Compressed Air Energy Storage System Research Articles

Design of Underwater Compressed Air Flexible Airbag Energy Storage Device and Experimental Study of Physical Model in Pool

Renewable energy is a prominent area of research within the energy sector, and the storage of renewable energy represents an efficient method for its utilization. There are various energy storage methods available, among which compressed air energy storage stands out due to its large capacity and cost-effective working medium. While land-based compressed air energy storage power stations have been constructed worldwide, their efficiency remains low. Underwater compressed air energy storage has the potential to significantly enhance efficiency, although no such device currently exists. This paper presents the design of an UWCA-FABESD utilizing five flexible air bags for underwater gas storage and discharge. Additionally, it introduces the working principle of the adiabatic underwater compressed air energy storage system and device. Furthermore, a small-scale physical model with similar functionality was designed and manufactured to simulate the charging process of the air bag in onshore charging and discharging tests as well as posture adjustment and lifting arrangement tests, along with underwater charging and discharging tests. These experiments validated the related functions of the designed underwater compressed air flexible bag energy storage device while proposing methods for its improvement. This research provides a new approach to underwater compressed air energy storage.

Adaptive hybrid energy system for remote Canadian communities: Optimizing wind-diesel systems integrated with adiabatic compressed air energy storage

This study addresses gaps in the integration of compressed air energy storage (CAES) with wind-diesel systems in remote areas, departing from previous research that mostly focused on diesel engine efficiency. Critical factors such as CAES sizing, design, and operation are thoroughly examined through a comprehensive analysis, including power supply–demand patterns and full-year system performance. Utilizing Kangirsuk, an Inuit village, as a case study, the research introduces a novel optimization-based sizing strategy for a small-scale adiabatic CAES (A-CAES) system integrated into a wind-diesel power plant. The study contributes by providing insights into power supply–demand patterns, proposing an optimization strategy for adaptive hybrid energy systems, and evaluating the performance of CAES systems over a year. Results show significant diesel fuel reductions, with a 55% reduction in diesel consumption for a single wind turbine with a CAES system, and an even greater reduction of 63.4% when employing two wind turbines with a CAES system. The diesel fuel savings are determined for oversized CAES systems, indicating that oversizing can improve the system’s diesel fuel independence up to 65.3%, albeit at a higher cost. The capital costs associated with achieving these reductions are $5,088,000 for the 55% reduction, $8,020,000 for the 63.4% reduction, and $11,520,000 for the 65.3% reduction. The cost-effectiveness analysis reveals that while oversizing contributes to enhanced fuel savings, the associated expenses need to be carefully considered in balancing diesel fuel independence gains against economic investment.

Energy loss analysis in two-stage turbine of compressed air energy storage system: Effect of varying partial admission ratio and inlet pressure

The compressed air energy storage (CAES) system experiences decreasing air storage pressure during energy release process. To ensure system stability, maintaining a specific pressure difference between air storage and turbine inlet is necessary. Hence, adopting a judicious air distribution scheme for the turbine is crucial. Partial admission, based on reasoned nozzle governing methods, enhances system performance. This investigation explores the impact of varying partial admission ratio (PAR) and inlet pressure on flow dynamics and loss characteristics under rated output power. Full circumferential numerical simulations of a two-stage axial turbine within CAES system elucidates insights. First-stage efficiency declines linearly with decreasing PAR, while second-stage displays escalating reductions. Principally, turbine energy losses primarily stem from the entropy production rate (EPR) by turbulent dissipation and EPR arising from heat transfer with fluctuating temperature gradients. Partial admission significantly affects losses within the rotor, especially within the second stage. Leaving velocity loss for 50 % PAR is about 3 times that of 100 % PAR. The percentage of losses within R2 for 50 % PAR increases by 6.7 % compared with that for 100 % PAR. This research provides theoretical insights for designing, regulating, and optimizing nozzle governing and partial admission turbines in CAES systems.

Experimental investigation of camless air engine to improve performance by the novel controller and exhaust pressure predicting technique

In the face of the climate crisis, hike in prices of petroleum products, and limited gasoline sources, it is imperative to explore the possible opportunities in the field of energy transformation technology. Non-conventional and non-hazardous green fuel-air engine technology has proven to have a promising future in propulsion technology. In the air engine, the camless mechanism has created scope for research by replacement option of cam-follower with variable valve train (solenoid valve), which can be controlled electronically. In this paper, work is done on the operational parameters (i.e., cycle time, flow rate, and crank position) of camless air engines and proposed a controlling mechanism with experimental results to improve the system's efficiency. Control of intake duration maximizes the utilization of input compressed air power by allowing the optimum amount of air to expand fully. The novel controller was designed, developed, and tested, which controls the engine intake duration by estimating exhaust pressure. A prototype model was built with an electronic control circuit and pneumatic system, which records signals of operational parameters with the help of feedback sensors and controls the engine's intake duration at different operating pressure ranging from 3 to 6.5 bar. Experiments were conducted, and the results of two cycles were compared, case-I, where compressed air is continuously supplied from 0° to 170° of crank angle, and case-II controlled cycle, which controls intake duration by estimating exhaust pressure. Results show the average efficiency improvement of 11.91 % in case-II compared to case-I and also improvement in work done and RPM (Revolution per Minute) of the cycle. Thus, the control system in a camless air engine increases the feasibility of the air engine as one of the propulsion technologies in a city vehicle and even in the Compressed Air Energy Storage System (CAES).

Multi-perspective analysis of adiabatic compressed air energy storage system with cascaded packed bed latent heat storage under variable conditions

Adiabatic compressed air energy storage (A-CAES) with advanced thermal energy storage systems has enormous potential in applications. In particular, the extent of thermal energy utilization determines the comprehensive performance of an A-CAES system. In this paper, a cascaded latent heat packed bed storage system is used as a thermal energy storage under variable conditions of A-CAES. The transient thermal characteristic of the packed bed under variable conditions are further studied. Moreover, the key parameters that affect the thermal energy utilization of the system are also parametrically investigated. The results show that the proposed system has a roundtrip efficiency of 63.42 %, an exergy efficiency of 66.58 %, and a payback period of 4.63 years. The economic analysis shows that the proposed system is more advantageous in comparison with A-CAES with heat transfer oil as heat storage system.

Economic and environmental feasibility of coupled wind power-subsurface compressed CO2 energy storage system in China: An LCA approach

Energy storage is a crucial solution for addressing the uneven distribution of renewable energy sources, including wind, hydropower, and solar. A novel technology that combines energy storage with underground CO2 storage is introduced, building upon compressed CO2 energy storage (CCES), an advancement of compressed air energy storage systems. Through a case study and literature review, a life cycle assessment (LCA) is conducted to evaluate the economic and environmental performance of a wind power—CCES coupled system. The results indicate that the global warming potential (GWP) and acidification potential (AP) of the CCES system coupled with wind power are 19g CO2-eq/kWh and 0.13g SO2-eq/kWh, respectively, which are significantly lower than those of coal power and are lower than those of wind power alone. Currently, the power output of this energy storage system is limited. However, in an optimistic scenario, the cost to build and operate a wind power—CCES coupled system can be recovered within 16 years based on current electricity prices in China. Therefore, utilizing CO2 storage reservoirs to store excess electricity from wind power is a feasible approach in China's power system from both economic and environmental perspectives.

Multi-perspective analysis of adiabatic compressed air energy storage system with cascaded packed bed latent heat storage under variable conditions

Multi-perspective analysis of adiabatic compressed air energy storage system with cascaded packed bed latent heat storage under variable conditions

Performance analysis of a new compressed air energy storage system coupled with the municipal solid waste power generation systems

In order to improve the performance of the compressed air energy storage (CAES) system, a novel design is proposed: the CAES system is combined with the municipal solid waste power generation systems, including a waste incineration power generation system and a biogas power generation system. During the charging process, the feedwater and the condensate from the waste incineration power generation system are used to cool the compressed air. During the discharge process, the released compressed air is heated by the flue gas from the waste incineration power generation system, and the high-temperature compressed air works in the expander. Finally, the expanded air from the expander is fed into the combustor of the biogas power generation system, thus replacing the compressor of the gas cycle. Through the system integration, the efficiency of the CAES system is improved, and some equipment of the original CAES system is reduced. Based on the systems simulation, energy analysis, exergy analysis, economic analysis, and sensitivity analysis are performed. As a result, for the CAES subsystem, the round-trip efficiency, the energy storage density, and the exergy efficiency can reach 75.32 %, 14.10 MJ/m3, and 74.31 %. Besides, the dynamic payback period can reach 6.82 years.

Comparative Analysis of Diagonal and Centrifugal Compressors with Synergy Theory in Compressed Air Energy Storage System

Comparative Analysis of Diagonal and Centrifugal Compressors with Synergy Theory in Compressed Air Energy Storage System

Performance Analysis and Optimization of Compressed Air Energy Storage Integrated with Latent Thermal Energy Storage

Recovering compression waste heat using latent thermal energy storage (LTES) is a promising method to enhance the round-trip efficiency of compressed air energy storage (CAES) systems. In this study, a systematic thermodynamic model coupled with a concentric diffusion heat transfer model of the cylindrical packed-bed LTES is established for a CAES system, and the numerical simulation model is validated by experimental data in the reference. Based on the numerical model, the charging–discharging performance of LTES and CAES systems is evaluated under different layouts of phase change materials (PCMs) in LTES, and the optimal layout of PCM is specified as a three-stage layout, since the exergy efficiency of LTES and round-trip efficiency are improved by 8.2% and 6.9% compared with a one-stage layout. Then, the proportion of three PCMs is optimized using response surface methods. The optimization results indicate that the exergy efficiency of LTES and round-trip efficiency of the CAES system are expected to be 80.9% and 73.3% under the PCM proportion of 0.48:0.3:0.22 for three stages, which are 7.0% and 13.1% higher than the original three-stage PCMs with equal proportions.

Theoretical evaluation of a hybrid buoyancy-compressed air energy storage system

Energy storage plays a pivotal role in the emerging green economy. This study, for the first time, presents the theoretical evaluation of a buoyancy power generator combining with the compressed air energy storage (CAES-BPG) system. A theoretical model that satisfies conservation laws and does not involve any adjustable parameters is developed for the calculation of system efficiency and power generation capacity. To accurately predict drag acting on the buoy, the low Reynolds number κ-ω SST model with a locally refined mesh (y+~1) is applied to fully resolve the viscosity affected regions including the viscous sublayers, whilst the surrounding flow is modelled by LES. The refined mesh moves passively with the buoy and does not change, whilst mesh in other regions undergoes smoothing and remeshing to accommodate the buoy's motion. Correlations of drag coefficients are then developed as a function of buoy shape, Reynolds number, and vessel-to-buoy size ratio. The aerofoil shape yielded a substantially smaller drag coefficient compared to the square, hex, and bullet shapes. System efficiency showed independency on buoy volume and shell material but decreased as the water level in the vessel increased, reaching 64 % for a water level of 1.5 m. Similarly, as the water level increased, the system output power decreased. The output power increased as the buoy volume increased, reaching ~22 kW for a buoy volume of 2 m3 at a water level of 1.5 m. This CAES-BPG system is highly automatic and fully green, and can operate continuously once compressed air is connected, showing great potential for implementation as an energy storage / utilisation system of small to medium capacities.

Effect of geothermal heat transfer on performance of the adiabatic compressed air energy storage systems with the salt cavern gas storage

The temperature and pressure of compressed air influence the output performance of the adiabatic compressed air energy storage system with salt cavern gas storage. However, current studies often overlook the impact of geothermal heat transfer on system performance. In this paper, a mathematical model of the energy storage system with salt cavern gas storage is developed, considering the geothermal heat transfer in wellbore and salt carven. The model is used to illustrate the effects of geothermal heat transfer on the system performance through a sensitivity analysis of some key parameters. The results show that geothermal heat transfer will significantly reduce the gas and energy storage capacity, with a maximum reduction of 15.3 % and 11.1 % at a depth of 2000 m, respectively. Furthermore, this reduction would increase with the depth of the salt cavern. The geothermal energy reduces the round-trip efficiency from 68.7 % to 66.26 % and the energy storage density from 5.18 kWh·m−3 to 4.32 kWh·m−3. For common salt cavern gas storage at a depth of about 600 m ∼ 1200 m, the negative impacts of geothermal heat transfer on round-trip efficiency and energy storage density are less than 2.2 % and 0.5 kWh·m−3, respectively. Sensitivity analysis also demonstrates that the primary factors influencing the system’s performance are the thermal conductivity of the surrounding rock, the volume of the salt cavern, and the length of the wellbores. The secondary factors include the heat transfer coefficient on the inner wall of the salt cavern, the inner pipe radius, and the roughness of the inner pipe. Irrelevant factors include the thermal conductivity of the protective fluid and the thermal conductivity of the cement layer. The proposed comprehensive mathematical model of the system and simulation findings aid in forecasting the performance of storage systems and offer theoretical guidance for the design of large-scale compressed air energy storage systems.

Thermodynamic and economic analyses of a modified adiabatic compressed air energy storage system coupling with thermal power generation

With the proposal of "Carbon peaking and carbon neutrality", Adiabatic Compressed Air Energy Storage (A-CAES) has emerged as a significant component within China's energy storage infrastructure. But its thermodynamic efficiency and economical return need yet to be raised. The present paper proposed a modified system coupling with thermal power plant to utilize the excess compression heat. Utilizing advanced transient modeling software, an A-CAES plant is modeled and validated. The operation performance of the coupled system is compared with non-coupled system, which shows that the system efficiency is raised from 54.8 % to 76.7 % and the investment return rate is improved from 9.18 % to 10.43 %.

Aerodynamic performance and flow field losses analysis: A study on nozzle governing turbine with varied regulated nozzle stator installation angle

During the energy release process in compressed air energy storage (CAES) system, the air storage pressure gradually diminishes. To optimize turbine performance in this scenario, a judicious air distribution method becomes imperative. This study adopts single nozzle governing method and elucidates the variation in aerodynamic characteristics under rated output work conditions by manipulating regulated nozzle stator installation angle (RNSIA) and total inlet pressure under varying base pressure. When the RNSIA ranges from −10° to 4° under the base pressure of 10.0 MPa, the maximum specific work increment is 13.2 % and efficiency increment is 14.3 % compared with throttle governing. Meanwhile, the maximum specific work increment is 4.0 % and efficiency increment is 2.9 % compared with designed RNSIA. The proportion of throttle entropy increase to the system progressively rises from 5 % to 40 %, mirroring the trend in system entropy increase. To maintain output work requirements, it's advisable to appropriately decrease the RNSIA to boost inlet pressure of the regulated nozzle and mitigate throttling losses. Additionally, the reduction in the RNSIA within a certain range prolongs the duration of the energy release process in the CAES system, which effectively enhances the round-trip efficiency of the CAES system.

Performance analysis of a compressed air energy storage incorporated with a biomass power generation system

Compressed air energy storage technology is recognized as a promising method to consume renewable energy on a large scale and establish the safe and stable operation of the power grid. To improve the energy efficiency and economic performance of the compressed air energy storage system, this study proposes a design for integrating a compressed air energy storage system with a biomass power generation system. In the energy storage process, the feedwater from the biomass power generation system is used to cool the compressed air in the compressed air energy storage system. In the energy release process, the flue gas from the biomass power generation system is used to heat the compressed air. Besides, the compressed air from the compressed air energy storage system first works in the expander and then goes to the biomass power generation system for combustion. Based on the system simulation, the proposed system is assessed from the energy, exergy, economy, and environment perspectives. The results show that the round-trip efficiency and the energy storage density of the compressed air energy storage subsystem are 84.90 % and 15.91 MJ/m3, respectively. The exergy efficiency of the compressed air energy storage subsystem is 80.46 %, with the highest exergy loss in the throttle valves. The total investment of the compressed air energy storage subsystem is 256.45 k$, and the dynamic payback period and the net present value are 4.20 years and 340.48 k$. Besides, the proposed system’s CO2 emission is 258 kg/GWh. This study provides a new option for enhancing the performance of compressed air energy storage through the system integration.

Thermodynamic analysis of natural gas/hydrogen-fueled compressed air energy storage system

In this paper, a diabatic compressed air energy storage system fueled by a natural gas/hydrogen mixture that integrates heating and power generation is proposed. A comprehensive thermodynamic analysis has been conducted to identify the key factors influencing system performance and elucidate the detailed formation and distribution patterns of irreversible losses when utilizing a hydrogen-natural gas blend as fuel in the proposed system. The research results indicate that increasing the hydrogen blending ratio from 0.5 to 1 lead to greater enhancements in roundtrip efficiency (∼1.08% vs. ∼0.33%), exergy efficiency (∼3.88% vs. ∼1.15%), and energy density (∼1.24% vs. ∼0.42%) compared to an increase from 0 to 0.5. The combustor suffers the largest exergy destruction proportion, with a notable reduction in exergy destruction achieved through increased hydrogen blending. System performance benefits significantly from higher combustor outlet temperatures and expansion ratios at various hydrogen blending ratios. The rate of change in exergy efficiency (∼42.76% vs. ∼83.17%) and energy density (∼58.83%) demonstrates an inverse correlation with the varied parameters (1100–1500K, 4–8), except for the rate of change in energy density (∼6.76%), which displays a positive relationship with the combustor outlet temperature. Notably, a significant decrease in the rate of change in roundtrip efficiency (∼1.87% vs. ∼6.64%) is observed within a specific parameter range (1400–1500K, 5–6). Sensitivity analysis identifies the combustor outlet temperature as the most influential factor in enhancing system performance, consistently showing positive effects of the hydrogen blending ratio.

Status and Development Perspectives of the Compressed Air Energy Storage (CAES) Technologies—A Literature Review

The potential energy of compressed air represents a multi-application source of power. Historically employed to drive certain manufacturing or transportation systems, it became a source of vehicle propulsion in the late 19th century. During the second half of the 20th century, significant efforts were directed towards harnessing pressurized air for the storage of electrical energy. Today’s systems, which are based on storing the air at a high pressure, are usually recognized as compressed air energy storage (CAES) installations. This paper aims to provide an overview of different technologies that take advantage of the energy accumulated in the compressed air. Particular attention is paid to the CAES installations that are working as electrical energy storage systems (EESs). These systems, developed originally as large capacity (>100 MWe) and fuel-based installations, may soon become fully scalable, highly efficient, and fuel-free electrical energy storage systems. To present this opportunity, a thorough review encompassing previous and up-to-date advancements in their development was carried out. In particular, CAES concepts, such as diabatic (D-CAES), adiabatic (A-CAES), and isothermal (I-CAES), are described in detail. This review also provides the detailed characteristics of the crucial elements of these configurations, including compressors, expanders, air storage chambers, and thermal storage tanks. Knowledge of these components and their role allows us to understand the main challenges behind the further development of the mentioned CAES setups. Apart from the CAES systems that are designed as EES systems, this paper describes other prospective technologies that utilize the energy of pressurized air. Accordingly, compressed air cars and their key elements are explained in detail. Moreover, the technology renowned as wave-driven compressed air energy storage (W-CAES) is described as well, indicating that the utilization of pressurized air represents a viable option for converting ocean energy into electrical power.

A variable pressure water-sealed compressed air energy storage (CAES) tunnel excavated in the seabed: Concept and airtightness evaluation

For compressed air energy storage (CAES) caverns, the artificially excavated tunnel is flexible in site selection but high in sealing cost. A novel concept of building a water-sealed CAES tunnel in the seabed is proposed in this study, and the airtightness of the system is preliminarily evaluated. Based on the proposed variable pressure water-sealed CAES tunnel excavated in the seabed and combined with the actual operation of the system, a multifield and multiphase coupling calculation model for the airtightness calculation of water-sealed CAES tunnel under pressure changes was constructed, and the rationality of the model was confirmed by a case study. The airtightness analysis of the water-sealed CAES system is carried out. It is an effective method to excavate a tunnel in the seabed, and sealing the CAES system by utilizing the water head pressure in the pores of the rock mass and the low permeability of the rock mass. To satisfy the sealing requirements of the CAES system, the seawater depth of the tunnel should be deeper than 190 m if the gas pressure inside the tunnel is 4.5–10.0 MPa with the rock mass permeability of 1.0 × 10-16 m2 and the overlying rock thickness of 100 m, When the gas pressure inside the tunnel is 4.5–10.0 MPa, the overburden thickness is 100 m and the seawater depth is 50 m; the rock mass permeability should be less than 7.32 × 10-17 m2.

Solution for Post-Mining Sites: Thermo-Economic Analysis of a Large-Scale Integrated Energy Storage System

The intensive development of renewable energy sources and the decreasing efficiency of conventional energy sources are reducing the flexibility of the electric power system. It becomes necessary to develop energy storage systems that allow reducing the differences between generation and energy demand. This article presents a multivariant analysis of an adiabatic compressed air energy storage system. The system uses a post-mining shaft as a reservoir of compressed air and also as a location for the development of a heat storage tank. Consideration was given to the length of the discharge stage, which directly affects the capital expenditure and operating schedule of the system. The basis for the analyses was the in-house numerical model, which takes into account the variability of air parameters during system operation. The numerical model also includes calculations of Thermal Energy Storage’s transient performance. The energy efficiency of the system operating on a daily cycle varies from 67.9% to 70.3%. Various mechanisms for economic support of energy storage systems were analyzed. The levelized cost of storage varies, depending on the variant, from 75.86 EUR/MWh for the most favorable case to 223.24 EUR/MWh for the least favorable case.

Investigation and improvement of complex characteristics of packed bed thermal energy storage (PBTES) in adiabatic compressed air energy storage (A-CAES) systems

With the application of large-scale renewable energy, power grids have put forward explicit demands for energy storage. Among the various forms of energy storage systems, the adiabatic compressed air energy storage (A-CAES) system has received more attention due to its environmental friendliness and adaptability. As a key link in the regenerative A-CAES, thermal energy storage (TES) has an important impact on the efficiency of the system. Among various forms of TES, PBTES has better economy and adaptability. However, there is insufficient research on the impact of PBTES structure on A-CAES systems. Therefore, a dimensionless governing equation for the PBTES is proposed to study the depth effect of the PBTES structure. Through comparing with the pilot-scale and industrial-scale PBTES experimental data, the maximum error of the model is 2.3%, which proves that the model has good accuracy in the simulation of different scales of PBTES. The result of research shows that: the improved thickness of the structural layer is between 0.1 m and 0.15 m. The increase in the number of cycles of the A-CAES system results in a gradual increase in system efficiency. For the A-CAES system, the round-trip efficiency is improved by 4.1%, reaching 64%, with the improvement of the wall, volume ratio, and height-to-diameter ratio of PBTES.