Thermal energy networks move heat among many buildings and infrastructure facilities, like subway tunnels and wastewater treatment plants. Thermal energy networks do not combust fuel or generate heat; they simply distribute it, taking excess heat from where it isn’t wanted and delivering it to buildings that need it. Closed loops of water-filled pipes balance, redistribute, and store heat among multiple buildings and other heat sinks and sources, such as wastewater treatment plants, subway systems, and the earth beneath our feet. The pipe loops are connected to highly efficient heat pumps inside buildings to provide heating, cooling, and domestic hot water. Thermal energy networks are carbon- and pollution-free (assuming the electricity source for the pumps is renewable solar, wind, or hydro) and use much less electricity than other electric heating and cooling systems, such as baseboard heaters and conventional air conditioners. This eases the demand for electricity generation and transmission and smooths the peaks in electricity load during periods of extreme heat or cold, reducing the likelihood of blackouts.

Thermal energy networks use the same basic technology as geothermal systems. Geothermal systems are efficient because they capture ambient, low-temperature underground heat (55ºF year-round in New York) through deep boreholes and deliver it to indoor heat pumps. Ground-source geothermal heat pumps don’t have to work as hard as air-source heat pumps: they only need to raise or lower the temperature slightly from that constant, moderate 55º base, so they use less electricity and save money. District geothermal connects many buildings to one system of boreholes for improved economies of scale: shared boreholes and loops cost less in total than boreholes for each individual building. Thermal energy networks are a step up from geothermal: they may not require boreholes but instead capture the excess heat from and deliver it to buildings and infrastructure facilities like wastewater treatment plants. (Many thermal energy network systems also incorporate some boreholes, however, for heat storage and increased reliability.) thermal energy network connected heat pumps deliver the heat captured from other sources to warm the air or to heat water in buildings that need it. The process is reversed to cool buildings, and the heat pumps extract heat, delivering it to the pipes and then to buildings that need warmth, domestic water tanks, or storage, either underground or in infrastructure facilities.

Thermal energy is, simply, heat.

Geothermal energy is heat (thermal) from the ground (geo).

Two primary sources of underground heat can be harnessed to meet human needs: thermal water heated by the earth’s core, and subsurface ground heat below ten feet with consistent low temperatures year-round.

Magma-heated water is found in areas with a lot of volcanic activity, such as along the Pacific Rim. That superheated water can reach the surface through cracks, geysers, and pipes, emitting steam, which can be used to turn turbines to produce electricity. This is the most renewable, cleanest, lowest-cost, dispatchable form of electricity. Magma-heated water can also be used directly for bathing:

Therma is the Latin word for hot baths, and for many millennia, communities close to volcanic hot springs have used it for bathing. Old Roman baths are still used in Italy and England today, and natural hot springs are popular for relaxing and bathing wherever they are found.

Subsurface or low-temperature ground heat is a resource for regions like the eastern United States, where that magma-heated water is miles below us and unreachable. In these areas, the geothermal energy used is the constant ambient temperature underground, about 55°F in New York year round. This heat is captured by sinking closed pipe loops into boreholes, typically 500 to 1,000 feet deep; the water in the pipes absorbs the heat and then delivers it to heat pumps in buildings, which efficiently extract and amplify that heat to raise the temperature indoors, returning the now cooled water to the borehole to be returned to 55°F. For cooling, the system is reversed: the heat pump removes heat from the building and transfers it to the water in the pipes, which delivers it underground to be stored and to return the water temperature in the pipe loops to 55°F. Geothermal heat pump systems sharply cut electricity use and emit no greenhouse gasses or other pollutants. Geothermal heat systems in the north-east always use this kind of ambient underground heat.

Thermal energy networks do not burn fuel or generate heat; instead, they simply remove excess heat from buildings and distribute it to buildings needing heat. Your temperature choice to heat or cool is delivered to your home or business using a heat pump. Heat pumps also reduce electricity demand because they are a highly efficient technology. Thus, they will increase grid reliability during and beyond the transition since less electricity is needed to operate a heat pump.

Thermal energy networks can drive a rapid, just transition from fracked gas and “renewable” methane. The same union labor that builds gas pipelines is needed for thermal energy network construction, thus, generating thousands of good new jobs.

While investor-owned utilities can develop and own thermal energy networks, they won’t have a monopoly: municipalities, community groups, and housing co-ops can also create and own them, eliminating the profits that make up around 10% of utility bills.

Thermal energy networks and district geothermal require the same union labor as fracked gas utilities. They are key to a just transition for workers away from gas and towards beneficial electrification. Labor unions were central to writing and passing the Utility Thermal Energy Network and Jobs Act into law in 2022. The unions collaborated with community-based organizations, the utilities, and legislators to pass a law requiring the seven largest investor-owned utilities to develop one or more pilot projects each that would demonstrate the feasibility and economic savings of thermal energy networks and test thermal energy networks in varied building stocks and using different sinks and sources; they also explore different business models. The utilities should also collaborate with unions in developing new and expanding existing workforce development and job training programs in disadvantaged communities as defined by the New York State Climate Action Plan. The unions should include the American Federation of Labor and Congress of Industrial Organizations (AFL-CIO), the Building and Construction Trades Council of Greater New York, and other unions whose members will likely build these projects.

Disadvantaged communities are harmed first and worst by climate change and immediately by burning fossil fuels in their homes for heat and hot water and in their neighborhoods for electricity generation. Low—and middle-income Black and brown New Yorkers are in desperate need of healthy, clean, and affordable heating, cooling, and hot water. Thermal energy networks can supply that affordably and at efficient neighborhood scales.

Thermal energy networks and district geothermal in low-income communities are also solutions to the problem of skyrocketing gas prices for households that can’t afford to electrify their buildings individually. As fewer and fewer buildings use fracked gas, the shrinking number of remaining accounts will be sharing the financial responsibility for the operations and management costs of the entire network. This phenomenon is known as “stranded assets.” Stranded assets emerge when an energy asset, like a gas system or fossil fuels, has become less valuable or unusable and loses its value. The utilities that continue to push to expand obsolete, climate-killing gas infrastructure should be held responsible for the financial losses that are certain to follow, but they will instead transfer those costs to the customers who can least afford it, abetted by the state utility regulators. Acting quickly to develop and build thermal energy networks in disadvantaged communities will protect them from being stuck with gas and monthly bills that will soar to literally thousands of dollars.

Further Reading:

A geothermal energy boom could be coming to Chicago’s South Side

Duke stranded gas assets could cost customers $4.8B, report finds

Thermal energy networks link diverse buildings with varied patterns of use so that the demands for heating and cooling are balanced simultaneously and over the seasons. In considering ideal sites for thermal energy networks, Sane Energy has been working with affordable housing complexes, and we’ve started reaching out to parents and organizations in the green and healthy schools movement to inform them about the potential benefits of thermal energy networks anchored by schools. Schools using thermal energy networks would have clean indoor and outdoor air, comfortable heating in winter and cooling in summer (which few public schools in New York now have) from a single technology upgrade, rooftops free of heating, ventilation, and air conditioning equipment so that solar panels could be installed to power the heat pumps, and reliability, resilience, low maintenance, and low operating costs. As the climate crisis worsens and extreme heat, cold, flooding, blackouts, and fires more frequently require reliably heated and cooled shelters, a role frequently served by schools and libraries, these public institutions would benefit from anchoring thermal energy networks with solar electricity and battery storage backup.

Sane Energy is also talking with town leaders in the Hudson Valley and upstate, learning about their needs and educating and informing executives, officials, and community advocates about the long-term benefits of moving their municipal complexes and neighboring buildings from fossil fuel systems to thermal energy networks. We have also engaged the New York City Housing Authority (NYCHA) over a National Grid pilot project for a NYCHA facility in Brooklyn to ensure that the project is properly designed. Low-income residents must not be used as guinea pigs for poorly engineered energy experiments. We also want to encourage NYCHA to develop geothermal and thermal energy network systems for their housing complexes instead of using less efficient, less resilient air source heat pumps.