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[en] Highlights: ► In small-scale CAES there are no robust guidelines in choosing an operational pressure for the vessels. ► Through the stress analysis of the vessel, an optimum pressure at minimum cost can be determined. ► One contribution is in determining the optimum pressure is small-scale CAES. ► Another contribution is in determining the shape size, and number of vessels in small-scale CAES designs. - Abstract: The paper reports guidelines for the efficient design and sizing of Small-Scale Compressed Air Energy Storage (SS-CAES) pressure vessels, including guidelines for pressures that should be used in the SS-CAES system to minimize the cost of the pressure vessel. Under a specified energy storage capacity and specified maximum and minimum operating pressures in CAES, the volume of the vessel(s) can be evaluated. The present study provides guidelines for choosing appropriate shape and size for the vessels that minimize material and manufacturing cost for cylindrical vessels. The two main contributions of the paper are that it provides a methodology to determine: (a) an optimum pressure; (b) the shape, size, and number of vessel to be used in a particular application. Results suggest that pressure vessels with a length to diameter ratio of roughly three are the most economical, and that a system should be designed for a pressure of roughly three times the minimum pressure of the expansion device.
[en] Highlights: • A multi-stage AA-CAES system model is established based on thermodynamic theory. • Four Cases about pressure loss and effectiveness of heat exchanger are investigated. • The impact of pressure loss on conversion of heat energy in TES is more sensitive. • The impact of heat exchanger effectiveness in charge process on system is stronger. • Pressure loss in heat exchanger affects the change trends of system efficiency. - Abstract: Advanced Adiabatic Compressed Air Energy Storage (AA-CAES) is a large-scale energy storage system based on gas turbine technology and thermal energy storage (TES). Electrical energy can be converted into internal energy of air and heat energy in TES during the charge process, while reverse energy conversion proceeds during discharge process. The performance of AA-CAES system requires further improvement in order to increase efficiency. In this paper, a multi-stage AA-CAES system model is established, and the influence of effectiveness and pressure loss in heat exchanger on energy conversion and utilization efficiency of AA-CAES system is analyzed theoretically based on the theory of thermodynamics. Four Cases about effectiveness and pressure loss of heat exchanger are investigated and compared with each other. It is found that effectiveness and pressure loss of heat exchanger are directly related to energy conversion and utilization in AA-CAES system. System efficiency changes with the variation of heat exchanger effectiveness and the impact of pressure loss on conversion of heat energy in TES is more sensitive than that of internal energy of air. Pressure loss can cause the complexity of system efficiency change. With appropriate selection of the values of heat exchanger effectiveness for both charge and discharge processes, an AA-CAES system with a higher efficiency could be expected
[en] Highlights: • Four performance indexes of constant-sliding mode are the best. • Cooling capacity of constant-sliding mode is the strongest. • The exergy destruction of air storage chamber is the largest. • Three modes have similar variation tendencies of parameters of air storage chamber. - Abstract: The tri-generative system based on advanced adiabatic compressed air energy storage can simultaneously provide cooling energy, heating energy and mechanical energy. In order to study the discharge characteristics, three operation modes of expanders, which contain constant pressure, constant-sliding and sliding pressure, are proposed in this paper. By utilizing the numerical simulation method, the performance difference of three modes is compared with each other. The results show that four performance indexes of constant-sliding mode are all the biggest, which are respectively cycle efficiency 40.55%, thermal efficiency 80.06%, exergy efficiency 48.45% and exergy density 4.071 × 106 J·m−3, and cooling capacity of it is also the strongest, 8.386 × 109 J, among the three operation modes. Air storage chamber has the largest exergy destruction. Operation process of air storage chamber is similar for three operation modes. Meanwhile, the effects of heat exchanger effectiveness, ambient pressure and air storage chamber model on system performance are also investigated.
[en] In this study, a new compressed air energy storage (CAES) refrigeration system is proposed for electrical power load shifting application. It is a combination of a gas refrigeration cycle and a vapor compression refrigeration cycle. Thermodynamic calculations are conducted to investigate the performance of this system. Economic analysis is performed to study the operating cost of the system, and comparison is made with a vapor compression refrigeration system and an ice storage refrigeration system. The results indicate that the CAES refrigeration system has the advantages of simple structure, high efficiency and low operating cost
[en] Highlights: • CAES and CAES with thermal storage systems were investigated. • The potential for using heat generated during the compression stage was analysed. • CAES-TS has the potential to be used both as energy storage and heat source. • CAES-TS could be a useful tool for balancing overall energy demand and supply. - Abstract: The potential for using heat generated during the compression stage of a Compressed Air Energy Storage system was investigated using exergy and exergoeconomic analysis. Two Compressed Air Energy Storage systems were analysed: Compressed Air Energy Storage (CAES) and Compressed Air Energy Storage combined with Thermal Storage (CAES-TS) connected to a district heating network. The maximum output of the CAES was 100 MWe and the output of the CAES-TS was 100 MWe and 105 MWth. The study shows that 308 GW h/year of electricity and 466 GW h/year of fuel are used to generate 375 GW h/year of electricity. During the compression of air 289 GW h/year of heat is generated, which is wasted in the CAES and used for district heating in the CAES-TS system. Energy efficiency of the CAES system was around 48% and the efficiency of CAES-TS was 86%. Exergoeconomic analysis shows that the exergy cost of electricity generated in the CAES was 13.89 ¢/kW h, and the exergy cost of electricity generated in the CAES-TS was 11.20 ¢/kW h. The exergy cost of heat was 22.24 ¢/kW h in the CAES-TS system. The study shows that CAES-TS has the potential to be used both as energy storage and heat source and could be a useful tool for balancing overall energy demand and supply
[en] Future sustainable energy systems call for the introduction of integrated storage technologies. One of these technologies is compressed air energy storage (CAES). In Denmark at present, wind power meets 20% and combined heat and power production (CHP) meets 50% of the electricity demand. Based on these figures, the paper assesses the value of integrating CAES into future sustainable energy systems with even higher shares of fluctuating renewable energy sources. The evaluation is made on the basis of detailed energy system analyses in which the supply of complete national energy systems is calculated hour by hour in relation to the demands during a year. The Danish case is evaluated in a system-economic perspective by comparing the economic benefits achieved by improving the integration of wind power to the costs of the CAES technology. The result is compared to various other storage options. Furthermore, a business-economic evaluation is done by calculating the potential income of the CAES technology from both spot markets and regulating power markets. The evaluation includes both historical hour by hour prices during a 7-year period on the Nordic Nord Pool market as well as expected future price variations. The conclusion is that even in energy systems with very high shares of wind power and CHP, neither the historical nor the expected future price variations on the spot market alone can justify the investment in CAES systems. Other storage technology options are significantly more feasible. CAES may operate both on the spot market and the regulating power market, which indicates potential feasibility. However, such strategy is highly risky because of the small extent of the regulating power market and if CAES is to become feasible it will depend on incomes from auxiliary services. (author)
[en] Highlights: • Design procedure of an aquifer compressed air energy storage system was proposed. • An approach to select aquifers with adequate permeability was presented. • Applied an exergy analysis to exam the impact of permeability on plant economics. • The exergy destruction in the aquifer was reduced as the permeability increased. - Abstract: Economic, large-scale energy storage technology plays a key role in enabling the utility industry to integrate more renewable energy sources into the grid. Compressed air energy storage in porous geological formations has the potential to become one of the principal energy storage technologies in the future. Storing pressurized air in aquifers has several advantages, including large storage capacity, geologically widespread availability, relatively constant pressure, and relatively low construction cost. The performance of a compressed air energy storage plant is influenced by the subsurface reservoir properties. In this paper, the design criteria, calculation procedure, and exergy analysis approach to quantify the influence of aquifer permeability on compressed air energy storage plants are proposed. A case-study model was built to simulate a compressed air energy storage plant using aquifers with porosities of 30% and different permeabilities (0.01–1.0 darcies). The exergy destruction rates and exergy and thermal efficiencies were calculated. The results indicated that as the permeability increased, the exergy destruction due to a pressure drop of working fluid in an aquifer decreased; as the permeability increased, both thermal and exergy efficiencies increased, and the net output of the plant increased. The benefits are more obvious when the permeability increased from low (⩽0.05 darcies) to medium–high values (⩾0.25 darcies)
[en] Highlights: • A “quasi dynamic iterative searching” is proposed in turbine dynamic modelling. • A simulation platform is built to synchronise multiple time scale dynamic responses. • Low-temperature system dynamic characteristics is extensively investigated. • Effects of heat exchangers’ thermal inertias on system dynamics are analysed. - Abstract: It is challenging to gain insight of a Compressed Air Energy Storage (CAES) system dynamic behaviour under various operation conditions due to its complexity with mixed mechanical, thermal, chemical and electrical processes in one. Although a number of studies are reported on CAES steady state and dynamic modelling to reveal its characteristics, few studies have been reported in whole CAES system dynamic modelling involving a radial turbine. This paper explores a new method to analyse the transient performance of the radial turbine while it is integrated with whole low temperature Adiabatic-CAES system. The proposed modelling method approximates the average air flow within single stator/rotor stage. By applying the principle of energy and torque balance on the transmission shaft, the dynamic speed-torque characteristics of the turbine is obtained with a “quasi dynamic iterative searching” process. The model is then integrated to a simulation platform, which is created to synchronise the wide range of time scale dynamic responses including heat transfer, mechanical and electrical energy conversion processes. As every component of the low temperature adiabatic CAES system is built on its fundamental physical and engineering principles, the model is capable of revealing the system transient characteristics. Based on the model, various simulation studies are conducted and the results are compared with the operation data from the literature. It provides a valuable tool for preliminary design of a radial turbine to test its suitability in full and partial load operation conditions, and analyse its transient behaviours.
[en] Highlights: • Mode 4 has the highest exergy efficiency. • Mode 2 has the largest exergy density. • Second heat exchanger has the largest exergy destruction. - Abstract: Advanced adiabatic compressed air energy storage system plays an important role in smoothing out the fluctuated power from renewable energy. Under different operation modes of charge-discharge process, thermodynamic behavior of system will vary. In order to optimize system performance, four operation modes of charge-discharge process are proposed in this paper. The performance difference of four modes is compared with each other based on energy analysis and exergy analysis. The results show that exergy efficiency of mode 4 is the highest, 55.71%, and exergy density of mode 2 is the largest, 8.09 × 106 J m−3, when design parameters of system are identical. The second heat exchanger has the most improvement potential in elevating system performance. In addition, a parametric analysis and multi-objective optimization are also carried out to assess the effects of several key parameters on system performance.
[en] Highlights: • A grid-connected CCHP system with CAES and hybrid refrigeration is proposed. • A multi-objective assessment and optimization is presented. • Each component capacity of the CCHP system is determined by optimization. • A sensitivity analysis is conducted by the key parameters of the system. • Performance comparison with conventional CCHP system has been done. - Abstract: As one of attractive technology of energy conservation, combined cooling, heating and power (CCHP) system has brought about widespread attention. However, the variability of users demand has limited the application of CCHP system. To ensure stable and efficient operation, the compressed air energy storage is considered to be integrated with CCHP system. A grid-connected CCHP system with compressed air energy storage (CAES) and hybrid refrigeration is proposed in this paper. The power from grid is stored in CAES at off-peak time and released at on-peak time. The hybrid refrigeration system including LiBr absorption chiller and electric compression refrigerator provides cooling load to users. A multi-objective assessment and optimization synthetically considering energy, economy and environment are presented. The multi-objective indicator used as objective function to optimize each component capacity of the proposed CCHP system. A sensitive analysis of key parameters and performance comparison with conventional CCHP system have been carried out. The results shows that when the capacity of gas turbine is 691 kW, the comprehensive performance of the proposed CCHP system is the optimal performance. The power price, natural gas price, compression ratio and turbine inlet temperature of CAES have great influence on the performance of the proposed CCHP system. Meanwhile, the multi-objective indicator’s value of the proposed CCHP system is more than conventional CCHP system 4.85%.