Filters
Availability
Publication Year
Resource Type
Faculty
School/Institute
Publication Search Results
Sort
Results per page
1 - 10 of 155
-
(1989)ThesisIn this project the preparation of the electrolyte for the all vanadium redox flow battery was investigated using both chemical and electrolytic reduction of ^O,- powder. Oxalic acid and SO^ reduction were found to be unsuitable as only the V(IV) state could be produced directly. With suspended powder hydrolysis, however, vanadium sulphate of any oxidation state, in this case 50% V(IV) plus 50% V(III) in sulphuric acid can readily be prepared from V^O^ powder, thus allowing a significant reduction in the cost of the vanadium battery electrolyte. Results from conductivity and electrolyte stability tests at elevated temperature have led to modification of the electrolyte composition for the vanadium redox cell, from the 2 M V plus 2 M H^SO^, originally employed, to the use of 3 M H^SO^, much higher energy efficiencies and greater electrolyte stability was demonstrated with the 3 M H^SO^ supporting electrolyte. Spectroscopy and electrolyte conductivity have been demonstrated as suitable techniques for state-of-charge monitoring. A number of electrode materials were also evaluated and a Toray graphite bonded to a carbon plastic electrode was selected for further prototype development. Energy efficiencies of between 83 and 86% were obtained for a current density of 30 mA/cm for a temperature range 5 to 45'C, and between 0 and 100% state-of-charge. A wide range of construction materials was tested for long term stability in the vanadium redox electrolyte.
-
-
-
-
(1988)ThesisThe all-vanadium redox flow cell is proposed as an alternative energy storage system, utilising the vanadium (II)/vanadium(III) and vanadium (IV)/(V) redox couples for the negative and positive half cells, respectively. Single redox flow cells with an active electrode area of up to 200 cm2 were constructed and their performance characteristics evaluated employing various electrode and membrane materials. Of the electrode materials evaluated graphite felt (RVG, Le-Carbone Lorraine) was found to maximise the kinetics of the vanadium couples while minimising 02 and H2 evolution reactions. Two membranes, namely the anion (AMV) exchange and cation (CMV) exchange (Asahi Glass Co., Japan) were evaluated and were found to meet the resistivity and selectivity requirements for redox flow cell applications. Employing the graphite felt (RVG) electrode and either a cation (CMV) or anion (AMV) exchange membrane excellent cell performance was achieved. Using 2 M vanadium solutions coulombic efficiencies of greater than 90% were achieved, voltage efficiencies ranged between 80%-85% while overall energy efficiencies of 76%-81% were obtained. The average open circuit voltage under these conditions is 1.4 volts. The high overall energy efficiency achieved for the single cells together with the simplicity and inherent characteristics of the all vanadium redox flow cell make it one of the most promising energy storage systems currently under development.
-
-
-
-
-