Vanadium Redox Energy Storage

Via Utilipoint IssueAlert, a quick mention of this vanadium redox energy storage system that claims to have some remarkable properties, including a claimed 70-78% round-trip efficiency, up to 220 W/kg energy density, and a real-time energy storage ability (i.e., it charges as fast as it discharges). It does require a pump (they estimate it will need replacement every 5-7 years, ouch). All this without using heavy metals. Sweet!