Battery energy storage systems are becoming a core part of the electric grid, storing power and releasing it when it is needed. As these installations grow, so does the importance of understanding how they behave when something goes wrong.
Standards bodies have been moving to address that question. The sixth edition of UL 9540A, published March 13, 2026, adds large-scale fire and deflagration testing aligned with NFPA 855-2026, according to UL’s published guidance on installation codes and requirements for energy storage systems. These changes reflect a growing recognition that cell-level failures can escalate to installation-level events, and that test methods need to capture that escalation.
Recent events underline the point. In mid-September 2026, a fire broke out again at the Moss Landing battery energy storage facility operated by Vistra in California. According to the U.S. Environmental Protection Agency, it involved about 1,300 battery modules damaged in the January 2025 fire and still held in a building that has not operated since. As reported by KSBW, the U.S. Environmental Protection Agency warned that unstable battery modules could reignite, a reminder that the hazard from a battery fire may persist well after visible flames are out.
Stronger standards and rigorous large-scale testing are essential, and they should be supported. But the physics of these events also argues for attention at the smallest scale. A grid-scale fire typically begins with a single cell entering thermal runaway. If that process can be anticipated, detected early and contained within the module or pack, the chance of escalation may be reduced. Prediction, detection and suppression at the cell and pack level are therefore not alternatives to system-level safety; they are part of it.
DELTTA SUNMASS INNOVATIONS LLC, based in Great Neck, New York, is developing DELTTA NEX GEN, a patent-pending architecture intended to address thermal runaway prediction, detection and suppression. The company emphasizes that the technology is at the development stage. It has not been tested or certified under UL 9540A or any other standard, it is not endorsed by UL, NFPA or any other organization, and its proposed performance targets remain subject to independent evaluation and certification.
Consistent with that status, DELTTA SUNMASS is publicly inviting scientists, engineers, accredited testing laboratories, energy storage operators and fire services to evaluate the architecture independently. The company welcomes rigorous scrutiny, including findings that identify limitations.
“The new edition of UL 9540A and NFPA 855-2026 show how seriously the industry is taking propagation risk. Any new safety technology, including ours, should be measured against that same rigor, and we are inviting qualified experts to do exactly that.” — Dr. Philip H. M. Thomas, Founder, Group Chairman & Global CEO, DELTTA SUNMASS INNOVATIONS LLC
The direction of the standards is clear: more realistic testing, at larger scale, with greater attention to how failures spread. Innovation at the cell and pack level should be held to the same expectation, and earn its place through independent evidence.
Contact for evaluation inquiries and responses: contactdeltta@delttagroup.com | greentechlabs@delttagroup.com
Sources
- UL Solutions, “Installation codes and requirements for energy storage systems (ESS) FAQs”: https://www.ul.com/resources/installation-codes-and-requirements-energy-storage-systems-ess-faqs
- KSBW, Moss Landing battery fire and unstable batteries: https://www.ksbw.com/article/moss-landing-battery-fire-unstable-batteries/73828347
- U.S. EPA, “September 2026 Fire” (Moss Landing): https://www.epa.gov/ca/september-2026-fire
- DELTTA NEX GEN video presentation: https://sunmass.delttagreentech.com/watch/