Development and technology status of energy storage in depleted gas reservoirs

Utilizing energy storage in depleted oil and gas reservoirs can improve productivity while reducing power costs and is one of the best ways to achieve synergistic development of"Carbon Peak–Carbon Neutral"and"Underground Resource Utiliza-tion".Starting from the development of Compressed Air Energy Storage(CAES)technology,the site selection of CAES in depleted gas and oil reservoirs,the evolution mechanism of reservoir dynamic sealing,and the high-flow CAES and injection technology are summarized.It focuses on analyzing the characteristics,key equipment,reservoir construction,application scenarios and cost analysis of CAES projects,and sorting out the technical key points and existing difficulties.The devel-opment trend of CAES technology is proposed,and the future development path is scrutinized to provide reference for the research of CAES projects in depleted oil and gas reservoirs.

Comparative analysis of thermodynamic and mechanical responses between underground hydrogen storage and compressed air energy storage in lined rock caverns

Underground hydrogen storage(UHS)and compressed air energy storage(CAES)are two viable largescale energy storage technologies for mitigating the intermittency of wind and solar power.Therefore,it is meaningful to compare the properties of hydrogen and air with typical thermodynamic storage processes.This study employs a multi-physical coupling model to compare the operations of CAES and UHS,integrating gas thermodynamics within caverns,thermal conduction,and mechanical deformation around rock caverns.Gas thermodynamic responses are validated using additional simulations and the field test data.Temperature and pressure variations of air and hydrogen within rock caverns exhibit similarities under both adiabatic and diabatic simulation modes.Hydrogen reaches higher temperature and pressure following gas charging stage compared to air,and the ideal gas assumption may lead to overestimation of gas temperature and pressure.Unlike steel lining of CAES,the sealing layer(fibre-reinforced plastic FRP)in UHS is prone to deformation but can effectively mitigates stress in the sealing layer.In CAES,the first principal stress on the surface of the sealing layer and concrete lining is tensile stress,whereas UHS exhibits compressive stress in the same areas.Our present research can provide references for the selection of energy storage methods.

A novel nano-grade organosilicon polymer:Improving airtightness of compressed air energy storage in hard rock formations

Enhancing cavern sealing is crucial for improving the efficiency of compressed air energy storage(CAES)in hard rock formations.This study introduced a novel approach using a nano-grade organosilicon polymer(NOSP)as a sealant,coupled with an air seepage evaluation model that incorporates Knudsen diffusion.Moreover,the initial coating application methods were outlined,and the advantages of using NOSP compared to other sealing materials,particularly regarding cost and construction techniques,were also examined and discussed.Experimental results indicated a significant reduction in permeability of rock specimens coated with a 7–10μm thick NOSP layer.Specifically,under a 0.5 MPa pulse pressure,the permeability decreased to less than 1 n D,and under a 4 MPa pulse pressure,it ranged between4.5×10^(-6)–5.5×10^(-6)m D,marking a 75%–80%decrease in granite permeability.The sealing efficacy of NOSP surpasses concrete and is comparable to rubber materials.The optimal viscosity for application lies between 95 and 105 KU,and the coating thickness should ideally range from 7 to 10μm,applied to substrates with less than 3%porosity.This study provides new insights into air transport and sealing mechanisms at the pore level,proposing NOSP as a cost-effective and simplified solution for CAES applications.

Air tightness of compressed air storage energy caverns with polymer sealing layer subjected to various air pressures

During the operation of compressed air storage energy system,the rapid change of air pressure in a cavern will cause drastic changes in air density and permeability coefficient of sealing layer.To calculate and properly evaluate air tightness of polymer sealing caverns,the air-pressure-related air density and permeability must be considered.In this context,the high-pressure air penetration in the polymer sealing layer is studied in consideration of thermodynamic change of the cavern structure during the system operation.The air tightness model of compressed air storage energy caverns is then established.In the model,the permeability coefficient and air density of sealing layer vary with air pressure,and the effectiveness of the model is verified by field data in two test caverns.Finally,a compressed air storage energy cavern is taken as an example to understand the air tightness.The air leakage rate in the caverns is larger than that using air-pressure-independent permeability coefficient and air density,which is constant and small in the previous leakage rate calculation.Under the operating pressure of 4.5-10 MPa,the daily air leakage in the compressed air storage energy cavern of Yungang Mine with high polymer butyl rubber as the sealing material is 0.62%,which can meet the sealing requirements of compressed air storage energy caverns.The air tightness of the polymer sealing cavern is mainly affected by the cavern operating pressure,injected air temperature,cavern radius,and sealing layer thickness.The cavern air leakage rate will be decreased to reduce the cavern operating pressure the injection air temperature,or the cavern radius and sealing layer thickness will be increased.

Design and Development of Wind-Solar Hybrid Power System with Compressed Air Energy Storage for Voltage and Frequency Regulations

The intermittent nature of wind and solar photovoltaic energy systems leads to the fluctuation of power generated due to the fact that the power output is highly dependent upon local weather conditions, which results to the load shading issue that led to the voltage and frequency instability. In additional to that, the high proportions of erratic renewable energy sources can lead to erratic frequency changes which affect the grid stability. In order to reduce this effect, the energy storage system is commonly used in most wind-solar energy systems to balance the voltage and frequency instability during load variations. One of the innovative energy storage systems is the compressed air energy storage system (CAES) for wind and solar hybrid energy system and this technology is the key focus in this research study. The aim of this research was to examine the system configuration of the CAES system through modelling and experimental approach with PID controller design for regulating the voltage and frequency under different load conditions. The essential elements and the entire system have been presented in this work as thorough modelling in the MATLAB/Simulink environment for different load conditions. The developed model was tested through an experimental workbench using the developed prototype of the compressed air storage in the Siemens Lab at DeKUT and explored the consequence of the working parameters on the system proficiency and the model accuracy. The performance of the system for the developed prototype of CAES system was validated using results from an experimental workbench with MATLAB/Simulink R2022b simulation. The modeling and experimental results, shows that the frequency fluctuation and voltage drop of the developed CAES system during load variations was governed by the I/P converter using a PID_Compact controller programed in the TIA Portal V17 software and downloaded into PLC S7 1200. Based on these results, the model can be applied as a basis for the performance assessment of the compressed air energy storage system so as to be included in current technology of wind and solar hybrid energy systems.

先进压缩空气储能系统的基础研究与应用进展

Decarbonization of the electric power sector is essential for sustainable development.Low-carbon generation technologies,such as solar and wind energy,can replace the CO_(2)-emitting energy sources(coal and natural gas plants).As a sustainable engineering practice,long-duration energy storage technologies must be employed to manage imbalances in the variable renewable energy supply and electricity demand.Compressed air energy storage(CAES)is an effective solution for balancing this mismatch and therefore is suitable for use in future electrical systems to achieve a high penetration of renewable energy generation.This study introduces recent progress in CAES,mainly advanced CAES,which is a clean energy technology that eliminates the use of fossil fuels,compared with two commercial CAES plants at Huntorf and McIntosh which are conventional ones utilizing fossil fuels.Advanced CAES include adiabatic CAES,isothermal CAES,liquid air energy storage,supercritical CAES,underwater CAES,and CAES coupled with other technologies.The principles and configurations of these advanced CAES technologies are briefly discussed and a comprehensive review of the state-of-the-art technologies is presented,including theoretical studies,experiments,demonstrations,and applications.The comparison and discussion of these CAES technologies are summarized with a focus on technical maturity,power sizing,storage capacity,operation pressure,round-trip efficiency,efficiency of the components,operation duration,and investment cost.Potential application trends were compiled.This paper presents a comprehensive reference for developing novel CAES systems and makes recommendations for future research and development to facilitate their application in several areas,ranging from fundamentals to applications.

不同工况和应用场景下CAES-CFP三联产系统特性分析

To meet the goal of worldwide decarbonization,the transformation process toward clean and green energy structures has accelerated.In this context,coal-fired power plant(CFPP)and large-scale energy storage represented by compressed air energy storage(CAES)technology,are tasked with increasing renewable resource accommodation and maintaining the power system security.To achieve this,this paper proposes the concept of a CFPP-CAES combined cycle and a trigenerative system based on that.Considering the working conditions of the CFPP,thermal characteristics of three typical operation modes were studied and some general regularities were identified.The results of various potential integration schemes discussion indicated that extracting water from low-temperature points in the feedwater system to cool pressurized air and simultaneously increase the backwater temperature is beneficial for improving performance.In addition,preheating the pressurized air before the air expanders via lowgrade water in the feedwater system as much as possible and reducing extracted steam contribute to increasing the efficiency.With the optimal integration scheme,2.85 tonnes of coal can be saved per cycle and the round-trip efficiency can be increased by 2.24%.Through the cogeneration of heat and power,the system efficiency can reach 77.5%.In addition,the contribution degree of the three compression heat utilization methods to the performance improvement ranked from high to low,is preheating the feedwater before the boiler,supplying heat,and flowing into the CFPP feedwater system.In the cooling energy generation mode,the system efficiency can be increased to over 69%.Regardless of the operation mode,the benefit produced by integration is further enhanced when the CFPP operates at higher operating conditions because the coupling points parameters are changed.In addition,the dynamic payback period can be shortened by 11.33 years and the internal rate of return increases by 5.20%under a typical application scenario.Regarding the effect of different application scenarios in terms of economics,investing in the proposed system is more appropriate in regions with multiple energy demands,especially heating demand.These results demonstrate the technical advantages of the proposed system and provide guiding principles for its design,operation,and project investment.

Design issues for compressed air energy storage in sealed underground cavities

Compressed air energy storage （CAES） systems represent a new technology for storing very large amount of energy. A peculiarity of the systems is that gas must be stored under a high pressure （p - 10-30 MPa）. A lined rock cavern （LRC） in the form of a tunnel or shaft can be used within this pressure range. The rock mass surrounding the opening resists the internal pressure and the lining ensures gas tightness. The present paper investigates the key aspects of technical feasibility of shallow LRC tunnels or shafts under a wide range of geotechnical conditions. Results show that the safety with respect to uplift failure of the rock mass is a necessary but not a sufficient condition for assessing feasibility. The deformation of the rock mass should also be kept sufficiently small to preserve the integrity of the lining and, especially, its tightness. If the rock is not sufficiently stiff, buckling or fatigue failure of the steel lining becomes more decisive when evaluating the feasible operating air pressure. The design of the concrete plug that seals the compressed air stored in the container is another demanding task. Numerical analyses indicate that in most cases, the stability of the rock mass under the plug loading is not a decisive factor for plug design.

Experimental investigation on the energy evolution of dry and water-saturated red sandstones

In order to investigate the effect of water content on the energy evolution of red sandstone, the axial loading–unloading experiments on dry and water-saturated sandstone samples were conducted, and the distribution and evolution of elastic energy and dissipated energy within the rock were measured.The results show that the saturation process from dry to fully-saturated states reduces the strength, rigidity and brittleness of the rock by 30.2%, 25.5% and 16.7%, respectively. The water-saturated sample has larger irreversible deformation in the pre-peak stage and smaller stress drop in the post-peak stage.The saturation process decreases the accumulation energy limit by 38.9%, but increases the dissipated energy and residual elastic energy density, thus greatly reducing the magnitude and rate of energy release. The water-saturated sample has lower conversion efficiency to elastic energy by 3% in the prepeak region; moreover, the elastic energy ratio falls with a smaller range in the post-peak stage.Therefore, saturation process can greatly reduce the risk of dynamic disaster, and heterogeneous water content can lead to dynamic disaster possibly on the other hand.

Performance Analysis of Constant-Pressure Pumped Hydro Combined with Compressed Air Energy Storage System Considering Off-Design Model of Compressor

With the wide application of renewable energy, energy storage technology has become a research hotspot. In order to overcome the shortcomings of energy loss caused by compression heating in compressed air energy storage technology, a novel constant-pressure pumped hydro combined with compressed air energy storage system was proposed. To deepen the understanding of the system and make the analysis closer to reality, this paper adopted an off-design model of the compressor to calculate and analyze the effect of key parameters on system thermodynamics performance. In addition, the results of this paper were compared with previous research results, and it was found that the current efficiency considering the off-design model of compressor was generally 2% - 5% higher than the previous efficiency. With increased preset pressure or with decreased terminal pressure, both the previous efficiency and current efficiency of the system increased. The exergy destruction coefficient of the throttle valve reached 4%. System efficiency was more sensitive to changes in water pump efficiency and hydroturbine efficiency.

Performance Evaluation of Compressed Air Energy Storage Using TRNSYS

The appreciable economic growth in some of the developing countries like India in the recent years, towards providing energy security causes large environmental impact. Renewable Energy （RE） is being seen as one of the important means to meet the growing power needs of the economy while enhancing energy security and providing opportunities for mitigating greenhouse gas emissions. However, RE sources are highly intermittent in nature. The variability of these sources has led to concerns regarding the reliability of an electric grid that derives a large fraction of its energy from these sources as well as the cost of reliably integrating large amounts of variable generation into the electric grid. Hence at this juncture, it is necessary to explore the benefits of suitable Energy storage technologies. Compressed air energy storage （CAES） is a commercial, utility-scale technology that provides long-duration energy storage with fast ramp rates and good part-load operation. It is a promising storage technology for balancing the large-scale penetration of renewable energies, such as wind and solar power, into electric grids. Considering the potential of CAES storage, the present work, a thermodynamic model is developed with suitable assumptions and the simulation analysis is performed using transient system simulation （TRNSYS） v17 software. The system performanee is compared by considering the recovery during the heat of compression using a thermal storage system and without considering the heat recovery. The overall turnaround efficiency of the system without considering the thermal energy storage （TES） system is 57 % and with TES system the efficiency is increased to 70%.

Looping of Hybrid PV/Wind Turbine Power Plants by a Compressed Air Storage System and Creation of Artificial Wind to Ensure the Permanent Availability of Energy in the Tropical Zones

In general, the energy storage in facilities to intermittent sources is provided by a battery of accumulators. Having found that the duration of life of chemical accumulators is strongly shortened in the northern regions of Cameroon and that this has a considerable impact on the operating costs and the reliability of power plants to intermittent sources, this work proposes to find an alternative to these chemical accumulators rendered vulnerable by the high temperatures. It reviews all energy storage techniques and makes a choice （the CAES （compressed air energy storage）） based on thermal robustness. It proposes a new technique of restitution of the energy by producing an artificial wind from the compressed air. The feedback loop thus obtained by the compressor-tank-wind subsystem is studied from a series of manipulations and its efficiency is determined. To automate the operation of this system, a controller is required. The operating logic of the controller is provided in function of the precise states of the load, the tank and the natural sources.

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

Energy storage technology is an essential part of the efficient energy system.Compressed air energy storage(CAES)is considered to be one of the most promising large-scale physical energy storage technologies.It is favored because of its low-cost,long-life,environmentally friendly and low-carbon characteristics.The compressor is the core component of CAES,and the performance is critical to the overall system efficiency.That importance is not only reflected in the design point,but also in the continuous efficient operation under variable working conditions.The diagonal compressor is currently the focus of the developing large-scale CAES because of its stronger flow capacity compared with traditional centrifugal compressors.And the diagonal compressor has the higher single stage pressure ratio compared with axial compressors.In this paper,the full three dimensional numerical simulation technologies with synergy theory are used to compare and analyze the internal flow characteristics.The performance of the centrifugal and diagonal impellers that are optimized under the same requirements for large-scale CAES has been analyzed.The relationship between the internal flow characteristics and performance of the centrifugal and diagonal impellers with the change of mass flow rates and total inlet temperature is given qualitatively and quantitatively.Where the cosine value of the synergy angle is high,the local flow loss is large.The smaller proportion of the positive area is the pursuit of design.Through comparative analysis,it is concluded that the internal flow and performance changes of centrifugal and diagonal impellers are different.The results confirm the superiority and feasibility of the off-design performance of the diagonal compressor applied to the developing large-scale CAES.

Design Strategy of Diagonal Compressors in Compressed Air Energy Storage System

As a kind of large-scale physical energy storage,compressed air energy storage(CAES)plays an important role in the construction of more efficient energy system based on renewable energy in the future.Compared with traditional industrial compressors,the compressor of CAES has higher off-design performance requirements.From the perspective of design,it needs to pay attention not only to the performance of the design point,but also to the performance of all the stable working range.However,from the previous literature,no diagonal compressor was used in CAES which can meet the requirements,which also reflects the design program can be further improved.Therefore,this paper studies the design strategy of high efficient diagonal compressor for large-scale CAES,and gives the complete strategy algorithms used for different program modules.The pressure ratio,isentropic efficiency and stable working range are comprehensively considered.In the design process,the criteria for the key parameters of the diagonal flow angle of the diagonal compressor are given for the first time.The results show that the isentropic efficiency at the design point is 92.7%,the total pressure ratio is1.97,and the stable working range exceeds 20%,which meets the design requirements of the compressor for CAES and exceeds the overall performance of the previous compressors in the entire working range.

Conception of a new 4-quadrant hydrogen compressed air energy storage power plant with an integrated electrolyzer

A hydrogen compressed air energy storage power plant with an integrated electrolyzer is ideal for large-scale,long-term energy storage because of the emission-free operation and the possibility to offer multiple ancillary services on the German energy market.This paper defines analyzes such a storage concept and conducts an extensive comparison with four additional storage concepts based on various criteria.The results show that the combination of storing compressed air and hydrogen offers a higher efficiency than storing only hydrogen and lower specific investment costs than storing only compressed air.This result is confirmed with analysis of the optimal sizing of each power plant component for simultaneous participation on multiple energy markets with a linear optimization dispatch mode.The hydrogen compressed air energy storage(HCAES)power plant can utilize more revenue possibilities than a hydrogen energy storage because of the higher round-trip efficiency and the combination of the air compressor and the integrated electrolyzer during charging mode.The integration of the electrolyzer,however,offers a couple of challenges itself because of the highly flexible operation mode.A new concept for the controllable 24-pulse diode-thyristor rectifier of the electrolyzer is presented,that uses mostly common components while offering little to no grid harmonics and a long lifetime.The flexible integrated electrolyzer allows for the 4-quadrant operation of the storage power plant.

Electrochemical hydrogen compression and purification versus competing technologies: Part Ⅰ. Pros and cons

It is undisputed that hydrogen will play a great role in our future energetic mix, because it enables the storage of renewable electricity(power-to-H2) and the reversible conversion into electricity in fuel cell, not to speak of its wide use in the(petro)chemical industry. Whereas in these applications, pure hydrogen is required, today’s hydrogen production is still largely based on fossil fuels and can therefore not be considered pure. Therefore, purification of hydrogen is mandatory, at a large scale. In addition, hydrogen being the lightest gas, its volumetric energy content is well-below its competing fuels, unless it is compressed at high pressures(typically 70 MPa), making compression unavoidable as well. This contribution will detail the means available today for both purification and for compression of hydrogen. It will show that among the available technologies, the electrochemical hydrogen compressor(EHC), which also enables hydrogen purification, has numerous advantages compared to the classical technologies currently used at the industrial scale. EHC has their thermodynamic and operational advantages, but also their ease of use. However, the deployment of EHCs will be viable only if they reach sufficient performances, which implies some specifications that their base materials should stick to. The present contribution will detail these specifications.

Experimental study on compression stroke characteristics of free- piston engine generator

The compression stroke characteristics of free-piston engine generator were studied. The numerical model of the compression stroke was established based on thermodynamics and dynamics equation,and the leak loss,heat loss and friction loss were considered. Through solving numerical equations,the in-cylinder pressure of compression stroke under different compression ratios was calculated,energy transfer and conversion process was analyzed,and the calculated results were experimentally verified. The results showed that the actual effective output of electronic energy and the compression energy stored in the com-pressed gas accounted for about 70%. The compression energy gradually increased with the increasing com-pression ratio. When the compression ratio was more than 7. 5,the actual compression energy increased slowly and the energy error between simulation and test decreased.

Increasing Coal-Fired Power Plant Operational Flexibility by Integrating Solar Thermal Energy and Compressed Air Energy Storage System

This paper proposed a novel integrated system with solar energy,thermal energy storage(TES),coal-fired power plant(CFPP),and compressed air energy storage(CAES)system to improve the operational flexibility of the CFPP.A portion of the solar energy is adopted for preheating the boiler’s feedwater,and another portion is stored in the TES for the CAES discharging process.Condensate water from the CFPP condenser is used for cooling compressed air during the CAES charging process.The thermodynamic performance of the integrated system under different load conditions is studied.The system operations in a typical day are simulated with EBSILON software.The system enables daily coal saving of 9.88 t and reduces CO_(2)emission by 27.95 t compared with the original CFPP at 100%load.Under partial load conditions,the system enables maximum coal saving of 10.29 t and maximum CO_(2)emission reduction of 29.11 t at 75%load.The system has maximum peak shaving depth of 9.42%under 40%load condition.The potential of the system participating ancillary service is also discussed.It is found that the integration of solar thermal system and CAES system can bring significant ancillary service revenue to a conventional CFPP.

Efficiency Analysis of an Arrayed Liquid Piston Isothermal Air Compression System for Compressed Air Energy Storage

Compressed air energy storage(CAES)is an important technology in the development of renewable energy.The main advantages of CAES are its high energy capacity and environmental friendliness.One of the main challenges is its low energy density,meaning a natural cavern is required for air storage.High-pressure air compression can effectively solve the problem.A liquid piston gas compressor facilitates high-pressure compression,and efficient convective heat transfer can significantly reduce the compression energy consumption during air compression.In this paper,a near isothermal compression method is proposed to increase the surface area and heat exchange by using multiple tube bundles in parallel in the compression chamber in order to obtain high-pressure air using liquid-driven compression.Air compression with a compression ratio of 6.25:1 is achieved by reducing the tube diameter and increasing the parallel tube number while keeping the compression chamber cross-sectional area constant in order to obtain a high-pressure air of 5 MPa.The performances of this system are analyzed when different numbers of tubes are applied.A system compression efficiency of 93.0%and an expansion efficiency of 92.9%can be achieved when 1000 tubes are applied at a 1 minute period.A new approach is provided in this study to achieve high efficiency and high pressure compressed air energy storage.

Gigawatt Scale Storage for Gigawatt Scale Renewables

Multi-GW renewables need multi-GW storage, or fossil fuelled power stations will be needed to balance for intermittency. For the same reason, such balancing must be able to last for an entire evening peak if renewables are not generating at the same time. Batteries and DSR （demand side response） make very useful contributions and there is a large market for both, but without large scale and long duration storage, they cannot do the job. Interconnectors also contribute to the solution, and storage will make them more profitable, but （taking a UK perspective） Ofgem identified that all our neighbours have similar generation capacity crunches and similar demand patters, so if we need the electricity when they do, we’ll have to pay through the nose for it. Last winter’s ￡ 1,500/MWh prices proved that―even with only 4 GW interconnection. Following exit from the single market, our neighbours will be able to say “our consumers are more important than yours at any price”. We need UK-based storage at the right scale, to store UK-generated electricity for UK use and for export―otherwise we lose security of supply. CAES （compressed air energy storage） and pumped hydro are the only technologies currently able to deliver this scale and duration of storage. Pumped hydro is cost-effective in the long term but there are few sites, and it is （location dependent） over 3x the cost of CAES. Storelectric has 2 versions of CAES： one is a comparable price to existing CAES, but much more efficient （~70% v 50%） and zero emissions （existing CAES emits 50%-60% of the gas of an equivalent sized power station）. The other is retro-fittable to suitable gas power stations, is more efficient （-60% v 50%）, almost halves their emissions, adds storage-related revenue streams and is much cheaper. Both are new configurations of existing and well proven technologies, supported by engineering majors.