Planning board hears detailed update on Flatiron Energy battery storage project at 284 Eastern Ave

Chelsea City Planning Board members on Jan. 27 received an informational briefing on Flatiron Energy’s battery energy storage project at 284 Eastern Avenue and spent more than an hour questioning project staff about safety, security and visual screening.

Hunter Prangi, project manager at Flatiron Energy, said the company moved from a two‑story, building‑based design to a modular, containerized approach “to complete the project faster” and to meet floodplain and setback requirements. He added that the team selected off‑the‑shelf containerized battery modules and had contracted Consigli Construction to build the site. The project has been awarded a contract through the Massachusetts Department of Energy Resources procurement, Prangi said.

The redesign reduces zoning variances, the applicants said: mounting containers on elevated platforms lets the project meet a 15‑foot front setback and stay under the municipality’s maximum height threshold. Prangi also said equipment will be raised to a 14‑foot base flood elevation and that the layout avoids an old Chelsea sewer that runs through the site. “This allows the project in terms of schedule to come online much earlier,” Prangi said.

Board members pressed the team on operational and safety details. The project manager said the system will use lithium iron phosphate (LFP) chemistry, which Flatiron described as having a lower fire risk than older chemistries, and that the product will undergo UL and large‑scale fire testing before any modules are installed. “The product will not be installed on‑site until we have all passing reports,” the team said.

When asked whether a fire‑suppression system would be installed, applicants said there is no external water‑based suppression system for the containers; in a major thermal event the response protocol is remote shutdown, compartmentalization and emergency response from the fire department. “There’s a battery management system and a central fire panel on‑site,” Prangi said. He added that the fire department will be trained annually and instructed about staging and perimeter response rather than direct entry into containers in a thermal event.

The team said the modular layout includes spacing and ventilation to limit thermal‑runaway propagation, off‑gassing panels on container roofs to relieve pressure and that the product is designed and tested to avoid cascade failure. They said the design includes 124 containers on elevated platforms, each bolted to foundations; the team estimated each unit weighs roughly 80,000 pounds.

Security and vandalism were recurring concerns. Board members asked how the site would be protected from scaling, tagging, theft of service panels or tampering with controls. The applicant said the site will be fenced, monitored 24/7 with cameras and central station monitoring, include locked battery panels and remote shutdown capability; they called the security plan a layered approach that also relies on a 21‑foot screen wall proposal with landscaping and community art along Eastern Avenue.

On screening, the applicants proposed a tall (about 21‑foot) wall featuring a community mural on the Eastern Avenue face and trees that would grow to screen the wall over several years. Board members suggested exploring living walls or textured, paintable precast panels and urged more greenery to reduce tagging and visual bulk.

Flatiron representatives said they would return to the board in February for a public hearing on a modification and to provide additional technical documentation; staff also referenced ongoing coordination with Chelsea fire and that the project has been in monthly conversations with the fire chief. The board did not take a vote on Jan. 27 because the presentation was informational and the project will come back for formal review.

Next steps: Flatiron will supply additional materials and return to the planning board’s February meeting for major‑modification review and a public hearing.