Value of NAS energy storage toward integrating wind: Results from the wind to battery project

Energy storage is a natural option toward adding the much-needed flexibility for integrating higher amounts of wind generation into the existing power system. This paper presents field results and analyses quantifying the ability and the value of Sodium Sulfur (NAS) battery energy storage toward shifting wind generation from off-peak to on-peak, limiting the ramp rate of wind farm output, and a strategy to integrate the aforementioned goals. The battery can also be considered on a system level independent of wind. It is argued that even in its capacity as a system resource independent of wind, the battery can aid integration of wind generation. Analyses quantifying the value of the battery in the energy and operating reserve markets are presented. Financially optimal locations to site the battery have also been identified. The presented research is a part of the 'Wind to Battery' project led by Xcel Energy, a major U.S. utility.