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[en] Highlights: •Investigated CAES + HPT system concept for offshore wind energy; •Validated cost model for offshore wind farm including CAPEX and OPEX items; •Quantified cost-of-rated-power savings associated with CAES + HPT concept; •Estimated savings of 21.6% with CAES + HPT for a sample $2.92 billion project. -- Abstract: The size and number of off-shore wind turbines over the next decade is expected to rapidly increase due to the high wind energy potential and the ability of such farms to provide utility-scale energy. In this future, inexpensive and efficient on-site wind energy storage can be critical to address short-time (hourly) mismatches between wind supply and energy demand. This study investigates a compressed air energy storage (CAES) and hydraulic power transmission (HPT) system concept. To assess cost impact, the NREL Cost and Scaling Model was modified to improve accuracy and robustness for offshore wind farms with large turbines. Special attention was paid to the support structure, installation, electrical interface and connections, land leasing, and operations and maintenance cost items as well as specific increased/reduced costs reductions associated with CAES + HPT systems. This cost model was validated and applied to a sample $2.92 billion project Virginia Offshore case It was found that adaption of CAES + HPT can lead to a substantial savings of 21.6% of this 20-year lifetime cost by dramatically reducing capital and operating cost of the generator and power transmission components. However, there are several additional variables that can impact the off-shore energy policy and planning for this new CAES + HPT concept. Furthermore, these cost-savings are only first-order estimates based on linear mass-cost relationships, and thus detailed engineering and economic analysis are recommended.
[en] Over the last two decades, Pakistan’s energy demand has grown exponentially with very diminutive measures taken by the government to fulfill the needs. The large power plant projects are cumbersome, take years to be completed and require plenty of time to get fully operational. The idea of distributed generation works well in this case. Renewable energy comes well into play when we talk about distributed generation but the dependability of renewable energy resources on back-up such as batteries makes them unappealing. The objective of this paper is to practically implement a backup for the renewable energy resources using a mechanical storage such as CAES (Compressed Air Energy System). The proposed model is a composite technology, which comprises of EES (Electrical Energy Storage) and electrical power supply system. Solar energy driven compressor is used to compress the air in a storage tank, which is used on demand to drive the generator coupled air turbine. The fact that the developed system is solar powered, no other fuel is used with air and it uses mechanical storage instead of conventional storage like batteries, which makes the developed prototype system efficient, economical and durable as compared to the existing CAES. This paper focuses on the thermodynamic investigation, design and finally implementing a prototype CAES for a small load as an un-interrupted power supply system. (author)
[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] Highlights: •A concise analytical solution for SC-CAES system was presented for the first time. •The analytical solution is universal for SC-CAES and other similar CAES systems. •A method of sectional treatment and Taylor expansion was carried out. •Exergy analysis for SC-CAES system with its analytical model was conducted. -- Abstract: An analytical solution for a novel Compressed Air Energy Storage (CAES) system, Supercritical Compressed Air Energy Storage (SC-CAES) system, was conducted in this paper. The analytical solution can explore the evolution and its reason of roundtrip efficiency varying with system key parameters in depth, while it can also reveal the coupling mechanism of different sections of the system. On that basis, the model of exergy destruction for each part was obtained, and the exergy destruction can be easily calculated. Furthermore, the analytical solution has the character of universality due to the deduced method of sectional treatment, hence it can be extended to other similar CAES systems. Lastly, a sensitivity analysis and an exergy analysis were conducted for SC-CAES system. It is found and proved that the system efficiency varies linearly with isentropic efficiencies of compressor and expander, temperature difference of intercooler and reheater, pressure loss of intercooler and reheater. Meanwhile, the main factors of the varying tendency of total exergy destruction with different parameters are revealed.
[en] This document describes the main characteristics of various electric power storage methods and their application domains. The large-scale storages include the hydraulic systems, those using compressed air, the batteries or those implementing a thermal way. The small-scale storages are electrochemical as the accumulators, the super-capacitors, mechanical as the flywheel, magnetic or also by the hydrogen use. The first part presents the necessity of the electric power storage, the second part the places of these storage. The third part details the forms of storage. (A.L.B.)
[en] This article examines how the ability to ''store'' electricity can pay handsome dividends in a competitive environment. Priorities change when industries are deregulated. Indeed, new priorities are being established for electric generation--low cost, efficiency, product distinction for marketing purposes, etc. are all more critical today. Perhaps not so obvious is the fundamental role of energy storage in a fully competitive marketplace. In fact, rarely do a technology development and a changing business climate play off against each other so nicely. Consider the function of the emerging electricity broker, or power marketer. Imagine the premium that broker could command with access to a large increment of electricity--purchased at a low price--and supplied at a moment's notice for a substantially higher price. Storage of electricity would mean that the investment in excess available generation capacity to supply so-called peak demand could be avoided. It also means that electricity could be brokered like other commodities--that is purchased, stockpiled, and sold to reflect market conditions across a wider geographical region and time spain. Benefits accrue to transmission and distribution, in addition to generation. Energy storage helps to manage the increasing stress placed on the grid as a result of intermittent sources of power and large numbers of cogenerators and small power producers. On the customer side, any ratepayer large or small could, theoretically, play the spot market in electric supply with a reserve to tap in emergencies. For a parallel in other deregulated markets, recall how storage has become an important factor in natural-gas contracting. Quality of electricity also can be improved by applying storage to stabilize the grid, especially along the distribution system at substations. And the opening of vast markets for electricity consumption, such as electric vehicles, depends in large measure on electric storage
[en] Carbon dioxide is main green house gas, and it has been increased greatly in the atmosphere since the industrial revolution. The human living environment has been worsened with more and more carbon dioxide in the air. In this paper, the authors analyzed the physical property of carbon dioxide and green house gas effect, then studied the disposal measures for carbon dioxide. At last it was pointed out that various measures should be taken to carry out the carbon dioxide disposal, more economic benefit can be anticipated along with carbon dioxide disposal by EOR, CO_2-ECBM, CAES, et al, of which CO_2-ECBM is one of the way with best benefits. (authors)
[en] The fight against climate change requires harnessing novel technologies to decrease CO2 emissions. Renewable energy must be among the main strategies for complying with the COP-21 agreements. Energy storage technologies will play a crucial role in increasing the efficiency and availability of this kind of energy source. Moreover, energy storage technologies will help reduce the supply risk of the electric power system, by overcoming the uncertainty of renewable energy generation. Compressed air energy storage (CAES) enables large amounts of energy to be accumulated reliably. Although there are different structures in the subsurface that may be considered for this purpose, the development of CAES in a salt dome offers several technical and economic advantages. Furthermore, currently this kind of structure is the only one used for this purpose on an industrial scale. In order to reduce the inherent risk associated with the definition and selection of subsurface structures, this study proposes a multi-criteria algorithm based on the Analytic Hierarchy Process methodology. In this scenario, the algorithm focuses on the process to rank salt domes for CAES development. The study applies this methodology in the Basque–Cantabrian basin, where as many as eleven structures have been examined.
[en] Electricity storage (ES) has the potential of offering several energy system benefits but different technologies also offer different services which can be traded on different markets. In this study, a combined assessment methodology is proposed, enabling a benchmark comparison of stationary electricity storage technologies for different time and system scales, considering their technical, economic and environmental performance. The results show that for short time scale (0.01 h), battery stands out with an advantage in terms of levelised costs, while Advanced Adiabatic (AA-) and Isothermal (I-) Compressed Air Energy Storage (CAES) have relatively low life cycle Greenhouse Gas (GHG) emissions. For the medium time scale (4.5 h), I-CAES shows the best performance for small scale systems, while for large scale systems, Pumped Hydro Storage (PHS) and AA-CAES show best performance. In our long time scale (seasonal) scenario, Power-to-gas-to-power (P2G2P) has lower levelised costs due to low or avoided investment for storage of gas, but higher GHG emissions than other technologies. If existing reservoirs can be utilized for PHS, it can be economically competitive to P2G2P for seasonal storage. However, storage capacity required for seasonal storage should also be taken into account, for which P2G2P has more flexibility. - Highlights: • Stationary electricity storage assessment combining techno-economic and life cycle assessment. • Current and future performance variations, type and price of electricity stored were considered. • Performances of storages were investigated under different time- and system-scales. • Storage technologies perform quite differently based on applications and the electricity stored. • Recommendations were made in terms of preference of technologies for different applications.
[en] A simulation model consisting of wind speed, wind turbine and AA-CAES (advanced adiabatic compressed air energy storage) system is developed in this paper, and thermodynamic analysis on energy conversion and transfer in hybrid system is carried out. The impacts of stable wind speed and unstable wind speed on the hybrid system are analyzed and compared from the viewpoint of energy conversion and system efficiency. Besides, energy conversion relationship between wind turbine and AA-CAES system is investigated on the basis of process analysis. The results show that there are several different forms of energy in hybrid system, which have distinct conversion relationship. As to wind turbine, power coefficient determines wind energy utilization efficiency, and in AA-CAES system, it is compressor efficiency that mainly affects energy conversion efficiencies of other components. The strength and fluctuation of wind speed have a direct impact on energy conversion efficiencies of components of hybrid system, and within proper wind speed scope, the maximum of system efficiency could be expected. - Highlights: • A hybrid system consisting of wind, wind turbine and AA-CAES system is established. • Energy conversion in hybrid system with stable and unstable wind speed is analyzed. • Maximum efficiency of hybrid system can be reached within proper wind speed scope. • Thermal energy change in hybrid system is more sensitive to wind speed change. • Compressor efficiency can affect other efficiencies in AA-CAES system