Flow cells could provide cheaper green energy storage

Particularly suited to storing large amounts of energy, flow cells can be linked into electrical distribution grids and can be sized to meet a wide range of power requirements. The project, led by Michael Aziz of the Harvard School of Engineering and Applied Sciences, aims to reduce the cost of this technology so that it can compete with current solid battery systems, which are cheap but limited.

Flow cells work by pumping liquid electrode materials, which carry positive and negative charges, through an electrochemical conversion cell — similar to a fuel cell — which generates electrical current. Pumping the liquids in the opposite direction while supplying current to the cell recharges the battery. The amount of power the cell can produce is dictated by the size of the electrochemical cell, while the amount of energy it can store depends on the volume of the electrode materials in the system, which are held separately from the cell in external tanks.