Designing, Installing, and Maintaining Safer Battery Energy Storage Systems

By Judy Jeevarajan, vice president and executive director, ULRI’s Electrochemical Safety Research Institute

Battery energy storage systems (BESS) are being installed at a slower pace on a global level than in the late 2010s. This is a result of the fires observed with these significantly large BESS, which range in energy from megawatt hours to gigawatt hours. A majority of the BESS installed globally are based on lithium-ion battery chemistry, with only a handful of them using flow battery chemistries. In 2019, reports from South Korea confirmed the occurrence of about 23 fires with lithium-ion battery BESS installations.¹

Lithium-ion batteries were used to power portable electronic devices such as cameras, camcorders, and laptops in the late 1990s, and their use has increased exponentially in the past three decades due to the many advantages they offer, which includes lighter weight, smaller volume, high rate capability, long cycle life, and no memory effect. However, associated with these advantages also comes the very high propensity for lithium-ion batteries to undergo thermal runaway accompanied by venting, smoke and/or fire. This is observed when the cells and batteries are not manufactured at a high quality², not designed appropriately, used or charged incorrectly, not tested adequately to characterize operational and safety limits, and not certified in the required relevant manner at the various levels from cell to system level.³

At ESRI, the battery experts have worked on characterizing the safety of lithium-ion cells and batteries under various nominal and off-nominal conditions. ESRI research has included characterizing thermal runaway and its gaseous⁴ and particulate emissions⁵, mitigation of thermal runaway propagation and efficacy of fire suppressants for lithium-ion fires. Manufacturers, installers, and operators should create a detailed failure modes and effects analysis (FMEA) that considers all possible failure scenarios and then pare it down to determine the credible failures. The next step should include tests, analyses and verifications to confirm that the risks posed by these failures are minimized or eliminated. Large-scale grid energy storage should be designed to prevent the occurrence of thermal runaway, have early detection and mitigation of venting and fire, mitigate the propagation of thermal runaway if it were to occur, provide for a safe venting of gases and smoke to prevent combustion or explosions due to combustible gas accumulation in confined spaces, and finally have a very effective fire suppression system. High-fidelity models will provide adequate data for safe design and installation of the high-voltage, high-capacity stationary grid storage systems.

In addition to the characterization of the batteries manufactured with fresh or reused cells, the energy storage systems require periodic inspection and maintenance. Real-time data should be tracked closely, and personnel should be trained to review and comprehend any excursions beyond the manufacturer’s specification for the system that may lead to a hazardous event if left unchecked. Periodic maintenance should include visual inspections of the battery modules to look for loss of integrity such as loose interconnects and tabs, loose thermocouples and sense lines, swelling or shape changes of cells, modules and battery packs, or leakage of cooling fluids. Changes in battery and energy system behavior due to age and environment of usage should be well understood by the manufacturer, and changes that need to be incorporated to continue to monitor the health of the battery should be integrated without interruptions.

A review and confirmation of the data associated with the verifications should be completed by the authorities having jurisdiction (AHJ) before the BESS is commissioned and operational. In the past decade, cells, modules or batteries used in electric vehicles have been reconfigured into batteries used in stationary grid energy storage applications. The relevant tests need to be conducted on the used cells, modules or batteries to confirm state of health, and once configured into batteries, should undergo the relevant certification tests for grid energy storage installations. Certifications to well-established standards (such as UL1973, UL1974, UL9540, UL9540A, IEC62619, and IEC63056) should be conducted and the data and results reviewed by AHJs for conformance. Periodic inspections and audits are required to be performed to confirm safe working of the BESS installations.

BESS designers, installers, and maintenance operators can review the information listed in the reference section below to design safer systems and reduce the risk posed by these systems.

References:

1. “ESS units caught on fire due to bad management”, 2019 [https://koreajoongangdaily.joins.com/2019/06/11/economy/ESS-units-caught-on-fire-due-to-bad-management/3064174.html].
2. T. Joshi, S. Azam, D. Juarez-Robles, J. Jeevarajan, “Safety and Quality Issues of Counterfeit Lithium-Ion Cells”. ACS Energy Lett., 8, 2831, 2023 [https://doi.org/10.1021/acsenergylett.3c00724].
3. J. Jeevarajan, T. Joshi, M. Parhizi, T. Rauhala and D. Juarez-Robles, “Battery Hazards for Large Energy Storage Systems”, ACS Energy Letters, 7, 2725-2733, 2022 [https://doi.org/10.1021/acsenergylett.2c01400].
4. Kwon, B., Schraiber, A., Jeevarajan, J. A., “Evaluating fire and smoke risks with lithium-ion cells, modules and batteries”, ACS Energy Letters, 9, 5319-5328, 2024 [https://doi.org/10.1021/acsenergylett.4c02480].
5. Premnath, V., Parhizi, M., Niemiec, N., Smith, I., Jeevarajan, J., “Characterization of Particulate Emissions from Thermal Runaway of Lithium-ion Cells”, Journal of Electrochemical Energy Conversion and Storage, 2024 [https://doi.org/10.1115/1.4065938].

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