or Electrochemical Flow Capacitor http://www.gizmag.com/electrochemical-flow-capacitor/23298/
"The EFCs developed at Drexel University are another step in this direction and are aimed at large scale usage. The device consists of a cell connected to two external reservoirs, each containing a mixture of electrolyte liquid and charge-carrying carbon particles. The uncharged slurry is pumped from the reservoir tanks into the flow cell, where the stored energy is transferred to the carbon particles. Once charged, the slurry can be stored in large tanks until the energy is needed, at which time the entire process is reversed." <more>
