Solid state hydrogen storage can significantly improve the volumetric hydrogen storage density and enhance the safety of hydrogen storage and transportation, addressing the two most concerning issues of high-density hydrogen energy storage and safe application. With the rapid development of the hydrogen energy industry in China, it has attracted multiple enterprises to enter the market

From the perspective of implementation methods, solid-state hydrogen storage is mainly divided into physical adsorption and chemical hydride hydrogen storage. The former utilizes activated carbon, carbon nanotubes, carbon nanofibers, and carbon based materials to physically adsorb hydrogen gas, as well as metal organic frameworks (MOFs) and covalent organic frameworks (COFs) with microporous grids to capture and store hydrogen gas.
 
And chemical hydride hydrogen storage utilizes metal hydride hydrogen storage. Hydrogen gas first catalyzes the decomposition of its surface into hydrogen atoms, which then diffuse into the internal voids of the material lattice and are stored in the metal crystallization points in an atomic state, forming metal hydrides. This reaction process is reversible, thus achieving the absorption and release of hydrogen gas.
 
At present, there are mainly magnesium based hydrogen storage alloys, iron-based hydrogen storage alloys, lanthanum nickel rare earth based hydrogen storage alloys, titanium based hydrogen storage alloys, zirconium based hydrogen storage alloys, etc. A unit volume of metal can store nearly a thousand volumes of hydrogen gas at room temperature and pressure, with a volume density even better than liquid hydrogen. Therefore, metal hydrogen storage has become a popular development trend, and most of the aforementioned companies have also entered the market as a result.

Taking magnesium based alloys with lighter molecular weight as an example for hydrogen storage, China has a great advantage in magnesium resources. About 90% of the world's magnesium is produced in China, and there is no problem of material being "choked". Its volumetric hydrogen storage density can reach 106 kg/m ³, which is 1191 times the density of hydrogen gas under standard conditions, 2.7 times that of high-pressure hydrogen storage at 70 MPa, and 1.5 times that of liquid hydrogen. It is also very environmentally friendly.
 
From the perspective of the main body of promotion, due to the high technological threshold and huge funding demand of solid-state hydrogen storage, the layout and promotion of the field of solid-state hydrogen storage are mostly carried out in the form of cooperation between enterprises and cutting-edge universities and advantageous enterprises specializing in non-ferrous metal research, seizing development opportunities through the establishment of technology attack platforms, demonstration development projects and other forms.
 
Among them, the Industrial Research Institute of Youyan Technology Group, which was restructured from the former Beijing Nonferrous Metals Research Institute, has become a powerful driving force for the development of solid-state hydrogen storage industry. It has successively cooperated with hydrogen energy enterprises such as Shengyuan Environmental Protection, Hydrogen Maple Energy, Jiahua Lidao, and Hongda Xingye to accelerate the breakthrough of key technologies and the incubation and transformation of achievements in solid-state hydrogen storage.
 
From the perspective of policy environment, the development guidance of solid-state hydrogen storage technology has attracted attention. The "Medium - and Long Term Plan for the Development of Hydrogen Energy Industry (2021-2035)" issued in March this year put forward specific requirements for the construction and safety management of hydrogen energy infrastructure, aiming to accelerate the construction of a safe, stable, and effective hydrogen energy supply network.
 
Regarding this, Wang Xiang, Deputy Director of the High Technology Department of the National Development and Reform Commission, interpreted: We will steadily build a storage and transportation system, support the exploration and practice of various storage and transportation methods, and gradually construct a high-density, lightweight, low-cost, and diversified hydrogen energy storage and transportation system. In addition to promoting the commercialization and industrialization of high-pressure gas storage and transportation, low-temperature liquid hydrogen storage and transportation, it is also necessary to explore the application of solid-state, cryogenic high-pressure, organic liquid and other storage and transportation methods.
 
In April of this year, the National Rare Earth Functional Materials Innovation Center organized an expert demonstration meeting on the implementation plan of the "Rare Earth Hydrogen Storage Materials and Application Technology Innovation Platform - Solid State Hydrogen Storage System Development and Pilot Production Line Construction" project in Baotou City; In April of the same year, the Ministry of Science and Technology released the 2022 project application guidelines for key projects such as the National Key R&D Program "Hydrogen Energy Technology", which includes solid-state hydrogen storage and release technology based on solid-state new materials, solid-state hydrogen storage systems for medium and low-pressure hydrogen pipelines and their application technologies, and other solid-state hydrogen storage related projects.
 
 
Progress of the industrial chain and market prospects
 
Behind the warming of development, business opportunities for solid-state hydrogen storage materials and systems have emerged. What is the current level of development of solid-state hydrogen storage materials and systems in China? What is the future development direction?
 
A complete hydrogen storage system unit, including hydrogen storage alloy, shell, valves, piping, internal structure, and other ancillary devices. A solid-state hydrogen storage system is designed based on a series of solid-state hydrogen storage modules, including solid-state hydrogen storage modules, enclosures, monitoring units, and other ancillary devices.
 
In terms of materials and key components, solid-state hydrogen storage has low working pressure and good safety performance, so the research and production difficulty of hydride storage tanks, valves, piping and other ancillary devices is relatively low. Enterprises can adopt self-developed production or procurement to achieve matching; At present, the research and development of hydrogen storage alloy materials and the integration of solid-state hydrogen storage system control are still the main constraints, and there are various technical routes for metal hydride hydrogen storage. Based on the chemical characteristics and application scenarios of metals, low-cost and easy to promote titanium iron material solid-state hydrogen storage, as well as magnesium based material solid-state hydrogen storage with superior hydrogen storage and charging/discharging performance, have been developed.
 
We have selected AB ₂ titanium based material for solid-state hydrogen storage after multiple considerations, which has advantages in cost and system integration in the automotive field, "said Liu Yangcheng, Technical Director of Jiahua Lidao. Currently, the company's independent intellectual property 4.5T solid-state hydrogen storage fuel cell refrigerated truck has been delivered.
 
In terms of technological development, on the one hand, the technology of metal hydride hydrogen storage materials needs to be mature, such as weight hydrogen storage rate, reversibility, etc; On the other hand, although hydrogen storage alloys have a high volumetric hydrogen storage density, the heating and cooling of the hydrogen storage system are achieved by setting heat exchange pipes inside the hydrogen storage tank. The medium flowing through different positions in the heat exchange pipes will affect the reaction rate of the hydrogen storage alloy. Therefore, the control of hydrogen absorption and release temperature, hydrogen absorption and release rate, and hydrogen absorption and release cycle in the hydrogen storage system requires high requirements. How to optimize the performance of hydrogen storage materials and control management of hydrogen storage systems is a key research and development focus for companies entering the market.
 
In the application field, solid-state hydrogen storage is still in the early stage of research and development demonstration. In recent years, buses, trucks, refrigerated trucks, backup power supplies, and other vehicles that use solid-state hydrogen storage as energy supply have emerged in China. Domestic enterprises represented by hydrogen storage energy, magnesium source power, and Antai Chuangming have established material and industrialization project production lines, and their solid-state hydrogen storage industries all adopt the magnesium based material solid-state hydrogen storage route.
 
It is worth mentioning that due to the use of metal hydrides and aluminum alloy hydrogen tanks in solid-state hydrogen storage, existing solid-state hydrogen storage tanks are relatively heavy, and current terminal applications are mostly concentrated in the fixed hydrogen storage application market, as well as small mobile applications that are not sensitive to weight.
 
Solid state hydrogen storage may be a very large-scale energy storage method in the future. It can not only serve as a reliable power source for building cogeneration, microgrids, and backup power for mobile base stations, but also be safely stored for a long time and quickly peak shaving. In the field of mobile applications, solid-state hydrogen storage tanks can be used as a product for sale and energy replacement, "industry insiders speculate.
 
Overall, the advantages of high-density and high safety solid-state hydrogen storage are obvious. With the increasing attention of the hydrogen energy industry and enterprises to this field, solid-state hydrogen storage is expected to continuously improve its technology in practical applications, promoting the realization of diversified storage and transportation systems in the hydrogen energy industry.