Carbon dioxide-pumped thermal energy storage (CPTES) is an emerging energy storage technology that combines compressed carbon dioxide energy storage with heat pump technology. In the CPTES system, CO2 circulates within a closed loop, eliminating the need for separate CO2 storage. However, conventional CPTES systems suffer from reduced efficiency because electricity is consumed to generate cooling during discharging. To address this limitation, this study proposes a novel CPTES system for combined cooling, heating, and power generation. The proposed system enhances power output by utilizing solar heat energy and recovers waste heat through an absorption refrigeration cycle and an organic Rankine cycle. The evaluation of the novel system performance is performed in terms of thermodynamics and economics. Under design conditions, the novel system can supply 11,335.6 kW of power, 4976.9 kW of heating, and 3252.4 kW of cooling. Compared to conventional systems, the novel system shows significant performance gains: round-trip efficiency increases by 27.82 %, energy efficiency

Liquid air energy storage (LAES) technology is a new type of physical energy storage technology that does not require fossil fuels to supplementary heating and has advantages of low carbon, small geographic limitations and environmental friendliness. Currently, most research on LAES system focuses on thermodynamic analysis, and limited research has been conducted on air pretreatment technology involved in the system. This paper investigates air pretreatment technologies applicable to LAES systems, in which the air pretreatment system includes two parts: air filtration and air purification. The filtration system is studied from the principle of air filtration and forms of filters. The purification system is studied from five aspects, namely, technological route, material, structure, position and operation mode, and the air filtration system and purification system suitable for LAES are designed. The results show that under the condition of the same liquefaction temperature, compared with the basic model without air pretreatment system, the power consumption in compression stage decreases. The work output during expansion increases, and the air liquefaction rate (ALR) and round-trip efficiency (RTE) are slightly lower. Under the same temperature of the outlet of the accumulator and making full use of the cold energy, the improved model, compared with the basic model, has a higher ALR of 1.78% similar to 2.16% and a higher RTE of 1.38% similar to 1.69%.

Compressed Air Energy Storage (CAES) is recognized as a pivotal large-scale, long-duration energy storage solution and has emerged as a critical enabler for maintaining operational stability in next-generation power systems. Salt Cavern Storage (SCS), serving as the cornerstone infrastructure of Salt Cavern Compressed Air Energy Storage (SC-CAES), has been globally prioritized for the deployment of CAES power stations due to its inherent advantages, including stable geological structure, superior sealing capacity, high-pressure gas containment capability, cost-efficient construction, and mature engineering protocols. This review reveals that China possesses substantial salt cavern resources with an estimated storage capacity of approximately 1.3 × 108 m3, yet the current utilization efficiency remains below 0.2%. Techno-economic analysis indicates that SCS offers a significant cost advantage, with a projected future levelized storage system cost between 69–139 USD/kW, substantially lower than alternatives such as artificial caverns or pipeline storage. Furthermore, advanced adiabatic CAES systems integrated with SCS in China have achieved round-trip efficiencies exceeding 70%. Based on the current development status of SC-CAES technology in China and the construction landscape of CAES power stations, this paper systematically reviews the key technological systems of SC-CAES, covering site selection techniques, cavern construction and retrofitting technologies, as well as monitoring and maintenance methodologies. Additionally, it provides a comprehensive assessment of critical aspects such as containment integrity, geometric configuration of caverns, and project economic viability. Finally, the study concludes with forward-looking perspectives on the future development directions of SC-CAES.

Current studies on adsorption CO₂ energy storage systems primarily focus on zeolite-based applications, while comparative studies on systems utilizing different types of porous materials remain scarce. The present paper undertakes a comparative analysis of adsorption CO₂ energy storage systems utilizing three distinct porous materials: 13X zeolite, Mg-MOF-74, and activated carbon. Furthermore, an innovative dual-tank heat storage system is incorporated into the design, aimed at cyclically utilizing the adsorption heat. The findings imply that the system utilizing Mg-MOF-74 demonstrates optimal performance in both thermodynamic and economic aspects. The system utilizing Mg-MOF-74 demonstrated a round-trip efficiency that is 5.47% and 6.20% higher than those employing 13X zeolite and activated carbon. The energy density of the Mg-MOF-74 system is 4.35 and 4.81 times higher than that of the 13X zeolite and activated carbon systems. The system employing Mg-MOF-74 exhibits a dynamic payback period that is 2.85 years and 3.19 years shorter than those of the 13X zeolite and activated carbon systems, respectively. The thermodynamic and economic indicators exhibit distinct variation trends in response to changes in key parameters. Prioritizing economic feasibility, the system can achieve a maximum net present value of $3,753,131.17 at a charge pressure of 13.8 MPa.

Abstract Compressed-gas energy storage is an important technical approach to addressing the fluctuation problem of renewable-energy grid connection. However, in practical applications, challenges are still faced, such as the low utilization rate of waste heat and large throttling losses. The ejector can effectively recover expansion work, reduce throttling losses, and lower the pressure of the cushion gas, and can be integrated with compressed-gas energy storage systems in many efficient ways. This paper systematically reviews the basic principles and development status of compressed-gas energy storage technology, and focuses on analysing the integration methods and application effects of ejectors in different types of energy storage systems. Research indicates that the introduction of an ejector can enhance the cycle efficiency of the system by 2%–4.38%, resulting in an increase of ∼21% in the profit of the system. Additionally, incorporating an ejector can improve the energy storage density of the gas storage facility and enhance the cooling capacity of the system. Finally, based on the current situation, judgments are made on the existing problems and future development directions.

The adsorption carbon dioxide energy storage system offers a high energy density technology route. During the desorption process of carbon dioxide, significant energy consumption can affect the system performance. To address this challenge, a novel solar-assisted adsorption carbon dioxide energy storage system is proposed. The adsorption heat is cascaded through a dual-tank thermal storage, three heaters, an organic Rankine cycle, and a regenerator, which addresses the high energy consumption issue in desorption and significantly improves the utilization efficiency of adsorption heat. Furthermore, a parabolic trough collector is incorporated to assist the system in achieving superior performance. Under the design parameters, the equivalent conversion factor for energy storage, exergy efficiency and energy density of the proposed system can reach 70.13%, 62.64% and 18.51 kWh/m3, respectively. After comprehensive consideration of component exergy destruction and exergy efficiency, heat exchanger 1, cooler 3 and compressor 1 should be prioritized for improvement to reduce energy losses. The analysis of key parameters indicates that when adiabatic efficiencies of compressors and turbines are set at 90% and 92% respectively, the equivalent conversion factor for energy storage and the exergy efficiency can be maximized to 76.73% and 66.21%.

To explore and enhance the multi-cycle performance of a liquid carbon dioxide energy storage cold storage packed bed, this study utilizes finite element simulation techniques to investigate multiple continuous charging and discharging processes in a two-dimensional continuous solid phase model. A composite cold storage packed bed with good performance parameters has been proposed. The study explores the phase transition parameters of the phase change material and the effect of the charging stop temperature on the performance of the cold storage packed bed. The findings reveal that as the charging stop temperature increases, there is an inverse correlation between overall efficiency and charging density. The composite cold storage packed bed can mitigate the issue of a substantial decrease in charging density resulting from the selection of a higher charging stop temperature. Specifically, the best performance composite cold storage packed bed achieves an overall efficiency of 91.18 % and a charging density of 37.39 MJ/kg, which is a 27.48 % improvement over the traditional rock-filled packed bed, with an overall efficiency reduction of only 1.70 %. This research offers a theoretical framework for the optimization and enhancement of cold storage packed bed performance within liquid carbon dioxide energy storage.

The liquefied air energy storage system coupled with coal-fired power unit (CFP-LAES) enhances the peak regulation capability of the unit, facilitating supply-demand balance of the grid. In order to maximize the energy utilization of CFP-LAES system and broaden the application scenarios, a novel CFP-LAES system for the supply of electricity, heat energy and cold energy is proposed in this paper. The output power of CFP-LAES system is improved by introducing an ejector, and the cooling is realized by absorption refrigeration. The thermodynamic model of the multi-generation CFP-LAES system is established and its energy, exergy and economic analyses are carried out. At the same time, the influence of different air liquefaction technologies on system performance is studied. The results show that from the perspective of system efficiency and flexible operation, scheme VI has the best performance, with an energy efficiency of 88.79 % and an exergy efficiency of 66.92 %. The energy density of auxiliary peak regulation of the system is 238.64 kWh/m3, energy density of auxiliary heating is 51.39 kWh/ m3 and energy density of auxiliary cooling is 28.14 kWh/m3. From the perspective of economy, scheme V has the best performance, with a return on investment of 29.52 % and a dynamic payback period of 3.00 years. In addition, the air liquefaction effect of Heyland cycle is the best, and the liquefaction efficiency can reach 88.22 %. The good performance shows that the proposed system has the potential to become a competitive new direction for LAES applications.

The cold storage packed bed is a critical component in liquid air energy storage. To enhance its performance, this study employs numerical simulation techniques, modeling the cold storage bed based on a continuous solidphase model, and investigating the multiple cold storage/release processes of the cold storage packed bed. Owing to the pronounced dynamic characteristics of the cold storage packed bed, the presence of a thermocline can lead to a degradation in their performance. This study analyzed performance improvement methods for filling phase change material in different forms at the top of a packed bed. The addition of a small amount of phase change material can retain the advantage of low cost in packed beds. The research results indicate that the round-trip efficiency of both composite cold storage packed bed and solid-phase cold storage packed bed increases with the increase of cycle times, while their cold storage efficiency and cold storage density decrease with the increase of cycle times. Selecting phase change material with high intermediate phase change temperatures and large volumetric heat capacities aids in achieving superior performance from composite cold storage packed beds. Compared to the solid-phase cold storage packed bed, the composite cold storage packed bed with the best overall performance boasts an increased round-trip efficiency of 0.17 percentage points and a cold storage density enhancement of 15.54%, with the cold storage efficiency dropping by just 1.32 percentage points. By sacrificing a mere fraction of the cold storage efficiency with minimal impact on round-trip efficiency, a substantial increase in cold storage density is realized. This helps meet the significant demand for cold energy as liquid air energy storage develops towards high-capacity units.

Considering excellent physical properties of carbon dioxide, compressed carbon dioxide energy storage has recently become a hot topic of research. The desorption of carbon dioxide in adsorption type carbon dioxide energy storage system requires huge energy consumption, which limits the system application scenarios or affects the system efficiency. Based on the low energy consumption absorption storage of carbon dioxide by guanidine sulfate solution, a novel adsorption type carbon dioxide energy storage system with high energy storage density and high efficiency is proposed to solve the above problems. The thermodynamic and economic models of proposed system are established. Comprehensive performance analysis is conducted in this research to assess the feasibility of proposed system. The analysis indicates the round-trip efficiency and energy density under basic operating condition can reach 71.85 % and 10.22 kWh/m3, respectively. The Net Present Value of the system is $29.12 million. The system round-trip efficiency and energy density can be improved to 73.95 % and 15.53 kWh/m3 when adsorption pressure is reduced to 0.1 MPa. Improving turbomachinery efficiency can significantly reduce system energy loss. The round-trip efficiency can be improved to 78.03 % when the compressor adiabatic efficiency and turbine adiabatic efficiency are increased to 90 % and 92 %.

With the continuous expansion of the scale of power grids, the traditional manual inspection method can no longer meet the real-time operation and maintenance management of transmission lines. At present, the intelligent inspection mode has gradually become a symbol to improve operational efficiency, and the overhead transmission line inspection technology of unmanned aerial vehicle (UAV) is booming. In the field of electric power inspection, the traditional task planning method of UAV has problems such as difficult task planning and weak autonomous control ability. To further enhance the patrol capability of UAV system and improve the efficiency of UAV mission planning, this review paper summarizes and analyzes the existing multi-UAV mission planning technology and looks forward to the development direction of UAV cluster detection technology.

As an energy storage technology, liquid air energy storage (LAES) can assist in peaking for thermal power units and enhance the flexibility of the power system. To prove the feasibility of establishing LAES in thermal power plants in terms of economics, this article establishes the economic model of the coupled system based on the theory of total life cycle cost. Based on two profitability models in three typical cities in China, the cost analysis, profit analysis, evaluation index analysis, breakeven analysis and sensitivity analysis of LAES coupled with thermal power units are carried out. The results show that the establishment of LAES in thermal power plants can be profitable, and the payback periods are within the desired range. The LAES system should select the auxiliary peaking mode when the thermal unit is always operated at low operating conditions. The shortest dynamic payback period of the system is 4.3 years, and the highest return on investment is 41.15 %. The LAES system should select the electricity spot trading model when the thermal unit is always operated at high operating conditions. The shortest dynamic payback period of the system is 10.1 years, and the highest return on investment is 13.04 %.

To address the issue of low energy utilization in the wind hydrogen coupled energy storage (WHES) system, this paper proposes an organic Rankine cycle (ORC) wind hydrogen coupled energy storage (OWHES) system based on the WHES system. The economic calculation model of the WHES system and OWHES system with a capacity of 50 MW are established. The economic feasibility of the system is compared and analyzed by the economic evaluation indicator such as return on investment, payback period and net present value. The results show that the OWHES system has higher return on investment ability, its net present value increased by 43.13 million & YEN;, the static investment payback period shortened by 1.6 years, and the return on investment increased by 1.2 %. The electricity price of the OWHES system needs to be less than 0.3 & YEN;/kWh, otherwise it is not economically feasible. The economic impact of hydrogen production subsidies on the OWHES system is greater than that of electricity generation subsidies. Without subsidies, the hydrogen price needs to be greater than 35.52 & YEN;/kg for the OWHES system to meet the requirements of economic feasibility evaluation indicators.

To investigate the criteria for selecting working fluids in biomass power plants coupled with pump thermal energy storage (PTES) system, two system models, HPO (heat pump only) and CP (complete PTES), were developed. Sensitivity analyses were conducted, and the performance of five commonly used working fluids was compared. The results show that the key factor for HPO is the coefficient of performance (COP) of the heat pump cycle, while for CP, the critical factor is the net power output of the thermal cycle. Roundtrip efficiency can be improved by reducing the compressor inlet temperature, minimizing the heat exchanger terminal temperature difference, and enhancing isentropic efficiency. HPO roundtrip efficiency increases with rising ambient temperatures, whereas CP roundtrip efficiency decreases. High isentropic indices and high, stable specific heat capacities are crucial criteria for selecting working fluids. Exergy analysis reveals that exergy losses primarily occur in turbomachinery for all working fluids. After parameter optimization, the highest roundtrip efficiencies for HPO and CP are achieved with carbon dioxide (54.35%) and argon (61.01%), respectively. Helium provides the lowest compressor and expander investment costs, at $50.86/kW for HPO and $142.23/kW for CP.

Energy storage technology is supporting technology for building new power systems. As a type of energy storage technology applicable to large-scale and long-duration scenarios, compressed carbon dioxide storage (CCES) has rapidly developed. The CCES projects, including carbon dioxide battery in Italy and carbon dioxide storage demonstration system in China, have also been completed. This paper carries out a comprehensive summary and performance comparison of latest developments in CCES, including theoretical research, experimental studies and demonstration projects. Firstly, the principles, performance indicators and application scenarios of CCES are introduced. Secondly, based on the different configurations of CCES, the systems are categorized into standalone and integrated systems. Furthermore, based on the storage methods of carbon dioxide, CCES is subdivided into seven types of storage systems: gas-to-gas, gas-to-supercritical, gas-to-liquid and liquid-to-liquid, among others. The research progress of each type of system is discussed. Their performance is compared in tabular form. In addition, the experimental research and demonstration projects related to CCES technology are presented. Finally, the advantages and limitations of CCES systems are discussed. The suggestions and prospects for future research and development in CCES are offered.

Liquid gas energy storage has the advantages of being safe and environmentally friendly, with high energy density and large capacity. The performance and normal operation of the Liquid gas energy storage system will be directly impacted by the cold storage device. This study is conducted under the simulation conditions specified by liquefied carbon dioxide energy storage for the cold storage device, utilizing air as the intermediate heat exchange fluid. Based on the deep charging condition as the baseline, delves into the impact of different cold storage stop factors and the effects of the first and regular cycles on the performance of the cold storage packedbed, with a focus on the cold energy loss caused by the temperature gradient layer. The results show that the discharging efficiency and the charging/discharging utilization ratio decrease with an increase in the cold storage stop factor, while the charging efficiency gradually improves. In the first cycle, due to its lower discharging efficiency, the overall efficiency first increases and then decreases with the increase in the cold storage stop factor, reaching a peak of 61.98 % at 0.65. In regular cycle, the trend of the overall efficiency is opposite to that of the charging/discharging utilization ratio, hence, when selecting the high cold storage stop factor to enhance the overall efficiency, it is necessary to consider the waste of effective charging capacity. The theoretical guidance for the design and operation of the cold storage packed-bed in the liquid gas energy storage system can be provided by this study.

The proportion of wind power generation is increasing, and the wind abandonment problem is gradually highlighted. The hydrogen energy and wind power coupled will handle the "wind abandonment" issue. However, existing research indicates that the wind hydrogen coupling system will generate a large amount of waste heat, and the efficiency of electric hydrogen electric conversion is not high. This study built a novel wind-hydrogen energy storage system for waste heat utilization. This novel system enables the triple supply of electricity, hydrogen and heat through waste heat utilization. In this study, a dynamic and thermodynamic model of the system is developed. Based on the laws of thermodynamics, the system model for exergy analysis is developed. The system is analyzed for both exergy efficiency and exergy destruction. The results show that the alkaline electrolyzer shortens the start-up time through waste heat recovery. The fuel cell-organic Rankine cycle (FCORC) combined cycle increased the power generation by 3541 kWh, and the exergy efficiency increased by about 3.6 %. The electric hydrogen electric conversion efficiency of the storage system is improved by 4.5 %, and exergy efficiency is improved by 3.5 %. Exergy destruction of the system is mainly concentrated in alkaline electrolyzer and fuel cell.

Isothermal compressed gas energy storage (I-CGES) systems are widely recognized for their simplicity and high cycle efficiency. However, challenges such as limited energy storage density and suboptimal thermodynamic performance remain. In this study, an innovative isothermal compressed carbon dioxide energy storage (I-CCES) system is proposed, which utilizes a dual-liquid piston structure and uses carbon dioxide as the working medium, taking full advantage of the superior thermal conductivity of carbon dioxide. A comprehensive model is developed to evaluate the system performance, and the main indexes include energy storage density, round-trip efficiency and compression/expansion efficiency. The effects of ambient temperature, pressure parameters and flow rate were systematically analyzed. The results show that the system has an energy storage density of 0.404 kWh/m3, round-trip efficiency of 58.24 % and an indicated efficiency of 74.48 % under the design parameters. By optimizing the ambient temperature (296.15-300.15 K), minimum pressure (2.0-3.0 MPa) and maximum pressure (5.0-6.0 MPa), the round-trip efficiency and energy storage density can be increased to 64.54 % and 0.409 kWh/m3, respectively. It is noteworthy that the flow rate variation has a negligible effect on the efficiency, which emphasizes the robustness of the system under dynamic operating conditions.

The future energy landscape is expected to increasingly rely on green hydrogen as a carrier for variable renewable energy, particularly to facilitate the decarbonization of hard-to-abate sectors. Off-grid hydrogen production has emerged as a promising solution, offering a pathway to minimize carbon intensity while ensuring the economic viability of hydrogen generation. This study simulates the operation of an isolated power system by integrating wind, solar, and hydrogen production, utilizing real-time weather data to explore the wind-solar capacity ratio for maximizing the operational hours of hydrogen electrolysers. The levelized cost of electricity and the levelized cost of hydrogen (LCOH) for these off-grid systems are evaluated across four representative locations in northern China and compared with fossil-based hydrogen (steam methane reforming/coal gasification). The findings indicate that, in northern China, the optimal wind-to-solar capacity ratio for maximizing hydrogen production falls within the range of 2.0-2.75. Under this configuration, the lowest achievable LCOH is 27.17 CNY/kg (similar to 3.77 USD/kg), offering a significant advantage in terms of negligible carbon emissions compared with fossil-based hydrogen. Furthermore, a 40% reduction in the unit fixed costs of wind turbines, solar photovoltaic systems, and electrolysers is projected to lower the LCOH by 8.33 CNY/kg (23.29%), 3.12 CNY/kg (8.73%), and 2.54 CNY/kg (7.10%), respectively. These findings underscore the potential of off-grid wind-solar hybrid hydrogen production as a viable and sustainable alternative. Greater policy support and increased investment are essential to accelerating the deployment of such systems and realizing their full potential in the clean-energy transition. The operation of an isolated power system integrating wind, solar, and green hydrogen production is simulated utilizing real-time weather data to explore the wind-solar capacity ratio for maximizing the operational hours of hydrogen electrolysers.