TAILIEUCHUNG - 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. | Power H Wenzl Clausthal University of Technology Clausthal-Zellerfeld Germany 2009 Elsevier . All rights reserved. Definitions and Terms 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. Ragone diagram is a method of comparing the specific power and specific energy of different power sources in these circumstances. Power is the rate at which energy is used. From a practical point of view high power corresponds to the discharging of a battery in a few minutes or the discharging of a supercapacitor in a few seconds. For certain types of industrial Ni-Cd batteries the discharge rate may even be as brief as one second. This article focuses on applications of electrochemical power sources that have been designed or are used for such high power discharges. There are many complications when trying to determine the power capability of electrochemical systems. For example instead of a constant power discharge a constant current discharge is sometimes used in which case the average power must be calculated. In addition in certain applications it is also necessary to ascertain how well a system can reabsorb power . during regenerative braking in electric vehicles or during sudden gusts of a wind turbine. Furthermore for fuel cells and redox flow cells the concepts of specific capacity specific energy and energy density are completely inappropriate because they depend on the size of storage tanks and not on the size of the electrochemical conversion units. Notwithstanding these difficulties the power of a fuel cell can be calculated as the product of the .
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