Energy and Power Requirements

Comminution is mechanically a very wasteful process. It has been seen that most of the energy is lost, and this is so because of the difficulty in transmitting the applied forces to the particles in the mill contents that most need to be broken down. The culprit in this 

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The cost of a remote repair facility ranges from about 500,000 to 730,000, depending on the beam energy and power required. The current power range available for a portable accelerator is 45 to 300 W, with the energies varying from 1.5 to 9 MeV. 

The principal battery which is under development with a beta-alumina electrolyte is the sodium/sulphur system which operates at 300-400 C and has liquid electrodes. This is described in my second lecture to the summer school. The interest in this battery stems from its projected application as a traction battery for vehicles and as a load levelling device for power stations. For such applications the energy and power requirements are many orders of magnitude larger than for the solid state batteries described above and current densities of 200 mA/cm are commonplace. Liquid electrodes are therefore necessary to avoid electrode polarisation effects. The practical problems of developing these high temperature, high power level batteries are formidable and a substantial world-wide effort is involved. 

The performance specification and the acceptable cost of a battery depend, of course, on its application. Here we are concerned with traction batteries, primarily for use in road vehicles, and we have concentrated our attention upon urban buses and light delivery vehicles. In order to define the battery performance targets it is first necessary to consider the operational problem from the point of view of the traffic manager, who specifies the journey profile which the vehicle must be capable of making, and then to select a particular design of vehicle in order to interpret this duty cycle in terms of energy and power requirements and the permissible mass and volume of the battery. When this was done, we arrived at a specification of battery performance for each class of vehicle (Table l). 

Portable applications of fuel cells include auxiliary power unit and emergency power systems, power tools, laptop computers, and other mobile devices including cell phones. Demands are also growing with the increased energy and power requirements for broadband mobile computing (Dyer, 2002). Power requirements may vary from a few watts (<1 W) to a few hundred watts or kilowatts (1-5 kW). Portable fuel cells are often categorized on the basis of power requirements (DOE 2010— Record 11009) such as applications less than 2 W, applications for 10-50 W, and applications for 100-250 W. 

Shukla et al., (2003) have described a process to assess the energy and power requirements of a fuel cell-based automobile. They have estimated that the power plant of a modem car must be capable of delivering about 50 kW of sustained power for accessories and hill climbing, with burst-power requirement for a few tens of seconds to about 80 kW during acceleration. For a car with these performance characteristics, this sets the upper power limit required, but in common usage rarely exceeds 15 kW while cruising. 

Reserve batteries have been developed for appHcations that require a long inactive shelf period foUowed by intense discharge during which high energy and power, and sometimes operation at low ambient temperature, are required. These batteries are usually classified by the mechanism of activation which is employed. There are water-activated batteries that utilize fresh or seawater electrolyte-activated batteries, some using the complete electrolyte, some only the solvent gas-activated batteries where the gas is used as either an active cathode material or part of the electrolyte and heat-activated or thermal batteries which use a soHd salt electrolyte activated by melting on appHcation of heat. 

The energy or power required by any separation process is related more or less directly to its thermodynamic classification. There are, broadly speaking, three general types of continuous separation processes reversible, partially reversible, and irreversible. 

A very important feature of solid-state technology is energy conservation in the process of speed control. The slip losses that appear in the rotor circuit are now totally eliminated. With the application of this technology, we can change the characteristics of the motor so that the voltage and frequency are set at values just sufficient to meet the speed and power requirements of the load. The power drawn from the mains is completely utilized in doing useful work rather than appearing as stator losses, rotor slip losses or external resistance losses of the rotor circuit. 

Vehicle fuel economy is normally measured in miles per gallon. At any given instant, it depends on the energy content of a gallon of fuel (Qf), the vehicle velocity (V.,) and power required (P,-5q), the thermal efficiency with which the engine converts fuel energy into useful output work (rj,.), and the mechanical efficiency with which the driveline delivers that work to the vehicle wheels (r j). Specifically,... 

Chemical kinetics is a powerful tool that provides unique mechanistic information and deep insight into the activation process that is at the heart of every chemical transformation. This chapter is structured around some of the most important types of information obtained from kinetic studies. The rate law provides the composition of the transition state (TS), kinetic isotope effects (KIEs) can establish whether a specific bond is involved in the activation process, and activation parameters provide information about the energy and entropy requirements. Independent generation, characterization, and reactivity studies of potential intermediates allow one to search for and identify such intermediates in multistep reactions by spectroscopic means or by use of chemical traps. 

In secondary batteries finally, on which the following consideration concentrates, the charging is done electrochemically by reversing the discharging process. This requirement is quite demanding in terms of kinetics and makes a compromise indispensable with respect to energy and power density. The requirement of reversibility... 

Within a given line of battery technology, energy and power density typically are inversely related. Increasing the energy density requires maximization of active electrode material mass per battery mass and thus requires minimization of the amount of additional components (such as current collector, conductive additives, or void space for optimizing electronic and ionic connectivity within an electrode material, see Section 3.5.5), most of which are beneficial for increased power densities. 

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