Monday, March 03, 2008

Sodium Sulfide Batteries: 1 Megawatt Storage

Renewable energy such as wind and solar have been waiting for cheap, reliable utility scale storage for decades. The sun only shines half the day on average, and the wind is apt to stop blowing at any time. Utility-scale electrical storage could provide 24 hour energy from renewables, which would make renewable energy more competitive.
Xcel Energy, (NYSE: XEL)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. ___EnergyBlog
More information on the sodium sulfide system can be found here.

For truly huge electrical storage, redox flow cells make more sense. Even so, the NaS system can certainly fill an important gap, if they prove both reliable and cheap enough.

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Blogger Snake Oil Baron said...

In addition to renewables, conventional generators might be more efficient if they could run higher during the off peak hours to store energy for higher demand times. It would all depend on whether the gain in generating efficiencies outweighed the loss of efficiency from storage.

It is quite analogous to the balancing that organisms do when they shuffle chemical energy between sources which are stable, those which are rapidly accessible and trying to maintain some efficiency by not over producing one kind only to reconvert it later. They also need to balance the degree of distribution versus centralization (blood vs fat vs liver).

11:35 AM  
Blogger al fin said...


When redox flow cell technology scales up, I expect that your solution will be used. Until then, other load leveling schemes will be necessary, such as compressed air and pumped water storage.

There is not enough production capacity at this time to do much more than modest load leveling, residential heat and storage, and renewable energy installation storage.

8:08 AM  

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