Note to players: Description acceptable. One technology for this purpose has an “advanced adiabatic” variant that has yet to achieve viability. Various devices that serve this purpose can be compared using a Ragone plot. One type of device used for this purpose relies on the formation of a double layer on two coatings of activated (-5[1])carbon and is called an EDLC. Another system for this purpose uses magnetic bearings to levitate a (*) flywheel. Round-trip efficiencies between 70-80% are achieved by “pumped” systems for this purpose, which hold water at two different elevations to deal with load (10[1])fluctuations. Technologies for this purpose are needed because, for many renewables, peak demand and peak production occur at different times. (10[1])For 10 points, name this process performed by hooking up a power plant to a grid of rechargeable batteries. ■END■ (10[1])