A fire safety engineering firm hired by the Town of Norfolk has found that NextGrid’s permit application for a battery storage system (BSS) at the Pond Street solar farm is incomplete and that key documents still need to be filed before the project can move forward.  The same firm was hired by NextGrid to perform a plume study.  

The firm, Jensen Hughes of Westborough, delivered its findings to the town on May 6. The review was commissioned by Norfolk as part of the permitting process for the battery energy storage system, known as a BESS, that is part of the Pond Street solar project.

Fire code review 

Jensen Hughes examined four categories of documents that fire code requires before a large battery installation can be permitted: site and layout plans, two hazard analysis reports, and an emergency response plan.

The emergency response plan, which covers how personnel and responders would handle fires, equipment failures, and other emergencies, passed review. The plan meets the requirements of NFPA 855, the national fire safety standard for battery storage systems.

The other submissions fell short.

The site plans were found to be incomplete as they do not identify how many battery containers will be installed, how far apart they will be placed, or how they relate to electrical equipment, exit pathways, and roadways. Jensen Hughes stated that this information is needed to assess whether fire could spread from one battery unit to another.

In addition, NextGrid was required to submit two hazard mitigation analyses: one covering the battery itself and one covering the specific site. Jensen Hughes noted that NextGrid provided some documents, but that they were incomplete.

The report concluded that all missing items must be submitted and approved before the project can proceed.

The plume study

Separately, NextGrid commissioned Jensen Hughes to analyze what would happen if a battery malfunctioned and released toxic gases. That report examined a scenario in which one battery module fails - a so-called thermal runaway- and gases are vented through the top of the container.

The study found that the most hazardous gas released in such an event is carbon monoxide which rises quickly after it exits the container because it is released upward at high temperature. Modeling showed that concentrations dangerous to human health would remain within about 25 feet of the exhaust point but would not reach ground-level breathing height at that distance.

The report used conservative assumptions, including the worst 5 percent of wind conditions recorded at Norwood Memorial Airport over 20 years. 

Background

The Pond Street site has been under construction since the project received town approvals in 2022. Panels and battery containers have not yet been installed. The site involves approximately 25 acres and is designed to generate about 6 megawatts of electricity for the grid.

As we reported in February, a resident group called the Norfolk Commonsense Coalition raised concerns about battery safety, transparency in the approval process, and the cancellation of a planned access road from the Police Department on Sharon Avenue. That road was removed from the plan in 2024.

The batteries planned for the site use lithium iron phosphate chemistry. NextGrid has described this as a safer battery type than other lithium-ion formulations because it requires higher temperatures to reach thermal runaway. The system has received a UL 9540 listing, a certification for energy storage systems.

What Comes Next

Based on the Jensen Hughes review, NextGrid must revise its site plans and submit complete hazard analyses before the fire code permitting process can be completed.