142 research outputs found
Regenerative fuel cells
No full textA regenerative fuel cell (RFC) is a hydrogen accumulator which is charged via an electrolyzer (electricity conversion into H2) and discharged via the fuel cell (H2 conversion into electricity), where the storage media is pressurized hydrogen. The also generated oxygen is mostly not stored in terrestrial applications. There are discrete RFCs (DRFC) consisting of two separate stacks (electrolyzer and fuel cell) and unitized RFCs (URFC) with one single stack working during charge in electrolysis mode and during discharge in fuel cell mode. URFCs show a high specific energy up to 1500 Wh kg−1. Furthermore, it is possible to optimize the power and energy of the system independently, which is important for seasonal storage of larger amounts of energy. In contrast to conventional electrochemical accumulators the discharge power of RFCs is unaffected by the state-of-charge of the system. But unfortunately, due to the long conversion chain with associated losses, RFCs generally have low levels of efficiency compared to conventional electrochemical accumulators. The high specific energy of URFCs makes the system interesting for niche applications in military and space areas where efficiency and related costs are not primary parameters. For civil terrestrial applications, however, costs and electrical efficiency are mostly primary parameters. DRFCs are preferred since the individual stacks (EL, FC) can be better optimized. However, for the time being, there are existing no commercial applications of RFCs, as they are not really competitive, especially not with electrochemical accumulators. In the future could be electricity storage with RFCs possible in off-grid or island applications in which a high level of autonomy is required but also in grid application with high share of renewables to stabilized power supply. In a broader sense are power-to-gas storage systems identically with DRFCs. Power-to-gas technologies and therefore also electrolyzers currently are developing strongly which will decreases the costs and increases the efficiency of RFC as well. The RFC technology is in the moment proton exchange membranes based, but they are relatively costly caused by use of platin group metal catalysts. Alkaline-RFCs could reduce the cost by using non-platin group metal catalysts. Because Alkaline-RFCs show an unsatisfactory performance and poor cyclability, therefore, the development is still in an initial stage. The efficiency of PEM-RFCs (URFC max. 35%, DRFC max. 40%) is relatively low. Higher efficiencies, however, show SO-RFCs. SO-URFCs already reach today in an early development state ca. 45% efficiency and could be used also in terrestrial applications
Cell Components – Electrodes | Nanoelectrodes
No full textThis chapter deals with the preparation, characterization, electrochemical behavior and application of arrays of nanoelectrodes
for electrochemical power sources. Different preparation methods are presented, focusing on membrane templated
deposition, seed-mediated growth and hydrothermal synthesis. Arrays of inlaid nanoelectrodes are preferred for advanced
electroanalytical and sensing purposes, where the Faradaic to capacitive current ratio need to be maximized, while complex
3D architectures are of particular interest for application requiring high specific surface and composed by high aspect ratio
nanomaterials, such as for batteries, supercapacitors and photoelectrochemical devices. The way how the morphology of the
array influences its electrochemical behavior is discussed, together with some fundamentals concerning the electrochemical
characterization. Finally, recent examples of studies on arrays of nanoelectrodes in batteries and supercapacitors are
presented
Electrochemical capacitors: Ionic Liquid Electrolytes
No full textDouble-layer carbon supercapacitors (electrochemical
double-layer capacitor (EDLCs)) based on two carbon
electrodes of high surface area separated by an electrolyte
are the most popular electrochemical supercapacitors. The
charge process is electrostatic with charge separation at
the two electrode–electrolyte interfaces. The EDLCs can
thus be modeled with two capacitances in series with what
is called equivalent series resistance (ESR). Given that the
electrode capacitance depends on the reciprocal of the
double-layer thickness, and that it is directly related to the carbon surface area, typically of several hundred square meters per gram of
carbon, the capacitance of EDLCs is significantly higher
than that of the dielectric and electrolytic capacitors. The
stored energy of EDLCs is also higher than that of the
dielectric and electrolytic capacitors, but it is lower than
that of batteries....
Hydrogen Evolution
No full textThe article begins with a brief presentation of the strategic importance of the hydrogen evolution reaction in various fields; this is followed by a discussion of its reversibility and of the factors on which reversibility depends. Adsorption of hydrogen atoms is a necessary step that depends on the interaction of metal surfaces with solvents. Thus, a correlation is found between M-H bond strength and hydrophilicity of metal surfaces. This point is discussed with the help of voltammetric curves for platinum-group metals. Besides being adsorbed, hydrogen atoms can also penetrate beneath the surface, thus affecting the adsorption energy on the surface. Hydrogen evolution is often accompanied by cathodic poisoning owing to the presence of metallic impurities. Ways to minimize this are discussed. The three most popular mechanisms of the electrode reaction for hydrogen liberation are discussed and kinetic parameters reported. The effect of the coverage of the electrode with the intermediate (H ad) is illustrated in detail. The effect of the nature of the electrode material (in electrocatalysis) is discussed using the so-called volcano curves depicting the dependence of the activity on M-H bond strength. A detailed analysis of electronic and geometric factors in electrocatalysis is also carried out. Finally, the findings of a survey of the most active materials in acidic and alkaline solutions are presented
A safe, low-cost, and sustainable lithium-ion polymer battery
No full textA polymer lithium-ion battery, formed by a Li4/3Ti5/3O4- LiFePO4 electrode combination and a poly(vinylidene fluoride) (PVdF)-based gel electrolyte, is presented and discussed. The electrochemical characterization demonstrates that this battery is capable of delivering appreciable capacity values at rates ranging from C/32 (160 mAh g(-1)) to 0.75C (130 mAh g(-1)), this being accompanied by a remarkable cycle life. In addition, because the two electrodes are based on common and nontoxic materials and operate within the stability window of the electrolyte, the battery is expected to be safe, inexpensive, and compatible with the environment. All these properties make the battery of prospective interest for application in the hybrid and electric vehicle field. (C) 2004 The Electrochemical Society
Battery parameters for hybrid electric vehicles
No full textThis chapter discusses the evaluation of the key parameters of lithium-ion batteries for power assist and plug-in HEV applications on the basis of reference tests set up by US Advanced Battery Consortium (USABC) –Department of Energy (DOE); a battery case study is used to highlight the analysis procedure. The chapter then briefly summarizes the main characteristics of lithium-ion batteries already on the market and under development, with emphasis also devoted to safety of each battery-chemistry. The use of supercapacitors (ultracapacitors) in parallel with the batteries to increase both performance and battery life is also discussed, and limits and future developments of lithium-ion batteries and of supercapacitors are included. At the end is a short discussion of electric vehicles powered by PEM fuel cells
Brennstoffzelle fuer die dezentrale Hausenergieverordnung Technik - Betrieb - Kosten - Arbeitsplaetze - Aus- und Weiterbildung. Tagungs-Unterlagen (Manuskriptform)
No full textDieser Tagungsband enthaelt vier Beitraege mit folgenden Themen: Uebersicht und Einfuehrung zur Technik der Brennstoffzelle und erste Betriebserfahrungen (J. Garche); Kostenfragen bei der Markteinfuehrung (G. Erdmann); Die Brennstoffzelle kommt - Markteinfuehrung aus Sicht eines regionalen Energiedienstleisters (J. Kraemer, Elektrizitaetswerk Rheinhessen AG); Auswirkungen der Innovation Brennstoffzelle auf Handwerksberufe - Anforderungen, Taetigkeiten, Berufsbilder, Ausbildungsanordnungen (F. Marscheider-Weidemann).This volume contains four contributions on the following subjects: Outline of and introduction to the fuel cell technology and preliminary performance results (J. Garche); Cost aspects of market introduction (G. Erdmann); The fuel cell is on its way - market introduction from the view of a regional utility (J. Kraemer, Elektrizitaetswerk Rheinhessen AG); Effects of the fuel cell innovation on the trade sector - requirements, work, jobs, training (F. Marscheider-Weidemann).SIGLEAvailable from TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman
Methods and Instruments | Thermal Analysis
No full textThis chapter presents the most relevant thermal characterization techniques commonly deployed for characterization of batteries, fuel cells and supercapacitors that includes thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), evolved gas analysis (EGA), accelerating rate calorimetry (ARC), thermomechanical analysis (TMA) and dynamic mechanical analysis (DMA). The chapter highlights the working principle of these techniques, their relevant thermal metrics, and the key aspects for performing the thermal measurement for these applications. The most important practical application aspects of thermal methods described are: (1) characterization and quality control of raw materials, supporting materials and electrode, (2) performance testing, (3) safety evaluation and (4) real system simulation to power the development of emerging energy storage devices. The research applications of thermal methods are highlighted to study the energy devices materials and components, the thermal behavior and failure mechanism that is still not fully realized to meet the growing demand for safer, more efficient, and sustainable energy storage solutions. Finally, the gaps in applications of thermo-analytical techniques for characterization and quality control of energy storages devices are identified with conclusion for further improvements including international standardizations and implementation of these standards into metrology system and manufacturing.Pei Lay Yap and Dusan Losi
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