Compressed Air Energy Storage Research Articles

Stability of lower limit of air pressure in abandoned coal mine roadways during long-term CAES

Power supply instability in the grid has been exacerbated by the rapid development of new energy generation methods. Notably, large-scale energy storage is the most practical solution to this problem. Meanwhile, in China, an effective method of reusing the increasing number of abandoned coal mines is urgently required. Accordingly, building compressed air energy storage (CAES) plants along the roadways of abandoned coal mines can serve as a viable energy storage method while repurposing these mines. This study examined the effect of the lower limit of air pressure (LLAP) on the stability of coal mine roadways in CAES applications by considering an ongoing pilot CAES coal mine in Chongqing, China. The findings indicate that the LLAP has a positive correlation with the roadway stability provided the frequency of air injection/extraction and upper limit of air pressure are constant. Over 10 years of CAES operation, a higher LLAP corresponds to less overall deformation of the roadway and top slab subsidence, and smaller plastic zone volume. Furthermore, the first main principle stress also decreases as the LLAP increases. According to the findings of this paper, the LLAP for the actual operation of CAES should be adjusted upwards as appropriate, which help to improve the geological stability of CAES roadways.

A directly charged thermal store for compressed air energy storage systems

This paper discusses the design of a heat storage unit with integrated heat exchangers (TES + HX), which is intended to work in a Compressed Air Energy Storage (CAES) system. The unit can be charged directly by the system's stream of pressurised air, eliminating the need for additional heat exchangers and reducing the number of heat transfer processes. Silica sand is used as the storage medium due to its high heat capacity, non-corrosivity and its ability to accommodate the thermal expansion of steel pipes.A medium-scale, medium-duration CAES system (250 kW/1MWh) is used as a case study. The heat storage subsystem comprises a packed-bed thermal store, three air-to-air heat exchangers and an ambient pressure air blower. Combined, this subsystem has an approximate cost of £147k and achieves an efficiency of ∼89 %, which translates into a levelized cost of ∼48.5 £/MWh. An integrated TES + HX unit can achieve a levelized cost of ∼35 £/MWh. The unit has an estimated cost of £38.5k and achieves an overall roundtrip exergy efficiency of ∼91.8 %. The integrated TES + HX unit not only offers a significant reduction in the capital cost of a CAES system and an efficiency improvement, but it also allows for a simpler overall architecture.

A Review of Modeling and Applications of Energy Storage Systems in Power Grids

As the penetration of variable renewable generation increases in power systems, issues, such as grid stiffness, larger frequency deviations, and grid stability, are becoming more relevant, particularly in view of 100% renewable energy networks, which is the future of smart grids. In this context, energy storage systems (ESSs) are proving to be indispensable for facilitating the integration of renewable energy sources (RESs), are being widely deployed in both microgrids and bulk power systems, and thus will be the hallmark of the clean electrical grids of the future. Hence, this article reviews several energy storage technologies that are rapidly evolving to address the RES integration challenge, particularly compressed air energy storage (CAES), flywheels, batteries, and thermal ESSs, and their modeling and applications in power grids. An overview of these ESSs is provided, focusing on new models and applications in microgrids and distribution and transmission grids for grid operation, markets, stability, and control.

Statistical evaluation of stability margin of a multi-stage compressor with geometric variability using adaptive polynomial chaos-Kriging model

Compressed air energy storage systems must promptly adapt to power network demand fluctuations, necessitating a high surge margin in the compression system to ensure safety. It is challenging to completely eliminate blade geometric variations caused by limited machining precision, the important effects of which should be considered during aerodynamic shape design and production inspection. The present paper explores the uncertainty impact of geometric deviations on the stability margin of a multi-stage axial compressor at a low rotational speed. Initially, an adaptive polynomial chaos expansion-based universal Kriging model is introduced, and its superior response performance in addressing high-dimensional uncertainty quantification problems is validated through rigorous analytical and engineering tests. Then, this model is used to statistically evaluate the stability margin improvement (SMI) of the compressor due to the Gaussian and realistic geometric variabilities separately. The results show that the mean and standard deviation of SMI are −0.11% and 0.5% under the Gaussian geometric variability, while those are 0.33% and 0.39% under the realistic variability. For both the geometric variabilities, the stagger angle and maximum thickness deviations of the first-stage rotor are the most influential parameters controlling the uncertainty variations in the stability margin. Finally, the underlying impact mechanism of the influential geometric deviations is investigated. The variation in the stability margin caused by the geometric deviations primarily results from the alteration of inlet incidences, affecting the size of the tip leakage vortex blockage and boundary-layer separation regions near the blade tip of the first-stage rotor.

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 : State-of-the-Art of Lined Rock Cavern

Compressed Air Energy Storage : State-of-the-Art of Lined Rock Cavern

Energy Storage Technologies and Business Model

Abstract: As the demand for renewable energy sources continues to grow, the importance of energy storage technologies and the development of sustainable business models for energy storage services have become paramount. This paper explores the various energy storage technologies available in the market and their unique characteristics, including battery storage systems, pumped hydro storage, compressed air energy storage, and more. Additionally, it investigates the evolving landscape of energy storage services and the potential business models that can be employed to maximize the utilization and economic viability of energy storage systems. The paper analyses the key factors influencing the deployment and adoption of energy storage technologies, such as cost, regulatory frameworks, grid integration, and the role of energy market stakeholders. Moreover, it delves into the emerging trends and 1the existing energy infrastructure. By examining the current state of energy storage technologies and providing insights into the development of sustainable business models, this paper aims to contribute to the understanding of the role of energy storage in enabling the transition towards a cleaner and more reliable energy future

Compressed air and hydrogen energy storage hybridized with solar energy to supply electricity and hot water for a residential settlement

In order to move toward net zero energy buildings, use of new and renewable energy resources parallel with development of high performance energy storage systems is necessary to maximize energy absorption and reduce energy losses with subsequent improvement in the energy performance of systems. In this research, two separate energy storage systems for supplying electricity and hot water for 500 residential buildings in Beijing have been designed and compared based on their performance. 1500 solar panels provide the required power for buildings. The first system is compressed air energy storage (CAES), while the second system is hydrogen energy storage (HES). Simulation has been done in TRNSYS and EES software. Energy and exergy analyses have been done for both systems. In case of the loss of hot water produced by the systems, the annual average energy efficiency of CAES and HES is about 44 % and 42 %, respectively. The energy efficiency of the first system decreases in the hot months of the year and reaches about 42 %, but the efficiency of the HES system is constant throughout the year. If the hot water produced by the systems is used for consumption in residential buildings, the energy efficiency of CAES and HES reaches 93 % and 64 %, respectively. The most exergy destruction in the CAES is related to combustion chambers (41 % of the total exergy destruction) and in the HES, it is related to electrolyzers (71 % of the total exergy destruction). The exergy efficiency of the first system is about 56 %, while for the second system this value is about 34 %.

Analysis of multi-cascade CCHP system with gas turbine bypass extraction air energy storage

The operational load of gas turbine can be regulated by using compressor bypass extraction. In this paper, a combined cooling, heating and power (CCHP) system integrating gas turbine cycle (GTC), compressed air energy storage (CAES), supercritical CO2 Brayton recompression cycle (SCRC), organic Rankine cycle (ORC) and absorption refrigeration cycle (ARC) is proposed. The use of CAES not only enables flexible recovery of waste heat and load demand regulation, but also enables effective storage and secondary use of bypass extracted air from the compressor. The temperature of the graded expanded air is reduced and returned to the gas turbine unit, improving its thermal performance. The exergy and economic analyses show that the GTC has the largest percentage of both exergy destruction and investment cost rates, over 60%. Under the proposed operation model, the payback period of a single gas turbine is 4.12 years, and the payback period of the proposed CCHP system is 2.44 years. Thermodynamic, economic and environmental evaluation models are established to analyze the system performance at different loads. At the lowest load operation, the energy efficiency of the CCHP system can reach 75.99%, the exergy efficiency is 45.89%, the unit energy cost is 0.032 $/kWh, and the greenhouse gas equivalent emission is 0.313 kgCO2e/kWh. Compared with the other four cascade waste heat recovery systems, the proposed CCHP system greatly improves the thermodynamic performance and reduces the unit energy cost rate and greenhouse gas equivalent emissions, especially under low load operation conditions.

Thermo-dynamic and economic analysis of a novel pumped hydro-compressed air energy storage system combined with compressed air energy storage system as a spray system

The efficiency of adiabatic compressed air energy storage technology is limited by the low utilization of thermal energy in the energy storage room. Therefore, a pumped hydro-compressed air energy storage system combined with a compressed air energy storage system as a spray system is introduced in the present research and analyzed by thermodynamic and economic analysis to verify the feasibility of system. For the performance analysis of the system, the main components and the whole system are precisely analyzed from the thermodynamic point. The results show that the round-trip efficiency and total exergy efficiency of the system are 52.45% and 77.8%. The system can significantly improve the air temperature in the air storage room, reduce the pressure energy loss of the system, and increase the energy storage capacity. Moreover, achieving high system round-trip efficiency is dependent on components of the system with high efficiencies. By optimization of the system operation mode, the round-trip efficiency of the system can reach 56%.

Effect of relative humidity on the nozzle performance in non-equilibrium condensing flows for improving the compressed air energy storage technology

Compressed air energy storage (CAES) is now becoming the focus of a lot of research as it offers broad application possibilities and enormous economic benefits in terms of environmental protection and life with low-carbon emissions. The compressor performance is closely related to energy storage efficiency in CAES. Considering the significant role of water components inside the flow of the compressor, the flow mechanism in transonic with non-equilibrium condensation should be explored in detail. First, a blend condensation model is presented with the effect of the entire Knudsen number range on droplet growth, to explore condensation flow characteristics more clearly. Moreover, the influence of relative humidity (RH) on the nucleation and droplet growth and condensation shock wave is analysed with the blend model. Finally, flow loss is calculated in the de Laval nozzle, and the direction to optimize the compressor efficiency is indicated by considering the RH conditions and wall curvature arcs. The contribution of these factors to the flow loss deserves careful consideration. The analysis conducted in the paper shows the effect of relative humidity on the nozzle, and the conclusions obtained provide meaningful reference for improving the performance of compressors used in the CAES process in the future.

Integrating compressed air energy storage with wind energy system – A review

- With an increasing capacity of wind energy globally, wind-driven Compressed Air Energy Storage (CAES) technology has gained significant momentum in recent years. However, unlike traditional CAES systems, a wind-driven CAES system operates with more frequent fluctuations due to the intermittent nature of wind power. Consequently, the design and operation of wind-driven CAES systems must address such a complex and dynamic behavior. Considering the growing interest in wind-driven CAES systems, a comprehensive and systematic review of the existing literature on their design and operational characteristics is appealing. Therefore, this study aims at filling this research gap by examining the existing literature on the configuration, sizing, and operation/scheduling of wind-driven CAES systems. This review also aims at highlighting the underlying assumptions and methodologies employed in previous studies on wind-driven CAES systems. Given the challenges faced by several CAES projects, which were discontinued due to geological and economic constraints, it is imperative to conduct comprehensive feasibility studies to support the development and implementation of wind-driven CAES systems. Additionally, there is a growing necessity to explore the feasibility of small-scale CAES systems, focusing on their potential to bolster energy security and resilience for small or remote communities in distributed energy systems. By examining the existing literature and highlighting the gaps in current research, a number of insights are provided serving as foundations for future investigations in this field.

Techno-Economic Analysis and Optimization of a Compressed-Air Energy Storage System Integrated with a Natural Gas Combined-Cycle Plant

To address the rising electricity demand and greenhouse gas concentration in the environment, considerable effort is being carried out across the globe on installing and operating renewable energy sources. However, the renewable energy production is affected by diurnal and seasonal variability. To ensure that the electric grid remains reliable and resilient even for the high penetration of renewables into the grid, various types of energy storage systems are being investigated. In this paper, a compressed-air energy storage (CAES) system integrated with a natural gas combined-cycle (NGCC) power plant is investigated where air is extracted from the gas turbine compressor or injected back into the gas turbine combustor when it is optimal to do so. First-principles dynamic models of the NGCC plant and CAES are developed along with the development of an economic model. The dynamic optimization of the integrated system is undertaken in the Python/Pyomo platform for maximizing the net present value (NPV). NPV optimization is undertaken for 14 regions/cases considering year-long locational marginal price (LMP) data with a 1 h interval. Design variables such as the storage capacity and storage pressure, as well as the operating variables such as the power plant load, air injection rate, and air extraction rate, are optimized. Results show that the integrated CAES system has a higher NPV than the NGCC-only system for all 14 regions, thus indicating the potential deployment of the integrated system under the assumption of the availability of caverns in close proximity to the NGCC plant. The levelized cost of storage is found to be in the range of 136–145 $/MWh. Roundtrip efficiency is found to be between 74.6–82.5%. A sensitivity study with respect to LMP shows that the LMP profile has a significant impact on the extent of air injection/extraction while capital expenditure reduction has a negligible effect.

Investigation of synergistic integration and optimization in combining compressed-air energy storage and a gas turbine

It is very important to guarantee performance synergy when combining two sub-systems. This study investigated combinations of compressed air energy storage systems (CAESs) and a gas turbine (GT) while considering various design factors. These factors included the CAES type, CAES capacity, and air injection flow rate, which were not considered in previous studies. The feasibility of various integration scenarios was evaluated, and the best scenario with the highest synergistic effect was obtained through an optimization method. When using a conventional CAES (C-CAES), the combined system was undesirable. When using an adiabatic CAES (A-CAES) or regenerative A-CAES, the combined system outperformed the standalone operation. When the flow ratio of the GT and A-CAES was 1:1.33, the percentage increases in net power and generated energy were 31.5 % and 12.6 %, respectively, and the roundtrip efficiency increased by 3.4 %p. When the flow ratio of GT and regenerative A-CAES was 1:0.88, the percentage increases in net power and generated energy were 31.3 % and 20.6 %, respectively, and the roundtrip efficiency was improved by 2.2 %p. This study provides the best synergistic integration between a CAES and GT for the first time by fully considering various scenarios, including thermal and mass integrations.

Advanced exergy and exergo-economic analyses of an advanced adiabatic compressed air energy storage system, part 2: Parametric study and optimization

In this study, parametric analysis and multi-objective optimization of the advanced adiabatic compressed air energy storage system (AA-CAES) were performed. Non-dominated Sorting Genetic Algorithm (NSGA-II) method was used in the multi-objective optimization study. In the optimization study, objective functions were determined in the conventional and advanced exergy/exergo-economic analyses concept. In the optimization study in the concept of advanced exergo-economic analyses, a new performance criterion that is not in the literature was determined and the results were confirmed by conventional exergo-economic analyses. In this study, the modified total unit product cost, which is given as the new performance criterion, is defined on the basis of avoidable feed exergy cost rate and avoidable investment cost rate. This shows the potential to be improved in the cost of the system and gives more detailed information than the total unit product cost in conventional exergo-economic analysis. As a result of the optimization study, the total unit product cost and the exergy efficiency of the system were found to be 162.9 $/day and 64.3%, respectively for the conventional exergy/exergo-economic analyses concept. For the advanced exergy/exergo-economic analyses concept, the modified total unit product cost and the modified exergy efficiency of system were found to be 103.5 $/day and 91.9 %. The exergy efficiency and the total unit product cost improved by 16.48 % and 3.55 %, respectively, with the optimization study according to the basic case of the overall system. With the parametric study, the increase in the efficiency of the wind turbine affected the exergy destruction rate more than the other system components. While the effect of the increase in the efficiency of the turbines on the exergy destruction cost rate of the system is greater than the other system components, the system component that most affects the cost rate of the system is the compressors.

Photothermal-assisted scheme design and thermodynamic analysis of advanced adiabatic compressed air energy storage system

The conventional photothermal-assisted scheme adopted by advanced adiabatic compressed air energy storage (AA-CAES) has equal stages of expanders and high-temperature reheaters, and is equipped with a regenerator to waste heat recovery, which is relatively complex and requires high solar heat supply and solar irradiance. In this paper, a novel photothermal-assisted AA-CAES (PT-AA-CAES) with a simpler structure and suitable for low solar irradiance is designed, which adopts 3-stage expansion and 2-stage high-temperature reheat. The thermodynamic model of PT-AA-CAES system is established, and a comprehensive evaluation coefficient combining exergy efficiency and energy storage density is proposed. The numerical results demonstrate that the compressor unit outlet pressure and expansion unit inlet pressure with the optimal comprehensive performance are 10 MPa and 4 MPa. Furthermore, when the solar irradiance is below 690 W/m2, 660 W/m2, and 600 W/m2, the output work, exergy efficiency, and energy storage density of the novel PT-AA-CAES system will surpass those of the conventional PT-AA-CAES system with the same solar heat consumption, and at a solar irradiance of 580 W/m2, the exceeded values are 44.3 kW h, 2.03%, and 0.15 kW h/m3, respectively. These conclusions can assist the AA-CAES system in the selection of unit pressures and photothermal-assisted scheme.

The investigation on a hot dry rock compressed air energy storage system

For the strict site requirement and the consumption of fossil fuel in compressed air energy storage system, the large-scale application of compressed air energy storage is limited. In this paper, a hot dry rock compressed air energy storage system is proposed, and the cracks of hot dry rock are used as the storage place of compressed air. Meanwhile, the thermodynamic model and wellbore model are constructed to evaluate the performance of proposed system. In the range of mass flow rate and recharge pressure of present work, the numerical results illustrate that the production temperature increases with the augment of the mass flow rate, but the increase of the recharge pressure has no obvious effect on the production temperature. Besides, the consumption of valley electricity increases with the augment of mass flow rate and the reduction of the recharge pressure. In addition, the round trip efficiency of the system fluctuates between 48.59%∼54.88%, which is much better than that of the traditional compressed air energy storage system (42%).

Off-design characteristics of a novel integrated system of coal-fired cogeneration unit and compressed air energy storage

The regulation range of heat-power ratio in conventional coal-fired cogeneration unit of heat and power (CHP) is limited, which makes the previous determination of electricity by heat can't meet both the heat and power load, and results in relatively low efficiency. In this paper, a new integrated system of coal-fired CHP unit with compressed air energy storage (CAES) system is studied, which can greatly adjust the heat-power ratio. During heat enhanced period (increasing heat-power ratio), CAES stores electric energy and makes the compression heat supply to the users. During power enhanced (reducing heat-power ratio), CAES discharges energy and absorbs CHP extraction heat to use in CAES expander. As the regulation of heat-power ratio is a process of variable working conditions, a detailed off-design model of the integrated system is established. The influence of the key parameters on the system off-design characteristics is revealed. The research shows that the CAES air flow rate has a great impact on the integrated system's efficiency and heat-power ratio, while the CAES chamber pressure has the least impact on the integrated system's efficiency. Under different CAES air flow rates and air chamber pressures, the fuel ratio corresponding to the highest exergy efficiency in the two periods is the same, which is about 0.92. Finally, a case study is made on the data of an industry park, which shows that the integrated system can well follow the heat and power demand with relatively high efficiency.

Review of Coupling Methods of Compressed Air Energy Storage Systems and Renewable Energy Resources

With the strong advancement of the global carbon reduction strategy and the rapid development of renewable energy, compressed air energy storage (CAES) technology has received more and more attention for its key role in large-scale renewable energy access. This paper summarizes the coupling systems of CAES and wind, solar, and biomass energies from the perspective of system topology, and points out the advantages and limitations of each system. It is shown that the coupling of wind energy and CAES is mainly combined in series and in parallel, and sometimes part of the wind power can be converted into thermal energy when coupled to CAES. The coupling between solar heat and CAES is an important form of coupling between solar energy and CAES. Solar-heat-coupled CAES mainly uses solar energy to heat expander inlet air. The coupling forms of solar energy and CAES are based on various CAES forms, various heat heating sequences, reheating, bottom cycle, and other factors. The combination of biomass and CAES is generally based on biomass gasification power generation technology. In the future, a wind–solar–CAES multiple coupling system is expected to become a promising large-scale form for the utilization of renewable energy, and this integrated system has great potential as a system configuration, but has some technical challenges.

A modified semi-weight function method for SIF calculation of arbitrary inclined interface crack with both single complex-root and double real-root singularities

An arbitrary inclined crack terminated at the interface usually has singularity of single complex-root or double real-root at crack tip. Currently, most methods of the stress intensity factor (SIF) calculation (e.g., Mellin transformation method, enrichment strategy method) only consider the single complex-root singularity, with difficulty in solving auxiliary functions. Although the scaled boundary method takes the double real-root singularity into account, it needs to set special finite elements at crack tip. In this study, based on the sub-matrix method and the reciprocal theorem of work, a modified semi-weight function method is proposed to calculate SIF of the arbitrary interface crack with consideration of both single complex-root and double real-root singularity, and also analyze the effect of bimaterial parameters (Gi), crack inclination angle (w) and relative length (a/L) on the SIFs. This modified method has the advantages of uniform auxiliary function (independent of crack size and external load) and simple finite element calculation (without special singularity element). Moreover, its validity is verified by good agreement of our calculation results with the available literature results and finite element results. The research results can provide a theoretical basis for anti-crack design of multi-layer caverns of the compressed air energy storage (CAES).