If you’ve been paying any attention to the renewable energy space, you’ll know that generation isn’t really the problem anymore. Solar panels are cheap, and wind turbines are everywhere. The problem is matching generation with demand—sometimes there’s too much wind and sun, and sometimes there’s not enough. Ideally, you could store that energy somewhere, and deploy it when you need it.

The answer everyone keeps reaching for is lithium-ion batteries, and they work just fine. However, there’s a competing technology that’s been quietly scaling up in the background—the vanadium flow battery.…