[Objective] During the operation of artificial caverns, the gas distribution method has a significant impact on the pressure, temperature, and other thermodynamic properties of the gas. These changes in gas properties further affect the performance, safety, and stability of the caverns. [Method] A transient three-dimensional CFD model of an underground artificial cavern featuring a tangential gas distribution method was established using Fluent. The study investigated the changes in the temperature, pressure, and other thermodynamic properties of the gas inside the cavern during the charging process, analyzing the influence of the tangential gas distribution on gas thermodynamic properties. [Result] The results indicate that the tangential gas distribution method can optimize gas distribution, effectively control the gas temperature near the cavern wall to prevent local hot spots during cavern charging, and thereby improve the efficiency and safety of the CAES system. [Conclusion] Compared to conventional gas distribution methods, tangential gas distribution shows certain advantages in preventing local hot spots during the charging process in artificial caverns.
[Objective] With the large-scale integration of renewable energy, the demand for primary frequency regulation in power systems is growing. Traditional thermal power units face severe challenges due to their insufficient regulation performance. To address this technical challenge, this study focuses on an electric double-layer capacitor (EDLC) energy storage system for thermal power primary frequency regulation. [Method] Relying on the energy storage project of Huaneng Luoyuan Power Plant, a multi-level system design—spanning cell selection, module design, cluster integration, and a 1 MW/30 s prefabricated container—was completed based on 3.0 V/3400 F EDLC cells. An experimental platform was established to test key performance indicators, including module temperature rise, cell cycle life, and high-temperature durability. Finally, the primary frequency regulation response capability of the system was verified through simulation. [Result] The experimental results indicate that under a maximum regulation frequency of 30 cycles/h, the maximum temperature rise of the module is only 21 ℃. After 900000 cycles at room temperature, the capacity retention is 75.86%, while the capacity retention after 20000 cycles at 65 ℃ is 82.47%. Simulation results demonstrate that the system's power response delay is <50 ms, the output accuracy deviation is ≤ ±2.1%, and the charge-discharge turnaround time is only 60 ms. [Conclusion] The designed EDLC energy storage system exhibits the core characteristics of "fast turnaround and precise output", which can effectively improve the primary frequency regulation performance of thermal power units. This study provides a comprehensive design and experimental basis for the large-scale engineering application of EDLCs in the field of thermal power frequency regulation.
[Objective] This study addresses the issues of varying quality in safety risk early warning technologies for lithium battery energy storage stations and the conceptual confusion between "early warning" and "alarming." It aims to clarify the connotation and stage-specific characteristics of risk early warning and to standardize technology application. [Method] The research analyzed the connotation of station safety protection and investigated the causes of risk sources. It derived a development map for thermal runaway accidents in lithium batteries, defining characteristic signals and alert response measures for each stage. A systematic comparison was conducted between two categories of warning technologies: those based on external signals (particles, temperature, gas, stress, sound, ultrasonic) and those based on operational data analysis (voltage, current, temperature), focusing on their principles, applicable stages, and performance. Engineering application scenarios were statistically reviewed. The effectiveness of a specific early warning technology was validated using data from actual engineering project deployments. [Result] The study clarifies the development stages of safety risks, their characteristic signals, and a graded alert notification mechanism, fundamentally distinguishing "early warning" (targeting early-stage risks) from "alarming" (triggered post-thermal runaway). The technology comparison demonstrates: external signal-based technologies are only suitable for post-thermal runaway alarming; operational data analysis technologies enable risk early warning across all accident stages, including early abnormalities. A market phenomenon exists where alarming technologies are misleadingly promoted as early warning solutions. Engineering application data confirms: the adoption of full-stage early warning technology significantly reduces the occurrence probability of safety risk incidents in stations. Based on this data, a risk probability classification is established. [Conclusion] Operational data analysis-based early warning technology is an effective means for achieving full-stage risk early warning in lithium battery energy storage stations, exhibiting significantly superior performance compared to external signal-based alarming technologies. Market promotion must be regulated, strictly differentiating between early warning and alarming functions. The proposed risk development map, signal identification framework, and graded alert mechanism lay the foundation for an early warning system. Engineering practice should prioritize the selection of full-stage early warning technologies compliant with standards. Actual data validates its effectiveness in significantly reducing risk probability, and the resulting risk classification provides crucial evidence for safety management. Further research into intelligent algorithms and the promotion of technology standardization is recommended.
[Objective] To address the common challenges in current project practices of distributed grid-forming energy storage systems, such as complex communication interactions, extensive equipment retrofitting, and high investment costs, this paper proposes a low-cost, easy-to-implement application scheme and control strategy for distributed grid-forming energy storage systems suitable for scenarios with large geographical coverage and less stringent load reliability requirements. [Method] First, the basic principles of mainstream grid-forming control technologies, namely droop control and virtual synchronous generator (VSG) technology, were introduced, along with the virtual impedance and pre-synchronization techniques required in practical engineering. Subsequently, from the perspectives of individual equipment configuration and overall system control, this study investigated equipment site selection and evaluation methods, the impact of grid-forming energy storage system integration on existing line protection, virtual impedance configuration, and black start issues. [Result] Based on this, the study proposes a scheme to access the "three-remote" (tele-signaling, tele-metering, and tele-control) signals of low-voltage incoming line circuit breakers to maximize the utilization of existing equipment. A "master-slave" ("one-large-supporting-multiple-small") scheme is designed to reduce the system's dependence on the regulation of the upper-level controller, thereby lowering system complexity and minimizing the need for new hardware. To address key issues during the black start process, such as the auxiliary power supply gap, transformer inrush current, and capacitive inrush currents, optimization strategies are devised, including sequencing the auxiliary equipment startup, transformer soft start, and active voltage reduction during closing to mitigate capacitive inrush impacts. The effectiveness of this scheme is demonstrated through engineering application. [Conclusion] This scheme requires minimal grid retrofitting, reduces the coupling degree among equipment, and significantly enhances the feasibility of engineering applications while ensuring renewable energy integration and backup power reliability. It provides a valuable technical reference for the deployment of grid-forming energy storage systems.
[Objective] Against the backdrop of "dual carbon" goals and energy security demands, deep underground energy storage is a crucial approach for large-scale energy storage. Numerical simulation studies are vital for optimizing the design and operation of these systems. This paper focuses on the progress of numerical simulations for major geological storage media (salt caverns, rock caverns, and porous media), and analyzes the key scientific issues and technical challenges in different storage scenarios. [Method] By systematically reviewing domestic and international literature, this paper summarized the numerical simulation methods and findings for hydrogen storage, natural gas storage, and compressed air energy storage from the perspectives of geological characteristics, multi-physics coupling models, and operational parameter sensitivity. Key attention was paid to the thermodynamic response of salt caverns, the structural stability of rock caverns, and the seepage characteristics and cushion gas effects in porous media. [Result] The review shows that: for salt cavern storage, thermo-hydro-mechanical (THM) coupled models offer improved accuracy over conventional models; during the charge-discharge cycles in rock caverns, thermal and density stratification, as well as humidity variations, are observed; in porous media, the type of cushion gas and the characteristics of the geological formation significantly affect storage performance. [Conclusion] Numerical simulations for deep underground energy storage require strengthening research on multi-physics coupling mechanisms, damage evolution of geological media, and long-term cyclic reliability. This will provide theoretical support for the engineering application of geological formations such as depleted oil and gas reservoirs. Future research should focus on the coupling of multiple conditions, leakage prevention and control, and the synergistic utilization of geothermal energy.
