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.

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.

Research on Storage Capacity of Compressed Air Pumped Hydro Energy Storage Equipment

Compressed air pumped hydro energy storage equipment combines compressed air energy storage technology and pumped storage technology. The water is pumped to a vessel to compress air for energy storage, and the compressed air expanses pushing water to drive the hydro turbine for power generation. The novel storage equipment saves natural gas resources, reduces carbon emission, and improves the controllability and reliability. The principle of compressed air pumped hydro energy storage is introduced and its mathematical model is built. The storage and generation process of the novel equipment is analyzed using the model. The calculation formula of the storage power is deduced in theory in different situations of isothermal and adiabatic compression. The optimal storage scheme is given when the capacity and withstand pressure of the vessel is definitive, and the max available capacity and the equipment utilization efficiency evaluation of the scheme is given.

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.

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.

Response Characteristics of Flexible Risers in Offshore Compressed Air Energy Storage Systems

With the rapid development of marine renewable energy technologies, the demand to mitigate the fluctuation of variable generators with energy storage technologies continues to increase. Offshore compressed air energy storage (OCAES) is a novel flexible-scale energy storage technology that is suitable for marine renewable energy storage in coastal cities, islands, offshore platforms, and offshore renewable energy farms. For deep-water applications, a marine riser is necessary for connecting floating platforms and subsea systems. Thus, the response characteristics of marine risers are of great importance for the stability and safety of the entire OCAES system. In this study, numerical models of two kinds of flexible risers, namely, catenary riser and lazy wave riser, are established in OrcaFlex software. The static and dynamic characteristics of the catenary and the lazy wave risers are analyzed under different environment conditions and internal pressure levels. A sensitivity analysis of the main parameters affecting the lazy wave riser is also conducted. Results show that the structure of the lazy wave riser is more complex than the catenary riser;nevertheless, the former presents better response performance.

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%.

Research on New Compressed Air Energy Storage Technology

In recent years, wind power generation and photovoltaic power generation have been developing rapidly, and the installed capacity of the new resources generation has been keeping a fast growth every year. But with the incorporation into the grid, the new resources generation that has the properties such as randomness and volatility causes certain risks to the power grid, which results in the falling of the incorporation proportion instead of rising. This paper describes the current status and development problems of the new energy in China, and gives a brief introduction of characteristics of various energy storage technologies. This paper focuses on the analysis of the compressed air energy storage technology in recent years and new developments and the latest technology at home and abroad, additionally, the paper introduces a new concept of the compressed air energy storage system.

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.

计及AA-CAES与PTC集成的综合能源系统运行优化与性能分析

为进一步发挥综合能源系统的多能互补优势,提出一种计及先进绝热压缩空气储能(AA-CAES)与槽式太阳能集热器(PTC)集成的综合能源系统(IES-PTC-CAES)优化运行策略。首先,对AA-CAES、PTC以及系统中其他设备进行分析并建立相应模型;进而以经济性、环保性和能效性为优化目标,以设备运行的关键参数为优化变量,基于分时电价建立了协同优化策略,并通过K-means算法将模拟出的典型年负荷聚类为典型日负荷;最终,使用并行式的遗传算法对系统进行寻优,得到不同目标下IES-PTC-CAES的最优运行策略。结果表明:与参考系统相比,IES-PTC-CAES系统经济目标下总成本降低了14.61万元,环保目标下二氧化碳排放量减少了6194.38 kg。

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.

渗透率各向异性对CAESA系统季节性运行性能的影响

【目的】储层岩石渗透率通常呈各向异性分布,探究储层岩石渗透率各向异性对含水层压缩空气储能(compressed air energy storage in aquifers,CAESA)系统季节性运行性能的影响。【方法】建立CAESA系统概念模型和三维井群-储库数值模型,拟定3种储层渗透率各向异性分布方案,运用T2WELL/EOS3数值模拟软件,研究CAESA系统在季节性运行模式和渗透率各向异性条件下的流体传质和传热过程。【结果】储层渗透率各向异性会影响井筒-储层中的气相运移、流体交互和温压传递过程,进而影响系统的储能效率;当渗透率横纵比从2.0升高至10.0时,井筒的最大压力降低2.79 MPa,抽采阶段井口的最高温度升高2.06℃,井口两相流现象出现的时间从系统运行第435 d提前至第410 d,系统储能效率从89.8%降低至60.1%。【结论】对于渗透率各向异性程度较高的储层,可以通过增加初始气囊注入量或在后期进行补气来增加系统支撑压力,还可以采用注浆等工程手段,建立人造低渗边界以优化储层条件,提升系统储能效率。

基于AA-CAES电站和综合需求响应的供暖期弃风消纳策略

“双碳”目标背景下,为解决热电联产机组“以热定电”模式导致的大规模弃风问题,本文提出基于先进绝热压缩空气储能电站(advanced adiabatic compressed air energy storage,AA-CAES)和综合需求响应的综合能源系统(integrated energy system,IES)供暖期弃风消纳策略。首先,在“源-储”两侧建立热电联产机组与AA-CAES电站耦合运行模型,分析耦合运行实现热电解耦机理;其次,在“荷”侧引入价格型和替代型需求响应机制来探寻负荷侧优化系统调度潜力;然后,在IES中引入碳捕集系统和阶梯型碳交易机制来约束碳排放,并在碳排放量最少、综合成本最低为目标构建IES运行基础上,引入模糊机会规划约束模型来分析风、光不确定性对系统调度影响;最后,利用西北某地区实际数据进行算例验证。结果表明:热电机组与AA-CAES电站耦合运行相较于未耦合运行可提高风电消纳率84.55%、降低总成本11.42%、减少碳排放20.28%;综合需求响应机制的引入可进一步提高风电消纳率35.00%、降低总成本20.93%、减少碳排放24.43%;风光不确定性的上升会提高与外部电网的交互成本。

利用ORC-VCR回收压缩热的预冷式CAES系统性能分析

常规非绝热压缩空气储能(D-CAES)系统的储能过程通常采用四级以上的压缩机组以减少空气压缩功的消耗,导致产生大量的低品位压缩热直接排放到环境中,能源浪费严重。针对这一问题,本工作提出了一种采用有机朗肯循环-蒸汽压缩制冷(ORC-VCR)回收压缩热的预冷式CAES系统(ORC-VCR-CAES),通过回收空气压缩阶段压缩机产生的压缩热来对压缩机入口空气进行预冷,可以进一步降低空气压缩功的消耗,提高系统的循环效率。对ORC-VCR-CAES耦合系统进行了热力学分析和经济性分析。结果表明,不同ORC-VCR循环工质对系统性能的影响较大,采用R152a作为循环工质的ORC-VCR-CAES系统综合性能最佳。其系统循环效率可达64.15%,比常规D-CAES系统提高了5.94%;在考虑外部废热能量输入时,ORC-VCR-CAES系统(火用)效率为51.90%,比常规D-CAES系统提高了4.81%。通过压缩热的回收有效减少了冷却器的(火用)损失,但压缩机组的(火用)损失仍然较大,是系统进一步优化的关键部件;经济性分析表明,当峰谷电价为1.26元和0.30元时,ORC-VCR-CAES系统的项目净现值相比于常规D-CAES系统可增加12.48%,且峰谷电价差越小,ORC-VCRCAES相比于常规D-CAES系统的项目净现值增加百分比越高。

地下水对CAES地下储气库气密性和围岩稳定性影响

压缩空气储能(CAES)储气库密封和稳定是保证电站安全稳定运行的基础,储气库受力影响因素众多,且特性复杂,长期运行过程中气密性和稳定性的精准预测和评估一直是热点和难点。以考虑渗漏和传热过程的压缩空气热力学模型为非稳态边界、以热流固耦合理论为核心建立了储气库多物理场耦合下气密性和稳定性联合分析模型,探讨了洞周围岩中的地下水对储气库气密性和稳定性的影响。研究成果表明:(1)地下水的存在可使储气库每个循环气体损失量降低78%;(2)衬砌结构主要受拉应力作用,顶部和底部出现了应力集中现象,需进行加密配筋;(3)岩体中存在地下水有助于强化储气库内的气体密封效果。

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.

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.