China has developed new systems to extract hydrogen from seawater and fresh water, as well as uranium, bromine and other marine resources. The special thing is that the waste heat generated during the production of hydrogen is reused in this system. Due to this, the power consumption efficiency of the system is improved by about 15 percent.

According to a study published in the journal ‘Nature Energy’, a research team from the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences has developed this system. The research team is led by Deng Dehui and Liu Yanting. Scientists have modified existing technology to produce hydrogen from seawater in a way that can reduce electricity and water consumption.

Why is it difficult to make hydrogen from sea water?

Making hydrogen from seawater with the help of renewable energy is considered as an important way to produce green hydrogen. But direct electrolysis of seawater has many problems. Chloride ions present in seawater can react with the electrode, damaging the electrode.

Apart from this, elements like calcium and magnesium deposit a layer on the electrode surface. This can reduce the efficiency of the electrolyzer and also affect the lifetime of the system.

For this reason, to make hydrogen from seawater, fresh water is usually first desalinated, that is, by separating salt and other dissolved substances from seawater. After this, hydrogen is produced by electrolysis of this water. But this method requires a separate desalination system, which increases electricity consumption.

China added electrolyzers and desalination

To overcome this problem, Chinese scientists have combined electrolyzer and desalination system together. In 2023, the research team designed a small 25 kW unit based on seawater desalination technology. Now this design has been developed on a large scale and a 250 kW plant has been constructed.

The peculiarity of this system is that the waste heat from the electrolyzer is not allowed to go to waste. In a commercial electrolyzer, large amounts of electricity are converted into heat at temperatures of about 80 to 90 degrees Celsius. Usually this heat is removed by cold water.

In a new technology, this heat has been used for desalination. The heat released during electrolysis is sent to a vacuum distillation tower. Here it is used to convert seawater into steam at a temperature of about 40 to 50 degrees Celsius. After this, the steam is cooled to prepare fresh water.

Hydrogen, water and uranium from one system

According to the Chinese Academy of Sciences, this process produces enough fresh water to run an electrolyzer. Even after this, excess water remains.

At the same time, many resources present in the thick seawater remaining after desalination can be recovered in different stages. According to scientists, apart from salt, it also contains uranium, bromine and other marine resources.

This technology is unique to uranium. The amount of uranium in seawater is very low, but the total amount in all the world’s oceans is considered to be very large. This is why scientists have long sought a cheaper and more efficient way to extract uranium from seawater.

How much hydrogen will a 250 kilowatt plant produce?

According to the research paper, this 250 kilowatt unit can produce about 3.8 lakh standard cubic meters of hydrogen per year. Its purity is said to be up to 99.9999 percent. Along with this, this system can also produce 256 tons of clean water annually.

The study found that the electricity consumption efficiency of this system improved by 14.4 percent compared to conventional alkaline water electrolysis. Scientists also tested it by running it on and off every day for 40 days. During this period, no significant decrease in system performance was observed.

How cheap can hydrogen get?

According to the research team’s cost analysis, if the cost of electricity remains at $0.033 per kilowatt-hour, which is the level of onshore wind energy, the estimated cost of hydrogen produced from this system could be around $2.1 per kilogram.

At the same time, if the cost of electricity is $0.049 per kilowatt-hour at the same level as solar energy, the cost of hydrogen is estimated to be around $2.9 per kilogram. In the study, the current price of hydrogen is assumed to be around $3.9 per kilogram.

Preparing for what to do next?

The research team will now work on developing better catalysts, using the heat generated from the electrolyzer more efficiently and improving various parameters of the entire system.

Artificial intelligence can also be used to improve system performance and energy efficiency, according to scientists. That is, this technology is not only limited to making hydrogen and clean water from sea water. It is also working to recover uranium, bromine and other resources present in the sea.