Battery energy storage systems (BESS) use an arrangement of batteries and other electrical equipment to store electrical energy. 越来越多地用于住宅, 商业, 工业, and utility applications for peak shaving or grid support these installations vary from large-scale outdoor and indoor sites (e.g., warehouse-type buildings) to modular systems. 集装箱系统, 模块化设计的一种形式, have become a popular means of efficiently integrating BESS projects.
由于快速的响应时间, lithium-ion BESS can be used to stabilize the power grid, 调制栅极频率, and provide emergency power or 工业-scale peak shaving services, reducing the cost of electricity for the end user. 然而, high-powered and rapid charge cycles can put stress on the batteries resulting in degradation over time, 哪些不利于安全.
在过去的四年里, more than thirty large-scale BESS around the world experienced failures that resulted in fires and, 在某些情况下, 爆炸. 考虑到皇家88账户注册些问题, professionals and authorities need to develop and implement strategies to prevent and mitigate BESS fire and explosion hazards. The guidelines provided in NFPA 855 (Standard for the Installation of Energy Storage Systems) and Chapter 1207 (Electrical Energy Storage Systems) of the International Fire Code are the first steps.
热失控
Prevention and mitigation measures should be directed at thermal runaway, which is by far the most severe BESS failure mode. If thermal runaway cannot be stopped, fire and explosion are the most severe consequences.
Thermal runaway of lithium-ion battery cells is essentially the primary cause of lithium-ion BESS fires or 爆炸. Under a variety of scenarios that cause a short circuit, batteries can undergo thermal runaway where the stored chemical energy is converted to thermal energy. If the process cannot be adequately cooled, an escalation in temperature will occur fueling the reaction, which can result in cell rupture and release of flammable and toxic gases. The most common initiating events for thermal runaway include:
- 电池制造缺陷
- 收费过高(e.g.，逆变器故障)
- 过热(e.g., poor cooling capacity or cooling system failure)
- 机械虐待(e).g.(地震事件或撞击)
Battery Management System as a Barrier to 热失控
在电池储能系统中, one of the most important barriers is the battery management system (BMS), which provides primary thermal runaway protection by assuring that the battery system operates within a safe range of parameters (e.g.，电荷状态，温度). 在UL 9540中列出了BESS, BMS监视器, controls and optimizes the performance of battery modules and disconnects them from the system in the event of abnormal conditions. The BMS also provides charge and discharge management of the batteries.
In case of undervoltage or overvoltage, 过热现象, 或者过流状态, the BMS will alarm and then limit the charge and discharge current or power. 在紧急情况下, the BMS will cease operations and electrically disconnect each battery enclosure. This is assuming that the BMS is not damaged and operational. 然而, if an internal cell breakdown has occurred, the BMS will not stop the thermal runaway.
爆炸控制
A thermal runaway with fire or explosion as the consequence is the most severe hazard to prevent or mitigate. While there has been some guidance on fire control and suppression, 许多BESS制造商, integrators and end-users struggle with the explosion control requirement. 爆炸控制 can be achieved by providing one of the following:
- Explosion prevention systems are designed, 安装, 操作, maintained and tested by NFPA 69 (Standard on Explosion Prevention Systems)
- Deflagration venting 安装 and maintained following NFPA 68 (Standard on Explosion Protection by Deflagration Venting)
If implementing an explosion prevention system according to NFPA 69, the combustible concentration shall be maintained at or below 25 percent of LFL for all foreseeable variations in operating conditions and material loadings. One option for achieving these requirements is ventilation or air dilution. This can be accomplished by installing a forced ventilation system, which can be automatically actuated by a gas-detection system when gas concentration levels exceed a pre-determined set point.
此外, deflagration venting creates a pathway for rapidly expanding gases to exit the enclosure in the event of a deflagration. It can be challenging to protect BESS enclosures with little free air volume and a high degree of internal obstruction. Performance-based engineering methods, such as Computational Fluid Dynamics (CFD), 在皇家88账户注册种情况下可能需要.
Best Practices for Mitigating BESS Hazards
Compliance with NFPA 855 is increasingly required to permit a BESS, and the International Fire Code (IFC) has influenced local fire code requirements concerning these systems. Hence, NFPA 855 and the IFC are used to guide best practices along with industry experience (i.e., lessons learned from failure events).
The following are best practices for BESS with an energy capacity greater than 600 kWh. These are for the BESS product level and do not have general applicability to various installation sites. Depending on the installation location of the BESS, additional local requirements and preferences may need to be considered. 此外, all features shall meet applicable local codes and standards, including the use of listed equipment.
- 减灾分析(HMA). HMA aids in identifying and mitigating hazards created with the BESS technology. At a minimum, the HMA should address the failure modes identified in NFPA 855 and the IFC. The HMA can be used to analyze the effectiveness of 安装 safety measures.
- 烟雾和火灾探测. 烟雾和火灾探测 equipment is required to be 安装 in large BESS enclosures that are not remote or indoor applications. The IFC requires smoke detection and automatic sprinkler systems for “rooms” containing stationary battery energy storage systems.
- 火控与灭火. 火控与灭火 is prescriptively required by NFPA 855 but may be omitted if approved by both the authority and the owner if the project site is remote and outdoors. The IFC requires automatic sprinkler systems for “rooms” containing stationary battery energy storage systems. In case of thermal runaway with the resulting fire, water is the preferred agent for suppression. While incapable of stopping thermal runaway in the cells where that process has already started, fire sprinklers are capable of controlling fire spread and reducing the hazard of a lithium-ion battery fire.
- 爆炸控制. NFPA 855 requires explosion control measures in the form of deflagration venting (NFPA 68) or explosion prevention (NFPA 69), including cabinet-style BESS enclosures.
- 气体探测. 气体探测 may be used as part of an NFPA 69 explosion control solution.
- 热失控保护. 热失控保护 is required and can generally be achieved by using a battery management system that is UL 1973 certified.
- 尺寸和分离要求. Separation distances between each BESS container and adjacent structures should be maintained to reduce fire spread. There are prescriptive distances that can be shortened under the consideration of full-scale fire test data, performance-based methods or by using engineered fire barriers.
- 水的供应. Since water is the preferred agent for suppressing lithium-ion battery fires, a permanent source of water is recommended.
Address the Fire Safety Challenges of Lithium-Ion Battery Storage
BESS is an important element in reducing carbon emissions and enabling renewable power generation technologies. In a time of increased development and deployment of BESS installations, it is important to make sure that it is done safely. Jensen Hughes can help you address the unique fire safety challenges associated with lithium-ion battery storage and handling and ensure that building and fire code requirements are met.
