Due to the shortage of fresh water resources, asking for water from the sea is an important direction for the future development of hydrogen energy. However, the complex composition of seawater (about 92 chemical elements) has led to many problems and challenges in the production of hydrogen from seawater, and the process of hydrogen production after desalination is complex and costly.
On November 30, 2022, Xie Heping, Dean of the Institute of Deep Earth Science and Green Energy of Shenzhen University, published a paper in Nature to establish a new principle and technology of phase change migration-driven direct electrolysis of seawater without desalination by in-situ electrolysis with new ideas such as molecular diffusion and interfacial equilibrium.
This technology completely isolates seawater ions, and realizes high-efficiency in-situ direct electrolysis of seawater hydrogen production without desalination process, side reaction, and additional energy consumption, which can be directly electrolyzed in situ in seawater to produce hydrogen. At the same time, the team developed the world's first set of 400 liters/hour seawater in-situ direct electrolysis hydrogen production technology and equipment.
After the publication of the paper, it caused a shock around the world, and the technology was also selected as one of the "Top Ten Advances in Chinese Science in 2022" organized by the Ministry of Science and Technology.
At the China Carbon Neutral Energy Summit Forum and the 3rd China International Conference on New Energy Storage Technology and Engineering Application held on September 10, 2023, Xie Heping revealed that just 20 days after the paper was published last year, on December 16 last year, the team signed a cooperation agreement with Dongfang Electric Group. Dongfang Electric invested 30 million yuan in special funds to obtain the intellectual property rights of original technology patents and related materials shared by the four parties, and formed an alliance to carry out offshore pilot and engineering demonstration and industrialization of seawater direct electrolysis hydrogen production technology.
"After the publication of the paper, the international market has paid extensive attention to the principle technology, and many international enterprises want to purchase our hydrogen production unit, but require us to provide technical drawings, operating parameters and detailed technical solutions. However, we believe that the intellectual property rights of this original technology should be in Chinese hands, and we should take the lead in piloting, project demonstration/industrialization, and the formation of an industrial chain, which also prompted me to realize my dream of sea trials as soon as possible. Xie Heping said.
Xie Heping introduced that in order to adapt to the uncontrollable typhoons and waves of the ocean, the team established an expansion model and control system based on new principles, and jointly designed a floating seawater hydrogen production platform with Dongfang Electric Group, in May this year, the team carried out a successful sea trial of 1.2 Nm3/h seawater in-situ direct electrolysis hydrogen production in Xinghua Bay, Fuqing City, Fujian Province, creating the world's first offshore wind power seawater direct electrolysis hydrogen production technology demonstration project.
"This is the first time that the new principle technology of direct hydrogen production from seawater is docked with offshore green power, and the on-site verification of the real marine environment has been successfully carried out, and the effect is similar to that of the laboratory under the strong interference of 3-8 level winds and 0.3-0.9 meters wave strong interference, with a scale of 1.2Nm3 H2/h and 5kWh/Nm3 H2 electrolytic energy consumption." Xie Heping said.
On July 6, 2023, at the "Mainland Original Offshore Wind Power Direct Hydrogen Production Principle Technology without Desalinated Seawater" large-scale and industrialization strategic consultation seminar held by the Chinese Academy of Engineering, the participating academicians affirmed the results of the sea trial.
Speaking of the cost that the outside world is particularly concerned about, in his speech at the conference, Xie Heping said that because the direct hydrogen production of seawater can be directly connected to renewable energy such as offshore wind power, there is no seawater desalination process, no additional catalyst engineering, no seawater pumping and transportation process, no seawater pollution treatment process, no seawater hydrogen production equipment platform, so the future has great economic potential.
According to the formula of "direct hydrogen production cost of seawater = electricity price× unit electricity consumption + (annual depreciation + annual operation and maintenance) / total annual hydrogen production", based on the on-grid electricity price of offshore wind power 0.2 yuan - 0.3 yuan / kWh, the unit mass hydrogen cost of direct hydrogen production from seawater is 0.219 yuan/Nm3+0.2 yuan/Nm3+(1-1.5) yuan/Nm3=1.419-1.919 yuan/Nm3 = 15.89-21.49 yuan/kg.
Compared with the cost of hydrogen production from fresh water on land, the cost of direct hydrogen production from direct electrolysis of seawater is comparable to the former (no floor space and other facilities and pollutant treatment costs).
Further cost reduction in the future comes from two aspects - the reduction of energy consumption for direct hydrogen production by direct electrolysis of seawater and the reduction of offshore wind power prices. According to Xie Heping's calculation, based on the current direct electrolysis of seawater electricity consumption of 5kWh/Nm3 hydrogen, when the electricity price is lower than 0.09 yuan / kWh, the comprehensive cost is expected to be lower than 0.87 yuan / Nm3 hydrogen (the lower limit of the cost of coal-to-gray hydrogen). At present, the team has tackled the second generation of technology, so that the technical energy consumption is reduced to 4.5kWh/Nm3, and when the energy consumption of electrolysis hydrogen production is reduced to 4.0 kWh/Nm3, when the electricity price is lower than 0.11 yuan/kWh, the cost of hydrogen production from seawater direct electrode will be lower than 0.87 yuan/Nm3 (the limit low price of coal-to-gray hydrogen).
In addition, when the offshore wind power price is lower than 0.23 yuan / kWh, the cost of seawater hydrogen production has a competitive advantage compared with coal hydrogen production + CCUS; When the electricity price is lower than 0.15 yuan / kWh, the hydrogen production from seawater is equivalent to the coal to gray hydrogen; When the electricity price is lower than 0.11 yuan / kWh, the cost of hydrogen production from seawater will be completely lower than the cost of coal to gray hydrogen.
"This will change the world's energy landscape." Xie Heping said.
Reflections on the industrialization of future technologies
When talking about the future technology and industrialization trend, Xie Heping said that on the one hand, the team will iteratively upgrade the principle technology. This includes new principle upgrades for alkaline electrolyzers (AWE) and new principles for acid submembrane electrolyzers (PEMs).
On the other hand, the team will also iteratively upgrade the hydrogen production platform technology, including the establishment of floating seawater direct hydrogen production platform technology (large and medium-sized), fixed seawater direct hydrogen production platform technology, and powered seawater direct hydrogen production vessel technology (large tonnage).
In terms of the construction of the upstream and downstream industrial chains of the industrial chain, Xie Heping pointed out three paths. The first is to cooperate with the Ding Wenjiang team of Shanghai Jiao Tong University to build an industrial chain of "seawater hydrogen production + magnesium-based solid, storage, transportation and use technology".
Secondly, his team will work with the team of Academician Zhang Qingjie of the National Key Laboratory of Energy Hydrogen Energy and Ammonia-Hydrogen Fusion New Energy Technology to build a "seawater hydrogen production + hydrogen-ammonia integration" technology industrial chain, that is, directly using seawater to produce hydrogen, while converting it into stored and transported ammonia fuel on site, and completing the transportation/consumption of ammonia through ammonia carriers (existing) or ammonia fuel ships (future), so as to realize the carbon-free hydrogen-ammonia cycle driven by offshore renewable energy, and ammonia-hydrogen fusion (ammonia hydrogen and ammonia hydrogen are used together).
Thirdly, in the future, we can also build an industrial chain of "seawater hydrogen production + green methanol integration" technology, that is, directly use seawater to produce hydrogen, capture carbon dioxide through the air, convert it into methanol fuel on site, complete the transportation/consumption of green methanol through existing oil and gas pipelines at sea or methanol-powered ships or methanol carriers, realize the conversion of carbon-negative "hydrogen → green methanol" driven by offshore renewable energy, and provide an important carrier for fuel-powered vehicles, synthetic fibers, plastics, pesticides, fuel, synthetic proteins, etc.
In addition to these three paths, the team will continue to make efforts in the new industrial chain of personalized equipment manufacturing for direct hydrogen production from seawater, develop and tackle new renewable energy technologies such as personalized offshore wind turbines, and dock new technical equipment for large-scale "fixed", "powered" and "floating" seawater direct hydrogen production operation platforms, and strive to lead the global "marine green hydrogen" industry chain.
Xie's ambitions did not stop there, and at the end of his speech, he put forward the idea of "providing a bay to build a large-scale R&D and pilot demonstration base". According to Xie Heping, on July 20, 2023, his team has met with representatives of the Quanzhou Municipal Party Committee to negotiate the industrialization of Quanzhou.