4c524e74_y_Storage____Clean_Energy_Wonk__1
[0] Polysulfide Bromide battery [2] 15 MW demonstration project in 2003; more recent projects canceled. [3] 75%, unknown cost; [4] Regenysis, the owner of this technology, was a subsidiary of Germany’s RWE. No recent activity; the program may have been wound down. [1] 
A regenerative fuel cell based battery technology (aka “Flow Battery.) Seems have run into difficulties due to the toxicity of the chemicals involved.
Large Scale Electricity Storage. | Clean Energy Wonk
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