Compressed Air Energy Storage System Research Articles

Study on start-up characteristics of single piston free piston linear generator for small-scale compressed air energy storage system

This study presents a new idea of applying single piston free piston linear generator (FPLG) to small-scale compressed air energy storage (CAES) system. Firstly, a single piston FPLG prototype for CAES is built. Then, the thermodynamic, motion and output characteristics of FPLG during start-up process are studied based on the experimental data. The results show that the start-up process of single piston FPLG can be divided into three stages, and the order of achieving a steady state is movement and output > in-cylinder pressure > the in-cylinder temperature. The in-cylinder temperature increases in a spiral pattern, and the temperature difference between adjacent cycles at the same state point decreases. In the 0th cycle, when the free piston assembly (FPA) moves from top dead center (TDC) and bottom dead center (BDC), the peak current and power output are greater than the other cycles. The peak current and power output when FPA moves from TDC to BDC are greater than those when FPA moves from BDC to TDC. The maximum current and power output can reach 0.8 A and 62.25 W. At the beginning of the expansion stage, as the intake duration (tin) increases, the in-cylinder pressure increases first and then decreases. As the intake pressure (pin) increases, the in-cylinder pressure continues to increase. In addition, the in-cylinder temperature of working chamber A (TA) is lower than in-cylinder temperature of working chamber B (TB), and the temperature difference between TA and TB can reach 12.4 K. At higher pin condition, the intake point cannot be too close to the two ends and tin cannot be too long. At lower pin condition, the intake point cannot be too close to both ends and tin cannot be too short to ensure the system starts. The purpose of this paper is to provide valuable insights and guidance for the practical application of small-scale CAES system.

Proposal design and thermodynamic optimization of an afterburning-type isothermal compressed air energy storage system integrated with molten salt thermal storage

The isothermal compressed air energy storage is a potential technique for large-scale energy storage. In this study, the molten salt thermal storage is integrated with the afterburning-type isothermal compressed air energy storage system, which uses liquid piston compression technique, to enhance the thermal performances. Thermodynamic models of the hybrid energy storage system were developed, and the genetic algorithm was used to optimize multiple parameters to enhance the energy efficiency. Four operation modes, i.e., the high, medium-high, medium-low, and the low output power modes were proposed, to enhance the operational flexibility of the hybrid energy storage system. When the system operates in the operation mode of medium-low output power, a portion of afterburning heat is stored in the molten salt and used in the operation mode of low output power. Results show that the roundtrip efficiency of high, medium-high, medium-low, and the low output power modes are 63.57 %, 59.33 %, 57.13 %, and 83.28 %, respectively. Exergy analysis was carried out to quantify the irreversibilities of key components. In the three modes of operation with afterburning, the combustion chamber has the highest portion of exergy loss, and in the operation mode without afterburning, the exergy loss of heat exchangers is higher than that of expanders.

A Perspective on the Process and Turbomachinery Design of Compressed Air Energy Storage Systems

Abstract The present paper will describe the Baker Hughes experience in the development of the turbomachinery equipment for Hydrostor's advanced compressed air energy storage (A-CAES) system. At the core of a compressed air energy storage (CAES) plant, there is an air compressing system, followed by an air expander used to recover the stored energy. To achieve a reliable and effective solution, the expander is obtained from the architecture of Baker Hughes steam turbines, which was adapted to match the specific process needs. The criticalities that were addressed and solved to derive the expanders from the original steam turbine are presented. Specifically, the paper describes the activities performed to optimize the inlet and exhaust sections of each segment, the development of the blades for high atmospheric volume flow, and the implications that thermal transients have on the machine reliability. The inlet and exhaust sections were arranged according to the layout constraints, which were set to mitigate the effects of the thermal stresses and to reduce the weight to facilitate the machine transportation, while maintaining high aero-performance. As for the expander, a single-body configuration was selected to optimize capital expenditures and reduce leakage to atmosphere. A new set of blades derived from Baker Hughes's Steam Turbine stages were developed. This new stage is characterized by rotating blades with high radius ratio (HRR); therefore, an optimization strategy was adopted to include the mechanical constraints from the beginning of the design cycle and obtain a final geometry that can be used with different flow path and operating conditions. Finally, the three-dimensional full Navier Stokes Computational fluid dynamics analysis was used to assess the performance of the new stages in nominal and off-design conditions. A detailed analysis of the thermal transient of the expander parts with finite element analysis methods was performed to assess the life expectations of the equipment. The finite element analysis results are discussed in the paper to show the capability of the machine to sustain an extremely fast start up sequence. Compressor train is characterized by a multiple body configuration. A detailed optimization was performed to improve the efficiency and the availability of the selected solution. The low-pressure axial compressor discharge section has been optimized to reduce losses and a detailed study of rotor has been performed to evaluate the capability to withstand a high number of start and stop cycles.

Thermodynamic and economic analysis of a novel compressed air energy storage system coupled with solar energy and liquid piston energy storage and release

Compressed air energy storage (CAES) is one of the important means to solve the instability of power generation in renewable energy systems. To further improve the output power of the CAES system and the stability of the double-chamber liquid piston expansion module (LPEM) a new CAES coupled with liquid piston energy storage and release (LPSR-CAES) is proposed. The coupled LPEM conducts suction stage B at the end of the expansion stage, ensuring stable exhaust pressure and temperature for the module. By establishing the thermodynamic and economic models of LPSR-CAES, the effect laws of key node parameters on the system performance are investigated. The results show that the heat transfer between liquid droplets and air dominates the heat transfer in LPEM. The proposed LPEM exhibits excellent isothermal performance and stability, with a maximum temperature difference of about 20 K during the cycle, and stable exhaust temperature changes within 10 K. Under the design conditions, the converted electrical efficiency, round-trip efficiency, exergy efficiency and net present value of the system are 68.31 %, 58.86 %, 66.99 % and 12.25 M$ respectively. The higher the solar supplement temperature, the more outstanding the thermal and economic performance of the system. The short-term energy storage system performance of the proposed system is more prominent. Based on the actual light data, the system can achieve 72.09 % and 69.41 % of converted electrical efficiency and exergy efficiency, respectively, at the 219th day. The results of this study provide theoretical support for the engineering application of the proposed system.

Performance analysis of a novel medium temperature compressed air energy storage system based on inverter-driven compressor pressure regulation

Performance analysis of a novel medium temperature compressed air energy storage system based on inverter-driven compressor pressure regulation

Loss characteristics and optimization method of a compressed air energy storage radial turbine with nozzle governing

During the operation of the compressed air energy storage (CAES) system, a discrepancy exists between the air storage pressure and the turbine inlet pressure. At the same time, to ensure that the turbine operates efficiently when the system load varies, the turbine needs to be regulated reasonably. In this paper, the influence of three nozzle governing (NG) parameters on turbine performance during the NG process is investigated: the inlet pressure of the NG region, the area of the NG region, and the base pressure. The flow characteristics and loss mechanisms under partial admission conditions and NG conditions are also analyzed. Furthermore, the NG process is optimized by using a transition section. The results show that the loss under the NG condition with low inlet pressure at the NG region is similar to the partial admission loss, both of which are mainly affected by the area of the NG region. In both working conditions, vortex structures appear at the stator outlet of the NG region. At the same time, the mixing of different airflows and the flow separation phenomenon within the rotor leads to a significant increase in entropy production rate. The transition section can attenuate the leakage and reduce the entropy production rate in the radial gap between the stator and rotor, increasing turbine efficiency by up to 1.1 % at maximum when using the transition section.

Dynamic modeling and analysis of compressed air energy storage for multi-scenario regulation requirements

Compressed air energy storage (CAES) technology has received widespread attention due to its advantages of large scale, low cost and less pollution. However, only mechanical and thermal dynamics are considered in the current dynamic models of the CAES system. The modeling approaches are relatively homogeneous. CAES power stations have gradually increased the demand for auxiliary services such as frequency modulation mode and voltage regulation mode in addition to the peak regulation mode. Therefore, it is urgent to pay attention to the dynamic response characteristics at shorter time scales. Due to the lack of an accurate and complete dynamic model of the CAES system for multi-scenario adaptation requirements, the development of system optimization design and control technology has been severely limited. The paper establishes a dynamic model of advanced adiabatic compressed air energy storage (AA-CAES) considering multi-timescale dynamic characteristics, interaction of variable operating conditions and multivariate coordinated control. The simulation data is compared with the measured data of the peak regulation, frequency regulation and voltage regulation scenarios of the Jintan Salt Cave CAES (JTSC-CAES). The results show that the deviation of the dynamic model is <7 %, which verifies the validity and accuracy of the proposed AA-CAES dynamic model. The established model and research results provide the theoretical model foundation for dynamic characteristic research, system design and optimization control of the JTSC-CAES.

Multi-region coupling computational fluid dynamics simulation of the underground compressed air energy storage process

Compressed air energy storage (CAES) in underground spaces is a common method for addressing the instability of renewable energy generation. As the construction and testing of CAES systems are often of high cost, the numerical simulation which offers a more efficient and low-cost research method can provide a better alternative to research the process. In this study, a numerical simulation model has been developed to describe the air movement within the CAES process. Specifically, the study focuses on two different types of motion: air compressible flow within the cavern and air porous flow in the surrounding rock. Using OpenFOAM, a multi-region coupling solver has been developed to address the different governing equations for these two types of motion, and couples pressure, velocity, and temperature at the boundaries. The developed solver is used to simulate a field test of a CAES system. The numerical simulation results closely match the experimental data, verifying the reliability of the solver. Moreover, the solver can achieve multi-region flow simulations that are previously unattainable, resulting in more accurate simulations. Simulations have also been conducted to analyze various working conditions, including different rock permeability, porosity, and air injection mass rates. The results show that different conditions significantly affect air pressure, leakage rate, temperature, and flow field changes within the cavern. These simulation results and the underlying mechanisms have been analyzed to provide reference and technical support for site selection, construction, and operational strategies of CAES systems in underground spaces.

Simulation-Based Hybrid Energy Storage Composite-Target Planning with Power Quality Improvements for Integrated Energy Systems in Large-Building Microgrids

In this paper, we present an optimization planning method for enhancing power quality in integrated energy systems in large-building microgrids by adjusting the sizing and deployment of hybrid energy storage systems. These integrated energy systems incorporate wind and solar power, natural gas supply, and interactions with electric vehicles and the main power grid. In the optimization planning method developed, the objectives of cost-effective and low-carbon operation, the lifecycle cost of hybrid energy storage, power quality improvements, and renewable energy utilization are targeted and coordinated by using utility fusion theory. Our planning method addresses multiple energy forms—cooling, heating, electricity, natural gas, and renewable energies—which are integrated through a combined cooling, heating, and power system and a natural gas turbine. The hybrid energy storage system incorporates batteries and compressed-air energy storage systems to handle fast and slow variations in power demand, respectively. A sensitivity matrix between the output power of the energy sources and the voltage is modeled by using the power flow method in DistFlow, reflecting the improvements in power quality and the respective constraints. The method proposed is validated by simulating various typical scenarios on the modified IEEE 13-node distribution network topology. The novelty of this paper lies in its focus on the application of integrated energy systems within large buildings and its approach to hybrid energy storage system planning in multiple dimensions, including making co-location and capacity sizing decisions. Other innovative aspects include the coordination of hybrid energy storage combinations, simultaneous siting and sizing decisions, lifecycle cost calculations, and optimization for power quality enhancement. As part of these design considerations, microgrid-related technologies are integrated with cutting-edge nearly zero-energy building designs, representing a pioneering attempt within this field. Our results indicate that this multi-objective, multi-dimensional, utility fusion-based optimization method for hybrid energy storage significantly enhances the economic efficiency and quality of the operation of integrated energy systems in large-building microgrids in building-level energy distribution planning.

Thermodynamic performance analysis of a new air energy storage multigeneration system

This paper proposes a chemical looping hydrogen generation-solid oxide fuel cell combined cooling, heating, and power system that utilizes compressed air energy storage and liquefied natural gas, aiming to address the issues of instability in renewable energy power generation and waste of liquefied natural gas cold energy. The scheme achieves CO2 capture and efficient power generation while also addressing grid fluctuations and the utilization of waste cold energy. The compressed air energy storage system is employed to supply air centrally, eliminating the power consumption of traditional air compressors while improving discharging efficiency. Aspen Plus software and embedded Fortran are used for system simulation. The system is comprehensively evaluated through energy analysis, exergy analysis, and sensitivity analysis. The results indicate that the discharging efficiency, energy round-trip efficiency, and round-trip electrical efficiency are 87.56%, 81.57%, and 67.82%, respectively. The purity of CO2 capture is 99.72%. Sensitivity analysis indicates that the outlet pressure of the air storage tank and fuel flow are the main influencing parameters for system performance. Increasing the fuel flow can effectively enhance system power output, but efficiency will decrease. The outlet pressure primarily influences the power output of the gas turbine and discharging time. Overall, this system provides theoretical guidance and new ideas for efficient energy utilization.

Thermodynamic analysis of an advanced adiabatic compressed air energy storage system integrated with a high-temperature thermal energy storage and an Organic Rankine Cycle

Advanced adiabatic compressed air energy storage (AA-CAES) system has drawn great attention owing to its large-scale energy storage capacity, long lifespan, and environmental friendliness. However, the performance of the air turbine during the discharging process is limited by the low temperature of the compression heat. Thus, this study proposes an integrated AA-CAES system incorporating high-temperature thermal energy storage and an Organic Rankine Cycle (ORC). The high-temperature thermal energy storage is introduced to heat the discharging compressed air to enhance the air turbine performance, and the Organic Rankine Cycle is integrated to utilize the waste heat. Notably, two preheaters are deployed in a special tandem to recover the heat from the air exiting the turbine and the water exiting the hot water tank, respectively. This paper develops a thermodynamic model to simulate the proposed system, assessing the effects of heat storage temperature, ambient temperature, and inlet conditions of the air turbine on performance metrics, including exergy efficiency and exergy destruction. The simulation results indicate that, compared to thermal oil and Hitec salt, employing solar salt as the heat storage medium for the solar thermal collection and storage unit yields the best performance. The energy storage efficiency, roundtrip efficiency, exergy efficiency, exergy conversion coefficient, and energy storage density of this system are 115.6 %, 65.7 %, 78 %, 79.4 %, and 5.51 kWh/m3, respectively. Exergy analysis reveals that the exergy efficiency of interheaters (IH) is the lowest at 76.7 %, while air turbines (ATBs) exhibit the highest exergy efficiency at 91.2 %. Moreover, due to the irreversible processes of compression, expansion, and throttling, ATBS, compressors, and throttle valves collectively contribute to an exergy destruction rate as high as 79.2 %. The parameter analysis demonstrates that low ambient temperature, high inlet temperature, and high inlet pressure of the air turbine enhance energy storage performance.

Performance analysis of a novel multi-machine compensable pumped hydro compressed air energy storage system

Many pumped hydro compressed air energy storage systems suffer from large head variations in the hydraulic machinery. To address this defect, this study proposes a multi-machine compensable pumped hydro compressed air energy storage system and reveals its operational, energy, exergy, and economic performances. First, the energy, exergy, and economic models of the system are established. Second, the operational characteristics of each component are analyzed. Third, the energy, exergy, and economic performances of the system are presented. Finally, the impact of operating pressure on the energy and exergy performance is analyzed. The results indicate that air pressure variations of 0.300 MPa/0.256 MPa in Tank 1 are reduced to head variations of 11.0 m/12.7 m at the hydraulic machinery, respectively. Furthermore, the round-trip efficiency, exergy efficiency, and energy storage density reached were 0.672, 0.694, and 0.038 kW·h/m3, respectively. The most significant work wastage and exergy loss occurred in Tanks 1 and 2, contributing to 48.5 % and 37.5 % of the total, respectively. As the operating pressure increases, the round-trip and exergy efficiencies decrease, and the energy storage density increases. In this study, the head amplitude at the hydraulic machinery under charging and discharging conditions was reduced by nearly 2/3 and 1/2, respectively.

Dynamic simulation and optimal design of a combined cold and power system with 10 MW compressed air energy storage and integrated refrigeration

A combined cold and power system with 10 MW compressed air energy storage and integrated refrigeration (CCR) is proposed. In traditional 10 MW compressed air energy storage (CAES) system, outlet pressure of air tank is throttled to a low pressure by throttling device. In CCR system, the throttling device is replaced by a piston turbine to achieve control of pressure and mass flow. Meanwhile, pressure potential energy of compressed air is converted to mechanical work, which is used to drive refrigeration subsystem. The dynamic mathematic model of proposed CCR system is built up. According to energy and exergy analysis of the whole dynamic process, it is confirmed that the proposed model obeys the first and second laws of thermodynamics. The optimal solution for T23 and γAC are calculated to be 259.6896 K and 1.2335, respectively. The Pareto frontier of multi-objective optimization of energy and exergy efficiencies are conducted. Energy efficiency of proposed CCR system is higher than that of CAES system by at least 32.8 %. The electrical efficiency of proposed CCR system is also higher than that of CAES system. It suggests that the pressure potential energy wasted in the throttle process is well utilized by the piston turbine in CCR system.

Experimental study on single-cylinder two-stroke piston expander based on in-cylinder spray heat transfer

Compressed air energy storage stands as a highly promising technology within the realm of energy retention. The piston expander finds applicability in smaller-scale compressed air energy storage systems. In compressed air energy storage systems, the expansion process is critical in energy discharge and significantly impacts overall performance. Isothermal expansion techniques are effective in enhancing the operational efficiency of piston expanders, in contrast to adiabatic expansion methodologies. Previous simulations by our research group show that the isothermal expansion model has a lower power output than the adiabatic expansion model due to its higher exhaust pressure. To further validate the accuracy of the simulation results, an experimental platform was constructed and the uncertainty of the experimental system as well as the measured data was evaluated. This study conducted experimental research using the single-variable method, focusing on different load conditions and spray parameters. The study findings indicate that the exhaust pressure during isothermal expansion consistently exceeds that of adiabatic expansion. The exhaust pressure of isothermal expansion increased by 3.85 % to 14.9 %. Under varying load conditions, the average rotational speed and output power of isothermal expansion were noted to be inferior to those of adiabatic expansion. Despite changes in nozzle diameter or spray temperature when the spray timing is set at 0°-180°, the average rotational speed and output power of isothermal expansion remain lower than that of adiabatic expansion. The average output power of isothermal expansion decreased by 1.29 % to 5.24 %. Nevertheless, if the spray timing is set between 0°-120°, the average output power of the isothermal expansion surpasses the adiabatic expansion with an improvement of 1.84 %.

Techno-economic assessment of vertical axis wind turbine driven RO desalination with compressed air energy storage for remote communities

Renewable energy desalination is gaining much attention in remote off-grid communities facing challenges in accessing clean water. Typically, batteries ensure the continuous operation of small-scale renewable reverse osmosis (RO) desalination systems; however, they are expensive and have relatively shorter lifespans. This study investigates the implementation of a compressed air energy storage (CAES) system coupled with a vertical axis wind turbine (VAWT) to directly drive small-scale RO desalination, potentially replacing batteries and reducing energy conversions. A Simulink model was developed to simulate the performance of a VAWT-driven CAES operating RO units, adaptable for both technical and economic assessments. Parametric studies have identified the optimal configuration. The most cost-effective configuration, utilising eleven VAWTs and a pressure exchanger (PX), achieves a levelised cost of water (LCOW) of 1.63 US$/m3 and an annual water production of 9400 m3. The normalised daily water production per square metre of turbine swept area at the study site is 0.19 m3/m2/day at an average wind speed of 5 m/s. While this configuration has a higher initial capital cost, it yields the lowest LCOW. The CAES system effectively addresses the intermittency challenges of wind energy. This study presents a novel, battery-free VAWT-CAES-RO system as a sustainable desalination solution for remote communities, offering a promising approach to address water scarcity in an environmentally friendly manner.

Capacity configuration of compressed air energy storage systems with consideration of variable operating conditions

Abstract The extensive integration of high proportions of new energy poses difficulties to the secure and stable operation of power systems. Compressed air energy storage (CAES) technology, as a large-scale, long-duration energy storage technology, has garnered significant attention. However, CAES systems often work in off-nominal conditions, leading to the issue that capacity configured based on nominal conditions may struggle to meet the demands of wind and solar energy consumption. This paper conducts an in-depth study of the off-nominal operation characteristics of CAES systems, constructs a variable operation condition configuration model for CAES systems, and proposes a configuration method for scenarios involving wind and solar energy consumption. Numerical examples have proven that the proposed configuration method can effectively mitigate the fluctuation of new energy output and satisfy the demand for combined heat and power supply.

Optimal dual-pressure evaporation organic Rankine cycle for recovering waste heat from compressed air energy storage (CAES)

Compressed Air Energy Storage (CAES) is an effective solution to the problems of the intermittency and volatility of renewable energy. However, the process of compressing air consumes energy and converts it into low-temperature waste heat, limiting the improvement of round-trip efficiency. This paper introduces the dual-pressure evaporation organic Rankine cycle (ORC) to recover the waste heat from the CAES system compression process, which enhances the round-trip efficiency. Optimal working fluids and design schemes of parallel and series dual-pressure evaporation ORCs are analyzed. The thermodynamic performance of two cycle types is compared. The exergy loss distribution characteristics of the dual-pressure evaporation ORC are explored, and the impact on the round-trip efficiency of the CAES system is evaluated. Results show that the parallel dual-pressure evaporation ORC has better performance with an optimum working fluid of R1234yf and a maximum waste heat conversion efficiency of 9.3 %. The round-trip efficiency of the CAES system will be relatively increased by 5.2 % by introducing the parallel dual-pressure evaporation ORC. The maximum exergy efficiency of the parallel dual-pressure evaporation ORC is 52.8 %, and the condenser and low-pressure stage expander have larger exergy losses, accounting for 33.8 % and 22.0 % of the total losses, respectively.

Dynamic analysis of an adiabatic compressed air energy storage system with temperature-regulated in air tanks

In this study, an innovative temperature regulation method is developed to augment the air storage capacity of adiabatic compressed air energy storage. Hot water, produced by recovering waste heat from the discharging process, is injected into these tanks to control the air temperature as needed. The transient-state calculation models have been established for each component, and validation is performed using experimental data obtained from published work. The utilization of proportion integration differentiation control technology enables precise regulation of the air outlet temperature of heat exchangers, achieving a control accuracy of 1K. The operational status of the components has been investigated, and a comparison is made between the performances of the modified and traditional adiabatic compressed air energy storage systems. The comparative analysis results show that the modified system can achieve a notable round trip efficiency of 71.71 %, which is comparable to that of conventional system (71.41 %). The effective air storage density of the modified system is 47.24 kg/m3, which presents a 15.08 % increase compared to traditional system (41.05 kg/m3). The influence of discharge pressure and pressure difference between threshold pressure and discharge pressure is also investigated. It is found that the modified adiabatic compressed air energy storage shows a consistently greater effective air storage density than traditional system, with a minimum increase exceeding 10.52 %.

A comprehensive performance comparison between compressed air energy storage and compressed carbon dioxide energy storage

Currently, working fluids for adiabatic compressed energy storage primarily rely on carbon dioxide and air. However, it remains an unresolved issue to which of these two systems performs better. Therefore, this paper compares the advantages and disadvantages of both systems in terms of thermodynamic and economic performances under the given boundary conditions. To accurately obtain the performance of energy storage systems, quasi-dynamic models are established for key components. On this foundation, corresponding thermodynamic-economic models are developed. The results indicate that at thermal storage temperatures of 120 ℃, 140 ℃, and 160 ℃, 100 MW×5h compressed carbon dioxide energy storage systems have higher round-trip efficiencies than compressed air energy storage systems. However, the compressed carbon dioxide energy storage also faces the difficulties of higher cost and longer payback period. Specifically, at the thermal storage temperature of 140 ℃, round-trip efficiencies of compressed air energy storage and compressed carbon dioxide energy storage are 59.48 % and 65.16 % respectively, with costs of $11.54 × 107 and $13.45 × 107, and payback periods of 11.86 years and 12.57 years respectively. Compared to compressed air energy storage system, compressed carbon dioxide energy storage system has 9.55 % higher round-trip efficiency, 16.55 % higher cost, and 6 % longer payback period. At other thermal storage temperatures, similar phenomenons can be observed for these two systems. After comprehensively considering the obtained thermodynamic and economic performances, the overall performance of compressed air energy storage is superior to that of compressed carbon dioxide energy storage. In addition, in practical engineering, key components of compressed air energy storage are more mature than those of compressed carbon dioxide energy storage, and air has higher safety than carbon dioxide. In the future work, the comparison for performances between different types of compressed carbon dioxide energy storage and compressed air energy storage should be taken into account, and dynamic models of the systems should be developed. Additionally, the industry chain of compressed carbon dioxide energy storage should be accelerated to reduce equipment costs, enabling it to compete with compressed air energy storage.

Airtightness evaluation of lined caverns for compressed air energy storage under thermo-hydro-mechanical (THM) coupling

Large-scale compressed air energy storage (CAES) technology can effectively facilitate the integration of renewable energy sources into the power grid. The airtightness of caverns is crucial for the economic viability and efficiency of CAES systems. This paper presents a new thermo-hydro-mechanical (THM) model for investigating the effects of complex thermodynamic changes on air leakage in concrete-lined rock caverns. The model is validated using field measurement data, numerical simulations, and analytical solutions. Subsequent simulations were conducted to analyze air leakage, pore pressure, and leakage range under various operating conditions. Finally, the impacts of different parameters on air tightness were assessed. The results indicate that the daily air leakage mass percentage (TDALMP) in the concrete-lined CAES cavern is 0.60 % under the operating pressure of 4.5–10 MPa, which meets the tightness requirement. The permeability of the lining is a key parameter for airtightness, in this case, the permeability of the concrete lining cannot exceed 1 × 10−19 m2. The daily air leakage rate can be reduced by modestly increasing the cavern radius, lowering the temperature of the injected air, and decreasing the maximum operating pressure. These results can provide a reference for the study and construction of CAES caverns in similar projects.