Well, the flow battery looks kine of interesting. That ability to recharge just by replacing the spent electrolyte is certainly interesting. I checked Paul's link to the Wiki article. Then I came up with some problems, not necessarily with the system, but with my lack of knowledge. The energy density of the electrodes appears to me to be rather low, the highest appeared to be about 2500 W/m^2. I'm not sure that is as big a problem as it looks like at first, because with modern technology a 1 m^2 plate may have an active area that is much larger than 1 m^2, using various techniques to make the plate more of a mesh or sponge. I'm also not too sure about the energy density of the electrolyte. I don't know if the quoted energy densities are low or high. That would impact the use of flow batteries in cars. You have to have a high enough energy density that you can haul enough energy to get you where you need to go. And recharging the electrolyte at a filling station might require some large, complicated and expensive system.
So there are some questions about it. They may all be answerable, but I expect that it will take some engineering to come up with good answers.
Bill Gill
