Chinese pilot uses electrolysis heat to make fresh water alongside hydrogen

Making hydrogen with seawater does not necessarily mean exposing electrodes to salt. A team at the Dalian Institute of Chemical Physics in China coupled water electrolysis to a desalination stage heated by the process itself. The experimental system produces both hydrogen and fresh water. It is not direct electrolysis of seawater, which can corrode electrodes and trigger unwanted reactions.

In alkaline electrolysis, electric current splits water into hydrogen and oxygen while some of the energy becomes low-temperature heat. The design uses that heat to distill seawater under reduced pressure, allowing water to evaporate at a lower temperature. Condensed vapor supplies fresh water to the electrolyzer and can also be delivered as a separate product. Salt remains in a concentrated stream; the prospect of recovering resources from this brine does not show that such recovery is already commercially operating.

The Chinese Academy of Sciences describes a first 20-kilowatt pilot that ran for 100 days. It produced 3.8 normal cubic meters of hydrogen per hour — volume specified at standardized temperature and pressure — as well as 1.2 kilograms of fresh water per hour. A system scaled to 250 kilowatts reached 48 normal cubic meters of hydrogen and 31.6 kilograms of fresh water per hour. These flow rates refer to different systems; the 100-day test is not evidence that the larger version operated for that long. The institute’s original Chinese-language announcement says the larger unit was built in August 2024 and ran for more than 40 days. The September 2026 news is the publication of the scientific analysis, not the inauguration of a new machine.

In the researchers’ reported comparison, the integrated system’s electrical efficiency improved by 14.4% relative to conventional alkaline electrolysis fed only with fresh water. This is a relative gain in the measure used by the study, not an absolute efficiency of 14.4%, nor a demonstrated reduction of the same size in cost or emissions. Shang Jiang and colleagues published the work in Nature Energy on September 15, 2026; the academy’s English-language announcement followed the next day.

The advance combines two established operations to recover a stream of heat that would otherwise be lost. The demonstration establishes reported output rates and an electrical comparison under the conditions tested. It does not yet establish economic viability with different seawater sources, brine management or the larger unit’s service life. Hydrogen will only be low-emission if the electricity supply is suitable too, something production rates alone cannot settle. This remains an engineering route under test, not a commercial plant extracting hydrogen directly from the sea.