solar panelIllustration of a networked geothermal system along a street. Water circulates through boreholes and a shared loop of pipe and carries heat away from where it is not wanted and toward where it is. Then, heating and cooling are supplied by a ground-source heat pump, running on grid electricity, with a thermostat that building occupants control.  Source: HEET

Study to see whether East Arlington could benefit from this technology

Rooftop solar panels have become an unremarkable sight in Arlington, along with electric vehicles and air-source heat pumps. For those with both the resources and the motivation to move away from burning fossil fuels, electrifying homes and vehicles chips away at greenhouse-gas emissions, the biggest driver of climate change.

But networked geothermal energy for both heating and cooling—supplying an entire neighborhood with climate control delivered through a system of underground pipes connected to ground-source heat pumps—represents a further frontier in the clean-energy effort.

With a $50,000 grant from HEET (Home Energy Efficiency Team) through its Kickstart Massachusetts program, officials with the Town of Arlington now are beginning the process to evaluate whether such a system could make sense to install eventually in the East Arlington neighborhood that includes both Thompson School, the local public K-5 campus, and Menotomy Manor, run by the Arlington Housing Authority for low-income families with children. This feasibility study could be complete by year's end.

Unlike electrification efforts made one homeowner at a time, networked geothermal can move many households off natural gas in one fell swoop. All 179 units at Menotomy Manor use natural gas for heating, cooking and hot water, according to the AHA’s executive director, Jack Nagle. Cooling currently comes only from window units—which tend to be a relatively less-efficient option — purchased by tenants themselves. 

Thompson School currently has an electrified cooling system but also relies on natural gas for heating and hot water, said the town’s facilities director, Rob Behrent. He went on: “Geothermal is the most energy-efficient system that operates reliably and is readily available today. The factor limiting installation is property size,” he said — and the Thompson School offers plenty of land for “the correct [number] of ground wells with the proper amount of spacing for the heating and cooling requirements for the building.” Picture1Another artist's illustration of an outdoor geothermal network. Photo courtesy: Eversource

Of course, actually designing and constructing such a system would cost much more than the $50,000 feasibility (study) grant.

At the same time, the alternative—maintaining the extant natural-gas system — also involves large numbers. A 2019 study of networked geothermal’s potential in Massachusetts found that “Massachusetts has one of the oldest natural gas distribution systems in the country, with more than 6,000 miles of aging and leak-prone pipes, or approximately 26 percent of the distribution system. Based on this information, HEET has estimated that the replacement of this infrastructure, which is expected to take two or more decades to complete, could ultimately cost utility customers more than $9 billion.”

That cost would be spread over many years and likely would end up being absorbed by a shrinking number of natural-gas customers as people who can choose to do so move away from fossil fuels.

Arlington’s Kickstart grant was awarded in March, and the town’s sustainability manager, Talia Fox, says that the town's Department of Planning and Community Development is still in the process of hiring a consultant for the study.

The aim, she says, is “to understand what scale and design of networked geothermal system might be possible for the general neighborhood and [the] select few buildings we’ve identified so far. We do not have clarity at this point on governance or ownership structure, permitting requirements or overall costs. There has been some community engagement, but we have not yet begun the engagement process in earnest.”

AHA eager to learn more

For his part, Jack Nagle of AHA is already “very excited” about the potential for reducing both greenhouse-gas emissions and utility bills for the 500 or so residents of Menotomy Manor.

“Even before the geothermal project was in the works, we were trying to understand how to electrify the site,” he told YourArlington recently.

AHA for some time has been gradually electrifying its properties, with Winslow Towers — the Arlington Center high-rise for low-income seniors and people with disabilities — now run entirely on electricity. The air-source heat pumps installed there through Mass Save, he notes, have all been through one or two winters without any need for the backup baseboard heating that was installed just in case. 

Initially, according to Nagle, the AHA had in mind air-source heat pumps for Menotomy Manor as well. But he now sees geothermal heating and cooling as potentially even better.

“It’s more expensive to set it up,” he said, “but less so once installed.” 

So far, he acknowledges, people living in and around Menotomy Manor don’t know any more about the project than any other Arlington residents do.

And, until the feasibility study wraps up, which should be by the end of 2024, many questions remain open, Fox told YourArlington.

"We don’t have the exact boundaries of the project because this is part of what the study will determine: what size of system could accommodate what buildings and in what configuration/where. The idea is potentially to include some of the residences around Thompson and Menotomy Manor, but we don’t know exactly where yet."

Framingham leads the way nationaly

Meanwhile, the first utility-scale networked geothermal project in the nation started operating in early June — only 20 miles away, in Framingham. That system, along with others in the works in greater Boston, offers a glimpse of the impacts and benefits that may lie ahead for East Arlington.

Images of 30-foot-tall drills, heavy equipment and eight-inch-wide PVC pipes stamped “Geothermal” soon greet anyone who searches for news coverage of Framingham's networked geothermal project.

In a parking lot, on Framingham Housing Authority property and behind a fire station, Eversource drilled a total of 90 boreholes 600 to 700 feet into bedrock, where the temperature is a steady 55 degrees Fahrenheit year-round.

Water circulating through the vertical boreholes, and then a horizontal loop running under the street connecting all the buildings being served, carries heat away from where it’s not wanted and toward where it is, depending on the season. WBUR ran a story on the Framingham system here >>

In each of the 32 residential and five commercial buildings connected to the loop, heating and cooling are supplied by a ground-source heat pump, running on grid electricity, with a thermostat the occupants control. The technology is not new—refrigerators and air conditioners are heat pumps too, and “networked geothermal systems have been used for decades on college campuses,” according to HEET. They don’t generate electricity but instead replace ways of heating and cooling a building that are less efficient, burn fossil fuels or both.

Constant temperature of bedrock key to technology

Fox notes that Arlington “has explored and continues to explore geothermal in the form of ground-source heat pumps for a number of school buildings.” For example, at the Jason Russell House in Arlington Center, a ground-source heat pump now supplies heating and cooling. 

Ground-source heat pumps work more efficiently than air-source heat pumps because of the more constant temperature of bedrock — hence Nagle’s interest in them. A well-designed system ensures that heat is never wasted but instead is stored or directed elsewhere. At times, one large building (such as a supermarket or ice rink) may be shedding heat while smaller ones are taking it up.

As the climate warms, the 2019 geothermal study cited above found, “Massachusetts [is] likely to undergo a shift from a heating dominant to a cooling dominant climate by 2070.” Because of their efficiency, HEET officials argue, networked geothermal systems that supply that cooling could reduce “the projected build-out of the electrical grid while curbing emissions at the speed and scale needed to tackle the challenge to decarbonize our building stock.

 A Department of Energy study quantifying how much less electrical infrastructure would be needed, if ground-source heat pumps were widely deployed, can be viewed here >>

But each networked geothermal system must be custom-built. In Framingham, Eversource technicians have been installing, house by house, heat pumps, air handlers and ductwork, along with electric resistance heating as a backup in case the system doesn’t work as designed. Before that, they weatherized and upgraded electrical systems as needed. Some buildings have been converted from gas, others from oil heating.

In the pumphouse are more redundant systems: a boiler to raise the temperature of the water if the system ever can’t meet the demand for heating, and a backup cooling system. The system cost about $14.7 million to design and build, with construction taking a full year.

'Bumps in the road'

In an update to Framingham residents in October 2023, Eric Bosworth, a senior program manager in Eversource’s clean technologies department, noted that workers had encountered “bumps in the road” typical of any infrastructure project; as with gas and water main work, digging uncovers objects no one knew were there. Last summer’s abundant rain also delayed some trench work.

“It’s really tough to get in there, and it’s really expensive to get in there and make geothermal work” in Massachusetts, National Grid’s decarbonization technologies manager, Bill Foley, told CommonWealth Beacon. Moreover, if the state’s relatively old and inefficient housing stock isn’t retrofitted to use less energy—insulation, replacing leaky windows — then any networked geothermal system will have to be oversized (and thus will cost more) in order to compensate.

Nevertheless, National Grid is following Eversource’s lead, with a networked geothermal project under construction in Lowell that is to include replacing gas stoves and other appliances. 

Another is in the planning stages at the Franklin Field housing project in Dorchester, which has seven apartment buildings. There, the Boston Housing Authority “will be responsible for all work … necessary to convert these buildings from gas heating to networked geothermal heating and cooling, including retrofits, electrical upgrades and appliance and heating equipment replacement.

Residents probably will have to relocate for a few days at some point during construction. BHA administrator Kenzie Bok told the Dorchester Reporter that a replacement for the complex’s aging gas boiler system was “all spec-ed out and ready to go” when Mayor Michelle Wu, in January 2023, challenged the BHA to retire its gas heating assets and decarbonize its properties by 2030

How Arlington fits in

Eversource’s project in Framingham and National Grid’s in Lowell and Dorchester both are pilots, meant to gather data that will help the utilities understand what it takes for networked geothermal to work both technically and financially. (After two years, Eversource plans to decide whether to continue operating the Framingham project, find a buyer or decommission it and restore the “original heating systems or better” in the participating buildings.)

In principle, said Audrey Schulman, founder of HEET and now director of its affiliate HEETLabs, “Each install becomes better and better and cheaper to install and functions more efficiently.” 

The Framingham, Lowell and Dorchster sites share features with Arlington’s: a mix of building types, energy demands and income levels, which HEET looks for in evaluating applications. In Dorchester and Arlington, housing- authority tenants stand to gain efficient, low-cost air conditioning instead of having to purchase window units.

Nagle predicts that cooling likely would make up the most attractive part of the package, along with lower utility bills, for many Menotomy Manor residents.

While some will also welcome electric stoves, others may not.

He emphasized, “We don’t want to talk about hypotheticals until it’s something we can commit to.”

East Arlington’s system would be bigger than Framingham’s and not funded by a gas utility—at least for now. Those in Framingham and Lowell are, partly because, as HEET puts it, “Utility-scale geothermal networks leverage the utilities’ right-of-way in the street along with their capital financing, existing workforce and customer base. Installation and building retrofit costs could be paid for up front by the utilities and spread across the entire customer base over many years.” 

Now that Arlington has joined the state’s Fossil-Fuel Free Building pilot, networked geothermal projects could offer gas utility companies a model for growth that doesn’t depend on gas. In one scenario, existing gas pipes could be converted to geothermal — the feasibility study will presumably examine whether that can happen in East Arlington. In Framingham, Eversouce laid new geothermal pipes, so buildings in the network can still use gas for cooking and hot water.

The state has also been moving away from permitting new gas infrastructure, notably with the Massachusetts Department of Public Utilities’ Order 20-80 in December 2023. Among other legislation seeking to move the state past gas, a bill now before the state Senate Ways and Means Committee would allow gas utilities to meet their obligation to provide service through “utility-scale non-emitting renewable thermal energy.” In March, Washington became the first state to pass such legislation; Massachusetts possibly could be the second.


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This news-feature by YourArlington freelancer Catherine Brewster was published Monday, July 8, 2024.

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