In response to climate change, countries around the world are committed to develop renewable energy and switch to EVs to promote clean energy and tackle global warming. To ensure power grid stability, demand for large stationary energy storage systems (battery cabinets) has increased rapidly. However, several fire and explosion incidents in connection with energy storage systems have made people realize that the road to renewable energy is not as smooth as one would hope, and that more challenges likely await. Making energy storage systems safer, ensuring safety in product design and production to avoid similar incidents, and adopting damage control and loss reduction mechanisms in the event of a disaster are all aspects that need to be considered and improved upon. Otherwise, public acceptance of power facilities such as energy storage systems would be affected to the detriment of the use and promotion of clean energy.
Analyzing the characteristics and cause of fire in connection with energy storage systems: Preventing fire propagation
Major fire incidents involving energy storage systems have been reported recently in several countries. For example, the Arizona Public Service (APS) electric utility experienced a battery fire in April of 2019, causing injuries to four firefighters and first responders. A pilot-stage lithium-ion (Li-ion) battery energy storage cabinet beneath the Minquan Bridge in Neihu District, Taipei City, caught fire in July 2020 and took firefighters more than three hours to bring under control. In April 2021, a sudden explosion occurred without warning at Beijing’s largest solar PV energy storage-charging station—the Jimei Home Dahongmen Power Station—leading to the death of two firefighters. At the end of July 2021, a fire spread across Tesla and Neoen’s giant energy storage system in Geelong, Australia, during initial testing, and this burned for almost four days before it was extinguished.
Based on these reports and post-event investigations, a few basic facts about fire in Li-ion battery energy storage systems and characteristic differences from general fire incidents can be derived:
- Li-ion phosphate battery (or LFP battery) is considered the safe choice among all Li-ion batteries, but recent events have proved otherwise. The most recent case at the Jimei Home Dahongmen Power Station involved an LFP battery. Battery system safety is affected by the cathode materials used as well as other battery components, such as the separator film and electrolytes, in addition to voltage, current, and temperature control systems, and system implementation and engineering considerations.
- Li-ion battery energy storage systems are battery modules and cabinets composed of tens of thousands of batteries. Internal or external short circuits in Li-ion batteries can lead to thermal runaway, triggering a series of chain reactions that fuel the spread of fire to other batteries, thereby further increasing the risk of a sudden explosion. Clean-agent fire suppression systems cannot effectively extinguish Li-ion battery fires. Any energy storage system is not safe from a fire hazard even if it has passed the UL 9540A, which is widely considered the most rigorous test method available.
- Three of the four major fire incidents mentioned above all occurred during initial testing (the APS electric utility in Arizona had been operating for over two years), indicating that environmental control and human factors during system testing are imperative.
Delta’s solution for energy storage system safety: Multi-level protection and barriers
The approach to preventing and analyzing the underlying cause of fires in energy storage systems needs to be strengthened by formulating stricter product safety standards and addressing possible flaws in battery design and production stage. Government fire prevention regulations, training on fire prevention equipment and firefighting practices, and fire drills should focus on the special characteristics of fires in energy storage systems. As a global leader in power and thermal solutions, Delta provides the following energy system solutions from a system design and management perspective:
- Battery safety detection design: According to APS’s incident report, the fire was caused by abnormal lithium metal deposits penetrating a separator film, which led to an internal short circuit in the battery coupled with insulation failure. This led to higher voltages, causing a spark to jump and initiate an arc flash. Insulation failure might be a result of condensation caused by improper temperature and humidity control.
In summary, batteries should be managed and protected by designing a safety mechanism for early detection and monitoring of the internal and external conditions (voltage, current, temperature, and humidity) of a battery. Preventive measures should be adopted to address problems before they become unmanageable.
Delta’s solutions include (1) a battery cell voltage monitoring design that ensures that every battery cell is not used beyond its limit; (2) a system installation insulation detection system that detects the DC busbar insulation status in real time and cuts off the battery cabinet relay as soon as a leakage current or drop in insulation resistance is detected; and (3) a multi-point meter that measures the temperature and humidity inside and outside of the battery cabinet, and uses the battery system’s patented algorithm to regulate the environmental control and access control systems according to the status of the battery cabinet, thus preventing the risk of condensation inside the cabinet.
- Battery cabinet fire propagation prevention design: If an energy storage system is not compartmentalized, a thermal runaway event in a single battery is extremely likely to spread to neighboring cabinets, causing a massive fire in the entire container or even a sudden explosion. This makes rescue operations by firefighters more difficult and dangerous. Even if a fire does not spread to neighboring cabinets, the entire energy storage system would be rendered useless because of the toxic substance released after the thermal runaway in the Li-ion battery or the water used to extinguish the fire.
Standalone units and compartmentalization management are key safety design features in Delta’s energy storage systems, so that fire in a single battery module can be contained within that cabinet only. The interior of the cabinet is lined with heat-resistant ceramic material (temperature resistance: 1260 ºC), which can effectively prevent the fires from spreading and burning while also ensuring the safety of other cabinets and the normal operation of the entire energy storage system.
- Fire suppression design for energy storage systems: As mentioned earlier, clean-agent fire suppression systems for general fires cannot extinguish Li-ion battery fires effectively because a fire in an energy storage system has a special characteristic.
To address this problem, Delta adopts a dual-protection fire prevention strategy that provides protection both internally and externally. Internally, a gaseous clean agent is installed inside the cabinet to prevent electrical fires which can trigger thermal runaway in a battery. Externally, as the strengthening of the protection mechanism to cool the cabinet to avoid the expansion of the fire when an accident occurs, clients can consider to install a fire sprinkler system that discharges water to cool the cabinet in order to prevent fire propagation after a comprehensive assessment based on the site environment, the importance of surrounding buildings and equipment, and environmental safety regulations.
Generally speaking, if the site is unattended, located in a remote location, or has no existing fire fighting facilities, it is recommended to install automatic fire sprinkler system to initially control the fire before the firefighters arrive at the scene.
- Waterproof and dustproof design: According to China Electric Power Research Institute’s investigation report on the fire at the Dahongmen Power Station, when the firefighters were dealing with the fire at the southern section of the power station, water from the firefighting effort might have accidentally been sprayed to the northern area of the power section, causing a sudden explosion in that part of the station. Thus, determining how to use firefighting water more carefully to prevent high-voltage short circuits from causing an even more catastrophic fire is an integral part of damage control when an energy storage system catches fire.
Delta’s energy storage systems provide IP55 protection against dust and water so that if water from a fire sprinkler is sprayed outside of a cabinet, it won’t cause an electrical incident or high-voltage short circuit inside the cabinet, thus realizing damage control.
EPC designs and installation: Critical environmental measures
The roles and responsibilities of EPC companies are vital. Large renewable energy storage systems are frequently installed in mountains or coastal areas, including abandoned salt marshes and wetlands. Environmental and geological surveys of these locations must be performed thoroughly to establish relevant environmental measures (e.g., measures for preventing fire, wind erosion, corrosion, salt damage, water damage, and soil liquefaction). Attention must be paid to grounding systems and communication interference in order to prevent fires caused by system or equipment failure (e.g., cooling, warning, and control systems). During construction, insulation protection and engineering safety must be ensured, and any foreign objects must be covered properly to prevent accidents due to human or environmental factors during system testing.
Finally, when an energy storage system is installed and activated, subsequent maintenance and technical services are key to ensuring system safety. Apart from a good operations maintenance system and standardization of service operations, regular maintenance and monitoring mechanisms must be implemented to ensure system safety.
Conclusion
An energy system is effective only if considerable effort and resources are devoted to its development and use. Every detail and aspect is critical to the safety and operation of the system. Considering that a fire in an energy storage system burns very quickly, Delta has designed its energy storage systems with a multi-level safety mechanism as a thermal barrier. Future designs will require safety monitoring and management of battery cells and modules, protection and backup operation of cabinets and the entire system, and maintenance and technical support. As such, Delta has devised a comprehensive set of design and response strategies as a preventive measure, so that even if an incident occurs, any damage can be controlled and minimized, physical injuries can be avoided, and the road to energy transformation can be made smoother. This is the initial purpose and ultimate goal of Delta’s energy storage solutions.
More Information: Delta Energy Storage System: A Versatile Power Modulation Strategy
Delta Energy Storage Solution: https://www.deltaww.com/en-US/Solutions/Energy-Storage-Solutions/ALL/
