Short news on NAS batteries

NGK’s NAS batteries are restarting

Existing NAS batteries systems are rebuilt by NGK Insulators Ltd. to reduce potential fire risk. Slowly, but surely, the fire incident of September 21, 2011, becomes a classified event.

xcel-energy-logoFor instance, Xcel Energy now announces it is restarting its battery plant that was commissioned in 2008 and stopped on NGK recommendation after the fire incident in Japan.

GE continues to massively hire storage experts

geThere are still ten open job positions related to Durathon on GE web site. There is even one in Japan for a Field Services Engineer, in the middle of NGK playground.

More than ever, a leading technology for grid applications

sodiumIn a recent article “Dynamic Modelling of Advanced Battery Energy Storage System for Grid-Tied AC Microgrid Applications“, researchers concludes:

“Sodium sulfur-type BESS devices are best suited to the requirements set by modern microgrid applications. These batteries can act in contingencies where rapid action is required to maintain the adequate levels of the grid frequency, but also in the case of high penetration of renewable generation, such as wind or solar photovoltaic, since the NaS battery can operate as the perfect complement in valley hours. In this case, the excess energy can be stored for delivery in peak hours. They are environmentally safe and have low maintenance while operate at high temperatures; it does not represent a major drawback. The biggest drawbacks are the cost and the limited information about these type of batteries which difficult the development of experimental prototypes and computer models. It is expected however that the appearance of other vendors reduces costs and facilitate the modelling.”

It is one of the numerous independent studies that recognise the advantages of NAS compared with other technologies for grid storage solutions.

Gauthier Dupont
Dupont Energy Consulting GmbH

NGK’s NAS batteries long recovery


  • September 21, 2011 : Fire incident at the Tsukuba Plant, Joso City, Ibaraki Prefecture, Japan
  • September 22, 2011 : announcement of the event on NGK’s website
  • October 5, 2011 : fire authorities confirmed that the fire had been extinguished
  • October 25, 2011 : NGK requests all NAS batteries facilities to be stopped or to restrict their usage (after agreement with NGK)
  • October 28, 2011 : All shipments are officially postponed & business forecast is revised
  • November 24, 2011 : NGK publishes a Q&A on its website
  • June 7, 2012 : NGK explains the causes of the fire incident and countermeasures
  • From June 2012 : upgrade of existing batteries facilities
  • October 2012 (?) : batteries production resumed

Small cause, big effects

After months of silence, NGK finally communicates on June 7th, 2012, about the NAS battery fire incident. The cause: a single faulty cell. One of 15,360 cells composing a 2 MW block. The solution: safety enhancement. No need for design change. Big incident, easy solution.


Since June 2012, existing NAS batteries facilities are, one after the other, upgraded to safety enhancement, by implementing following measures to prevent the spread of fire in modular batteries :

  • Fuses between battery cells
  • Insulation boards between blocks in battery modules
  • Anti-fire boards above and below battery modules.

The two first measures requires about 6000 battery modules from 174 locations in Japan, France, Germany, UAE, UK and USA to be collected in NGK facilities in Japan and then shipped back.

Along with additional safety measures (improved fire monitoring system, installation of fire extinguishers and fire-prevention equipment), as well as facilities organisation improvement (setup of a fire-fighting structure on site and of a fire evacuation route, with guidance system).

Production of new batteries 

New batteries would be produced at the earliest in October 2012. Business development perspectives are nevertheless maintained, mainly because NGK niche market is waiting for their batteries. unless GE’s Durathon shows up…

Gauthier Dupont
Dupont Energy Consulting GmbH

NAS Batteries back in the race soon ?

The biggest battery storage system in the world…

Tohoku Electric Power Co. Inc. set up a sodium sulfur (NAS) storage system at its Noshiro fossil-fuel-burning power plant. The system comprises forty 2 MW NaS batteries from NGK Insulators Ltd. able to continuously supply 80 MW for six hours. When it will be operational, it will be the biggest battery storage system in the world.

The system aims to prevent blackout in summer, thanks to load leveling (the batteries are charged during the night when the load is low and discharged in the afternoon during peak load hours). Tohoku EPCo is indeed unable to supply enough power because of the damage caused by the earthquake of March 11, 2011 (the one with the tsunami and Fukushima nuclear disaster).


It was expected to be running in January 2012, but because of the fire incident that occurred on September 21, 2011, the commissioning is postponed to April.

This announcement looks innocent, but it tells us that it seems that NGK is close to solve the problems raised by the fire incident.

Gauthier Dupont
Dupont Energy Consulting GmbH