One of the Harvard researchers, Michael Aziz, looking very pleased.

 Similar to both a battery and a fuel cell.  Energy stored in the electrolyte instead of the electrodes.  Capacity for energy storage is independent of power handling capacity.  High storage capacity retention per cycle.

 Uses Bromine and 9,10-anthraquinone-2,7-disulfonic acid (AQDS).  Metal-free molecules are larger and cheaper.  Each molecule holds two units of electric charge, allowing twice the energy storage per unit volume over the one unit available in metal-based flow batteries.

 The target cost of making a storage system feasible is $100 per kW-hr.  Lead-acid batteries cost about $250 per kW-hr.  Vanadium flow batteries cost $700 per kW-hr.  It is too early to determine the total cost of a metal-free flow battery but the cost of the electrolyte is about 1/3 that of vanadium. Vanadium contributes $81 per kW-hr to the total cost while AQDS/bromine costs only $27 per kW-hr. Still much remains to be done to bring the cost down.