In recent years, domestic hydrogen utilization technology has gradually developed, and production scale has continuously expanded. According to the development plan of the National Development and Reform Commission and the National Energy Administration, hydrogen energy will become an important part of the energy structure by 2050. However, the source of hydrogen is not evenly distributed, so it is necessary to transport hydrogen to the corresponding markets. There are various ways to transport hydrogen, and currently, gaseous hydrogen is still the main method. Pipeline transportation is considered a very important way to transport hydrogen.

　　Pipeline Hydrogen Transportation

　　Pipeline transportation of hydrogen refers to the construction of pipelines between hydrogen production plants and hydrogen stations, hydrogen-using units, etc., with hydrogen being transported in gaseous form. According to the transportation distance, pipeline hydrogen transportation is divided into long-distance pipelines and short-distance pipelines. The former is mainly used for long-distance transportation between hydrogen production plants and hydrogen stations, with higher hydrogen transportation pressure and larger pipe diameter. The latter is mainly used for hydrogen delivery between hydrogen stations and various users, with lower hydrogen transportation pressure and smaller pipe diameter.

　　According to the purity of hydrogen, it can also be divided into natural gas blended hydrogen pipelines and pure hydrogen pipelines. The former refers to a method used in the early stages of hydrogen energy development, where hydrogen is pressurized and input into existing natural gas pipelines, allowing hydrogen and natural gas to be transported in a mixed manner. The latter refers to pipelines specifically used for pure hydrogen transportation, but they are difficult to lay and have high investment costs, representing the ultimate goal of hydrogen pipeline network construction.

　　Large-scale, Long-distance, Low-cost

　　In the future, with the increase in hydrogen demand, the long-tube trailer transportation method will not be able to meet customer needs. Pipelines, as an important method for large-scale hydrogen transportation, have multiple advantages, including large transportation volume, long distance, low energy consumption loss, and high economic efficiency. Taking the pipeline transportation capacity utilization rate of 60% as a reference, comparing the pipeline transportation with the long-tube trailer and liquid tank truck transportation costs, the results are shown in the figure below. It can be seen that in the future long-distance, large-scale hydrogen transportation, pipeline hydrogen transportation is cost-effective and efficient, and is expected to become the optimal transportation mode.

　　Current Status of Development at Home and Abroad

　　Hydrogen pipeline transportation has a history of more than 80 years, and the total mileage of hydrogen transportation pipelines worldwide has exceeded 5000km, with the vast majority operated by hydrogen producers, mainly used for industrial raw material supply. Foreign hydrogen pipelines started earlier, with the United States and Europe being the earliest to deploy and lay hydrogen pipeline networks. Currently, the country with the most hydrogen pipelines is the United States, with a total mileage exceeding 2700km; the length of hydrogen transportation pipelines in Europe has also reached 1770km.

　　In terms of pipeline hydrogen transportation, China's research started relatively late, with a smaller scale of hydrogen pipelines and a total mileage of about 400 kilometers, with only about 100 kilometers of pipelines in use, and a transportation pressure of 4MPa. With the rapid development of hydrogen energy, China is accelerating the construction of hydrogen pipelines. Ten hydrogen pipeline construction projects have been announced, with a planned total length exceeding 1500km.

　　Hydrogen Pipeline Construction Standards

　　Many specifications and standards for hydrogen pipelines are similar to those for natural gas pipelines, but the physical properties of the two gases are quite different, so there are some differences in specifications and standards, and natural gas pipeline standards cannot be directly used for design and construction. Although China has built some hydrogen pipelines and has accumulated some experience in pipeline design, construction, operation, and maintenance, there is not yet a complete set of hydrogen pipeline standards. Relevant departments are currently compiling them, and their establishment and release are urgently needed.

　　Internationally, regarding the standards for long-distance hydrogen pipelines, there are mainly three: ASME B31.12—2014 "Hydrogen Piping Systems and Pipelines" compiled by the American Society of Mechanical Engineers, applicable to long-distance pipelines, distribution pipelines, and service pipelines transporting hydrogen from manufacturing plants to usage sites.

　　Another is CGA G-5.6—2005(R2013) "Hydrogen Piping Systems" by the Compressed Gas Association of Europe and AIGA 033/14 "Hydrogen Piping Systems" by the Asian Industrial Gases Association. The contents of these two are basically the same, both applicable to the transportation and distribution systems of pure hydrogen and hydrogen mixtures, limited to gaseous products, with a temperature range of -40~175 ℃ and a total pressure of 1~21 MPa.

　　Technology Needs Breakthrough

　　Because pipeline materials are in long-term contact with hydrogen, hydrogen will penetrate into the materials, causing metal materials to suffer damage, crack expansion speed to accelerate, and fracture toughness to decrease, thus causing risks such as hydrogen embrittlement, penetration, and leakage. Studies have shown that hydrogen pressure, purity, environmental temperature, pipeline strength level, deformation rate, and microstructure all affect the degree of pipeline damage. In addition, hydrogen also has a certain impact on related pipeline facilities, such as instruments and valves.

　　Zheng Jinyang, an academician of the Chinese Academy of Engineering, said that for large-scale commercial application of hydrogen pipeline transportation in China, there are two main technical difficulties: firstly, key technologies, including low-cost, high-strength hydrogen embrittlement resistant materials, high-performance hydrogen pipeline design and manufacturing technology, pipeline operation and control technology, and emergency and maintenance technology; secondly, the localization of related equipment, such as high-flow compressors, hydrogen metering equipment, valves, and instruments.

　　Development Trend

　　In recent years, hydrogen has become well-known as a clean energy source. Major energy powers around the world have formulated hydrogen energy development goals and strategies, with huge investment in research and development. Relevant data shows that by 2030, the hydrogen energy industry will become an important part of China's new energy strategy and a new economic growth point, and the construction mileage of high-pressure long-distance hydrogen pipelines will reach 3000km. With the development of hydrogen energy and the maturity and improvement of related technologies, large-scale centralized hydrogen production and long-distance transportation of hydrogen are future trends. Efficient and economical pipeline transportation is an important direction for the large-scale commercial development of hydrogen energy.