I wondered where the water was to come from, as hydrogen production direct from seawater is still very early stage.

The answer is that they are to desalinate it onboard (Fr):
https://fr.lhyfe.com/presse/changement-dechelle-pour-la-production-dhydrogene-offshore-le-projet-hope-et-son-consortium-selectionnes-par-la-commission-europeenne-et-soutenus-a-hauteur-de-20-me/

' Système de traitement de l’eau de mer. Ce système peu énergivore, compact, économique et capable d’utiliser la chaleur émise par l’électrolyseur, sera pour la première fois utilisé pour produire de l’hydrogène vert à partir d’eau de mer purifiée par évaporation.'

So some of the energy for desalination is to come from otherwise waste heat from the electrolyser.

The initial installation is to be close inshore, just off the coast of Belgium, where there is good hydrogen infrastructure to utilise the product.

I am particularly keen on the project backed by Ikea to release the oxygen from offshore windfarms into the Baltic sea instead of the air, so countering the oxygen depletion there.

A great ecological freebie.

They are looking at the same idea in Canada.

I liked it up to "green hydrogen [...] will be exported ashore by pipeline". A big challenge for less-than-close to shore wind is bringing the electricity ashore because wiring is expensive. I have to think a wire is cheaper and more durable than a pipeline for volatile gas. What happened to generating ammonia or hydrides and bringing them back on shore via drone boats?

Hi Alfred.

AFAIK the answer to how to bring power ashore is pretty much: 'It depends'

Here are a couple of references:

https://www.oxfordenergy.org/wpcms/wp-content/uploads/2023/11/ET27-Hydrogen-pipelines-vs.-HVDC-lines_HG_AP_2.pdf

Note in the abstract:

' Hydrogen pipelines offer the advantage of transporting larger energy volumes, but existing projects are dwarfed by the vast networks of HVDC transmission lines. '

And:
' Considering these technologies as standalone competitors belies their complementary nature. In the emerging energy landscape, they will be integral components of a complex system. Decisions on which technology to prioritize depend on factors such as existing infrastructure, adaptability, risk assessment, and social acceptance. Furthermore, while both HVDC lines and hydrogen pipelines are
expected to proliferate, other factors such as market maturity of the relevant energy vector, government policies, and regulatory frameworks around grid development and utilization are also expected to play a crucial role.'

And here:

https://www.sciencedirect.com/science/article/abs/pii/S0306261921001604

' Four different scenarios were explored. The first two scenarios evaluated the power transmission of 2 GW between two shores separated by either shallow or deep waters. Whilst the remaining two scenarios analysed the power transmission of 600 MW between an offshore platform, close to an offshore wind farm, and its hinterland, in shallow and deep waters. For bulk power transmission of electricity, the use of a high voltage direct current through submarine cables was studied. In the case of hydrogen, two transport alternatives were evaluated: hydrogen transported through pipelines and by ships in liquefied and compressed states. The findings of this study indicate that for a 2 GW power transmission and distances slightly over 1000 km in deep waters, the hydrogen transported through pipelines is cheaper than electricity, even when the electricity prices are low. Overall, among the hydrogen transport alternatives, the best solution is to transport liquefied hydrogen by ship.'

Turning the power into ammonia is pretty much only considered for longer distances, where you have to use tankers, for instance from the Arabian Gulf to Europe, as conversion to ammonia and back again, with its own issues of being very nasty to handle, takes a lot of energy and ammonia is not (?) usually piped.

The basics of transmission technology is that one hydrogen pipeline carries as much energy as several HVDC cables.

For the North Sea, existing NG pipelines ready for conversion reduces costs, so the rough guide that they are usually better for over 1,000km does not apply.

For deep sea work, ie floating offshore wind, the main line of thought is to send in hydrogen tankers to take off the product, which obviously would not be possible with electricity,

My own take is that piping hydrogen as opposed to electricity enables both far more efficient use, as it can be converted right where it is needed to electricity and heat, at stonking efficiency, and helps in storing energy, as hydrogen and its derivatives are far more storable than electricity,

And to back that up, and without wishing to show off, I must point out that I have a Chemistry 'O' Level, (1966), so expertise is not lacking, and was obtained prior to many of my critics,! :-0

Some more info here:

https://www.hydrogeninsight.com/production/europes-first-offshore-hydrogen-pilot-saw-electrolyser-performance-as-high-as-on-land/2-1-1590319

' “The performance achieved was as high as on land, confirming the reliability of the installation,” the developer said in a press release. It also confirmed to Hydrogen Insight that Plug’s electrolyser had a working range of 10-100%, meaning that it could produce H2 when the electricity input was as low as 10% of its nameplate capacity (ie, 100kW).'

However:

' Lhyfe also confirmed to Hydrogen Insight that the project only produced 15 tonnes of H2, or around a quarter of the maximum output possible, assuming full utilisation for all of the days it was producing hydrogen at sea. However, it added that the focus of the project was technical feasibility in harsh marine environments rather than maximising production.'

But it would seem that like a lot of renewable technology, nameplate capacity and actual output will be very different.