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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] 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] Rapid development of smart electronics, energy harvesting technologies are gaining tremendous attention to provide alternative energy for self-powered operations of wearable electronics, sensors, wireless networks and medical implants, followed by substantial interest from both academia and industry. In this framework, piezoelectric nanogenerator (PNG) is an energy harvesting device that converts ubiquitous mechanical energy (such as vibration, walking, body movement, keyboard typing etc.) available in our surroundings, into a faun of electrical signal based on the energy conversion by nanostructured piezoelectric materials. Thus issues associated with conventional battery systems such as limited life-span, large size, environmental pollution, compatibility and cost intensively are mitigated by harvesting solutions
[en] This paper studies the experimental and exergy analysis of solar still with the sand heat energy storage system. The cumulative yield from solar still with and without energy storage material is found to be 3.3 and 1.89 kg/m2, respectively for 8-h operation. Results show that the exergy efficiency of the system is higher with the least water depth of 0.02 m (mw = 20 kg). Competitive analysis of second law efficiency shows that the exergy efficiency improves the system by 30% than conventional single slope solar still without any heat storage. The maximum exergy efficiency with energy storage material is found as 13.2% and it is less than the conventional solar still without any material inside the basin.
[en] Full text: This paper points out one of the critical issue overlooked for fusion to become a viable energy source in the future, quantitatively analyzes the requirements, and suggests a possible solution. Future grids in possible markets and the impact of fusion introduction was analyzed with numerical model, and the limitation and requirements of the generation capacity of fusion plant is shown as the function of grid capacity, composition and stability. There are very limited opportunity of 1 GW or above for fusion in most of the emerging grids, and fusion will need smaller capacity, or better ancillary service including innovative storage. Almost all the fusion reactor designs assume large and stable electricity grids to connect and expect unlimited large pulsed power supply for starting plants. Unlike in the grids in the countries where fusion research is currently pursued, majority of the future grids where fusion would be deployed are anticipated to be significantly different. Even in the large grids in advanced countries, future system will be rather unstable because of the larger renewable fraction and trends to free electricity markets. Majority of the electric grids in the world will be still far smaller than 50 GW at the middle of this century, where introduction of fusion electricity over 1 GW would be difficult. This paper analyzes the impact of fusion electricity on small size grids. Fusion plants requires large electricity for startup, and in the case of disruption or other unexpected shut down, loss of electricity in a short time would disturb the stability of the grids. The authors established a simplified Heffron–Philips model constructed in Matlab/Simulink™. This model analyzes quantitative impacts of fusion on a given grid size and composition, and provides limits and requirements for fusion to be installed. This concept suggests the possibility of faster and easier introduction of fusion energy in the future, with reduced difficulty and with larger and more attractive market possibility. Majority of sales of fusion, if it would be viable, is in the developing countries rather than the mature markets where growth is not expected, and thus encompassing such a business model could justify the investment for fusion development. (author)
[en] In recent years lithium-ion batteries have been widely applied for portable electronic devices such as cellular phones and personal computers. Sulfones are dipolar aprotic solvents, which are used in lithium-ion batteries because of their high resistivity to electrode materials and ability to ensure high speed of electrode process. The aim of this work is the study of the local structures of LiCl in ethyl methyl sulfone (EMSO2) using quantum chemical calculations. All calculations have been carried out using the Gaussian 09 software package. Optimization of the molecular structure of isolated molecule of EMSO2 and that of the complex 1:1 LiCl:EMSO2 in their ground states in the gas phase was performed using restricted Hartree-Fock (RHF) method combined with 6-311++G(d,p) extended basis set including polarization and diffuse functions. The assignment of theoretical vibrational modes was performed by GaussView 5.0, which gives a visual representation of vibrational modes. The structural and spectral parameters of LiCl/ethyl methyl sulfone system were established. The calculations show the existence of two stable 1:1 LiCl:ethyl methyl sulfone structures and one transition state. The energy minima and transition state structure were verified by vibrational analysis. Energy minima were confirmed by the absence of imaginary vibration frequency. In the case of transition state one imaginary mode was observed. It was shown that intensity of the CH and SO stretching vibrations to the interaction between LiCl and sulfone strongly depends on the structure of the complex. The difference in spectral features is explained in the frame of vibrational Stark effect. The obtained results have been compared with those for LiCl/dimethyl sulfone and LiCl/diethyl sulfone system
[en] Highlights: • A complete set of contributions by storage in reducing system costs is analyzed. • A stochastic form of SCOPF identifies costs caused by wind variability. • Storage saves reserve cost by 48% in 2020 wind level by reducing wind variability. • Storage lowers generation cost by 2.1% in 2020 wind level by adopting more wind. • The benefit of storage capacity become larger with higher wind generation capacity. - Abstract: With the rapid increase in variable renewable sources in the power system, storage capacity is being considered as an effective solution, because its flexible charging-discharging characteristics enable the reduction of the variability of these sources. However, the value of energy storage has been estimated mostly based on arbitrage benefit, and this does not reflect the true contribution of energy storage to the power system, especially when it is integrated with high levels of wind generation. This study analyzes a more complete set of contributions made by energy storage toward reducing the total cost of supplying electricity to customers. A simulation based on a stochastic form of multi-period Security-Constrained Optimal Power Flow (SCOPF) is used to reflect the stochastic characteristics of wind resources. The results show that in addition to the arbitrage benefit, energy storage can generate an additional economic value by 1) reducing the variability of wind generation; 2) adopting more wind generation that is otherwise wasted because of high variability, and 3) lowering the peak capacity needed to meet system adequacy. Moreover, the results indicate that the benefit of energy storage is larger with higher wind generation capacity.
[en] A facile greener approach was adopted to synthesized the metal sulphide and its composite with carbon quantum dots for high performance supercapacitor application. Metal sulphides and oxides are providing high energy storage capacity due to the involvement of redox reactions in the energy storage process compared with carbonaceous materials where electrochemical double layer is primarily responsible for energy storage. The reversibility of the cycle has been optimized in the potential range from 0 V to 0.75V. The NiS/ C-dots nano structure composite exhibited high specific capacitance of 900 F/ g at the current density 2 Agt and the cyclic stability retained up to the tested cycles of 2000. Introduction of C-dots in the NiS nanostructure crystal indicated that the hybrid electrode material showed high performance of electrochemical application. (author)
[en] Energy systems are meaningful devices which are based on basic laws of physics to take energy at one end and transform it into another form with optimum efficiency. Scientists, engineers always strive to make systems more efficient and lighter. This motive acts as driving force to bring about new technologies, materials and alternative approaches. Nanofluids are that kind of materials which have revolutionized energy absorbing, transporting and storage systems. Various parameters which are cardinal in thermal performance enhancement are drastically modified when material changes into nanoform. These parameters are thermal conductivity, heat transfer coefficient, optical extinction coefficient, electrical conductivity, viscosity, density, metallic property. When materials changes its phase from bulk to nano, surface to volume ratio changes tremendously. In our experimental analysis we have chosen nanofluids (MgO+CNTs)/H2O Hybrid for evaluating performance of and flat plate solar collector for exergy efficiency, entropy generation and thermal efficiency. Exergy efficiency indicates how system is efficient to convert available energy into useful work. We have gone through preparation of nanofluid along with characterization. Experimental analysis established that at 1% volume concentration and the flow rate 21/min exergetic efficiency (second law efficiency) for (MgO+CNTs)/H2O nanofluid is enhanced by ∼28 % compare to water, ∼13% compare to MgO. Entropy generation rate, which is penalty increases insignificantly at lower concentration for MgO hybrid compare to MgO. But enhancement in exergy efficiency dominates over increment in entropy generation rate. We can conclude that nanofluid based energy transporting systems are more efficient in terms of performance and energy saving. (author)
[en] The climatic variation and deteriorating availability of fossil fuels needs to move the society towards renewable sources. The supercapacitor will become an attractive power solution to the increasing number of applications, such as renewable energy power generation, transportation, power system and many others, because of its advantages, which include high charge/discharge current capability, very high efficiency, wide temperature range, etc. Thus, supercapacitor is an emerging technology in the field of energy storage systems that can offer higher power density than batteries and higher energy density over traditional capacitors. In other words, one can say, it actually fills the gap between the batteries and conventional capacitors. Many metal oxides/ hydroxides have been studied extensively for the application of supercapacitor. The RuO2 is studied widely for sup supercapacitor, it also shows great performance as supercapacitor, but the costing and toxicity are the basic problems with this material and other oxide/ hydroxide material. Therefore, we have to move towards the alternative way, that is, cost as well as environment friendly material. The strontium hydroxide (Sr(OH)2) with tuberose dendritically branched structures has been grown successfully by successive ionic layer adsorption and reaction (SILAR) method at room temperature without using any surfactant or binder. The Sr(OH)2 film electrode exhibited the specific capacity of 413Cg-1 at 2 Ag-1 in 1 M NaOH electrolyte. The Sr(OH)2 can be emerged as a promising electrode material for supercapacitor application synthesized by low cost chemical method applicable to roll-to-roll technology, portable electronics, electric vehicles, large scale energy storage grid, etc. (author)