Eversource’s Putnam Avenue substation in Cambridgeport was expanded in 2020. (Photo: Marc Levy)

As Eversource seeks approval to build a substation in Kendall Square and expand its electric distribution and transmission system in Cambridge, Somerville and Brighton, the company is already coping with increased demand for power that has brought parts of the existing system close to its operational limits, company experts testified last week. Eversource has started installing “long feeders” to connect some East Cambridge customers individually to its substation on Putnam Avenue in Cambridgeport because the existing East Cambridge substation is already over capacity, according to company witnesses.

Eversource wants to build an 11-story underground substation and connect it with existing facilities in Somerville, East Cambridge, Putnam Avenue and Brighton. The company says it needs the project to reliably serve customers amid rapidly rising demand in the Cambridge area – not because there isn’t enough power but because the cables, transformers and other equipment needed to bring electricity to customers won’t be sufficient to carry the increasing power load.

The company wants to bring the system online by 2030, but testimony at a hearing of the Energy Facilities Siting Board on Oct. 16 indicated it could be needed more urgently. Growth not only in Cambridge but also in Somerville, and limited excess capacity at all three substations serving Cambridge and Somerville, means Eversource has little cushion in the distribution system, company witnesses said.

“The project would be needed earlier because the transmission overloads and the ensuing risk of load shed is further heightened” if one piece of equipment should fail – the contingency that Eversource plans for, said Eversource vice president of system planning Digaunto Chatterjee. Load shed refers to cutting off power to customers.

The siting board and the Department of Public Utilities must approve the project; a decision could be delayed, Eversource says, because the Massachusetts Institute of Technology filed a last-minute opposition to the utility’s preferred route through the MIT campus and wants the board to give full consideration to MIT’s proposed alternate routes.

The City of Cambridge is also concerned about a delay and was trying last week to meet with MIT and Eversource to stave it off, public works commissioner Kathy Watkins said. On Wednesday, the city asked the siting board for permission to file “brief testimony” that would “formally state its position” on the dueling routes.  The city’s motion for a late filing, which was granted, said it was acting because of “very recent developments” in its discussions with Eversource and MIT.

Somerville’s needs grow

Eversource witnesses described shrinking opportunities to transfer electricity loads among the existing substations: Somerville, East Cambridge and Putnam Avenue Until recently the Somerville facility served mostly the Prospect Street area of Cambridge because there was little growth in demand in Somerville, they said. Now, with extensive development in Boynton Yards and the Union Square area, Eversource expects that demand in Somerville will be 24 megawatts higher than when it filed the application to build the new system in March 2022 – an unusually big jump, Chatterjee said.

Eversource had planned to add a third transformer to the Somerville substation this year, but it has been delayed until the end of next year because of “permit issues” involving the City of Somerville. The additional transformer wouldn’t be enough anyway, he said.

When the company filed its application, “we had assumed 44 megawatts of load will be transferred out of East Cambridge, onto Somerville; and as Somerville load increases, the ability to have transfers from East Cambridge to Somerville gets more and more limiting, even after the addition of the third transformer,” he said.

“If you’re sensing panic”

The Somerville substation will be needed to serve the increasing load in that city and won’t be available to help in Cambridge, he said. Meanwhile, there is no room in the other existing substations – Somerville and Putnam Avenue – to increase distribution capacity, he said.

The understanding is that “Somerville is maxed out. There is no feasible way to add a fourth transformer at Somerville,” Chatterjee said. The next closest distribution bulk station is some 5 miles away in North Cambridge, and that area is also growing, “so we will have to add a fourth transformer at North Cambridge to supply its own needs.”

“If you’re sensing panic, it’s that we’re kind of out of options on the distribution side. Regardless of how we move load around between Putnam and East Cambridge and Somerville from the transmission standpoint, that load pocket just keeps going up,” Chatterjee said.

To deal with the situation for now, “we’re physically now running feeders from Putnam into the streets of East Cambridge to pick up that load,” he said.

Vicinity plant adds to burden

One potential new customer – not included in the company’s new projections – is Vicinity, which operates a steam plant on the shore of the Charles River near the Longfellow Bridge and plans to convert to electric-powered steam turbines. The facility, formerly the Cambridge Electric Light power plant, now produces heat and power with a mix of fuels to generate steam for customers in Cambridge and Boston.

The change would add to Eversource’s problems, increasing the load burden by 84 megawatts, Eversource witnesses testified. Vicinity plans to convert the first of its two turbines by the end of 2024, raising demand by 42 megawatts, Eversource director of transmission planning Jacob Lucas said. Vicinity is already advertising its new “eSteam” product as a move to cleaner energy; according to the company, it has “deconstructed” one of its turbines in preparation for the change.

Eversource will have to offer “interruptible” power to the first turbine until the new substation starts operating in 2030, Lucas said. “What Eversource was trying to do is provide some means by which Vicinity would be able to serve its customers this electrified steam product before then, and that’s what we’re working to accomplish,” he said. The new substation and distribution network configuration “significantly offloads the amount of power that needs to flow from North Cambridge into Kendall to supply that load,” Lucas said.

IQHQ is the first customer

Vicinity’s plans came under scrutiny from siting board staff, who wanted to know whether the conversion would attract customers who now get power from Eversource for heat and how energy-efficient the new boilers would be. “When you’re talking about using electricity to make steam to provide downstream heating to customers, [it] does bring up the question of how else could customers heat their premises if they weren’t using steam,” siting board director Andrew Greene said. “What if Vicinity’s customers were essentially using electricity through a heat pump technology to heat their premises instead of the steam-producing process?· Wouldn’t that be more energy-efficient?”

Eversource’s Chatterjee agreed that heat pumps were probably more efficient but said Eversource did not know how many Vicinity customers were in Cambridge; the Kendall plant is one of three serving Boston and Cambridge. According to Vicinity’s website, the first customer who has signed up for Vicinity’s electric-powered steam is IQHQ, owner of two projects in Boston’s Fenway neighborhood. Vicinity also says on its website that it plans to install heat pumps that will operate using water from the Charles River rather than air temperature, but does not provide details.

Adding urgency

Greene asked the Eversource panel of witnesses for their opinion about “whether the Siting Board should regard the Vicinity use of electricity in a favorable light or whether we should be concerned that it’s perhaps an inefficient use of energy and potentially prone to producing more emissions for the same amount of useful energy provided, despite the characterization of it as eSteam.”

They demurred. “We have a statutory obligation to conduct a study and determine any transmission or distribution constraints that ensue from any customer load interconnection requests, and that is what we have done at this point,” Chatterjee said. He added that the Vicinity conversion did not figure into Eversource’s calculation of the need for the new substation and distribution system.

The electrification of Vicinity’s steam turbines “is not a driver for the project by any stretch – if only it exacerbates the transmission issue substantially and drives a higher urgency of the station,” he said.