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[en] Phase change material (PCM) can store large amount of thermal energy at phase change temperature. Determination of thermophysical properties of PCM plays an important role in estimation of energy stored or released in storage device. Properties of PCM are key factors for designing a latent heat thermal energy storage system. This paper deals with the study of effect of heating/cooling rate on thermophysical properties, especially on melting temperature and latent heat of fusion /solidification. Results indicate that latent heat of fusion has more dependence on heating/cooling rate than onset, peak and end temperature. (author)
[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] 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] A brief overview is given of the research activities of the Dutch association for energy distribution companies EnergieNed in the field of energy storage techniques, carried out within the framework of the long-range programme Study and Research (MSO, abbreviated in Dutch)
[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] 1. The effects of large scale electrical energy storage on the introduction of alternative energy sources (solar, wind) may depend on the following factors: a) The composition and utilization of the existing power plants. b) Types of locally available rate of electricity demand. c) The need for intermediate size stand alone facilities. 2. The storage may act as a deterrent to the introduction of alternative energies if there exists a large under utilized capacity of efficient base load plants. It may however facilitate the introduction of alternatives, where no large excess of this kind exists, and the predicted expansion rate may justify small scale modular addition of production and storage capacity. Availability of storage may facilitate deployment of alternatives in remote areas, in preference to long transmission lines. This may depend on favorable patterns of time correlation between availability of wind and solar solar energy on appropriate time scales: daily, weekly, local synoptic and seasonal. 3. Some of the electricity storage devices are associated with heat dissipation at useful temperatures (CAES, batteries, fuel cells). This creates a heat disposal problem, and at the same time, an opportunity for its utilization in association with the daily and seasonal heat storage. (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] Several electrochemical energy storage batteries are under development for bulk energy storage. These batteries are often characterized by their low power density, but are attractive as stationary storage devices for load leveling and solar applications because of their potentially low cost. 17 refs
[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)