grid scale energy storage

ares energy storage technology employs a fleet of electric traction drive shuttle-trains, operating on a closed low-friction automated steel rail network to transport a field of heavy masses between two storage yards at different elevations.

during periods where excess energy is available on the grid, ares shuttle-trains draw electricity from the grid, which powers their individual axle-drive motors, as they transport a continuous flow of masses uphill against the force of gravity to an upper storage yard.  when the grid requires energy to meet periods of high demand, this process is reversed.  the shuttle-trains provide a continuous flow of masses returning to the lower storage yard with their motors operating as generators, converting the potential energy of the masses elevation back into electricity in a highly efficient process.
 
ares facilities integrate significant recent advances in motor/generator traction drive and power control technologies with proven rail technology to produce a reliable and highly capable system that approaches an 80% charge / discharge efficiency. 

the facilities are highly scalable in power and energy ranging from a small installation of 100mw with 200mwh of storage capacity up to large 2-3gw regional energy storage system with 16-24gwh energy storage capacity.

today’s flow batteries pump two different liquids through an interaction chamber where dissolved molecules undergo chemical reactions that store or give up energy. the chamber contains a membrane that only allows ions not involved in reactions to pass between the liquids while keeping the active ions physically separated. this battery design has two major drawbacks: the high cost of liquids containing rare materials such as vanadium – especially in the huge quantities needed for grid storage – and the membrane, which is also very expensive and requires frequent maintenance.

the new stanford/slac battery design uses only one stream of molecules and does not need a membrane at all. its molecules mostly consist of the relatively inexpensive elements lithium and sulfur, which interact with a piece of lithium metal coated with a barrier that permits electrons to pass without degrading the metal. when discharging, the molecules, called lithium polysulfides, absorb lithium ions; when charging, they lose them back into the liquid. the entire molecular stream is dissolved in an organic solvent, which doesn’t have the corrosion issues of water-based flow batteries.