The technology, which was developed at the Pacific Northwest National Laboratory, uses low-cost and sustainable synthesized molecules rather than the usual commodity metals, and could be retrofitted to existing batteries.

Flow batteries differ in both form and function to the more common lithium-ion batteries. They store their active chemicals – liquid electrolytes – in two external tanks. To generate power, these liquids are pumped into a central stack with two electrodes that are separated by a membrane. They exchange ions across this membrane, and this generates electricity. To store electricity, the process is reversed.

Flow batteries are safer and more scalable than lithium-ion batteries, and they can withstand greater temperatures or periods of idleness, which makes them well suited to storing and releasing the energy produced by renewable energy such as solar panels and wind turbines – particularly in the home.