SolaX Completes World’s First UL Conducted System-Level Deflagration Test on 5MWh BESS

SolaX has successfully completed a full-scale system-level deflagration test on its ORI 5MWh large-scale energy storage system under the proposed UL 9540A:2025 framework, with UL Solutions directly involved in the test design, execution and assessment.

As per firm's statement, the trial marks the first system-level deflagration test conducted globally by UL under the proposed standard.

The test was carried out on a fully integrated ORI 5MWh energy storage system using real lithium-ion battery cells. Under controlled conditions, selected cells were intentionally driven into thermal runaway while the emergency ventilation system was kept closed. This allowed the system to pass through the full sequence of flammable gas release, accumulation and deflagration, replicating a worst-case system-level risk scenario.

UL Solutions designed the test site, system configuration and operating conditions based on simulation studies to create a highly demanding environment. The trigger point was positioned in an area prone to stronger pressure waves and flame turbulence, increasing stress on the container’s structural integrity and pressure-relief mechanisms.

According to test observations, the pressure-relief structure activated as designed, container doors remained closed with no significant deformation, and the container structure remained intact without rupture. No components or structural fragments were ejected, and no additional risks to personnel or the surrounding environment were identified.

A UL Solutions engineer involved in the test said that the scenario was designed to maximise both severity and realism, while accounting for uncertainties associated with real battery thermal runaway and gas dispersion. The layout incorporated redundant ignition sources and a carefully defined trigger-cell initiation mode, with the trigger cell positioned to maximise deflagration potential. The engineer added that the test presented a high level of challenge to the system’s structural integrity and safety functions, and the results provide valuable reference for understanding system-level safety boundaries.

SolaX said that the test reinforces its approach of treating safety as a development baseline rather than a compliance milestone. Company representatives stated that risks associated with deployed systems are ultimately borne by customers, making early identification of safety boundaries through rigorous testing a core responsibility.

SolaX further said that it will continue working with UL Solutions and other international organisations to advance system-level energy storage safety and support the long-term integration of large-scale storage into global power systems.