压缩空气储能示范进展及商业应用场景综述

    [目的]   近年来,储能技术及储能产业发展受到的关注度持续升温。    [方法]   在此背景下,对压缩空气储能技术及其商业应用场景进行了分析与综述。通过梳理国内致力于压缩空气储能技术示范的研究团队及其技术特点,较为全面地反映了国内压缩空气储能技术的发展方向;在此基础上,介绍了已投运数十年的德国汉特福及美国阿拉巴马州两座商业化压缩空气储能电站的配置参数及运行经验,综述了近年来国内外针对多种新型压缩空气储能技术的示范进展状况。结合压缩空气储能技术梳理、商业化储能电站回顾及新型压缩空气储能技术示范进展综述三方面的工作,可为国内压缩空气储能技术发展及国家多部委大力推动的储能行业发展提供借鉴。最后,从电源侧储能、电网侧储能及用户侧储能三类应用场景分析了压缩空气储能技术的适应性及应用潜力。    [结果]   德国及美国两座商业化压缩空气储能电站数十年的可靠运行经验,检验了压缩空气储能电站长期运行的可靠性。与此同时,国内自500 kW至10 MW等多容量规模压缩空气储能示范工程的先后投建,表明此项储能技术在国内已实现由理论研究阶段向示范验证阶段的突破。    [结论]   在当下政策环境,用户侧峰谷电价政策是较为典型的储能应用场景边界条件,在压缩空气储能技术推广中可以重点考虑。     

压缩空气储能系统的理论分析及性能研究

压缩空气储能技术和抽水蓄能技术是两种最具潜力的电能规模化储存技术。构建了四套压缩空气储能方案,结合热力学第一定律对高压储罐内压缩空气的温度与压力参数的变化规律以及不同储能方案性能进行了比较。研究结果表明,高压储罐在与环境换热较差时,高压储罐的充气过程会经历较为明显的温升现象。200 m3储罐以1.0 kg/s流速充气至10 MPa时,温升幅度为22.46 ℃,储气过程的温升现象降低了储罐的空气容纳能力。在压缩空气储能系统性能方面,四套储能系统的热耗位于4 100 kJ/kW·h至4 200 kJ/kW·h之间,系统效率位于52.30%与56.33%之间。在储能系统效率与对外输出电能总量指标上,高压储罐与环境之间换热性能较好的储能系统均要优于换热条件较差的储能系统。     

Performance comparison of different combined heat and compressed air energy storage systems integrated with organic Rankine cycle

Compressed air energy storage (CAES) is promising to enable large‐scale penetration of renewable energies (REs). However, conventional diabatic CAES (D‐CAES) depends largely on fossil fuels, while adiabatic CAES (A‐CAES) is limited in output power. To conquer these disadvantages, concept of combined heat and CAES (CH‐CAES) is proposed in this paper. The proposed system couples an electric heater with conventional A‐CAES. During charging, electricity storage transforms from pure compression to partly relying on Joule heating. The stored heat in an electric heater will be used to boost turbine inlet temperature during discharging. Consequently, system charge/discharge capacity can be improved without enlarging cavern size, raising cavern pressure, and producing greenhouse gases. This paper discusses three types of CH‐CAES systems with different electric heater installation positions. Off‐design performance analysis for each system is conducted on the basis of turbomachinery (compressors, turbines, and the pump) characteristic maps and heat exchangers off‐design models. Performance comparison is conducted between these three CH‐CAES systems (called Mode II, III, and IV for simplification) and the conventional A‐CAES system (Mode I). Control strategies are also given in this paper. Results show that the EVR (energy generated per unit volume of storage) increases with participation of an electric heater, while the RTE (system roundtrip efficiency) slightly decreases. Mode I has the highest RTE. The largest EVR appears in Mode III where the electrical heater is in series with the intercooler and after cooler. Mode II is a compromise solution to achieve both relatively high RET and EVR when the electrical heater is installed in series only with the intercooler. Mode IV with a paralleling electrical heater has great flexibility to adapt different user demands. The integration of the ORC has a positive effect on system RTE and EVR.     

The value of compressed air energy storage with wind in transmission-constrained electric power systems

In this work, we examine the potential advantages of co-locating wind and energy storage to increase transmission utilization and decrease transmission costs. Co-location of wind and storage decreases transmission requirements, but also decreases the economic value of energy storage compared to locating energy storage at the load. This represents a tradeoff which we examine to estimate the transmission costs required to justify moving storage from load-sited to wind-sited in three different locations in the United States. We examined compressed air energy storage (CAES) in three “wind by wire” scenarios with a variety of transmission and CAES sizes relative to a given amount of wind. In the sites and years evaluated, the optimal amount of transmission ranges from 60% to 100% of the wind farm rating, with the optimal amount of CAES equal to 0–35% of the wind farm rating, depending heavily on wind resource, value of electricity in the local market, and the cost of natural gas.     

Compressed Air Energy Storage in an Electricity System With Significant Wind Power Generation

In this paper, a stochastic electricity market model is applied to estimate the effects of significant wind power generation on system operation and on economic value of investments in compressed air energy storage (CAES). The model's principle is cost minimization by determining the system costs mainly as a function of available generation and transmission capacities, primary energy prices, plant characteristics, and electricity demand. To obtain appropriate estimates, notably reduced efficiencies at part load, start-up costs, and reserve power requirements are taken into account. The latter are endogenously modeled by applying a probabilistic method. The intermittency of wind is covered by a stochastic recombining tree and the system is considered to adapt on increasing wind integration over time by endogenous modeling of investments in selected thermal power plants and CAES. Results for a German case study indicate that CAES can be economic in the case of large-scale wind power deployment     

Optimal operation strategies of compressed air energy storage (CAES) on electricity spot markets with fluctuating prices

Compressed air energy storage (CAES) technologies can be used for load levelling in the electricity supply and are therefore often considered for future energy systems with a high share of fluctuating renewable energy sources, such as e.g. wind power. In such systems, CAES plants will often operate on electricity spot markets by storing energy when electricity prices are low and producing electricity when prices are high. In order to make a profit on such markets, CAES plant operators have to identify proper strategies to decide when to sell and when to buy electricity. This paper describes three independent computer-based methodologies which may be used for identifying the optimal operation strategy for a given CAES plant, on a given spot market and in a given year. The optimal strategy is identified as the one which provides the best business-economic net earnings for the plant. In practice, CAES plants will not be able to achieve such optimal operation, since the fluctuations of spot market prices in the coming hours and days are not known. Consequently, two simple practical strategies have been identified and compared to the results of the optimal strategy. This comparison shows that, in practice, a CAES plant can be expected to earn 80-90 per cent of the optimal earnings.     

Conceptual design of compressed air energy storage electric power systems

Conceptual design studies have been conducted to identify Compressed Air Energy Storage (CAES) systems which are technically feasible and potentially attractive for future electric utility load-levelling applications. The CAES concept consists of compressing air during off-peak periods and storing it in underground facilities for later use. During peak-load periods the air would be withdrawn, heated by recuperation and combustion and expanded through turbines to generate power. By using off-peak electricity for compression and stored air for peak-load generation, the resulting oil consumption would be about 40 per cent of that consumed by conventional gas-turbine peaking plants. The turbomachinery requirements for this type of system could be met using existing equipment with relatively modest modifications. Although the study discussed herein focused on the storage of air in hydraulically compensated, mined, hard-rock caverns, the compressed air could also be stored in underground aquifers or leached-out salt cavities. Conventional underground excavation technology could be used to construct these storage caverns. A geological survey of the north-central and north-east regions of the United States indicated that sufficient siting opportunities exist such that a prudently designed CAES plant should have little long-term adverse impact on the environment. The competitive position of CAES relative to conventional generation alternatives is highly dependent on utility-specific factors. The cost of electric energy from CAES is generally competitive with costs from conventional peak-shaving systems such as gas turbines and will improve as low-cost off-peak energy from nuclear plants becomes available.     

Design and thermodynamic analysis of compressed air energy storage system

压缩空气储能技术具有提升风能与太阳能等可再生资源电能质量的潜力,通过此项技术实现间歇性与不稳定性可再生电力的有效储存,进而在电网负荷高峰期以优质电力的形式稳定输出.结合热力学分析方法设计了储能功率56.58 MW,释能输出功率154.76 MW的压缩空气储能系统.在释能阶段透平机组配置上,参照GE 9171E燃机布置第二级透平入口参数,并以其812.41 K高温烟气余热提供第一级透平工质所需全部热量,无需为第一级透平配备专门燃烧器.在此思路下设计的压缩空气储能系统,热耗可降低至3783.96 kJ/(kW·h),储能系统的能量转换效率也高达56.11%.     

Techno‐economic study of compressed air energy storage systems for the grid integration of wind power

Integrating variable renewable energy from wind farms into power grids presents challenges for system operation, control, and stability due to the intermittent nature of wind power. One of the most promising solutions is the use of compressed air energy storage (CAES). The main purpose of this paper is to examine the technical and economic potential for use of CAES systems in the grid integration. To carry out this study, 2 CAES plant configurations: adiabatic CAES (A‐CAES) and diabatic CAES (D‐CAES) were modelled and simulated by using the process simulation software ECLIPSE. The nominal compression and power generation of both systems were given at 100 and 140 MWe, respectively. Technical results showed that the overall energy efficiency of the A‐CAES was 65.6%, considerably better than that of the D‐CAES at 54.2%. However, it could be seen in the economic analysis that the breakeven electricity selling price (BESP) of the A‐CAES system was much higher than that of the D‐CAES system at €144/MWh and €91/MWh, respectively. In order to compete with large‐scale fossil fuel power plants, we found that a CO₂ taxation scheme (with an assumed CO₂‐tax of €20/tonne) improved the economic performance of both CAES systems significantly. This advantage is maximised if the CAES systems use low carbon electricity during its compression cycle, either through access to special tariffs at times of low carbon intensity on the grid, or by direct coupling to a clean energy source, for example a 100‐MW class wind farm.     

压缩空气储能技术现状与发展趋势

在分析传统压缩空气储能（CAES）技术的工作原理和技术特点的基础上,介绍了压缩空气储能技术的发展,包括非绝热压缩空气储能技术（D-CAES）、绝热压缩空气储能技术（A-CAES）、液化空气储能技术（LAES）和超临界压缩空气储能技术（SC-CAES）等,并给出了评价不同系统性能的技术参数。以国际上第一座压缩空气储能电站——德国Huntorf电站的运行参数和相关情况为例,分析了D-CAES技术的应用情况;对压缩空气储能技术在美国及其他国家和地区的应用和发展现状进行分析。通过对比不同的压缩空气储能技术方案,分析了A-CAES、LAES、SC-CAES及LCES储能系统的先进性、竞争优势与不足,分析了未来CAES技术的发展趋势。     

Economic feasibility and optimisation of an energy storage system for Portland Wind Farm (Victoria,Australia)

This paper presents the details of a theoretical study of the economic advantages of using large-scale energy storage to complement a wind farm in a base-load dominated electricity grid. A computer model is developed which simulates the operation of several energy storage systems when used with the 190-MW Portland Wind Farm (PWF) located in Portland, Victoria, Australia. A variety of operating strategies are compared with the results of a dynamic programming model which finds the maximum possible revenue which a given system can generate for a set of input conditions. Three energy storage systems are modelled and costed: Pumped Seawater Hydro Storage (PSHS), Compressed Air Energy Storage (CAES), and Thermal Energy Storage (TES). It is found that CAES is the most profitable storage medium, requiring a capital expenditure of A$140 M and generating a rate of return (ROR) of 15.4%. The ROR for PSHS was 9.6%, and for TES was 8.0%. Therefore, a significant investment opportunity exists for the installation of an energy storage system in this wind farm. It is therefore highly recommended that CAES is investigated further with the aim of introducing large-scale energy storage to PWF and other similar wind turbine installations.     

Dynamic characteristics and operation strategy of the discharge process in compressed air energy storage systems for applications in power systems

In the context of the rapid development of large-scale renewable energy, large-scale energy storage technology is widely considered as the most effective means of improving the quality and security of electricity. In the existing energy storage technology, advanced adiabatic compressed air energy storage (AA-CAES) technology has broad application prospects because of its advantages of low pollution, low investment, flexible site selection, and large capacity. However, the lack of an in-depth understanding of the dynamic characteristics of CAES systems has severely limited the development of system design and control strategy, resulting in a lack of commercial operation of large-scale CAES systems. This paper describes the design and implementation of a CAES plant and its controller for applications in the distribution network level. The dynamic mathematical models of AA-CAES were established and a feasible control strategy for the grid-connected process was developed to analyze the dynamic characteristics of the system in the discharge stage. The work done in this study provided a data reference for the deep understanding of the dynamic characteristics of AA-CAES, system design, and control strategy in the industry.     

Dynamic simulation of air storage–based gas turbine plants

Cavern storage is a proven energy storage technology, capable of storing energy in the form of compressed air inside a cavern. The Huntorf plant and the Alabama plants use this technology to store electrical energy during the off‐peak load hours by compressing the air inside a cavern and then using this compressed air during gas turbine operation to generate electricity during peak load demand hours. The advantage of doing this is that it increases the efficiency of gas turbine operation while meeting the grid generation and the load balance. The operation of a typical compressed air energy storage (CAES)–based gas turbine plant involves the operation of several components, including the compressor, the cavern storage, the combustor, the turbine, and so on. The dynamics of the plant as a whole depends on the performance of the individual components. The focus of this article is to develop a Simulink‐based models for each of the individual components, which can then be assembled appropriately to design an entire CAES plant. As an illustration, a case study for the Huntorf CAES plant is presented with the developed models. A typical daily operation of the Huntorf plant is simulated and compared with the reported Huntorf plant data. The model accurately captures the reported dynamics of the cavern storage. In addition, the reported quantities like the compressor power consumption, the turbine power generation, and the temperature at different junctions of the CAES plant match well with the simulated results. Copyright © 2011 John Wiley & Sons, Ltd.     

Thermo-economic analysis and sizing of a PV plant equipped with a compressed air energy storage system

Photovoltaic (PV) farms are widely used around the world to provide required electricity. Compressed air energy storage (CAES) system has been already proposed for energy storage applications in large scales. In this work, employing a CAES unit equipped with an ancillary solar heating system for a large scale PV farm in Brazil is proposed. A PV farm with 100 MWp (megawatt peak) capacity is proposed to be built in the most suitable point within Brazil. The sizing of the CAES unit and the solar heating system, which has not been investigated, along with selecting the best power sales strategy for the power plant, which has been always a challenge for renewable energy source power plants, are carried out emphasizing energy-economic considerations. In order to prove the proficiency of the proposal, the performance of the power plant and energy storage unit is assessed over a sample year. In order to have a comprehensive economic analysis, Net Present Value (NPV) method is employed and all the possible uncertainties in the system have been taken into account.     

The technical,geographical, and economic feasibility for solar energy to supply the energy needs of the US

So far, solar energy has been viewed as only a minor contributor in the energy mixture of the US due to cost and intermittency constraints. However, recent drastic cost reductions in the production of photovoltaics (PV) pave the way for enabling this technology to become cost competitive with fossil fuel energy generation. We show that with the right incentives, cost competitiveness with grid prices in the US (e.g., 6–10 US¢/kWh) can be attained by 2020. The intermittency problem is solved by integrating PV with compressed air energy storage (CAES) and by extending the thermal storage capability in concentrated solar power (CSP). We used hourly load data for the entire US and 45-year solar irradiation data from the southwest region of the US, to simulate the CAES storage requirements, under worst weather conditions. Based on expected improvements of established, commercially available PV, CSP, and CAES technologies, we show that solar energy has the technical, geographical, and economic potential to supply 69% of the total electricity needs and 35% of the total (electricity and fuel) energy needs of the US by 2050. When we extend our scenario to 2100, solar energy supplies over 90%, and together with other renewables, 100% of the total US energy demand with a corresponding 92% reduction in energy-related carbon dioxide emissions compared to the 2005 levels.     

Economic evaluation of the dual mode CAES solution for increased wind energy contribution in autonomous island networks

Wind parks operating in autonomous island grids, such as those encountered in the Aegean Archipelago, face considerable wind energy curtailments, owed to the inability of local electricity networks to absorb the entire wind energy production. On the other hand, plans promoting the natural gas-based electricity generation in big islands (such as Crete) question the future of wind energy. To recover wind energy curtailments and benefit from the introduction of natural gas, the adoption of compressed air energy storage (CAES) systems suggests an appreciable energy solution. Furthermore, to improve the economic performance of the proposed system, it is decided that guaranteed energy amounts should be delivered to the local grid during peak demand periods. In an effort to obtain favourable negotiation conditions – for the selling price of energy delivered – and also improve the economic performance of the system, a dual mode CAES operation is currently examined. Proceeding to the economic evaluation of dual mode CAES configurations that ensure maximum wind energy recovery, the feasibility of the proposed system may be validated. Lower electricity production costs and considerable reduction of fuel consumption achieved – in comparison with the requirements of conventional peak demand power units – illustrate the system's advantages.     

Current application situation and development prospect of physical energy storage technologies

作为可再生能源并网的关键技术,可再生能源的高速发展也带动了储能产业的发展和成熟。物理储能技术,发展历史长,技术较为成熟,部分已实现商业化运作;以抽水蓄能为代表,是电网调峰的主力,也在储能市场容量中占据着绝对份额。但无论是传统抽水蓄能,还是压缩空气储能都对环境、地理地质条件有较高的要求,极大地制约了这些技术的普遍推广和应用。因此物理储能也经历着应用模式的变革、传统技术向新兴技术转化的过程。虽然抽水蓄能、压缩空气储能和飞轮储能三种物理储能技术在原理、应用领域、安装容量以及未来发展趋势上各不相同, 但作为战略新兴技术,都需要技术的突破、政策和资金的支持以及更多的市场应用机会。     

System behaviour of compressed-air energy-storage in Denmark with a high penetration of renewable energy sources

In 2005, wind power supplied 19% of the 36 TWh annual electricity demand in Denmark, while 50% was produced at combined heat-and-power plants (CHP). The installed wind-turbine capacity in Western Denmark exceeds the local demand at certain points in time. So far, excess production has been exported to neighbouring countries. However, plans to expand wind power both in Denmark and in its neighbouring countries could restrain the export option and create transmission congestion challenges. This results in a need to increase the flexibility of the local electricity-system. Compressed-Air Energy-Storage (CAES) has been proposed as a potential solution for levelling fluctuating wind-power production and maintaining a system balance. This paper analyses the energy-balance effects of adding CAES to the Western Danish energy-system. Results show that even with an unlimited CAES plant capacity, excess power production is not eliminated because of the high percentage of CHP production. The optimal wind-power penetration for maximum CAES operation is found to be around 55%. The minimum storage size for CAES to fully eliminate condensing power plants operation in the optimized system is over 500 GWh, which corresponds to a cavern volume of around 234 Mm³ at an average pressure of 60 bar. Such a storage size would be technically and economically unfeasible. The analysis, however, did not include the potential role of a CAES plant in regulating the power services.     

Operating characteristics of constant-pressure compressed air energy storage (CAES) system combined with pumped hydro storage based on energy and exergy analysis

Energy storage systems are becoming more important for load leveling, especially because of the widespread use of intermittent renewable energy. Compressed air energy storage (CAES) is a very promising method for energy storage because CAES relies on existing technologies, is less expensive, and easier to site and permit, as compared to pumped hydro storage. But, in the case of CAES employing hard rock caverns or man-made air vessels, although the smallest possible cavern volume is desirable in order to minimize the construction cost and optimize utilization of the given space, the operating pressure range in the cavern must be limited in order to reduce the deterioration in efficiency of the CAES system at off-design conditions. In this paper, a new constant-pressure CAES system combined with pumped hydro storage was studied to address the current problem associated with the conventional CAES systems. An energy and exergy analysis of the novel CAES system was performed in order to understand the operation characteristics of the system according to several different compression and expansion processes; we then examined the effects of the height of the storage cavern and heat transfer between two media (air, water) and the cavern on the performance of the novel CAES system.     

Economics of compressed air energy storage to integrate wind power: A case study in ERCOT

Compressed air energy storage (CAES) could be paired with a wind farm to provide firm, dispatchable baseload power, or serve as a peaking plant and capture upswings in electricity prices. We present a firm-level engineering-economic analysis of a wind/CAES system with a wind farm in central Texas, load in either Dallas or Houston, and a CAES plant whose location is profit-optimized. With 2008 hourly prices and load in Houston, the economically optimal CAES expander capacity is unrealistically large – 24 GW – and dispatches for only a few hours per week when prices are highest; a price cap and capacity payment likewise results in a large (17 GW) profit-maximizing CAES expander. Under all other scenarios considered the CAES plant is unprofitable. Using 2008 data, a baseload wind/CAES system is less profitable than a natural gas combined cycle (NGCC) plant at carbon prices less than $56/tCO₂ ($15/MMBTU gas) to $230/tCO₂ ($5/MMBTU gas). Entering regulation markets raises profit only slightly. Social benefits of CAES paired with wind include avoided construction of new generation capacity, improved air quality during peak times, and increased economic surplus, but may not outweigh the private cost of the CAES system nor justify a subsidy.