Tài liệu miễn phí Hoá dầu
Download Tài liệu học tập miễn phí Hoá dầu
Alternating Currents
The general topic of alternating current (AC) influence on the battery charging is necessarily a huge undertaking. The vast body of knowledge in electrochemical systems has been largely associated with direct current (DC) measurements. To place this into perspective, it helps to note that a DC can be considered a special case of an AC where the frequency of the AC is zero (or, as a practical matter, has a frequency having a very long period).
8/29/2018 7:08:54 PM +00:00
Capacity
For a battery, the term ‘capacity’ relates to the ‘charge capacity’, i.e., the total amount of electrical charge Q that can be drawn from the device before a specified cutoff voltage V is reached. In the battery industry, charge capacity is typically measured in ampere-hours (Ah). Practically, the capacity Q is determined as the integral of the discharge current over the discharge time, starting from the fully charged state and ending at the fully discharged state
8/29/2018 7:08:54 PM +00:00
Charge–Discharge Curves
The voltage of a battery is given by its open-circuit voltage (OCV) and overvoltages occurring due to diffusion processes, electrochemical reactions, and ohmic resistances. Because of these overvoltages, the cell voltage is always above the OCV during charging and it is always below the OCV during discharging. The battery voltage during discharging can be expressed in a first-order approximation according to the following equation:
8/29/2018 7:08:54 PM +00:00
Codes and Standards
The terms codes and standards are almost synonymous; they have essentially the same meaning. They are different in that codes are usually requirements imposed by regulatory authorities, whereas standards are consensus documents adopted voluntarily by organizations with a common interest in a technology, product, or practice.
8/29/2018 7:08:54 PM +00:00
Fast Charging
Increased environmental concerns and fuel costs have made a significant impact on transportation technology, as a result of which advanced vehicles with enhanced fuel economy and less emission have started to penetrate the market and have gained popularity.
8/29/2018 7:08:54 PM +00:00
Lifetime Prediction
Lifetime prediction of electrochemical systems obviously requires a detailed understanding of aging processes and their causes. However, lifetime prediction on the basis of such detailed understanding is only possible in the few applications where one aging process dominates and where test procedures and methods are available, which allow investigation of this dominant aging process without the influence of other aging processes.
8/29/2018 7:08:54 PM +00:00
Modeling
The ‘ideal’ rechargeable battery is obviously the one that has high power and energy density, high discharge rate, flat discharge curves, good low-temperature performance, and long service and shelf life as well as safety. However, the mentioned preferable characteristics of rechargeable batteries conflict with one another and require trade-offs. The objective of advanced battery research and development should be to obtain a compromise among the battery requirements.
8/29/2018 7:08:54 PM +00:00
B BATTERIES
Contents Nomenclature Capacity Energy Self-Discharge Charging Methods Fast Charging Charge–Discharge Curves Partial-State-of-Charge Adaptive State-of-Charge Determination Dynamics Alternating Currents Parallel and Series Connections Modeling Lifetime Prediction Codes and Standards
8/29/2018 7:08:54 PM +00:00
Parallel and Series Connections
Series and parallel connections are simple to define in electrical terms, but underlying these basic concepts is a wealth of detail. The battery voltage determines the number of series connections and can have a significant effect on battery safety and reliability.
8/29/2018 7:08:54 PM +00:00
Partial-State-of-Charge
The 150 years history of the lead–acid battery has seen technological improvements in numerous areas, including grid alloy, jar material, and manufacturing methods. The most notable improvement is the valveregulated lead–acid (VRLA) battery, both absorbent glass mat and gel electrolyte versions.
8/29/2018 7:08:54 PM +00:00
Self-Discharge
Self-discharge processes are processes that decrease the performance of electrochemical power sources without flow of current through an external circuit (i.e., with no load connected to the positive and negative poles). Batteries that are prone to self-discharge are generally disfavored by industry, because they have a short shelf life and require regular monitoring to maintain them in a full state of charge.
8/29/2018 7:08:54 PM +00:00
Adaptive State-of-Charge Determination
University of Technology, Eindhoven, The Netherlands V Pop, Holst Centre/IMEC-NL, Eindhoven, The One of the challenges that face modern society is the search for sustainability. Sustainable economic development requires the existence of clean renewable energy sources and efficient energy storage media.
8/29/2018 7:08:54 PM +00:00
BATTERIES AND FUEL CELLS
The electrical efficiency Z of a galvanic cell or supercapacitor is defined as the ratio of the electrical energy that can be removed from it to the electrical energy supplied. Often the electrical efficiency of a galvanic cell or supercapacitor is also called energy efficiency as heat generation is never a useful by-product of the operation of galvanic cells or supercapacitors:
8/29/2018 7:08:54 PM +00:00
Lifetime
All electrochemical power sources deteriorate over time. In contrast to many other technologies, however, the deterioration tends to be slow and predictable, and catastrophic failure is rarely observed. Owing to the gradual decline in performance, it is important to have a clear definition of what constitutes end of lifetime. The following terms are used to denote different aspects of lifetime (see Figure 1)
8/29/2018 7:08:54 PM +00:00
Power
In rapid-response situations, the ability of supercapacitors and batteries to provide power (W) over a short period of time is more important than their ability to provide energy (Wh) over a long period of time. Familiar examples are the starting of internal combustion engines, the protection of computers and telecommunications equipment against brief interruptions of mains power supply, the starting of electrical motors with high inrush currents, and the triggering of fuses.
8/29/2018 7:08:54 PM +00:00
Techno-Economic Assessments
In view of a possible climate change and increasing oil-prices, there is a need to change our rate of using carbon-intensive fossil energy resources in the future. Fuel cells and batteries have been proposed as technical solutions for energy conversion and storage, allowing for paving the way for a prospective world relying mainly on renewable low-carbon intensive energy sources.
8/29/2018 7:08:54 PM +00:00
Application
Electrochemical capacitors (ECCs; sometimes referred to as supercapacitors or ultracapacitors) are energy storage devices that have much higher capacitance and energy density than the traditional dielectric capacitors that are presently sold in various markets by the billions each year. Electrochemical capacitors have much lower energy density and much higher power capacity than batteries.
8/29/2018 7:08:54 PM +00:00
Electrochemical Capacitors: Ionic Liquid Electrolytes
Double-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).
8/29/2018 7:08:54 PM +00:00
Electrochemical Double-Layer Capacitors
Electrochemical double-layer capacitors store electrical energy at the phase boundary between an electronic conductor (electrode) and a liquid ionic conductor (electrolyte solution). In contrast to that, electrostatic space charge layers at dielectric oxide films, formed anodically on etched aluminum or tantalum foils of conventional electrolytic capacitors, should not be confused with the electrochemical double layer.
8/29/2018 7:08:54 PM +00:00
Electrochemical Hybrid Capacitors
Asymmetric’ supercapacitors consist of two electrodes that differ considerably in capacitance and utilize different mechanisms for energy storage. The asymmetric concept may employ a faradaic, rechargeable batterytype electrode process at the positive electrode, and a nonfaradaic double-layer capacitance at the negative electrode.
8/29/2018 7:08:54 PM +00:00
Electrochemical Metal Oxides Capacitors
Manufacture of metal oxide electrodes: Thermochemical oxide layers, metal oxide hydrates, amorphous and crystalline powders, and supported and adsorbed ruthenium di-oxide (RuO2).
8/29/2018 7:08:54 PM +00:00
Electrochemical Polymer Capacitors
‘Metallically’ conducting polymers show good intrinsic conductivity, at least in the charged state. The specific capacitance values, potential ranges, long-term stabilities, and cycle lives of supercapacitors based on polymers are rather moderate, compared to the cycle lives of those based on carbon and metal oxide materials.
8/29/2018 7:08:54 PM +00:00
Electrostatic Solid-State Capacitors
Conventional electrostatic capacitors contain a dielectric instead of an electrolyte solution. Electrochemical supercapacitors, however, contain a liquid electrolyte (aqueous, nonaqueous), and can be classified by the electrode material used (carbon, metal oxide, polymer) and the operating principle (double-layer capacitance, redox pseudocapacitance, hybrid capacitance).
8/29/2018 7:08:54 PM +00:00
C CAPACITORS
Capacitors store electrical charge. Generally, that charge is stored physically, as equal quantities of positive and negative charge are separated on opposite faces of an insulating material. When the two faces are connected by an external current path, current flows until complete charge balance is achieved. The capacitor can then be returned to its charged state by applying voltage.
8/29/2018 7:08:54 PM +00:00
CHEMISTRY, ELECTROCHEMISTRY, AND ELECTROCHEMICAL APPLICATIONS
Aluminum is the most abundant metallic element, making up about 8% by weight of the Earth’s crust. It is a silverywhite metal and belongs to group III of the periodic table. Its atomic number is 13 and atomic weight 26.981 54. Pure aluminum is soft and ductile.
8/29/2018 7:08:54 PM +00:00
Carbon
Carbon T Takamura, Harbin Institute of Technology, Harbin, China & 2009 Elsevier B.V. All rights reserved. Physical and Chemical Properties of Carbon Families Morphology of Carbon Carbon is solid under ambient temperature and pressure and there are four allotropes: diamond, graphite, nanotubes and fullerenes, and carbynes, and in addition, there are many morphologies including amorphous carbons, glass-like carbons, porous carbons, and so on. The presence of such a wide variety of carbon morphologies is ascribed to the presence of different hybrid atomic/molecular orbitals: sp1, sp2, and sp3. Usually, the binding structure of solid carbon consists of hybridization of sp2 and sp3 orbitals, which form...
8/29/2018 7:08:54 PM +00:00
Bài thuyết trình môn Công nghệ hoàn tất: Kỹ thuật nhuộm - in hoa
Sau quá trình tiền xử lý, in nhuộm vải phải trải qua nhiều khâu xử lý cơ học, chịu nhiều tác nhân của hóa chất và chịu xử lý của các điều kiện nhiệt ẩm nên vải xử lý nên vải thường bị dãn dài, co ngang, mặt vải không nhẵn phẳng nên chúng chưa đáp ứng được yêu cầu sản phẩm. Do đó trước khi xuất xưởng vải phải được qua khâu hoàn tất. Tham khảo bài tiểu luận này để nghiên cứu quá trình xử lý vải trước khi xuất xưởng. Công nghệ hoàn tất này có thể tiến hành bằng hai cách: Xử lý hoàn tất bằng phương pháp cơ học và xử lý hoàn tất bằng xử lý hóa học.
8/29/2018 7:05:35 PM +00:00
Electric Vehicles: Fuel Cells
Hydrogen fuel cells are one of the most promising alternatives to internal combustion engine hybrids and pure battery electric power for propelling passenger vehicles. Compared to internal combustion engine hybrid vehicles burning hydrocarbon fuels, fuel cell vehicles offer three primary advantages. First, the fuel cell system produces no tank-to-wheel carbon dioxide emissions and no other harmful emissions such as oxides of nitrogen, carbon monoxide, or particulates. Second, the fuel cell system offers the potential for approximately 30% higher well-to-wheel energy efficiency. Third, the hydrogen fuel consumed by the fuel cell can be produced from a variety of renewable sources...
8/29/2018 7:02:04 PM +00:00
Aviation: Fuel Cells
Fuel cell-powered aircraft have been of long-term interest to the aviation community because of their potential for improved performance and environmental compatibility. Only recently have improvements in the technological readiness of fuel cell power plants enabled the first aviation applications. Based on the results of conceptual design studies and a few technology demonstration projects, a widespread understanding of the importance of fuel cell power plants for near-term and future aviation applications has emerged. In the near term, fuel cells can exhibit compelling performance advantages in applications such as auxiliary power generation and propulsive power generation for small-scale aircraft and...
8/29/2018 7:02:04 PM +00:00
Buses: Fuel Cells
Discussions about the future of transportation are marked by three key factors À growing energy demand and energy security on the one side and climate change and environmental protection on the other. The word that is most often used to embody all these concerns is ‘sustainability’ or, in the field of transportation, ‘sustainable mobility’. Achieving sustainable mobility is the big challenge for the future in the vehicle and associated industries. It is now common wisdom that transport based on fossil resources is a finite proposition. Until today, the burning of fossil fuels in internal combustion engines (ICEs) was the...
8/29/2018 7:02:04 PM +00:00