“A Century and a Half Worth of Stuff”: Princeton’s Energy Story in Transition

Ted Borer invites me into his office nestled within the MacMillan Building, a squat and slightly faded brick complex built in the early sixties. Posters and chatchkes adorn his room: schematics of campus with colored lines connecting buildings; banknotes from China, Colombia, Dubai, Germany; a button declaring “I love microgrids;” a union bumper sticker from NJ Local 68 Operating Engineers; a photo of Einstein riding a bicycle. 

Princeton is in the midst of a radical energy transition. All across campus, construction workers assemble the components of a net zero future, building out acres of solar panels, drilling thousands of boreholes in the ground and burying hot water pipelines with the goal of decarbonizing by 2046. For most of its history, Princeton followed national energy trends. Now it is leading them. I met up with Borer to get a walk-through of this transformative change.

“I think a lot of my job, or maybe even my calling,” Borer tells me, “is to explain really complex nerdy stuff in as simple a way as possible, so that the average person who’s not a nerdy engineer is like, ‘oh yeah, that’s pretty obvious.’” Behind him sits a framed poster of a Zeus-like figure with red hair and lightning shooting out of his eyes, holding a sun up and lunging toward the viewer. The poster issues a challenge: “Electrify! Reach Drawdown: Reimagine, Rebuild, Rewild, Restore.”

Gray haired and bespectacled, Borer has spent 39 years in the power industry, working on nuclear, coal, oil and natural gas projects in Pennsylvania before moving to Princeton in 1994. Before he was Energy Plant Director here, Borer contributed to the planning and building of Princeton’s cogeneration plant, which provides both power and heat to campus. The cogeneration plant burns natural gas to turn a turbine that produces electricity and low-pressure steam. The electricity supplies over half of Princeton’s demand, and the steam is sent all throughout campus as heating for Princeton’s buildings.

 Hidden between the West Garage and New College West, Princeton’s energy generation facility sprawls across four structures: the cogeneration building, the chilled water plant, a 2.6 million gallon thermal storage water tank, and a cooling tower stack. Despite the plant’s relative efficiency—up to 80% versus 35% of regular natural gas generation—its principal natural gas turbine is on track to be (mostly) replaced by a far more efficient, and carbon-free, geo-exchange heating and cooling system. 

The cogeneration plant marks my first stop in Princeton’s energy story.

– 

Hanging from the ceiling, running up and down the walls, and connecting to large metal-cased machines, pipes of all sizes and colors snake through the expansive energy facility that Borer ushers me into. The machines—designed to chill water—are all stationary, their moving parts hidden. An ever-present humming noise is the only indication that these pumps and chillers move hundreds of thousands of gallons of water each day. 

Here, chilled water is shunted through Princeton’s buildings to remove heat and cool the campus throughout the year. While this water mostly acts as general air conditioning, when concentrated it serves to chill specialized equipment like electron microscopes and lasers used in campus labs. As we walk past the pumps which thrum quietly, Borer points out their different ages: two painted a cheerful red were installed within the last decade, and two faded silver remained from their installation in the mid-60’s. The chilled water will pick up heat as it rushes through campus, then makes its way back to the energy plant, and finally, ejects that heat through an array of twelve stocky cooling towers. 

In its current configuration, this system cannot avoid waste: the cooling towers, effective at dissipating heat energy captured by the chilled water system, waste all of that captured energy—for that reason, Borer calls the towers “energy throwaway machines.” They dump approximately 123 million kilowatt hours’ worth of useful heat energy into the atmosphere. “In the future, that should make us cry,” he says as we exit the chiller room.

This next space, the energy generation facility, is cavernous, its ceiling hard to perceive above harsh strip lighting. Boxy machines form a maze around me, concealing the true size of the chamber. Unlike the chiller room, this space is dingy, and I feel like I’m underground. An incessant whine permeates the room; my tongue picks up a hint of oil in the humid air. 

Here, we arrive at the beating heart of Princeton’s energy plant: a General Electric LM-1600 “aeroderivative” gas turbine. We stay still for a moment to take in the spectacle before us. Encased in a beige block of metal dulled from decades of use, the engine provides 15 megawatts—million watts—of electricity to campus, enough to meet around half of Princeton’s 27-megawatt peak energy demand. The engine model this turbine derives from is used in the supersonic F/A-18 Hornet fighter jet; the promotional material of its manufacturer, General Electric, asks us to “think of the turbine and others in its family as jet engines afraid of heights.” Princeton’s vertigo-fearing engine is bolted down to the ground, clad in steel and imprisoned in a giant energy facility: it needn’t fret about finding itself at high altitude.

Borer speaks of the turbine with pride. “If you happen to be a Blue Angels pilot, you have two of these strapped to the wings of your airframe, and you can go about Mach two,” he says. “We took a purely military derived technology… and we beat it into a device that we use to provide heating and power for education and research. That’s beating a sword into a plowshare.”

As we walk around the room, Borer points out a tiny porthole that gives a glimpse inside part of the generation system. I peer in, basking in the pale glow of a purple flame. Through the multiple layers of reinforced, protective glass, I am looking into the core of a secondary combustion chamber, the duct burner. Though the turbine shoots out air at a scorching 1385 Fahrenheit, the air does not contain quite enough energy to generate the steam required to heat all of campus. To make up the difference, the duct burner needs to guzzle yet more natural gas (“enough for a town” according to Borer), injecting the fuel into the turbine’s exhaust. This infusion sets off a second reaction which produces the required heat—and the mesmerizing violet inferno.

Like the cooling system, this generator wastes potentially useful energy. Where we are now with generation, no form of fossil fuel combustion is able to avoid this fact. Through combustion, Princeton’s generator converts the energy stored in its natural gas feedstock into heat. The generator can capture some of this heat’s energy by using it to spin a turbine, converting the energy into torque which transfers the energy into a much more usable form: electricity. Approximately 35% of the heat is converted in this way. The leftover heat from combustion can be captured to boil water for steam—but only to an extent, as the boiler only expends about 30-45% of the leftover heat energy. After both of these processes, the cogenerator only uses 80% of the energy it starts with. Even this is exceptional for fossil fuel generations: coal plant efficiency hovers around 33%; conventional natural gas generators up to 35%. But none of these wasteful and highly emissive forms of heat and power production will be enough to meet our decarbonization mandate. 

Soon to be mostly replaced by the geo-exchange system under construction, Princeton’s cogeneration plant is the latest—and the last—iteration of a series of fossil fuel plants which have provided to campus heat and power via combustion for over 130 years. For most of its history, indeed, Princeton followed, rather than led, energy infrastructure practices.

–

Cogeneration is not a new method of energy production. The first commercial power plant in the country, Thomas Edison’s famous Pearl Street Station, used the technology in 1882. Burning coal to power “dynamo machines” (now called generators), it used the heat from that combustion to produce steam for heating nearby houses. In this era, power generators were feeble. Pearl Street Station pioneered a hulking 27-ton generator four times as large as any generator which came before it—nicknamed the “jumbo dynamo” for its power—but the station produced just enough power to illuminate a mere 1200 light bulbs. Yet the Station was a success, and set a precedent for cogeneration across the country.

Princeton soon followed Edison’s lead. In 1889, just seven years after Pearl Street Station opened, Princeton built its own cogeneration plant to bring electricity to campus. Called the “New Dynamo Building,” it was a brick facility with an 80-foot tall chimney that sat next to the extravagant, High Victorian Gothic John Green School of Science (both located where Firestone library now stands). The dynamo building—“just the most badass name for a power plant ever,” as Borer puts it—employed a back-pressure steam turbine attached to a boiler to produce “cogenerated” steam and electricity for campus buildings.

A University Catalogue at the time boasted the Dynamo Building’s accessories: a “sixty horse-power boiler,” a “poly-phase generator,” a Westinghouse alternate generator with “a full set of transformers” (Princeton would not dare furnish its power plant with an incomplete transformer set), among various other peculiarly-named machinery. Arc and incandescent lights lit up spaces in the dim shop floor so that its various machines could be examined by students. 

Both Princeton’s and Edison’s cogeneration plants were what is known as district energy sources. In addition to these local power plants, large industrial sites, such as paper mills or pulp factories, favored on-site cogeneration that district energy provides: any waste heat from electricity generation could be captured and reused in other on-site plant processes. As electricity was haltingly installed in cities and towns throughout America, district cogeneration became a common sight in residential areas and industrial processes. 

The early electricity industry at this time, from the early 1880s to the late 1890s, was dominated by thousands of central electric stations which were, as one energy historian describes, “small in scale, parochial in outlook.” Residential electricity providers hadn’t yet branched out from lightbulbs; they mainly competed with kerosene lamp and gas lighting companies. A 1902 census recorded 3620 central electricity stations, and 50,000 isolated electric plants—plants providing electricity for individual properties like factories, many of which most likely employed cogeneration. Residential power stations could heat surrounding buildings with steam because of their proximity to domestic housing.

Yet, over time, district cogeneration was gradually phased out as electrification swept across the country in the early 20th century. By 1925, electricity adoption increased at a rampant pace—growing four times faster than the population. The commercialization of steam turbines and the alternating current (AC) system led to bigger and bigger central power plants which served larger areas. These large, centralized power stations replaced many district cogeneration systems. Electricity and heat became cheaper to buy and transport from the grid rather than to produce on-site, and even the demand for heat dropped as the heat demand for industrial processes decreased. Between 1902 and 1925, three quarters of the manufacturing industry switched from relying on on-site cogeneration to distant, less efficient, central power plants. 

As Princeton’s campus expanded in the early 20th century, it followed this national trend: the University didn’t expand its electricity production beyond a certain point. Apart from building a few cogenerated steam turbine generators in the early 1900s, Princeton chose to meet most additional electricity demand from new campus activities from the grid. Despite this, and looking ahead, Princeton did install more heating systems. Powered by coal, these heating plants benefited from extensive coal production and transportation infrastructure via rail. The boxy “university gothic” boiler house on 200 Elm Drive, opened in 1923, was resupplied by coal trains on a dedicated line that ran directly adjacent to the building (The building now houses Public Safety). 

The Office of Facilities later retrofitted the coal boilers to run on natural gas in the sixties, increasing reliability (no more risk of late coal train deliveries) and decreasing air pollution on campus. This boiler house, and other campus generators, carried Princeton through the 1970s’ energy crisis, albeit with difficulty. During that time, the University established an Energy Management System to optimize heating and cooling used by campus buildings. 

However, Princeton’s desire for a new district cogeneration plant arose when a change in America’s energy supply took hold in the late 1970s: a glut of natural gas. Natural gas exploration and distribution had previously been regulated by federal policy since 1938 in order to thwart monopolistic power abuses which ran rampant in America’s power history. These regulations protected households, but disincentivized inter-state transport, constraining national supply.

After Congress passed deregulation laws like the Natural Gas Policy Act of 1978, the natural gas industry exploded in size. Further policy changes established market rules which made it easier for natural gas producers to transport the fuel through pipelines and to directly negotiate with consumers like Princeton. FERC’s 1992 Order No. 636 “restructured” natural gas markets towards full deregulation, having a “revolutionary impact on the natural gas industry… [unleashing] unprecedented exploration, pipeline construction, and marketing.” 

Soaring gas extraction and deregulation policies, when added to high electricity prices leftover from the 1970s oil crisis, meant Princeton saw an energy market with low gas prices and high electricity prices. It became cheaper to buy natural gas to fuel a district electricity plant than to buy electricity from the grid. An advantageous “spark spread” like this sends a signal: “it suggests you should build a cogeneration plant,” Borer describes. 

And so, in the Fall of 1996, Princeton did just that.

– 

The national energy environment is changing once more today as the climate crisis intensifies. Natural gas use, which kicked off in the 1980s and expanded further in the 2010s with new fracking technology, has turned out to not be the wonder fuel people thought it could be. Fossil fuel plants, which currently dominate energy production, are the second largest contributor to carbon emissions nationwide. Now, all of them must be phased out as quickly as possible to prevent the worst effects of climate change. National climate policies such as the Inflation Reduction Act have spurred unprecedented investments in renewable energy infrastructure.

As in previous moments of energy transition, Princeton is changing with the national landscape. Yet this time, it is positioning itself ahead of the curve. At the moment, the University hopes to rise to the challenge of deep decarbonization by achieving net-zero by 2046. To do so, it is installing a renewable geo-exchange heating and cooling system powered by new solar farms, to mostly take over from the cogeneration plant. Geo-exchange is on the cutting edge of renewable energy infrastructure: the technology has not been commercialized yet, and is only employed in a few locations across the country.

Geo-exchange is a form of climate control that uses rock as a “thermal piggy bank.” Electric heat pumps pull excess heat out of buildings during the summer through water pipes and stow that heated water deep underground, where it will heat up 50 billion pounds of rock by 15-20 degrees. All summer long, the bedrock will collect heat, and in the winter, the same heat pumps will extract the heat from this warmed rock and distribute it to campus.

Because geo-exchange only transfers heat and cooling, rather than generating them, it is highly efficient—more efficient than our current cogeneration plant by a long shot. Where the cogeneration plant has a maximum coefficient of performance of 0.8, geo-exchange will have one of three to four—up to five times as efficient as Princeton’s current infrastructure. The system will replace the cogeneration plant as campus’ primary heater, and is a critical component of Princeton’s net-zero energy transition.

“This,” Borer says in the cogeneration plant, “is…[the] physical place of transition.” In the chiller room, workers in hard hats huddle around a newly-installed water pump undergoing testing later that day. Borer gestures to another new, yet-to-be-tested device: a heat pump that will replace the current chillers. Rather than withdrawing heat from the chilled water system and dispelling it through cooling towers, this heat pump—encased in a blue ribcage and bolted to glossy orange tubes—will capture the heat and sequester it in the underground boreholes: stored for later, rather than wasted.

“It’s a really, really fundamental shift in the way we deliver heating and cooling to campus,” Borer tells me. “We’ve been doing combustion based heating since the 1700s. We’ve been operating a steam system since the 1860s. We were cogenerating in the 1890s… All of that is combustion based. 

“Now, in this moment, we’re changing from combustion based to electric input, and then we’re trying to have all that [come from] renewable supply. And we’re trying to tighten up buildings in ways that we never have before.”

This shift is drastic, its impact visible all across campus. Construction for the geo-exchange heating and cooling system requires drilling thousands of 850-foot deep bore holes into bedrock all across campus and snaking 13 miles of new, insulated hot water pipes between buildings. Today, this impact can hardly be ignored: makeshift bridges span over sunken cavities awaiting pipelines; screeches, bangs, and earth-shaking pounds of excavation equipment echo between buildings; slender rods plunge into the soil from drilling machines which cover Whitman lawn; severed shafts of thick black pipes, soon to be connected and then submerged, poke out of the earth. While some students find all this construction disruptive, they are playing their part in this epochal transition to a more sustainable future.

“You look around and say, ‘Wow, this looks so chaotic,’” Borer tells me. “The answer is, yeah, [this is] once a century, maybe once every century and a half. That’s what it takes to save the planet. We’re correcting or revising a century and a half worth of stuff.”

– 

In front of a framed 19th century campus schematic displaying the dynamo building, Borer tells me about the people who worked to supply Princeton’s power in that era. “They were providing heat, and they were providing light. And they probably had the exact same conversations about their weekends [around] the lunch table,” he says.

While Princeton has continued to change its energy system to keep up with the country’s evolving energy landscape, the charge to provide heat and power to campus has stayed the same. It will continue to do so for campus energy workers as Princeton installs geo-exchange infrastructure. 

“[These workers] had that on their shoulders for years. And then they pass it to somebody else running it on their shoulder for years. And then they pass it to somebody else. We’re carrying it on our shoulders, and not that long from now, we’ll pass it, and it’ll be on somebody else’s shoulders,” Borer says. “There’s a direct continuity of the work that happened back then, to what we’re doing today and what we’re doing next. To me that is very meaningful, to be a part of that.”