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UL Responds to Battery Energy Storage System Incidents and Safety

Gain clarity on the scope of energy storage product and system testing and UL Solutions’ maintenance of standards and certifications, in addition to post-market surveillance operations.

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On July 18, 2020, DNV GL  published a report, titled “McMicken Battery Energy Storage System Event – Technical Analysis and Recommendations”. The report presented an analysis conducted by DNV GL on behalf of Arizona Public Service (APS) regarding the investigation into a thermal event and subsequent explosion that occurred at the APS McMicken Battery Energy Storage facility.

Addressing Inaccuracies in the McMicken energy storage event report

The DNV GL Report contains some inaccuracies with respect to the Underwriters Laboratories Standards development process as well as the scopes and test methodologies of the referenced UL Standards. The response presented by Underwriters Laboratories provides clarifications to the DNV GL report along with an overview of the Standards development process. The response presented by UL Solutions provides an overview of energy storage safety regarding the scope of the testing of energy storage products and systems.  

The links below provide the detailed responses from Underwriters Laboratories, the nonprofit organization responsible for the development and maintenance of UL Standards, and UL Solutions, the testing, inspection, and certification entity responsible for the certification of products to UL Solutions and other standards:


UL Response to DNVGL APS Report

230.14 KB

Executive Summary for UL Response to DNVGL APS report

182.47 KB

Cover Letter to McMicken Report Response

99.39 KB

Underwriters Laboratories Response to DNVGL APS Report

255.02 KB

The battery and energy storage system industry is dynamic with many new developments underway and there have been, and continue to be, multiple revisions of the UL Standards affecting this industry. UL Standards will continue to evolve as technology advances, safety concerns are identified, and additional research, testing and data become available.

Empowering our energy storage customers with safety standards and certifications

Our stewardship of the public’s trust in Underwriters Laboratories and UL Solutions is of the utmost importance. We expect that these responses will not only clarify information in the DNV GL report, but will also provide future opportunities for collaboration with all of our partners — not only in the development and maintenance of UL standards, but also in UL Solutions’ certification of energy storage products and their post-market surveillance.


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