A sodium sulfur (NaS) or sodium sulphur battery is a molten salt battery made up of liquid sodium (Na) and sulfur (S). In recent times, sodium sulfur batteries have gained prominence as one of the most suitable long-duration battery system technologies.
Moreover, the need for a constant and reliable power supply makes sodium sulfur batteries the ideal choice for stationary energy storage due to enhanced safety, environmental benignity, large capacity, and long duration.
Keep reading this post to learn more about sodium sulfur batteries.
What is a Sodium Sulfur Battery?
It is an energy storage system (ESS) based on electrochemical charge/discharge reactions occurring between a positive electrode (cathode) and a negative electrode (anode).
While the cathode is usually made of molten sulfur (sulfur cathode), the anode is made of molten sodium.
Additionally, the electrodes are separated by a solid ceramic—sodium alumina—which also serves as the electrolyte that allows only positively charged sodium ions to pass through.
In addition, the electrolyte combines with the sulfur to form sodium polysulfides:
2Na + 4S = Na2S4
Independent heaters are integral to the battery system because the battery temperature in a sodium sulfur battery is kept at about 300–350°C to allow the reactions to process and maintain the electrodes in a molten state.
The Evolution of Sodium-based Battery Technology
Sodium sulfur batteries (NaS) are believed to have been originally developed by the Ford Motor Company in the 1960s. Subsequently, the Japanese company NGK used the technology to manufacture battery systems for stationary applications.
NGK’s (NGK Insulators) NAS battery is a large-capacity battery energy storage system with superior features, such as high energy density, large capacity, and long service life.
Furthermore, BASF Stationary Energy Storage GmbH (BASF SE) supplies containerized NAS® batteries, which can be transported easily and installed quickly at customers’ sites.
Sodium-based battery technology is believed to be a viable alternative to lithium-based batteries.
However, the quest for new solid electrolytes has focused on achieving four key requirements: easy fabrication, low cost, chemical stability, and mechanical stability.
A key finding in this context relates to Yan Yao—a professor at the Electrical & Computer Engineering department of Cullen College of Engineering—and his colleagues at the University of Houston who have developed a homogeneous glassy electrolyte.
This electrolyte enables reversible sodium plating and stripping at a greater density and makes it more viable to produce sodium ion-based batteries commercially and on a larger scale.
Consequently, the new electrolyte can help in using ambient temperature solid-state sodium-sulfur battery technology for grid-level energy storage systems.
In addition, research conducted by Dr. Shenlong Zhao and Bin-Wei Zhang contributed significantly towards developing high-performance, room temperature sodium sulfur batteries.
Experiments are being carried out further to commercialize these batteries as a powerful battery solution with four times the storage capacity of lithium-ion batteries.
According to Dr. Arumugam Manthiram, who served as the Director of the University of Texas’s Texas Materials Institute, sodium and sulfur are appealing materials for future battery production:
“With expanded electrification and increased need for renewable energy storage going forward, cost and affordability will be the single dominant factor.”
Growth Drivers of the Sodium Sulfur Battery Market
Some of the significant drivers behind the growth of the global sodium sulfur battery market include:
- A rise in demand for alternative energy storage systems due to increasing lithium metal prices.
- A rise in the number of global renewable energy storage projects, especially in America and China.
- A rise in the number of R&D projects on sodium batteries, mainly in China, India, Indonesia, and Japan.
- Growing demand for battery energy storage systems.
- Growing demand for electric charging stations with electric vehicles.
- Social and environmental pressure to reduce greenhouse gas emissions.
- Supportive government investments and policies in advanced energy storage technologies.
Advantages of Sodium Sulfur Batteries
Here are the major advantages of sodium sulfur batteries:
Depth of discharge: A key advantage is the ability of sodium sulfur batteries to discharge completely without degradation to the cell.
Energy density: The high energy density (110 Wh/kg) and power density (150 W/kg) of sodium sulfur batteries make them ideal for use in various applications.
Low-cost materials: As sodium salt is one of the most abundant elements on Earth, sodium sulfur batteries cost less than other batteries, such as lithium-ion batteries.
Disadvantages of Sodium Sulfur Batteries
The following are the main disadvantages of sodium sulfur batteries:
Operational cost: The increased operational cost of sodium sulfur batteries is due to the high temperature (350°C) required to liquefy sodium.
Production capacity: Unlike Li-ion batteries, sodium sulfur batteries are not yet established in the market. Currently, NGK is the only recognized manufacturer of sodium sulfur batteries in commercial volumes.
Safety: As the sodium sulfur batteries operate at very high temperatures, the safety risk makes them less suitable for BTM applications. Moreover, the sodium battery is highly dangerous if the liquid sodium comes into contact with water in the atmosphere.
Applications of Sodium Sulfur Batteries
The three major applications of sodium sulfur batteries include:
- Behind the meter (BTM) applications (including backup power and peak shaving)
- In front of the meter (FTM) applications (including flex ramping and renewable shifting)
- Off-grid or remote applications (including backup power in data centers and self-consumption from distributed renewable generation in islands, military areas, and remote areas)
Sodium sulfur batteries are mostly used for backup power, load leveling, and renewable energy stabilization applications.
For instance, the NaS battery system can be used as an emergency power supply during momentary voltage drops and power outages.
Blackridge Research & Consulting – Global Sodium Sulfur Battery Market Report
Blackridge Research & Consulting’s Global Sodium Sulfur Battery Market report offers deep insights into the sodium sulfur battery market across multiple regions.
The report provides a comprehensive analysis of key industry players, the emerging market trends and developments, the most influential growth drivers and restraints, and more.
According to the report, the forecast period indicates the Asia-Pacific region to be the largest market for sodium sulfur batteries.
In addition, the target of reduced emissions will lead to an increased demand for NaS batteries in the power generation sector, especially in China, India, and other Southeast Asian countries, such as Korea and Japan.
The sodium sulfur battery is a megawatt-level energy storage system with superior features, such as high energy density, large capacity, and long service life.
Sodium sulfur batteries are increasingly being used to stabilize output from wind and solar power generators.
Furthermore, NaS batteries present significant opportunities to generate clean energy at a low cost and transition to a decarbonized economy using plentiful resources like sodium, which can be processed from seawater.
Despite facing high competition from conventional batteries, sodium sulfur batteries hold great potential for residential and commercial projects and industrial applications.