Storing megawatts: Liquid metal batteries and electricity

Making aluminum requires a lot of electricity. That's because the metal bonds tightly to oxygen and it takes a lot of energy to break that bond. In essence, the process of making aluminum is a giant battery with the silvery metal being reduced to purity at the cathode while oxygen bonds with the carbon anode to make, you guessed it, CO2. It takes roughly 15 kilowatt-hours of electricity to make just one kilogram of aluminum via electrolysis. [More]

Source: Scientific American - Alternative Energy Technology