Chinese scientists produce green hydrogen directly from seawater at floating offshore pilot project

Electrolysers usually require purified water to ensure that the electrodes are not contaminated when splitting H₂O into hydrogen and oxygen — and desalination equipment is usually factored into green H₂ projects that need to source their water from the sea.

The floating platform — which includes in-situ electrolysis, as well as “intelligent energy conversion management”, safety detection and control systems — was said to have produced hydrogen in a “stable” fashion for more than 240 hours at the Xinghua Bay offshore wind farm, off Fujian province, despite enduring gale-force winds, one-metre high waves and a rainstorm, according to China’s English-language news channel CGTN.

While the new technology could remove the need for desalination, the removal of salt and other substances and microorganisms from seawater by reverse osmosis is relatively inexpensive, costing about 0.035kWh of electricity per kilogram of hydrogen — a fraction of the 50-65kWh/kgH₂ needed by electrolysers, according to Paul Martin of the Hydrogen Science Coalition.

Nevertheless, the Chinese technology removes the need to build onshore desalination plants, and means that hydrogen could be produced directly offshore using power from nearby wind turbines, and then pumped to shore via pipeline, which could be a cheaper option than sending offshore wind power along subsea electricity cables and producing green H₂ onshore.

Germany, for instance, has set aside North Sea acreage for 1GW of green hydrogen to be produced offshore and pumped onshore via pipeline, while the Netherlands has promised to hold a tender for a 500MW offshore green hydrogen project that will also see its H₂ pumped to shore via pipeline.

The Chinese technology, which was jointly developed by Dongfang and the Chinese Academy of Engineering, was detailed in a study published in the journal Nature on 30 November last year.