We overview different alternative energy resources and comment on their benefits and challenges. We highlight some features of alternative and sustainable energy resources and discuss some challenges for their integration into the power grid. In view of global trend toward blending alternatives and conventional energy resources in electrical power grids, a more robust energy distribution approach is necessary. Here, we present an alternative to the power grid with great potential for integrating alternative energy sources and defining microgrids-the Controlled-Delivery Grid (CDG). We comment how this new digital approach enhances the distribution of energy may help to resolve those challenges. We also examine the role of energy storage elements (batteries, super-capacitors), and sustainable energy resources in this new approach to the power grid. We provide some numerical analysis on the performance of energy distribution of the CDG and some experimental results that highlight some of its features. V C 2017 American Institute of Chemical Engineers Environ Prog, 37: 155-164, 2018
We demonstrate that the capacitance of ionic-liquid filled supercapacitors is substantially increased by placing a diode-like structure on the separator membrane. We call the structured separator -gate, and demonstrate that the order of a p-n layout with respect to the auxiliary electrode affects the overall cell's capacitance. The smallest ESR and the largest capacitance values are noted when the p-side is facing the auxiliary electrode.
Electrochemical cells consist of two half-cells containing each an anode and a cathode. There is an ionic contact between the two half-cells to maintain the flow of ionic charge. In order to maintain the charge flow in a voltaic cell, a salt bridge is placed between the two half-cells. We replaced the salt-bridge by a third electrode - a conductive and permeable gate electrode. A bias potential was then applied to this gate electrode. In that way, we were able to control the external current of the cell. This would be the first step towards the realization of ion transistors. In preliminary studies, several gate electrodes were considered: layers of functionalized carbon nanotubes (CNT) and metal plate capacitors. Cyclic voltammetry and electrochemical impedance spectroscopy revealed the effect of the gate bias on the effective capacitance and impedance of the cell. Current-Voltage measurements (I-V curves) were made on layered structures, which were made of p-type and n-type CNT. These data clearly exhibited the formation of barrier(s) between the two layers. Cyclic voltammetry (CV) measurements were carried out using an electrochemical workstation (CHI760C, Electrochemical Instrument) at room temperature and using 0.01 M solution of NaCl as electrolyte. Various scan rates of 0.01, 0.05, 0.1 and 0.5 Vs-1 were assessed. Two graphite rods, one serving as a working and the other as a counter electrode, were used. Ag/AgCl (3M KCl filled) electrode served as the reference. The gate electrode was placed in the middle of the cell, between the working and counter electrodes. The corresponding specific capacitances were calculated from the CV data. Electrochemical impedance spectroscopy (EIS) was performed for each of the gate electrodes, as well. The data were taken at a dc bias of 0.24 V with sinusoidal signal of small magnitude over sub to kilo Hertz frequency range. The capacitive behavior was more pronounced at low frequencies. Membranes composed of p-i-n structures, a p-type layer of CNT, followed by an insulating layer of MMA and finished by an n-type CNT all deposited on a 10-micron Teflon filter substrate exhibited the larger capacitive behavior compared to p-n layered membranes or metallic capacitor. Chrono-potentiometry method was performed for gate electrodes. The curve within a potential window indicated from the time constant better capacitive behavior in p-i-n than other two gate electrodes. The value indicated in milli farad magnitude which is similar to the range of values found in cyclic voltammetry and electrochemical impedance spectroscopy techniques. References: [1] Y. Zhang, H. Grebel, “Controlling Ionic Currents with Transistor-like Structure”, ECS Transactions 2 (18). 2007 [2] S. Sreevatsa, H. Grebel, “Carbon Nanotube Structures as Ionic Barriers: A New Corrosion Prevention Concept”, ECS Transactions 19 (29) 91-100. 2009
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