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December 20, 2021

Constructing Energy Storage Systems with Safety as a Priority

Dhruv Patel, Senior Vice President of EPC Renewable Energy & Storage, McCarthy Building Companies

This is a guest blog post from #ESACon21 sponsor McCarthy Building Companies.

When building storage facilities, the safety of an energy storage system (ESS) needs to be top priority and planning for a potential thermal event is key. Owners should begin by choosing UL-rated systems and installing to National Fire Protection Association (NFPA) standards. Energy storage standards from UL 9540 began in 2016 and NFPA 855 in 2020, and were based on input from hundreds of stakeholders, including engineers, installers, manufacturers, first-responders and safety policymakers with the goal of preventing loss of life and property.

Many safety concerns, especially with lithium-based batteries, relate to thermal incidents; for example, when a battery experiences an increase in temperature that eventually leads to cell short-circuiting or disintegration that can spark a fire. Batteries can malfunction through physical damage, neglect or electrical issues, but owners can significantly reduce the odds of this happening by routinely testing energy storage systems and ensuring they are installed to industry standards.

What is NFPA 855 and why is it important?

This standard from the NFPA focuses on how to prevent and extinguish ESS fires by installing systems correctly and providing accurate safety labeling for worst-case scenarios. NFPA’s installation standards aren’t enforceable unless adopted by the local jurisdiction, but any reputable installer should follow NFPA standards.

NFPA 855 requires 3 feet of space between every 50 kWh of energy storage, however, there are some exceptions. The NFPA installation standard also uses results of UL 9540A testing methods to determine what safety labels and fire suppression systems are necessary. Labels will explain what type of battery is installed and what safety measures are already in place, so first responders aren’t surprised when they arrive at an emergency.

Utilizing the UL 9540A test method

The UL 9540A test method sheds light on how batteries perform in fire conditions. If a thermal event should occur, this test shows how the ESS would react. A battery can’t pass or fail these tests, but the results help installers design systems for the most successful performance. It essentially simulates a thermal event in a single cell to understand if it will spread.

UL 9540A tests look at the battery cell, battery module and the battery unit. The test tries to initiate a thermal event at the cell level, then notes how it happened and how the module reacted. Then it considers how fire spreads from unit to unit to determine the potential for an explosion. Finally, a closed room test is performed to show how a unit-to-unit fire spreads and reacts to fire mitigation equipment.

The results of these extreme tests aid fire departments and other safety organizations in both installing energy storage systems and successfully suppressing any fires or other negative outcomes that may occur during their use.

Importance of early communication, routine preventative maintenance

When first developing plans for an ESS, upfront communication with the local Authority Having Jurisdiction (AHJ) should take place prior to completing design. Gaining input and understanding local requirements will ultimately produce a safer facility. Formal reviews should be conducted with authorities throughout the construction process. By including the AHJ early on in planning, the reviews tend to go more smoothly because they already understand the design and concept.

Energy storage systems are relatively new to most municipalities, however, others will have experience and will be able to share lessons learned from other projects in their jurisdiction. It’s important to have fully developed emergency response plans with clear site access, and navigate those plans on site to ensure feasibility.

Additionally, a clear preventative maintenance program should be established early on in order to ensure the system’s performance, functionality and safety. The plan should include thermal AR scans, regularly scheduled outages (to perform visual inspections of the system and verify torque of connections are within proper tolerances), and a system for keeping records and logs.

Although ESS fires and explosions are rare, it’s important to prepare for a worst-case scenario. Installing UL-certified systems to NFPA standards, utilizing the UL 9540A test method and communicating early on in the planning process ensure that energy storage adoption is a safe option for everyday power needs.

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