IF WE’RE EVER to run our electric grid on the on-again, off-again power that wind and sun provide, we’re going to need better batteries. Here’s an option.

In place of the solid electrodes of a conventional battery, flow batteries use two liquid electrolytes that react when pumped through a cell stack. The battery is broken down into a cell stack and two large electrolyte tanks; as the electrolyte flows past a porous membrane in each cell, ions and electrons flow back and forth, charging or discharging the battery.

Voltage and current capacity are defined by the chemical reaction used and the number, size, and connection of the individual battery cells. Energy storage capacity is defined by the size of the electrolyte storage tanks. Recharging simply means reversing the current flow - or putting in fresh electrolyte.

More here.