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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 Environment

      J-WAFS announces 2021 Solutions Grants for commercializing water and food technologies

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      The Abdul Latif Jameel Water and Food Systems Lab (J-WAFS) recently announced the 2021 J-WAFS Solutions grant recipients. The J-WAFS Solutions program aims to propel MIT water- and food-related research toward commercialization. Grant recipients receive one year of financial support, as well as mentorship, networking, and guidance from industry experts, to begin their journey into the commercial world — whether that be in the form of bringing innovative products to market or launching cutting-edge startup companies. 

      This year, three projects will receive funding across water, food, and agriculture spaces. The winning projects will advance nascent technologies for off-grid refrigeration, portable water filtration, and dairy waste recycling. Each provides an efficient, accessible solution to the respective challenge being addressed.

      Since the start of the J-WAFS Solutions program in 2015, grants have provided instrumental support in creating a number of key MIT startups that focus on major water and food challenges. A 2015-16 grant helped the team behind Via Separations develop their business plan to massively decarbonize industrial separations processes. Other successful J-WAFS Solutions alumni include researchers who created a low-cost water filter made from tree branches and the team that launched the startup Xibus Systems, which is developing a handheld food safety sensor.

      “New technological advances are being made at MIT every day, and J-WAFS Solutions grants provide critical resources and support for these technologies to make it to market so that they can transform our local and global water and food systems,” says J-WAFS Executive Director Renee Robins. “This year’s grant recipients offer innovative tools that will provide more accessible food storage for smallholder farmers in places like Africa, safer drinking water, and a new approach to recycling food waste,” Robins notes. She adds, “J-WAFS is excited to work with these teams, and we look forward to seeing their impact on the water and food sectors.”

      The J-WAFS Solutions program is implemented in collaboration with Community Jameel, the global philanthropic organization founded by Mohammed Jameel ’78, and is supported by the MIT Venture Mentoring Service and the iCorps New England Regional Innovation Node at MIT.

      Mobile evaporative cooling rooms for vegetable preservation

      Food waste is a persistent problem across food systems supply chains, as 30-50 percent of food produced is lost before it reaches the table. The problem is compounded in areas without access to the refrigeration necessary to store food after it is harvested. Hot and dry climates in particular struggle to preserve food before it reaches consumers. A team led by Daniel Frey, faculty director for research at MIT D-Lab and professor of mechanical engineering, has pioneered a new approach to enable farmers to better preserve their produce and improve access to nutritious food in the community. The team includes Leon Glicksman, professor of building technology and mechanical engineering, and Eric Verploegen, a research engineer in MIT D-Lab.

      Instead of relying on traditional refrigeration with high energy and cost requirements, the team is utilizing forced-air evaporative cooling chambers. Their design, based on retrofitting shipping containers, will provide a lower-cost, better-performing solution enabling farmers to chill their produce without access to power. The research team was previously funded by J-WAFS through two different grants in 2019 to develop the off-grid technology in collaboration with researchers at the University of Nairobi and the Collectives for Integrated Livelihood Initiatives (CInI), Jamshedpur. Now, the cooling rooms are ready for pilot testing, which the MIT team will conduct with rural farmers in Kenya and India. The MIT team will deploy and test the storage chambers through collaborations with two Kenyan social enterprises and a nongovernmental organization in Gujarat, India. 

      Off-grid portable ion concentration polarization desalination unit

      Shrinking aquifers, polluted rivers, and increased drought are making fresh drinking water increasingly scarce, driving the need for improved desalination technologies. The water purifiers market, which was $45 billion in 2019, is expected to grow to $90.1 billion in 2025. However, current products on the market are limited in scope, in that they are designed to treat water that is already relatively low in salinity, and do not account for lead contamination or other technical challenges. A better solution is required to ensure access to clean and safe drinking water in the face of water shortages. 

      A team led by Jongyoon Han, professor of biological engineering and electrical engineering at MIT, has developed a portable desalination unit that utilizes an ion concentration polarization process. The compact and lightweight unit has the ability to remove dissolved and suspended solids from brackish water at a rate of one liter per hour, both in installed and remote field settings. The unit was featured in an award-winning video in the 2021 J-WAFS World Water Day Video Competition: MIT Research for a Water Secure Future. The team plans to develop the next-generation prototype of the desalination unit alongside a mass-production strategy and business model.

      Converting dairy industry waste into food and feed ingredients

      One of the trendiest foods in the last decade, Greek yogurt, has a hidden dark side: acid whey. This low-pH, liquid by-product of yogurt production has been a growing problem for producers, as untreated disposal of the whey can pose environmental risks due to its high organic content and acidic odor.

      With an estimated 3 million tons of acid whey generated in the United States each year, MIT researchers saw an opportunity to turn waste into a valuable resource for our food systems. Led by the Willard Henry Dow Professor in Chemical Engineering, Gregory Stephanopoulos, and Anthony J. Sinskey, professor of microbiology, the researchers are utilizing metabolic engineering to turn acid whey into carotenoids, the yellow and orange organic pigments found naturally in carrots, autumn leaves, and salmon. The team is hoping that these carotenoids can be utilized as food supplements or feed additives to make the most of what otherwise would have been wasted. More

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      in Energy

      The boiling crisis — and how to avoid it

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      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

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      in Environment

      Climate and sustainability classes expand at MIT

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      In fall 2019, a new class, 6.S898/12.S992 (Climate Change Seminar), arrived at MIT. It was, at the time, the only course in the Department of Electrical Engineering and Computer Science (EECS) to tackle the science of climate change. The class covered climate models and simulations alongside atmospheric science, policy, and economics.

      Ron Rivest, MIT Institute Professor of Computer Science, was one of the class’s three instructors, with Alan Edelman of the Computer Science and Artificial Intelligence Laboratory (CSAIL) and John Fernández of the Department of Urban Studies and Planning. “Computer scientists have much to contribute to climate science,” Rivest says. “In particular, the modeling and simulation of climate can benefit from advances in computer science.”

      Rivest is one of many MIT faculty members who have been working in recent years to bring topics in climate, sustainability, and the environment to students in a growing variety of fields. And students have said they want this trend to continue.

      “Sustainability is something that touches all disciplines,” says Megan Xu, a rising senior in biological engineering and advisory chair of the Undergraduate Association Sustainability Committee. “As students who have grown up knowing that climate change is real and witnessed climate disaster after disaster, we know this is a huge problem that needs to be addressed by our generation.”

      Expanding the course catalog

      As education program manager at the MIT Environmental Solutions Initiative, Sarah Meyers has repeatedly had a hand in launching new sustainability classes. She has steered grant money to faculty, brought together instructors, and helped design syllabi — all in the service of giving MIT students the same world-class education in climate and sustainability that they get in science and engineering.

      Her work has given Meyers a bird’s-eye view of MIT’s course offerings in this area. By her count, there are now over 120 undergraduate classes, across 23 academic departments, that teach climate, environment, and sustainability principles.

      “Educating the next generation is the most important way that MIT can have an impact on the world’s environmental challenges,” she says. “MIT students are going to be leaders in their fields, whatever they may be. If they really understand sustainable design practices, if they can balance the needs of all stakeholders to make ethical decisions, then that actually changes the way our world operates and can move humanity towards a more sustainable future.”

      Some sustainability classes are established institutions at MIT. Success stories include 2.00A (Fundamentals of Engineering Design: Explore Space, Sea and Earth), a hands-on engineering class popular with first-year students; and 21W.775 (Writing About Nature and Environmental Issues), which has helped undergraduates fulfill their HASS-H (humanities distribution subject) and CI-H (Communication Intensive subject in the Humanities, Arts, and Social Sciences) graduation requirements for 15 years.

      Expanding this list of classes is an institutional priority. In the recently released Climate Action Plan for the Decade, MIT pledged to recruit at least 20 additional faculty members who will teach climate-related classes.

      “I think it’s easy to find classes if you’re looking for sustainability classes to take,” says Naomi Lutz, a senior in mechanical engineering who helped advise the MIT administration on education measures in the Climate Action Plan. “I usually scroll through the titles of the classes in courses 1, 2, 11, and 12 to see if any are of interest. I also have used the Environment & Sustainability Minor class list to look for sustainability-related classes to take.

      “The coming years are critical for the future of our planet, so it’s important that we all learn about sustainability and think about how to address it,” she adds.

      Working with students’ schedules

      Still, despite all this activity, climate and sustainability are not yet mainstream parts of an MIT education. Last year, a survey of over 800 MIT undergraduates, taken by the Undergraduate Association Sustainability Committee, found that only one in four had ever taken a class related to sustainability. But it doesn’t seem to be from lack of interest in the topic. More than half of those surveyed said that sustainability is a factor in their career planning, and almost 80 percent try to practice sustainability in their daily lives.

      “I’ve often had conversations with students who were surprised to learn there are so many classes available,” says Meyers. “We do need to do a better job communicating about them, and making it as easy as possible to enroll.”

      A recurring challenge is helping students fit sustainability into their plans for graduation, which are often tightly mapped-out.

      “We each only have four years — around 32 to 40 classes — to absorb all that we can from this amazing place,” says Xu. “Many of these classes are mandated to be GIRs [General Institute Requirements] and major requirements. Many students recognize that sustainability is important, but might not have the time to devote an entire class to the topic if it would not count toward their requirements.”

      This was a central focus for the students who were involved in forming education recommendations for the Climate Action Plan. “We propose that more sustainability-related courses or tracks are offered in the most common majors, especially in Course 6 [EECS],” says Lutz. “If students can fulfill major requirements while taking courses that address environmental problems, we believe more students will pursue research and careers related to sustainability.”

      She also recommends that students look into the dozens of climate and sustainability classes that fulfill GIRs. “It’s really easy to take sustainability-related courses that fulfill HASS [Humanities, Arts, and Social Sciences] requirements,” she says. For example, students can meet their HASS-S (social sciences sistribution subject) requirement by taking 21H.185 (Environment and History), or fulfill their HASS-A requirement with CMS.374 (Transmedia Art, Extraction and Environmental Justice).

      Classes with impact

      For those students who do seek out sustainability classes early in their MIT careers, the experience can shape their whole education.

      “My first semester at MIT, I took Environment and History, co-taught by professors Susan Solomon and Harriet Ritvo,” says Xu. “It taught me that there is so much more involved than just science and hard facts to solving problems in sustainability and climate. I learned to look at problems with more of a focus on people, which has informed much of the extracurricular work that I’ve gone on to do at MIT.”

      And the faculty, too, sometimes find that teaching in this area opens new doors for them. Rivest, who taught the climate change seminar in Course 6, is now working to build a simplified climate model with his co-instructor Alan Edelman, their teaching assistant Henri Drake, and Professor John Deutch of the Department of Chemistry, who joined the class as a guest lecturer. “I very much enjoyed meeting new colleagues from all around MIT,” Rivest says. “Teaching a class like this fosters connections between computer scientists and climate scientists.”

      Which is why Meyers will continue helping to get these classes off the ground. “We know students think climate is a huge issue for their futures. We know faculty agree with them,” she says. “Everybody wants this to be part of an MIT education. The next step is to really reach out to students and departments to fill the classrooms. That’s the start of a virtuous cycle where enrollment drives more sustainability instruction in every part of MIT.” More

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      in Environment

      Countering climate change with cool pavements

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      Pavements are an abundant urban surface, covering around 40 percent of American cities. But in addition to carrying traffic, they can also emit heat.

      Due to what’s called the urban heat island effect, densely built, impermeable surfaces like pavements can absorb solar radiation and warm up their surroundings by re-emitting that radiation as heat. This phenomenon poses a serious threat to cities. It increases air temperatures by up as much as 7 degrees Fahrenheit and contributes to health and environmental risks — risks that climate change will magnify.

      In response, researchers at the MIT Concrete Sustainability Hub (MIT CSHub) are studying how a surface that ordinarily heightens urban heat islands can instead lessen their intensity. Their research focuses on “cool pavements,” which reflect more solar radiation and emit less heat than conventional paving surfaces.

      A recent study by a team of current and former MIT CSHub researchers in the journal of Environmental Science and Technology outlines cool pavements and their implementation. The study found that they could lower air temperatures in Boston and Phoenix by up to 1.7 degrees Celsius (3 F) and 2.1 C (3.7 F), respectively. They would also reduce greenhouse gas emissions, cutting total emissions by up to 3 percent in Boston and 6 percent in Phoenix. Achieving these savings, however, requires that cool pavement strategies be selected according to the climate, traffic, and building configurations of each neighborhood.

      Cities like Los Angeles and Phoenix have already conducted sizeable experiments with cool pavements, but the technology is still not widely implemented. The CSHub team hopes their research can guide future cool paving projects to help cities cope with a changing climate.

      Scratching the surface

      It’s well known that darker surfaces get hotter in sunlight than lighter ones. Climate scientists use a metric called “albedo” to help describe this phenomenon.

      “Albedo is a measure of surface reflectivity,” explains Hessam AzariJafari, the paper’s lead author and a postdoc at the MIT CSHub. “Surfaces with low albedo absorb more light and tend to be darker, while high-albedo surfaces are brighter and reflect more light.”

      Albedo is central to cool pavements. Typical paving surfaces, like conventional asphalt, possess a low albedo and absorb more radiation and emit more heat. Cool pavements, however, have brighter materials that reflect more than three times as much radiation and, consequently, re-emit far less heat.

      “We can build cool pavements in many different ways,” says Randolph Kirchain, a researcher in the Materials Science Laboratory and co-director of the Concrete Sustainability Hub. “Brighter materials like concrete and lighter-colored aggregates offer higher albedo, while existing asphalt pavements can be made ‘cool’ through reflective coatings.”

      CSHub researchers considered these several options in a study of Boston and Phoenix. Their analysis considered different outcomes when concrete, reflective asphalt, and reflective concrete replaced conventional asphalt pavements — which make up more than 95 percent of pavements worldwide.

      Situational awareness

      For a comprehensive understanding of the environmental benefits of cool pavements in Boston and Phoenix, researchers had to look beyond just paving materials. That’s because in addition to lowering air temperatures, cool pavements exert direct and indirect impacts on climate change.  

      “The one direct impact is radiative forcing,” notes AzariJafari. “By reflecting radiation back into the atmosphere, cool pavements exert a radiative forcing, meaning that they change the Earth’s energy balance by sending more energy out of the atmosphere — similar to the polar ice caps.”

      Cool pavements also exert complex, indirect climate change impacts by altering energy use in adjacent buildings.

      “On the one hand, by lowering temperatures, cool pavements can reduce some need for AC [air conditioning] in the summer while increasing heating demand in the winter,” says AzariJafari. “Conversely, by reflecting light — called incident radiation — onto nearby buildings, cool pavements can warm structures up, which can increase AC usage in the summer and lower heating demand in the winter.”

      What’s more, albedo effects are only a portion of the overall life cycle impacts of a cool pavement. In fact, impacts from construction and materials extraction (referred to together as embodied impacts) and the use of the pavement both dominate the life cycle. The primary use phase impact of a pavement — apart from albedo effects  — is excess fuel consumption: Pavements with smooth surfaces and stiff structures cause less excess fuel consumption in the vehicles that drive on them.

      Assessing the climate-change impacts of cool pavements, then, is an intricate process — one involving many trade-offs. In their study, the researchers sought to analyze and measure them.

      A full reflection

      To determine the ideal implementation of cool pavements in Boston and Phoenix, researchers investigated the life cycle impacts of shifting from conventional asphalt pavements to three cool pavement options: reflective asphalt, concrete, and reflective concrete.

      To do this, they used coupled physical simulations to model buildings in thousands of hypothetical neighborhoods. Using this data, they then trained a neural network model to predict impacts based on building and neighborhood characteristics. With this tool in place, it was possible to estimate the impact of cool pavements for each of the thousands of roads and hundreds of thousands of buildings in Boston and Phoenix.

      In addition to albedo effects, they also looked at the embodied impacts for all pavement types and the effect of pavement type on vehicle excess fuel consumption due to surface qualities, stiffness, and deterioration rate.

      After assessing the life cycle impacts of each cool pavement type, the researchers calculated which material — conventional asphalt, reflective asphalt, concrete, and reflective concrete — benefited each neighborhood most. They found that while cool pavements were advantageous in Boston and Phoenix overall, the ideal materials varied greatly within and between both cities.

      “One benefit that was universal across neighborhood type and paving material, was the impact of radiative forcing,” notes AzariJafari. “This was particularly the case in areas with shorter, less-dense buildings, where the effect was most pronounced.”

      Unlike radiative forcing, however, changes to building energy demand differed by location. In Boston, cool pavements reduced energy demand as often as they increased it across all neighborhoods. In Phoenix, cool pavements had a negative impact on energy demand in most census tracts due to incident radiation. When factoring in radiative forcing, though, cool pavements ultimately had a net benefit.

      Only after considering embodied emissions and impacts on fuel consumption did the ideal pavement type manifest for each neighborhood. Once factoring in uncertainty over the life cycle, researchers found that reflective concrete pavements had the best results, proving optimal in 53 percent and 73 percent of the neighborhoods in Boston and Phoenix, respectively.

      Once again, uncertainties and variations were identified. In Boston, replacing conventional asphalt pavements with a cool option was always preferred, while in Phoenix concrete pavements — reflective or not — had better outcomes due to rigidity at high temperatures that minimized vehicle fuel consumption. And despite the dominance of concrete in Phoenix, in 17 percent of its neighborhoods all reflective paving options proved more or less as effective, while in 1 percent of cases, conventional pavements were actually superior.

      “Though the climate change impacts we studied have proven numerous and often at odds with each other, our conclusions are unambiguous: Cool pavements could offer immense climate change mitigation benefits for both cities,” says Kirchain.

      The improvements to air temperatures would be noticeable: the team found that cool pavements would lower peak summer air temperatures in Boston by 1.7 C (3 F) and in Phoenix by 2.1 C (3.7 F). The carbon dioxide emissions reductions would likewise be impressive. Boston would decrease its carbon dioxide emissions by as much as 3 percent over 50 years while reductions in Phoenix would reach 6 percent over the same period.

      This analysis is one of the most comprehensive studies of cool pavements to date — but there’s more to investigate. Just as with pavements, it’s also possible to adjust building albedo, which may result in changes to building energy demand. Intensive grid decarbonization and the introduction of low-carbon concrete mixtures may also alter the emissions generated by cool pavements.

      There’s still lots of ground to cover for the CSHub team. But by studying cool pavements, they’ve elevated a brilliant climate change solution and opened avenues for further research and future mitigation.

      The MIT Concrete Sustainability Hub is a team of researchers from several departments across MIT working on concrete and infrastructure science, engineering, and economics. Its research is supported by the Portland Cement Association and the Ready Mixed Concrete Research and Education Foundation. More

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      in Energy

      A peculiar state of matter in layers of semiconductors

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      Scientists around the world are developing new hardware for quantum computers, a new type of device that could accelerate drug design, financial modeling, and weather prediction. These computers rely on qubits, bits of matter that can represent some combination of 1 and 0 simultaneously. The problem is that qubits are fickle, degrading into regular bits when interactions with surrounding matter interfere. But new research at MIT suggests a way to protect their states, using a phenomenon called many-body localization (MBL).

      MBL is a peculiar phase of matter, proposed decades ago, that is unlike solid or liquid. Typically, matter comes to thermal equilibrium with its environment. That’s why soup cools and ice cubes melt. But in MBL, an object consisting of many strongly interacting bodies, such as atoms, never reaches such equilibrium. Heat, like sound, consists of collective atomic vibrations and can travel in waves; an object always has such heat waves internally. But when there’s enough disorder and enough interaction in the way its atoms are arranged, the waves can become trapped, thus preventing the object from reaching equilibrium.

      MBL had been demonstrated in “optical lattices,” arrangements of atoms at very cold temperatures held in place using lasers. But such setups are impractical. MBL had also arguably been shown in solid systems, but only with very slow temporal dynamics, in which the phase’s existence is hard to prove because equilibrium might be reached if researchers could wait long enough. The MIT research found a signatures of MBL in a “solid-state” system — one made of semiconductors — that would otherwise have reached equilibrium in the time it was watched.

      “It could open a new chapter in the study of quantum dynamics,” says Rahul Nandkishore, a physicist at the University of Colorado at Boulder, who was not involved in the work.

      Mingda Li, the Norman C Rasmussen Assistant Professor Nuclear Science and Engineering at MIT, led the new study, published in a recent issue of Nano Letters. The researchers built a system containing alternating semiconductor layers, creating a microscopic lasagna — aluminum arsenide, followed by gallium arsenide, and so on, for 600 layers, each 3 nanometers (millionths of a millimeter) thick. Between the layers they dispersed “nanodots,” 2-nanometer particles of erbium arsenide, to create disorder. The lasagna, or “superlattice,” came in three recipes: one with no nanodots, one in which nanodots covered 8 percent of each layer’s area, and one in which they covered 25 percent.

      According to Li, the team used layers of material, instead of a bulk material, to simplify the system so dissipation of heat across the planes was essentially one-dimensional. And they used nanodots, instead of mere chemical impurities, to crank up the disorder.

      To measure whether these disordered systems are still staying in equilibrium, the researchers measured them with X-rays. Using the Advanced Photon Source at Argonne National Lab, they shot beams of radiation at an energy of more than 20,000 electron volts, and to resolve the energy difference between the incoming X-ray and after its reflection off the sample’s surface, with an energy resolution less than one one-thousandth of an electron volt. To avoid penetrating the superlattice and hitting the underlying substrate, they shot it at an angle of just half a degree from parallel.

      Just as light can be measured as waves or particles, so too can heat. The collective atomic vibration for heat in the form of a heat-carrying unit is called a phonon. X-rays interact with these phonons, and by measuring how X-rays reflect off the sample, the experimenters can determine if it is in equilibrium.

      The researchers found that when the superlattice was cold — 30 kelvin, about -400 degrees Fahrenheit — and it contained nanodots, its phonons at certain frequencies remained were not in equilibrium.

      More work remains to prove conclusively that MBL has been achieved, but “this new quantum phase can open up a whole new platform to explore quantum phenomena,” Li says, “with many potential applications, from thermal storage to quantum computing.”

      To create qubits, some quantum computers employ specks of matter called quantum dots. Li says quantum dots similar to Li’s nanodots could act as qubits. Magnets could read or write their quantum states, while the many-body localization would keep them insulated from heat and other environmental factors.

      In terms of thermal storage, such a superlattice might switch in and out of an MBL phase by magnetically controlling the nanodots. It could insulate computer parts from heat at one moment, then allow parts to disperse heat when it won’t cause damage. Or it could allow heat to build up and be harnessed later for generating electricity.

      Conveniently, superlattices with nanodots can be constructed using traditional techniques for fabricating semiconductors, alongside other elements of computer chips. According to Li, “It’s a much larger design space than with chemical doping, and there are numerous applications.”

      “I am excited to see that signatures of MBL can now also be found in real material systems,” says Immanuel Bloch, scientific director at the Max-Planck-Institute of Quantum Optics, of the new work. “I believe this will help us to better understand the conditions under which MBL can be observed in different quantum many-body systems and how possible coupling to the environment affects the stability of the system. These are fundamental and important questions and the MIT experiment is an important step helping us to answer them.”

      Funding was provided by the U.S. Department of Energy’s Basic Energy Sciences program’s Neutron Scattering Program. More

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      in Energy

      Energy storage from a chemistry perspective

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      The transition toward a more sustainable, environmentally sound electrical grid has driven an upsurge in renewables like solar and wind. But something as simple as cloud cover can cause grid instability, and wind power is inherently unpredictable. This intermittent nature of renewables has invigorated the competitive landscape for energy storage companies looking to enhance power system flexibility while enabling the integration of renewables.

      “Impact is what drives PolyJoule more than anything else,” says CEO Eli Paster. “We see impact from a renewable integration standpoint, from a curtailment standpoint, and also from the standpoint of transitioning from a centralized to a decentralized model of energy-power delivery.”

      PolyJoule is a Billerica, Massachusetts-based startup that’s looking to reinvent energy storage from a chemistry perspective. Co-founders Ian Hunter of MIT’s Department of Mechanical Engineering and Tim Swager of the Department of Chemistry are longstanding MIT professors considered luminaries in their respective fields. Meanwhile, the core team is a small but highly skilled collection of chemists, manufacturing specialists, supply chain optimizers, and entrepreneurs, many of whom have called MIT home at one point or another.

      “The ideas that we work on in the lab, you’ll see turned into products three to four years from now, and they will still be innovative and well ahead of the curve when they get to market,” Paster says. “But the concepts come from the foresight of thinking five to 10 years in advance. That’s what we have in our back pocket, thanks to great minds like Ian and Tim.”

      PolyJoule takes a systems-level approach married to high-throughput, analytical electrochemistry that has allowed the company to pinpoint a chemical cell design based on 10,000 trials. The result is a battery that is low-cost, safe, and has a long lifetime. It’s capable of responding to base loads and peak loads in microseconds, allowing the same battery to participate in multiple power markets and deployment use cases.

      In the energy storage sphere, interesting technologies abound, but workable solutions are few and far between. But Paster says PolyJoule has managed to bridge the gap between the lab and the real world by taking industry concerns into account from the beginning. “We’ve taken a slightly contrarian view to all of the other energy storage companies that have come before us that have said, ‘If we build it, they will come.’ Instead, we’ve gone directly to the customer and asked, ‘If you could have a better battery storage platform, what would it look like?’”

      With commercial input feeding into the thought processes behind their technological and commercial deployment, PolyJoule says they’ve designed a battery that is less expensive to make, less expensive to operate, safer, and easier to deploy.

      Traditionally, lithium-ion batteries have been the go-to energy storage solution. But lithium has its drawbacks, including cost, safety issues, and detrimental effects on the environment. But PolyJoule isn’t interested in lithium — or metals of any kind, in fact. “We start with the periodic table of organic elements,” says Paster, “and from there, we derive what works at economies of scale, what is easy to converge and convert chemically.”

      Having an inherently safer chemistry allows PolyJoule to save on system integration costs, among other things. PolyJoule batteries don’t contain flammable solvents, which means no added expenses related to fire mitigation. Safer chemistry also means ease of storage, and PolyJoule batteries are currently undergoing global safety certification (UL approval) to be allowed indoors and on airplanes. Finally, with high power built into the chemistry, PolyJoule’s cells can be charged and discharged to extremes, without the need for heating or cooling systems.

      “From raw material to product delivery, we examine each step in the value chain with an eye towards reducing costs,” says Paster. It all starts with designing the chemistry around earth-abundant elements, which allows the small startup to compete with larger suppliers, even at smaller scales. Consider the fact that PolyJoule’s differentiating material cost is less than $1 per kilogram, whereas lithium carbonate sells for $20 per kilogram.

      On the manufacturing side, Paster explains that PolyJoule cuts costs by making their cells in old paper mills and warehouses, employing off-the-shelf equipment previously used for tissue paper or newspaper printing. “We use equipment that has been around for decades because we don’t want to create a cutting-edge technology that requires cutting-edge manufacturing,” he says. “We want to create a cutting-edge technology that can be deployed in industrialized nations and in other nations that can benefit the most from energy storage.”

      PolyJoule’s first customer is an industrial distributed energy consumer with baseline energy consumption that increases by a factor of 10 when the heavy machinery kicks on twice a day. In the early morning and late afternoon, it consumes about 50 kilowatts for 20 minutes to an hour, compared to a baseline rate of 5  kilowatts. It’s an application model that is translatable to a variety of industries. Think wastewater treatment, food processing, and server farms — anything with a fluctuation in power consumption over a 24-hour period.

      By the end of the year, PolyJoule will have delivered its first 10 kilowatt-hour system, exiting stealth mode and adding commercial viability to demonstrated technological superiority. “What we’re seeing, now is massive amounts of energy storage being added to renewables and grid-edge applications,” says Paster. “We anticipated that by 12-18 months, and now we’re ramping up to catch up with some of the bigger players.” More

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      in Energy

      Designing better batteries for electric vehicles

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      The urgent need to cut carbon emissions is prompting a rapid move toward electrified mobility and expanded deployment of solar and wind on the electric grid. If those trends escalate as expected, the need for better methods of storing electrical energy will intensify.

      “We need all the strategies we can get to address the threat of climate change,” says Elsa Olivetti PhD ’07, the Esther and Harold E. Edgerton Associate Professor in Materials Science and Engineering. “Obviously, developing technologies for grid-based storage at a large scale is critical. But for mobile applications — in particular, transportation — much research is focusing on adapting today’s lithium-ion battery to make versions that are safer, smaller, and can store more energy for their size and weight.”

      Traditional lithium-ion batteries continue to improve, but they have limitations that persist, in part because of their structure. A lithium-ion battery consists of two electrodes — one positive and one negative — sandwiched around an organic (carbon-containing) liquid. As the battery is charged and discharged, electrically charged particles (or ions) of lithium pass from one electrode to the other through the liquid electrolyte.

      One problem with that design is that at certain voltages and temperatures, the liquid electrolyte can become volatile and catch fire. “Batteries are generally safe under normal usage, but the risk is still there,” says Kevin Huang PhD ’15, a research scientist in Olivetti’s group.

      Another problem is that lithium-ion batteries are not well-suited for use in vehicles. Large, heavy battery packs take up space and increase a vehicle’s overall weight, reducing fuel efficiency. But it’s proving difficult to make today’s lithium-ion batteries smaller and lighter while maintaining their energy density — that is, the amount of energy they store per gram of weight.

      To solve those problems, researchers are changing key features of the lithium-ion battery to make an all-solid, or “solid-state,” version. They replace the liquid electrolyte in the middle with a thin, solid electrolyte that’s stable at a wide range of voltages and temperatures. With that solid electrolyte, they use a high-capacity positive electrode and a high-capacity, lithium metal negative electrode that’s far thinner than the usual layer of porous carbon. Those changes make it possible to shrink the overall battery considerably while maintaining its energy-storage capacity, thereby achieving a higher energy density.

      “Those features — enhanced safety and greater energy density — are probably the two most-often-touted advantages of a potential solid-state battery,” says Huang. He then quickly clarifies that “all of these things are prospective, hoped-for, and not necessarily realized.” Nevertheless, the possibility has many researchers scrambling to find materials and designs that can deliver on that promise.

      Thinking beyond the lab

      Researchers have come up with many intriguing options that look promising — in the lab. But Olivetti and Huang believe that additional practical considerations may be important, given the urgency of the climate change challenge. “There are always metrics that we researchers use in the lab to evaluate possible materials and processes,” says Olivetti. Examples might include energy-storage capacity and charge/discharge rate. When performing basic research — which she deems both necessary and important — those metrics are appropriate. “But if the aim is implementation, we suggest adding a few metrics that specifically address the potential for rapid scaling,” she says.

      Based on industry’s experience with current lithium-ion batteries, the MIT researchers and their colleague Gerbrand Ceder, the Daniel M. Tellep Distinguished Professor of Engineering at the University of California at Berkeley, suggest three broad questions that can help identify potential constraints on future scale-up as a result of materials selection. First, with this battery design, could materials availability, supply chains, or price volatility become a problem as production scales up? (Note that the environmental and other concerns raised by expanded mining are outside the scope of this study.) Second, will fabricating batteries from these materials involve difficult manufacturing steps during which parts are likely to fail? And third, do manufacturing measures needed to ensure a high-performance product based on these materials ultimately lower or raise the cost of the batteries produced?

      To demonstrate their approach, Olivetti, Ceder, and Huang examined some of the electrolyte chemistries and battery structures now being investigated by researchers. To select their examples, they turned to previous work in which they and their collaborators used text- and data-mining techniques to gather information on materials and processing details reported in the literature. From that database, they selected a few frequently reported options that represent a range of possibilities.

      Materials and availability

      In the world of solid inorganic electrolytes, there are two main classes of materials — the oxides, which contain oxygen, and the sulfides, which contain sulfur. Olivetti, Ceder, and Huang focused on one promising electrolyte option in each class and examined key elements of concern for each of them.

      The sulfide they considered was LGPS, which combines lithium, germanium, phosphorus, and sulfur. Based on availability considerations, they focused on the germanium, an element that raises concerns in part because it’s not generally mined on its own. Instead, it’s a byproduct produced during the mining of coal and zinc.

      To investigate its availability, the researchers looked at how much germanium was produced annually in the past six decades during coal and zinc mining and then at how much could have been produced. The outcome suggested that 100 times more germanium could have been produced, even in recent years. Given that supply potential, the availability of germanium is not likely to constrain the scale-up of a solid-state battery based on an LGPS electrolyte.

      The situation looked less promising with the researchers’ selected oxide, LLZO, which consists of lithium, lanthanum, zirconium, and oxygen. Extraction and processing of lanthanum are largely concentrated in China, and there’s limited data available, so the researchers didn’t try to analyze its availability. The other three elements are abundantly available. However, in practice, a small quantity of another element — called a dopant — must be added to make LLZO easy to process. So the team focused on tantalum, the most frequently used dopant, as the main element of concern for LLZO.

      Tantalum is produced as a byproduct of tin and niobium mining. Historical data show that the amount of tantalum produced during tin and niobium mining was much closer to the potential maximum than was the case with germanium. So the availability of tantalum is more of a concern for the possible scale-up of an LLZO-based battery.

      But knowing the availability of an element in the ground doesn’t address the steps required to get it to a manufacturer. So the researchers investigated a follow-on question concerning the supply chains for critical elements — mining, processing, refining, shipping, and so on. Assuming that abundant supplies are available, can the supply chains that deliver those materials expand quickly enough to meet the growing demand for batteries?

      In sample analyses, they looked at how much supply chains for germanium and tantalum would need to grow year to year to provide batteries for a projected fleet of electric vehicles in 2030. As an example, an electric vehicle fleet often cited as a goal for 2030 would require production of enough batteries to deliver a total of 100 gigawatt hours of energy. To meet that goal using just LGPS batteries, the supply chain for germanium would need to grow by 50 percent from year to year — a stretch, since the maximum growth rate in the past has been about 7 percent. Using just LLZO batteries, the supply chain for tantalum would need to grow by about 30 percent — a growth rate well above the historical high of about 10 percent.

      Those examples demonstrate the importance of considering both materials availability and supply chains when evaluating different solid electrolytes for their scale-up potential. “Even when the quantity of a material available isn’t a concern, as is the case with germanium, scaling all the steps in the supply chain to match the future production of electric vehicles may require a growth rate that’s literally unprecedented,” says Huang.

      Materials and processing

      In assessing the potential for scale-up of a battery design, another factor to consider is the difficulty of the manufacturing process and how it may impact cost. Fabricating a solid-state battery inevitably involves many steps, and a failure at any step raises the cost of each battery successfully produced. As Huang explains, “You’re not shipping those failed batteries; you’re throwing them away. But you’ve still spent money on the materials and time and processing.”

      As a proxy for manufacturing difficulty, Olivetti, Ceder, and Huang explored the impact of failure rate on overall cost for selected solid-state battery designs in their database. In one example, they focused on the oxide LLZO. LLZO is extremely brittle, and at the high temperatures involved in manufacturing, a large sheet that’s thin enough to use in a high-performance solid-state battery is likely to crack or warp.

      To determine the impact of such failures on cost, they modeled four key processing steps in assembling LLZO-based batteries. At each step, they calculated cost based on an assumed yield — that is, the fraction of total units that were successfully processed without failing. With the LLZO, the yield was far lower than with the other designs they examined; and, as the yield went down, the cost of each kilowatt-hour (kWh) of battery energy went up significantly. For example, when 5 percent more units failed during the final cathode heating step, cost increased by about $30/kWh — a nontrivial change considering that a commonly accepted target cost for such batteries is $100/kWh. Clearly, manufacturing difficulties can have a profound impact on the viability of a design for large-scale adoption.

      Materials and performance

      One of the main challenges in designing an all-solid battery comes from “interfaces” — that is, where one component meets another. During manufacturing or operation, materials at those interfaces can become unstable. “Atoms start going places that they shouldn’t, and battery performance declines,” says Huang.

      As a result, much research is devoted to coming up with methods of stabilizing interfaces in different battery designs. Many of the methods proposed do increase performance; and as a result, the cost of the battery in dollars per kWh goes down. But implementing such solutions generally involves added materials and time, increasing the cost per kWh during large-scale manufacturing.

      To illustrate that trade-off, the researchers first examined their oxide, LLZO. Here, the goal is to stabilize the interface between the LLZO electrolyte and the negative electrode by inserting a thin layer of tin between the two. They analyzed the impacts — both positive and negative — on cost of implementing that solution. They found that adding the tin separator increases energy-storage capacity and improves performance, which reduces the unit cost in dollars/kWh. But the cost of including the tin layer exceeds the savings so that the final cost is higher than the original cost.

      In another analysis, they looked at a sulfide electrolyte called LPSCl, which consists of lithium, phosphorus, and sulfur with a bit of added chlorine. In this case, the positive electrode incorporates particles of the electrolyte material — a method of ensuring that the lithium ions can find a pathway through the electrolyte to the other electrode. However, the added electrolyte particles are not compatible with other particles in the positive electrode — another interface problem. In this case, a standard solution is to add a “binder,” another material that makes the particles stick together.

      Their analysis confirmed that without the binder, performance is poor, and the cost of the LPSCl-based battery is more than $500/kWh. Adding the binder improves performance significantly, and the cost drops by almost $300/kWh. In this case, the cost of adding the binder during manufacturing is so low that essentially all the of the cost decrease from adding the binder is realized. Here, the method implemented to solve the interface problem pays off in lower costs.

      The researchers performed similar studies of other promising solid-state batteries reported in the literature, and their results were consistent: The choice of battery materials and processes can affect not only near-term outcomes in the lab but also the feasibility and cost of manufacturing the proposed solid-state battery at the scale needed to meet future demand. The results also showed that considering all three factors together — availability, processing needs, and battery performance — is important because there may be collective effects and trade-offs involved.

      Olivetti is proud of the range of concerns the team’s approach can probe. But she stresses that it’s not meant to replace traditional metrics used to guide materials and processing choices in the lab. “Instead, it’s meant to complement those metrics by also looking broadly at the sorts of things that could get in the way of scaling” — an important consideration given what Huang calls “the urgent ticking clock” of clean energy and climate change.

      This research was supported by the Seed Fund Program of the MIT Energy Initiative (MITEI) Low-Carbon Energy Center for Energy Storage; by Shell, a founding member of MITEI; and by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Office, under the Advanced Battery Materials Research Program. The text mining work was supported by the National Science Foundation, the Office of Naval Research, and MITEI.

      This article appears in the Spring 2021 issue of Energy Futures, the magazine of the MIT Energy Initiative. More