Facts have shown that battery energy storage systems are essential for the integration and development of clean energy, but require more advanced fire safety protection measures. The senior engineer of SES Power with 20 years of experience in the lithium battery industry analyzed and explained the reason why exhaust gas detection is an important line of defense to prevent battery thermal runaway.

　　Wind power facilities, solar farms, microgrids, data centers and telecommunications facilities have at least one thing in common: They rely on battery energy storage systems (BESS) composed of thousands of lithium-ion batteries. Battery energy storage systems not only play a key role in the transition to renewable energy and smarter grids, but have become a key component of data centers and telecom hubs.

　　According to the survey, the global utility-scale battery energy storage system market is valued at $2.9 billion in 2020 and is expected to grow at a CAGR of 32.8% from 2020 to 2025, reaching $12.1 billion by 2025. That number more than doubles when you include uninterruptible power supplies (UPS) in data and telecom centers, vehicle charging facilities, and other energy storage applications. The total global energy storage market is expected to grow from $7.8 billion in 2020 to $26.8 billion in 2028.

　　Why are lithium-ion batteries the preferred battery energy storage technology? First, they are relatively inexpensive and provide higher energy density due to their size and weight; they have a longer continuous discharge time; they are less prone to self-discharge than other types of batteries; and require little maintenance, and does not require regular exhaust emissions.

　　Despite the multiple advantages of lithium-ion batteries, there are also some disadvantages. On the one hand, lithium-ion battery energy storage systems require sophisticated battery management systems (BMS) to maintain operation within safe parameters of voltage, temperature, and charging. If mismanaged or abused, the battery can fail, cause venting or overheating, and if the battery catches fire (thermal runaway), it can quickly escalate into a catastrophic fire, or even an explosion, which is extremely difficult to extinguish and can be extinguished with dominoes The domino effect accelerates diffusion to surrounding batteries.

　　A: Three stages of battery failure

　　• Abuse factor

　　Electrical abuse occurs when battery voltage limits are exceeded during charging or discharging. Because a large number of cells in a battery energy storage system are charged or discharged at the same time, the risk of electrical abuse of a single cell increases. Thermal abuse occurs when operating temperatures exceed the battery's endurance limit. Mechanical abuse refers to physical damage such as crushing, indentation or puncture.

　　• Battery exhaust (exhaust gas)

　　If the abuse factor continues, the liquid electrolyte in the battery will convert to a gas, which will cause the internal pressure of the battery to increase enough to open the pressure relief hole or break the battery seal. This outgassing is distinct from the outgassing after thermal runaway occurs, and typically occurs several minutes before thermal runaway.

　　• Thermal runaway

　　As the temperature inside the battery rises, the separator will melt and rupture, releasing fumes and igniting the electrolyte. Gases emitted during this phase typically include carbon monoxide (CO), carbon dioxide (CO2) and combustible gases. The resulting fire can generate temperatures above 1,000°C and spread to surrounding batteries, causing them to enter a thermal runaway state that can cause the entire system to fail and catch fire.

　　(Smoke and exhaust gas detection and monitoring sensors installed on the top of the lithium-ion battery energy storage system)

　　B: Challenges brought by battery energy storage systems to traditional monitoring technologies

　　Battery energy storage systems require a battery management system (BMS) to monitor voltage, current, and temperature and prevent battery abuse, but relying on a battery management system (BMS) as the only layer of defense against thermal runaway is risky. Because the battery management system (BMS) cannot resolve the temperature or voltage of a single battery. Even with temperature sensors on each battery, there may be undetected hot spots.

　　Traditional monitoring techniques, such as smoke and fire detection, carbon monoxide (CO) monitoring, carbon dioxide (CO2) monitoring, lower explosion limit (LEL) monitoring, are part of the safety solution for battery energy storage systems.

　　Smoke and fire are generally not produced, and carbon monoxide (CO), carbon dioxide (CO2), and lower explosive limit (LEL) gases are generally not present in detectable concentrations until thermal runaway begins.

　　In short, these techniques are passive responses to thermal runaway rather than active prevention. Even if a battery has reached the point of smoking or catching fire, it may be too late to stop its fire from spreading to surrounding batteries.

　　C: Initial exhaust (exhaust) detection before thermal runaway

　　Detecting early signs of lithium-ion battery failure and then responding proactively with early monitoring data is critical to preventing thermal runaway and explosive fires.

　　To evaluate the response time of lithium-ion batteries in detecting early signs of potential thermal runaway, a study by the safety agency DNV tested three technologies: exhaust gas sensors, battery voltage sensors, and lower explosion limit sensors.

　　Of the three types, exhaust gas detectors have the highest sensitivity and accuracy. They had an average response time of less than 10 seconds after the onset of exhaust gas emissions and 6 minutes and 11 seconds before the onset of thermal runaway. Neither the LEL nor the voltage sensor is active until thermal runaway starts.

　　The findings also show that system shutdown measures combined with exhaust gas detection are effective in preventing thermal runaway. Once exhaust gas is detected, the battery energy storage system automatically shuts down to prevent the battery temperature from rising, thereby preventing thermal runaway from spreading to adjacent cells.

　　Benefiting from globalized energy conservation and emission reduction, the construction of clean energy has gradually entered an outbreak period, which has also led to an increase in supporting energy storage systems. The ternary lithium battery with high energy volume ratio has more energy than the lithium iron phosphate battery, but the safety is superior to the lithium iron phosphate. SES Power has been working hard in this market segment for a long time and has launched, such as 12V100Ah, 12V200Ah, 24V100Ah, 24V200Ah, 36V100Ah, 48V50Ah, 48V100Ah, etc. using square aluminum-shell lithium iron phosphate cells. It can be said very sincerely that the competition in this market is more intense than that of electric vehicle batteries. Many customers are very concerned about cost performance. SES Power recommends that customers use lithium iron phosphate ladder batteries first, which can ensure a price advantage. However, SES Power suggests that the customized echelon lithium-ion battery pack must add more functional investment in safety performance. These investments do not actually account for much of the cost of this customized lithium-ion battery pack, but it can greatly improve safety. sex.