With the increasing penetration rate of renewable energy in China’s power system in the future, the stability of the system will face more severe challenges. Long-term energy storage technology plays an important role in balancing grid demand, improving grid stability, promoting the consumption of renewable energy, and promoting green and low-carbon development in the power system. Long-term energy storage has a wide range of application scenarios on the power supply side, grid side, and load side of the system, which is of great significance for the development of China’s new power system. Firstly, the characteristics and development trends of the current new power system are introduced, and the supporting role of long-term energy storage technology in the new power system is analyzed. Then, the technical principles and routes of five long-term energy storage technologies, such as the compressed air energy storage, lithium-ion battery energy storage, liquid flow battery energy storage, molten salt energy storage, and hydrogen energy storage, are summarized. The advantages and disadvantages of various long-term energy storage technologies are also analyzed. Finally, the future application prospects of long-term energy storage technology in the new power system are discussed.

Affected by the rapid electricity load growth and the increase of water uncertainty under extreme weather conditions, the contradiction between supply-side and demand-side volatility in areas with high hydropower proportion has become increasingly prominent. The demand for flexible resources with long-term regulation capability is becoming more urgent. Hydrogen energy storage with long-term regulation capacity can alleviate the tense situation of supply and demand in areas with high proportion of hydropower. The research designs an optimal allocation model of electric-hydrogen hybrid energy storage, which is suitable for areas with high hydropower proportion. The loss of load penalty function is introduced into the objective function, and the variation of generation capacity of large/small and medium-sized hydropower units with time is quantified. By taking the power system composed of 96 different types of generators in a high hydropower proportion area as the object, analysis is performed. Compared with the current energy storage configuration requirements, the optimization result of the model increases the hydropower consumption by 7 188 MW·h, reduces the unloaded electricity by 6 513 MW·h, and reduces the total cost by 3.194 million yuan. Moreover, the demand scale of different types of energy storage and the income of energy storage enterprises in high hydropower area, high thermal power area and high new energy area are compared horizontally. The relevant conclusions can provide reference for the development of energy storage investment in the future.

The compressed air energy storage is a large-scale physical energy storage technology and a highly promising new type of energy storage technology. This paper summarizes the basic principles of isothermal compressed air energy storage, and introduces the principles and current development status of key equipment and related technologies. It provides an analysis and summary of liquid pistons, pumps and turbines. Moreover, it reviews the basic principles of isothermal compressed air energy storage, and analyzes the existing research progress on isothermal compressed air energy storage technology. An analysis and summary are presented for liquid piston technology, as well as pump and turbine technology in the system. The data of existing compressed air energy storage power stations are summarized and analyzed. The data of existing compressed air energy storage power stations are summarized and analyzed. On this basis, the future development direction of isothermal compressed air energy storage technology is prospected, which provides a certain data reference for the selection of power equipment in isothermal compressed air energy storage system and the promotion of demonstration projects.

Solid oxide cells have the ability to switch between electrolysis and fuel cell power generating modes, and operate at 650~850 ℃, resulting in high-grade waste heat. The equipment utilization ratio and energy utilization efficiency can be significantly increased by using the cell for the tri-generation of heat, electricity, and hydrogen. A photovoltaic and concentrated solar heat driven solid oxide cell system for tri-generation system of heat, power, and hydrogen is presented, and molten salt thermal storage system and batteries are coupled to ensure continuous and stable operation of solid oxide cell. By taking the lowest total cost as the object, a mixed integer linear programming model for system capacity configuration and operation strategy optimization is constructed. Moreover, based on the energy consumption principle of cascade utilization, the pinch analysis approach is applied to maximize the cascade use of multi-grade energy flows throughout the entire system, providing an efficient mechanism for integrating mass and energy in coupled systems. For a real case of solar energy resources and heat, electricity, hydrogen requirement in an industrial park, the coupled system’s levelized energy cost is 0.28 yuan/kW, and the annual full load operating hours of the solid oxide cell reaches over 6 000 h.

Liquid air energy storage (LAES) technology stands out as a large-scale energy storage technology due to its superior energy storage density and adaptability to external energy sources. An LAES system that recovers waste cold of liquid ethylene and introduces an external low-temperature heat source is proposed. Moreover, thermodynamical and economic analysis on key parameters, including isentropic efficiency of the compressor and expander, and temperature of the heat source, are conducted. The results reveal that, when the ethylene flow rate is 34 t/h, the energy storage capacity can reach up to 5 MW/40 (MW·h). At isentropic efficiency of the compressor and expander of 90%, the round-trip efficiency can achieve 77.45% by solely relying on an ambient heat source of 25 ℃ for air heating. When the heat source temperature is increased to 125 °C, the system’s optimal round-trip efficiency, net present value, and dynamic payback period reaches 106.99%, 144.73 million yuan, and 3.56 years, respectively. These findings provide reference for research on the coupling of LAES systems with external cold energy.

Latent heat thermal energy storage technology can realize recovery and supply of heat during solid-state hydrogen storage and release process, achieving self-thermal balance inside the solid-state hydrogen storage tank, and improve the hydrogen storage and release performance. For horizontal tube and shell latent heat thermal energy storage exchanger, a new movement method where the inner tube is placed eccentrically to rotate around the central axis is proposed. By the Fluent software, the user-defined function UDF is written using the dynamic mesh technique, and the influence of eccentric distance and rotation velocity of the inner tube on heat storage performance is focused. The results show that, compared with the conventional static arrangement of the central inner tube, the rotation movement of the eccentric inner tube can improve the heat storage performance significantly. The heat storage time reaches the shortest when the eccentric distance is 9 mm and the rotation velocity is 0.10 r/min, namely decreases by 92.16%, and the time average heat storage rate increases by 11.51 times. The heat storage time reduces by 13.57% when the eccentric distance is 9 mm and the rotation velocity is decreased from 0.30 r/min to 0.1 r/min, it decreases by 70.48% when the rotation velocity is 0.10 r/min and the eccentric distance is increased from 3 mm to 9 mm. The study results can provide a new idea for performance optimization of horizontal shell and tube latent heat thermal energy storage exchangers in hydrogen storage field.

“Power entropy” can quantitatively reflect the characteristic difference of multi-time scale energy storage configuration. The power curve synthesized by two sinusoidal power curves is used to study the entropy difference and characteristics of main scenarios of energy storage applications such as frequency regulation, peak regulation and cross-season energy regulation. The results show that, power entropy can effectively reflect the difference of characteristics of energy storage for different time scales. For the scenarios of frequency regulation and peak regulation, using two sets of energy storage is better. For the scenarios that the difference between frequency and amplitude is less than 2 times, it is appropriate to apply a single set of energy storage. The research theoretically explores the methods and basis of multi-time scale energy storage configuration, reveals the essential differences of multi-time scale problems, it is helpful to form a scientific and optimal energy storage configuration scheme, scheduling scheme and optimization scheme.

At present, the construction technology of salt cavern gas storage has been mature, and it is developing in the direction of intelligence. Based on the technical status of salt cavern gas storage, the current construction technologies of salt cavern gas storage are analyzed. From the perspective of whole life cycle management, the intelligent construction of salt cavern gas storage is divided into four stages: intelligent location, intelligent design, intelligent construction and intelligent operation and maintenance, and the key technologies involved in each stage are studied. The technical framework of intelligent construction technology of salt cavern gas storage and its specific content is put forward. Moreover, the future research focus of intelligent construction of salt cavern gas storage is proposed and summarized from four aspects: system, technology, theory and model. The relevant technologies have been effectively applied in Yingcheng 300 MW compressed air energy storage demonstration project.

In order to reduce the fluctuation of renewable energy power generation output and improve the utilization rate of renewable energy, this paper designs an on/off grid wind solar hybrid hydrogen synthesis ammonia system. Taking the maximum annual revenue of the system as the objective function, considering the operation constraints such as power balance, hydrogen balance and grid interaction, a capacity allocation scheduling optimization model is established. Taking the real output of the wind and solar energy in a certain area of Inner Mongolia as the input, through the analysis on wind and solar energy capacity ratio, this paper explores the technical and economic effect of the wind and solar energy capacity ratio on the system. The results show that, after the capacity configuration and scheduling optimization of the on/off grid wind solar complementary hydrogen and ammonia system, the system can reasonably switch the working state under different wind and solar output conditions, stabilize the wind and solar fluctuations, and realize the stable and efficient operation of ammonia equipment. The grid connected system is better than the off grid system. Through the analysis of the ratio of wind and solar capacity, in the case area, with the increase of wind capacity, the capacity of electrolyzer and hydrogen storage tank to be configured in the system shows a trend of first decreasing and then increasing. When the capacity of wind power generation and photovoltaic power generation is close to or equal, the economic efficiency of the system is high.

Hydrogen storage by physical adsorption offers significant advantages, including high safety, high hydrogen storage density, and fast hydrogen charging and discharging rates, making it a highly promising method for hydrogen storage. Among the various materials, metal-organic frameworks (MOFs) have emerged as ideal hydrogen storage materials due to their highly ordered porous structures and tunable characteristics. To investigate the influence of thermal effects during the hydrogen adsorption process on storage performance, a numerical model of hydrogen storage by adsorption is established and validated. Subsequently, the hydrogen storage properties of Cu-BTC and activated carbon AX-21 tanks are analyzed and compared. Furthermore, the hydrogen storage capacity of Cu-BTC tank at different temperatures is explored. The results indicate that, compared with AX-21, the hydrogen storage capacity at room temperature increases by 12.8% when using Cu-BTC as adsorbent. When the storage temperature is reduced to 77 K, the maximum pressure in the Cu-BTC tank decreases to 0.97 MPa, and the hydrogen storage capacity increases by 174% compared with room temperature (300 K). These findings provide valuable insights for further research on the hydrogen storage capabilities of Cu-BTC materials.