Results 11 - 20 of 163
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[en] Analytical solutions of the linearized governing equation are presented for periodic gas flow around a well in porous media. Two cases are considered: a fully penetrating well and a partially penetrating well. For the first case, a closed form solution is obtained, whereas for the second case the solution is in the form of eigenfunctions expansions. The results have practical application in compressed air energy storage. (authors)
[en] In order to resolve the problems arising from the fact that the production and consumption of electricity are at distinctly levels through much of the day, the electric power companies have been led to adopt different solutions, from the financial inducements to customers to limit their use of appliances, to the design of electric power stations with daily or weekly compressed air energy storage. Faced with fluctuating energy demand situation, the electric power companies are developing an electric base load, produced by basic power stations, hydroelectric (river) stations, nuclear and steam stations. They respond to the fluctuation of demand by starting up stations powered by fuel-oil by more or less sophisticated gas turbine, by hydroelectric energy, or as at Huntorf, by pneumatic stored energy. In this communication, we present the results, the capital cost and the operating cost concerning the combination of pneumatic storage with reciprocating engine and gas turbine. (author)
[en] Experience in optimal synthesis of individual vehicle components and mechanisms on the basis of additive technology is analyzed. A list of basic additive technologies is presented. The benefits of additive technology in combination with three-dimensional computer simulation are noted. The possibility of visualizing CAE calculations by means of additive technology is considered. In addition, the role of additive technology in the manufacture of individual vehicle components and mechanisms is discussed.
[en] The major types of energy storage systems (including conventional batteries, compressed air energy storage, pumped hydro and superconducting coils) are discussed in this paper. 8 bibliographies
[en] Highlights: • Thermodynamic analysis is presented for an improved A-CAES combined with PBTES system. • A mathematic model is developed, validated and used to simulate system performances. • PBTES heights have significant influence on the PBTES’s thermal behaviors and the system efficiencies. • The maximum cycle efficiency of the improved A-CAES system is 56.74%. - Abstract: Energy storage technology is a cutting-edge research in the field of new and renewable energy application. In this paper we introduce the concept of an energy storage based on adiabatic compressed air energy storage (A-CAES) combined with packed bed thermal energy storage (PBTES) system. First, the system thermodynamic performance of a typical single cycle is discussed and the effect of PBTES heights is analyzed. The results show that an overall efficiency in excess of 49% is achievable and the PBTES heights have significant influence on the thermal behavior of PBTES, as well as the overall efficiencies. Because there is still heat energy remaining in the packed bed until the discharge process is terminated, an improved A-CAES system with a heat recuperator is further proposed. It is found that this improved system shows a promotion of ∼5% compared with the first present A-CAES system. The cycle efficiency of the improved system increases with the increase of continuous cycles, and then reaches a stable value of 56.74% after around 25 cycles. The main conclusions drawn from this work will be helpful for future development of a high-efficiency A-CAES system combined with PBTES.
[en] Highlights: • A wellbore-reservoir coupled model is developed based on Huntorf CAES plant. • Performance of CAESA can be similar to or even better than CAESC. • The temperature of CAESA shows a smooth variation due to large grain specific heat. • The impact of initial gas bubble volume on the storage efficiency is not significant. • Boundary permeability of the reservoir can significantly affect total storage efficiency. - Abstract: CAESA (compressed air energy storage in aquifers) attracts more and more attention as the increase need of large scale energy storage. The compassion of CAESA and CAESC (compressed air energy storage in caverns) can help on understanding the performance of CAESA, since there is no on running CAESA project. In order to investigate the detail thermodynamic process, integrated wellbore-reservoir (cavern or aquifer) simulations of CAES (compressed air energy storage) are carried out based on parameters of the Huntorf CAES plant. Reasonable matches between monitored data and simulated results are obtained for the Huntorf cavern systems in the wellbore and cavern regions. In this study, the hydrodynamic and thermodynamic behaviors of CAES in cavern and aquifer systems are investigated, such as pressure and temperature distribution and variation in both the wellbore and cavern regions of the CAES systems. Performances of CAESA are investigated with numerical models and compared with the performances of CAESC. The comparisons of CAESC and CAESA indicate that the pressure variation in CAESA shows a wider variation range than that in CAESC, while the temperature shows a smooth variation due to the large grain specific heat of the grains in the porous media. The simulation results confirm that the CAES can be achieved in aquifers, and further that the performance of energy storage in aquifers can be similar to or better than CAESC, if the aquifers have appropriate reservoir properties, which means the gas bubble can be well developed in an aquifer with such properties and the aquifer should have closed or semi-closed boundaries. The impacts of gas-bubble volume, formation permeability, and aquifer boundary permeability on storage efficiency are investigated and the simulation results indicate that the increase of gas bubble volume and permeability can improve the efficiency, but the effect is not significant. The gas bubble boundary permeability has a small effect on the energy efficiency of the sustainable daily cycle but can significantly affect total sustainable cycle times. The analysis of thermodynamic behaviors in CAESA suggests that more attention should be paid to the heat storage, reservoir properties and two-phase flow processes.
[en] The low efficiency of existing CAES systems is due to large energy losses during the air compression process. This could be remedied by building an adiabatic CAES system, where the heat of compression is stored and subsequently used during the expansion process in the turbine. An energy and exergy analysis of A-CAES is presented in this article. A dynamic mathematical model of an adiabatic CAES system was constructed using Aspen Hysys software. The volume of the CAES cavern is 310000 m3 and the operation pressure inside the cavern ranges from 43 to 70 bar. Thermal oil was used as the working medium in thermal energy storage system. The temperature in the hot oil tank was 300 °C and in the cold oil tank 80 °C. Simulations of processes of loading and unloading of compressed air storage were performed and then places where exergy destruction occurs were identified. The biggest exergy destruction occurs in the compressors (276.191 MWh/cycle in total) and turbines (190.394 MWh/cycle in total). Major destruction of exergy was also reported at control valve V2 (103.688 MWh/cycle). Round trip efficiency of the system is 50%. - Highlights: • An adiabatic compressed air energy storage system using thermal oil is proposed. • Analysis of energy efficiency of adiabatic CAES was presented. • Exergy destruction and exergy losses have been pointed out.
[en] This paper presents a framework for optimally allocating storage technologies in a power system. This decision support tool helps in quantitatively answering the questions on “where to and how much to install” considering the profits from arbitrage opportunities in a co-optimized electricity market. The developed framework is illustrated on a modified IEEE (Institute of Electrical and Electronics Engineers) 24 bus RTS (Reliability Test System), and the framework finds the optimal allocation solution and the revenues storage earns at each of these locations. Bulk energy storage, CAES (compressed air energy storage) is used as the representative storage technology, and the benefits of optimally allocated storage integration onto the grid are compared with transmission expansion solution. The paper also discusses about system-level indicators to identify candidate locations for economical storage ventures, which are derived based on the optimal storage allocation solution; and applies the market price based storage venture indicators on MISO (Mid-continental Independent System Operator) and PJM (Pennsylvania-New Jersey-Maryland Interconnection) electricity markets. - Highlights: • Storage optimal allocation framework based on high-fidelity storage dispatch model. • Storage with transmission addresses energy and ancillary issues under high renewables. • Bulk storage earns higher revenues from co-optimization (∼10× energy only market). • Grid offers distributed opportunities for investing in a strategic mix of storage. • Storage opportunities depend on cross-arbitrage, as seen from MISO (Mid-continental Independent System Operator) and PJM (Pennsylvania-New Jersey-Maryland Interconnection) markets