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      in Energy

      MIT makes strides on climate action plan

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      Two recent online events related to MIT’s ambitious new climate action plan highlighted several areas of progress, including uses of the campus as a real-life testbed for climate impact research, the creation of new planning bodies with opportunities for input from all parts of the MIT community, and a variety of moves toward reducing the Institute’s own carbon footprint in ways that may also provide a useful model for others.

      On Monday, MIT’s Office of Sustainability held its seventh annual “Sustainability Connect” event, bringing together students, faculty, staff, and alumni to learn about and share ideas for addressing climate change. This year’s virtual event emphasized the work toward carrying out the climate plan, titled “Fast Forward: MIT’s Climate Action Plan for the Decade,” which was announced in May. An earlier event, the “MIT Climate Tune-in” on Nov. 3, provided an overview of the many areas of MIT’s work to tackle climate change and featured a video message from Maria Zuber, MIT’s vice president for research, who was attending the COP26 international climate meeting in Glasgow, Scotland, as part of an 18-member team from MIT.

      Zuber pointed out some significant progress that was made at the conference, including a broad agreement by over 100 nations to end deforestation by the end of the decade; she also noted that the U.S. and E.U. are leading a global coalition of countries committed to curbing methane emissions by 30 percent from 2020 levels by decade’s end. “It’s easy to be pessimistic,” she said, “but being here in Glasgow, I’m actually cautiously optimistic, seeing the thousands and thousands of people here who are working toward meaningful climate action. And I know that same spirit exists on our own campus also.”

      As for MIT’s own climate plan, Zuber emphasized three points: “We’re committed to action; second of all, we’re committed to moving fast; and third, we’ve organized ourselves better for success.” That organization includes the creation of the MIT Climate Steering Committee, to oversee and coordinate MIT’s strategies on climate change; the Climate Nucleus, to oversee the management and implementation of the new plan; and three working groups that are forming now, to involve all parts of the MIT community.

      The “Fast Forward” plan calls for reducing the campus’s net greenhouse gas emissions to zero by 2026 and eliminating all such emissions, including indirect ones, by 2050. At Monday’s event, Director of Sustainability Julie Newman pointed out that the climate plan includes no less than 14 specific commitments related to the campus itself. These can be grouped into five broad areas, she said: mitigation, resiliency, electric vehicle infrastructure, investment portfolio sustainability, and climate leadership. “Each of these commitments has due dates, and they range from the tactical to the strategic,” she said. “We’re in the midst of activating our internal teams” to address these commitments, she added, noting that there are 30 teams that involve 75 faculty and researcher members, plus up to eight student positions.

      One specific project that is well underway involves preparing a detailed map of the flood risks to the campus as sea levels rise and storm surges increase. While previous attempts to map out the campus flooding risks had treated buildings essentially as uniform blocks, the new project has already mapped out in detail the location, elevation, and condition of every access point — doors, windows, and drains — in every building in the main campus, and now plans to extend the work to the residence buildings and outlying parts of campus. The project’s methods for identifying and quantifying the risks to specific parts of the campus, Newman said, represents “part of our mission for leveraging the campus as a test bed” by creating a map that is “true to the nature of the topography and the infrastructure,” in order to be prepared for the effects of climate change.

      Also speaking at the Sustainability Connect event, Vice President for Campus Services and Stewardship Joe Higgins outlined a variety of measures that are underway to cut the carbon footprint of the campus as much as possible, as quickly as possible. Part of that, he explained, involves using the campus as a testbed for the development of the equivalent of a “smart thermostat” system for campus buildings. While such products exist commercially for homeowners, there is no such system yet for large institutional or commercial buildings.

      There is a team actively developing such a pilot program in some MIT buildings, he said, focusing on some large lab buildings that have especially high energy usage. They are examining the use of artificial intelligence to reduce energy consumption, he noted. By adding systems to monitor energy use, temperatures, occupancy, and so on, and to control heating, lighting and air conditioning systems, Higgins said at least a 3 to 5 percent reduction in energy use can be realized. “It may be well beyond that,” he added. “There’s a huge opportunity here.”

      Higgins also outlined the ongoing plan to convert the existing steam distribution system for campus heating into a hot water system. Though the massive undertaking may take decades to complete, he said that project alone may reduce campus carbon emissions by 10 percent. Other efforts include the installation of an additional 400 kilowatts of rooftop solar installations.

      Jeremy Gregory, executive director of MIT’s climate and sustainability consortium, described efforts to deal with the most far-reaching areas of greenhouse gas emission, the so-called Scope 3 emissions. He explained that Scope 1 is the direct emissions from the campus itself, from buildings and vehicles; Scope 2 includes indirect emissions from the generation of electricity; and Scope 3 is “everything else.” That includes employee travel, buildings that MIT leases from others and to others, and all goods and services, he added, “so it includes a lot of different categories of emissions.” Gregory said his team, including several student fellows, is actively investigating and quantifying these Scope 3 emissions at MIT, along with potential methods of reducing them.

      Professor Noelle Selin, who was recently named as co-chair of the new Climate Nucleus along with Professor Anne White, outlined their plans for the coming year, including the setting up of the three working groups.

      Selin said the nucleus consists of representatives of departments, labs, centers, and institutes that have significant responsibilities under the climate plan. That body will make recommendations to the steering committee, which includes the deans of all five of MIT’s schools and the MIT Schwarzman College of Computing, “about how to amplify MIT’s impact in the climate sphere. We have an implementation role, but we also have an accelerator pedal that can really make MIT’s climate impact more ambitious, and really push the buttons and make sure that the Institute’s commitments are actually borne out in reality.”

      The MIT Climate Tune-In also featured Selin and White, as well as a presentation on MIT’s expanded educational offerings on climate and sustainability, from Sarah Meyers, ESI’s education program manager; students Derek Allmond and Natalie Northrup; and postdoc Peter Godart. Professor Dennis Whyte also spoke about MIT and Commonwealth Fusion Systems’ recent historical advance toward commercial fusion energy. Organizers said that the Climate Tune-In event is the first of what they hope will be many opportunities to hear updates on the wide range of work happening across campus to implement the Fast Forward plan, and to spark conversations within the MIT community. More

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      in Energy

      Radio-frequency wave scattering improves fusion simulations

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      In the quest for fusion energy, understanding how radio-frequency (RF) waves travel (or “propagate”) in the turbulent interior of a fusion furnace is crucial to maintaining an efficient, continuously operating power plant. Transmitted by an antenna in the doughnut-shaped vacuum chamber common to magnetic confinement fusion devices called tokamaks, RF waves heat the plasma fuel and drive its current around the toroidal interior. The efficiency of this process can be affected by how the wave’s trajectory is altered (or “scattered”) by conditions within the chamber.

      Researchers have tried to study these RF processes using computer simulations to match the experimental conditions. A good match would validate the computer model, and raise confidence in using it to explore new physics and design future RF antennas that perform efficiently. While the simulations can accurately calculate how much total current is driven by RF waves, they do a poor job at predicting where exactly in the plasma this current is produced.

      Now, in a paper published in the Journal of Plasma Physics, MIT researchers suggest that the models for RF wave propagation used for these simulations have not properly taken into account the way these waves are scattered as they encounter dense, turbulent filaments present in the edge of the plasma known as the “scrape-off layer” (SOL).

      Bodhi Biswas, a graduate student at the Plasma Science and Fusion Center (PSFC) under the direction of Senior Research Scientist Paul Bonoli, School of Engineering Distinguished Professor of Engineering Anne White, and Principal Research Scientist Abhay Ram, who is the paper’s lead author. Ram compares the scattering that occurs in this situation to a wave of water hitting a lily pad: “The wave crashing with the lily pad will excite a secondary, scattered wave that makes circular ripples traveling outward from the plant. The incoming wave has transferred energy to the scattered wave. Some of this energy is reflected backwards (in relation to the incoming wave), some travels forwards, and some is deflected to the side. The specifics all depend on the particular attributes of the wave, the water, and the lily pad. In our case, the lily pad is the plasma filament.”

      Until now, researchers have not properly taken these filaments and the scattering they provoke into consideration when modeling the turbulence inside a tokamak, leading to an underestimation of wave scattering. Using data from PSFC tokamak Alcator C-Mod, Biswas shows that using the new method of modeling RF-wave scattering from SOL turbulence provides results considerably different from older models, and a much better match to experiments. Notably, the “lower-hybrid” wave spectrum, crucial to driving plasma current in a steady-state tokamak, appears to scatter asymmetrically, an important effect not accounted for in previous models.

      Biswas’s advisor Paul Bonoli is well acquainted with traditional “ray-tracing” models, which evaluate a wave trajectory by dividing it into a series of rays. He has used this model, with its limitations, for decades in his own research to understand plasma behavior. Bonoli says he is pleased that “the research results in Bodhi’s doctoral thesis have refocused attention on the profound effect that edge turbulence can have on the propagation and absorption of radio-frequency power.”

      Although ray-tracing treatments of scattering do not fully capture all the wave physics, a “full-wave” model that does would be prohibitively expensive. To solve the problem economically, Biswas splits his analysis into two parts: (1) using ray tracing to model the trajectory of the wave in the tokamak assuming no turbulence, while (2) modifying this ray-trajectory with the new scattering model that accounts for the turbulent plasma filaments.

      “This scattering model is a full-wave model, but computed over a small region and in a simplified geometry so that it is very quick to do,” says Biswas. “The result is a ray-tracing model that, for the first time, accounts for full-wave scattering physics.”

      Biswas notes that this model bridges the gap between simple scattering models that fail to match experiment and full-wave models that are prohibitively expensive, providing reasonable accuracy at low cost.

      “Our results suggest scattering is an important effect, and that it must be taken into account when designing future RF antennas. The low cost of our scattering model makes this very doable.”

      “This is exciting progress,” says Syun’ichi Shiraiwa, staff research physicist at the Princeton Plasma Physics Laboratory. “I believe that Bodhi’s work provides a clear path to the end of a long tunnel we have been in. His work not only demonstrates that the wave scattering, once accurately accounted for, can explain the experimental results, but also answers a puzzling question: why previous scattering models were incomplete, and their results unsatisfying.”

      Work is now underway to apply this model to more plasmas from Alcator C-Mod and other tokamaks. Biswas believes that this new model will be particularly applicable to high-density tokamak plasmas, for which the standard ray-tracing model has been noticeably inaccurate. He is also excited that the model could be validated by DIII-D National Fusion Facility, a fusion experiment on which the PSFC collaborates.

      “The DIII-D tokamak will soon be capable of launching lower hybrid waves and measuring its electric field in the scrape-off layer. These measurements could provide direct evidence of the asymmetric scattering effect predicted by our model.” More

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      in Security

      Saving seaweed with machine learning

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      Last year, Charlene Xia ’17, SM ’20 found herself at a crossroads. She was finishing up her master’s degree in media arts and sciences from the MIT Media Lab and had just submitted applications to doctoral degree programs. All Xia could do was sit and wait. In the meantime, she narrowed down her career options, regardless of whether she was accepted to any program.

      “I had two thoughts: I’m either going to get a PhD to work on a project that protects our planet, or I’m going to start a restaurant,” recalls Xia.

      Xia poured over her extensive cookbook collection, researching international cuisines as she anxiously awaited word about her graduate school applications. She even looked into the cost of a food truck permit in the Boston area. Just as she started hatching plans to open a plant-based skewer restaurant, Xia received word that she had been accepted into the mechanical engineering graduate program at MIT.

      Shortly after starting her doctoral studies, Xia’s advisor, Professor David Wallace, approached her with an interesting opportunity. MathWorks, a software company known for developing the MATLAB computing platform, had announced a new seed funding program in MIT’s Department of Mechanical Engineering. The program encouraged collaborative research projects focused on the health of the planet.

      “I saw this as a super-fun opportunity to combine my passion for food, my technical expertise in ocean engineering, and my interest in sustainably helping our planet,” says Xia.

      Play video

      From MIT Mechanical Engineering: “Saving Seaweed with Machine Learning”

      Wallace knew Xia would be up to the task of taking an interdisciplinary approach to solve an issue related to the health of the planet. “Charlene is a remarkable student with extraordinary talent and deep thoughtfulness. She is pretty much fearless, embracing challenges in almost any domain with the well-founded belief that, with effort, she will become a master,” says Wallace.

      Alongside Wallace and Associate Professor Stefanie Mueller, Xia proposed a project to predict and prevent the spread of diseases in aquaculture. The team focused on seaweed farms in particular.

      Already popular in East Asian cuisines, seaweed holds tremendous potential as a sustainable food source for the world’s ever-growing population. In addition to its nutritive value, seaweed combats various environmental threats. It helps fight climate change by absorbing excess carbon dioxide in the atmosphere, and can also absorb fertilizer run-off, keeping coasts cleaner.

      As with so much of marine life, seaweed is threatened by the very thing it helps mitigate against: climate change. Climate stressors like warm temperatures or minimal sunlight encourage the growth of harmful bacteria such as ice-ice disease. Within days, entire seaweed farms are decimated by unchecked bacterial growth.

      To solve this problem, Xia turned to the microbiota present in these seaweed farms as a predictive indicator of any threat to the seaweed or livestock. “Our project is to develop a low-cost device that can detect and prevent diseases before they affect seaweed or livestock by monitoring the microbiome of the environment,” says Xia.

      The team pairs old technology with the latest in computing. Using a submersible digital holographic microscope, they take a 2D image. They then use a machine learning system known as a neural network to convert the 2D image into a representation of the microbiome present in the 3D environment.

      “Using a machine learning network, you can take a 2D image and reconstruct it almost in real time to get an idea of what the microbiome looks like in a 3D space,” says Xia.

      The software can be run in a small Raspberry Pi that could be attached to the holographic microscope. To figure out how to communicate these data back to the research team, Xia drew upon her master’s degree research.

      In that work, under the guidance of Professor Allan Adams and Professor Joseph Paradiso in the Media Lab, Xia focused on developing small underwater communication devices that can relay data about the ocean back to researchers. Rather than the usual $4,000, these devices were designed to cost less than $100, helping lower the cost barrier for those interested in uncovering the many mysteries of our oceans. The communication devices can be used to relay data about the ocean environment from the machine learning algorithms.

      By combining these low-cost communication devices along with microscopic images and machine learning, Xia hopes to design a low-cost, real-time monitoring system that can be scaled to cover entire seaweed farms.

      “It’s almost like having the ‘internet of things’ underwater,” adds Xia. “I’m developing this whole underwater camera system alongside the wireless communication I developed that can give me the data while I’m sitting on dry land.”

      Armed with these data about the microbiome, Xia and her team can detect whether or not a disease is about to strike and jeopardize seaweed or livestock before it is too late.

      While Xia still daydreams about opening a restaurant, she hopes the seaweed project will prompt people to rethink how they consider food production in general.

      “We should think about farming and food production in terms of the entire ecosystem,” she says. “My meta-goal for this project would be to get people to think about food production in a more holistic and natural way.” More

    • 113 Shares139 Views

      in Environment

      For campus “porosity hunters,” climate resilience is the goal

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      At MIT, it’s not uncommon to see groups navigating campus with smartphones and measuring devices in hand, using the Institute as a test bed for research. During one week this summer more than a dozen students, researchers, and faculty, plus an altimeter, could be seen doing just that as they traveled across MIT to measure the points of entry into campus buildings — including windows, doors, and vents — known as a building’s porosity.

      Why measure campus building porosity?

      The group was part of the MIT Porosity Hunt, a citizen-science effort that is using the MIT campus as a place to test emerging methodologies, instruments, and data collection processes to better understand the potential impact of a changing climate — and specifically storm scenarios resulting from it — on infrastructure. The hunt is a collaborative effort between the Urban Risk Lab, led by director and associate professor of architecture and urbanism Miho Mazereeuw, and the Office of Sustainability (MITOS), aimed at supporting an MIT that is resilient to the impacts of climate change, including flooding and extreme heat events. Working over three days, members of the hunt catalogued openings in dozens of buildings across campus to better support flood mapping and resiliency planning at MIT.

      For Mazereeuw, the data collection project lies at the nexus of her work with the Urban Risk Lab and as a member of MIT’s Climate Resiliency Committee. While the lab’s mission is to “develop methods, prototypes, and technologies to embed risk reduction and preparedness into the design of cities and regions to increase resilience,” the Climate Resiliency Committee — made up of faculty, staff, and researchers — is focused on assessing, planning, and operationalizing a climate-resilient MIT. The work of both the lab and the committee is embedded in the recently released MIT Climate Resiliency Dashboard, a visualization tool that allows users to understand potential flooding impacts of a number of storm scenarios and drive decision-making.

      While the debut of the tool signaled a big advancement in resiliency planning at MIT, some, including Mazereeuw, saw an opportunity for enhancement. In working with Ken Strzepek, a MITOS Faculty Fellow and research scientist at the MIT Center for Global Change Science who was also an integral part of this work, Mazereeuw says she was surprised to learn that even the most sophisticated flood modeling treats buildings as solid blocks. With all buildings being treated the same, despite varying porosity, the dashboard is limited in some flood scenario analysis. To address this, Mazereeuw and others got to work to fill in that additional layer of data, with the citizen science efforts a key factor of that work. “Understanding the porosity of the building is important to understanding how much water actually goes in the building in these scenarios,” she explains.

      Though surveyors are often used to collect and map this type of information, Mazereeuw wanted to leverage the MIT community in order to collect data quickly while engaging students, faculty, and researchers as resiliency stewards for the campus. “It’s important for projects like this to encourage awareness,” she explains. “Generally, when something fails, we notice it, but otherwise we don’t. With climate change bringing on more uncertainty in the scale and intensity of events, we need everyone to be more aware and help us understand things like vulnerabilities.”

      To do this, MITOS and the Urban Risk Lab reached out to more than a dozen students, who were joined by faculty, staff, and researchers, to map porosity of 31 campus buildings connected by basements. The buildings were chosen based on this connectivity, understanding that water that reaches one basement could potentially flow to another.

      Urban Risk Lab research scientists Aditya Barve and Mayank Ojha aided the group’s efforts by creating a mapping app and chatbot to support consistency in reporting and ease of use. Each team member used the app to find buildings where porosity points needed to be mapped. As teams arrived at the building exteriors, they entered their location in the app, which then triggered the Facebook and LINE-powered chatbot on their phone. There, students were guided through measuring the opening, adjusting for elevation to correlate to the City of Cambridge base datum, and, based on observable features, noting the materials and quality of the opening on a one-through-three scale. Over just three days, the team, which included Mazereeuw herself, mapped 1,030 porosity points that will aid in resiliency planning and preparation on campus in a number of ways.

      “The goal is to understand various heights for flood waters around porous spots on campus,” says Mazereeuw. “But the impact can be different depending on the space. We hope this data can inform safety as well as understanding potential damage to research or disruption to campus operations from future storms.”

      The porosity data collection is complete for this round — future hunts will likely be conducted to confirm and converge data — but one team member’s work continues at the basement level of MIT. Katarina Boukin, a PhD student in civil and environmental engineering and PhD student fellow with MITOS, has been focused on methods of collecting data beneath buildings at MIT to understand how they would be impacted if flood water were to enter. “We have a number of connected basements on campus, and if one of them floods, potentially all of them do,” explains Boukin. “By looking at absolute elevation and porosity, we’re connecting the outside to the inside and tracking how much and where water may flow.” With the added data from the Porosity Hunt, a complete picture of vulnerabilities and resiliency opportunities can be shared.

      Synthesizing much of this data is where Eva Then ’21 comes in. Then was among the students who worked to capture data points over the three days and is now working in ArcGIS — an online mapping software that also powers the Climate Resiliency Dashboard — to process and visualize the data collected. Once completed, the data will be incorporated into the campus flood model to increase the accuracy of projections on the Climate Resiliency Dashboard. “Over the next decades, the model will serve as an adaptive planning tool to make campus safe and resilient amid growing climate risks,” Then says.

      For Mazereeuw, the Porosity Hunt and data collected additionally serve as a study in scalability, providing valuable insight on how similar research efforts inspired by the MIT test bed approach could be undertaken and inform policy beyond MIT. She also hopes it will inspire students to launch their own hunts in the future, becoming resiliency stewards for their campus and dorms. “Going through measuring and documenting turns on and shows a new set of goggles — you see campus and buildings in a slightly different way,” she says, “Having people look carefully and document change is a powerful tool in climate and resiliency planning.” 

      Mazereeuw also notes that recent devastating flooding events across the country, including those resulting from Hurricane Ida, have put a special focus on this work. “The loss of life that occurred in that storm, including those who died as waters flooded their basement homes  underscores the urgency of this type of research, planning, and readiness.” More

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      in Environment

      The language of change

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      Ryan Conti came to MIT hoping to find a way to do good things in the world. Now a junior, his path is pointing toward a career in climate science, and he is preparing by majoring in both math and computer science and by minoring in philosophy.

      Language for catalyzing change

      Philosophy matters to Conti not only because he is interested in ethics — questions of right and wrong — but because he believes the philosophy of language can illuminate how humans communicate, including factors that contribute to miscommunication. “I care a lot about climate change, so I want to do scientific work on it, but I also want to help work on policy — which means conveying arguments well and convincing people so that change can occur,” he says.Conti says a key reason he came to MIT was because the Institute has such a strong School of Humanities, Arts, and Social Sciences (MIT SHASS). “One of the big factors in my choosing MIT is that the humanities departments here are really, really good,” says Conti, who was named a 2021 Burchard Scholar in honor of his excellence in the Institute’s humanistic fields. “I was considering literature, writing, philosophy, linguistics, all of that.”Revitalizing endangered indigenous languages

      Within MIT SHASS, Conti has focused academically on the philosophy of language, and he is also personally pursuing another linguistic passion — the preservation and revitalization of endangered indigenous languages. Raised in Plano, Texas, Conti is a citizen of the Chickasaw Nation, which today has fewer than 50 first-language speakers left.“I’ve been studying the language on my own. It’s something I really care about a lot, the entire endeavor of language revitalization,” says Conti, who credits his maternal grandmother with instilling his appreciation for his heritage. “She would always tell me that I should be proud of it,” he says. “As I got older and understood the history of things, the precarious nature of our language, I got more invested.” Conti says working to revitalize the Chickasaw language “could be one of the most important things I do with my life.”Already, MIT has given him an opportunity — through the MIT Solve initiative — to participate in a website project for speakers of Makah, an endangered indigenous language of the Pacific Northwest. “The thrust at a high level is trying to use AI [artificial intelligence] to develop speech-to-text software for languages in the Wakashan language family,” he says. The project taught him a lot about natural language processing and automatic speech recognition, he adds, although his website design was not chosen for implementation.

      Glacier dynamics, algorithms — and Quizbowl!

      MIT has also given Conti some experience on the front lines of climate change. Through the Undergraduate Research Opportunities Program, he has been working in MIT’s Glacier Dynamics and Remote Sensing Group, developing machine learning algorithms to improve iceberg detection using satellite imagery. After graduation, Conti plans to pursue a PhD in climate science, perhaps continuing to work in glaciology.He also hopes to participate in a Chickasaw program that pairs students with native speakers to become fluent. He says he sees some natural overlap between his two passions. “Issues of indigenous sovereignty and language preservation are inherently linked with climate change, because the effects of climate change fall unequally on poor communities, which are oftentimes indigenous communities,” he says.For the moment, however, those plans still lie at least two years in the future. In the meantime, Conti is having fun serving as vice president of the MIT Quizbowl Team, an academic quiz team that competes across the region and often participate in national tournaments. What are Conti’s competition specialties? Literature and philosophy. 

      Story prepared by MIT SHASS CommunicationsEditor, Designer: Emily Hiestand, Communications DirectorSenior Writer: Kathryn O’Neill, Associate News Manager More

    • 100 Shares189 Views

      in Energy

      Crossing disciplines, adding fresh eyes to nuclear engineering

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      Sometimes patterns repeat in nature. Spirals appear in sunflowers and hurricanes. Branches occur in veins and lightning. Limiao Zhang, a doctoral student in MIT’s Department of Nuclear Science and Engineering, has found another similarity: between street traffic and boiling water, with implications for preventing nuclear meltdowns.

      Growing up in China, Zhang enjoyed watching her father repair things around the house. He couldn’t fulfill his dream of becoming an engineer, instead joining the police force, but Zhang did have that opportunity and studied mechanical engineering at Three Gorges University. Being one of four girls among about 50 boys in the major didn’t discourage her. “My father always told me girls can do anything,” she says. She graduated at the top of her class.

      In college, she and a team of classmates won a national engineering competition. They designed and built a model of a carousel powered by solar, hydroelectric, and pedal power. One judge asked how long the system could operate safely. “I didn’t have a perfect answer,” she recalls. She realized that engineering means designing products that not only function, but are resilient. So for her master’s degree, at Beihang University, she turned to industrial engineering and analyzed the reliability of critical infrastructure, in particular traffic networks.

      “Among all the critical infrastructures, nuclear power plants are quite special,” Zhang says. “Although one can provide very enormous carbon-free energy, once it fails, it can cause catastrophic results.” So she decided to switch fields again and study nuclear engineering. At the time she had no nuclear background, and hadn’t studied in the United States, but “I tried to step out of my comfort zone,” she says. “I just applied and MIT welcomed me.” Her supervisor, Matteo Bucci, and her classmates explained the basics of fission reactions as she adjusted to the new material, language, and environment. She doubted herself — “my friend told me, ‘I saw clouds above your head’” — but she passed her first-year courses and published her first paper soon afterward.

      Much of the work in Bucci’s lab deals with what’s called the boiling crisis. In many applications, such as nuclear plants and powerful computers, water cools things. When a hot surface boils water, bubbles cling to the surface before rising, but if too many form, they merge into a layer of vapor that insulates the surface. The heat has nowhere to go — a boiling crisis.

      Bucci invited Zhang into his lab in part because she saw a connection between traffic and heat transfer. The data plots of both phenomena look surprisingly similar. “The mathematical tools she had developed for the study of traffic jams were a completely different way of looking into our problem” Bucci says, “by using something which is intuitively not connected.”

      One can view bubbles as cars. The more there are, the more they interfere with each other. People studying boiling had focused on the physics of individual bubbles. Zhang instead uses statistical physics to analyze collective patterns of behavior. “She brings a different set of skills, a different set of knowledge, to our research,” says Guanyu Su, a postdoc in the lab. “That’s very refreshing.”

      In her first paper on the boiling crisis, published in Physical Review Letters, Zhang used theory and simulations to identify scale-free behavior in boiling: just as in traffic, the same patterns appear whether zoomed in or out, in terms of space or time. Both small and large bubbles matter. Using this insight, the team found certain physical parameters that could predict a boiling crisis. Zhang’s mathematical tools both explain experimental data and suggest new experiments to try. For a second paper, the team collected more data and found ways to predict the boiling crisis in a wider variety of conditions.

      Zhang’s thesis and third paper, both in progress, propose a universal law for explaining the crisis. “She translated the mechanism into a physical law, like F=ma or E=mc2,” Bucci says. “She came up with an equally simple equation.” Zhang says she’s learned a lot from colleagues in the department who are pioneering new nuclear reactors or other technologies, “but for my own work, I try to get down to the very basics of a phenomenon.”

      Bucci describes Zhang as determined, open-minded, and commendably self-critical. Su says she’s careful, optimistic, and courageous. “If I imagine going from heat transfer to city planning, that would be almost impossible for me,” he says. “She has a strong mind.” Last year, Zhang gave birth to a boy, whom she’s raising on her own as she does her research. (Her husband is stuck in China during the pandemic.) “This, to me,” Bucci says, “is almost superhuman.”

      Zhang will graduate at the end of the year, and has started looking for jobs back in China. She wants to continue in the energy field, though maybe not nuclear. “I will use my interdisciplinary knowledge,” she says. “I hope I can design safer and more efficient and more reliable systems to provide energy for our society.” More

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      in Environment

      Mitigating hazards with vulnerability in mind

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      From tropical storms to landslides, the form and frequency of natural hazards vary widely. But the feelings of vulnerability they can provoke are universal.

      Growing up in hazard-prone cities, Ipek Bensu Manav, a civil and environmental engineering PhD candidate with the MIT Concrete Sustainability Hub (CSHub), noticed that this vulnerability was always at the periphery. Today, she’s studying vulnerability, in both its engineering and social dimensions, with the aim of promoting more hazard-resilient communities.

      Her research at CSHub has taken her across the country to attend impactful conferences and allowed her to engage with prominent experts and decision-makers in the realm of resilience. But more fundamentally, it has also taken her beyond the conventional bounds of engineering, reshaping her understanding of the practice.

      From her time in Miami, Florida, and Istanbul, Turkey, Manav is no stranger to natural hazards. Istanbul, which suffered a devastating earthquake in 1999, is predicted to experience an equally violent tremor in the near future, while Miami ranks among the top cities in the U.S. in terms of natural disaster risk due to its vulnerability to hurricanes.

      “Growing up in Miami, I’d always hear about hurricane season on the news,” recounts Manav, “While in Istanbul there was a constant fear about the next big earthquake. Losing people and [witnessing] those kinds of events instilled in me a desire to tame nature.”

      It was this desire to “push the bounds of what is possible” — and to protect lives in the process — that motivated Manav to study civil engineering at Boğaziçi University. Her studies there affirmed her belief in the formidable power of engineering to “outsmart nature.”

      This, in part, led her to continue her studies at MIT CSHub — a team of interdisciplinary researchers who study how to achieve resilient and sustainable infrastructure. Her role at CSHub has given her the opportunity to study resilience in depth. It has also challenged her understanding of natural disasters — and whether they are “natural” at all.

      “Over the past few decades, some policy choices have increased the risk of experiencing disasters,” explains Manav. “An increasingly popular sentiment among resilience researchers is that natural disasters are not ‘natural,’ but are actually man-made. At CSHub we believe there is an opportunity to do better with the growing knowledge and engineering and policy research.”

      As a part of the CSHub portfolio, Manav’s research looks not just at resilient engineering, but the engineering of resilient communities.

      Her work draws on a metric developed at CSHub known as city texture, which is a measurement of the rectilinearity of a city’s layout. City texture, Manav and her colleagues have found, is a versatile and informative measurement. By capturing a city’s order or disorder, it can predict variations in wind flow — variations currently too computationally intensive for most cities to easily render.  

      Manav has derived this metric for her native South Florida. A city texture analysis she conducted there found that numerous census tracts could experience wind speeds 50 percent greater than currently predicted. Mitigating these wind variations could lead to some $697 million in savings annually.

      Such enormous hazard losses and the growing threat of climate change have presented her with a new understanding of engineering.

      “With resilience and climate change at the forefront of engineering, the focus has shifted,” she explains, “from defying limits and building impressive structures to making structures that adapt to the changing environment around us.”

      Witnessing this shift has reoriented her relationship with engineering. Rather than viewing it as a distinct science, she has begun to place it in its broader social and political context — and to recognize how those social and political dynamics often determine engineering outcomes.

      “When I started grad school, I often felt ‘Oh this is an engineering problem. I can engineer a solution’,” recounts Manav. “But as I’ve read more about resilience, I’ve realized that it’s just as much a concern of politics and policy as it is of engineering.”

      She attributes her awareness of policy to MIT CSHub’s collaboration with the Portland Cement Association and the Ready Mixed Concrete Research & Education Foundation. The commitment of the concrete and cement industries to resilient construction has exposed her to the myriad policies that dictate the resilience of communities.

      “Spending time with our partners made me realize how much of a policy issue [resilience] is,” she explains. “And working with them has provided me with a seat at the table with the people engaged in resilience.”

      Opportunities for engagement have been plentiful. She has attended numerous conferences and met with leaders in the realm of sustainability and resilience, including the International Code Council (ICC), Smart Home America, and Strengthen Alabama Homes.

      Some opportunities have proven particularly fortuitous. When attending a presentation hosted by the ICC and the National Association for the Advancement of Colored People (NAACP) that highlighted people of color working on building codes, Manav felt inspired to reach out to the presenters. Soon after, she found herself collaborating with them on a policy report on resilience in communities of color.

      “For me, it was a shifting point, going from prophesizing about what we could be doing, to observing what is being done. It was a very humbling experience,” she says. “Having worked in this lab made me feel more comfortable stepping outside of my comfort zone and reaching out.”

      Manav credits this growing confidence to her mentorship at CSHub. More than just providing support, CSHub Co-director Randy Kirchain has routinely challenged her and inspired further growth.

      “There have been countless times that I’ve reached out to him because I was feeling unsure of myself or my ideas,” says Manav. “And he’s offered clarity and assurance.”

      Before her first conference, she recalls Kirchain staying in the office well into the evening to help her practice and hone her presentation. He’s also advocated for her on research projects to ensure that her insight is included and that she receives the credit she deserves. But most of all, he’s been a great person to work with.

      “Randy is a lighthearted, funny, and honest person to be around,” recounts Manav. “He builds in me the confidence to dive straight into whatever task I’m tackling.”

      That current task is related to equity. Inspired by her conversations with members of the NAACP, Manav has introduced a new dimension to her research — social vulnerability.

      In contrast to place vulnerability, which captures the geographical susceptibility to hazards, social vulnerability captures the extent to which residents have the resources to respond to and recover from hazard events. Household income could act as a proxy for these resources, and the spread of household income across geographies and demographics can help derive metrics of place and social vulnerability. And these metrics matter.

      “Selecting different metrics favors different people when distributing hazard mitigation and recovery funds,” explains Manav. “If we’re looking at just the dollar value of losses, then wealthy households with more valuable properties disproportionally benefit. But, conversely, if we look at losses as a percentage of income, we’re going to prioritize low-income households that might not necessarily have the resources to recover.”

      Manav has incorporated metrics of social vulnerability into her city texture loss estimations. The resulting approach could predict unmitigated damage, estimate subsequent hazard losses, and measure the disparate impact of those losses on low-income and socially vulnerable communities.

      Her hope is that this streamlined approach could change how funds are disbursed and give communities the tools to solve the entwined challenges of climate change and equity.

      The city texture work Manav has adopted is quite different from the gravity-defying engineering that drew her to the field. But she’s found that it is often more pragmatic and impactful.

      Rather than mastering the elements, she’s learning how to adapt to them and help others do the same. Solutions to climate change, she’s discovered, demand the collaboration of numerous parties — as well as a willingness to confront one’s own vulnerabilities and make the decision to reach out.  More

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      in Energy

      The boiling crisis — and how to avoid it

      by

      It’s rare for a pre-teen to become enamored with thermodynamics, but those consumed by such a passion may consider themselves lucky to end up at a place like MIT. Madhumitha Ravichandran certainly does. A PhD student in Nuclear Science and Engineering (NSE), Ravichandran first encountered the laws of thermodynamics as a middle school student in Chennai, India. “They made complete sense to me,” she says. “While looking at the refrigerator at home, I wondered if I might someday build energy systems that utilized these same principles. That’s how it started, and I’ve sustained that interest ever since.”

      She’s now drawing on her knowledge of thermodynamics in research carried out in the laboratory of NSE Assistant Professor Matteo Bucci, her doctoral supervisor. Ravichandran and Bucci are gaining key insights into the “boiling crisis” — a problem that has long saddled the energy industry.

      Ravichandran was well prepared for this work by the time she arrived at MIT in 2017. As an undergraduate at India’s Sastra University, she pursued research on “two-phase flows,” examining the transitions water undergoes between its liquid and gaseous forms. She continued to study droplet evaporation and related phenomena during an internship in early 2017 in the Bucci Lab. That was an eye-opening experience, Ravichandran explains. “Back at my university in India, only 2 to 3 percent of the mechanical engineering students were women, and there were no women on the faculty. It was the first time I had faced social inequities because of my gender, and I went through some struggles, to say the least.”

      MIT offered a welcome contrast. “The amount of freedom I was given made me extremely happy,” she says. “I was always encouraged to explore my ideas, and I always felt included.” She was doubly happy because, midway through the internship, she learned that she’d been accepted to MIT’s graduate program.

      As a PhD student, her research has followed a similar path. She continues to study boiling and heat transfer, but Bucci gave this work some added urgency. They’re now investigating the aforementioned boiling crisis, which affects nuclear reactors and other kinds of power plants that rely on steam generation to drive turbines. In a light water nuclear reactor, water is heated by fuel rods in which nuclear fission has occurred. Heat removal is most efficient when the water circulating past the rods boils. However, if too many bubbles form on the surface, enveloping the fuel rods in a layer of vapor, heat transfer is greatly reduced. That’s not only diminishes power generation, it can also be dangerous because the fuel rods must be continuously cooled to avoid a dreaded meltdown accident.

      Nuclear plants operate at low power ratings to provide an ample safety margin and thereby prevent such a scenario from occurring. Ravichandran believes these standards may be overly cautious, owing to the fact that people aren’t yet sure of the conditions that bring about the boiling crisis. This hurts the economic viability of nuclear power, she says, at a time when we desperately need carbon-free power sources. But Ravichandran and other researchers in the Bucci Lab are starting to fill some major gaps in our understanding.

      They initially ran experiments to determine how quickly bubbles form when water hits a hot surface, how big the bubbles get, how long they grow, and how the surface temperature changes. “A typical experiment lasted two minutes, but it took more than three weeks to pick out every bubble that formed and track its growth and evolution,” Ravichandran explains.

      To streamline this process, she and Bucci are implementing a machine learning approach, based on neural network technology. Neural networks are good at recognizing patterns, including those associated with bubble nucleation. “These networks are data hungry,” Ravichandran says. “The more data they’re fed, the better they perform.” The networks were trained on experimental results pertaining to bubble formation on different surfaces; the networks were then tested on surfaces for which the NSE researchers had no data and didn’t know what to expect.

      After gaining experimental validation of the output from the machine learning models, the team is now trying to get these models to make reliable predictions as to when the bubble crisis, itself, will occur. The ultimate goal is to have a fully autonomous system that can not only predict the boiling crisis, but also show why it happens and automatically shut down experiments before things go too far and lab equipment starts melting.

      In the meantime, Ravichandran and Bucci have made some important theoretical advances, which they report on in a recently published paper for Applied Physics Letters. There had been a debate in the nuclear engineering community as to whether the boiling crisis is caused by bubbles covering the fuel rod surface or due to bubbles growing on top of each other, extending outward from the surface. Ravichandran and Bucci determined that it is a surface-level phenomenon. In addition, they’ve identified the three main factors that trigger the boiling crisis. First, there’s the number of bubbles that form over a given surface area and, second, the average bubble size. The third factor is the product of the bubble frequency (the number of bubbles forming within a second at a given site) and the time it takes for a bubble to reach its full size.

      Ravichandran is happy to have shed some new light on this issue but acknowledges that there’s still much work to be done. Although her research agenda is ambitious and nearly all consuming, she never forgets where she came from and the sense of isolation she felt while studying engineering as an undergraduate. She has, on her own initiative, been mentoring female engineering students in India, providing both research guidance and career advice.

      “I sometimes feel there was a reason I went through those early hardships,” Ravichandran says. “That’s what made me decide that I want to be an educator.” She’s also grateful for the opportunities that have opened up for her since coming to MIT. A recipient of a 2021-22 MathWorks Engineering Fellowship, she says, “now it feels like the only limits on me are those that I’ve placed on myself.” More