Status and Development of Large scale Water Electrolysis Hydrogen Production Technology

With the large-scale use of coal and petroleum energy, the impact of global climate change is increasingly significant, which will cause a huge crisis to human society and development. Therefore, reducing greenhouse gas and other harmful gas emissions from fossil energy use has become the consensus and focus of the international community. At the 2020 Paris Climate Change Conference, the Chinese government made a commitment and put forward its own "double carbon target", that is, to strive to reach the peak of carbon dioxide emissions by 2030, and strive to achieve the ambitious goal of carbon neutrality by 2060 [1].

Hydrogen energy has the characteristics of large energy density, high calorific value, rich reserves, extensive sources, high conversion efficiency, and generates water after combustion. Hydrogen can be used as a high-efficient energy storage carrier with various storage methods and utilization forms. Hydrogen energy is an effective solution to achieve large-scale long-term storage of renewable energy, which is considered by experts and scholars as one of the most promising energy sources and has been highly concerned by people [2].

At present, hydrogen is generally divided into gray hydrogen, blue hydrogen and green hydrogen according to whether there is carbon dioxide emission in the hydrogen production process. Ash hydrogen is produced and emitted carbon dioxide in the process of production, such as hydrogen production from coal, coal gasification, hydrogen production from natural gas or industrial by-product hydrogen; Blue hydrogen is produced in the process of production but does not emit carbon dioxide, that is, carbon capture and carbon sequestration are carried out for the emitted carbon dioxide, which also includes hydrogen production from fossil energy, but there will be costs in the process of carbon capture and sequestration, such as turning into solid carbon black in the process of methane cracking to obtain hydrogen; Green hydrogen is produced from renewable energy (such as geothermal energy, biomass, marine energy, wind power, photovoltaic solar energy and solid waste). There is no carbon emission in the process of hydrogen production. In 2021, China's hydrogen output will be about 33 million tons, ranking first in the world. According to the analysis of hydrogen sources, 62% of the hydrogen will be produced from coal, 19% from natural gas, 18% from industrial by-products, and only 1% from electrolytic water [3-4]. From these data, the proportion of green hydrogen is relatively low.

Water electrolysis is the main way to produce green hydrogen, a necessary technology for the development of hydrogen energy [5], and an important pillar to achieve the goal of "double carbon". With the continuous promotion and deepening of the "dual carbon" policy, the reduction of the cost of renewable energy power, the large-scale promotion of hydrogen fuel cell vehicles and the gradual maturity of the hydrogen energy market, the market demand for hydrogen will grow explosively. However, the production of green hydrogen through water electrolysis technology will be the mainstream direction of the future low-carbon economy, the only way for the development of hydrogen energy, and the main source of hydrogen.

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  Hydrogen production by water electrolysis is the key technology to produce green hydrogen. Hydrogen production by water electrolysis is an electrochemical process that decomposes water into hydrogen and oxygen [6]. At present, water electrolysis hydrogen production can be divided into alkaline water electrolysis hydrogen production technology (ALK, Alkaline Electrolysis), proton exchange membrane hydrogen production technology (PEM, Proton Exchange Membrane Electrolysis) and solid oxide water electrolysis hydrogen production technology (SOEC, Solid Oxide Electrolysis) according to the different electrolytic membranes. The comparative analysis of the three water electrolysis hydrogen production technologies is shown in the following table1。

At present, in domestic and international markets, large-scale water electrolysis hydrogen production technology mainly adopts alkaline water electrolysis hydrogen production technology and proton exchange membrane electrolysis hydrogen production technology. During the transformation of hydrogen energy to energy level, the equipment produced by large-scale water electrolysis hydrogen production technology has the advantages of large scale, high efficiency, small floor area, low cost of hydrogen energy, etc. It has always been a hot spot for global enterprises and scientific research institutions in the continuous research and development of electrolytic water hydrogen production technology [7]. For water electrolysis hydrogen production technology with hydrogen production capacity of more than 1000 Nm3/h in a single tank, the domestic manufacturers that have mastered alkaline large-scale water electrolysis hydrogen production technology and equipment include Perui Hydrogen Energy Co., Ltd. of the 718 Research Institute of China Shipbuilding Group, Cocklell Jingli (Suzhou) Hydrogen Energy Technology Co., Ltd., Tianjin Continental Hydrogen Production Equipment Co., Ltd., Longji Hydrogen Energy Technology Co., Ltd., Yangzhou Jidao Energy Co., Ltd., etc, Many enterprises make China's alkaline large-scale water electrolysis hydrogen production technology have a certain cost advantage in the international market, but the proton exchange membrane electrolysis hydrogen production equipment still lags behind Europe, America, Japan and South Korea. Global proton exchange membrane electrolysis hydrogen production equipment manufacturers whose single tank is higher than 1000 Nm3/h include Cummins.

2.1 Large scale alkaline water electrolysis hydrogen production technology

Perui Hydrogen Energy: the hydrogen production capacity of a single alkaline water electrolysis hydrogen production equipment developed can reach 2000 Nm3/h, the hydrogen production station layout is adopted, the bipolar filter pressing structure is adopted, and the sealing performance of the insulating sealing gasket is strong; The silicon rectifier is used to replace the original silicon controlled rectifier, which reduces the harmonic interference to the power grid during the operation of the device, effectively eliminates the high harmonic pollution to the power grid, and reduces the reactive power loss; Before purification, the hydrogen purity of the product reaches 99.8%, and the oxygen purity reaches 99.2%. After purification, the hydrogen purity of the product can reach 99.999%. In 2021, the first 1000 Nm3/h large-scale water electrolysis hydrogen production equipment produced by the company will be successfully delivered to the Winter Olympics, with low energy consumption and superior safety performance. High efficiency hydrogen production will be used for hydrogen injection of fuel cell vehicles in the Winter Olympics park and surrounding areas.

Cauclea Competitive: The 1300 Nm3/h electrolytic cell jointly developed with Huaneng Qingneng Institute, Huaneng Sichuan Company and Huaneng Sichuan Hydrogen Energy Company has carried out innovation in the aspects of point, area and body in the key technology research and development, core component design, whole system assembly and integration of large-scale, high current density, pressure alkaline water electrolysis hydrogen production, and achieved many important technological breakthroughs. The key "point" of efficient catalyst synthesis was broken through, and a new nickel based multi-component alloy catalyst layer was constructed, effectively improving the working current density and reducing the hydrogen evolution potential. It has broken through the analysis and structure optimization of the three-phase key interface, overturned the traditional plate flow field structure, optimized the horizontal and vertical dimensional space layout of the electrolytic cell, and realized the efficient transfer of heat and material. It breaks through the whole "body" reliable assembly of large high-density electrolytic cells, and improves the high-voltage sealing, performance uniformity and operation reliability of electrolytic cells. The 1000 Nm3/h alkaline large-scale water electrolysis hydrogen production equipment supplied to Baofeng Energy is the world's first set with a capacity of 1300 Nm3/h, and the maximum capacity can reach 1500 Nm3/h, meeting 20%~115% frequency modulation hydrogen production. The current density of large-scale internationally commercialized water electrolysis hydrogen production equipment reaches 6000 A/m2 for the first time, and the main control system adopts domestic PLC. The equipment has also broken the world record of hydrogen production from a single alkaline electrolytic cell, and is stable under full load.

Cockerell Jingli has been conducting in-depth research on reducing contact resistance, optimizing electrode materials, improving current density and reducing energy consumption. At present, the DC power consumption of the large alkaline water electrolysis equipment produced by the enterprise is 4.13 kW · h/m3 hydrogen, which is better than the first level of 4.3 kW · h/m3 hydrogen in the national mandatory standard Energy Efficiency Limits and Energy Consumption Grades of Water Electrolytic Hydrogen Production System. It has achieved a leap in current density from 2000 A/m2 to 4000 A/m2. Under the condition of quick start, the equipment can run at full load in one minute, and the conversion rate of current, voltage and AC/DC can reach 98.5%. At present, we have also realized the interconnection of IOT electrolyzer control equipment, terminal intelligence and remote monitoring, which we can achieve, and meet the purity requirements of 5 A. Non asbestos diaphragm is also used, and non-contact electrolysis mode is used to improve the electrolysis efficiency, ensure that the current density can reach 6085~6086 A, and the long-term operation is stable. With the further development of hydrogen energy, Kawkael has become more integrated and more large-scale, efficient and intensive. Continental hydrogen production: It is a professional manufacturer of discrete circulating water electrolysis hydrogen production technology in China. It has 1000 Nm3/h large-scale alkaline water electrolysis hydrogen production equipment. The highest operating pressure hydrogen production equipment is 5.0 MPa, and its products are sold well all over the world.

Sungrow Hydrogen Energy: The company has independently developed 1000 Nm3/h large-scale alkaline water electrolysis hydrogen production equipment, and the corresponding electrolysis hydrogen production equipment of the megawatt proton exchange membrane hydrogen production system. It has built a test platform for the electrolysis water hydrogen production system to meet the test requirements of 1000~3000 standard cubic meters of hydrogen production system. Sungrow hydrogen energy large-scale water electrolysis hydrogen production equipment is being applied to the "North China Hydrogen Valley" project in Baicheng City, Jilin Province.

Yangzhou Jidao Energy Co., Ltd.: released the first set of pressurized shell type single tank hydrogen production equipment with the largest capacity for hydrolysis and successfully went offline. It was jointly developed by Jidao Energy, Dalian University of Technology, Zhongke Liquid Sunshine Suzhou Company and other units. It has made breakthroughs in water electrolysis equipment structure, electrolyte distribution, catalyst, temperature control and other aspects, and has independent intellectual property rights, It is the first commercial alkaline water electrolysis hydrogen production equipment of outdoor safe explosion-proof type. The hydrogen production capacity of the electrolytic hydrogen production equipment is 1350 Nm3/h, the maximum is 1500 Nm3/h, the pressure is 2.5 MPa, the land is saved by 50%, the plant is 90%, and it has a number of international leading key indicators. At the same time, it also forms the following advantages: the complete set of technology of outdoor safe pressure shell electrolyzer, large-scale high pressure water electrolysis technology, the unit equipment investment can be reduced by 20%, the DC energy consumption is lower than 4.2 kW · h/m3 hydrogen, which is significantly superior to the national first level energy efficiency standard; The equipment will be used in hydrogen generation and energy storage power plants, which will be connected to the power grid for control and realize functions such as one key start, unattended, remote monitoring, equipment interconnection, etc; The circulation distribution technology of multiple electrolytic chambers is adopted, so the operation of the electrolytic cell is more stable, and the system kinetic energy is reduced by 10%; Electrolysis equipment adopts leakage prevention online detection technology, tank body automatic cleaning technology and internal circuit cooling technology. The release of this large-scale water electrolysis hydrogen production equipment marks that China has successfully mastered the key technology of high-performance alkaline large-scale hydrogen production. Next, Kyodo Energy will start the development of 3.5 MPa, 2000 Nm3/h large-scale electrolytic cell.

Longji Hydrogen Energy: The large-scale alkaline water electrolysis hydrogen production equipment successfully launched adopts modular and high current density design. The hydrogen production capacity of a single commercial large-scale alkaline water electrolysis hydrogen production equipment reaches more than 1000 Nm3/h. The design of non asbestos mesh is more environmentally friendly. At the same time, "multiple large-scale electrolytic cells correspond to a set of gas-liquid separation system and gas purification system" is taken into account, which improves the intensification of large-scale hydrogen production plants. The distributed IO control system is not only highly integrated and material saving, but also capable of fully automatic unattended and efficient operation of the system.

The cost of hydrogen production by water electrolysis is a key factor in the transformation of green hydrogen from industrial to energy level, and there are three main technical paths to reduce the cost:

The first is large-scale, including the large-scale and modularization of single water electrolysis hydrogen production equipment. The hydrogen production capacity of large domestic alkaline water electrolysis hydrogen production equipment has reached 1000 cubic meters through improving materials, multiple tanks corresponding to a set of purification, container integrated modularization and other aspects, and has been applied in green hydrogen projects and demonstration projects. However, the proton exchange membrane water electrolysis hydrogen production equipment can produce 100 cubic meters of hydrogen. Modularization is a system with multiple water electrolysis hydrogen production equipment. For example, a project in Germany can reach 4000 Nm3/h, which is composed of eight 500 Nm3/h water electrolysis hydrogen production equipment.

The second is to reduce power consumption. The reduction of electricity consumption brings about hydrogen production by water electrolysis, but the reduction of hydrogen production cost has significant advantages. Research institutions and enterprises are actively promoting the reduction of electricity consumption, mainly focusing on materials, high current density and large size electrodes, diaphragms, etc. Reducing power consumption involves materials, structures and other disciplines, as well as the impact of processing means and other links. At present, there is no innovative indicator plan in China, so it is very difficult to reduce power consumption.

Due to the ceiling of current density in alkaline water electrolysis hydrogen production technology, the efficiency of alkaline water electrolysis hydrogen production has reached a bottleneck; However, proton exchange membrane water electrolysis hydrogen production can easily break through the upper limit of current density, and can further increase, and the hot start cold start speed is faster. Pure water is used without the cost of later alkali recovery and pollution control, on this basis, the cost of hydrogen production is reduced.

Third, the combination with renewable energy. Renewable energy has three characteristics: intermittency, fluctuation and seasonality (especially hydropower, wind power and photoelectric). Under the dual carbon background and the development idea of integration of wind, solar and hydrogen storage, hydrogen is the main means of energy storage and peak shaving. The larger the capacity of large-scale water electrolysis hydrogen production to adapt to the three characteristics of renewable energy sources, the more advanced the technology, the higher the efficiency of green hydrogen production, and the rapid response of key systems to the fluctuations of renewable energy. At present, domestic enterprises have achieved second level response, that is, they can start and stop within one second. Large alkaline water electrolysis hydrogen production equipment can adapt to renewable energy from 20% to 100%. Large proton exchange membrane water electrolysis hydrogen production equipment is more efficient and has achieved full coverage.