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A tried-and-true technology brings clean, affordable heating and cooling to communities
After decades of relative obscurity—at least in the U.S.—geothermal is rapidly gaining acceptance as a powerful source of renewable energy. Companies like Fervo Energy have made headlines recently for their efforts to generate electricity by drilling deep into the earth, where temperatures reach hundreds of degrees, using technically complex, and potentially high-risk approaches.
The heat beneath our feet
However, there is another kind of geothermal energy that sits almost right beneath our feet. That energy is used not to generate electricity, but to provide heating and cooling. The core technology—the ground-source heat pump—has been around for many decades and is fairly straightforward. It’s also remarkably efficient—more on that in a minute.
The recent innovation with this kind of geothermal isn’t the equipment—it’s networking the components over wider geographic areas and using a utility business model. Rather than individual homeowners paying for single geothermal systems, gas utilities are beginning to pilot networked geothermal installations that connect entire neighborhoods, including residential and commercial buildings. With this model, gas utilities can leverage not only their right-of-way in the street, but their capital financing, which amortizes cost over decades and across the entire customer base, along with their skilled workforce.
How do such systems work?
A closed, horizontal loop of pipe filled with water sits below the frostline, where in New England the ambient temperature is 55 ℉. A set of vertical boreholes goes down several hundred feet and ties into the horizontal loop. Buildings are connected to the loop, and a ground-source heat pump in each building delivers heat in the winter and removes heat in the summer. The system is powered by electricity, which means that when the grid is fully green, networked geothermal will be entirely emissions-free.
Back to efficiency
In a networked geothermal system, when heat is removed from buildings in the summer, that thermal energy isn’t vented outdoors; it goes back into the ground, where some of it is absorbed by the bedrock and sent back into buildings in the winter. “Rejected” heat can also be transferred between buildings that have varying heating and cooling needs.
This is one reason networked geothermal is so efficient. The most efficient gas furnaces have a coefficient of performance (COP) of less than 1—meaning for every unit of fuel burned, less than one unit of heat is generated. Networked geothermal systems have been documented to range between 6 and 9 times that efficiency—meaning they significantly reduce greenhouse gas emissions. In addition, once our buildings are fully electrified, these systems will also greatly reduce peak demand on the electric grid when compared to other sources of electric heat, such as baseboards.
Increased safety and air quality
Because there is no fuel and no combustion with networked geothermal, there is no risk of explosions (remember the 2018 Merrimack Valley tragedy in Massachusetts), no outdoor gas leaks (which kill trees), and no indoor air pollutants (which can cause or worsen health problems).
Gas utilities in Massachusetts are leading the way
The two largest gas utilities in Massachusetts are front-runners in pioneering the “gas to geo” approach, which is being explored or legislated in states across the country. Eversource Gas has the first-in-the-nation utility networked geothermal installation going in the ground right now in Framingham, which will serve about 140 customers in nearly 40 buildings. National Grid also has an installation in progress in Lowell.
Building in equity and environmental justice
A phased transition from gas to networked geothermal led by the utilities can, and must, ensure that underserved and low-income communities are included equitably and with adequate financial support for the necessary home efficiency and appliance upgrades that accompany the shift from natural gas.
The smart alternative to costly gas pipe replacement
Massachusetts ratepayers are on a course to spend an estimated $40 billion over the next 20 years replacing hazardous, old, leaking gas pipes. Similar expenditures are underway wherever natural gas is delivered to homes and businesses. Redirecting our energy investment dollars away from natural gas infrastructure to networked geothermal will help us build the utility of the future—one that delivers safe, renewable, non-combusting, affordable heating and cooling, along with good paying jobs and local economic benefits.
You can learn more about networked geothermal on the open-source Wiki (www.gastogeo.wiki/wiki/Main_Page) and at HEET.org, a nonprofit climate-solutions incubator working to advance an equitable transition from natural gas to utility networked geothermal. To register your interest in networked geothermal service for your neighborhood, enter your name on the map at https://bit.ly/NetworkGeothermalSurvey.
Laurel Kayne is the director of communications at HEET (Home Energy Efficiency Team). An ardent green enthusiast, Laurel is delighted to apply her energy and skills to helping HEET increase its impact nationwide and accelerate the transition off of fossil fuels.
Networked geothermal moves heat into and out of buildings. The primary source of heat is the ambient temperature underground, though the systems also transfer “waste” heat between buildings with different heating and cooling needs, increasing efficiency. (HEET)