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Constant voltage ultracapacitor
Journal article   Peer reviewed

Constant voltage ultracapacitor

Ezzat G. Bakhoum
Journal of renewable and sustainable energy, Vol.4(3), 33116
05/2012
DOI: https://doi.org/10.1063/1.4729585
Web of Science ID: WOS:000305882200027

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3 Times Cited - Web of Science

Abstract

Ultracapacitors have attracted lots of attention recently due to their growing use in hybrid vehicles and in energy storage applications for the smart grid. A very undesirable feature of ultracapacitors is the fact that the voltage drops as the capacitor is discharged. DC-DC converters are employed at present to convert the voltage of the ultracapacitor to constant voltage; however, these converters typically do not operate if the voltage of the ultracapacitor drops below 1 V. In addition, DC-DC converters suffer from well-known size/efficiency tradeoffs. This paper introduces a novel new ultracapacitor that is characterized by constant voltage. The new ultracapacitor does not utilize familiar energy conversion principles. Rather, operation depends on an embedded electromechanical system that actually alters the capacitance of the ultracapacitor as the device is discharged. Due to a simple proportionality relationship between charge, capacitance and voltage, the voltage remains constant. Theoretical and experimental investigations have shown that the embedded mechanism for altering the capacitance has an efficiency of 99% or higher.

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