VFB Maintenance Methods: Technical and Economic Issues

The VFB system has been extensively studied for almost 30 years. Several plants are installed around the world, with power and energy exceeding some MW and some MWh respectively and new companies are entering the growing market. However, a real widespread application of this technology is hindered by its high capital cost. One method to make these batteries more competitive on the market is to increase their cyclability by means of appropriate maintenance procedures. Some procedures are focused on physical treatments such as the remixing of the positive electrolyte with the negative one, which causes heat generation. Other methods are focused on chemical and electrochemical regeneration procedures which make use of chemical reducing agents, catalysts or electrochemical processes. The latter requires the use of an electrolysis system in order to restore the vanadium oxidation state to the correct ratio in the positive and negative electrolyte. In the first part of this work, an extensive description of VFB technology is presented while in the second part a description of the most important and realizable maintenance procedures with their impact on the system cost is shown, considering both operative and economical points of view.