FAT for Fitness

By Jeff Zwijack

This article was originally published in pv magazine – March 2024 Edition.

Large-scale, stationary battery energy storage systems (BESS) have rapidly become crucial components of modern power grids. With the increasing adoption of BESS, however, the risk of battery fires has increased, as Jeff Zwijack of Clean Energy Associates reports.

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Lithium batteries are powerful but fragile and they contain a potent, flammable electrolyte. When a lithium battery enters a state of “thermal runaway,” it suffers an irreversible chemical reaction that cannot be stopped. Once initiated, a battery in thermal runaway releases a substantial amount of heat and energy – a problem that is becoming more challenging to manage as the industry moves toward ever larger battery cells.

A recent Clean Energy Associates (CEA) audit of BESS factory acceptance testing (FAT) has revealed some alarming results. Of the systems inspected, 18% exhibited problems with their thermal management system and 26% had defects in their fire-suppression systems. While not all of the problems identified were critical, any deviations from the quality requirements for the key protections to prevent a fire from starting and spreading are cause for concern.  

Even on a small scale, lithium batteries such as those found in phones and laptop computers can cause significant damage. The risk compounds even further with large-scale BESS projects.

It is crucial to minimize the risk of major issues and that starts with the battery cell itself. Selecting the right supplier and ensuring a high-quality manufacturing process for the cell, module, and rack is critical.

The Past Several Years Have Shown That Thermal Runaway Poses a Significant Risk to the Energy Storage Industry

Battery management

The battery management system (BMS) is the next layer of defense. It defines safe operating parameters for voltage, current, and temperature, and can intervene autonomously to prevent critical failures. It is crucial to ensure that the BMS is designed to meet the specific needs of the BESS. Integrators and developers must carefully evaluate BMS options to ensure safety and reliability.  

The thermal management system works hand-in-hand with the BMS to control a battery’s temperature during operation. It detects when the battery system gets too hot and uses cooling mechanisms, such as air or liquid, to dissipate excess heat.

In the event of a fire or a detected fire hazard, the fire suppression system kicks in to swiftly mitigate the threat. These systems incorporate various early detection mechanisms such as smoke detectors, heat sensors, and gas analyzers. In extreme cases where fire risk is imminent, the BESS may have an emergency shutdown procedure to de-energize the system, disconnect the batteries, and isolate any potential sources of fire.

Developers also need to think about energy storage integration inherently differently from the way the industry thinks about solar project integration. In solar, with a high-quality PV module, racking system, and inverter, any competent engineering firm can put all of that together and design a safe and effective project. It is not always necessary for the engineering firm to have experience implementing the specific panel model or racking system.

26% of batteries inspected by CEA had fire-suppression system defects

Quality assurance

Energy storage adds an additional layer of complexity, so it is essential to fully assess an integrator’s capabilities. Integrators should offer experience with the specific battery cells, inverters, and control systems chosen for a project, ensuring they can handle any challenges that may arise as those components are assembled. Factors such as financial stability, the number of years in business, project execution history, and compliance with safety standards should also be considered.

Even when the right battery cells, inverters, and control systems are selected, rigorous factory acceptance testing (FAT) is necessary to ensure that an integrator fulfills its obligations. One key aspect of FAT is to include all of the specifics in the supply agreement. If a purchaser is arguing about FAT protocols after a deal has been signed, their leverage is very limited.

The second key aspect of FAT is to have an expert representative on site witnessing the entire process. Testing involves comprehensive assessments of thermal management systems, fire suppression systems, and overall system functionality. Test results provide insights into a system’s readiness for deployment, and enable developers to identify and address defects or weaknesses before they can become operational hazards.

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Jeff Zwijack is CEA’s Associate Director for energy storage, helping buyers to choose the right suppliers and ensure product quality and safety. Zwijack previously started the application engineering and sales team at IHI Terrasun Solutions, where he helped to propose and design more than 11 GWh of energy storage system opportunities. He has helped to close more than 1 GWh of projects.

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