​​THE GROUND BENEATH Massachusetts is key to a relatively new strategy to decarbonize the state’s building stock within the next decade. Deep beneath Framingham, Lowell, and Boston, pipes will exchange heat between homes and commercial buildings with the rock below, creating geothermal heating and cooling systems aimed at saving residents money while phasing out dependence on nonrenewable energy.

A first association with geothermal power is usually visible hot springs or geysers that bubble along the borders of tectonic plates. US states like California and Nevada – as well as almost 30 countries around the world – augment their clean energy resources through geothermal power plants, which use heat from rocks deep below the ground to flash water into steam at the surface and drive turbines.

But geothermal heating and cooling systems are still a rarity, with Massachusetts utilities exploring new ways to decarbonize the systems through systems of pipes and deep wells that exchange heat.

“What we’re talking about here doesn’t require tectonic plate boundaries,” National Grid’s future of heat solutions director Owen Brady-Traczyk said on The Codcast. “It doesn’t require specific geology. It doesn’t require any of the sort of conditions that you might otherwise have thought would be required for geothermal. It just requires depth.”

Residents are getting more familiar with heat pumps – temperature systems that exchange warmer and cooler air between a home and the outside – as a greener way to heat and cool their homes. Geothermal systems extend the heat pumps into the earth, which fluctuates less in temperature than the air. Liquid-filled pipes transfer underground heat up to buildings during the winter and sink warmth into the ground for cooling during the summer.

Eversource broke ground on a networked geothermal system in Framingham last June, which will heat and cool a neighborhood’s 32 residential and five commercial buildings. National Grid dug its first borehole for a UMass Lowell networked geothermal pilot last April. As the Lowell project readies for construction, Boston Mayor Michelle Wu and National Grid announced the utility’s second pilot at the Franklin Field Apartments owned by the Boston Housing Authority.

The pilots are learning exercises as much as energy retrofit projects. 

“What we’re finding at National Grid is geothermal is really tough,” said Bill Foley, the company’s decarbonization technologies manager, who joined Brady-Traczyk on The Codcast. “So if you look at the housing stock in Boston, the housing stock is very old. With the general building stock – commercial, residential, industrial – it’s really tough to get in there, and it’s really expensive to get in there and make geothermal work.”

The main barriers to geothermal systems tend to be high upfront costs and the initial disturbance as drillers plunge boreholes hundreds of feet into the earth. The federal Inflation Reduction Act has increased some of the incentives available for the technology, Brady-Traczyk said, and once the system is in place, it should power along smoothly and silently beneath roads, walkways, or central courtyards. 

Geothermal heating is both a “high-cost” and “high-performance” system, Brady-Traczyk said. “So if there are ways that we can make the economics work for customers, they end up with something that uses a very low amount of energy on the back end,” he said. “It’s just then a question of how able we are to put all of that together and to make it work for individuals who might not have a lot of dollars to be able to invest in a system.”

In Foley’s view, geothermal systems are easiest to implement if a development can essentially start from the studs, building geothermal heating systems into the initial design. But existing communities like the Franklin Field public housing apartments in Boston offer a place to design and build networked geothermal systems in centralized locations to allow heat exchange not just between buildings and the earth, but also potentially between buildings themselves if one structure is producing heat that another could use. 

“One of the ways that we on the public side can most impact the private market is by creating a market ourselves and by leading where they should follow,” Boston Housing Authority head Kenzie Bok told CommonWealth Beacon in October as the city assessed possible sites for geothermal systems. 

The project offers renewable and affordable heating systems for public housing residents, plus the utilities get a test case on multifamily residential campuses, she noted. “I think that if that’s something that we can do, and we can do it successfully for public housing development in Boston, then it opens up the possibility to do geothermal networks more broadly across multi-family residential.”