National Geographic has an article on a large scale sodium sulphur battery being built in Texas - Texas Pioneers Energy Storage in Giant Battery.

Presidio, Texas, has one link to U.S. electrical power, stretching some 60 miles (100 kilometers) from Marfa in the high desert to the banks of the Rio Grande.

Built in 1948, the transmission line was around when Rock Hudson, Elizabeth Taylor, and James Dean walked Marfa’s streets while filming the epic movie Giant.

Electrical storms erupt frequently in the rugged expanse between Marfa, nearly one mile (1,600 meters) above sea level, and Presidio, on the Mexico border, “one of the hottest places in the nation,” in the words of city administrator Brad Newton. “It really creates a situation unique to our geographic area,” he says.

Reliance on a single aging, transmission line in this hostile terrain has made life in Presidio different than in most of the United States.

Chronic power outages and electrical fluctuations have been the norm.

And sweltering in the dark has been only part of the problem. The situation wreaks havoc with electrical devices, causing computer systems to reset frequently—an annoyance in homes and a constant worry for authorities.

“The area is a significant border crossing and for them to lose computers was not a good option,” said Calvin Crowder, president of Electric Transmission Texas, LLC, a joint venture between subsidiaries of American Electric Power and Warren Buffett’s electricity company, Berkshire Hathaway’s MidAmerican Energy Holdings.

ETT is just completing installation of a system designed to resolve Presidio’s power woes.

The hoped-for remedy is a battery, a Texas-size battery, which could eventually end up playing an important role in wider use of green power generation such as solar and wind. The U.S. $25 million system, which is now charging and is set to be dedicated April 8, will be the largest use of this energy storage technology in the United States.

The four-megawatt sodium-sulfur (NaS) battery system consists of 80 modules, 8,000 pounds (3,600 kilograms) each, constructed by the Japanese firm NGK-Locke. They were shipped to Long Beach, California, in December and transported to Texas aboard 24 trucks.

The cost of the battery system includes $10 million just to construct the building in which it will be housed and the new substation it requires.

EcoGeek has a post on a sodium sulphur battery project in Minnesota for storing wind power - Is Cheap, Efficient Storage for Wind Power Finally Here ?.

With the rise of wind power, many critics have focused on its unreliability and how there's no efficient storage available. Other companies have worked on making the turbines themselves more efficient, but so far there hasn't been a low cost storage solution. Xcel Energy is hoping that their "Wind-to-Battery" project holds that solution.

The company is testing an 80-ton sodium-sulfur battery on a Minnesota wind farm and believes that it can power 500 homes for seven hours when fully charged. The battery consists of 20 50-KW modules that are together the size of two tractor trailers and can store 7.2 MWh.

The project is the first in the country to test the storage of wind power and while 500 homes isn't even a dent in the amount of homes that would need to be powered, it will give the company a good indication of how this type of storage could be expanded if the test is successful.

Jim at The Energy Blog has a post on using sodium sulphur batteries to store energy from wind farms in Minnesota.

Xcel Energy, in partnership with the University of Minnesota, the National Renewable Energy Laboratory and the Great Plains Institute, will soon begin testing a one-megawatt sodium-sulfur battery storage system to demonstrate its ability to store wind energy and dispatch it to the electricity grid when needed.

Fully charged, the batteries could power 500 homes for six and one-half hours. Xcel Energy will purchase the batteries from NGK Insulators, Ltd. that will be an integral part of the project. The sodium-sulfur battery is commercially available and versions of this technology are already being used in Japan and in a few US applications, but this is the first U.S. application of the battery as a direct wind energy storage device.

The 50-kilowatt battery modules, 20 in total, will be roughly the size of two semi trailers and weigh approximately 60 tons. They will be able to store about 6.5 megawatt-hours of electricity, with a charge/discharge capacity of one megawatt. When the wind blows, the batteries are charged. When the wind calms down, the batteries can be used to supply energy to the grid as needed.

"Energy storage is key to expanding the use of renewable energy. This technology has the potential to reduce the impact caused by the variability and limited predictability of wind energy generation."

-- Dick Kelly, Xcel Energy chairman, president and CEO.

The project will take place in Luverne, Minn., with the battery installation beginning this spring adjacent to a nearby 11-megawatt wind farm owned by Minwind Energy, LLC. Testing will begin in October and is expected to last up to two years.

Commercial projects are now underway that use flow batteries, compressed air energy storage, thermal energy storage, pumped hydro, and sodium sulfur batteries for energy storage in connection with renewable energy projects. American Electric Power (AEP) is also using NaS batteries in a couple of their systems, but not in connection with wind power. While not enough experience has been gained with any of these technologies to make any decision as to which technology is best under what conditions, pumped hydro and sodium sulfur batteries are the most well proven and thus seem to be the first choice of electric utilities. Thermal storage is gaining acceptance for use with thermal solar systems, the only energy technology that it is suitable for use with. As Mr. Kelly stated, energy storage is essential to widespread use of renewable energy technologies.