Geothermal networks link homes and businesses to the warmth and cooling provided by the earth. Courtesy: HEET
This year has brought a big shake-up in Washington and an even bigger turn of fortune for renewable energy. Immediately upon taking office, President Trump issued a slew of executive orders pausing leases on offshore wind and taking steps to reverse incentives for renewable technology like electric vehicles. But there’s one renewable energy source that even the Trump administration appears to support: geothermal energy.
Geothermal power taps the heat stored deep within the earth to heat and cool our buildings. It’s a potentially potent source of energy that is constant, ubiquitous, and free. (Perhaps that is why the Trump administration listed it as an “essential energy resource” during its declared “energy emergency” – solar, wind, and battery storage weren’t so lucky.) In fact, networked geothermal energy is already bearing fruit in New England in projects that are now heating dozens of homes.
The latest geothermal breakthrough may be on the horizon in Connecticut, where state lawmakers recently considered several bills to support the development of geothermal networks tapping into the heat stored deep within the earth. (In May, lawmakers included language in an energy bill that would create a thermal energy network program but did not commit to funding it.)
And clearly, geothermal could be a game changer for Connecticut, where more than 40% of homes burn heating oil for warmth and 37% use natural gas. Pollution from heating buildings accounts for about 30% of the state’s carbon emissions. But if more homes and businesses could access geothermal, the number of buildings dependent on fossil fuels for heating could fall dramatically, and along with that, the amount of carbon pollution spewed into the air.
“Connecticut’s reliance on inefficient fossil fuel heating is costly and produces health-harming pollution,” says Shannon Laun, CLF vice president for Connecticut. “Shifting towards highly efficient heat pumps and thermal energy networks would benefit the health and well-being of everyone living here.”
How Geothermal Energy Works
Beneath our feet, the Earth’s surface warms and cools with the seasons. But lower down, soil and rock stay at a constant temperature — usually between 50 and 60 degrees Fahrenheit. Geothermal taps this heat using a piping system called a “loop” to circulate water between the earth, a ground source heat pump, and a building.
Geothermal networks go one step further by connecting entire neighborhoods with the year-round warmth beneath the Earth’s surface. That involves laying water-filled pipes under streets, just like we have with gas. The water in these pipes absorbs the ground temperature of the earth and delivers it to buildings. The pipes also connect buildings with different heating needs, so energy never gets wasted.
Instead, it is exchanged between buildings or stored in the ground until needed. In the winter, heat pumps move heat from the ground into the home, and the process is reversed in the summer to keep buildings cool. Networked geothermal could provide a viable heating source for whole neighborhoods and cities.
“When you have different load types, like commercial and residential buildings, all connected on the same loop, it requires less electricity to power,” explains Laun. “So, it’s not only more efficient but also more affordable. Plus, geothermal ground source heat pumps provide access to cooling as well as heating. When you get a heat pump installed in a building that previously lacked air conditioning, residents get year-round efficient heating and cooling, which is really important because extreme heat waves can have deadly consequences.”
In Massachusetts, A Test Case Swings Into Action
Laun says she has seen growing momentum for geothermal networks in Connecticut, partly because of successes in other states. One such success is right next door in Massachusetts, where Eversource commissioned the country’s first gas utility-installed networked geothermal system last summer in the city of Framingham. The pilot connected 130 buildings to “geo” pipe on a mile-long main loop. Seven commercial buildings, a fire station, a school, dozens of single-family homes, and apartments owned by the Framingham Housing Authority are now heated and cooled using the heat beneath the city. Residents are expecting to benefit from substantially lower utility bills even though they also now enjoy air-conditioning they didn’t have before. The project was conceived by HEET, a Boston-based nonprofit and CLF partner dedicated to ethical and efficient thermal energy transition.
While costs for building conversions were higher than expected, according to Zeyneb Magavi, executive director of HEET, the overall outcomes are encouraging. And in a planned expansion of the Framingham project, Magavi says the next segment will double the total amount of energy delivered for half the cost of the first.
Meanwhile, last year, National Grid also announced a pilot project to replace an existing gas network of 129 units with a geothermal network at the Boston Housing Authority’s Franklin Field Apartments in Dorchester. More than 20 other demonstration projects are moving forward across the country.
Magavi describes geothermal energy networks as “an enormous opportunity” to use local thermal energy resources and heat that would otherwise be wasted.
Not only is geothermal energy an obvious solution to the vexing problem of heating and cooling, but it’s a relatively easy transition for gas utilities that already have the workforce, equipment, and administrative staff to develop a thermal utility, says Magavi.
Things Are Heating Up in Connecticut
Eversource is also seeking permission from the Connecticut utility regulator to build a geothermal network pilot similar to its Framingham project. As of this writing, details have not yet been decided. However, unlike in Massachusetts, this pilot project would develop a geothermal network for new construction to minimize project costs.
“It’s a great first step, but ultimately, we need to deploy networked geothermal more broadly as a way of transitioning off the gas system and electrifying buildings,” says Laun. “That means retrofitting existing homes to take advantage of the efficiency and affordability of geothermal heating. It’s not going to be the solution everywhere, but it definitely can play a significant role in eliminating fossil fuels from the building sector.”
