Where Collisions Are Key

When Hurricane Sandy pummeled New Jersey in 2012, Princeton escaped with far less damage than many other communities: mainly, 50 felled trees, blocked roads, and a loss of power from the local utility. The University managed to power the campus with its cogeneration plant. But instead of using power from its solar-panel field, Princeton shut it down. That might seem paradoxical, but there was an important reason for the decision: Solar power can come and go with the clouds, varying quickly from no power to full power. The variation had the potential to trip Princeton’s generator — and that was not a risk campus energy experts wanted to take. Had there been some way to store solar energy from sunny days for later use — like a giant battery — things might have been different.

A decade ago, these kinds of issues — enormous batteries, judicious use of electricity — were research topics at Princeton, to be sure, but they didn’t have a central home on campus. That changed with the 2008 founding of the Andlinger Center for Energy and the Environment, made possible by a $100 million gift from international business executive Gerhard R. Andlinger ’52. This fall, center researchers are moving into their home: a new building at the corner of Olden Street and Prospect Avenue. The question of how to build a giant battery is exactly the kind of multidisciplinary problem this center was made to tackle — in fact, a group of young faculty members is on the case. Their goal: to someday construct batteries into a building’s very walls. 

The idea started like so many great ones do — over beer. Battery researcher Dan Steingart, who has a joint appointment with the Andlinger Center and the department of mechanical and aerospace engineering, was chatting with fellow Andlinger faculty member and civil and environmental engineer Claire White about her expertise — sustainable concrete. When she mentioned the alkaline chemistry (higher than neutral pH) of a sustainable concrete under investigation in her lab, they came up with an idea. Alkaline batteries — the kind most people use every day — share this high-pH chemistry. Could they get White’s concrete to behave like a battery?

Their research was driven by economics as well as science. People might not think of fossil fuels as batteries, but petroleum products have been storing energy for eons. When petroleum burns, the process of combustion releases the energy held inside its chemical bonds, Steingart says. Oil and gas are cheap and easy to transport, he adds, so to be competitive as part of an electrical-power storage network without any subsidies, “the per-pound cost of a battery has to approach that of dog food.” Fortunately, concrete is about as cheap a material as they come. White and Steingart’s approach was to make a small concrete block with electrodes embedded inside. 

White and Steingart experienced what Andlinger Center founding director Emily Carter calls a “collision.” Princeton, she says, is second to none at putting brilliant people in proximity and encouraging the random encounters that spark something new. If that sounds like the way chemists might speak about atoms, well, that makes sense. Carter is an eminent quantum chemist. In 2007, she read the report of the Intergovernmental Panel on Climate Change, which convinced her that human beings’ energy habits profoundly affect Earth’s climate. It was her epiphany: She decided then and there to reorient her research toward energy. 

The Andlinger Center is meant to be the place where experts “collide” to address big questions: Where will we get energy to supply a growing and modernizing population? How can we use the energy we already have in the most efficient way? And how can we do it while being good stewards to the planet? These problems are too big for science and engineering alone, and so the center includes research in policy, social sciences, and the humanities. For instance, behavioral scientist Sander van der Linden has looked into the kinds of activities that promote lasting changes in energy-consumption habits, while biochemical engineer José Avalos is collaborating with Eric Larson of the center’s Energy Systems Analysis Group to study the economic viability of biofuel production plants. The Andlinger Center’s E-ffiliates Partnership, led by chemist Paul Chirik, catalyzes still more collaborations, with companies that work in the energy and environmental sectors. More than 100 Princeton researchers are examining issues related to climate, energy, and environment.

Carter’s own work illustrates that collaboration. When she turned her focus toward energy, she knew there was someone at Princeton she could learn from: solar-cell pioneer Sigurd Wagner. Carter researched solar-energy science and technology with Wagner during a sabbatical. Before long, she was getting grants to apply her quantum know-how to energy-related projects, such as designing new solar-panel materials, or finding ways to convert the greenhouse-gas carbon dioxide to compounds that could be readily transformed into fuels. She became the Andlinger Center’s first director in 2010. And today, she gets around in an electric car — a Volkswagen e-Golf. 

Long before batteries, firewood was Princeton’s energy-storage system: Burning wood released heat that kept many a Princetonian warm in the winter. The sandstone and brick of Nassau Hall retained fireplace heat and provided a cool interior during spring and summer. 

Modern times demand more of buildings, at Princeton and elsewhere. According to the U.S. Energy Information Administration, buildings account for 41 percent of all energy consumption in the nation. Research connected with the Andlinger Center is aimed at lowering that figure, starting right on campus. Consider the Friend Center for Engineering Education, a short walk from the new Andlinger building and one of Princeton’s most technologically advanced facilities when it was completed in 2001. But that doesn’t mean its energy consumption cannot be improved. Sunlight streams in through its glass windows, providing natural light but also a great deal of heat — a disadvantage in the hotter months. “In the summer it’s always cool inside, but only because there’s air conditioning,” says Denisa Buzatu ’15. “Maybe we can be more efficient than that.”

As a rising junior, Buzatu landed an Andlinger Center internship that got her thinking differently about the Friend Center, and how shade can save energy in buildings like it. The research became the foundation for her senior thesis. Working with Princeton civil and environmental engineer Sigrid Adriaenssens, Buzatu developed a movable, adaptable shade. Think origami that folds not by human hands, but by electrical current. Instead of paper, the surfaces of this “origami” are made of acrylic triangles. Wires connecting the triangles can contract to fold the shade or return to a flat shape. According to Buzatu’s computer simulations, installing such a shade could save about 43 percent of the Friend Center’s heating and cooling costs.

Buzatu’s prototypes are about the size of a catcher’s mitt. Scaling them to a practical size requires adjustments in the wiring and design, so she didn’t reach the point of testing on a real-life building. No matter — she’s been bitten by the energy bug, and hopes to weave sustainable design into her graduate studies at the Yale School of Architecture.

Professor Forrest Meggers in the Thermoheliodome, which kept people comfortable in the heat without air conditioning.

Frank Wojciechowski

High-tech shades may reduce the need for air conditioning, but what if it were possible to cool a space without it? Forrest Meggers wants to show the world it’s possible. Meggers, an assistant professor with joint appointments at the Andlinger Center and the School of Architecture, became interested in engineering because he wanted to build bicycles. True to his teenage passion, he gets around Princeton by bike. 

The venue chosen by Meggers and his collaborators for their A/C-free work was Princeton’s Architectural Laboratory, formerly the site of stables for polo ponies, near Jadwin Gym. There, they built an unenclosed pavilion that keeps people comfortable in the summer heat without cooling the air. It’s called the Thermoheliodome (now disconnected). 

Made from 128 robotically fabricated pieces of white foam, the partial dome pumps chilled water from a cooling tower to stick-shaped surfaces that point into the structure’s interior. Meggers designed the inside of the space with funky geometric shapes — cone-shaped indentations lined with reflective material. These shapes allow the chilled temperatures from the sticks to reach all over the surface of the structure with minimal cooling of the surrounding air. (Air quickly escapes any outdoor space, so cooling it would be a waste of energy.) The structure’s lower surface temperature makes people perceive a cooler temperature when walking inside it. The result? “Even though the air in the pavilion might be 90 degrees, you will think it’s less than 80,” Meggers says.

Today, the University’s energy plant cools, heats, and provides power to many buildings on campus. To fill gaps in demand, Princeton purchases power from local utilities, but it’s striving to reduce its carbon footprint by decreasing reliance on fossil fuels. According to the facilities department, the University is on track to decrease campus greenhouse-gas emissions to 1990 levels by 2020, a goal set in the 2008 University-wide Sustainability Plan. 

One important step toward that goal took place in 2012: the installation of the solar-panel field that was shut down temporarily during Hurricane Sandy. The 27-acre field south of Lake Carnegie and visible from the Dinky boasts 16,528 solar panels. It provided roughly 5.5 percent of campus electricity last year.

Barry Rand *07 has spent quite a bit of his time at the Andlinger Center thinking about that solar field. Rand, who has a joint appointment in the electrical engineering department, works to develop materials that will be more efficient at converting the sun’s rays into electricity (commercial solar panels currently top out at less than 25 percent efficiency). His materials may be years away from reaching the market, but he’s using Princeton’s solar field to think about how to maximize the energy that can be harvested with materials already available. 

Working with Rand, Manali P. Gokhale ’16 compared energy production from the two types of solar panels in Princeton’s field: one kind that tracks the sun each day and moves to maximize energy capture, and another that’s fixed at a tilt of 25 degrees. Gokhale found that sun-tracking panels produced 9 percent more energy over the course of the year. But then she looked at how much energy was being produced for a given area of land. Tracking panels move around, so they need extra space. Per unit of land, the fixed solar panels produced 54 percent more energy than their tracking counterparts. The take-away message, Rand says, is that as solar-cell technology gets cheaper, and the cost of land or roof space becomes more significant — as in urban areas — it may make more sense to install fixed panels. 

The sun isn’t the only energy source Andlinger Center researchers are considering. Affiliated faculty are studying fuel cells, wind power, and fusion, to name a few alternatives. José Avalos, who holds a joint appointment in chemical and biological engineering, is working to make biofuels more sustainably.

Avalos is among the many researchers who are coaxing microbes to make valuable molecules. This work isn’t limited to biofuels; it also applies to making pharmaceuticals and other valuable chemicals in a greener way. He gets the job done by hijacking yeast cells’ mitochondria — a compartment considered the “powerhouse” within a cell. 

For example, yeast naturally makes tiny amounts of isobutanol, a molecule Avalos would like to see powering vehicles someday. Isobutanol is chemically related to ethanol, the alcohol in beer or wine and one of today’s dominant biofuels. Ethanol is made from renewable plant sources, largely corn and sugar cane, but it has disadvantages. It has less energy content than gasoline. It also absorbs water from the air, making it corrosive enough to be incompatible with the country’s fuel-transportation infrastructure if used in appreciable quantities. What’s more, using land that could grow food crops to make ethanol fuel is controversial in some quarters.

Avalos engineered yeast to boost isobutanol production. His mitochondria hack increases isobutanol production by about 260 percent, compared with a 10 percent increase from a more established technique. Because microbes easily can be programmed to make small tweaks to the chemical structure of a fuel, it may be feasible someday to cheaply synthesize super-efficient fuel molecules that have yet to be discovered, using renewable materials. The possibilities are limited only by researchers’ imaginations, Avalos says: “We’re only scratching the surface of what can be done.” 

Back on the concrete-battery project, the researchers decided to charge and deplete the concrete block with the electrodes and see what happened next. Early testing has found that the block retains its integrity when charged and depleted, just as a battery would. Steingart envisions painting solar cells on the outside of the mini battery brick, and Rand — another collaborator — is searching for materials that can do double duty: first converting solar energy to electricity, and then storing the power that’s generated. “The challenge is that the outside of this battery brick will have to do very different things from the inside,” Steingart says. “But if you can get it to work, it wouldn’t even have to be as good as the best battery, or the best solar panel, because it would be way cheaper.” 

There’s some early “proof of concept,” but it’s hard to know how long it might take to make the blocks a viable solution to outages caused by another Hurricane Sandy. The prototype is about the size of an ice cube. Even if it proves scalable, White says there will be regulatory barriers to placing them in buildings: New concretes can’t be used under established building codes. Undeterred, Meggers is on the project as well, using his architectural expertise to think about how to integrate this kind of brick into life-size structures. He quips that he always asks the same question of his collaborators: “When do we get to build a bigger block?”

The likelihood that there will be payoffs from these projects only in the distant future doesn’t faze Andlinger Center director Carter. “You can’t just think short-term. It’s only going to get you so far,” she says. “I take the view that this center will exist for centuries. We’re going to continue to need it.”  

Carmen Drahl *07 is a Washington, D.C.-based writer. She is a regular contributor at Forbes.com.

For the record

Emily Carter, professor of mechanical and aerospace engineering and applied and computational mathematics, researched solar-energy science and technology with Professor Sigurd Wagner during a sabbatical. Details of the sabbatical were described incorrectly in the version of this story published in the Dec. 2, 2015, issue.