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At present, the public generally believes that "wind (solar) power generation → electrolysis of water for hydrogen production → hydrogen storage → fuel cell power generation" is one of the important paths for the generation and utilization of ideal clean energy in the future. Among them, hydrogen energy storage is achieved by storing renewable energy for power generation or surplus electricity for electrolysis of water to produce hydrogen gas (green hydrogen), and converting the stored hydrogen gas into electrical energy through fuel cells when needed. It is an important means of long-term energy storage and can achieve cross day or even cross season regulation of wind and solar clean energy. Therefore, hydrogen energy storage is undoubtedly of great significance for the storage of renewable energy, the development layout of new energy in China, and the achievement of the "dual carbon" goal.

As is well known, renewable energy generation has intermittent and fluctuating characteristics and cannot be directly integrated into the grid. Hydrogen storage can effectively combine electrolytic hydrogen production, hydrogen storage, and hydrogen utilization to achieve efficient storage and utilization of renewable energy, cultivate efficient and advanced clean energy development and utilization models, and the continuous development and maturity of hydrogen storage can effectively solve the current problem of "wind and solar waste" in the utilization of renewable energy, promoting further deep development and application of renewable energy. Therefore, the electricity generated can be stored by electrolyzing water to produce hydrogen, and stable power generation can be integrated into the grid through fuel cells, thereby achieving efficient utilization of renewable energy. Moreover, the hydrogen storage power station system is simple, easy to maintain, and starts quickly, which can effectively supplement the power supply to the grid.

At present, hydrogen energy storage has entered the stage of commercial application abroad, while the development in China is relatively slow and still in the stage of demonstration station construction. In January 2022, the first domestically built MW level solid polymer electrolysis hydrogen production, hydrogen storage, and fuel cell power generation demonstration station with independent intellectual property rights in Lu'an, Anhui Province, achieved full chain connectivity and grid connected power generation, enabling maximum storage and utilization of renewable energy. By 2030, China will develop wind and solar power with a total installed capacity of over 1.2 billion kW, which will result in an average annual increase of over 70 million kW in new energy during the 14th and 15th Five Year Plans. This magnitude of new energy growth undoubtedly requires strong energy storage devices (such as hydrogen storage, flow batteries, etc.) to support it.


Anhui Lu'an Megawatt Hydrogen Energy Comprehensive Utilization Demonstration Station

The temperature of hydrogen liquefaction is extremely low, about -253 ℃, and it is easy to cause hydrogen embrittlement and hydrogen leakage in the metal. At present, fuel cell hydrogen supply systems mainly include high-pressure hydrogen storage, liquefied hydrogen storage, and solid-state hydrogen storage.


Comparison of different hydrogen storage methods [1]

Low temperature liquid hydrogen storage mainly converts gaseous hydrogen into liquid hydrogen by lowering the temperature, but its large-scale application is limited due to high energy consumption and high cost; Solid state hydrogen storage utilizes hydrogen storage materials (such as hydrogen storage alloys) to achieve reversible hydrogen charging and discharging. Due to its high bulk hydrogen storage density, low energy consumption, and high safety, it has broad prospects in fuel cell vehicle systems and future hydrogen storage, but currently it is mainly in the experimental stage. The use of high-pressure physical hydrogen storage technology for hydrogen storage is generally achieved by using a compressor to compress the hydrogen to the pressure required by the high-pressure hydrogen storage container for storage. Although there are problems with low hydrogen storage density and safety that need to be improved, it is currently the most important hydrogen storage method due to its simplicity, low cost, and fast hydrogen flushing and discharging speed.

High pressure physical hydrogen storage achieves the storage of gaseous hydrogen through pressurization, which has lower energy consumption and cost compared to low-temperature liquid hydrogen storage. It is currently the main method adopted by most enterprises (such as Zhejiang Juhua, Beijing Ketek, etc.) for hydrogen storage in refueling stations and onboard hydrogen storage. At present, the cylinder volumes of hydrogen storage stations range from 45L to 1500L, and the most mature and low-cost fixed steel hydrogen storage cylinders and steel pressure vessels are commonly used. At present, 20MPa steel hydrogen cylinders are commonly used in industry, and can be combined with 45MPa steel hydrogen cylinders and 98MPa steel strip wound pressure vessels for application. With the continuous development of high-pressure hydrogen storage containers, their pressure upper limit is also constantly increasing. The international standard for hydrogen refueling stations is a pressure upper limit of 70MPa, while in Japan, its safety upper limit has been raised to 88MPa. In China, the most advanced Changshu hydrogen refueling station can reach a maximum of 98MPa. However, due to its gaseous state, its hydrogen storage density is only about 40g/L, which is still some distance from the DOE's released hydrogen storage target of 55g/L.

In the white paper "China's Energy Development in the New Era" issued by the State Council in December 2020, it was pointed out to accelerate the development of hydrogen storage and promote the improvement of the hydrogen fuel cell technology chain. With the rapid development of the photovoltaic industry and other new energy generation fields, as well as the continuous reduction of costs, hydrogen energy storage will become an important option for clean energy storage in the future. At present, the overall cost of electrolyzing water for hydrogen production and fuel cell power generation is relatively high, and it is still necessary to continuously achieve localization in key materials and technologies, continuously improve power generation efficiency and collaborative control, accelerate policy improvement and hydrogen storage system construction. But in the next decade, with the further improvement of hydrogen storage technology, the industrial development and efficient construction of hydrogen energy storage are very promising.



References

[1] Wang Heng. Application of Hydrogen Energy Development Model [J]. Rural Electrification, 2021, (05): 65-69