Flow batteries
Batteries that keep their energy in liquid electrolytes in tanks, so capacity scales with tank size.
Storage · Electrochemical · No. 74
- Storage
- Duration: Hours to days
A battery you enlarge by adding tanks: China's biggest stores 1,000 MWh in liquid vanadium that barely wears out.
Chart: Illustration: Flow batteries
Where it comes from
Chart: Map of where it comes from
Two tanks of dissolved vanadium are pumped past a membrane where they swap electrons; the liquid does not crack or swell, so it lasts about 10,000 cycles.
Three things to know
- Because power and energy are sized separately, extra hours mean only more liquid and tanks, which suits 6 to 12 hour storage.
- Only 70 to 80% of the electricity comes back out, against about 85 to 90% for lithium-ion.
- Suppliers outside China are fragile: US firm ESS Inc lost USD 63.4 million in FY2025 and Australia's Redflow failed in 2024.
The journey
- 1 Vanadium oreMostly mined in China and Russia
- 2 ElectrolyteVanadium dissolved in sulphuric acid
- 3 TanksBigger tanks give more hours of storage
- 4 Cell stackPumped liquids swap electrons across a membrane
- 5 GridCarries solar through evening and night