As the renewable energy industry grows and becomes a larger part of our energy mix, the concept of energy storage has made its way into the spotlight and has created some important pressing questions: Do renewables' inherent intermittency require some kind of energy storage, and should it be at the endpoint of use or closer to the utility (or both)? Do we even need an "energy storage" application, or can grid flexibility and responsiveness assume this role? If energy storage is indeed embraced, how should we weigh the options?
Pike Research says nearly 56 gigawatts of "long-duration" bulk energy storage for the grid will be installed from 2012-22. Installations of energy storage for "ancillary services" alone (things like scheduling and dispatch, reactive power and voltage control, system protection) will increase more than tenfold to surpass 3.5 GW in that timeframe.
We recently ran a story looking at several of these options, and some companies with new technologies in each area. Pumped hydro has been the go-to energy storage option proven to work at fully deployed grid scale. Compressed energy, meanwhile, is fairly cheap where it can be deployed appropriate to grid-scale applications, using geological formations (caves or caverns) that can be relatively well sealed off.
Batteries are getting some utility-scale attention now, too. Duke Energy's 153-MW Notrees wind power project has a 36-MW battery storage system courtesy of Xtreme Power to deploy reserve power and help both the system operator and the grid balance supply and demand. Elsewhere in Texas, Xtreme is working with Samsung SDI to provide a 1 MW/1MWh lithium-ion-based battery energy storage system as part of a $27 million "Smart Grid Demonstration Project". In the U.K., S&C Electric and Scottish and Southern Energy Power Distribution have commissioned a pilot project with three single-phase 25 kWh lithium-ion batteries.
Battery technology is fast becoming "one of the favored options for grid-scale energy storage," says Aaron Feaver, CTO of EnerG2. It "has been deployed semi-successfully in grid-scale installations" such as backup power on hospitals, data centers and renewable energy sites. It's extremely low-cost/kWh, though shortfalls in cycling and power mean batteries need to replaced every few years or even months. The beauty of batteries, though, is that the technology is ripe for cost and performance improvements, and generally speaking it can be added anywhere. Pumped hydro "works only when you have a hill," he says, while compressed storage needs leak-proof caves or caverns (though some new entrants claim to use pipes instead).
Next page: Can batteries be improved?