Compressed air energy storage is a new form of large-scale and long-term physical energy storage. Gas storage is a crucial component of compressed air energy storage system. The characteristics of common gas storage devices are summarized, and the underground artificial chamber is discussed in detail. The advantages of underground artificial chamber of compressed air energy storage system compared with other types of gas storage are summarized. The design factors such as bearing structure, sealing system and heat transfer management system of underground artificial chamber are analyzed. The key technologies affecting operation of the underground artificial chamber such as site selection, buried depth and pressure design criteria are analyzed and discussed. The evaluation method and evaluation indexes of the factors affecting stable operation of the artificial chamber are put forward. On this basis, the future development direction of compressed air energy storage underground artificial chamber is prospected, which provides a reference for rational design and stable operation of the underground artificial chamber.

Flow batteries are considered as one of the most promising technologies for large-scale energy storage, due to their inherent safety, long cycle life, environmental friendliness and robust scalability. As the key material of flow batteries, electrodes have a significant influence on battery performance. The research advancements of electrospun carbon nano-fiber electrodes in flow batteries are reviewed. The fabrication principles of electrospun carbon nano-fibers and their influence on the critical fabrication parameters are elucidated. It provides a comprehensive review of preparation methods for electrospun carbon nano-fiber electrodes with controllable structure and chemistry, properties and their effect on battery performance, including microstructural modulation of carbon nano-fibers, heteroatom doping, and catalytic modification. The key of electrode optimization is synergies between electrochemical activity and mass transport of electrodes, which are associated with the active areas and chemistry properties. The microstructure and surface properties of fibers can be controlled by strategies involving fiber porosity or new structural designs. Doping heteroatoms and introducing catalysts can increase the active area and hydrophilicity of the electrodes to promote the electrochemical activity of the electrodes. Lastly, the challenges and future developments of the electrospun carbon nano-fiber electrodes from laboratory preparation to scaling-up are outlined.

In view of the electricity demand of users and the power generation of renewable energy, an optimal scheduling model of grid-connected wind-optical-battery-waste mine pumped storage combined power generation system is established, with the optimization objective of minimizing the total operating cost of the system. Moreover, the results of the optimal scheduling are measured with the evaluation indexes of the equivalent load variance, the fluctuation rate of the contact line, and the power supply loss rate. The optimal solution is performed using CPLEX solver for the scheduling model. Through simulation on the optimal scheduling models of three different energy storage forms, it is concluded that the total cost of the hybrid energy storage in the form of storage battery and abandoned mine pumped storage reduces by 62.21% and 49.18% compared with that of the battery alone and abandoned mine pumped storage alone, respectively. The optimization results are ranked and evaluated by using the combined entropy weight rank sum ratio method, and the weighted rank-sum ratio of the wind-solar-battery-abandoned mine pumped storage combined power generation system is 0.833, with the highest score ranking. The results show that the proposed model not only improves the operation economy of the system, but also enhances the reliability of the system power supply, which verifies the rationality and effectiveness of the proposed model.

A new type of liquid air energy storage (LAES) system coupled with solar energy is proposed to address the issue of low round-trip efficiency (RTE) in current LAES systems. The discharging process of the new system is equipped with series-connected two-stage air heaters, which improves the RTE while allowing the system to operate in conventional ways under low solar radiation conditions. Sensitivity analysis of main parameters and exergy analysis are conducted on the new system, and the results show that, within the allowable range, the lower the liquefaction temperature, the lower the charging pressure and the higher the discharging pressure, resulting in higher RTE of the system. The optimal RTE of the system can reach 72.4%, and the system can still operate at an RTE of 53.6% when solar radiation is insufficient. The exergy efficiency of the new system is 38.0%, among which the solar collector field has the highest exergy destruction, accounting for 52.4% of the total exergy destruction, followed by the throttle valve and thermoelectric generator. In heat exchangers, there is significant exergy destruction in cold boxes and evaporators.

Wind power generation and solar thermal power generation have complementary advantages in terms of time characteristics, and the heat storage system equipped with solar thermal power station can effectively alleviate the peak regulation pressure and improve the wind power absorption capacity. On this basis, a solar thermal-wind combined power generation system is proposed. The Latin hypercube sampling method is used to effectively reduce the uncertainty of wind power output and solar irradiation intensity. Then, a two-stage double-layer optimal allocation method is proposed to rationally allocate the heat storage capacity. The upper layer model aims to minimize the investment cost of comprehensive operation of the system and the lowest curtailment of the system. The optimal heat storage capacity is determined by a fuzzy multi-attribute decision scheme. In the lower layer model, the operation is optimized with the goal of maximizing the net benefit of the cogeneration system in the scenario. The results show that the optimal heat storage capacity of the heat storage system of the solar thermal power station is 906 MW·h, and the comprehensive operating cost for the optimal heat storage capacity configuration is 2 430 000 yuan. Through the comparison between the results of different scenarios, the curtailment of the system with this configuration method reduces by 69.615 MW, and the net revenue of the system increases by 7.7%.

The beam-down concentrating solar power plant has the advantages of high concentrating ratio, low installation and maintenance requirements, and low pump consumption. Relying on the 50 MW beam-down tower concentrating solar power station in Yumen Xinneng First Power Co., Ltd., the mathematical models of the heliostat field, hyperboloid mirror, receiver, molten salt tank, and power generation cycle are established and verified. The run-test results reveal that, the maximum outlet temperature of the molten salt can be maintained at 559 ℃ for 50 minutes at an average direct normal irradiation of 739.70 W/m². The cosine efficiency, shading and blocking efficiency, shading efficiency of the hyperboloid mirror, and attenuation efficiency of the heliostat field at 12:00 are 0.856 8, 0.999 7, 0.994 1, and 0.974 6, respectively. The average hyperboloid mirror flux density and receiver flux density are 11.3 kW/m² and 400.5 kW/m², respectively. Meanwhile, the power station is maintained for 16 h at the rated generation power of 50 MW. The research has certain reference significance for the operation of a beam-down concentrating solar power plant.

Compressed air energy storage (CAES) technologies have garnered widespread attention due to their large scale, high efficiency, and environmental friendliness. Among them, the non-combustion compressed air energy storage technology is mature, and produces no carbon emissions during operation. There are already several adiabatic non-combustion compressed air energy storage power stations in operation, under construction, and in planning in China. However, the design parameters of the CAES system lack a unified standardization system, which poses many challenges in system design and performance optimization of CAES. To solve this problem, the design of medium-temperature and high-temperature thermal energy storage system schemes for a 200 MW class CAES system is presented, the key equipment parameters and system boundary conditions are determined. Moreover, the performance and technical economy of the medium- and high-temperature thermal energy storage system schemes is compared. The results show that, the high-temperature thermal energy storage system is superior to the medium-temperature thermal energy storage system in performance indicators, but it has a higher investment cost, indicating that when choosing the thermal energy storage technology route for large-capacity CAES systems, it is necessary to consider comprehensively based on specific application scenarios and economic budgets.

Based on the time-of-use electricity price and the cost of wind-PV-energy storage system, technical and economic research of source-grid-load-storage system is studied. Firstly, a microgrid system model integrating renewable energy and energy storage system is proposed, which includes PV, wind power, energy storage system, grid, and load. Then, under the premise of ensuring reliable power supply to the load, an optimization model of the source-grid-load-storage system is established with the goal of optimizing the system economy based on load data, irradiation data, wind speed data, time-of-use electricity price data, and the costs of each unit of the system. Finally, the optimal capacity and economic feasibility of configuring a wind-PV-storage system in a certain region are analyzed in detail through a numerical example. The analysis results indicate that, the energy storage systems store energy at low electricity prices and release energy at high electricity prices, thereby avoiding users from purchasing electricity from the grid at high electricity prices and reducing the cost of purchasing electricity from the grid. The configuration of a wind-PV-energy storage system can effectively reduce the annual cost of purchasing electricity from the grid.

With the rapid advancement of renewable energy power generation, thermal power units need to take on major peaking tasks. Molten salt thermal storage technology, as a prominent method for thermal power peaking, can effectively improve peaking performance of the units. The Ebsilon software is employed to model a subcritical 300 MW unit integrated with coupled molten salt thermal storage system. Considering the operational conditions of supplying industrial steam to external entities, several indexes such as the storage/exothermic thermal efficiency, load variation and thermoelectric conversion rate of three heat storage/exothermic schemes are investigated comparatively. The results indicates that, during the heat storage process, the heat storage scheme 3 (the heat source for heat storage is the main steam, reheat steam and medium-pressure cylinder exhaust, and the exothermic medium-pressure cylinder exhaust goes directly to the condenser) exhibits the highest load variation, reaching up to 102.63 MW. Meanwhile, the heat storage scheme 1 (employing main steam and reheat steam as the heat source for storage) demonstrates the superior thermal efficiency at 28.76%. During the discharge process, exothermic scheme 2 (heat from high-temperature molten salt is used to supply industrial steam and preheat condensate) has the largest load variation, release thermal efficiency, and thermoelectricity conversion rate, which are 34.69 MW, 46.14%, and 59.07%, respectively. This study can provide theoretical guidance for the study of peak performance and thermal economy of thermal power units coupled with molten salt thermal storage system.

Energy storage system assisted thermal power unit frequency regulation is limited by the capacity of storage device, and its output power can not track the command power for a long time. At the same time, lithium battery energy storage technology also exists problems in safety hazards, cycle life limitations, limited enhancement of unit frequency gain gain and other issues. For this reason, the characteristics of high cycle life and high safety of supercapacitor are used to construct the simulation model of hybrid energy storage system assisted coal-fired thermal power unit frequency regulation in Matlab/Simulink platform. Combining with the operating state of thermal power unit and energy storage system, a set of control strategy based on index calculation and fuzzy control synergy is designed to achieve the adaptive adjustment of hybrid energy storage system output under dynamic operating conditions. Simulations show that, the control strategy can effectively extend the service life of lithium batteries and efficiently utilize the residual power of the hybrid energy storage system. Compared with the conventional control strategy of hybrid energy storage system, the proposed control strategy reduces the average daily use time of lithium battery by 60%, improves the comprehensive index of frequency regulation performance by 34%, and increases the average daily revenue by 20 000 yuan, which has high engineering application value.