Development of an Accelerated Test Method for the Determination of Susceptibility to Atmospheric Corrosion

The theoretical rationale is presented for use of a repetitive cyclic current reversal voltammetric technique for characterization of localized corrosion processes, including atmospheric corrosion. Applicability of this proposed experimental protocol is applied to characterization of susceptibility to crevice and pitting corrosion, atmospheric corrosion and stress corrosion cracking. Criteria upon which relative susceptibility is based were determined and tested using two iron based alloys commonly in use at NASA-Kennedy; A36 (a low carbon steel) and 4130 (a low alloy steel). Practicality of the procedure was demonstrated by measuring changes in anodic polarization behavior during high frequency current reversal cycles of 25 cycles per second with 1 mA/sq cm current density amplitude in solutions containing Cl anions. The results demonstrated that, due to excessive polarization which affects conductivity of barrier corrosion product layers, A36 was less resistant to atmospheric corrosion than its 4130 counterpart; behavior which was also demonstrated during exposure tests

Integrated Flywheel Technology, 1983

Topics of discussion included: technology assessment of the integrated flywheel systems, potential of system concepts, identification of critical areas needing development and, to scope and define an appropriate program for coordinated activity

Electrochemical characterization of systems for secondary battery application First quarterly report, May - Jul. 1966

Screening techniques for electrode-electrolyte electrochemical systems for high energy density batterie

Energy storage in the UK electrical network : estimation of the scale and review of technology options

This paper aims to clarify the difference between stores of energy in the form of non-rechargeable stores of energy such as fossil-fuels, and the storage of electricity by devices that are rechargeable. The existing scale of these two distinct types of storage is considered in the UK context, followed by a review of rechargeable technology options. The storage is found to be overwhelmingly contained within the fossil-fuel stores of conventional generators, but their scale is thought to be determined by the risks associated with long supply chains and price variability. The paper also aims to add to the debate regarding the need to have more flexible supply and demand available within the UK electrical network in order to balance the expected increase of wind derived generation. We conclude that the decarbonisation challenge facing the UK electricity sector should be seen not only as a supply and demand challenge but also as a storage challenge. (c) 2010 Elsevier Ltd. All rights reserved

A Novel Approach to Interarea Oscillation Damping by Unified Power Flow Controllers Utilizing Ultracapacitors

This paper discusses a novel approach for damping interarea oscillations in a bulk power network using multiple unified power flow controllers (UPFCs) utilizing ultracapacitors, also known more generally as electrochemical capacitors (ECs). In this paper, a new control is introduced to mitigate interarea oscillations by directly controlling the UPFCs\u27 sending and receiving bus voltages that better utilizes the stored energy in the ECs. The results of this controller are compared with and without ECs. The proposed control provides better interarea oscillation mitigation when applied to multiple UPFCs in the 118-bus IEEE test system

Development of new test instruments and protocols for the diagnostic of fuel cell stacks

In the area of fuel cell research, most of the experimental techniques and equipments are still devoted to the analysis of single cells or very short stacks. However, the diagnosis of fuel cell stacks providing significant power levels is a critical aspect to be considered for the integration of fuel cell systems into real applications such as vehicles or stationary gensets. In this article, a new instrument developed in-lab is proposed in order to satisfy the requirements of electrochemical impedance studies to be led on large FC generators made of numerous individual cells. Moreover, new voltammetry protocols dedicated to PEMFC stack analysis are described. They enable for instance the study of membrane permeability and loss of platinum activity inside complete PEMFC assemblies. Keywords: PEMFC; Stack; Characterization; Electrochemical Impedance Spectroscopy; Cyclic Voltammetry; Linear Sweep Voltammetry

Online condition monitoring of lithium-ion and lead acid batteries for renewable energy applications

Electrochemical Impedance Spectroscopy (EIS) has been largely employed for the study of reaction kinetics and condition monitoring of batteries during different operational conditions, such as: Temperature, State of Charge (SoC) and State of Health (SoH) etc. The EIS plot translates to the impedance profile of a battery and is fitted to an Equivalent Electric Circuit (EEC) that model the physicochemical processes occurring in the batteries. To precisely monitor the condition of the batteries, Kramers-Kronig relation: linearity, stability and causality as well as the appropriate perturbation amplitude applied during EIS should be adhered to. Regardless of the accuracy of EIS, its lengthy acquisition time makes it impracticable for online measurement. Different broadband signals have been proposed in literature to shorten EIS measurement time, with different researchers favouring one technique over the other. Nonetheless, broadband signals applied to characterize a battery must be reasonably accurate, with little effect on the systems instrumentation. The major objective of this study is to explore the differences in the internal chemistries of the lithium-ion and lead acid batteries and to reduce the time associated with their condition monitoring using EIS. In this regard, this study firstly queries the methodology for EIS experiments, by investigating the optimum perturbation amplitude for EIS measurement on both the lead acid and lithium-ion batteries. Secondly, this study utilizes electrochemical equations to predict the dynamics and operational conditions associated with batteries. It also investigates the effect of different operational conditions on the lead acid and lithium-ion batteries after EEC parameters have been extracted from EIS measurements. Furthermore, different broadband excitation techniques for rapid diagnostics are explored. An online condition monitoring system is implemented through the utilization of a DC-DC converter that is used to interface the battery with the load. The online system is applied alongside the different broadband signals. The deviation in the broadband impedance spectroscopy result is compared against the Frequency Response Analyzer (FRA) to determine the most suitable technique for battery state estimation. Based on the comparisons, the adoption of a novel technique – Chirp Broadband Signal Excitation (CBSE) is proposed for online condition monitoring of batteries, as it has the advantage of being faster and precise at the most important frequency decade of the impedance spectrum of batteries

Performance analysis of batteries used in electric and hybrid electric vehicles

Hybrid electric vehicles (HEVs) and electric vehicles (EVs) are the most viable solutions to the undesirable high petroleum consumption by the present form of internal combustion engine driven vehicles. The varying requisites of HEVs and EVs have resulted in the advancement of battery technology in the area of chemical compositions such as electrode and electrolyte in addition to its electrical combination, control and protection schemes. The maximum utilization and protection of the battery is a challenge that needs to be tackled to improve its efficiency and reliability. A comprehensive study of the present battery technology has been performed in this thesis. The research is focused on battery modeling and its applications taking the complete electric drive train into consideration. Novel models and research perspectives have been proposed and analyzed. The scopes of increasing the accuracy of the present day battery management system have also been discussed

Techno-economic projections for advanced small solar thermal electric power plants to years 1990-2000

Advanced technologies applicable to solar thermal electric power systems in the 1990-200 time-frame are delineated for power applications that fulfill a wide spectrum of small power needs with primary emphasis on power ratings less than 10MWe. Projections of power system characteristics (energy and capital costs as a function of capacity factor) are made based on development of identified promising technologies and are used as the basis for comparing technology development options and combinations of these options to determine developmental directions offering potential for significant improvements. Stirling engines, Brayton/Rankine combined cycles and storage/transport concepts encompassing liquid metals, and reversible-reaction chemical systems are considered for two-axis tracking systems such as the central receiver or power tower concept and distributed parabolic dish receivers which can provide efficient low-cost solar energy collection while achieving high temperatures for efficient energy conversion. Pursuit of advanced technology across a broad front can result in post-1985 solar thermal systems having the potential of approaching the goal of competitiveness with conventional power systems

Development of an electrochemical micromachining (μECM) machine

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London.Electrochemical machining (ECM) and especially electrochemical micromachining (μECM) became an attractive area of research due to the fact that this process does not create any defective layer after machining and that there is a growing demand for better surface integrity on different micro applications such as microfluidics systems and stressfree drilled holes in the automotive and aerospace sectors. Electrochemical machining is considered as a non-conventional machining process based on the phenomenon of electrolysis. This process requires maintaining a small gap - the interelectrode gap (IEG) - between the anode (workpiece) and the cathode (tool-electrode) in order to achieve acceptable machining results (i.e. accuracy, high aspect ratio with appropriate material removal rate and efficiency). This work presents the design of a next generation μECM machine for the automotive, aerospace, medical and metrology sectors. It has 3 axes of motion (X, Y and Z) and a spindle allowing the tool-electrode to rotate during machining. The linear slides for each axis use air bearings with linear DC brushless motors and 2nmresolution encoders for ultra-precise motion. The control system is based on the Power PMAC motion controller from Delta Tau. The electrolyte tank is located at the rear of the machine and allows the electrolyte to be changed quickly. A pulse power supply unit (PSU) and a special control algorithm have been implemented. The pulse power supply provides not only ultra-short pulses (50ns), but also plus and minus biases as well as a polarity switching functionality. It fulfils the requirements of tool preparation with reversed ECM on the machine. Moreover, the PSU is equipped with an ultrafast over current protection which prevents the tool-electrode from being damaged in case of short-circuits. Two different process control algorithms were made: one is fuzzy logic based and the other is adapting the feed rate according to the position and time at which short-circuits were detected. The developed machine is capable of drilling micro holes in hard-to-machine materials but also machine micro-styli and micro-needles for the metrology (micro CMM) and medical sectors. This work also presents drilling trials performed with the machine with an orbiting tool. Machining experiments were also carried out using electrolytes made of a combination of HCl and NaNO aqueous solutions. The developed machine was used to fabricate micro tools out of 170μm WC-Co alloy shafts via micro electrochemical turning and drill deep holes via μECM in disks made of 18NiCr6 alloy. Results suggest that this process can be used for industrial applications for hard-to-machine materials. The author also suggests that the developed machine can be used to manufacture micro-probes and micro-tools for metrology and micro-manufacturing purposes.Brunel University European Commissio