Use In Energy Storage Devices Research Articles

In situ growth of manganese oxide on 3D graphene by a reverse microemulsion method for supercapacitors

In this study, a new, effective strategy is reported for the fabrication of composites using manganese oxide (MnO2) grown in situ on three-dimensional (3D) graphene by the reverse microemulsion (water-in-oil) method. A uniform coating of nanoscale MnO2 layers can be observed on the internal surface of 3D graphene, which could benefit rapid ionic and electronic transport. The electrochemical performance of the MnO2/3D graphene composites is optimized by the control of the composite structure and mass loading of MnO2. The MnO2/3D graphene composite thus prepared exhibits a significantly high specific capacitance of 659.7 F g−1 at 0.3 A g−1 and an excellent retention life of 106% after 1000 cycles. The facile synthesis and excellent electrochemical performance of the MnO2/3D graphene composites indicate that the developed method demonstrates potential applications for the fabrication of novel electrode materials for use in energy storage devices.

A Review of Frequency Response Solution for Type - 3 Wind Turbines Using Energy Storage Device

This paper identifies the current approaches to provide the frequency response from type 3 (Doubly Fed Induction Generator based) wind turbines to support the grid during power imbalance. It discusses the use of energy storage devices for providing support during frequency deviation. The paper mainly focuses on the approach to connect the energy storage with the wind turbine through the DC coupling capacitor and use the already available wind turbine AC/DC/AC converter for power conversion. The process to choose an energy storage device and appropriately sizing it for desired support is stated. It also discusses the wind turbine controller strategy modification to properly operate the energy storage device and provide required support. Finally, the study shows simulation results indicating the validation of connecting energy storage through DC coupling capacitor and the updated control algorithm method in different operating condition.

The Performance of Doped Mesoporous Carbon Electrodes as Electrochemical Capacitors in Optimized Alkaline Electrolyte

Nitrogen and sulfur dual-doped mesoporous carbons were prepared through a facile template-mediated pyrolyzing method using poly(ethyleneimine) (PEI) as sources of nitrogen (N) and carbon (C), ferrous sulfate (FeSO4 7H2O) as both precursor of sulfur (S) and activation reagent along with nanoscaled silica as sacrificial supports. The as-prepared doped mesoporous carbons show perfect supercapacitive performances, which have been demonstrated by cyclic voltammetry and constant-current charge/discharge cycling techniques. The specific capacitance (SC) of the as-prepared electrode can reach 279 F/g at a current density of 1 A/g. Even at a high rate capability of 100 A/g, the electrode still shows the SC value as high as 240 F/g, retaining 86% of that at 1 A/g. Regarding the effect of electrolyte concentrations (1-6M KOH), 3 M KOH gives the best performance. The above results indicate that the doped mesoporous carbon electrodes developed in this work are promising for use in energy storage devices.

A Carbon-Free, Precious-Metal-Free, High-Performance O2 Electrode for Regenerative Fuel Cells and Metal-Air Batteries

There have been extensive research efforts focusing on developing technologies for renewable electricity, particularly solar photovoltaics and wind turbines. However, the intermittent and localized nature of wind and solar energy necessitates the development of a cost-effective way to balance energy supply and demand and to deliver electricity from remote places to cities.[1] The short-term option is the electricity grid; however, it can only support intermittent renewable electricity in a stable fashion up to approximately 20 % of grid capacity which means that fossil resources would still account for the remaining 80 % of grid electricity.[2] Clearly, the development of cost-effective energy storage devices is needed to establish a path toward fossil-free energy.The development of high-performance and cost-effective electrodes for oxygen evolution and oxygen reduction is critical for enabling the use of energy storage devices based on O2-H2O chemistries such as metal-air batteries and unitized regenerative fuel cells (URFCs).[3] Herein, we report a precious-metal-free and carbon-free O2 electrode synthesized via electrodeposition of manganese oxide (MnOx) on a stainless steel (SS) substrate followed by high-temperature calcination at 480 oC. The MnOx-SS electrode displays high oxygen reduction and water oxidation activities when tested in an electrochemical cell, comparable to that of a precious-metal based electrode, Pt/C-SS. Accelerated durability testing reveals the excellent stability of the MnOx-SS electrode compared to both the Pt/C-SS electrode and a carbon-based electrode with MnOx and Ni catalysts. This can be rationalized by the carbon-free nature of the MnOx-SS electrode which circumvents carbon corrosion at the high electrochemical potentials during water oxidation and O2 reduction. Integrating the MnOx-SS electrode as the O2 electrode in an anion exchange membrane (AEM) URFC produces round trip efficiencies of 42-45 % at 20 mA.cm-2 over 10 cycles, and exhibits significantly enhanced durability compared to the carbon-based analogue. This work demonstrates the MnOx-SS electrode’s potential for use as a high performance, scalable, precious-metal-free and carbon-free O2 electrode in AEM-URFCs and metal-air batteries.

Storage Capacity Configuration to Improve Prediction Accuracy of Photovoltaic Output

The short-term prediction accuracy of Photovoltaic(PV) output may not meet power scheduling requirements, the combined use of photovoltaic generator and energy storage device can improve the prediction accuracy. Storage capacity configuration is an important issue for the economy of PV plant and PV prediction accuracy.In this paper, the distribution character of PV prediction error is analyzed based on the probability density function evolution method. A storage capacity configuration model is built to consider economic prediction accuracy and capacity .A storage device controlling strategy was bulit.Last, a tracking - economic factor is defined which can be used for economic evaluation of the energy storage device. An example is shown that PV prediction error is in normal distribution and the proposed method can improve the prediction accuracy of PV output while increasing the level of economic use of energy storage devices. DOI : http://dx.doi.org/10.11591/telkomnika.v12i3.3838 Full Text: PDF

Recent developments and applications of energy storage devices in electrified railways

This study presents the recent application of energy storage devices in electrified railways, especially batteries, flywheels, electric double layer capacitors and hybrid energy storage devices. The storage and reuse of regenerative braking energy is managed by energy storage devices depending on the purpose of each system. The advantages resulting from the use of energy storage devices are presented by observing the results of both verification tests and practical applications in passenger services. Several real installations of energy storage for railways are shown and compared by using the Ragone plot. The effect of the use of energy storage devices on electrified railways of the future is discussed. Finally, a discussion on the recent applications and developments of energy storage devices is presented in this study. The effective use of energy storage devices is characterised on the basis of the specific applications and current trends of the research undertaken by public bodies and manufacturers.

A carbon-free, precious-metal-free, high-performance O2 electrode for regenerative fuel cells and metal–air batteries

The development of high-performance and cost-effective electrodes for oxygen evolution and oxygen reduction is critical for enabling the use of energy storage devices based on O2–H2O chemistries such as metal–air batteries and unitized regenerative fuel cells (URFCs). Herein, we report a precious-metal-free and carbon-free O2 electrode synthesized via electrodeposition of manganese oxide (MnOx) on a stainless steel (SS) substrate followed by high-temperature calcination at 480 °C. The MnOx–SS electrode displays high oxygen reduction and water oxidation activities when tested in an electrochemical cell, comparable to that of a precious-metal based electrode, Pt/C–SS. Accelerated durability testing reveals the excellent stability of the MnOx–SS electrode compared to both the Pt/C–SS electrode and a carbon-based electrode with MnOx and Ni catalysts. This can be rationalized by the carbon-free nature of the MnOx–SS electrode which circumvents carbon corrosion at the high electrochemical potentials during water oxidation and O2 reduction. Integrating the MnOx–SS electrode as the O2 electrode into an anion exchange membrane (AEM) URFC produces round-trip efficiencies of 42–45% at 20 mA cm−2 over 10 cycles, and exhibits significantly enhanced durability compared to the carbon-based analogue. This work demonstrates the MnOx–SS electrode's potential for use as a high performance, scalable, precious-metal-free and carbon-free O2 electrode in AEM-URFCs and metal–air batteries.

One-Step Solvothermal-Processed 3D Spinel-Type Manganese Oxide Microspheres and Their Improved Supercapacitive Properties

Three-dimensional (3D) spinel-type MnO2 has attracted extensive interest as a potential electrode material for supercapacitors in order to meet cost/performance requirements of power supplies. In this study, MnO2 microspheres (MS-MnO2) with a 3D spinel phase and 0.5–4.0 μm size were constructed from small MnO2 nanoparticles by a rapid and facile solvothermal process in which tetraethylammonium (TEA) was used as the template. The properties of the synthesized spinel MS-MnO2 for use in supercapacitors were investigated by cyclic voltammetry and galvanostatic charge/discharge measurements using a three-electrode system in a neutral 1 M Na2SO4 electrolyte. The synthesized spinel MS-MnO2 exhibited faster charge/discharge rates and higher capacitance than commercial MnO2 materials. The obtained results showed that the as-prepared spinel MS-MnO2 possessed good specific capacitance (SC) of ∼190 F/g at 0.5 A/g. The spinel MS-MnO2 also exhibited excellent SC retention and Coulombic efficiency of ∼100% and ∼95%, respectively, after 1000 cycles at 1 A/g, suggesting its potential application in supercapacitors. In addition, manganese oxides with large cavities were obtained through postannealing treatment and showed their potential for use in energy-storage devices, energy-conversion systems, catalysts, and sensors.

Enhancing Pseudocapacitive Charge Storage in Polymer Templated Mesoporous Materials

Growing global energy demands coupled with environmental concerns have increased the need for renewable energy sources. For intermittent renewable sources like solar and wind to become available on demand will require the use of energy storage devices. Batteries and supercapacitors, also known as electrochemical capacitors (ECs), represent the most widely used energy storage devices. Supercapacitors are frequently overlooked as an energy storage technology, however, despite the fact that these devices provide greater power, much faster response times, and longer cycle life than batteries. Their limitation is that the energy density of ECs is significantly lower than that of batteries, and this has limited their potential applications. This Account reviews our recent work on improving pseudocapacitive energy storage performance by tailoring the electrode architecture. We report our studies of mesoporous transition metal oxide architectures that store charge through surface or near-surface redox reactions, a phenomenon termed pseudocapacitance. The faradaic nature of pseudocapacitance leads to significant increases in energy density and thus represents an exciting future direction for ECs. We show that both the choice of material and electrode architecture is important for producing the ideal pseudocapacitor device. Here we first briefly review the current state of electrode architectures for pseudocapacitors, from slurry electrodes to carbon/metal oxide composites. We then describe the synthesis of mesoporous films made with amphiphilic diblock copolymer templating agents, specifically those optimized for pseudocapacitive charge storage. These include films synthesized from nanoparticle building blocks and films made from traditional battery materials. In the case of more traditional battery materials, we focus on using flexible architectures to minimize the strain associated with lithium intercalation, that is, the accumulation of lithium ions or atoms between the layers of cathode or anode materials that occurs as batteries charge and discharge. Electrochemical analysis of these mesoporous films allows for a detailed understanding of the origin of charge storage by separating capacitive contributions from traditional diffusion-controlled intercalation processes. We also discuss methods to separate the two contributions to capacitance: double-layer capacitance and pseudocapacitance. Understanding these contributions should allow the selection of materials with an optimized architecture that maximize the contribution from pseudocapacitance. From our studies, we show that nanocrystal-based nanoporous materials offer an architecture optimized for high levels of redox or surface pseudocapacitance. Interestingly, in some cases, materials engineered to minimize the strain associated with lithium insertion can also show intercalation pseudocapacitance, which is a process where insertion processes become so kinetically facile that they appear capacitive. Finally, we conclude with a summary of simple design rules that should result in high-power, high-energy-density electrode architectures. These design rules include assembling small, nanosized building blocks to maximize electrode surface area; maintaining an interconnected, open mesoporosity to facilitate solvent diffusion; seeking flexibility in electrode structure to facilitate volume expansion during lithium insertion; optimizing crystalline domain size and orientation; and creating effective electron transport pathways.

Microwave-hydrothermal preparation of a graphene/hierarchy structure MnO2 composite for a supercapacitor

Graphene/hierarchy structure manganese dioxide (GN/MnO2) composites were synthesized using a simple microwave-hydrothermal method. The properties of the prepared composites were analyzed using field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) measurements. The electrochemical performances of the composites were analyzed using cyclic voltammetry, electrochemical impedance spectrometry (EIS), and chronopotentiometry. The results showed that GN/MnO2 (10wt% graphene) displayed a specific capacitance of 244F/g at a current density of 100mA/g. An excellent cyclic stability was obtained with a capacity retention of approximately 94.3% after 500 cycles in a 1mol/L Li2SO4 solution. The improved electrochemical performance is attributed to the hierarchy structure of the manganese dioxide, which can enlarge the interface between the active materials and the electrolyte. The preparation route provides a new approach for hierarchy structure graphene composites; this work could be readily extended to the preparation of other graphene-based composites with different structures for use in energy storage devices.

Enhancement of the electrochemical capacitance of TiO2 nanotube arrays through controlled phase transformation of anatase to rutile

Here, we report the fabrication of self-organized titania (TiO(2)) nanotube array supercapacitor electrodes through controlled phase transformation of TiO(2), with aerial capacitances as high as 2.6 mF cm(-2), which far exceeds the values so far reported in the literature. The role of phase transformation in the electrochemical charge-discharge behaviour of nanocrystalline TiO(2) nanotubes is investigated and discussed in detail. The ease of synthesis and the exceptional electrochemical properties make these nanotube arrays an alternative candidate for use in energy storage devices.

Future Supplies of Electricity

E lectricity has become an essential ingredient of business, industry, and everyday living in the developed countries, and the future trend is toward greater dependence on it.[*][1] During this decade, most of the world's electricity will be generated by the combustion of fossil fuels. In the United States (the biggest single consumer of electricity worldwide), the cheapest fuel is coal, from which 57% of power was generated in 1997. Other contributors to the supply were natural gas (9%) and oil (2%). Nonfossil sources included nuclear power (20%) and hydroelectric power (11%).† Other developed countries are also heavily dependent on fossil fuels for power generation. The people of less developed countries have become increasingly aware of the desirability of enhanced availability of reliable electricity. Their opinions have been reinforced by television images, advertisements, and other communications. China and India, for example, have substantial reserves of coal, and have been burning them at an increasing rate to generate more electricity. It seems more and more likely that higher atmospheric concentrations of greenhouse gases will ultimately lead to the need to drastically curtail releases of CO2. One strategy would be to embark on greatly expanded generation of electricity from renewable resources and from nuclear reactors. Another strategy would be to develop further techniques for capturing CO2 and injecting it into long-term sinks, such as permeable formations on the continents or into the deep seas. Even if methods of reducing CO2 emissions from power plants are economically practical, many years would be required to achieve a substantial result. The complex equipment used to create electricity is costly, and historically 30 to 50 years have passed between major introductions of new equipment. One impediment to change is a lack of U.S. federal support for necessary R&D. Public expenditures on energy R&D have declined by one-third during the past 20 years. Renewable energy has had some support. One of the handicaps of wind power and solar power is intermittent generation. This factor can be minimized through the use of energy storage devices, but the net effect is to increase the true cost of wind and solar power. These sources of electricity are also facing strong economic competition from very efficient equipment powered by natural gas. Those power generators can be located close to major customers, avoiding power transmittal losses. Air pollution is minimal, and emissions of CO2 per kilowatt hour are less than those from coal-fired equipment. The potential availability of cheaper power has led to the deregulation of electric utilities. Entrepreneurs are able to use existing transmission lines to deliver electricity to the highest bidder. About half of all U.S. electricity generation is now sold on the wholesale market before it reaches customers. Much of this power travels long distances between source and user. Growth in these activities comes at a time when many parts of the North American transmission system are already operating close to their limits.† If the United States and the rest of the world are to have a sustainable and prosperous future, numerous steps must be taken. Many of them will involve changes in the means of generating and distributing electricity. The Electric Power Research Institute (EPRI) in the United States has been a key agent in organizing a continuing exploration of goals and the means of achieving them. It has sought the advice and assistance of more than 150 major U.S. stakeholder organizations, who have identified future-oriented policies and have detailed research opportunities and the costs of exploiting them.§ In total, the proposals call for a rapid increase in annual U.S. R&D expenditures from $3.1 billion to $7.7 billion. In comparison to the nation's gross domestic product, this sum is tiny. The suggestions of these stakeholders are many and constructive. They include RD the development of hydrogen fuel cells that generate competitive electricity; safe and cheaper nuclear power; and electronic control of the supply, transmission, and delivery of reliable electricity. As a means of preparing for a drastically different future, the proposed program is worthy of serious consideration. [1]: #fn-1