37-408: CAES or C.A.E.S. may refer to: Compressed-air energy storage MIT Center of Advanced Engineering Study , a department of Massachusetts Institute of Technology Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title CAES . If an internal link led you here, you may wish to change
74-486: A 19 million cubic foot solution-mined salt cavern to store air at up to 1100 psi. Although the compression phase is approximately 82% efficient, the expansion phase requires the combustion of natural gas at one-third the rate of a gas turbine producing the same amount of electricity at 54% efficiency. In 2012, General Compression completed construction of a 2-MW near-isothermal project in Gaines County, Texas ,
111-464: A certain limit, as do the stresses induced on the storage vessels. The storage vessel is often a cavern created by solution mining (salt is dissolved in water for extraction) or by using an abandoned mine ; use of porous and permeable rock formations (rocks that have interconnected holes, through which liquid or air can pass), such as those in which reservoirs of natural gas are found, has also been studied. In some cases, an above-ground pipeline
148-540: A cost of $ 208 million, operating in 2024 with 64% efficiency. In 2009, the US Department of Energy awarded $ 24.9 million in matching funds for phase one of a 300-MW, $ 356 million Pacific Gas and Electric Company installation using a saline porous rock formation being developed near Bakersfield in Kern County, California . The goals of the project were to build and validate an advanced design. In 2010,
185-608: A similar approach, substituting seawater for air. The venturi warms the exhaust of the preceding stage and admits this preheated air to the following stage. This approach was widely adopted in various compressed-air vehicles such as H. K. Porter, Inc. 's mining locomotives and trams. Here, the heat of compression is effectively stored in the atmosphere (or sea) and returned later on. Compression can be done with electrically-powered turbo-compressors and expansion with turbo-expanders or air engines driving electrical generators to produce electricity. Air storage vessels vary in
222-685: A smaller scale, such as exploited by air cars and air-driven locomotives , and can use high-strength (e.g., carbon-fiber ) air-storage tanks. In order to retain the energy stored in compressed air, this tank should be thermally isolated from the environment; otherwise, the energy stored will escape in the form of heat, because compressing air raises its temperature. Citywide compressed air energy systems for delivering mechanical power directly via compressed air have been built since 1870. Cities such as Paris , France; Birmingham , England; Dresden , Rixdorf , and Offenbach , Germany; and Buenos Aires , Argentina, installed such systems. Victor Popp constructed
259-549: A target of 70% efficiency by using 600 °C (1,112 °F) air at 100 bars of pressure. This project was delayed for undisclosed reasons until at least 2016. Storelectric Ltd planned to build a 40-MW 100% renewable energy pilot plant in Cheshire , UK, with 800 MWh of storage capacity (2017). Hydrostor completed the first commercial A-CAES system in Goderich, Ontario , supplying service with 2.2MW / 10MWh storage to
296-486: Is 0%, then it is totally adiabatic; with an efficiency of 100%, it is totally isothermal. Typically with a near-isothermal process, an isothermal efficiency of 90–95% can be expected. One implementation of isothermal CAES uses high-, medium-, and low-pressure pistons in series. Each stage is followed by an airblast venturi pump that draws ambient air over an air-to-air (or air-to-seawater) heat exchanger between each expansion stage. Early compressed-air torpedo designs used
333-490: Is a constant pressure outside of the vessel, which is equal to the starting pressure p A {\displaystyle p_{A}} , the positive work of the outer pressure reduces the exploitable energy (negative value). This adds a term to the equation above: Intercooler Too Many Requests If you report this error to the Wikimedia System Administrators, please include
370-526: Is a way to store energy for later use using compressed air . At a utility scale, energy generated during periods of low demand can be released during peak load periods. The first utility-scale CAES project was in the Huntorf power plant in Elsfleth, Germany , and is still operational as of 2024 . The Huntorf plant was initially developed as a load balancer for fossil-fuel-generated electricity , but
407-461: Is expected to be 70%. Heat can be stored in a solid such as concrete or stone, or in a fluid such as hot oil (up to 300 °C) or molten salt solutions (600 °C). Storing the heat in hot water may yield an efficiency around 65%. Packed beds have been proposed as thermal storage units for adiabatic systems. A study numerically simulated an adiabatic compressed air energy storage system using packed bed thermal energy storage. The efficiency of
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#1732783416926444-410: Is no exergy loss in the heat transfer process, and so the compression work can be completely recovered as expansion work: 100% storage efficiency. However, in practice, there is always a temperature difference in any heat transfer process, and so all practical energy storage obtains efficiencies lower than 100%. To estimate the compression/expansion work in an isothermal process, it may be assumed that
481-406: Is the absolute pressure , V A {\displaystyle V_{A}} is the (unknown) volume of gas compressed, V B {\displaystyle V_{B}} is the volume of the vessel, n {\displaystyle n} is the amount of substance of gas (mol), and R {\displaystyle R} is the ideal gas constant . If there
518-403: Is usually made up of a series of parallel fins. As the gas is compressed, the heat of compression is rapidly transferred to the thermal mass, so the gas temperature is stabilized. An external cooling circuit is then used to maintain the temperature of the thermal mass. The isothermal efficiency (Z) is a measure of where the process lies between an adiabatic and isothermal process. If the efficiency
555-753: The Gem project at Rosamond in Kern County, California , was planned to provide 500 MW / 4,000 MWh of storage. The Pecho project in San Luis Obispo, California , was planned to be 400 MW / 3,200 MWh. The Broken Hill project in New South Wales , Australia was 200 MW / 1,600 MWh. In 2023, Alliant Energy announced plans to construct a 200-MWh compressed CO 2 facility based on the Sardinia facility in Columbia County, Wisconsin . It will be
592-824: The Ontario Grid (2019). It was the first A-CAES system to achieve commercial operation in decades. The European-Union-funded RICAS (adiabatic) project in Austria was to use crushed rock to store heat from the compression process to improve efficiency (2020). The system was expected to achieve 70–80% efficiency. Apex planned a plant for Anderson County, Texas , to go online in 2016. This project has been delayed until at least 2020. Canadian company Hydrostor planned to build four Advance plants in Toronto , Goderich, Angas, and Rosamond (2020). Some included partial heat storage in water, improving efficiency to 65%. As of 2022,
629-590: The US Department of Energy provided $ 29.4 million in funding to conduct preliminary work on a 150-MW salt-based project being developed by Iberdrola USA in Watkins Glen, New York . The goal is to incorporate smart grid technology to balance renewable intermittent energy sources . The first adiabatic project, a 200-megawatt facility called ADELE, was planned for construction in Germany (2013) with
666-438: The amount of stored energy that remains in this air. Consequently, if the air temperature is too low for the energy recovery process, then the air must be substantially re-heated prior to expansion in the turbine to power a generator . This reheating can be accomplished with a natural-gas -fired burner for utility -grade storage or with a heated metal mass. As recovery is often most needed when renewable sources are quiescent,
703-744: The compressed air obeys the ideal gas law : For a process from an initial state A to a final state B , with absolute temperature T = T A = T B {\displaystyle T=T_{A}=T_{B}} constant, one finds the work required for compression (negative) or done by the expansion (positive) to be where p V = p A V A = p B V B {\displaystyle pV=p_{A}V_{A}=p_{B}V_{B}} , and so V B V A = p A p B {\displaystyle {\frac {V_{B}}{V_{A}}}={\frac {p_{A}}{p_{B}}}} . Here p {\displaystyle p}
740-570: The cost of the vessel itself. A different approach consists of burying a large bag buried under several meters of sand instead of water. Plants operate on a peak-shaving daily cycle, charging at night and discharging during the day. Heating the compressed air using natural gas or geothermal heat to increase the amount of energy being extracted has been studied by the Pacific Northwest National Laboratory . Compressed-air energy storage can also be employed on
777-542: The efficiency of the storage improves considerably. There are several ways in which a CAES system can deal with heat. Air storage can be adiabatic , diabatic, isothermal , or near-isothermal. Adiabatic storage continues to store the energy produced by compression and returns it to the air as it is expanded to generate power. This is a subject of an ongoing study, with no utility-scale plants as of 2015. The theoretical efficiency of adiabatic storage approaches 100% with perfect insulation, but in practice, round trip efficiency
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#1732783416926814-399: The environment. In practice, neither of these perfect thermodynamic cycles is obtainable, as some heat losses are unavoidable, leading to a near-isothermal process. Near-isothermal compression (and expansion) is a process in which a gas is compressed in very close proximity to a large incompressible thermal mass such as a heat-absorbing and -releasing structure (HARS) or a water spray. A HARS
851-554: The first of its kind in the United States. Compressed air energy storage may be stored in undersea caves in Northern Ireland . In order to achieve a near- thermodynamically-reversible process so that most of the energy is saved in the system and can be retrieved, and losses are kept negligible, a near-reversible isothermal process or an isentropic process is desired. In an isothermal compression process,
888-499: The first systems to power clocks by sending a pulse of air every minute to change their pointer arms. They quickly evolved to deliver power to homes and industries. As of 1896, the Paris system had 2.2 MW of generation distributed at 550 kPa in 50 km of air pipes for motors in light and heavy industry. Usage was measured in cubic meters. The systems were the main source of house-delivered energy in those days and also powered
925-685: The fuel must be burned to make up for the wasted heat. This degrades the efficiency of the storage-recovery cycle. While this approach is relatively simple, the burning of fuel adds to the cost of the recovered electrical energy and compromises the ecological benefits associated with most renewable energy sources. Nevertheless, this is thus far the only system that has been implemented commercially. The McIntosh, Alabama , CAES plant requires 2.5 MJ of electricity and 1.2 MJ lower heating value (LHV) of gas for each MJ of energy output, corresponding to an energy recovery efficiency of about 27%. A General Electric 7FA 2x1 combined cycle plant, one of
962-543: The gas in the system is kept at a constant temperature throughout. This necessarily requires an exchange of heat with the gas; otherwise, the temperature would rise during charging and drop during discharge. This heat exchange can be achieved by heat exchangers (intercooling) between subsequent stages in the compressor, regulator, and tank. To avoid wasted energy, the intercoolers must be optimized for high heat transfer and low pressure drop. Smaller compressors can approximate isothermal compression even without intercooling, due to
999-558: The global shift towards renewable energy renewed interest in CAES systems, to help highly intermittent energy sources like photovoltaics and wind satisfy fluctuating electricity demands. One ongoing challenge in large-scale design is the management of thermal energy, since the compression of air leads to an unwanted temperature increase that not only reduces operational efficiency but can also lead to damage. The main difference between various architectures lies in thermal engineering. On
1036-414: The link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=CAES&oldid=1231511434 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Compressed-air energy storage Compressed-air-energy storage (CAES)
1073-579: The machines of dentists , seamstresses , printing facilities, and bakeries . The first utility-scale diabatic compressed air energy storage project was the 290-megawatt Huntorf plant opened in 1978 in Germany using a salt dome cavern with 580 MWh energy and a 42% efficiency. A 110-megawatt plant with a capacity of 26 hours (2,860 MWh energy) was built in McIntosh, Alabama in 1991. The Alabama facility's $ 65 million cost equals $ 590 per kW of capacity and about $ 23 per kW-hr of storage capacity. It uses
1110-579: The most efficient natural gas plants in operation, uses 1.85 MJ (LHV) of gas per MJ generated, a 54% thermal efficiency . Isothermal compression and expansion approaches attempt to maintain operating temperature by constant heat exchange to the environment. In a reciprocating compressor, this can be achieved by using a finned piston and low cycle speeds. Current challenges in effective heat exchangers mean that they are only practical for low power levels. The theoretical efficiency of isothermal energy storage approaches 100% for perfect heat transfer to
1147-461: The other hand, small-scale systems have long been used for propulsion of mine locomotives . Contrasted with traditional batteries, systems can store energy for longer periods of time and have less upkeep. Compression of air creates heat; the air is warmer after compression. Expansion removes heat. If no extra heat is added, the air will be much colder after expansion. If the heat generated during compression can be stored and used during expansion, then
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1184-420: The relatively high ratio of surface area to volume of the compression chamber and the resulting improvement in heat dissipation from the compressor body itself. When one obtains perfect isothermal storage (and discharge), the process is said to be "reversible". This requires that the heat transfer between the surroundings and the gas occur over an infinitesimally small temperature difference. In that case, there
1221-409: The simulated system under continuous operation was calculated to be between 70.5% and 71%. Diabatic storage dissipates much of the heat of compression with intercoolers (thus approaching isothermal compression) into the atmosphere as waste, essentially wasting the energy used to perform the work of compression. Upon removal from storage, the temperature of this compressed air is the one indicator of
1258-409: The storage vessel is positioned hundreds of meters below ground level, and the hydrostatic pressure (head) of the water column above the storage vessel maintains the pressure at the desired level. This configuration allows: On the other hand, the cost of this storage system is higher due to the need to position the storage vessel on the bottom of the chosen water reservoir (often the ocean) and due to
1295-399: The thermodynamic conditions of the storage and on the technology used: This storage system uses a chamber with specific boundaries to store large amounts of air. This means from a thermodynamic point of view that this system is a constant-volume and variable-pressure system. This causes some operational problems for the compressors and turbines, so the pressure variations have to be kept below
1332-876: The world's third such project. The project uses no fuel. It appears to have stopped operating in 2016. A 60 MW / 300 MWh facility with 60% efficiency opened in Jiangsu , China, using a salt cavern (2022). A 2.5 MW / 4 MWh compressed CO 2 facility started operating in Sardinia , Italy (2022). In 2022, Zhangjiakou connected the world's first 100-MW "advanced" system to the grid in north China. It uses no fossil fuels , instead adopting supercritical thermal storage, supercritical heat exchange, and high-load compression and expansion technologies. The plant can store 400 MWh with 70.4% efficiency. A 350 MW / 1.4 GWh underground salt cave project started construction in Shangdong at
1369-536: Was tested as a storage system, giving some good results. Obviously, the cost of the system is higher, but it can be placed wherever the designer chooses, whereas an underground system needs some particular geologic formations (salt domes, aquifers, depleted gas fields, etc.). In this case, the storage vessel is kept at constant pressure, while the gas is contained in a variable-volume vessel. Many types of storage vessels have been proposed, generally relying on liquid displacement to achieve isobaric operation. In such cases,
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