Presidio NaS Battery Project

The ETT sodium-sulfur ("NaS") battery system is the first in Texas and the largest in the United States and represents an investment by ETT to improve transmission reliability in Presidio, Texas and surrounding areas.

Since it was energized in March 2010, the NaS battery system has provided improved power quality and reduced momentary outages caused by voltage fluctuations. In the event of a transmission outage, the battery system is capable of automatically deploying to provide backup transmission power.

In addition to the battery system, other Presidio-area reliability improvements include the addition of the Gonzales substation and a 60-mile, 69-kV transmission line from Marfa, Texas to Presidio, Texas. The battery will allow the transmission line into Presidio to be taken off line while maintaining critical services to the community.

With the installation of this NaS battery system, Presidio, one of the oldest cities in the United States, is benefiting from one of the world's newest technology developments and electrical service for our customers in this region has been enhanced.

The battery system is controlled through an S&C Electric Company Smart Grid Storage Management System,™ a fast-response, automatic power converter and controller that provides the ability to store energy in a variety of battery storage technologies and to control the discharge of that power into the electrical grid.

AEP pioneered the use of the NaS battery in the United States. Following testing at its Dolan Technology Center near Columbus, Ohio, AEP became the first U.S. company to deploy NaS batteries when it installed and operated a demonstration unit in Gahanna, Ohio, in 2002.

The NAS battery system uses sodium-sulfur battery technology and provides the following benefits:
  • Due to its quick response, the battery addresses voltage fluctuations and momentary outages.
  • In the event of an outage on the radial transmission line providing power to Presidio, the battery can supply four megawatts of uninterrupted power for up to eight hours.
  • The battery allows for maintenance on the new transmission line between Marfa and Presidio without loss of electric service.
NaS Battery Overview (PDF)
March 26, 2010 National Geographic Article