Technologies

See the menu at left for discussions of individual storage technologies.

NAS Batteries

Description:
A NAS battery consists of liquid (molten) sulfur at the positive electrode and liquid (molten) sodium at the negative electrode as active materials separated by a solid beta alumina ceramic electrolyte. The electrolyte allows only the positive sodium ions to go through it and combine with the sulfur to form sodium polysulfides. 2Na + 4S = Na2S4 During discharge, as positive Na+ ions flow through the electrolyte and electrons flow in the external circuit of the battery producing about 2 volts. This process is reversible as charging causes sodium polysulfides to release the positive sodium ions back through the electrolyte to recombine as elemental sodium. The battery is kept at about 300 degrees C to allow this process. NAS battery cells are efficient ( about 89%).

 

Deployment Status:
NAS battery technology has been demonstrated at over 190 sites in Japan totaling more than 270 MW with stored energy suitable for 6 hours daily peak shaving. The largest NAS installation is a 34 MW, 245 MWh unit for wind stabilization in Northern Japan. U.S. utilities have deployed 9 MW for peak shaving, backup power, firming wind capacity and other applications; and project development is in-progress for an equal amount.

 

 

The demand for NAS batteries as an effective means of stabilizing renewable energy output and providing ancillary services is expanding. Several projects are under development in Europe, as well as in Japan and the US. Annual production capacity: 90MW, 150 MW planned in 2010

 

Developers / Suppliers:
NGK Insulators, Ltd.

Updated April 2009