There's discussion of that in the comments [1]. It looks like it's referring to the storage capacity. [1] http://spectrum.ieee.org/energywise/energy/the-smarte

There's discussion of that in the comments [1]. It looks like it's referring to the storage capacity. [1] http://spectrum.ieee.org/energywise/energy/the-smarter-grid/new-flow-battery-aims-to-replace-gas-plants#comment-1400912704 http://spectrum.ieee.org/energywise/energy/the-smarter-grid/...