Large-scale Compressed Air Energy Storage Research Articles

Performance study of a compressed air energy storage system incorporating abandoned oil wells as air storage tank

With the rapid development of intermittent renewable energy, large-scale compressed air energy storage technology represented by Adiabatic Compressed Air Energy Storage (A-CAES) has attracted much attention. In order to simultaneously solve the problems of reuse of decommissioned oil wells and low efficiency of A-CAES system, a compressed air energy storage system incorporating abandoned oil wells as Air Storage Tank (AST) is proposed in this paper. The system performance of underground Oil Well CAES (OW-CAES), aboveground Steel Pipeline CAES (SP-CAES), and aboveground Storage Tank CAES (ST-CAES) is comparatively analyzed based on a thermodynamic model, focusing on the impact of heat transfer characteristic parameters of the AST wall on the system performance. The results show that recoverable heat and round-trip efficiency are significantly affected by the heat transfer characteristics of the AST wall. More recoverable heat and higher round-trip efficiency can be achieved by increasing the wall temperature and the surface area of the AST, respectively. The round-trip efficiency and energy storage density of the OW-CAES system are higher than those of the ST-CAES system, which are increased by 8.3 % and 18.45 % respectively. This study provides theoretical support for the feasibility of the OW-CAES system and has certain engineering guiding significance.

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.

A thermo-hydro-mechanical damage model for lined rock cavern for compressed air energy storage

Large-scale compressed air energy storage (CAES) technology is regarded as an effective way to alleviate the instability of electricity generated from renewable sources such as wind and solar power, which involves the expensive construction of underground caverns to store highly pressurized and high-temperature compressed air. This study documents mechanical behavior and gas permeability of granite under temperature-pressure synchronous cyclic loading, and the response of the surrounding rock to Thermo-Hydro-Mechanical-Damage (THMD) evolution. Firstly, physical experiments were conducted to examine mechanical property and gas permeability evolutions of granite due to temperature-pressure synchronous cyclic loading. Based on these experiments, equations describing the damage evolution of granite were deduced. Subsequently, using these equations in combination with a thermo-hydro-mechanical coupled model of porous media with two-phase fluid flow, a sophisticated computational routine for the thermo-hydro-mechanical-damage analysis of underground gas storage caverns was developed. Lastly, numerical simulations were conducted to study heat transfer, two-phase seepage, and mechanical response of a CAES cavern under operating conditions. Under low to medium pressure and high-temperature synchronous cyclic loading, granite exhibited a significant variation in elastic modulus and compressive strength. Also, its permeability showed a substantial increase due to damage evolution. After two months of operation, prominent heat transfer was observed in the surrounding rock, particularly in the region extending to approximately 10 m from the inner surface of the cavern, exceeding the range of gas leakage diffusion within the cavern. The plastic zone of surrounding rock is distributed above the cavern's roof and below its bottom. Moreover, areas with higher damage are concentrated in the surrounding rock near the cavern's side walls. These findings contributed to our understanding of the behavior of granite in the context of CAES technology and provided valuable insights for the design and operation of gas storage caverns. The development of the THMD model offered a valuable tool for investigating stress and deformation characteristics of the lining and surrounding rock in CAES plants.

Two-phase Fluid Solid Coupling Modeling: Theory, Numerical Model, and Application

Underground compressed air energy storage (CAES) is seen as an important and promising way for balancing electrical power system. Many large-scale CAES projects (≥300 MW) are being planned in China, some of which have already been permitted for construction. Despite the benefits from CAES, some challenges arise in area of construction technology, operation system, maintenance and monitoring methods. One of the challenges lies in the evaluation of air leakage effect on flow and stress field around the underground cavern. Therefore, considering the actual physical field characteristics, the mathematical formula of mass conservation equations for air and water in porous media, as well as equilibrium equations for solid mechanics are established first and then coupled together for numerical solutions. The constitutive models for solid and porous fluid adopt classical elastic and Darcy’s law respectively, while the air-water interaction adopts classical van-Genuchten model and contributes to solid mechanics by pore pressure. Numerical implementations are based on secondary development to COMSOL software. Then interpretations to simulation results and the comparison with results not taking damage effect into account are made.

Expansion cooling prospects for large scale applications

Air conditioning in general and cooling in particular are the biggest energy sinks among all electricity consumers. Mitigating energy needs of this sector by active or passive means is a necessity. This paper offers a comprehensive review of various cooling technologies for large scale applications and compares them in terms of economy, environmental footprint and most importantly, energy requirements. There is a main focus on the potential of using expansion cooling, which is defined in conjunction with cooling effects generated during the expansion process of a gas. The interest in such cooling technology stems from the double benefit of utilizing a large-scale compressed air energy storage (CAES) system that can also provide cooling via the expansion of air. This consequently manifests in reducing the electrical demand required for cooling applications. Such a concept is beneficial for hot climates, where most of the electrical demand is reserved for offsetting the cooling load.

Large-scale CAES in bedded rock salt: A case study in Jiangsu Province, China

To efficiently utilize renewable energy sources primarily consisting of wind and solar power, large-scale compressed air energy storage (CAES) can be implemented using underground salt caverns. In this paper, the abundant wind and solar energy resources and the geological conditions of the three major salt mines in Jiangsu Province are introduced. A geomechanical model is established based on the Huai'an rock salt formation. The simulation results show that as the internal air pressure (IAP) increases, the safety factor increases, and the displacement, plastic zone, volume shrinkage, and equivalent strain decrease. Based on the above results, the minimum IAPs of caverns AN 13 and AN 21 are recommended to be 10–12 MPa. According to estimates, to store 15% of wind and solar power in Jiangsu Province through CAES by 2050, a 9894.0 × 104 m3 salt cavern volume is needed, of which at least 77.8 million m3 can be provided by salt mining enterprises. The cost of reconstructing an underground salt cavern is 12.1 billion yuan, while the investment in surface equipment is 746.7 billion yuan. We provide an economical and feasible solution for achieving carbon neutrality in Jiangsu Province in this study.

Compressed air energy storage (CAES): current status, geomechanical aspects and future opportunities

Abstract A compressed air energy storage (CAES) facility provides value by supporting the reliability of the energy grid through its ability to repeatedly store and dispatch energy on demand. Two main advantages of CAES are its ability to provide grid-scale energy storage and its utilization of compressed air, which yields a low environmental burden, being neither toxic nor flammable. The focus of this review paper is to deliver a general overview of current CAES technology (diabatic, adiabatic and isothermal CAES), storage requirements, site selection and design constraints. We discuss underground storage options suitable for CAES, including submerged bladders, underground mines, salt caverns, porous aquifers, depleted reservoirs, cased wellbores and surface pressure vessels. A geomechanical perspective is provided regarding the pressure limits for these options. The impacts of cyclic injection and withdrawal of compressed air, and the importance of caprock assessments with porous rock CAES, are also discussed. In addition, we provide an overview of the large-scale CAES facilities that are currently active or under development and a cost comparison of the diabatic, adiabatic and isothermal CAES options. Lastly, we outline major challenges and future opportunities for CAES and the top priorities for research, industry and stakeholders.

Energy distributing and thermodynamic characteristics of a coupling near-isothermal compressed air energy storage system

Intermittent renewable energy generation systems bring serious adverse impacts to the stable operation of the grid. In this regard, large-scale compressed air energy storage (CAES) systems with the potential to serve as long-term could be a solution for their optimal utilization. However, in a conventional CAES, most of the electricity is transformed into heat which passed into heat exchange mediums leads to serious heat transfer losses. In this study, a novel CAES system employing a Kalina cycle to effectively utilize the pre-compression heat in a near-isothermal compressed air process, is proposed and its holistic dynamic model is developed and presented for a deeper understanding of performance. The results showed that a near-isothermal compression undertakes the responsibilities of storing pressure potential energy, and the adiabatic pre-compression process helping in raising the inlet pressure of the liquid piston is primarily for storing thermal energy. In addition, the Kalina cycle working in the adiabatic pre-compression process achieves a 2.7 % improvement in the electrical efficiency. The thermal energy storage temperature was highlighted as the key factor in the energy allocation among the Kalina cycle, the thermal energy storage component, and the energy releasing sub-system in the proposed system. Through a systematic analysis of the proposed system performance, the highest electrical efficiency attained was 65.1 % with a 353 K storage temperature.

Modality analysis and algorithm design of stator short-circuit fault set for large compressed air energy storage generators

Using salt caverns and caves to build compressed air energy storage power stations is an important development direction in the field of large-scale energy storage. With the continuous maturity of technology, compressed air energy storage generators have gradually developed into large-scale units with a single-unit capacity of 300 MW. Due to the increase of single-unit capacity, the internal short-circuit fault of the stator will cause very serious losses. In addition, the compressed air energy storage generator has complex operating conditions and is more prone to various internal short-circuit faults. In order to effectively ensure its safe and reliable operation, it is particularly necessary to study the effective main protection configuration scheme. The optimal design of the main protection configuration scheme is based on the analysis of the possible internal short-circuit faults of the generator. At present, the stator windings of large-scale compressed air energy storage generators generally adopt double-layer wave winding or double-layer tap winding structures. For these two winding structures, this paper analyzes in detail the characteristics of all fault modalities that may occur inside the large-capacity compressed air energy storage generator and designs a general algorithm that can form their respective fault sets. Finally, the application of the algorithm in the analysis of the stator fault modality in a compressed air energy storage power station is introduced.

Overview of current compressed air energy storage projects and analysis of the potential underground storage capacity in India and the UK

Compressed air energy storage (CAES) is an established and evolving technology for providing large-scale, long-term electricity storage that can aid electrical power systems achieve the goal of decarbonisation. CAES facilities often utilise large underground storage caverns to ensure high capacity systems. This results in the need of locations with suitable geological features to develop a CAES plant. This paper examines recent and ongoing large-scale CAES projects and presents candidate methods of storing high pressure air using underground features. An assessment of the overall potential for CAES in India is presented by examining its geological features and locations with the greatest potential for CAES plants are determined. This is combined with an analysis of the renewable electricity generation potential in India to identify candidate areas for renewable generation and CAES integrated systems. Up to 1.05% of Indian land area is deemed suitable for CAES plant development and if fully utilised would be sufficient to meet the energy storage needs of India, however, practically a very small fraction of the total suitable land that could be developed so other competing energy storage technologies should be considered. Conversely, the UK possesses a very good potential for CAES, enough to greatly exceed necessary energy storage, owing to the abundance of salt beds not present in India. For CAES to garner serious consideration in India, aquifer storage based CAES needs to be demonstrated.

Day-Ahead Market Participation of an Active Distribution Network Equipped With Small-Scale CAES Systems

Large-scale compressed air energy storage (CAES) is conventionally used in power systems. However, application of CAESs at the distribution level is limited because of differences in design and efficiency. On the other hand, application of electrical batteries suited for distribution networks (DNs) faces also challenges from high investment cost and significant degradation. In this regard, this paper presents the participation of an active distribution system equipped with a small-scale CAES (SCAES) in the day-ahead wholesale market. To make CAES applicable to DNs, thermal-electrical setting design of the SCAES coupled with a packed-bed heat exchanger is adopted in the operation of the grid, where SCAES performs as an energy storage for DNs to surpass existing deficiencies of battery banks. The electrical/thermal conversion rate has been modeled for the SCAES operation. Moreover, the operation strategy of the SCAES is optimally coordinated with an electric vehicle charging station (EVCS) as an alternative energy storage technology in deregulated DNs. To make EVCS simulation more realistic, Gaussian Copula probability distribution function is used to model the behavior of the EVCS. The results obtained from different case studies confirm the value of SCAES as a reliable energy storage technology for DNs.

Experimental and Numerical Investigations of Small-Scale Lined Rock Cavern at Shallow Depth for Compressed Air Energy Storage

Lined rock cavern at shallow depth is identified as a promising alternative and cost-effective solution for air storage of large-scale compressed air energy storage (CAES) plant. To better understand the thermodynamic process of the compressed air in the underground cavern and the response of the surrounding rock during air charging and discharging phases, a small-scale pilot cavern with concrete liner and fiber-reinforced plastic (FRP) sealing layer was constructed in China. The test program includes one trial charging test, eight short-term charging tests, and one long-term charging test. Numerical simulations were carried out along with the experiments. The results show that the air pressure in the pilot cavern increased/decreased approximately linearly during the charging/discharging phase when the air was injected/released at a constant mass rate. The heat exchanging system could maintain the temperature of the compressed air in the cavern in a designed range. Excellent sealing performance of the FRP was validated in the test, with only 3.2% air mass leaked during the high-pressure storage phase. The influence of the high air pressure on the surrounding rock was limited and only elastic deformation was observed in all the tests. Good quality of rock mass could guarantee the structural safety of the underground cavern under high inner pressure. Generally, there are reasonable agreements between the numerical simulation and the results of the experiment. The study confirms the feasibility of CAES in lined rock caverns at shallow depth.

Experimental study of pipe-pile-based micro-scale compressed air energy storage (PPMS-CAES) for a building

Compressed air energy storage (CAES) technology has been re-emerging as one of the promising options to address the challenge coming from the intermittency of renewable energy resources. Unlike the large-scale CAES, which is limited by the geologic location, small-and micro-scale CAES that uses a human-made pressure vessel is adaptable for both grid-connected and standalone distributed units equipped with the energy generation capacity. The research team recently suggested a new concept of pipe-pile-based micro-scale CAES (PPMS-CAES) that uses pipe-pile foundations of a building as compressed air storage vessels. To ascertain the mechanical feasibility of the new concept, we conducted lab-scale pile loading tests with a model test pile in both a loose and dense soil chamber that emulates an actual closed-ended pipe pile. The test pile was subjected to a repeated cycle of compressed air charge (to Pmax=10 MPa) and discharge (to Pmin=0.1 MPa) during the experimental study. The displacement at the top of the test pile, with and without a structural loading, in loose and dense sand, was closely monitored during the repetitive air pressurization-and-depressurization. It was observed that the vertical displacement at the pile head under different conditions was accumulated during the extended cycle of air charge and discharge, but the rate of displacement gradually attenuates during the cycle. And, the presence of structural load and density of soil affected the magnitude of the accumulated vertical displacement. From the analysis, it can be concluded that the concept of PPMS-CAES is not likely to compromise the mechanical integrity of pipe piles while showing a promising capacity for energy storage.

Design of a Centrifugal Compressor with Low Solidity Vaned Diffuser (LSVD) for Large-Scale Compressed Air Energy Storage (CAES)

Compressed Air Energy Storage (CAES) has tremendous promotional value in the intermittent renewable energy supply systems. CAES has special requirements for compressor (e.g. heavy load, high pressure ratio, wide range). With advantages of higher efficiency and wider operation range, IGC (Integrally Geared Compressors) is selected to fulfill the special requirements of the large-scale CAES. To get a better aerodynamic performance, in this paper, based on the analysis of internal flow of centrifugal compressor, a multi-objective one-dimensional optimization design program was put forward combined with modified Two-Zone model and a low solidity vaned diffuser (LSVD) design method. Then, a centrifugal compressor aerodynamic component optimization design system was established with the three-dimensional blade optimization design method based on neural network and genetic optimization algorithm. Then a validation was done by redesigning the Krain-Impeller to get better performance. Finally, the aerodynamic design of the first stage of IGC was completed. The CFD calculation results indicated that the total-to-total pressure ratio of the first stage was 2.51 and the polytropic efficiency was 91.0% at the design point. What’s more, an operation margin and surge margin of the compressor was about 26.5% and 16.4% respectively.

Research on optimal self‐scheduling horizon for the wind power and large‐scale CAES combined system

The self-scheduling horizon is an important schedule parameter in the self-scheduling problem. A more reasonable self-scheduling horizon can lead to higher benefits of the wind farm (WF) and large-scale compressed air energy storage (CAES) combined system. However, very few studies have been reported about the optimisation of self-scheduling horizon for a WF paired with a CAES plant. In this study, a rolling day-ahead self-scheduling framework for a WF and CAES combined system is first proposed. After that, the self-scheduling horizon optimisation model is developed in the formulation of a bilayer stochastic chance-constrained optimisation problem. The proposed model is converted into its equivalent deterministic linear formulation and then is solved. Based on the developed model, the impacts of self-scheduling horizon on the profit of the combined system are analysed. Numerical simulation results indicate that the profit of the combined system increases after using the optimal self-scheduling horizon, and the profit increment is more obvious with the increase of the CAES's energy storage capacity.

Thermodynamic analysis and optimization of liquefied air energy storage system

A large proportion of new energy sources, such as wind and solar energy, are unable to be directly connected to the grid owing to their instability characteristics. To solve this problem, power storage technologies, such as large-scale compressed air energy storage (CAES) technology, have become more important and are playing an increasingly important role. Liquefied air energy storage (LAES) technology is a new type of CAES technology with high power storage density, which can solve the problem of large air storage devices that other CAES systems need to configure. In this study, thermodynamic models of the main components of an LAES system are first established, and the main components of the system are analyzed and optimized. On this basis, the thermodynamic model of an LAES system is established, and the thermodynamic analysis of the system is carried out by means of exergy analysis. The analyzed results show that an LAES system configured with four-stage compression and four-stage expansion has good comprehensive thermodynamic performance. The storage pressure and release pressure of the system are determined to be 15 and 7.1 MPa, respectively, and the air temperature before the pressure-reducing valve of liquefaction is 93 K. Increasing the adiabatic efficiency of main components of the LAES system can reduce their exergy loss, thereby reducing the exergy loss of the whole system and improving its energy storage efficiency.

Thermodynamic analysis of cavern and throttle valve in large-scale compressed air energy storage system

The compressed air energy storage system has the potential to enable large-scale implementation of renewable energies. However, the exergy destruction in the throttle valve and cavern is an important factor that affects the overall performance of the system. The conventional diabatic compressed air energy storage system consisted of compressors, heat exchangers, cavern, combustion chambers and turbines was studied and parameters of the Huntorf plant were adopted for calculation. Mathematical models of the components in the compressed air energy storage system were developed based on the equation of state for the real gas and the thermodynamic laws. The models are derived on the basis of assumptions that the inlet and outlet air flow rates of the cavern are negligible and that the system is operated in steady state. The test data of the Huntorf plant during the initial test was used to validate the models. Sensitivity analyses were conducted to identify the domain parameters that affect the exergy destruction in the cavern and throttle valve. The results indicated that 18.85% of the stored exergy was lost in the cavern and throttle valve during a complete cycle. The exergy destruction in the cavern was higher than that in the throttle valve, and the exergy destruction coefficients in the cavern and throttle varied with opposite tendencies when the parameters were changed. The heat transfer coefficient, injected air temperature, and initial temperature of the cavern were found to highly affect the total exergy destruction coefficient. Higher injected air temperature and lower cavern initial temperature reduces the total exergy destruction in the cavern and throttle valve.

Determining constraints imposed by salt fabrics on the morphology of solution-mined energy storage cavities, through dissolution experiments using brine and seawater in halite

Large-scale compressed air energy storage facilities offer one solution to the UK9s energy demands, using solution-mined caverns in salt lithologies. For optimum gas storage efficiency, cavern geometry should ideally be smooth: spherical to cylindrical with a circular cross-section. However, such caverns are often irregular with marked asymmetry or ellipticity, and although the reasons for non-circular cross-sections developing during solution mining in some caverns can be related to, for example, the presence of interbedded lithologies, in other instances they are not fully understood. Cavities from dissolution experiments using five main end-member salt facies fabrics from the Triassic Preesall and Northwich Halite formations have been assessed to determine factors affecting cavity geometry, formation and variability in dissolution behaviour. Identical sets of experiments were performed on each fabric type, using two solution concentration strengths: brine and synthetic seawater. Comparison of experimental results using a combination of analytical and imaging techniques shows the extent to which the salt fabric and enhancement of features within the salt influence the resulting dissolution cavity. Observations show a visible increase in micropores within the adjacent halite matrix following dissolution. Smaller-scale features provide further insights into the dissolution processes, and salt fabric behaviour under different dissolution conditions. Supplementary material: A detailed description of methods is available at https://doi.org/10.6084/m9.figshare.c.4282454

Exergy storage of compressed air in cavern and cavern volume estimation of the large-scale compressed air energy storage system

Accurate estimation of the energy storage capacity of a cavern with a defined storage volume and type is the very first step in planning and engineering a Compressed Air Energy Storage (CAES) plant. The challenges in obtaining a reliable estimation arise in the complexity associated with the thermodynamics of the internal air compression and expansion processes and the coupled heat transfer with surroundings. This study developed the methodology for estimating the exergy storage capacity with a known cavern volume, as well as the cavern volume required for a defined exergy storage capacity with different operation and heat transfer conditions.The work started by developing the mathematical models of the thermodynamic responses of air in a cavern subject to cavern operation in isochoric uncompensated or isobaric compensated modes, and heat transfer conditions including isothermal, convective heat transfer (CHT) and adiabatic wall conditions. The simulated transient air pressure and temperature were verified with the operational data of the Huntorf CAES plant. The study of the Huntorf CAES cavern confirmed the importance of the heat transfer influence on the energy conversion performance. The increase of mass storage due to the reduced temperature variation leads to an enhanced total exergy storage of the cavern. According to our simulations, within the operating range of the Huntorf plant, 34.77% more exergy after the charging and 37.98% more exergy after throttling can be stored in the cavern with isothermal wall condition than those in the cavern with adiabatic wall condition. Also, the nearly isothermal behaviour and high operating pressure in the compensated isobaric cavern resulted in the high effectiveness of exergy storage per unit cavern volume. The required cavern volume of the assumed isobaric cavern operation can be reduced to only 35% of the current cavern volume at the Huntorf plant. Finally, cavern volumes for an operational gas storage facility were used to demonstrate the methodology in estimating the exergy storage capacity, which provided an initial assessment of the storage capacity in the UK.

Pressure response of large-scale compressed air energy storage in porous formations

Large-scale compressed air energy storage (CAES) in porous formations can contribute to compensate the strong daily fluctuations in renewable energy production. This work presents a hypothetical CAES scenario using a representative geological anticlinal structure in Northern Germany and performs numerical simulations to estimate pressure response in the storage formation. The results show that the induced pressure changes laterally throughout the storage formation are due to initial fill of the air storage. Because of high air compressibility, the pressure fluctuations caused by daily cyclic operation can only be observed in the gas phase which reaches a distance of roughly 500 m.