To: Jim Bishop who wrote (118696 ) 9/3/2003 7:47:04 PM From: Tom Swift Read Replies (3) | Respond to of 150070 There is a real need for some sort of energy storage suited for the grid. However, I would not get excited about vanadium-flow batteries. If you look at the references cited in the link below, you will see that this is a fairly old idea (~1985).The main drawback of the VRB for electric vehicle applications, however, is its relatively low energy density compared with nickel metal hydride or lithium batteries. The energy density of a redox flow battery is related to the concentration of the redox ions in solution, on the cell potential and the number of electrons transferred during discharge per mole of active redox ions. In the all-vanadium redox flow cell, the present energy density is 25 Wh/kg, this being based on a maximum vanadium ion concentration of 2 M or less for wide temperature range operation. This concentration represents the solubility limit of the V(II) and/or V(III) ions in the sulphuric acid supporting electrolyte at temperatures below 5 oC and the stability of the V(V) ions at temperatures above 40 oC. ceic.unsw.edu.au Basically, this means that the vanadium battery can't compete performance-wise with Li-Ion or NiMH technologies in small and medium-sized applications. In fact, 25 Wh/kg is a little worse than lead acid batteries. That means that commercialization requires a step function advance to multi-megawatt installations -- not likely. The interesting aspect is the possibility of instant charge like a fuel cell. However, like the fuel cell, there is no infrastructure in place for charging these beasties which is a real challenge. Here is a Sandia link list for energy storage technology:sandia.gov If you click on the VRB link, you get the list of players:electricitystorage.org This technology appears to be real, I just don't find it exciting. If it was a 500-Lb gorilla, it would have been implemented 20 years ago.