The wind force and solar energy, in fast-developing step, have made the power storage an indispensable part in the link of new energy. The technologies such as hydrogen production from electric power and hydrogen production from offshore wind power have gradually entered our field of vision. The important role of electrolytic water hydrogen production technology that transforms the electric energy into chemical energy for storage, which later transforms back into electricity or other forms of energy upon demand, cannot be rejected. The main contributors to the concept of hydrogen energy storage are two processes of hydrogen generation and hydrogen electrolysis. The excess electricity generated by renewable energy sources, such as solar energy and wind energy, is utilized to dissociate water into hydrogen and oxygen by a water electrolyzer, while the electrical energy is internally converted to hydrogen chemical energy storage. When electricity is required, hydrogen, using either fuel cells or gas turbines, chemically reacts with oxygen to be converted back into electricity either for the grid or for other electrical applications.

Water electrolysis hydrogen production technology

1. Efficiency improvement:With the progress of technology, core equipment such as electrolytic cells, proton exchange membranes, and catalysts continue to make breakthroughs, and the efficiency of hydrogen production from electrolytic water is gradually improved. Alkaline water electrolysis technology has high maturity and is the mainstream technology in the field of commercial electrolysis. Compared with the traditional technology, the PEM has higher current density and efficiency, and it can quickly respond to the power fluctuation of renewable energy sources.
2. Cost reduction:The large-scale production and material science development make the cost of hydrogen production by electrolytic water present a downtrend. Increase the production scale of the electrolyzer, reduce the cost of raw materials and manufacturing process, and, meanwhile, do the system design and operation management to improve the energy use efficiency so as to reduce the hydrogen production cost further.
3. Green hydrogen production capacity will be increased: The power generation using renewable energy can be transformed into electrolytic water for producing green hydrogen. In the global context of energy transition, countries strongly advocate for the development of green hydrogen. By 2025, the capacity of green hydrogen production will be three times that of China, with electrolytic water hydrogen production technology leading the world and accounting for about 60% of the world's built capacity.
4. Moreover, there are a lot of problems in the production of hydrogen by water electrolysis, and the efficiency of hydrogen production through water electrolysis is low, about 15%. The main equipment such as an electrolytic cell is costly, and some key materials like catalysts depend on imports, or their preparation process is complicated, leading to high production costs of hydrogen. Reasonable treatment and utilization of by-products in the process of hydrogen production, such as oxygen, to improve the economy and environmental friendliness of the whole process of hydrogen production.

 

Hydrogen storage technology

1. High-Pressure Gaseous Hydrogen Storage: This is the most common way in industrial hydrogen storage today. According to the principle of partial pressure, the higher the storage pressure of hydrogen is, the higher the storage density will be. In addition to the progress of high-pressure-resistant container material and manufacturing technology, safety and storage density have improved with the times, such as 70MPa ultra-high-pressure gaseous hydrogen storage technology being applied to some hydrogen fuel cell vehicles.
2. Liquid Hydrogen Storage: By liquefying hydrogen through cooling to about -253℃, high storage density of hydrogen can be achieved; it is suitable for large-scale and long-distance transportation but has highly energy-consumptive liquefaction processes, strict requirements on adiabatic performance of storage vessels, and greater difficulty in technique.
3. Hydrogen storage in solid:The use of metal hydride, coordination hydride, carbon material, and other solid materials to absorb or absorb hydrogen has the advantages of safety, efficiency, high hydrogen storage density, and is considered as the future direction of hydrogen storage technology. Currently, some solid hydrogen storage materials have entered small-scale demonstration applications.

 

Current situation and challenges:

Fuel Cell Optimization: The conversion efficiency, power density, and service life of fuel cells need to be further improved while the price of fuel cells has to be further reduced. Optimization of cell structure, improvement of material performance, and optimization of production process enable continuous extension of service life of fuel cells. Currently, the life of a hydrogen fuel cell system is about 20,000 hours, and by 2025, it will reach 25,000 hours, while by 2030, it will be 30,000-35,000 hours.

System integration and coordinated control: Solve such problems as system integration and coordinated control between hydrogen production, hydrogen storage, and hydrogen with other links to make it possible for efficient energy conversion, storage, and utilization with improved comprehensive performance and stability.

Grid-connected access technology: The hydrogen fuel cell power generation system connects to the grid, where there are certain problems that must be solved in power quality, power regulation, and adaptability in the grid.

While the cost is decreasing, the throw is higher compared to other ways of energy storage: the cost of fuel cells is falling rapidly with the maturity of technology and the expansion of the market size, and by 2025, it is expected to reach 1000 yuan /kW, and by 2030, it will reach 500 yuan /kW, gradually gaining the ability to compete with traditional internal combustion engines, but still at a high level.

 

Advantages of electrolytic water for hydrogen storage

1. High-energy storage: Large hydrogen energy density and realize high scale energy storage.
2. Long storage time: Hydrogen can be stored for a very long time, and long storing will not generate evident energy attenuation.
3. Clean, without pollution:In the whole process of storing hydrogen energy, there is almost no other poisonous pollutant generated; therefore, this way of storage is extremely friendly to the environment.
4. Extensive use: Hydrogen can be used in a wide range of applications, including but not limited to electricity generation, transportation, and industrial production.

 

It can be applied in the following areas

1. Renewable energy consumption:It is an effective way to overcome the intermittent and unstable power generation of renewable energies such as solar and wind.
2. Energy storage on the power grid:During the period of low power load in the power grid, electrolyze the water by the low price electric current, then store as hydrogen; during the period of peak power consumption, convert hydrogen to generate electricity supply for use by compensating the peaking and reducing valleys.
3. System for distributed energy sources:Can develop a set of distributed hydrogen energy storage systems that work in extremely remote areas or island industrial parks.
4. Transportation: Hydrogen fuel cell vehicles are typical applications of hydrogen energy storage in the transportation field.

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• hydrogen energy storage