This ‘flow battery’ could power green homes when the sun goes down and the wind stops blowing

Date: Aug 02, 2018

With solar and wind electricity prices plunging, the hunt is on for cheap batteries to store all this power for use around the clock. Now, researchers have made an advance with a flow battery, the type of battery being developed to soak up enough excess wind and solar power to fuel whole cities. They report the discovery of a potentially cheap, organic molecule that can power a flow battery for years instead of days.

Flow batteries have the same components as the typical lithium-ion cells in your cellphone, but work in a way that allows them to be scaled up to provide megawatts. They have pairs of electrodes that convert energy stored in chemicals into electricity, and electrolytes that ferry charges from one electrode to another. But where conventional batteries package electrodes and electrolytes together in a cell, flow batteries keep them separate. Energy is stored in external tanks of charged liquid electrolytes that can be any size—which makes it easier to store large amounts of renewable power. During use, positive and negative electrolytes are pumped through the electrodes, which extract electricity, a process that is reversed during charging.

Today, flow batteries can store and discharge large amounts of electricity more safely, cheaply, and durably than lithium-ion batteries. But they still rely on relatively expensive electrolytes that incorporate vanadium metal particles. Chemists have been looking to organic compounds called quinones as an alternative. Organic-based flow batteries can be a third the cost of those that use vanadium, but they wear out after repeated charging cycles in an industry that expects them to last for a decade or more.

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