Energy Storage: enabling a shift away from baseload generation

Rachel Johnson explores the current state of energy storage technologies and their role in facilitating the greater use of wind power.

When the wind blows in a remote corner of Minnesota, near the Iowa border, the local wind farm in Luverne powers up and delivers electricity to the local grid. Like all wind developments, it is dependent on the forces of nature to deliver its payload, but unlike most wind farms, it is now also able to power up the network on a calm day when the turbines are still.

This unusual capability is provided through a set of 20 sodium sulphur batteries, attached directly to the 11MW wind farm as part of an experiment carried out by Midwest utility Xcel Energy and the wind farm operator Minwind Energy.

Capable of storing up to 7.2MWh of electricity on a windy day, the batteries can discharge up to 1MW of electricity at a time, enough for 500 homes for four hours.

“The Minnesota test is the first direct wind-to-battery storage installation in the United States, meaning that the battery is connected directly to the wind farm,” says Patti Nystuen, at Xcel Energy. “This test show the technology works.”

By investing in battery technology, Xcel Energy is hoping to become a player in a global utility energy storage market that is estimated to be worth US$$4.8bn in 2010. Encompassing bulk storage technologies such as pumped hydro, and compressed air energy storage (CAES), fast response units such as flywheels and supercapacitors, and batteries ranging from traditional lead acid up to hydrogen and advanced flow cells, the energy storage market is expected to reach the US$10bn mark in 2015.