Princeton is ‘actually taking the bull by the horns, so to say, and radically transforming the energy infrastructure on campus’

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Princeton is undertaking an ambitious plan to transform its campus by 2046 so it emits no carbon at all. Holes are being dug for a giant geo-exchange system, experiments are well under way, and those behind the scenes are hoping this “living laboratory” produces eco-friendly systems that can be replicated elsewhere. Professor Forrest Meggers has been watching as well as working on these plans, and on the PAWcast he explained how Princeton is going to reach zero-carbon — and how people off campus can make a difference, too. 


Princeton University is positioning itself at the forefront of research that could help to throw the brakes on climate change, from its zero-carbon goals to the way it’s using the campus as a living laboratory. One person with a front row seat to all this is Forrest Meggers, a jointly appointed professor in Princeton’s architecture and engineering schools. He also directs Princeton’s C.H.A.O.S lab — that’s an acronym — which seeks to maximize the efficiency of heating and cooling systems. This month, as we celebrate Earth Day and PAW devotes its April issue to climate change, PAW asked Meggers for a tour through Princeton’s energy systems and a look at what’s coming next. 

OK, so Forrest, thank you so much for coming on the PAWcast. 

Forrest Meggers: Thanks for having me. 

Liz Daugherty: So why don’t we start with you. Can you tell me more about what you do at Princeton? 

FM: So, I have the luxurious pleasure of being between two different places on Princeton’s campus that are both directly engaged in the amazing installations that we see all over campus right now, from new buildings to new energy infrastructure. And those are the School of Architecture and the Andlinger Center for Energy and the Environment. At the School of Architecture, I get to build full-scale prototypes, studying building systems integration. And in the School of Engineering at the Andlinger Center, I have a lab where I get to look at how those subsystems themselves integrate and operate more efficiently. 

And all this plays out in conversation with our wonderful team of facilities that allow me to play a little bit in their infrastructure as much as their risk appetite will allow them. Because running the C.H.A.O.S lab, as I deemed my laboratory, sometimes incites a little bit of nervousness amongst those that are running the real buildings on campus, but we have a really wonderful working relationship and my work around heating and cooling systems really synergizes nicely with the work we’re trying to do decarbonize campus. 

LD: How is Princeton currently handling power and energy? Where does the electricity used on campus come from? And how are buildings heated and cooled? 

FM: So, at present, many would view what we already have on campus as relatively progressive and high performance, from an energy standpoint. Our energy comes, within campus, from a very efficient gas turbine system. So this is an engine that is, in fact, as Ted Borer, the head of the energy plant, will often point out — the same engine that’s in an F-14 fighter jet. And that engine is burning gas and produces electricity. 

But what’s unique about our engine is that unlike many large power plants that are decentralized and far away from cities and people that are using electricity, our plant is sitting right on campus. And so, when our engine makes electricity, it doesn’t convert all of the heat that is produced by burning the gas into electricity. And that waste heat, we capture, and we use it to distribute heat around campus, because on campus, we have what’s called a district heating system. And this is common in many university or large-scale corporate campuses where we distribute heat between all our buildings. And that’s an extremely efficient way to centralize the heating systems of our buildings. 

But in some ways it’s also a bit antiquated as we are still using steam pipes, some of which are 100 years old. Because we have been heating the whole campus since about the turn of the last century by pushing around this hot steam. And so, the plan, currently, is to think about how we can begin to progress to that next generation of district heating system and thinking about what could be even better than our already extremely efficient F-14 fighter engine. Because there are ways that we can potentially make that heat and electricity that don’t involve burning gas at all. Which is something from a climate change perspective is very important in thinking about what the real transitions that are necessary in the future. 

LD: So there’s a plan to try and reach net zero carbon, right. To not burn any fossil fuels, right. By 2046. Why 2046, and how is this going to happen? 

FM: Well, I think we all know why 2046. If this is the Princeton alumni magazine, most people know that the University was founded a very specific year that just happens to be 300 years before that date. So, I love that, actually, because it really points to the fact that a lot of the targets we’re viewing are a little bit arbitrary. But they’re absolutely necessary. And, in fact, the most recent conversation is, “Princeton set the 2046 deadline a little bit before some of our peers” but now, some of our peers have set even more ambitious targets. And now, our conversations with the Office of Sustainability are about how we might move that number up even more. 

But in reality, moving it up just means we all recognize the need to accelerate the pace of decarbonization based on the information that we get from our scientists. Many of our own scientists on Princeton’s campus contribute to what’s called the IPCC Report, the Intergovernmental Panel on Climate Change, which is producing these large-scale reports that synthesize research from thousands of researchers in order to try and condense down what are the largest challenges: How much climate change is happening? What are the things causing and driving that climate change the most, and what are the pathways that we might be able to navigate to do that decarbonization. 

And so, having that information at our fingertips from our own scientists is really critical as we transition to the application and the actual doing part of addressing climate change beyond just the science of characterizing the challenge and its implications for our response. 

LD: So, how is this going to happen? Like, this is going to be actual change, we’re going to be creating and using energy differently on campus. Now what do some places do. I think, all right, buying energy credits is not part of the plan here, right? Like offsetting by planting a tree someplace and saying that offsets your carbon — that’s not the plan. The idea is to actually produce zero carbon. So, how is that going to happen? 

FG: Correct, yeah. It is an ambitious goal to try and, sort of, internalize our reduction of carbon emissions. That’s not to say that there — let’s not pretend that there’s no value in buying clean electricity. And I would recommend to all your listeners to look into ways, very easily, to just ask your energy company about buying renewable energy. Because there is — electrons are not necessarily tied to one specific thing or another. But you can incentivize the production of more clean electrons by purchasing clean electricity. 

But that being said, you have no influence over the pace and the type of energy and engineering innovations that have to take place to decarbonize the grid in that framework. What we’re doing on Princeton’s campus is actually taking the bull by the horns, so to say, and radically transforming the energy infrastructure on campus. 

So, for starters, that steam that I mentioned, the room that you’re sitting in, probably right now listening to it — I hope, if it’s still winter — is less than 70 degrees. Not necessarily that warm. But steam, at 212 degrees is quite a bit warmer than what you actually need to heat most buildings. And so, a super obvious way to make the system much more efficient is to switch to a hot-water distribution system at lower temperatures. And this, obviously, lower temperature means lower heat loss. So this will increase the efficiency of the system by probably a factor of two. So, that will be a huge benefit. 

And just for context, stepping back — you know, I am the C.H.A.O.S professor, cooling and heating is my game — but that being said, there’s a good reason for that. Because heating and cooling is really the major energy drivers on campus. So the vast majority, I believe it’s more than 75 percent or more of our energy use on campus is specifically just for heating and cooling. So things like changing over to hot water is a big deal, but it’s also a really big deal from a construction and disturbance standpoint. 

So, you’ll see that if you come to campus. Right now, there are literally holes in the ground everywhere. Some of which, are wonderful geothermal holes, which we’ll get to momentarily, I’m sure. But the most of them that you see right now and that the students have to navigate around are us tearing out our — I think it’s close to — I want to say either five or 20 miles, I can’t remember — we can get this data and make sure we get the right number in there. But it’s miles of steam pipe under the ground on campus that have to be changed out and switched to hot water. And all that is in the service — this is the big part — all that is in the service of switching over to an electricity-driven, geothermal heat pump heating system. 

So, burning things to make heat makes it easy to make very hot steam, but if we want to be as efficient as possible and use as much renewable energy as possible, we have to transition over to things like ground source heat pumps. And those technologies take heat out of the ground and deliver that into the hot water that then’s going around campus. But, it’s a prerequisite to have switched to hot water in order to capture the even, another doubling of our energy efficiency by switching over to these geothermal electricity-driven heat pumps. 

LD: Tell me more about the geoexchange. What is it? How is it going to be used? How does it work? 

FM: The geoexchange is a network of pipes that are basically the same as if anybody’s ever had to drill a well at your house. Right now, the technology you use to put in the pipe that extracts the heat from the ground is the exact same thing that you would call — or I had growing up in Iowa — would call to my farm to drill a well to get well water. That same drilling technology now can be used to insert a heat exchanger then is just a pipe, usually a closed pipe is what we’re using at Princeton’s campus. Though you can use open pipes that take water out of the ground and put the water back into the ground water and just remove heat from it. Those closed pipes can go in those holes and then they’re able to, both take heat out of the ground in the winter, at a temperature that’s usually 30 or 40 degrees warmer than the outside air temperature. Because remember, that’s what we’re competing against: A heat pump is pulling heat from the outside and putting it in the inside of our buildings. So if we take it directly from the outside air, it has to work a lot harder on cold days, up to two times as hard as what we’re going to have in our geoexchange system because the ground is so much warmer than the air. 

And the inverse is true in the summer. We get to use all that coolness of the ground in the summer to dramatically increase the efficiency with which we can cool our buildings and create chilled water. Which, by the way, I didn’t mention this earlier, but parallel to the heating system, we already have, also, a district cooling system. So there are already pipes in the ground that distribute chilled water throughout campus, and so that infrastructure’s in place. And we’re basically installing the hot water pipes so that we can pump hot and cold water all around campus. 

And the beautiful thing about having such a large campus is that even in the middle of the winter, you might be surprised to know that we still need some cooling energy. And even in the middle of the summer, we still need some heating energy. And the heat pump, usually in your home, will be pumping heat out of the ground, for a geothermal — or out of the air for air-sourced heat pump — taking that into your home. But on campus, we can actually take some of the heat out of our cold water that we need to be cold and put it into our hot water. Which just by the cleverness of that setup allows us to double the efficiency of the system without actually changing the technology at all. It’s just what we would call a wonderful benefit of having a diversity of loads on campus where we need a lot of cooling and heating at the same time for research laboratories and various infrastructure and buildings that we have on campus. 

So overall, the system is going to have a huge impact in reducing energy consumption an associated carbon emissions while also ideally making buildings, hopefully, more comfortable and making people happier on campus, too. 

LD: So tell me a little bit about the living lab idea. Princeton has talked about how it can kind of be a test case for cities and other places. Has that happened yet? Princeton’s, kind of a specific, it’s a university. Have things come out of Princeton that have been used elsewhere to help other places reduce their carbon footprints?

FM: Yeah, certainly. I was just in a meeting with the head of the energy plant, again, Ted Borer, as well as the head of engineering facilities, Tom Nyquist, have both been participating in conferences and meetings around district heating. And everybody wants to come visit the Princeton installation, especially while it’s being installed. So there’s a high level of interest in what we’re doing. And we’re really sort of at the bleeding edge of — I would call it risk taking to put it bluntly. It takes a lot of bravery to completely rip out all of your heating system and put in something that’s relatively novel and not necessarily a common type of installation with our large-scale geoexchange system. 

So I didn’t mention earlier, but there are going to be about 2,000 of these wells all tied together, all piped back into this heat pump plant. And then that has to be redistributed through this new network of hot water pipes. And alongside that, we’re tying in these two thermal storage tanks where we store hot and cold water that basically become the cheapest battery you could ever buy, right? If I wanted a battery that was able to turn off or to power the heat pump that’s heating campus, I would have to spend 10 times as much money to buy an electric battery to power the heat pump, whereas, instead I can just heat up water and put it in this big tank that’s down by Faculty Road. 

And now I have this wonderful day-long battery that I can use for supplying heat. And also, that allows us to more, much more effectively use the solar power on campus. And the fun part about that is that this optimization, the question of how do I heat up this tank, how do I cool down with a hot and a cold tank, when should I cool with a cold tank in the summer? These questions are all wonderful optimization questions that our faculty in ORFE and civil engineering, chemical engineering, that are working on optimization strategies around energy systems. This is where the campus is a lab, can really happen without necessarily having to tinker so much with infrastructure. 

In my research, I’m the faculty member that likes to go actually turn nuts and bolts and try and build test energy systems. But, more broadly, the new energy infrastructure and all the new data points that come with it are going to create this wonderful playground for our faculty members that are interested in energy optimization, trying to align when we use electricity with when the grid actually has a lower carbon intensity. So any electron you pull off the grid, depending on the time of day it’s made, obviously, if it’s daytime, it’s more likely it was made solar power. But there’s no incentives or mechanisms for people to take advantage of that, at present. 

But researchers like Jesse Jenkins in Andlinger Center who looks at grid scale policy questions and Christos Maravelias who looks at the optimization of heating and cooling systems — these colleagues of mine and I have been having these wonderful conversations about how when this new system comes online, there’s going to be this great opportunity to take these datapoints and use them to propose new research to teach students about simple optimization problems as well as do advanced optimization around controls that may actually feed back and hopefully help people like Ted, Ted Borer, again, who runs that plant, think about better control strategies that they might implement to decrease — again, decreasing the carbon intensity of the overall system. 

LD: Have students been working on this with you, undergraduates, graduate students?

FM: Yeah, so, all of my post-docs and grad students have been thrust into various campus-as-a-lab projects in one way or another. In my lab, we build a lot of our own custom sensors that we take, and we do a lot of research around looking at set points and thermal comfort and how there’s a lot of poorly conceived standards and quote, unquote “best practices” that are not really the best at making people comfortable and they’re actually pretty good at wasting a lot of energy. And my students will go around and will work will controls engineers in facilities to try and look at what kind of complaints they’re getting and look at ways in which, many of the complaints, as I’m sure your listeners can attest, are often being too hot in rooms in the middle of winter, which frustrates people, or too cold in buildings in the middle of the summer. And these are, unfortunately, things that are a bit insidious and kind of built into the ways in which our control strategies and our thermostats measure things in our current built environment. 

And so, my students have engaged a lot with what are the sort of the standard practices around comfort. But certainly, there have also been many senior thesis projects around the co-generation plant and some of these simple optimizations that are already going on, on campus. And also looking into sort of the design of some of the infrastructure. Because students are excited — students that are interested in energy, they have definitely a strong interest in looking at things that are related to the actual campus energy infrastructure. And I think there’s a really wonderful opportunity to facilitate that excitement with the current decarbonization plan and geoexchange system. 

And solar — I mean, we’re adding another 15 megawatts of solar to the campus on top of the — we have a five megawatt installation that most people are familiar with. If you ride the Dinky into campus, you see it. But we’re going to be, multiplying that by a factor of three. And then with this new energy infrastructure, ideally we’ll be able to use even a higher fraction of that solar energy being generated directly on campus through our optimized use of a heating and cooling system. 

LD: So, should human behavior, or is human behavior going to be a part of this plan? I’m thinking, put on a sweater in the winter. Is changing the way that people think about their spaces and behave in their spaces going to play a role?

FM: Oh, certainly. We have, right now, a project in collaboration with, there’s a visiting fellow from a behavioral science company called Evidn, that’s at the Andlinger Center right now. But he’s also involved in a project with the Office of Sustainability where they’re looking at a very problematic behavior on campus that most people would think, maybe knee-jerk response, you know, like, remember to turn off the lights, or close your doors, or don’t leave your window open. 

But what people don’t realize is that those things are about a hundred times smaller than one person just leaving their hood open in a chemistry lab. So you take the small subset of hoods — when you do chemistry, the problem is you have to bring fresh air in. Most buildings are constantly recycling a certain amount of the air because it’s much more efficient to not have to heat up cold, outdoor air constantly. So you bring in the right among of fresh air. But in a chemistry building, you can’t recycle whatever dangerous thing might be in some student’s fume hood or some researcher’s fume hood. But the problem is, there’s not really the same culture around, don’t forget to turn off the light when you leave a room as there is — when people are doing research. They’re very focused on the research. 

So, Evidn has had this amazing project where they’ve saved, probably the equivalent of getting all the students, times two, to turn off the lights when they leave their rooms, just by teaching the researchers and creating heads-up displays that are actually showing how much energy they’re wasting if they leave the fume hood open. They just aren’t aware of how energy-consuming these things that are mainly viewed as research devices are. And so that’s been a really interesting, simple behavioral science step. 

So, the interesting thing about behavioral science is it’s very systematic and also quantifying what are the biggest actions people can take. So, we’re going to move forward, though and try expand it. These are very niche things amongst the chemistry fume hoods. And there’s certainly a larger context that can be, I think, addressed around understanding energy behaviors in dorms and especially with the new dorms coming online. I’m currently working with facilities to have a better set of default sensors put into the thermostats. So the students can even have recommendations about, “Hey, you should turn off —” if you open your window, the window has a senor that turns off the heating system. The students don’t necessarily know that. If you just put it in just sort of the standard way, which is just like a — students don’t need to know that this is happening. It’s just more efficient that if they open their window, we turn the cooling system off. But if you turn it into a thing where there’s heads-up display that says, “Hey, it’s really nice out, you should open your window.” These are the kinds of things we’ve been discussing around, sort of, changing behaviors instead of air conditioning your room when it’s 75 degrees out. Just opening your window and getting a little bit more fresh hair. It’s probably healthier, anyway. 

LD: Well, that leads into a question I was going to ask you because I think you’re in a really good position to give some advice on this. For regular people, alumni, anyone else who’s interested, what can regular people do if they’re not on Princeton’s campus, to just live a more sustainable life? 

FM: Well, you can just put on a sweater. (laughs) That’s always a good starting place. And turning down your thermostat is pretty easy. But one thing that people aren’t aware of as well — let me see — well, maybe a way to rethink the thermostat in your house is something that has only recently become possible for consumers. One of my biggest beefs with what people can do in their homes is just how detached we’ve made the consumer from the equipment that goes into your home. And that’s sort of systematically become a part of the way heating and cooling systems are installed in buildings. If your furnace breaks, the furnace guy comes and tells you what you should have, and you may ask for the most efficient one, but nine times out of 10, they’re going to convince you, you want this one because it won’t break. And that’s mainly because they don’t want to install the more complicated versions, and that’s what they have in their truck, and so, the inertia of keeping, doing things the same way we’ve always been doing them, especially in residences is pretty high. 

So I always say, probably about the biggest thing anybody can do is just be more of an advocate for yourself when it comes to making energy decisions around your home. Because a lot of the experts aren’t necessarily there to sell you the most efficient thing. And the internet does have some pretty good resources. I would recommend trying to go to — I mean, the Department of Energy tries to have a very objective and friendly interface to sort of just Google or question, “what is the best heating system I should get?” There’s a wonderful page on heat pumps. Heat pumps are terribly counterintuitive for most people. Because, although they use electricity to heat your house, they’re actually moving heat from one place to another. Unlike that electric space heater you have that’s just burning up electricity directly to make heat. So a heat pump could move up to eight times more heat into your house with one unit of electricity than a space heater ever could. 

Recently I was interviewed by The New York Times when they were doing a story about heat pumps, because most people have the misconception that you can’t use heat pumps where it’s too cold. In this case, obviously, we’re talking about air source heat pumps. But unfortunately, this is as often as the case, the fossil fuels industry’s ability to have very strong lobbying and marketing power has led to the propagation of the continued myth that you can’t have air source heat pumps in cold environments. Which is a problem that was solved more than a decade ago with heat pump technology. 

So if anybody tells you you can’t have an air source heat pump in New Jersey or New York or even Massachusetts, this is a misnomer. The technology, even in northern Minnesota you can run a heat pump, what’s called a cold climate heat pump, is what they’re called. And it’s basically clever ways to avoid frost build up. Because when it’s very cold outside, the heat pump’s going to be colder with a freezing temperature. And so the problem with them used to be that there would be lost of frost build up and that would make them stop working. But there’s been lots of really cool, clever material science things — some even developed at Princeton’s own material science institute — to make the ice not stick to the unit bringing the heat in from outside. So, don’t believe that heat pumps don’t work in cold climates. They do.

I think it’s very useful to be proactive about trying to get the most efficient system, and coming back to the thermostat, just as something anybody can do now, it’s only been about a decade, maybe now that we’ve had these smart Nest thermostats. But if you go back before that decade, there were no aisles in Target or BestBuy or Walmart that sold thermostats. But now there’s entire sections of the electronic parts of department stores that just sell thermostats. And that’s because suddenly someone realized that if we make these things actually consumer friendly, then people will start to advocate and install their own systems. Even though a thermostat has almost a VCR-controller programming level of complexity when you need to plug it into your wall, once you get it plugged in, the new ones are so intelligent, they automatically start to save you energy, just because they will learn a little bit about the habits in your house. And they’ll learn, sort of, the heating curve of your house, and they will slowly start to automate the process of doing setbacks. Because one of the biggest things if you have lots of time on your hands that you could do now is just go program your programmable thermostat. But if you talk to any of the computer science faculty at Princeton that do what’s called, human-computer interaction research, they will quickly tell you that the thermostat is the pariah of all human computer interaction. These devices have quite famously been pointed to numerous times to say, “It takes 135 button presses to get one week of setback — or one week of program temperatures programmed into your old-school programmable thermostat.” But the new ones don’t have that. 

So it’s just a really easy thing, and it’s also something I think that’s demonstrative of the necessity to engage consumers more directly in technology that are significant drivers of the performance of a building. I think we’re too far removed from a lot of that tech. 

LD: That gets through pretty much all of my questions. Was there anything else you’d like to add or mention? 

FM: No, I think I’m super excited about what’s going on campus. The only other plug that I would make, that I always make, is just a personal one, which is for bicycle advocacy and transport safety. We have a wonderful campus for cycling. And I think more people should do it because it’s good for your health and good for the environment. But that’s just me being a cyclist advocate, too. Because I think that’s a great way to get outside. 

And the last — and with that in mind, as far as the built environment goes, the one thing that we didn’t bring up that I’ll leave us to contemplate is we are having a lot of conversations now about the new normal. And I don’t think — I think many people view the pandemic as being something that has distracted us from climate change. Because this crazy thing happened and we have to think about ways to be more safe and recognize when it’s very useful to wear a mask if you’re sick, because it’s a way to prevent disease transmission. There’s all these sort of new normal things around the post-pandemic era. But I think some of those new normal things are really things that go hand in hand with strategies we should be making towards climate change. So a lot of the ways that we run buildings and we sort of enclose them and don’t have operable windows: I think my biggest takeaway from the pandemic is that the biggest way to increase your risk of getting COVID was just to be indoors. And so, thinking about how having more ventilation. Again, just opening windows in the summer, spending more time outside. All these things, I think, are things that will make society better and at the same time, actually, help to decrease our demand for energy and the carbon intensity associated with it. So, that goes with biking, too. 

So that’s kind of my final thought is trying to think of how might take advantage of our, hopefully, slightly more stronger propensity for change in this sort of post-pandemic, new normal moment. 

LD: Well, thank you so much for taking the time to talk to me today. 

FM: Thanks. 

PAWcast is a monthly interview podcast produced by the Princeton Alumni Weekly. If you enjoyed this episode, please subscribe. You can find us on Apple Podcasts, Google Podcasts, Spotify, and Soundcloud. You can read transcripts of every episode on our website, Music for this podcast is licensed from Universal Production Music.