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[en] Highlights: • A single energy storage can always be split into two hybrid energy storages. • These hybrid storages have the same total energy and power as the single storage. • The potential for storage hybridisation depends on the shape of the power profile. • A higher potential allows a higher spread of the power/energy-ratios of the storages. • Automobile and pulsed power applications are well suited for storage hybridisation. - Abstract: Aim of a storage hybridisation is a beneficial usage or combination of different storage technologies with various characteristics to downsize the overall system, decrease the costs or to increase the lifetime, system efficiency or performance. In this paper, the point of interest is a different ratio of power to energy (specific power) of two storages to create a hybrid energy storage system (HESS) with a resulting specific power that better matches the requirements of the application. The approach enables a downsizing of the overall system compared to a single storage system and consequently decreases costs. The paper presents a theoretical and analytical benchmark calculation that determines the maximum achievable hybridisation, i.e. possible spread in specific power, while retaining the original total energy and power capacities of an equivalent single storage system. The theory is independent from technology, topology, control strategy, and application and provides a unified view on hybrid energy storage systems. It serves as a pre-dimensioning tool and first step within a larger design process. Furthermore, it presents a general approach to choose storage combinations and to characterize the potential of an application for hybridisation. In this context, a Hybridisation Diagram is proposed and integral Hybridisation Parameters are introduced.
[en] The significance of nuclear energy is increasing because it has the potential to solve a number of problems concerned with shortages of fuels and environmental degradation in the 21st century. Therefore the uses of nuclear power should be widened so that it can be used as a source of heat energy as well as just being used for electrical generation. A concept for utilizing nuclear energy effectively has been studied for an electric power company. A new electric energy storage system has been proposed which stores power by producing a synthetic fuel, methanol. The methanol is made from coal gas and hydrogen which is produced by excess off-peak electricity and high temperature heat from a HTGR. The system is not only technically feasible, but is also cost-competitive with other storage systems. (author)
[en] We give a detailed description of the energy balance equation for a stand-alone hybrid solar–wind power generating system. The dimensions of the power generator and the energy capacity of a buffer battery (used as an energy storage system) are chosen to suit a known consumer's profile. Future applications of the mathematical model developed and analogies with a similar hydrodynamic problem are discussed. (paper)
[en] Highlights: ► Super-capacitors are used to store regenerative braking energy in a metro network. ► A novel approach is proposed to model easily and accurately the metro network. ► An efficient approach is proposed to calculate the required super-capacitors. ► Maximum energy saving is around 44% at off-peak period and 42% at peak period. ► Benefit/cost analyses are performed for the suggested ESS. - Abstract: In this paper, the stationary super-capacitors are used to store a metro network regenerative braking energy. In order to estimate the required energy storage systems (ESSs), line 3 of Tehran metro network is modeled through a novel approach, in peak and off-peak conditions based on the real data obtained from Tehran metro office. A useful method is proposed to predict the maximum instantaneous regenerative energy which is delivered to each station before applying ESS and based on that the ESS configuration for each station is determined. Finally, the effectiveness of the proposed ESS is confirmed by economic evaluations and benefit/cost analyses on line 3 of Tehran metro network.
[en] Highlights: ► PV systems with sun tracking and concentrators (CPVS) can reduce the cost of energy per kWh produced. ► The V-trough low-concentration system solution is compatible with flat PV module technologies. ► Optical, thermal and electrical models are needed to forecast real power production. ► The description of a PV grid connected system with batteries, a one-axis tracker and CPV photovoltaic system is presented. ► Outdoor measurements of the generating system are provided and discussed. - Abstract: Photovoltaic systems (PVSs) combined with either some form of storage, such as a battery energy storage system (BESS), or direct load control, can play a crucial role in achieving a more economical operation of the electric utility system while enhancing its reliability with additional energy sources. At the same time, it is also important to use cost-effective PV solutions. In this context, a low-concentration PVS (CPVS) is analysed as a feasible alternative. This paper, present a case study of a complex PVS, composed of two PVSs, a storage system (BEES) and an inverter that allows the system to operate in both the island and grid-connected modes. The first PVS, is a 2.76-kWp single-axis tracking system (azimuth) with modules facing south and tilted 30°, while the second PVS is a dual-axis tracking system, rated 860 Wp, consisting of a concentrator at the flat mirrors (DoubleSun® Four). The system is installed on the roof of the main building of the “ITIS Marconi” school (Italy). A detailed description of the system is provided, and preliminary operating data are presented and discussed. The efficiencies of the PV systems are calculated and measured to evaluate the cost effectiveness of a low-concentration system.
[en] Highlights: • An optimal planning model for DESSs in SOP-based active distribution networks is proposed. • The power flow controllability of SOP is modeled and optimally coordinated with DESS operation. • Inverter-based DG reactive power capability and short-term network reconfiguration at the hourly timescale are incorporated in the planning. • The proposed DESS planning model is formulated as a computationally efficient MISOCP problem. - Abstract: The integration of high-penetration distributed generators (DGs) with smart inverters and the emerging power electronics technology of soft open points provide increased controllability and flexibility to the operation of active distribution networks. Existing works on distributed energy storage planning have not fully considered the coordinated operation of these new power electronic devices with distributed energy storage systems, leading to less economic investment decisions. This paper proposes an optimal planning model of distributed energy storage systems in active distribution networks incorporating soft open points and reactive power capability of DGs. The reactive power capability of DG inverters and on load tap changers are considered in the Volt/VAR control. Moreover, soft open points are modeled to provide flexible active and reactive power control on the associated feeders. Hourly network reconfiguration is conducted to optimize the power flow by changing the network topology. A mixed-integer second-order cone programming model is formulated to optimally determine the locations and energy/power capacities of distributed energy storage systems. Finally, the effectiveness of the proposed model is validated on a modified IEEE 33-node distribution network. Considering soft open points, DG reactive power capability, and network reconfiguration, the results demonstrate the optimal distributed energy storage systems planning obtained by the proposed model achieves better economic solution.
[en] Highlights: • A review of power converter interfaces for electrochemical energy storage (EES) system is presented. • EES devices and their specificities regarding to integration with the electrical systems are also described. • Power converters are divided into standard, multilevel and multiport technology. • The smart storage concept and the interface requirements to integrate the EES devices are also reviewed. - Abstract: Energy storage concept that supports important technologies for electrical systems is well established and widely recognized. Several energy storage techniques are available, including an electrochemical energy storage system used to support electrical systems. These storage systems require interfaces based on power electronic converters for interconnection with an electrical system. This paper reviews the literature covering the various types of interfaces developed for electrochemical energy storage systems. Different electrochemical energy storage devices and their specificities regarding to integration with the electrical systems are described. . The various power converter interfaces that can be used for electrochemical energy storage systems are presented. These interfaces have been divided into standard, multilevel and multiport technology. The main characteristics and specificity of each topology considering its application to electrochemical energy storage systems are presented. The review also covers the smart storage concept and the requirements of the interface to integrate the electrochemical energy storage devices upon this concept
[en] The Dutch distribution companies are organised in the umbrella organization 'EnergieNed'. Amongst economics, environmental issues, marketing and legal issues, EnergieNed controls a research program. Part of this program is the energy storage program. Main task of the distribution companies is to supply the end-user with electricity, at the contracted price and quality. Storage might be a tool to achieve this. (author)
[en] The EPSRC operates a number of research programmes relevant to the proceedings of EESAT'98; in particular the Energy Storage and Recovery Programme, which in 1998 has funded seven new projects totalling approximately Pound 1.5 million. For the foreseeable future, energy storage research will be funded through a major new activity in Renewables and new energy technologies. This paper gives the background to the Energy Storage and Recovery Programme, the thinking behind the new activity, and lists the projects funded. (author)
[en] Highlights: • An automated search for reaction systems suitable for thermochemical energy storage was performed. • Algorithm to build reaction systems for thermochemical energy storage is presented. • Close to 1000 possible reaction systems for 5 different reactive gases were found. • The VIENNA TCES-database for thermochemical energy storage materials is presented. - Abstract: Thermochemical energy storage (TCES) is considered as an emerging green technology for increased energy utilization efficiency, thereby achieving a reduction of greenhouse gases. Various reaction systems based on different substance classes (e.g. hydrates, hydroxides, oxides) were suggested and investigated so far. Nevertheless, the number of know reactions which are suitable is still limited, as the main focus concentrates on the investigation of a handful known substances, their further improvement or applicability. To find novel promising candidates for thermochemical energy storage and also to allow for a broader view on the topic, this work present a systematic search approach for thermochemical storage reactions based on chemical databases. A mathematical search algorithm identifies potential reactions categorized by the reactant necessary for the reaction cycle and ranked by storage density. These candidates are listed in the online available VIENNA TCES-database, combined with experimental results, assessing the suitability of these reactions regarding of e.g. decomposition/recombination temperature, reversibility, cycle stability, etc.