Introduction: An energy storage system (ESS) is not just batteries but a comprehensive system that integrates electrochemical, power electronics, digital, and thermal technologies. As the penetration of renewable energy keeps increasing, we are seeing an explosive growth in the energy storage market. With this expansion, safety has become a crucial industry issue.

SHENZHEN, China, Nov. 28, 2022 /PRNewswire/ -- ESS plays a key role in new energy systems, prompting rapid market growth around the world. Wood Mackenzie's report shows global energy storage capacity could grow at a compound annual growth rate (CAGR) of 31%, recording 741 gigawatt-hours (GWh) of cumulative capacity by 2030. This being said, occasional safety accidents persist at battery energy storage plants, putting staff at risk and causing serious economic losses.

Lithium batteries are the core components of a battery energy storage system (BESS). Internal and external sources may quickly increase the temperature of battery cells, leading to thermal runaway. This can release flammable and explosive gases, causing fires or even explosions. Normally, there are several issues that may lead to safety accidents in lithium BESSs:

• Manufacturing defects, short circuits due to lithium plating, and battery cell inconsistency
• Circulating currents between lithium battery racks, accelerating battery cell deterioration
• External short circuits caused by insulation failures, internal short circuits caused by abnormal currents and overheating
• External environmental changes, such as high temperature and high humidity, accelerating lithium battery aging and causing insulation failures and short circuits, resulting in thermal runaway
• Battery monitoring failure due to improper configuration & coordination, or incomplete information sharing between the Battery Management System (BMS), Energy Management System (EMS), and Power Conversion System (PCS)

To ensure the safety of the entire ESS, it requires refined monitoring and management of batteries not only from system level, but also from rack level, pack level, and even cell level. By leveraging decades of extensive R&D investment and practical application of in electrochemical, power electronics and digital technologies, FusionSolar has pioneered the Smart String ESS Solution which features innovative battery pack & rack level optimization, as well as multi-level safety protection with refined monitoring and charge/discharge management of the ESS, achieving higher available battery capacity and increased safety.

FusionSolar Smart String ESS Solution adopts multiple levels of safety design for ultimate protection.

• Structural Safety
  The solution design isolates the batteries, rack-level optimizers, and fire control cabins to ensure stable, ongoing monitoring and fire protection. The protection rating of the entire system reaches IP55, the anti-corrosion level of the container is C5, and the system can withstand earthquakes up to a magnitude of 9.

• Electrical Safety
  Four-level active control and two-level physical isolation provide comprehensive overcurrent protection -- when detecting overcurrent, the system triggers the BMS to limit the current of battery packs and racks from the software side. If the fault is escalated, the battery pack & rack optimizers will shut down the system from the hardware side ('four-level'). Finally, the circuit breaker and fuse will help prevent the fault spreading from system level ('two-level'). In addition, when the ESS is not running, for example, during transportation or installation, the voltage of the battery pack terminals is zero, helping to protect construction and O&M personnel from accidents.

• Fire Safety
  FusionSolar Smart String ESS Solution is equipped with multiple temperature, humidity, and smoke sensors. These sense warning factors in the environment. For example, if they detect flammable gas, the sensors automatically exhaust the gas to prevent fire and explosions. After the exhaust system is shut down, an extinguishant is immediately released to put out the fire and prevent the accident from escalating.

• AI-based BMS Intelligent Alarming
   The solution uses an innovative patented AI-based short-circuit algorithm, which can intelligently detect internal short-circuits on the battery cell level, enabling early detection, early warning, and multi-level linkage protection.

Safety is always the top priority and is critical as we aim toward carbon neutrality. FusionSolar is committed to provide safer and more reliable ESS solutions by continuing to increase R&D investment and draw on the rich experience in power electronics, thermal, AI, and digital technologies, and will also continue working with customers and industry partners to accelerate carbon neutrality for a greener future.