions with the best solar resources are also some of the most parched.

To steer economies away from fossil fuels and to cut carbon emissions, hydrogen needs to be produced from low-carbon energy sources, such as wind and solar power. The shipping, aviation and steel industries would struggle to run on batteries or to use renewable energy directly through power grids if green hydrogen were available to them. Electricity zapped into water splits H2O in two, hydrogen and oxygen, which form gas H2 and O2. The hydrogen can then be piped to where energy is needed.

Lhyfe is now exploring whether the oxygen from offshore electrolysis could counteract declining levels of dissolved oxygen in the ocean — conditions that are stunting marine ecosystems in some regions. In July, researchers projected that artificial oxygenation from global deployment of offshore wind farms and electrolysers could reduce the volume of severely hypoxic zones by 1.1–2.4% (ref. 6). But they also reported some counterintuitive regional impacts. Their simulation projected oxygen injection in the Indian Ocean might expand the hypoxic zone.

The hydrogen producer Lhyfe’s 1-megawatt pilot platform operated offshore for 5 months this year using desalinated seawater, and a 10-megawatt platform is planned for Belgian waters in 2026. Lhyfe in Nantes, France, wants to mitigate the impact of desalination by eschewing chemical additives in its treatment process, and by diluting brine with extra seawater, says Stéphane Le Berre, Lhyfe’s offshore project manager.

The city could save about US$ 1.5 million per year by integrating electrolysers into wastewater treatment plants, which have been researched by researchers with the Municipal Water authority and University of Sydney, Australia. One-tenth of the amount of green hydrogen expected to be produced by Australia and New Zealand in 15 years is inferred by the analysts from S&P Global. Sydney Water says that it’s research confirms the viability of hydrogen production from its treated water.

Some observers, however, foresee potential environmental dividends if hydrogen producers tap seawater and waste water. Thomas Adisorn, a political scientist at Germany’s Wuppertal Institute for Climate, Environment and Energy, sees potential for projects such as that of Plug Power to improve the environment by supporting international development. In order to help officials with the hydrogen economy in Jordan, Adisorn organized a meeting in 1992 to use recycled waste water for the construction of wastewater infrastructure.

Using seawater presents almost limitless potential, but also troubling environmental impacts. Some desalination plants release heated brines laden with treatment chemicals back into the sea; they can also suck in and destroy marine creatures. The most significant ecosystem impact of these plants, according to a 2020 review4, is lethal osmotic shock to marine organisms, including fish, plankton and algae when super-salty brines cause their cells to dehydrate. Most at risk are organisms in semi-closed seas such as the Red Sea, the Mediterranean and the Persian Gulf. Nearly half of the world’s desalination capacity is concentrated in the Persian Gulf.

If hydrogen producers tap polluted or salty water instead of potable water, they could avoid adding strain to the water supplies. Municipal waste water, waste water from oil and gas production and even seawater are some of the options. Water treatment and desalination plants are expensive to build, but the investment is comparatively small relative to the overall cost of hydrogen production.

Water for producing hydrogen by electrolysis must be 9 litres of H2O and treated to remove minerals that would gum up the works.

There is more to the story that is still being told. If renewable energy powers the process then more water use will be counted. Manufacturing solar panels and wind turbines consumes more water than the operation does. The water footprint of green hydrogen is increased by manufacturing a wind turbine. The amount of solar power manufactured adds a large amount of water, most from the fabrication of silicon photovoltaic wafers.

Water as a source of life and strife: a tale of two fish, one fish, and two fish — but what the hell is the water?

There is an old joke, made famous by the writer David Foster Wallace, in which one fish says to another, “How’s the water?” The second fish asked, what the hell is water?

Having enough of the water was the greatest concern for tens of thousands of years. Some argue that too much attention is paid to water supply, and that the real priority should be making do with what is available. Indeed, progress on conservation and efficiency has been impressive — the US economy now needs much less water per dollar of output than in previous decades.

But it can only go so far. Rivers, wells and artificial reservoirs provide ample supplies for much of the world, but arid regions still struggle. Some researchers in these water-starved regions are turning their attention to the wet sponge that is the planet’s atmosphere. New technologies could extract clean fresh water from thin air, and sharply reduce water scarcity.

Water intended for drinking has to be clean and free of pollutant, no matter how abundant the supply. These chemicals, known as PFAS, are held together by several strong chemical bonds, which makes them impervious to most attempts to break them down. But engineers are devising various methods to crack them apart and purify PFAS-contaminated water.

Source: Water: a source of life and strife

Editorial: The FII Institute at the Cologne-San Francisco International Institute of Physics and Applied Physics (http://www.chi.org/abstract/slide/articles/14th edition)

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