Solid-state hydrogen storage has become a major focus in the research and development efforts of hydrogen energy companies

Solid-state hydrogen storage can not only significantly increase the volume density of hydrogen storage but also enhance the safety of storing and transporting hydrogen. It addresses the two most critical issues related to hydrogen energy: high-density storage and safe application. With the rapid development of the hydrogen energy industry in China, this technology has attracted many companies to get involved. In terms of implementation methods, solid-state hydrogen storage is mainly divided into physical adsorption and chemical hydride storage. The former absorbs hydrogen through the physical properties of carbon-based materials such as activated carbon, carbon nanotubes, and carbon nanofibers, while materials with microporous frameworks like metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) capture and store hydrogen. Chemical hydrogen storage utilizes metal hydrides to store hydrogen. Hydrogen is first catalytically decomposed into hydrogen atoms on its surface; these hydrogen atoms then diffuse into the voids within the material’s crystal lattice, where they are stored in atomic form within the metal’s crystal sites to form a metal hydride. This reaction process is reversible, thereby enabling the absorption and release of hydrogen. Currently, the main types include magnesium-based hydrogen storage alloys, iron-based hydrogen storage alloys, lanthanum-nickel-terbium-based hydrogen storage alloys, titanium-based hydrogen storage alloys, and zirconium-based hydrogen storage alloys. Metal can store nearly a thousand volumes of hydrogen per unit volume under normal temperature and pressure, and its volumetric density is even better than that of liquid hydrogen; therefore, metal-based hydrogen storage has become a popular trend, and most of the companies that have entered this field have done so for this reason.

Taking magnesium-based alloy hydrogen storage materials, which are based on the relatively low-molecular-weight metal magnesium, as an example, China has a significant advantage in terms of magnesium resources – approximately 90% of the world’s magnesium is produced in China, so there is no issue of material shortages. Its volumetric hydrogen storage density can reach 106 kg/m3, which is 1,191 times that of hydrogen under standard conditions, 2.7 times that of hydrogen stored at 70 MPa pressure, and 1.5 times that of liquid hydrogen; moreover, it is very environmentally friendly. From the perspective of the driving forces behind this development, given the high technical barriers and substantial capital requirements associated with solid-state hydrogen storage, efforts in this field are primarily carried out through collaborations between enterprises and leading universities specialized in non-ferrous metal research, as well as established companies. Such partnerships enable the creation of technology development platforms and demonstration projects in order to gain a competitive edge in this field. Among them, the Yoyan Research Institute, which is part of the Yoyan Technology Group and was established from the former Beijing Non-ferrous Metals Research Institute, has become a key driver in the development of the solid-state hydrogen storage industry. It has entered into partnerships with various hydrogen energy companies such as Shengyuan Environmental Protection, Hydrogen Maple Energy, Jiahualidao, and Hongda Xingye, in order to accelerate the advancement of key technologies related to solid-state hydrogen storage as well as the commercialization of related innovations. From a policy perspective, attention has been drawn to the guidance provided for the development of solid-state hydrogen storage technology routes. The \"Medium- and Long-Term Plan for the Development of the Hydrogen Energy Industry (2021–2035)\") issued in March this year sets out specific requirements for the construction of hydrogen energy infrastructure and safety management, with the aim of accelerating the establishment of a safe, stable, and efficient hydrogen energy supply network.

In response, Wang Xiang, Deputy Director of the High-Tech Department of the National Development and Reform Commission, explained: It is necessary to steadily develop a storage and transportation system, support the exploration and implementation of various storage and transportation methods, and gradually build a hydrogen energy storage and transportation system that is high-density, lightweight, low-cost, and diversified. In addition to advancing the commercialization and industrialization of high-pressure gaseous storage and transportation as well as cryogenic liquid hydrogen storage and transportation, efforts should also be made to explore the application of solid-state, deep-cold high-pressure, and organic liquid storage and transportation methods. In April this year, the **Rare Earth Functional Materials Innovation Center held an expert review meeting in Baotou City to discuss the implementation plan for the project \"Innovation Platform for Rare Earth Hydrogen Storage Materials and Their Applications – Development of Solid Hydrogen Storage Systems and Construction of Pilot Production Lines\" ； Also in April, the Ministry of Science and Technology issued the 2022 application guidelines for key projects under priority research and development programs such as the \"Hydrogen Energy Technology\" program; these included projects related to solid-state hydrogen storage, such as reversible hydrogen storage technologies based on new solid materials, as well as solid-state hydrogen storage systems for medium and low-pressure hydrogen pipelines and their associated application technologies.

Progress in the industry chain and market prospects: Behind this growing development, business opportunities arise in areas such as solid hydrogen storage materials and hydrogen storage systems. What is the current level of development of solid hydrogen storage materials and hydrogen storage systems in China? What will be the direction of development in the future? A complete hydrogen storage system unit, including the hydrogen storage alloy, housing, valves, piping, internal structure, and other auxiliary devices. A solid-state hydrogen storage system is constructed from a series of solid-state hydrogen storage modules according to a specific design, and it includes solid-state hydrogen storage modules, enclosures, monitoring units, and other auxiliary devices. In terms of materials and key components, solid-state hydrogen storage operates at low pressures and offers good safety characteristics; as a result, the development and production of auxiliary devices such as hydride storage tanks, valves, and piping systems are relatively straightforward. Companies can either develop and produce these components in-house or purchase them to meet their needs ； At present, the research and development of hydrogen storage alloy materials and the control and integration of solid-state hydrogen storage systems remain the main constraints. There are various technical approaches for storing hydrogen in metal hydrides; based on the chemical properties of the metals and the requirements of specific application scenarios, major approaches have been developed, such as solid-state hydrogen storage using ferrotitanium materials, which are low-cost and easy to implement, as well as solid-state hydrogen storage using magnesium-based materials, which offer superior hydrogen storage and charging/discharging capabilities. “After careful consideration, we selected the AB₂ titanium-based material for solid-state hydrogen storage, as it offers advantages in terms of cost and system integration for use in automotive applications. ”Liu Yangcheng, technical director at Jiahualidao, said that the company’s 4.5T solid-state hydrogen storage fuel cell refrigerated truck, which features independent intellectual property rights, has been delivered. In terms of technological development, on the one hand, the technology related to metal hydride materials for hydrogen storage needs further improvement, in aspects such as weight-based hydrogen storage capacity and reversibility ； On the other hand, although hydrogen storage alloys have a high volumetric hydrogen storage density, heating and cooling in a hydrogen storage system are achieved by installing heat exchange pipes inside the hydrogen storage tank. The flow of fluid through these heat exchange pipes and the resulting heat exchange at different locations affect the reaction rate of the hydrogen storage alloy; therefore, such systems require high precision in controlling the temperature, speed, and cycle of hydrogen absorption and release. Optimizing the performance of hydrogen storage materials and the control management of hydrogen storage systems are key research focuses for companies entering this field.

In terms of application areas, solid-state hydrogen storage is still in the early stages of research and development. In recent years, buses, trucks, refrigerated vehicles, and backup power sources that use solid-state hydrogen storage as an energy source have been introduced in China. In China, companies such as Hydrogen Storage Energy, Magnesium Source Power, and Antai Chuangming have established production lines for materials and industrialization projects; all three of these firms use magnesium-based materials for solid-state hydrogen storage in their operations. It is also worth mentioning that, since solid-state hydrogen storage makes use of metal hydrides and aluminum alloy hydrogen tanks, the existing solid-state hydrogen storage tanks are relatively heavy. Current applications are mainly focused on fixed hydrogen storage systems as well as small mobile applications where weight is not a concern. “In the future, solid-state hydrogen storage could become a highly efficient method for large-scale energy storage. It can be used as a power source for combined heat and power systems in buildings, as a reliable power source for microgrids, and as a backup power source for mobile base stations. It allows for safe long-term storage of energy, as well as rapid adjustment of power output to meet demand fluctuations. In the field of mobile applications, solid hydrogen storage tanks can be used as a product that is available for sale and replacement. ”Industry insiders speculate. Overall, solid-state hydrogen storage offers clear advantages in terms of high density and high safety. As the hydrogen energy industry and related companies pay more attention to this field, solid-state hydrogen storage is likely to see continuous technological improvements in practical applications, thereby contributing to the development of a diversified storage and transportation system for hydrogen energy.

What is more suitable for the current situation is to convert hydrogen into a liquid form in chemical industrial parks, and pipeline transportation is a growing trend.

Given the properties of hydrogen, transporting it through pipelines seems too risky