Photos courtesy of the Daily Princetonian.

The shop floor of TIGER

The shop floor of TIGER is the heart of Princeton’s geo-exchange system. It houses hulking heat pumps, air-dirt separators, chillers, and other mechanical components necessary to heat and cool campus. Photo by Raphaela Gold ’26.

Water is all around me. It rushes through cheerfully colored gleaming pipes on the way to be cleaned, heated up, cooled down, flung out to the opposite side of campus, and brought back to begin the journey again. I’m standing on the shop floor of Princeton’s new Thermally Integrated Geo-Exchange Resource building, or TIGER for short (of course). This is the heart of a circulatory system of energy that pumps water to heat and cool campus buildings. The smell of rubber greets my nose as I begin to walk through the whining blocks of machinery around me. 

“Now, this isn’t brand new technology, but it is a new way of using this technology,” Ted Borer, Princeton’s Energy Plant Manager, tells me as we tour the facility. Bright eyes peering through silver spectacles, sporting close-cropped haircut and a plaid shirt, Borer speaks with the enthusiasm of a young science teacher and the authority of a power industry veteran. He was hired almost 30 years ago to help build the fossil fuel power plant that generates electricity and heat for campus. He is now helping install a new system, dubbed “geo-exchange,” to gradually replace the older plant. For centuries, Princeton has heated campus with fire, fueled first by wood, then coal, then oil, then finally fossil gas in 1996. With geo-exchange, though, Princeton has begun to adopt water as a means of heating and cooling, a momentous shift. Like many other institutions, the university has done so for climate reasons. Renouncing fire makes it possible to avoid the carbon emissions that choke us and our planet.

We don’t usually think about the sheer amount of resources it takes to keep Princeton running. To some extent, that’s the point: we’re here, we’re told, to learn, not to worry about the more mundane infrastructure around us. Energy is merely at the periphery. In our time of climate crisis, this separation can be dangerous. Without understanding our energy sources – how they operate, how much they pollute and consume – it’s more difficult to discern exactly what is required to change how we manage energy at and beyond Princeton to combat the climate crisis. It’s also difficult to see the assumptions we hold about how to treat the land and resources we use to make that energy. 

Borer and his team, though, have had Princeton’s energy front and center in his mind for three decades. As the university rolls out geo-exchange, he’s more excited than ever.

The system that geo-exchange will mostly replace, cogeneration, is already pretty efficient for a fossil fuel plant. Cogeneration generates both electricity and heat for campus using a combined combustion process, making it more efficient than the usual fossil gas plant. Nevertheless, according to university reports, the aging plant emits around 73,000 tons of carbon dioxide annually. That’s around as much as 8,600 average houses a year. Plus, contained within the plant’s billowing exhaust are small amounts of unpleasant chemicals that escape engineering controls: carbon monoxide, nitrogen oxide, and other volatile organic compounds, according to internal monitoring reports. Even if this air pollution has fallen within permitting limits set by New Jersey’s Department of Environmental Protection (DEP), when combined with emissions from the other plants in the state, it can pose long-term health risks for living organisms. In 2016, Princeton’s administration, feeling a new urgency to address the climate crisis, set a goal to decarbonize campus by 2046, just four years before our government plans to achieve net zero nationally. 

To figure out how to replace the cogeneration plant, the university hired engineering consulting firm Burns & McDonnell, and they eventually settled on an alternative: geo-exchange. “[Geo-exchange] rose to the top because it had the ability to improve reliability, increase sustainability, reduce carbon emissions, and it was the lowest life cycle cost option of all the options to achieve carbon neutrality,” says Justin Grissom, a mechanical engineer at Burns & McDonnell who has helped manage the geo-exchange project. Princeton got to work, breaking ground for geo-exchange in 2022.

Heat pumps in TIGER

Heat pumps in TIGER move heated and chilled water around campus, keeping everything at the right temperature. Photo by Raphaela Gold ’26.

On an engineering level, the geo-exchange system I find myself in is remarkably elegant. Like the heart of a circulatory system, massive heat pumps around me push water through a complex network of pipes, circulating heat instead of blood. To heat up a building, the pumps direct hot water to that building and drop off the water’s stored heat; the now-cooled water comes back to pick up more heat from a hot water storage tank before rushing off to where it’s needed. To cool campus down, the pumps perform a similar function with cold water instead of hot. 

Able to regulate campus’ temperature across days and months, the geo-exchange system can also manage temperatures across seasons by using a huge array of deep subterranean wells that contractors are in the process of drilling. In the summer, the cold water which picks up heat may be pumped down one of the wells instead of dropping off its heat in one of the shorter-term storage tanks. As this now-heated water moves down the wells, its heat radiates out to warm up the surrounding rock by 15 to 20 degrees. Come winter, the same pumps will then run cold water down these same boreholes to collect the previously-stored heat and distribute it to the rest of campus. 

The seasonal aspect differentiates Princeton’s project from other large heat pump systems like that of Stanford’s, which doesn’t require an extensive system of wells. “[At] Stanford, the temperature is pretty even all year,” Borer says. “Here, it gets really cold. It gets really hot… We need to be able to capture the heat from the summer and deliver it in the winter.” 

While this all may seem like a simple process, its implications are huge. Most heating systems rely on devices that generate energy, converting the energy locked within, say, ancient, compressed plant matter into more usable forms. In that conversion process, a lot of energy gets lost: in the case of Princeton’s cogeneration, 20 percent. Because geo-exchange instead transfers energy, it’s far more efficient. Borer tells me that early tests show that the system can use one unit of energy to make four or five available – a so-called Coefficient Of Performance (COP) of four to five (cogeneration, by contrast, only has a COP of 0.8). And those are still early estimates, which Borer expects the system will exceed when finished. “I cannot dream of seven, but [COP] might be as high as six,” he says, grinning. 

To translate those performance figures into reality has required a massive engineering project of drilling, digging, and piping that dwarfs almost every other geothermal project in the state, even rivaling the largest geo-exchange systems nationally. The university will need to drill 2,000 boreholes to adequately heat campus, each measuring either 600 or 850 feet deep depending on the location. The whole process to complete one borehole can take two-and-a-half days, according to a New York Times feature of Princeton’s project. Contractors have already bored 1,000 holes, according to Borer. They now only have another thousand to dig before 2033.

In addition, Princeton must scrape up paths and roads to install another crucial part of geo-exchange infrastructure: 13 miles of hot water pipes to connect TIGER with the campus buildings it will regulate. So far, the University has snaked three miles of pipes through campus, according to Borer. Ten miles to go.


Geo-exchange uses fewer resources than its fossil fuel-based counterparts. At Princeton, the difference is striking. Because it’s a closed loop system, the geo-exchange network doesn’t require any constant inputs nor the sun’s heat, nor electricity from the grid (which will be net-zero by 2035 but currently still burns fossil fuels). 

Compare that with the cogeneration plant, which each year churns through around 110 million gallons of water (nearly half of campus’ total water use) and enough fossil gas to emit 73,000 tons of carbon dioxide. To get it up and running, the new energy system needs 6.6 million gallons of water (according to university drilling permits, 800 gallons of water per borehole) — but no additional inputs; furthermore, it will only emit a relatively small amount of greenhouse gasses.

Less resource consumption is still some resource consumption, however. For instance, although the university aims for geo-exchange to mostly replace cogeneration, fossil fuels will not fully cease to operate on campus. As part of a plan to ramp down the cogeneration plant’s use, Borer intends to replace its fossil gas turbine with diesel generators, which are notoriously polluting. “You might say, that’s the most polluting thing you could get. Why?” Borer asks rhetorically. “Because I never want to run it. I want to run it maybe 100 hours a year.” He reasons that he’ll only resort to diesel in extreme cases – when the grid is seriously stressed, when days of extreme cold strain geo-exchange’s resources, when there’s a storm that causes blackouts. All other times, he’ll stick to geo-exchange. Princeton’s vision, then, is one of fossil fuel phase-down, rather than phase out. “I will argue as much as I can that we need on-site, controllable power generation,” Borer said. “That pretty much means burning stuff.”


Princeton’s geo-exchange project is part of a much larger shift toward a more sustainable future. To reach that future, we could move down several pathways that each rely on different decarbonization methods. The assumptions about how we consume energy may narrow the types of pathways we can take. For instance, most sustainable energy analysts assume that middle- and upper-class individuals will continue to consume the same amount of energy (if not more) as they do now – which is already far higher than in most regions of the world. In this path, few politicians prioritize reducing consumption to more sustainable levels. Instead, they have foregrounded electricity-based heating systems like geo-exchange as the best chance to quickly discard the fossil fuel infrastructure that’s killing us.

As in Princeton, so too in New Jersey. The state has set out ambitious goals for building out geothermal heat pump systems like geo-exchange. It plans to help convert 90% of buildings to electric heating systems like geo-exchange by 2050. Governor Murphy recently set a goal of electrifying 400,000 residential properties and 20,000 commercial spaces by the end of the decade. 

But warning signs that have emerged in Princeton’s geo-exchange project indicate that New Jersey may struggle to support the rapid expansion of geothermal projects in the future. Let’s take a look at permitting first.

Asking for permission to shape the contours and contents of a landscape can be a philosophical, spiritual, or even religious practice. Within the neoliberal state, the process is a more spare affair. To gain permission to poke 2,000 deep holes into the ground and tear up thousands of square feet of land on Princeton’s own private property, all the university had to do was apply for a few drilling and construction permits. 

Relative to cogeneration plants, geo-exchange projects trigger less regulation. That’s partially because, according to Director of Engineering at Princeton University Thomas Nyquist, geo-exchange is a more “benign” system than a fossil fuel plant, meaning they have fewer hurdles to clear. The technology doesn’t require air permits (it doesn’t emit anything when operating), groundwater permits (it doesn’t need much replenishment, beyond the water needed to fill the pipes and storage tanks), or noise permits (the sound pollution from the heat pumps falls below New Jersey thresholds, according to Nyquist).

But large-scale geo-exchange also has fewer regulations because the infrastructure is still rare. “It hasn’t become ubiquitous enough to really get enough visibility to get a lot of regulation,” Grissom said.

Two stout tubes bend into one of the machines in TIGER. Photo by Raphaela Gold ’26.

Two stout tubes bend into one of the machines in TIGER. Photo by Raphaela Gold ’26.

The main permit Princeton had to obtain was a site-wide drilling permit for its drilling activities. They received approval from DEP after some exchanges with the department and local regulators. According to Borer, regulators hadn’t had to deal with such a large project before, which led to some confusion among, for instance, regulators overseeing horizontal pipe construction versus those overseeing vertical well construction.

Moreover, the size of Princeton’s project highlights potential gaps in New Jersey regulation. State law does not require drilling projects to involve third-party oversight to make sure nothing goes wrong. With the smaller projects that make up most geothermal projects in the state, this doesn’t pose a problem. But because Princeton’s drilling has involved multiple drilling companies working in tandem on thousands of boreholes over years, a State Advisory Board of drillers realized in 2019 that some oversight would be important. Seeing that there was “no way” DEP themselves could monitor this drilling, the Board recommended that a certified third-party inspector oversee the project– which Princeton enthusiastically accepted. A deft improvisation, this move also represents a stop-gap measure. Regulators may have to craft a standardized procedure to determine questions like when an overseer might be necessary or what type of accreditation that inspector would require.

Second, while geo-exchange and other ground-based heat pump systems seem to be one of the most attractive sustainable options for large-scale facilities like Princeton, the geothermal industry in New Jersey is too small to quickly install systems at this scale. In Princeton’s case, the university couldn’t find any local drilling companies large enough to meet their requirements. “We had to look all over the country to find people who had the right equipment, and the competence with that equipment, and enough of that equipment,” Borer said.

According to Princeton’s well permit applications, one drilling company, Midwest Geothermal, comes all the way from Michigan. “It wasn’t like you went down to Trenton and hired five contractors,” Grissom said. 

Of course, Princeton had the money to ship this Michigan company to New Jersey. But many other facilities hoping to install geo-exchange don’t. In the meantime, they have no choice but to wait for more local contractors to appear. 

Finally, uncertainty about the cost of geothermal can potentially delay its rollout. Nyquist and Borer hesitate to estimate the cost of Princeton’s geo-exchange system beyond saying that the university  spent “hundreds of millions of dollars.” That’s because they simply don’t know how much money Princeton will be awarded from the Inflation Reduction Act, a massive climate bill that has given geothermal systems a whopping 30 percent tax credit. The U.S. Internal Revenue Service (IRS) has issued broad rules and guidelines outlining what qualifies for the tax credits, and now entities seeking those subsidies have begun to apply for them. But now, the IRS must evaluate whether each applicant’s proposal fits their parameters, a process which Grissom says may take a few years. In the meantime, Borer is left wondering: will the heat exchangers, which transfer the heat from geo-exchange’s pipes into buildings, count for subsidies? Will the far-flung mechanical room or nondescript connecting pipe count? Considerations like these may increase or decrease the overall project cost by as much as 40 percent.

“Even a tax professional can’t guarantee anything yet, because nobody’s gone through the whole process yet,” Grissom said.

Until enough projects have moved through IRS considerations to give a sense of what components of a geothermal system can and cannot be subsidized, no one can be fully certain about how much projects will cost, which may discourage potential geothermal adopters.

These factors all contribute to New Jersey’s current predicament. With regulation suited for much smaller projects, a miniscule large-scale well drilling industry, and unclear federal tax credits, geothermal is off to a sluggish start. Princeton may be leading the way, but only because it has the resources to do so. 

TIGER, the central facility operating the new geo-exchange system, is located at campus’ south-east corner, past Powers Field. Photo by Alex Norbrook ’26.

TIGER, the central facility operating the new geo-exchange system, is located at campus’ south-east corner, past Powers Field. Photo by Alex Norbrook ’26.

On TIGER’s shop floor, surrounded by pipes of water, I see the decarbonization path that Princeton is charting along with the rest of the state. Through technologies like geo-exchange, most facets of everyday life, including energy consumption, can be kept the same with reduced climate impact. Although it will require mass construction on levels no one is prepared for, this path won’t require people to renounce the familiar comforts of industrial society. In some ways, that makes everything easier, because in the ideal scenario, no one will have to give anything up. 

But choosing one path to travel down limits the scope of what we might otherwise do, or what assumptions we might challenge. The current path that involves geo-exchange might not be enough to address the ideological assumptions that undergird the origins of the crisis. Could there be other pathways to a sustainable future that, for instance, think differently about New Jersey’s sky-high energy use? Could we think differently about private land, nuancing its current status as an inanimate resource to be torn up, drilled into, and shaped for human benefit? As I bid my farewells to Borer and walk away from the boxy industrial structure, these questions linger in my mind. 

Are technologies like geo-exchange enough?

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