The SB-7700 balancing monitor was used to carry out the online balancing experiment on the rotor-bearing unit of the flywheel energy storage system. The additional balance process flywheel was designed according to the balancing test results. The flywheel rotor-bearing system arrived at the rated speed of 3600 r/min after the rotor-bearing unit was balanced by the two-plane balancing method. The vibration monitor measurement showed that the vibration expressed some difference between the charging and discharging state. The discharging power rate had great impact on the amplitude-frequency performance at the resonance of the rotor-bearing unit. This was caused by the bias electrical-magnetic force of the permanent motor.

To achieve a high specific energy density, a metal rotor without a shaft is designed to consists of a hollow hub and three composite cylindrical rings fitted in interference. A mathematical model is formulated for the stress distribution using a simplified two dimensional stress model. Optimization is carried out by using the total storage energy density as the objective function and the thickness of the composite rings and the interference value between rings as the variables. It is found that the optimization increases the upper limit of the rotor speed from 50000 r/min to 57797 r/min, and the corresponding total storage energy capacity increases by 34.5%, from 1147 W·h to 1543 W·h.

Low melting point alloys are potential phase change thermal storage materials and heat transfer agent due to its excellent property such as high thermal conductivity coefficient, high thermal storage density, excellent thermal stability, low melting point and high boiling point. This paper review the phase change thermal storage low melting point alloys based on its thermo-physical properties such as phase change temperature, phase change latent, coefficient of thermal conductivity and stabilization. The steam pressure, interfacial force, viscosity and capacity of heat are introduced to explore the application of low melting point alloy in heat transfer materials. The high temperature corrosion behaviors of low melting point alloy are also introduced. And finally, the future work about the thermal storage and heat transfer low melting point alloys are prospected.

The earth is rich in diatomite resources. Such type of materials has a high porosity and favorable structural and thermophysical properties, and can therefore serve as the structural material for composite phase change materials. In this article, we first briefly introduces the structure and properties of diatomite, we then provide a state-of-the-art review on the use of the diatomite as the structural material for encapsulating phase change materials for thermal energy storage applications. Finally, further development in the area is discussed.

Flywheel energy storage systems (FESS) store energy in a rotating mass. The advantages of such systems includes high power density, environmental friendliness, long lifespan, wide operating temperature range, and very long charge-discharge cycle life. FESS has therefore been widely used in numerous applications. Integrating multiple flywheel energy storage units to form a flywheel array energy storage system (FAESS) provides a mean for large scale energy storage. In this paper, an overview of the current development status and key technologies of FAESS is given. Design method, parallel topology and control strategy of FAESS are then presented. With enhanced control technologies for parallel operation of flywheel energy storage units, FAESS could be used for grid frequency regulation particularly for dealing with intermittent renewable energy generation.

Output power of a grid-connected photovoltaic power generation system is often random and fluctuant. This is harmful to the stability of the power system,the photovoltaic power consumption and power quality,and therefore restricts the development of PV generation. To address these issues,supercapacitors were adopted as a power regulating device. This controls the grid-connected photovoltaic system to enable output power according to a preset condition in a smooth and stable manner. In this paper, an analysis is done on the supercapacitor characteristics,system structure and small-signal model of the bi-directional DC / DC converter. Based on the analysis, a strategy is put forward for power and current double closed-loop with feedback hysteresis current control. Finally, simulations are carried out in the PSCAD / EMTDC environment and the results and the results suggest the feasibility of the method.

Graphite (GP) based composite electrodes containing multi-walled carbon nanotube (MWCNT) were prepared for vanadium redox flow batteries (VRFB) using polytetrafluoroethylene (PTFE) as binding agent. Electrochemical performance of the GP-MWCNT composite electrodes was characterized by chronoamperometry, cyclic voltammetry and electrochemical impedance spectroscopy. The results showed that both positive and negative electrode reactions of VRFB benefited from the use of more MWCNT in the composite electrode, and the best electrochemical performance was obtained with pure MWCNT electrode. A VRFB was therefore constructed using pure MWCNT electrodes as both the positive and negative electrodes. Preliminary charge/discharge tests at a current density of 30 mA/cm² demonstrated that the VRFB had a good stability and electrochemical performance. The current efficiency, voltage efficiency and energy efficiency were 96%, 87% and 84%, respectively.

Renewable energies, such as solar and wind power, are increasingly being introduced as alternative energy sources on a glosbal scale toward a low-carbon society. For the next generation power network, which uses a large number of these distributed power generation sources, energy storage technologies will be indispensable. Among these technologies, battery energy storage technology is considered to be most viable. Sumitomo Electric Industries, Ltd. has developed a redox flow battery system suitable for large scale energy storage, and carried out several demonstration projects on the stabilization of renewable energy output using the redox flow battery system. This paper describes the advantages of the redox flow battery and reviews the demonstration projects.

This bimonthly review paper highlights 100 recent publications on lithium batteries. These papers were selected from 924 contributions found from the Web of Science between 1 February 2013 and 31 March 2013. Layered oxide cathode materials, high voltage spinel and polyanion are still under extensive investigations. Significant efforts have been devoted to Si based anode materials although the well known drawbacks of volume expansion and low Coulombic efficiency of the materials have not been overcome.. Several papers have shown positive results for different electrolyte additives. Li-O₂ and Li-S batteries with high energy density are found to the hot topic in the field. There are several papers on the SOH estimation and the degradation mechanisms of Li-ion batteries. There are also reports on calculations for electrode materials, SEI formation process and stress generation in the cells.

Phase transition is an essential problem in battery research. Understanding on phase transition in synthesis precisely is necessary to obtain target products with controlled structure and composition. Knowledge about phase transitions of electrolyte can offer the information of the safe and stable working condition, and provide a way to develop new electrolyte according to the characteristics of phase transition. Phase composition and phase evolution can be illustrated concisely and directly in phase diagram. This paper summarizes briefly typical research activities on phase transition and phase diagram in Li-ion batteries during material preparation.

Electrode kinetics plays a central role in electrochemical processes relevant to a number of industrial sectors including chemical, energy, material and environment protection. The electrode kinetic processes include diffusion, charge transfer in electrolyte and surface adsorption/ desorption. The modes of mass transfer processes include convection, diffusion and electronic migration. The current-voltage relationship is the basic route to characterize the electrode reaction kinetics, and under specific electrode conditions, the Tafel semi-log equation and Butler-Volmer dynamic equation could be derived respectively for polarization curves and electrode reaction kinetics. The surface processes include pre-positive and post-positive surface conversions. Moreover, fluid mechanics calculations can reveal the tangential flow behavior on the surface of electrode and the effects on mass transfer of rotating disk electrode process.

Based on the second law of thermodynamics and pinch theory, a new parameter named effective heat transfer factor (EHTF) is introduced to evaluate the performance of heat transfer processes. By using such a parameter for process optimization of a heat storage system, it is found that the EHTF is a much better indicator for heat transfer assessment as it considers not only state parameters but also processes.

Flywheel is a mechanical based energy storage method with a wide range of potential applications. In this paper, we introduce the principle and components of a flywheel energy storage system, and look at applications of the technology in relevant engineering fields.

Due to inherent safety, long cycle life, environmental friendliness and easiness in the state of charge monitoring, vanadium flow batteries (VRB) have been regarded as one of the promising technologies for large scale energy storage applications. In this paper, technological challenges are briefly reviewed first in the commercialization of vanadium flow batteries. Future research needs are then proposed. The most recent progress is then presented in VRB stack structural design, battery system integration and demonstration, especially the collaborative efforts made by the VRB research group of Dalian Institute of Chemical Physics (DICP) and Dalian Rongke Power Co. Ltd. (RKP).

Based on patent documents related to solar building published in the China Patent Retrieval System (CPRS), distribution of the proprietary technologies, volume of patent applications, China domestic applicants and supply chain of Building Integrated Photovoltaic (BIPV) industry are analyzed. Solar building technology development is found to be particularly rapid in recent years with industrial companies dominating the research and development.We show that the Photovoltaic supply chain is complete in central and eastern regions of China such as Jiangsu, Shanghai and Zhejiang. We also find that the photovoltaic industry pays a great attention to manufacturing rather applications.

There are variety of applications of battery energy storage system(battery energy storage system, BESS) used in the combined system of wind power and energy storage, and improving grid-connected wind power operation ability under dispatch by using battery energy storage system is currently one of the research focus. Based on forecast and historical operation data of a wind farm in northern China, this article reports an analysis on the wind farm forecast data to obtain the forecast error probability distribution characteristics by using an evaluation method combining the prediction error indicators and wind farm forecast assessment indicators. A battery energy storage system is then proposed to improve the ability to track wind power schedule output, followed by statistical analyses and quantification of the scope of racking schedule output. Finally, simulation verifications are performed of the effectiveness and viability of the control strategy for improving the ability of wind power tracking schedule output.

Due to weather conditions, the output power of Photovoltaic (PV) systems often experience significant fluctuation. The PV power is therefore neither a constant voltage source nor a constant current source. This can lead to a series of issues when connected to a power grid including power surge, requirement of more spinning reserve capacity and difficulties in participating power grid dispatching. The use of energy storage could improve the quality of PV output via controlling the power output. In this article, a Photovoltaic - Energy Storage Hybrid System is proposed and topology diagram and a control strategy are presented. A power converter system (PCS) is designed and analyzed for the energy storage system. These are validated through simulation using operation data of a real PV power station.

Based on the understanding of technological developments for electric automotive industry in China, a Vehicle-Energy Station-Grid (VEG) model is proposed for future electric vehicles (EVs), and associated future business implementation is explored. The use of VEG enables the EV owners to have flexible choices. For example, they choose a slow charge process in their home garages or a fast charge route at an energy station equipped with low-cost, long-life MW scale battery energy storage units for a rapid charge service. In addition, the energy station can extract or deliver energy with the gird for peak and frequency regulations. For this model to work, development of the safe and fast-charging power battery and the low cost and long life storage battery is very essential.

In the field of energy storage technologies, foreign countries started early, more achievement and experience in engineering project. Domestic energy storage technologies started late. In the distributed generation, using only one type energy storage is difficult to give good power performance for PV system. Based on our company grid-connected PV system photovoltaic with Li-ion battery and ultra-capacitor as hybrid energy storage system, it combined with the energy storage type of fast response characteristic and large capacity storage characteristics. The storage system controller coordinated power control between the energy storages and other power equipment in the system, which made the grid-connected power on demand and under control. The system can effectively increase the power output ability of PV generation system, decrease the frequency of charging and discharging for energy storage system, greatly extend the battery cycle life, has good application and popularization value.

Electrical energy storage (EES) is a key to break the bottleneck of penetration of renewable generation, and an essential component of smart grids. At the initial stage of commercialization of EES technologies, a systematic analysis and comparison of different technologies is important, which could help technology selection. This paper presents an overview of various EES technologies including mechanical (pumped hydro, compressed air, flywheel) electrochemical (secondary battery, flow battery) and chemical (hydrogen, synthetic natural gas). Finally, future developments of these technologies are summarized.