Lithium-ion energy storage battery explosion incidents

https://doi.org/10.1016/j.jlp.2021.104560Get rights and content

Highlights

  • Accounts of energy storage battery fires and explosions.

  • Lithium-ion battery thermal runaway gas explosion scenarios.

  • Deflagration pressure and gas burning velocity in one important incident.

  • High-voltage arc induced explosion pressures.

Abstract

Utility-scale lithium-ion energy storage batteries are being installed at an accelerating rate in many parts of the world. Some of these batteries have experienced troubling fires and explosions. There have been two types of explosions; flammable gas explosions due to gases generated in battery thermal runaways, and electrical arc explosions leading to structural failure of battery electrical enclosures. The thermal runaway gas explosion scenarios, which can be initiated by various electrical faults, can be either prompt ignitions soon after a large flammable gas mixture is formed, or delayed ignitions associated with late entry of air and/or loss of gaseous fire suppression agent. The electrical explosions have entailed inadequate electrical protection to prevent high energy arcs within electrical boxes vulnerable to arc induced high pressures and thermal loads. Estimates of both deflagration pressures and arc explosion pressures are described along with their incident implications.

Introduction

According to the International Energy Agency (2020), worldwide energy storage system capacity nearly doubled from 2017 to 2018, to reach over 8 GWh. The total installed storage power in 2018 was about 1.7 GW. About 85% of the storage capacity is from lithium-ion batteries.

U.S. Energy Information Administration (2019) projections are that megawatt-scale battery capacity will approximately triple from 2018 to 2021. Based on current utility plans, EIA projects most of the additional capacity to come from increasingly large lithium-ion energy batteries. Many such installations are now in the range 2 MW–20 MW, but several planned installations have capacities greater than 100 MW. A major reason for these expansions is that the cost for lithium-ion batteries lowered from approximately $1200 per kWh in 2010 to less than $200 per kWh in 2018 (Bloomberg, 2019).

Fig. 1 shows a simplified layout of a utility-scale lithium-ion Energy Storage Battery (ESB) installation unit. Lithium-ion cells, the basic building blocks of the system, are installed in a module. These cells usually have vents to prevent internal over-pressurization. Modules are equipped with electrical protection (fuses) and sensors for monitoring of voltages and (sometimes) temperatures, and either passive or active ventilation provisions.

Modules are placed and electrically interconnected with a Battery Management System (BMS) and Junction Box (JB) in vertical racks as indicated in Fig. 1. Each rack has a rack-level battery management system that communicates with the module sensors, and also has one or more DC connectors and fuses. A typical rack has a voltage of about 1000 VDC. The racks are installed in an enclosure, sometimes called a Battery Energy Storage Unit, equipped with system level Battery Management System (BMS) for electrical control, a Heating Ventilation Air Conditioning (HVAC) system, and a fire detection and suppression system. Interactions with power supply and discharge systems occur via an external Power Conversion System and Energy Management System as shown in Fig. 1.

Battery Energy Storage Units have doors for operating and maintenance personnel and for installation and replacement of equipment. A variety of Energy Storage Unit (ESU) sizes have been used to accommodate the varying electrical energy and power capacities required for different applications. Several designs are variations or modifications of standard ISO freight containers, with nominal dimensions of 2.4 m × 2.4 m x 6 m, and 2.4 m × 2.4 m x 12 m. Other designs are up to 16 m in length.

Installations are being located in rural, urban, and suburban areas, often adjacent to a solar power or wind turbine generator for charging the battery. There are also many behind-the-meter installations in which the energy storage battery can be charged by the utility electricity grid and often has electrical controls to allow discharging through an inverter and utility interface back into the grid.

Unfortunately, there have been a large number of energy storage battery fires in the past few years. For example, in South Korea, which has by far the largest number of energy storage battery installations, there were 23 reported fires between August 2017 and December 2018 according to the Korea Joongang Daily (2019). A Korean government led investigation of these incidents found that one important cause of the fires was defective battery protection systems. The failure of these protection systems in some incidents caused components to explode. Other fires in South Korea and elsewhere have involved explosions from other causes, including a vulnerability of some batteries to operate at abnormally high temperatures under certain fault conditions (Yonhap News Agency, 2020).

The objectives of this paper are 1) to describe some generic scenarios of energy storage battery fire incidents involving explosions, 2) discuss explosion pressure calculations for one vented deflagration incident and some hypothesized electrical arc explosions, and 3) to describe some important new equipment and installation standards and regulations intended to prevent energy storage battery explosions.

Section snippets

Thermal runaway gas explosion incidents

Various recent papers, for example Guo et al. (2018) and Li et al. (2019), describe how any one of several fault conditions, including electrical faults, overcharging, and particulate/moisture contamination, can lead to an escalated temperature in one lithium-ion cell, causing deterioration and eventual failure of the cell separator, with subsequent electrolyte decomposition and elevated vapor pressure. This leads to a thermochemical runaway venting in the cell that can then propagate to many

Thermal runaway explosion prevention measures

The lithium-ion energy storage battery thermal runaway issue has now been addressed in several recent standards and regulations. New Korean regulations are focusing on limiting charging to less than 90% SOC to prevent the type of thermal runaway conditions shown in Fig. 2 and in more recent Korean battery fires (Yonhap News Agency, 2020). The new NFPA 855 standard for energy storage systems requires that “a listed device or other approved method shall be provided to preclude, detect, and

Arc flash explosion incidents

Several lithium-ion battery energy storage system incidents involved electrical faults producing an arc flash explosion. The arc flash in these incidents occurred within some type of electrical enclosure that could not withstand the thermal and pressure loads generated by the arc flash. One example of an electrical enclosure that is designed to withstand a limited/controlled arc flash is a DC contactor. Each rack in the ESS enclosure is usually equipped with at least one high-voltage DC

Conclusions

Several large-scale lithium-ion energy storage battery fire incidents have involved explosions. The large explosion incidents, in which battery system enclosures are damaged, are due to the deflagration of accumulated flammable gases generated during cell thermal runaways within one or more modules. Smaller explosions are often due to energetic arc flashes within modules or rack electrical protection enclosures. These smaller explosions can either initiate or exacerbate energy storage system

Authors credit statement

Robert Zalosh: Conceptualization, Formal Analysis, Writing – Original & Review.Prainray Gandhi: Validation, Writing – Reviewing and Editing. Adam Barowy: Visualization, Writing – Reviewing and Editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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