Fractional-Order Modeling: Application to Ultra-High Density Capacitors (Super-Capacitors)

by Prof. Ahmed S. Elwakil, Ph.D.,
Dept. of Electrical and Computer Engineering
College of Engineering
University of Sharjah
P.O. Box 27272

Rapid advance in material science has produced a number of new materials that increase the energy storage capacity. Thus, a new wave of ultra-high density capacitive devices has been introduced in the market in the past few year by different manufacturers. Most of these “supercapacitors” are carbon-carbon Electrochemical Double Layer Capacitors (EDCLs) rated by manufactures at DC for the purpose of energy storage. Typical values of 1 Farad up to 3000 Farad are now easily obtained in the market. However, the porous nature of the electrodes and the complex dispersive nature of the materials used to fabricate these capacitors have led many researchers to observe a complex frequency-dependent behavior for these supercapacitors once used in non-DC applications; i.e. with AC charging voltages or currents. It was shown by several researchers that the best models that can capture the behavior of these new energy storage devices are fractional-order models. These accurate models are needed for the deisgn or subsequent power electronic circuits such as DC-DC converters. Yet this also implies new mathematical formulae that are not known and definitely not being employed as yet by the industry. This talk aims at surveying this topic in detail.

Biography: A. S. Elwakil was born in Cairo, Egypt. He received his Ph.D. from National University of Ireland ( University College Dublin) and his BS and MS degrees from Cairo university, all in Electrical Engineering. His research interests are primarily in the areas of Circuit Theory, Nonlinear Dynamics, Chaos Theory, as well as the relatively new area of Fractional-Order Circuits and Systems, in which he has played a pivotal role towards the migration of its concepts to electrical engineering. Prof. Elwakil has contributed to a diverse number of applications ranging from the modeling of oscillatory networks and nonlinear electronic circuits to energy devices and bio-materials and is the author and co-author of over 200 publications in these areas. He currently serves as an Associate Editor for the Int. J. of Circuit Theory and Applications (Wiley) and was a past Editor of this journal. He is also an Associate Editor of the Int. J. Bifurcation & Chaos, (World Scientific) and the Journal of Nonlinear Theory and its Applications (NOLTA). He was a past Associate Editor for the J. of Dynamics of Continuous, Discrete and Impulsive Systems: Series-B, published by the American Institute of Mathematical Sciences (AIMS) and is currently on the Editorial Board of the IEEE J. Emerging and Selected Topics in Circuits and Systems and an Associate Editor for the Int. J. Electronics & Communications (AEUE), Elsevier.

Prof. Elwakil was a Keynote speaker at the sixth International Workshop on Chaos Fractals and Applications, Taiyuan, Shanxi, China, August 2013, a keynote speaker at the Int. Conf. on Fractional Differentiation and Its Applications (ICFDA), Catania, Italy, June 2014 and a keynote speaker at the 39th Int. Conf. on Telecommunications and Signal Processing (TSP), Vienna, Austria, June 2016 where he lectured on the theory of Fractional-order circuits and systems: An emerging interdisciplinary research area. He has been a member of the IEEE Technical Committee on Nonlinear Circuits and Systems (TCNCAS) since 2003.

Prof. Elwakil was a Lead Guest Editor for the IEEE J. of Emerging and Selected Topics in Circuits & Systems, special issue on fractional-order circuits and systems (Sep. 2013) and a Guest Editor for a special issue on Chaos-Fractals Theories and Applications published in the J. of Mathematical Problems in Engineering, 2014. He is also the guest editor for a special issue on Fractional-Order Circuits (June 2016) in the J. Circuits Systems & Signal Processing (Springer). His paper ”Construction of classes of circuit-independent chaotic oscillators using passive only non linear devices," published in IEEE Trans. on Circuits & Systems-March 2001, is among its top 50 cited papers. The same paper was identified (by Reuters-Thomson) as the fastest moving front in Mathematics in January 2007. His paper “Fractional-order circuits and systems: An emerging interdisciplinary research area,” published in the IEEE Circuits & Systems Magazine is also among its top 50 cited papers. Prof. Elwakil received the Egyptian Government first class medal for achievements in Engineering Sciences in 2003, 2009 and 2015, respectively and was a visiting Professor/Researcher at Istanbul Technical University (Istanbul, Turkey), University of Calgary (Alberta, Canada), Queens University (Belfast, UK), Technical University of Denmark (Lyngby, Denmark), Ohio State University (Columbus, Ohio), University College Cork (Cork, Ireland), King Abdullah University of Science and Technology (KAUST, Saudi Arabia) and Nile University (Cairo, Egypt).