Sodium–sulfur battery
This is because of the square–cube law: large cells have less relative heat loss, so maintaining their high operating temperatures is easier.
An essential part of the cell is the presence of a BASE (beta-alumina solid electrolyte) membrane, which selectively conducts Na+.
[11] Stationary NaS batteries by NGK Insulators use hermetically sealed cells and multiple safety features on module level, such as sand for fire suppression.
[12] During the discharge phase, molten elemental sodium at the core serves as the anode, meaning that the Na donates electrons to the external circuit.
The sodium is separated by a beta-alumina solid electrolyte (BASE) cylinder from the container of molten sulfur, which is fabricated from an inert metal serving as the cathode.
To tackle this challenge, case studies to couple sodium–sulfur batteries to thermal solar energy systems.
[14] The heat energy collected from the sun would be used to pre-heat the cells and maintain the high temperatures for short periods between use.
Once running, the heat produced by charging and discharging cycles is sufficient to maintain operating temperatures and usually no external source is required.
Early on the morning of September 21, 2011, a 2000 kilowatt NaS battery system manufactured by NGK Insulators, owned by Tokyo Electric Power Company used for storing electricity and installed at the Tsukuba, Japan Mitsubishi Materials Corporation plant caught fire.
The additional safety measures implemented mean that the occurrence of incidents with consequences similar to those which occurred in 2011 and earlier (thermal runaway of complete modules, fires) can reasonably be excluded.
Despite the low materials cost, these batteries were expensive to produce, as the economy of scale was not achieved during that time.
The lower operating temperature allowed the use of a less-expensive polymer external casing instead of steel, offsetting some of the increased cost associated with using caesium.
A consortium formed by TEPCO (Tokyo Electric Power Co.) and NGK Insulators Ltd. declared their interest in researching the NaS battery in 1983, and became the primary drivers behind the development of this type ever since.
TEPCO chose the NaS battery because all its component elements (sodium, sulfur, and alumina) are abundant in Japan.
The first large-scale field testing took place at TEPCO's Tsunashima substation between 1993 and 1996, using 3 x 2 MW, 6.6 kV battery banks.
The 80 tonne, 2 semi-trailer sized battery is expected to have 7.2 MW·h of capacity at a charge and discharge rate of 1 MW.
[26] Since then, NGK announced several large-scale deployments including a virtual plant distributed on 10 sites in UAE totaling 108 MW/648 MWh in 2019.
[27] In March 2011, Sumitomo Electric Industries and Kyoto University announced that they had developed a low temperature molten sodium ion battery that can output power at under 100 °C.
Sumitomo Electric Industry CEO Masayoshi Matsumoto indicated that the company planned to begin production in 2015.
[29] There are several degradation pathways: NaS batteries can be deployed to support the electric grid, or for stand-alone renewable power[40] applications.
[42] In 2016, the Mitsubishi Electric Corporation commissioned the world's largest sodium–sulfur battery in Fukuoka Prefecture, Japan.
These insoluble polysulfides form as dendrites on the anode which can damage the battery and interfere with the movement of sodium ions into the electrolyte.
