Currently, the call for global energy transformation is getting stronger and stronger. In this context, hydrogen energy, as a clean, low-carbon, flexible and efficient energy source with a wide range of sources and diverse applications, has gained opportunities for explosive growth. However, there are still many bottlenecks that need to be overcome to achieve large-scale development of the hydrogen energy industry, and this is becoming a new opportunity for the chemical industry.
Problems under explosive growth
According to predictions from the International Hydrogen Council, by 2050, hydrogen energy will meet 18% of global end-use energy demand and reduce carbon dioxide emissions by 6 billion tons. In view of this, in recent years, about 80 countries around the world have proposed hydrogen energy development plans, using hydrogen energy as an important component of decarbonized energy and a new engine for green economic recovery. For example, the United States has released a national clean hydrogen energy strategy roadmap to accelerate the production, processing, delivery, storage and use of clean hydrogen; Germany has released a new version of the "National Hydrogen Energy Strategy" and plans to transform and build more than 1,800,000 hydrogen energy plants by 2027 or 2028. meters of hydrogen pipeline to double Germany’s electrolysis hydrogen capacity by 2030.
In my country, the National Development and Reform Commission officially released the "Mid- and Long-term Plan for Hydrogen Energy Industry Development (2021-2035)" in 2022 and pointed out that by 2050, the demand for hydrogen will be close to 60 million tons, and carbon dioxide emissions will be reduced by about 700 million tons. tons, hydrogen energy accounts for more than 10% of my country's terminal energy system, and the annual output value of the industry chain reaches 12 trillion yuan.
However, affected by multiple factors such as the high cost of hydrogen energy preparation, storage, transportation and use, insufficient supporting infrastructure, and the disconnect between production and demand, behind the hot track, the development bottleneck of the hydrogen energy industry cannot be underestimated.
In the hydrogen production process, the current mainstream hydrogen production methods are mainly hydrogen production from fossil energy and hydrogen production from industrial by-products. The technology is mature and the cost is relatively low, but there is a problem of carbon emissions; hydrogen production through water electrolysis can be carbon-free. The hydrogen produced and discharged has high purity, but it faces problems such as high power consumption and high capital investment. In the hydrogen storage and transportation link, safety and efficiency restrict the development of the industry. Hydrogen energy practitioners urgently need to accelerate the hydrogen energy industry through the promotion and application of new materials and new technologies.
How far is green hydrogen from being produced on a large scale?
At present, hydrogen energy can be divided into green hydrogen, blue hydrogen and gray hydrogen. Green hydrogen is hydrogen produced by using renewable energy. There are basically no carbon emissions during the production process, so this type of hydrogen is also called "zero carbon hydrogen"; gray hydrogen is produced by fossil fuels (coal, oil, natural gas, etc.) Hydrogen produced by combustion has lower production costs and the highest carbon emissions; blue hydrogen is based on gray hydrogen and applies carbon capture, utilization and storage technology to achieve low-carbon hydrogen production.
From the perspective of production structure, gray hydrogen currently produced by fossil energy accounts for a relatively high proportion. In 2021, global gray hydrogen will account for 99%. Blue hydrogen and green hydrogen will account for less than 1%. Green hydrogen will account for only 0.04% globally. . It is an inevitable trend to promote the transformation of hydrogen production from fossil energy and industrial by-product hydrogen to hydrogen production by electrolysis of water (green hydrogen).
For green hydrogen preparation, breakthrough in core technology is a top priority. Currently, green hydrogen preparation technology still has shortcomings in terms of key materials and hydrogen production costs.
Green hydrogen production technologies include alkaline water electrolysis technology (AEL), proton exchange membrane water electrolysis technology (PEM), anion exchange membrane water electrolysis technology (AEM) and other hydrogen production technologies.
Among them, AEL is the most mature and widely used, and it occupies the leading position in hydrogen production by electrolysis of water in China and even the world. The principle of AEL is to pass direct current into a high-concentration alkaline solution, and water molecules undergo electrochemical reactions on the electrodes to generate hydrogen and oxygen. In order to ensure the separation of reaction products, AEL needs to set up a porous structure separator between the anode and cathode of the electrolyzer, thus limiting the operation of the equipment under pressure conditions. Compared with AEL, PEM has the advantages of large current density, high hydrogen purity, and fast response speed. However, because the PEM electrolyzer needs to operate in a highly acidic and highly oxidizing working environment, the equipment is not suitable for expensive metal materials (such as Iridium, platinum, titanium, etc.) are more dependent and costly. At present, the global market for hydrogen production by electrolysis of water is basically divided between AEL and PEM, which account for about 80% and 20% respectively.
AEM is a relatively new technology. The structure of the AEM electrolyzer is similar to that of PEM: a solid polymer anion exchange membrane that can conduct hydroxide ions (OH-) is used as the electrolyte. Two electrodes are located on both sides of the membrane, and a catalyst is coated on them. The electrolyte can be pure Water or weakly alkaline solution. Unlike PEM, AEM's electrolyzer can rely on non-noble metal catalysts such as nickel-based, thus effectively reducing material costs. Compared with AEL, AEM equipment has smaller size, higher current density, fast dynamic response, and can better adapt to the volatility of renewable energy power generation. Therefore, AEM combines the dual advantages of alkaline low cost and high efficiency of pure water. It is one of the more cutting-edge water electrolysis technologies at present and one of the preferred technologies for large-scale application of green hydrogen in the future.
However, AEM has not yet achieved industrialization. The reason is that its biggest development bottleneck lies in the research and development of key materials, especially anion exchange membranes.
The anion exchange membrane is the core component of the AEM electrolyzer. The performance of the membrane directly affects the stability, lifespan, operating efficiency and production cost of the AEM electrolyzer. Currently, the pain points in the development of AEM membranes include chemical resistance, low hydroxide ion conductivity, low current density, and chemical stability.Poor performance and inability to balance performance and service life. Only a few companies and universities around the world are researching and developing AEM membranes, and the specialty chemical company Evonik is one of them. The company is developing an anion exchange membrane called DURAION® that achieves the quality triangle of the membrane electrolysis process, which is a balance of chemical stability, mechanical integrity and ionic conductivity. On this basis, Evonik is also cooperating with other companies in the industry, including scientific research institutions, electrolyser developers, energy companies, etc., to promote the development of a complete electrolysis system. Currently, Evonik and its partners have conducted thousands of hours of operational testing on DURAION® ion exchange membranes. DURAION® has demonstrated excellent conductivity and stability, paving the way for large-scale deployment and adoption of the breakthrough AEM process. the way.
In the future, with the continuous innovation of related materials, the cost of preparing green hydrogen is expected to continue to decrease, and then with the increase in scale, it will eventually become popular.
Finding the optimal route for hydrogen energy storage and transportation
At present, the resource side and market side of hydrogen energy are extremely unbalanced, requiring large-scale storage and transportation deployment. Hydrogen storage and transportation costs account for approximately 30%-40% of the entire hydrogen energy industry chain, affecting the cost reduction space and large-scale development of hydrogen energy.
The energy density per unit mass of hydrogen is extremely high, but the energy density per unit volume is very low. It is also flammable, explosive and prone to leakage, which brings many challenges to the storage and transportation of hydrogen.
In terms of hydrogen storage, high-pressure gaseous hydrogen storage is one of the most mature hydrogen storage technologies. It has the characteristics of low cost, low energy consumption, easy dehydrogenation, and wide working conditions. At present, high-pressure hydrogen storage containers are mainly divided into pure steel metal bottles (Type I), steel liner fiber circumferentially wound bottles (Type II), aluminum liner fiber fully wound bottles (Type III) and plastic liner fiber wound bottles. Bottles (Type IV) 4 types. The latter three use pressure-resistant containers of composite materials to eliminate unsafe factors such as hydrogen leakage and container explosion. Among them, type IV bottles are the lightest and suitable for vehicle mounting. They are the mainstream technical route for the development of future vehicle hydrogen storage systems.
The inner bladder is one of the core components of this hydrogen storage bottle. It needs to have hydrogen permeability and heat resistance, good high and low temperature mechanical properties, and good processability. High-performance fiber composite materials are important reinforcements for cylinder shells and require high-performance curing agents to provide core material properties. Evonik's amine curing agents VESTAMIN® and Ancamine® for epoxy systems can quickly soak into fibers and have excellent mechanical properties, durability and high molding efficiency, which can meet the stringent performance requirements of high-pressure hydrogen storage containers in practical applications.
Liquid hydrogen has a high volumetric energy density, can realize large-scale, long-distance hydrogen transportation, and has significant advantages for transoceanic transportation and international hydrogen trade. The process of directly liquefying hydrogen at low temperature consumes high energy and suffers from hydrogen evaporation loss and safety issues. Liquid organic hydrogen storage (Liquid organic hydrogen Carrier (LOHC) technology stores hydrogen in unsaturated liquid organic matter and realizes storage and release of hydrogen through reversible hydrogenation and dehydrogenation reactions. It has the characteristics of large hydrogen storage capacity and safe hydrogen transportation under normal temperature and pressure. At present, Germany and Japan are at the forefront of the development and application of LOHC technology. Representative companies include Hydrogenious of Germany. LOHC Technologies, Chiyoda Corporation of Japan, etc.
The performance of the catalyst in the dehydrogenation reaction determines the conversion efficiency and hydrogen purity of the hydrogen release process, and is one of the cores of LOHC technology. To this end, Evonik is working with Hydrogenious LOHC Technologies collaborate to develop and commercialize new high-performance catalysts.
In terms of hydrogen transportation, pipeline transportation is a more cost-effective way to transport large-scale, long-distance hydrogen energy. Using existing natural gas pipelines to mix hydrogen and building new pure hydrogen pipelines to transport hydrogen are both realistic and feasible solutions.
The main challenge facing hydrogen pipelines is hydrogen corrosion of the material. Existing gas pipelines are usually made of metal materials, and their performance will deteriorate in high-pressure environments with high concentrations of hydrogen, leading to problems such as hydrogen embrittlement and gas leakage. Therefore, the current research direction of hydrogen pipelines is mainly fiber-reinforced polymer materials. Non-metallic flexible pipes made of polymer materials are lightweight, high-strength, corrosion-resistant, and have a continuous structure that can produce longer pipe sections. The use of an all-polymer structure ensures that the pipeline will not produce hydrogen embrittlement under higher pressures, significantly reducing the risk of hydrogen leakage.
Evonik VESTAMID® NRG Series polyamide 12 (PA12) has high chemical resistance and outstanding mechanical properties. Thanks to its excellent hydrogen compatibility and low hydrogen permeability, Evonik VESTAMID® NRG The series can be used in various hydrogen energy fields, such as hydrogen pipelines of various structures. Powered by Evonik VESTAMID® The non-metallic flexible hydrogen pipeline manufactured by NRG can solve the problems faced by traditional metal hydrogen pipeline materials and provide a safer and more efficient material solution for the hydrogen storage and transportation industry.
After the natural gas mixed with hydrogen reaches the terminal, it also faces the challenge of separating the hydrogen in the pipeline. Likewise, SEPURAN® developed by Evonik Noble gas separation membrane can efficiently extract hydrogen from natural gas pipelines transporting methane-hydrogen mixed gas. Depending on the actual situation, 10%-30% hydrogen can be concentrated into high-purity hydrogen, with a purity of more than 90%. In addition, SEPURAN® Noble gas separation membranes also have the advantages of simple operation, quick start-up, small footprint, easy expansion, and can be plug-and-play through a simple modular setup.
The chemical industry plays a vital role in empowering the hydrogen energy industry chain and will continue to promote the rapid development of the hydrogen energy industry in the future. Many new materials and technologies will be used in the growth of the hydrogen energy industry to shoulder the important task of energy transformation and low-carbon development.
With the advantages of small floor area and easy expansion, it can be plug-and-play through simple modular setup.The chemical industry plays a vital role in empowering the hydrogen energy industry chain and will continue to promote the rapid development of the hydrogen energy industry in the future. Many new materials and technologies will be used in the growth of the hydrogen energy industry to shoulder the important task of energy transformation and low-carbon development.
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