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      Alumnus’ thermal battery helps industry eliminate fossil fuels

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      The explosion of renewable energy projects around the globe is leading to a saturation problem. As more renewable power contributes to the grid, the value of electricity is plummeting during the times of day when wind and solar hit peak productivity. The problem is limiting renewable energy investments in some of the sunniest and windiest places in the world.

      Now Antora Energy, co-founded by David Bierman SM ’14, PhD ’17, is addressing the intermittent nature of wind and solar with a low-cost, highly efficient thermal battery that stores electricity as heat to allow manufacturers and other energy-hungry businesses to eliminate their use of fossil fuels.

      “We take electricity when it’s cheapest, meaning when wind gusts are strongest and the sun is shining brightest,” Bierman explains. “We run that electricity through a resistive heater to drive up the temperature of a very inexpensive material — we use carbon blocks, which are extremely stable, produced at incredible scales, and are some of the cheapest materials on Earth. When you need to pull energy from the battery, you open a large shutter to extract thermal radiation, which is used to generate process heat or power using our thermophotovoltaic, or TPV, technology. The end result is a zero-carbon, flexible, combined heat and power system for industry.”

      Antora’s battery could dramatically expand the application of renewable energy by enabling its use in industry, a sector of the U.S. economy that accounted for nearly a quarter of all greenhouse gas emissions in 2021.

      Antora says it is able to deliver on the long-sought promise of heat-to-power TPV technology because it has achieved new levels of efficiency and scalability with its cells. Earlier this year, Antora opened a new manufacturing facility that will be capable of producing 2 megawatts of its TPV cells each year — which the company says makes it the largest TPV production facility in the world.

      Antora’s thermal battery manufacturing facilities and demonstration unit are located in sun-soaked California, where renewables make up close to a third of all electricity. But Antora’s team says its technology holds promise in other regions as increasingly large renewable projects connect to grids across the globe.

      “We see places today [with high renewables] as a sign of where things are going,” Bierman says. “If you look at the tailwinds we have in the renewable industry, there’s a sense of inevitability about solar and wind, which will need to be deployed at incredible scales to avoid a climate catastrophe. We’ll see terawatts and terawatts of new additions of these renewables, so what you see today in California or Texas or Kansas, with significant periods of renewable overproduction, is just the tip of the iceberg.”

      Bierman has been working on thermal energy storage and thermophotovoltaics since his time at MIT, and Antora’s ties to MIT are especially strong because its progress is the result of two MIT startups becoming one.

      Alumni join forces

      Bierman did his masters and doctoral work in MIT’s Department of Mechanical Engineering, where he worked on solid-state solar thermal energy conversion systems. In 2016, while taking course 15.366 (Climate and Energy Ventures), he met Jordan Kearns SM ’17, then a graduate student in the Technology and Policy Program and the Department of Nuclear Science and Engineering. The two were studying renewable energy when they began to think about the intermittent nature of wind and solar as an opportunity rather than a problem.

      “There are already places in the U.S. where we have more wind and solar at times than we know what to do with,” Kearns says. “That is an opportunity for not only emissions reductions but also for reducing energy costs. What’s the application? I don’t think the overproduction of energy was being talked about as much as the intermittency problem.”

      Kearns did research through the MIT Energy Initiative and the researchers received support from MIT’s Venture Mentoring Service and the MIT Sandbox Innovation Fund to further explore ways to capitalize on fluctuating power prices.

      Kearns officially founded a company called Medley Thermal in 2017 to help companies that use natural gas switch to energy produced by renewables when the price was right. To accomplish that, he combined an off-the-shelf electric boiler with novel control software so the companies could switch energy sources seamlessly from fossil fuel to electricity at especially windy or sunny times. Medley went on to become a finalist for the MIT Clean Energy Prize, and Kearns wanted Bierman to join him as a co-founder, but Bierman had received a fellowship to commercialize a thermal energy storage solution and decided to pursue that after graduation.

      The split ended up working out for both alumni. In the ensuing years, Kearns led Medley Thermal through a number of projects in which gradually larger companies switched from relying on natural gas or propane sources to renewable electricity from the grid. The work culminated in an installment at the Jay Peak resort in Vermont that Kearns says is one of the largest projects in the U.S. using renewable energy to produce heat. The project is expected to reduce about 2,500 tons of carbon dioxide per year.

      Bierman, meanwhile, further developed a thermal energy storage solution for industrial decarbonization, which works by using renewable electricity to heat blocks of carbon, which are stored in insulation to retain energy for long periods of time. The heat from those blocks can then be used to deliver electricity or heat to customers, at temperatures that can exceed 1,500 C. When Antora raised a $50 million Series A funding round last year, Bierman asked Kearns if he could buy out Medley’s team, and the researchers finally became co-workers.

      “Antora and Medley Thermal have a similar value prop: There’s low-cost electricity, and we want to connect that to the industrial sector,” Kearns explains. “But whereas Medley used renewables on an as-available basis, and then when the winds stop we went back to burning fossil fuel with a boiler, Antora has a thermal battery that takes in the electricity, converts it to heat, but also stores it as heat so even when the wind stops blowing we have a reservoir of heat that we can continue to pull from to make steam or power or whatever the facility needs. So, we can now further reduce energy costs by offsetting more fuel and offer a 100 percent clean energy solution.”

      United we scale

      Today, Kearns runs the project development arm of Antora.

      “There are other, much larger projects in the pipeline,” Kearns says. “The Jay Peak project is about 3 megawatts of power, but some of the ones we’re working on now are 30, 60 megawatt projects. Those are more industrial focused, and they’re located in places where we have a strong industrial base and an abundance of renewables, everywhere from Texas to Kansas to the Dakotas — that heart of the country that our team lovingly calls the Wind Belt.”

      Antora’s future projects will be with companies in the chemicals, mining, food and beverage, and oil and gas industries. Some of those projects are expected to come online as early as 2025.          

      The company’s scaling strategy is centered on the inexpensive production process for its batteries.

      “We constantly ask ourselves, ‘What is the best product we can make here?’” Bierman says. “We landed on a compact, containerized, modular system that gets shipped to sites and is easily integrated into industrial processes. It means we don’t have huge construction projects, timelines, and budget overruns. Instead, it’s all about scaling up the factory that builds these thermal batteries and just churning them out.”

      It was a winding journey for Kearns and Bierman, but they now believe they’re positioned to help huge companies become carbon-free while promoting the growth of the solar and wind industries.

      “The more I dig into this, the more shocked I am at how important a piece of the decarbonization puzzle this is today,” Bierman says. “The need has become super real since we first started talking about this in 2016. The economic opportunity has grown, but more importantly the awareness from industries that they need to decarbonize is totally different. Antora can help with that, so we’re scaling up as rapidly as possible to meet the demand we see in the market.” More

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      in Energy

      Panel addresses technologies needed for a net-zero future

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      Five speakers at a recent public panel discussion hosted by the MIT Energy Initiative (MITEI) and introduced by Deputy Director for Science and Technology Robert Stoner tackled one of the thorniest, yet most critical, questions facing the world today: How can we achieve the ambitious goals set by governments around the globe, including the United States, to reach net zero emissions of greenhouse gases by mid-century?

      While the challenges are great, the panelists agreed, there is reason for optimism that these technological challenges can be solved. More uncertain, some suggested, are the social, economic, and political hurdles to bringing about the needed innovations.

      The speakers addressed areas where new or improved technologies or systems are needed if these ambitious goals are to be achieved. Anne White, aassociate provost and associate vice president for research administration and a professor of nuclear science and engineering at MIT, moderated the panel discussion. She said that achieving the ambitious net-zero goal “has to be accomplished by filling some gaps, and going after some opportunities.” In addressing some of these needs, she said the five topics chosen for the panel discussion were “places where MIT has significant expertise, and progress is already ongoing.”

      First of these was the heating and cooling of buildings. Christoph Reinhart, a professor of architecture and director of the Building Technology Program, said that currently about 1 percent of existing buildings are being retrofitted each year for energy efficiency and conversion from fossil-fuel heating systems to efficient electric ones — but that is not nearly enough to meet the 2050 net-zero target. “It’s an enormous task,” he said. To meet the goals, he said, would require increasing the retrofitting rate to 5 percent per year, and to require all new construction to be carbon neutral as well.

      Reinhart then showed a series of examples of how such conversions could take place using existing solar and heat pump technology, and depending on the configuration, how they could provide a payback to the homeowner within 10 years or less. However, without strong policy incentives the initial cost outlay for such a system, on the order of $50,000, is likely to put conversions out of reach of many people. Still, a recent survey found that 30 percent of homeowners polled said they would accept installation at current costs. While there is government money available for incentives for others, “we have to be very clever on how we spend all this money … and make sure that everybody is basically benefiting.”

      William Green, a professor of chemical engineering, spoke about the daunting challenge of bringing aviation to net zero. “More and more people like to travel,” he said, but that travel comes with carbon emissions that affect the climate, as well as air pollution that affects human health. The economic costs associated with these emissions, he said, are estimated at $860 per ton of jet fuel used — which is very close to the cost of the fuel itself. So the price paid by the airlines, and ultimately by the passengers, “is only about half of the true cost to society, and the other half is being borne by all of us, by the fact that it’s affecting the climate and it’s causing medical problems for people.”

      Eliminating those emissions is a major challenge, he said. Virtually all jet fuel today is fossil fuel, but airlines are starting to incorporate some biomass-based fuel, derived mostly from food waste. But even these fuels are not carbon-neutral, he said. “They actually have pretty significant carbon intensity.”

      But there are possible alternatives, he said, mostly based on using hydrogen produced by clean electricity, and making fuels out of that hydrogen by reacting it, for example, with carbon dioxide. This could indeed produce a carbon-neutral fuel that existing aircraft could use, but the process is costly, requiring a great deal of hydrogen, and ways of concentrating carbon dioxide. Other viable options also exist, but all would add significant expense, at least with present technology. “It’s going to cost a lot more for the passengers on the plane,” Green said, “But the society will benefit from that.”

      Increased electrification of heating and transportation in order to avoid the use of fossil fuels will place major demands on the existing electric grid systems, which have to perform a constant delicate balancing of production with demand. Anuradha Annaswamy, a senior research scientist in MIT’s mechanical engineering department, said “the electric grid is an engineering marvel.” In the United States it consists of 300,000 miles of transmission lines capable of carrying 470,000 megawatts of power.

      But with a projected doubling of energy from renewable sources entering the grid by 2030, and with a push to electrify everything possible — from transportation to buildings to industry — the load is not only increasing, but the patterns of both energy use and production are changing. Annaswamy said that “with all these new assets and decision-makers entering the picture, the question is how you can use a more sophisticated information layer that coordinates how all these assets are either consuming or producing or storing energy, and have that information layer coexist with the physical layer to make and deliver electricity in all these ways. It’s really not a simple problem.”

      But there are ways of addressing these complexities. “Certainly, emerging technologies in power electronics and control and communication can be leveraged,” she said. But she added that “This is not just a technology problem, really, it is something that requires technologists, economists, and policymakers to all come together.”

      As for industrial processes, Bilge Yildiz, a professor of nuclear science and engineering and materials science and engineering, said that “the synthesis of industrial chemicals and materials constitutes about 33 percent of global CO2 emissions at present, and so our goal is to decarbonize this difficult sector.” About half of all these industrial emissions come from the production of just four materials: steel, cement, ammonia, and ethylene, so there is a major focus of research on ways to reduce their emissions.

      Most of the processes to make these materials have changed little for more than a century, she said, and they are mostly heat-based processes that involve burning a lot of fossil fuel. But the heat can instead be provided from renewable electricity, which can also be used to drive electrochemical reactions in some cases as a substitute for the thermal reactions. Already, there are processes for making cement and steel that produce only about half the present carbon dioxide (CO2) emissions.

      The production of ammonia, which is widely used in fertilizer and other bulk chemicals, accounts for more greenhouse gas emissions than any other industrial source. The present thermochemical process could be replaced by an electrochemical process, she said. Similarly, the production of ethylene, as a feedstock for plastics and other materials, is the second-highest emissions producer, with three tons of carbon dioxide released for every ton of ethylene produced. Again, an electrochemical alternative method exists, but needs to be improved to be cost competitive.

      As the world moves toward electrification of industrial processes to eliminate fossil fuels, the need for emissions-free sources of electricity will continue to increase. One very promising potential addition to the range of carbon-free generation sources is fusion, a field in which MIT is a leader in developing a particularly promising technology that takes advantage of the unique properties of high-temperature superconducting (HTS) materials.

      Dennis Whyte, the director of MIT’s Plasma Science and Fusion Center, pointed out that despite global efforts to reduce CO2 emissions, “we use exactly the same percentage of carbon-based products to generate energy as 10 years ago, or 20 years ago.” To make a real difference in global emissions, “we need to make really massive amounts of carbon-free energy.”

      Fusion, the process that powers the sun, is a particularly promising pathway, because the fuel, derived from water, is virtually inexhaustible. By using recently developed HTS material to generate the powerful magnetic fields needed to produce a sustained fusion reaction, the MIT-led project, which led to a spinoff company called Commonwealth Fusion Systems, was able to radically reduce the required size of a fusion reactor, Whyte explained. Using this approach, the company, in collaboration with MIT, expects to have a fusion system that produces net energy by the middle of this decade, and be ready to build a commercial plant to produce power for the grid early in the next. Meanwhile, at least 25 other private companies are also attempting to commercialize fusion technology. “I think we can take some credit for helping to spawn what is essentially now a new industry in the United States,” Whyte said.

      Fusion offers the potential, along with existing solar and wind technologies, to provide the emissions-free power the world needs, Whyte says, but that’s only half the problem, the other part being how to get that power to where it’s needed, when it’s needed. “How do we adapt these new energy sources to be as compatible as possible with everything that we have already in terms of energy delivery?”

      Part of the way to find answers to that, he suggested, is more collaborative work on these issues that cut across disciplines, as well as more of the kinds of cross-cutting conversations and interactions that took place in this panel discussion. More

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      in Energy

      Powering the future in Mongolia

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      Nestled within the Tuul River valley and embraced by the southern Khentii Mountain Range, Ulaanbaatar (UB), Mongolia’s largest city, presents itself as an arena where nature’s forces wage an unrelenting battle against human resilience. The capital city is an icy crucible, with bone-chilling winters that plummet temperatures to an astonishing -40 degrees Fahrenheit (-40 degrees Celsius). Mongolia, often hailed with the celestial moniker of “The Land of the Eternal Blue Sky,” paradoxically succumbs to a veil of pollution and energy struggles during the winter months, obscuring the true shade of the cherished vista.

      To understand the root of these issues, MIT students from classes 22.S094 (Climate and Sustainability Systems: Decarbonizing Ulaanbaatar at Scale) and 21A.S01 (Anthro-Engineering: Decarbonization at the Million-Person Scale) visited Mongolia to conduct on-site surveys, diving into the diverse tapestry of local life as they gleaned insight from various stakeholder groups. Setting foot on Mongolian soil on a crisp day in January, they wasted no time in shaking off the weariness of their arduous 17-hour flight, promptly embarking on a waiting bus. As they traversed the vast expanse of the countryside, their eyes were captivated by snow-laden terrain.

      That is, until a disconcerting sight unfolded — thick smog, akin to ethereal pillars, permeated the cityscape ahead. These imposing plumes emanated from the colossal smokestacks of Ulaanbaatar’s coal-fired power plants, steadfastly churning electricity and heat to fuel Mongolia’s central and district energy systems. Over 93 percent of the nation’s energy comes from coal-fired power plants, where the most considerable load is caused by household consumption. Nevertheless, with nearly half of Ulaanbaatar’s population disconnected from the central heating networks, one of Mongolia’s most significant sources of pollution comes from coal-burning stoves in the residential settlements known as the ger districts. Over the past three decades, since the democratic revolution in 1990, Mongolians have grappled with escalating concerns surrounding energy provision, accessibility, and sustainability.

      Engineers who think like anthropologists

      “We find ourselves compelled to venture on-site, engaging in direct conversations with the locals, and immersing ourselves in the fabric of daily life to uncover what we don’t know,” emphasized Michael Short, professor in MIT’s Department of Nuclear Science and Engineering and faculty lead of MIT’s NEET Climate and Sustainability Systems thread, shortly before heading to Mongolia.

      The Ulaanbaatar Project sprang from a multiyear collaboration between MIT and the National University of Mongolia (NUM). Shedding light on the matter, Professor Munkhbat Byambajav of the Department of Chemical and Biological Engineering at NUM underscored the paramount importance of mitigating environmental pollution at an economic scale to alleviate the heavy burden borne by the people.

      Class 22.S094 is offered through MIT’s New Engineering Education Transformation (NEET) program, which allows students with multidisciplinary interests to collaborate across departments within four different subject areas, or threads. In this capstone project, students consider ways to decarbonize a city like Ulaanbaatar, transitioning from burning coal briquettes to a more sustainable, energy-efficient solution, given several parameters and constraints set by the local context.

      One of the ideas students have recently explored is a thermal battery made with molten salt that can store enough energy to heat a ger for up to 12 hours with added insulation for cooling curve regulation. The Mongolian ger, meaning home, is a dome-like portable dwelling covered in felt and canvas, held together by ropes traditionally crafted of animal hair or wool. Over several semesters, students have been testing a version of their proposed idea on campus, working with a prototype that weighs around 35 pounds.

      Nathan Melenbrink, the lead instructor of NEET’s Climate and Sustainability Systems (CSS) thread, believes that the complexity of the Ulaanbaatar capstone project allows students to reject the one-way solution approach and instead consider challenges with a nonprescriptive mindset. The uniqueness of the CSS thread is that students are asked to build on the previous findings from the past cohort and iterate on their designs each year. This workflow has allowed the project to mature and advance in ways that may not be feasible within a semester schedule. When asked how the recent trip impacted the ongoing research back on campus, Melenbrink states, “In light of the recent trip to Mongolia, students are beginning to see the impact of cultural immersion and social awareness leveraging the technical scope and rigor of their work.”

      Course 21A.S01, taught by Professor Manduhai Buyandelger of the MIT Anthropology Section, proved instrumental in deepening students’ understanding of the intricate dynamics at play. She asks, “The prototype works in the lab, but does it work in real life once you factor in the challenges in the larger structures of delivery, production, and implementation in Mongolia?”

      This recognition of the social dimensions of engineering permeated the early stages of the UB project, engaging all participants, including students from MIT and NUM, professionals residing in Mongolia, and local nongovernmental organizations, fostering what Buyandelger aptly describes as “a collaboration on multiple scales: trans-disciplinary and transcontinental.” Lauren Bonilla, co-lecturer for the anthropology course, was crucial in devising the first onsite trip to Mongolia. Drawing upon her extensive ethnographic research in Mongolia that spans decades, Bonilla remarks, “To me, engineering is a highly social discipline.” She further stresses how anthro-engineering elevates the social dimensions of engineering by critically questioning the framing of problems and solutions, stating, “It draws on anthropological insights and methods, like ethnography, to bring a human face to the users of a technology and adds complexity and nuance to the social constraints that limit designs.”

      Making of khorkhog

      Amidst the frigid atmosphere, a traditional Mongolian ger stands in front of the Nuclear Science Laboratory at the National University of Mongolia, emitting warm steam from its roof. The faculty and students of NUM organize a welcoming event inside the ger, inviting everyone to partake in a khorkhog cookout. Earlier that week, a remark from the Mongolian energy representative stood out during one of the presentations: “We need powerful heat. Solar is not enough, and electricity is not enough. Mongolians need fire,” he had emphasized.

      Indeed, the culinary delight known as khorkhog demands the relentless embrace of scorching flames. The process involves a large metal jug, stones, fire, and lamb. With skillful precision, the volunteer chef places the fire-heated stones and large pieces of lamb into the cooking container, triggering a cascade of steam that fills the ger, accompanied by the sounds of sizzling and hissing. Everyone waits patiently as the cook carefully inspects the dish, keenly listening for signs of readiness. And when the time comes, a feast is shared among all, complemented by steam-cooked potatoes, freshly sliced onions, and vegetables. In this moment, the presence of fire symbolizes a profound connection with the heart of Mongolian culture, evoking a deep resonance among the gathered crowd as they partake in this cherished staple meal.

      The distance between two points

      Familiar faces form a grid on the computer screen as the standing meeting between the students in Massachusetts and Ulaanbaatar begins. Sharing the morning (evening in Mongolia) for updates has been a critical effort by both sides to stay engaged and make decisions together. NEET CSS students in Cambridge proceeded to share their latest findings.

      Lucy Nester, a nuclear science and engineering major, has been diligently working on developing a high-efficiency electrical heating solution for individual consumers. Her primary focus is leveraging the discounted electricity rates available in the ger districts and utilize existing infrastructure. Recognizing the importance of maximum flexibility in heating the brick, Nester emphasizes the “no one-size-fits-all” solution. She shares the results of her test trials, which involve both inductive and resistive heating methods, outlining the advantages and disadvantages of each approach. Despite her limited experience in electrical engineering and circuit building, Nester has impressively overcome the steep learning curve. She enthusiastically describes her UB trip as “one of the most remarkable experiences I’ve had during my time at MIT.”

      Darshdeep Grewal, a dedicated materials science and engineering major with a strong passion for data science and computation, has been diligently conducting research on convection heating using COMSOL Multiphysics. In his investigation, Grewal explores the correlation between air temperature and heating, investigates the impact of convecting air arrangement on the heating process, and examines the conditions that may contribute to overheating. Leveraging his expertise in computational workflows, Grewal presents an impressive collection of heatmap simulations derived from the extensive data accumulated by his team throughout the project. Recognizing the immense value of these simulations in modeling complex scenarios, he highlights the importance of running experiments concurrently with simulations to ensure accurate calibration of results, stating, “It’s important to stay rooted in reality.”

      Arina Khotimsky, another materials science and engineering major, has actively engaged in NEET’s Climate and Sustainability Systems thread since her sophomore year. Balancing the demands of her final semester at MIT and the upcoming review of 22.S094, Khotimsky reveals how she has seamlessly integrated her project involvement into her energy studies minor. Reflecting on her journey, she remarks, “Working on the Ulaanbaatar project has taught me the significance of taking local context into account while suggesting solutions as an engineer.” Khotimsky has been tirelessly iterating and refining the insulation box prototype, which holds the thermal battery and controls the rate at which the battery releases heat. In addition, the on-site observations have unveiled another design challenge — ensuring the insulation box functions as a secure and dependable means of transportation. 

      To “engineer” means to contrive through one’s deliberate use of skills. What confronted the UB Project team on site was not the limitations of skill or technology, but the real-world constraints often amiss in the early equation: the people and their everyday lives. With over 6,195 miles of distance between the two groups, it takes more than just dedication to make a collaboration blossom. That may be the desire for a positive impact. Moreover, it may be the goal of cultivating a healthier relationship with energy that spans a million-person scale. No matter where you are, there is no one solution to the complex story of energy. This progressive realization brings the two teams together every two weeks in virtual space, bridging the distance between the two points.  More

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      in Environment

      Four researchers with MIT ties earn 2023 Schmidt Science Fellowships

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      Four researchers with ties to MIT have been named Schmidt Science Fellows this year. Lillian Chin ’17, SM ’19; Neil Dalvie PD ’22, PhD ’22; Suong Nguyen, and Yirui Zhang SM ’19, PhD ’23 are among the 32 exceptional early-career scientists worldwide chosen to receive the prestigious fellowships.

      “History provides powerful examples of what happens when scientists are given the freedom to ask big questions which can achieve real breakthroughs across disciplines,” says Wendy Schmidt, co-founder of Schmidt Futures and president of the Schmidt Family Foundation. “Schmidt Science Fellows are tackling climate destruction, discovering new drugs against disease, developing novel materials, using machine learning to understand the drivers of human health, and much more. This new cohort will add to this legacy in applying scientific discovery to improve human health and opportunity, and preserve and restore essential planetary systems.”

      Schmidt Futures is a philanthropic initiative that brings talented people together in networks to prove out their ideas and solve hard problems in science and society. Schmidt Science Fellows receive a stipend of $100,000 a year for up to two years of postdoctoral research in a discipline different from their PhD at a world-leading lab anywhere across the globe.

      Lillian Chin ’17, SM ’19 is currently pursuing her PhD in the Department of Electrical Engineering and Computer Science. Her research focuses on creating new materials for robots. By designing the geometry of a material, Chin creates new “meta-materials” that have different properties from the original. Using this technique, she has created robot balls that dramatically expand in volume and soft grippers that can work in dangerous environments. All of these robots are built out of a single material, letting the researchers 3D print them with extra internal features like channels. These channels help to measure the deformation of metamaterials, enabling Chin and her collaborators to create robots that are strong, can move, and sense their own shape, like muscles do.

      “I feel very honored to have been chosen for this fellowship,” says Chin. “I feel like I proposed a very risky pivot, since my background is only in engineering, with very limited exposure to neuroscience. I’m very excited to be given the opportunity to learn best practices for interacting with patients and be able to translate my knowledge from robotics to biology.”

      With the Schmidt Fellowship, Chin plans to pursue new frontiers for custom materials with internal sensors, which can measure force and deformation and can be placed anywhere within the material. “I want to use these materials to make tools for clinicians and neuroscientists to better understand how humans touch and grasp objects around them,” says Chin. “I’m especially interested in seeing how my materials could help in diagnosis motor-related diseases or improve rehab outcomes by providing the patient with feedback. This will help me create robots that have a better sense of touch and learn how to move objects around like humans do.”

      Neil Dalvie PD ’22, PhD ’22 is a graduate of the Department of Chemical Engineering, where he worked with Professor J. Christopher Love on manufacturing of therapeutic proteins. Dalvie developed molecular biology techniques for manufacturing high-quality proteins in yeast, which enables rapid testing of new products and low-cost manufacturing and large scales. During the pandemic, he led a team that applied these learnings to develop a Covid-19 vaccine that was deployed in multiple low-income countries. After graduating, Dalvie wanted to apply the precision biological engineering that is routinely deployed in medicinal manufacturing to other large-scale bioprocesses.

      “It’s rare for scientists to cross large technical gaps after so many years of specific training to get a PhD — you get comfy being an expert in your field,” says Dalvie. “I was definitely intimidated by the giant leap from vaccine manufacturing to the natural rock cycle. The fellowship has allowed me to dive into the new field by removing immediate pressure to publish or find my next job. I am excited for what commonalities we will find between biomanufacturing and biogeochemistry.”

      As a Schmidt Science Fellow, Dalvie will work with Professor Pamela Silver at Harvard Medical School on engineering microorganisms for enhanced rock weathering and carbon sequestration to combat climate change. They are applying modern molecular biology to enhance natural biogeochemical processes at gigaton scales.

      Suong (Su) Nguyen, a postdoctoral researcher in Professor Jeremiah Johnson’s lab in the Department of Chemistry, earned her PhD from Princeton University, where she developed light-driven, catalytic methodologies for organic synthesis, biomass valorization, plastic waste recycling, and functionalization of quantum sensing materials.

      As a Schmidt Science fellow, Nguyen will pivot from organic chemistry to nanomaterials. Biological systems are able to synthesize macromolecules with precise structure essential for their biological function. Scientists have long dreamed of achieving similar control over synthetic materials, but existing methods are inefficient and limited in scope. Nguyen hopes to develop new strategies to achieve such high level of control over the structure and properties of nanomaterials and explore their potential for use in therapeutic applications.

      “I feel extremely honored and grateful to receive the Schmidt Science Fellowship,” says Nguyen. “The fellowship will provide me with a unique opportunity to engage with scientists from a very wide range of research backgrounds. I believe this will significantly shape the research objectives for my future career.”

      Yirui Zhang SM ’19, PhD ’22 is a graduate of the Department of Mechanical Engineering. Zhang’s research focuses on electrochemical energy storage and conversion, including lithium-ion batteries and electrocatalysis. She has developed in situ spectroscopy and electrochemical methods to probe the electrode-electrolyte interface, understand the interfacial molecular structures, and unravel the fundamental thermodynamics and kinetics of (electro)chemical reactions in energy storage. Further, she has leveraged the physical chemistry of liquids and tuned the molecular structures at the interface to improve the stability and kinetics of electrochemical reactions. 

      “I am honored and thrilled to have been named a Schmidt Science Fellow,” says Zhang. “The fellowship will not only provide me with the unique opportunity to broaden my scientific perspectives and pursue pivoting research, but also create a lifelong network for us to collaborate across diverse fields and become scientific and societal thought leaders. I look forward to pushing the boundaries of my research and advancing technologies to tackle global challenges in energy storage and health care with interdisciplinary efforts!”

      As a Schmidt Science Fellow, Zhang will work across disciplines and pivot to biosensing. She plans to combine spectroscopy, electrokinetics, and machine learning to develop a fast and cost-effective technique for monitoring and understanding infectious disease. The innovations will benefit next-generation point-of-care medical devices and wastewater-based epidemiology to provide timely diagnosis and help protect humans against deadly infections and antimicrobial resistance. More

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      in Energy

      Exploring new sides of climate and sustainability research

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      When the MIT Climate and Sustainability Consortium (MCSC) launched its Climate and Sustainability Scholars Program in fall 2022, the goal was to offer undergraduate students a unique way to develop and implement research projects with the strong support of each other and MIT faculty. Now into its second semester, the program is underscoring the value of fostering this kind of network — a community with MIT students at its core, exploring their diverse interests and passions in the climate and sustainability realms.Inspired by MIT’s successful SuperUROP [Undergraduate Research Opportunities Program], the yearlong MCSC Climate and Sustainability Scholars Program includes a classroom component combined with experiential learning opportunities and mentorship, all centered on climate and sustainability topics.“Harnessing the innovation, passion, and expertise of our talented students is critical to MIT’s mission of tackling the climate crisis,” says Anantha P. Chandrakasan, dean of the School of Engineering, Vannevar Bush Professor of Electrical Engineering and Computer Science, and chair of the MCSC. “The program is helping train students from a variety of disciplines and backgrounds to be effective leaders in climate and sustainability-focused roles in the future.”

      “What we found inspiring about MIT’s existing SuperUROP program was how it provides students with the guidance, training, and resources they need to investigate the world’s toughest problems,” says Elsa Olivetti, the Esther and Harold E. Edgerton Associate Professor in Materials Science and Engineering and MCSC co-director. “This incredible level of support and mentorship encourages students to think and explore in creative ways, make new connections, and develop strategies and solutions that propel their work forward.”The first and current cohort of Climate and Sustainability Scholars consists of 19 students, representing MIT’s School of Engineering, MIT Schwarzman College of Computing, School of Science, School of Architecture and Planning, and MIT Sloan School of Management. These students are learning new perspectives, approaches, and angles in climate and sustainability — from each other, MIT faculty, and industry professionals.Projects with real-world applicationsStudents in the program work directly with faculty and principal investigators across MIT to develop their research projects focused on a large scope of sustainability topics.

      “This broad scope is important,” says Desirée Plata, MIT’s Gilbert W. Winslow Career Development Professor in Civil and Environmental Engineering, “because climate and sustainability solutions are needed in every facet of society. For a long time, people were searching for a ‘silver bullet’ solution to the climate change problems, but we didn’t get to this point with a single technological decision. This problem was created across a spectrum of sociotechnological activities, and fundamentally different thinking across a spectrum of solutions is what’s needed to move us forward. MCSC students are working to provide those solutions.”

      Undergraduate student and physics major M. (MG) Geogdzhayeva is working with Raffaele Ferrari, Cecil and Ida Green Professor of Oceanography in the Department of Earth, Atmospheric and Planetary Sciences, and director of the Program in Atmospheres, Oceans, and Climate, on their project “Using Continuous Time Markov Chains to Project Extreme Events under Climate.” Geogdzhayeva’s research supports the Flagship Climate Grand Challenges project that Ferrari is leading along with Professor Noelle Eckley Selin.

      “The project I am working on has a similar approach to the Climate Grand Challenges project entitled “Bringing computation to the climate challenge,” says Geogdzhayeva. “I am designing an emulator for climate extremes. Our goal is to boil down climate information to what is necessary and to create a framework that can deliver specific information — in order to develop valuable forecasts. As someone who comes from a physics background, the Climate and Sustainability Scholars Program has helped me think about how my research fits into the real world, and how it could be implemented.”

      Investigating technology and stakeholders

      Within technology development, Jade Chongsathapornpong, also a physics major, is diving into photo-modulated catalytic reactions for clean energy applications. Chongsathapornpong, who has worked with the MCSC on carbon capture and sequestration through the Undergraduate Research Opportunities Program (UROP), is now working with Harry Tuller, MIT’s R.P. Simmons Professor of Ceramics and Electronic Materials. Louise Anderfaas, majoring in materials science and engineering, is also working with Tuller on her project “Robust and High Sensitivity Detectors for Exploration of Deep Geothermal Wells.”Two other students who have worked with the MCSC through UROP include Paul Irvine, electrical engineering and computer science major, who is now researching American conservatism’s current relation to and views about sustainability and climate change, and Pamela Duke, management major, now investigating the use of simulation tools to empower industrial decision-makers around climate change action.Other projects focusing on technology development include the experimental characterization of poly(arylene ethers) for energy-efficient propane/propylene separations by Duha Syar, who is a chemical engineering major and working with Zachary Smith, the Robert N. Noyce Career Development Professor of Chemical Engineering; developing methods to improve sheet steel recycling by Rebecca Lizarde, who is majoring in materials science and engineering; and ion conduction in polymer-ceramic composite electrolytes by Melissa Stok, also majoring in materials science and engineering.

      Melissa Stok, materials science and engineering major, during a classroom discussion.

      Photo: Andrew Okyere

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      “My project is very closely connected to developing better Li-Ion batteries, which are extremely important in our transition towards clean energy,” explains Stok, who is working with Bilge Yildiz, MIT’s Breene M. Kerr (1951) Professor of Nuclear Science and Engineering. “Currently, electric cars are limited in their range by their battery capacity, so working to create more effective batteries with higher energy densities and better power capacities will help make these cars go farther and faster. In addition, using safer materials that do not have as high of an environmental toll for extraction is also important.” Claire Kim, a chemical engineering major, is focusing on batteries as well, but is honing in on large form factor batteries more relevant for grid-scale energy storage with Fikile Brushett, associate professor of chemical engineering.Some students in the program chose to focus on stakeholders, which, when it comes to climate and sustainability, can range from entities in business and industry to farmers to Indigenous people and their communities. Shivani Konduru, an electrical engineering and computer science major, is exploring the “backfire effects” in climate change communication, focusing on perceptions of climate change and how the messenger may change outcomes, and Einat Gavish, mathematics major, on how different stakeholders perceive information on driving behavior.Two students are researching the impact of technology on local populations. Anushree Chaudhuri, who is majoring in urban studies and planning, is working with Lawrence Susskind, Ford Professor of Urban and Environmental Planning, on community acceptance of renewable energy siting, and Amelia Dogan, also an urban studies and planning major, is working with Danielle Wood, assistant professor of aeronautics and astronautics and media arts and sciences, on Indigenous data sovereignty in environmental contexts.

      “I am interviewing Indigenous environmental activists for my project,” says Dogan. “This course is the first one directly related to sustainability that I have taken, and I am really enjoying it. It has opened me up to other aspects of climate beyond just the humanity side, which is my focus. I did MIT’s SuperUROP program and loved it, so was excited to do this similar opportunity with the climate and sustainability focus.”

      Other projects include in-field monitoring of water quality by Dahlia Dry, a physics major; understanding carbon release and accrual in coastal wetlands by Trinity Stallins, an urban studies and planning major; and investigating enzyme synthesis for bioremediation by Delight Nweneka, an electrical engineering and computer science major, each linked to the MCSC’s impact pathway work in nature-based solutions.

      The wide range of research topics underscores the Climate and Sustainability Program’s goal of bringing together diverse interests, backgrounds, and areas of study even within the same major. For example, Helena McDonald is studying pollution impacts of rocket launches, while Aviva Intveld is analyzing the paleoclimate and paleoenvironment background of the first peopling of the Americas. Both students are Earth, atmospheric and planetary sciences majors but are researching climate impacts from very different perspectives. Intveld was recently named a 2023 Gates Cambridge Scholar.

      “There are students represented from several majors in the program, and some people are working on more technical projects, while others are interpersonal. Both approaches are really necessary in the pursuit of climate resilience,” says Grace Harrington, who is majoring in civil and environmental engineering and whose project investigates ways to optimize the power of the wind farm. “I think it’s one of the few classes I’ve taken with such an interdisciplinary nature.”

      Shivani Konduru, electrical engineering and computer science major, during a classroom lecture

      Photo: Andrew Okyere

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      Perspectives and guidance from MIT and industry expertsAs students are developing these projects, they are also taking the program’s course (Climate.UAR), which covers key topics in climate change science, decarbonization strategies, policy, environmental justice, and quantitative methods for evaluating social and environmental impacts. The course is cross-listed in departments across all five schools and is taught by an experienced and interdisciplinary team. Desirée Plata was central to developing the Climate and Sustainability Scholars Programs and course with Associate Professor Elsa Olivetti, who taught the first semester. Olivetti is now co-teaching the second semester with Jeffrey C. Grossman, the Morton and Claire Goulder and Family Professor in Environmental Systems, head of the Department of Materials Science and Engineering, and MCSC co-director. The course’s writing instructors are Caroline Beimford and David Larson.  

      “I have been introduced to a lot of new angles in the climate space through the weekly guest lecturers, who each shared a different sustainability-related perspective,” says Claire Kim. “As a chemical engineering major, I have mostly looked into the technologies for decarbonization, and how to scale them, so learning about policy, for example, was helpful for me. Professor Black from the Department of History spoke about how we can analyze the effectiveness of past policy to guide future policy, while Professor Selin talked about framing different climate policies as having co-benefits. These perspectives are really useful because no matter how good a technology is, you need to convince other people to adopt it, or have strong policy in place to encourage its use, in order for it to be effective.”

      Bringing the industry perspective, guests have presented from MCSC member companies such as PepsiCo, Holcim, Apple, Cargill, and Boeing. As an example, in one class, climate leaders from three companies presented together on their approaches to setting climate goals, barriers to reaching them, and ways to work together. “When I presented to the class, alongside my counterparts at Apple and Boeing, the student questions pushed us to explain how can collaborate on ways to achieve our climate goals, reflecting the broader opportunity we find within the MCSC,” says Dana Boyer, sustainability manager at Cargill.

      Witnessing the cross-industry dynamics unfold in class was particularly engaging for the students. “The most beneficial part of the program for me is the number of guest lectures who have come in to the class, not only from MIT but also from the industry side,” Grace Harrington adds. “The diverse range of people talking about their own fields has allowed me to make connections between all my classes.”Bringing in perspectives from both academia and industry is a reflection of the MCSC’s larger mission of linking its corporate members with each other and with the MIT community to develop scalable climate solutions.“In addition to focusing on an independent research project and engaging with a peer community, we’ve had the opportunity to hear from speakers across the sustainability space who are also part of or closely connected to the MIT ecosystem,” says Anushree Chaudhuri. “These opportunities have helped me make connections and learn about initiatives at the Institute that are closely related to existing or planned student sustainability projects. These connections — across topics like waste management, survey best practices, and climate communications — have strengthened student projects and opened pathways for future collaborations.

      Basuhi Ravi, MIT PhD candidate, giving a guest lecture

      Photo: Andrew Okyere

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      Having a positive impact as students and after graduation

      At the start of the program, students identified several goals, including developing focused independent research questions, drawing connections and links with real-world challenges, strengthening their critical thinking skills, and reflecting on their future career ambitions. A common thread throughout them all: the commitment to having a meaningful impact on climate and sustainability challenges both as students now, and as working professionals after graduation.“I’ve absolutely loved connecting with like-minded peers through the program. I happened to know most of the students coming in from various other communities on campus, so it’s been a really special experience for all of these people who I couldn’t connect with as a cohesive cohort before to come together. Whenever we have small group discussions in class, I’m always grateful for the time to learn about the interdisciplinary research projects everyone is involved with,” concludes Chaudhuri. “I’m looking forward to staying in touch with this group going forward, since I think most of us are planning on grad school and/or careers related to climate and sustainability.”

      The MCSC Climate and Sustainability Scholars Program is representative of MIT’s ambitious and bold initiatives on climate and sustainability — bringing together faculty and students across MIT to collaborate with industry on developing climate and sustainability solutions in the context of undergraduate education and research. Learn about how you can get involved. More

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      Flow batteries for grid-scale energy storage

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      In the coming decades, renewable energy sources such as solar and wind will increasingly dominate the conventional power grid. Because those sources only generate electricity when it’s sunny or windy, ensuring a reliable grid — one that can deliver power 24/7 — requires some means of storing electricity when supplies are abundant and delivering it later when they’re not. And because there can be hours and even days with no wind, for example, some energy storage devices must be able to store a large amount of electricity for a long time.

      A promising technology for performing that task is the flow battery, an electrochemical device that can store hundreds of megawatt-hours of energy — enough to keep thousands of homes running for many hours on a single charge. Flow batteries have the potential for long lifetimes and low costs in part due to their unusual design. In the everyday batteries used in phones and electric vehicles, the materials that store the electric charge are solid coatings on the electrodes. “A flow battery takes those solid-state charge-storage materials, dissolves them in electrolyte solutions, and then pumps the solutions through the electrodes,” says Fikile Brushett, an associate professor of chemical engineering at MIT. That design offers many benefits and poses a few challenges.

      Flow batteries: Design and operation

      A flow battery contains two substances that undergo electrochemical reactions in which electrons are transferred from one to the other. When the battery is being charged, the transfer of electrons forces the two substances into a state that’s “less energetically favorable” as it stores extra energy. (Think of a ball being pushed up to the top of a hill.) When the battery is being discharged, the transfer of electrons shifts the substances into a more energetically favorable state as the stored energy is released. (The ball is set free and allowed to roll down the hill.)

      At the core of a flow battery are two large tanks that hold liquid electrolytes, one positive and the other negative. Each electrolyte contains dissolved “active species” — atoms or molecules that will electrochemically react to release or store electrons. During charging, one species is “oxidized” (releases electrons), and the other is “reduced” (gains electrons); during discharging, they swap roles. Pumps are used to circulate the two electrolytes through separate electrodes, each made of a porous material that provides abundant surfaces on which the active species can react. A thin membrane between the adjacent electrodes keeps the two electrolytes from coming into direct contact and possibly reacting, which would release heat and waste energy that could otherwise be used on the grid.

      When the battery is being discharged, active species on the negative side oxidize, releasing electrons that flow through an external circuit to the positive side, causing the species there to be reduced. The flow of those electrons through the external circuit can power the grid. In addition to the movement of the electrons, “supporting” ions — other charged species in the electrolyte — pass through the membrane to help complete the reaction and keep the system electrically neutral.

      Once all the species have reacted and the battery is fully discharged, the system can be recharged. In that process, electricity from wind turbines, solar farms, and other generating sources drives the reverse reactions. The active species on the positive side oxidize to release electrons back through the wires to the negative side, where they rejoin their original active species. The battery is now reset and ready to send out more electricity when it’s needed. Brushett adds, “The battery can be cycled in this way over and over again for years on end.”

      Benefits and challenges

      A major advantage of this system design is that where the energy is stored (the tanks) is separated from where the electrochemical reactions occur (the so-called reactor, which includes the porous electrodes and membrane). As a result, the capacity of the battery — how much energy it can store — and its power — the rate at which it can be charged and discharged — can be adjusted separately. “If I want to have more capacity, I can just make the tanks bigger,” explains Kara Rodby PhD ’22, a former member of Brushett’s lab and now a technical analyst at Volta Energy Technologies. “And if I want to increase its power, I can increase the size of the reactor.” That flexibility makes it possible to design a flow battery to suit a particular application and to modify it if needs change in the future.

      However, the electrolyte in a flow battery can degrade with time and use. While all batteries experience electrolyte degradation, flow batteries in particular suffer from a relatively faster form of degradation called “crossover.” The membrane is designed to allow small supporting ions to pass through and block the larger active species, but in reality, it isn’t perfectly selective. Some of the active species in one tank can sneak through (or “cross over”) and mix with the electrolyte in the other tank. The two active species may then chemically react, effectively discharging the battery. Even if they don’t, some of the active species is no longer in the first tank where it belongs, so the overall capacity of the battery is lower.

      Recovering capacity lost to crossover requires some sort of remediation — for example, replacing the electrolyte in one or both tanks or finding a way to reestablish the “oxidation states” of the active species in the two tanks. (Oxidation state is a number assigned to an atom or compound to tell if it has more or fewer electrons than it has when it’s in its neutral state.) Such remediation is more easily — and therefore more cost-effectively — executed in a flow battery because all the components are more easily accessed than they are in a conventional battery.

      The state of the art: Vanadium

      A critical factor in designing flow batteries is the selected chemistry. The two electrolytes can contain different chemicals, but today the most widely used setup has vanadium in different oxidation states on the two sides. That arrangement addresses the two major challenges with flow batteries.

      First, vanadium doesn’t degrade. “If you put 100 grams of vanadium into your battery and you come back in 100 years, you should be able to recover 100 grams of that vanadium — as long as the battery doesn’t have some sort of a physical leak,” says Brushett.

      And second, if some of the vanadium in one tank flows through the membrane to the other side, there is no permanent cross-contamination of the electrolytes, only a shift in the oxidation states, which is easily remediated by re-balancing the electrolyte volumes and restoring the oxidation state via a minor charge step. Most of today’s commercial systems include a pipe connecting the two vanadium tanks that automatically transfers a certain amount of electrolyte from one tank to the other when the two get out of balance.

      However, as the grid becomes increasingly dominated by renewables, more and more flow batteries will be needed to provide long-duration storage. Demand for vanadium will grow, and that will be a problem. “Vanadium is found around the world but in dilute amounts, and extracting it is difficult,” says Rodby. “So there are limited places — mostly in Russia, China, and South Africa — where it’s produced, and the supply chain isn’t reliable.” As a result, vanadium prices are both high and extremely volatile — an impediment to the broad deployment of the vanadium flow battery.

      Beyond vanadium

      The question then becomes: If not vanadium, then what? Researchers worldwide are trying to answer that question, and many are focusing on promising chemistries using materials that are more abundant and less expensive than vanadium. But it’s not that easy, notes Rodby. While other chemistries may offer lower initial capital costs, they may be more expensive to operate over time. They may require periodic servicing to rejuvenate one or both of their electrolytes. “You may even need to replace them, so you’re essentially incurring that initial (low) capital cost again and again,” says Rodby.

      Indeed, comparing the economics of different options is difficult because “there are so many dependent variables,” says Brushett. “A flow battery is an electrochemical system, which means that there are multiple components working together in order for the device to function. Because of that, if you are trying to improve a system — performance, cost, whatever — it’s very difficult because when you touch one thing, five other things change.”

      So how can we compare these new and emerging chemistries — in a meaningful way — with today’s vanadium systems? And how do we compare them with one another, so we know which ones are more promising and what the potential pitfalls are with each one? “Addressing those questions can help us decide where to focus our research and where to invest our research and development dollars now,” says Brushett.

      Techno-economic modeling as a guide

      A good way to understand and assess the economic viability of new and emerging energy technologies is using techno-economic modeling. With certain models, one can account for the capital cost of a defined system and — based on the system’s projected performance — the operating costs over time, generating a total cost discounted over the system’s lifetime. That result allows a potential purchaser to compare options on a “levelized cost of storage” basis.

      Using that approach, Rodby developed a framework for estimating the levelized cost for flow batteries. The framework includes a dynamic physical model of the battery that tracks its performance over time, including any changes in storage capacity. The calculated operating costs therefore cover all services required over decades of operation, including the remediation steps taken in response to species degradation and crossover.

      Analyzing all possible chemistries would be impossible, so the researchers focused on certain classes. First, they narrowed the options down to those in which the active species are dissolved in water. “Aqueous systems are furthest along and are most likely to be successful commercially,” says Rodby. Next, they limited their analyses to “asymmetric” chemistries; that is, setups that use different materials in the two tanks. (As Brushett explains, vanadium is unusual in that using the same “parent” material in both tanks is rarely feasible.) Finally, they divided the possibilities into two classes: species that have a finite lifetime and species that have an infinite lifetime; that is, ones that degrade over time and ones that don’t.

      Results from their analyses aren’t clear-cut; there isn’t a particular chemistry that leads the pack. But they do provide general guidelines for choosing and pursuing the different options.

      Finite-lifetime materials

      While vanadium is a single element, the finite-lifetime materials are typically organic molecules made up of multiple elements, among them carbon. One advantage of organic molecules is that they can be synthesized in a lab and at an industrial scale, and the structure can be altered to suit a specific function. For example, the molecule can be made more soluble, so more will be present in the electrolyte and the energy density of the system will be greater; or it can be made bigger so it won’t fit through the membrane and cross to the other side. Finally, organic molecules can be made from simple, abundant, low-cost elements, potentially even waste streams from other industries.

      Despite those attractive features, there are two concerns. First, organic molecules would probably need to be made in a chemical plant, and upgrading the low-cost precursors as needed may prove to be more expensive than desired. Second, these molecules are large chemical structures that aren’t always very stable, so they’re prone to degradation. “So along with crossover, you now have a new degradation mechanism that occurs over time,” says Rodby. “Moreover, you may figure out the degradation process and how to reverse it in one type of organic molecule, but the process may be totally different in the next molecule you work on, making the discovery and development of each new chemistry require significant effort.”

      Research is ongoing, but at present, Rodby and Brushett find it challenging to make the case for the finite-lifetime chemistries, mostly based on their capital costs. Citing studies that have estimated the manufacturing costs of these materials, Rodby believes that current options cannot be made at low enough costs to be economically viable. “They’re cheaper than vanadium, but not cheap enough,” says Rodby.

      The results send an important message to researchers designing new chemistries using organic molecules: Be sure to consider operating challenges early on. Rodby and Brushett note that it’s often not until way down the “innovation pipeline” that researchers start to address practical questions concerning the long-term operation of a promising-looking system. The MIT team recommends that understanding the potential decay mechanisms and how they might be cost-effectively reversed or remediated should be an upfront design criterion.

      Infinite-lifetime species

      The infinite-lifetime species include materials that — like vanadium — are not going to decay. The most likely candidates are other metals; for example, iron or manganese. “These are commodity-scale chemicals that will certainly be low cost,” says Rodby.

      Here, the researchers found that there’s a wider “design space” of feasible options that could compete with vanadium. But there are still challenges to be addressed. While these species don’t degrade, they may trigger side reactions when used in a battery. For example, many metals catalyze the formation of hydrogen, which reduces efficiency and adds another form of capacity loss. While there are ways to deal with the hydrogen-evolution problem, a sufficiently low-cost and effective solution for high rates of this side reaction is still needed.

      In addition, crossover is a still a problem requiring remediation steps. The researchers evaluated two methods of dealing with crossover in systems combining two types of infinite-lifetime species.

      The first is the “spectator strategy.” Here, both of the tanks contain both active species. Explains Brushett, “You have the same electrolyte mixture on both sides of the battery, but only one of the species is ever working and the other is a spectator.” As a result, crossover can be remediated in similar ways to those used in the vanadium flow battery. The drawback is that half of the active material in each tank is unavailable for storing charge, so it’s wasted. “You’ve essentially doubled your electrolyte cost on a per-unit energy basis,” says Rodby.

      The second method calls for making a membrane that is perfectly selective: It must let through only the supporting ion needed to maintain the electrical balance between the two sides. However, that approach increases cell resistance, hurting system efficiency. In addition, the membrane would need to be made of a special material — say, a ceramic composite — that would be extremely expensive based on current production methods and scales. Rodby notes that work on such membranes is under way, but the cost and performance metrics are “far off from where they’d need to be to make sense.”

      Time is of the essence

      The researchers stress the urgency of the climate change threat and the need to have grid-scale, long-duration storage systems at the ready. “There are many chemistries now being looked at,” says Rodby, “but we need to hone in on some solutions that will actually be able to compete with vanadium and can be deployed soon and operated over the long term.”

      The techno-economic framework is intended to help guide that process. It can calculate the levelized cost of storage for specific designs for comparison with vanadium systems and with one another. It can identify critical gaps in knowledge related to long-term operation or remediation, thereby identifying technology development or experimental investigations that should be prioritized. And it can help determine whether the trade-off between lower upfront costs and greater operating costs makes sense in these next-generation chemistries.

      The good news, notes Rodby, is that advances achieved in research on one type of flow battery chemistry can often be applied to others. “A lot of the principles learned with vanadium can be translated to other systems,” she says. She believes that the field has advanced not only in understanding but also in the ability to design experiments that address problems common to all flow batteries, thereby helping to prepare the technology for its important role of grid-scale storage in the future.

      This research was supported by the MIT Energy Initiative. Kara Rodby PhD ’22 was supported by an ExxonMobil-MIT Energy Fellowship in 2021-22.

      This article appears in the Winter 2023 issue of Energy Futures, the magazine of the MIT Energy Initiative. More

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      in Energy

      Shrinky Dinks, nail polish, and smelly bacteria

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      In a lab on the fourth floor of MIT’s Building 56, a group of Massachusetts high school students gathered around a device that measures conductivity.

      Vincent Nguyen, 15, from Saugus, thought of the times the material on their sample electrode flaked off the moment they took it out of the oven. Or how the electrode would fold weirdly onto itself. The big fails were kind of funny, but discouraging. The students had worked for a month, experimenting with different materials, and 17-year-old Brianna Tong of Malden wondered if they’d finally gotten it right: Would their electrode work well enough to power a microbial fuel cell?

      The students secured their electrode with alligator clips, someone hit start, and the teens watched anxiously as the device searched for even the faintest electrical current.

      Capturing electrons from bacteria

      Last July, Tong, Nguyen, and six other students from Malden Catholic High School commuted between the lab of MIT chemical engineer Ariel L. Furst and their school’s chemistry lab. Their goal was to fashion electrodes for low-cost microbial fuel cells — miniature bioreactors that generate small amounts of electricity by capturing electrons transferred from living microbes. These devices can double as electrochemical sensors.

      Furst, the Paul M. Cook Career Development Professor of Chemical Engineering, uses a mix of electrochemistry, microbial engineering, and materials science to address challenges in human health and clean energy. “The goal of all of our projects is to increase sustainability, clean energy, and health equity globally,” she says.

      Electrochemical sensors are powerful, sensitive detection and measurement tools. Typically, their electrodes need to be built in precisely engineered environments. “Thinking about ways of making devices without needing a cleanroom is important for coming up with inexpensive devices that can be deployed in low-resource settings under non-ideal conditions,” Furst says.

      For 17-year-old Angelina Ang of Everett, the project illuminated the significance of “coming together to problem-solve for a healthier and more sustainable earth,” she says. “It made me realize that we hold the answers to fix our dying planet.”

      With the help of a children’s toy called Shrinky Dinks, carbon-based materials, nail polish, and a certain smelly bacterium, the students got — literally — a trial-by-fire introduction to the scientific method. At one point, one of their experimental electrodes burst into flames. Other results were more promising.

      The students took advantage of the electrical properties of a bacterium — Shewanella oneidensis — that’s been called nature’s microscopic power plant. As part of their metabolism, Shewanella oneidensis generate electricity by oxidizing organic matter. In essence, they spit out electrons. Put enough together, and you get a few milliamps.

      To build bacteria-friendly electrodes, one of the first things the students did was culture Shewanella. They learned how to pour a growth medium into petri dishes where the reddish, normally lake-living bacteria could multiply. The microbes, Furst notes, are a little stinky, like cabbage. “But we think they’re really cool,” she says.

      With the right engineering, Shewanella can produce electric current when they detect toxins in water or soil. They could be used for bioremediation of wastewater. Low-cost versions could be useful for areas with limited or no access to reliable electricity and clean water.

      Next-generation chemists

      The Malden Catholic-MIT program resulted from a fluke encounter between Furst and a Malden Catholic parent.

      Mary-Margaret O’Donnell-Zablocki, then a medicinal chemist at a Kendall Square biotech startup, met Furst through a mutual friend. She asked Furst if she’d consider hosting high school chemistry students in her lab for the summer.

      Furst was intrigued. She traces her own passion for science to a program she’d happened upon between her junior and senior years in high school in St. Louis. The daughter of a software engineer and a businesswoman, Furst was casting around for potential career interests when she came across a summer program that enlisted scientists in academia and private research to introduce high school students and teachers to aspects of the scientific enterprise.

      “That’s when I realized that research is not like a lab class where there’s an expected outcome,” Furst recalls. “It’s so much cooler than that.”

      Using startup funding from an MIT Energy Initiative seed grant, Furst developed a curriculum with Malden Catholic chemistry teacher Seamus McGuire, and students were invited to apply. In addition to Tong, Ang, and Nguyen, participants included Chengxiang Lou, 18, from China; Christian Ogata, 14, of Wakefield; Kenneth Ramirez, 17, of Everett; Isaac Toscano, 17, of Medford; and MaryKatherine Zablocki, 15, of Revere and Wakefield. O’Donnell-Zablocki was surprised — and pleased — when her daughter applied to the program and was accepted.

      Furst notes that women are still underrepresented in chemical engineering. She was particularly excited to mentor young women through the program.

      A conductive ink

      The students were charged with identifying materials that had high conductivity, low resistance, were a bit soluble, and — with the help of a compatible “glue” — were able to stick to a substrate.

      Furst showed the Malden Catholic crew Shrinky Dinks — a common polymer popularized in the 1970s as a craft material that, when heated in a toaster oven, shrinks to a third of its size and becomes thicker and more rigid. Electrodes based on Shrinky Dinks would cost pennies, making it an ideal, inexpensive material for microbial fuel cells that could monitor, for instance, soil health in low- and middle-income countries.

      “Right now, monitoring soil health is problematic,” Furst says. “You have to collect a sample and bring it back to the lab to analyze in expensive equipment. But if we have these little devices that cost a couple of bucks each, we can monitor soil health remotely.”

      After a crash course in conductive carbon-based inks and solvent glues, the students went off to Malden Catholic to figure out what materials they wanted to try.

      Tong rattled them off: carbon nanotubes, carbon nanofibers, graphite powder, activated carbon. Potential solvents to help glue the carbon to the Shrinky Dinks included nail polish, corn syrup, and embossing ink, to name a few. They tested and retested. When they hit a dead end, they revised their hypotheses.

      They tried using a 3D printed stencil to daub the ink-glue mixture onto the Shrinky Dinks. They hand-painted them. They tried printing stickers. They worked with little squeegees. They tried scooping and dragging the material. Some of their electro-materials either flaked off or wouldn’t stick in the heating process.

      “Embossing ink never dried after baking the Shrinky Dink,” Ogata recalls. “In fact, it’s probably still liquid! And corn syrup had a tendency to boil. Seeing activated carbon ignite or corn syrup boiling in the convection oven was quite the spectacle.”

      “After the electrode was out of the oven and cooled down, we would check the conductivity,” says Tong, who plans to pursue a career in science. “If we saw there was a high conductivity, we got excited and thought those materials worked.”

      The moment of truth came in Furst’s MIT lab, where the students had access to more sophisticated testing equipment. Would their electrodes conduct electricity?

      Many of them didn’t. Tong says, “At first, we were sad, but then Dr. Furst told us that this is what science is, testing repeatedly and sometimes not getting the results we wanted.” Lou agrees. “If we just copy the data left by other scholars and don’t collect and figure it out by ourselves, then it is difficult to be a qualified researcher,” he says.

      Some of the students plan to continue the project one afternoon a week at MIT and as an independent study at Malden Catholic. The long-term goal is to create a field-based soil sensor that employs a bacterium like Shewanella.

      By chance, the students’ very first electrode — made of graphite powder ink and nail polish glue — generated the most current. One of the team’s biggest surprises was how much better black nail polish worked than clear nail polish. It turns out black nail polish contains iron-based pigment — a conductor. The unexpected win took some of the sting out of the failures.

      “They learned a very hard lesson: Your results might be awesome, and things are exciting, but then nothing else might work. And that’s totally fine,” Furst says.

      This article appears in the Winter 2023 issue of Energy Futures, the magazine of the MIT Energy Initiative. More

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      Using combustion to make better batteries

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      For more than a century, much of the world has run on the combustion of fossil fuels. Now, to avert the threat of climate change, the energy system is changing. Notably, solar and wind systems are replacing fossil fuel combustion for generating electricity and heat, and batteries are replacing the internal combustion engine for powering vehicles. As the energy transition progresses, researchers worldwide are tackling the many challenges that arise.

      Sili Deng has spent her career thinking about combustion. Now an assistant professor in the MIT Department of Mechanical Engineering and the Class of 1954 Career Development Professor, Deng leads a group that, among other things, develops theoretical models to help understand and control combustion systems to make them more efficient and to control the formation of emissions, including particles of soot.

      “So we thought, given our background in combustion, what’s the best way we can contribute to the energy transition?” says Deng. In considering the possibilities, she notes that combustion refers only to the process — not to what’s burning. “While we generally think of fossil fuels when we think of combustion, the term ‘combustion’ encompasses many high-temperature chemical reactions that involve oxygen and typically emit light and large amounts of heat,” she says.

      Given that definition, she saw another role for the expertise she and her team have developed: They could explore the use of combustion to make materials for the energy transition. Under carefully controlled conditions, combusting flames can be used to produce not polluting soot, but rather valuable materials, including some that are critical in the manufacture of lithium-ion batteries.

      Improving the lithium-ion battery by lowering costs

      The demand for lithium-ion batteries is projected to skyrocket in the coming decades. Batteries will be needed to power the growing fleet of electric cars and to store the electricity produced by solar and wind systems so it can be delivered later when those sources aren’t generating. Some experts project that the global demand for lithium-ion batteries may increase tenfold or more in the next decade.

      Given such projections, many researchers are looking for ways to improve the lithium-ion battery technology. Deng and her group aren’t materials scientists, so they don’t focus on making new and better battery chemistries. Instead, their goal is to find a way to lower the high cost of making all of those batteries. And much of the cost of making a lithium-ion battery can be traced to the manufacture of materials used to make one of its two electrodes — the cathode.

      The MIT researchers began their search for cost savings by considering the methods now used to produce cathode materials. The raw materials are typically salts of several metals, including lithium, which provides ions — the electrically charged particles that move when the battery is charged and discharged. The processing technology aims to produce tiny particles, each one made up of a mixture of those ingredients, with the atoms arranged in the specific crystalline structure that will deliver the best performance in the finished battery.

      For the past several decades, companies have manufactured those cathode materials using a two-stage process called coprecipitation. In the first stage, the metal salts — excluding the lithium — are dissolved in water and thoroughly mixed inside a chemical reactor. Chemicals are added to change the acidity (the pH) of the mixture, and particles made up of the combined salts precipitate out of the solution. The particles are then removed, dried, ground up, and put through a sieve.

      A change in pH won’t cause lithium to precipitate, so it is added in the second stage. Solid lithium is ground together with the particles from the first stage until lithium atoms permeate the particles. The resulting material is then heated, or “annealed,” to ensure complete mixing and to achieve the targeted crystalline structure. Finally, the particles go through a “deagglomerator” that separates any particles that have joined together, and the cathode material emerges.

      Coprecipitation produces the needed materials, but the process is time-consuming. The first stage takes about 10 hours, and the second stage requires about 13 hours of annealing at a relatively low temperature (750 degrees Celsius). In addition, to prevent cracking during annealing, the temperature is gradually “ramped” up and down, which takes another 11 hours. The process is thus not only time-consuming but also energy-intensive and costly.

      For the past two years, Deng and her group have been exploring better ways to make the cathode material. “Combustion is very effective at oxidizing things, and the materials for lithium-ion batteries are generally mixtures of metal oxides,” says Deng. That being the case, they thought this could be an opportunity to use a combustion-based process called flame synthesis.

      A new way of making a high-performance cathode material

      The first task for Deng and her team — mechanical engineering postdoc Jianan Zhang, Valerie L. Muldoon ’20, SM ’22, and current graduate students Maanasa Bhat and Chuwei Zhang — was to choose a target material for their study. They decided to focus on a mixture of metal oxides consisting of nickel, cobalt, and manganese plus lithium. Known as “NCM811,” this material is widely used and has been shown to produce cathodes for batteries that deliver high performance; in an electric vehicle, that means a long driving range, rapid discharge and recharge, and a long lifetime. To better define their target, the researchers examined the literature to determine the composition and crystalline structure of NCM811 that has been shown to deliver the best performance as a cathode material.

      They then considered three possible approaches to improving on the coprecipitation process for synthesizing NCM811: They could simplify the system (to cut capital costs), speed up the process, or cut the energy required.

      “Our first thought was, what if we can mix together all of the substances — including the lithium — at the beginning?” says Deng. “Then we would not need to have the two stages” — a clear simplification over coprecipitation.

      Introducing FASP

      One process widely used in the chemical and other industries to fabricate nanoparticles is a type of flame synthesis called flame-assisted spray pyrolysis, or FASP. Deng’s concept for using FASP to make their targeted cathode powders proceeds as follows.

      The precursor materials — the metal salts (including the lithium) — are mixed with water, and the resulting solution is sprayed as fine droplets by an atomizer into a combustion chamber. There, a flame of burning methane heats up the mixture. The water evaporates, leaving the precursor materials to decompose, oxidize, and solidify to form the powder product. The cyclone separates particles of different sizes, and the baghouse filters out those that aren’t useful. The collected particles would then be annealed and deagglomerated.

      To investigate and optimize this concept, the researchers developed a lab-scale FASP setup consisting of a homemade ultrasonic nebulizer, a preheating section, a burner, a filter, and a vacuum pump that withdraws the powders that form. Using that system, they could control the details of the heating process: The preheating section replicates conditions as the material first enters the combustion chamber, and the burner replicates conditions as it passes the flame. That setup allowed the team to explore operating conditions that would give the best results.

      Their experiments showed marked benefits over coprecipitation. The nebulizer breaks up the liquid solution into fine droplets, ensuring atomic-level mixing. The water simply evaporates, so there’s no need to change the pH or to separate the solids from a liquid. As Deng notes, “You just let the gas go, and you’re left with the particles, which is what you want.” With lithium included at the outset, there’s no need for mixing solids with solids, which is neither efficient 
nor effective.

      They could even control the structure, or “morphology,” of the particles that formed. In one series of experiments, they tried exposing the incoming spray to different rates of temperature change over time. They found that the temperature “history” has a direct impact on morphology. With no preheating, the particles burst apart; and with rapid preheating, the particles were hollow. The best outcomes came when they used temperatures ranging from 175-225 C. Experiments with coin-cell batteries (laboratory devices used for testing battery materials) confirmed that by adjusting the preheating temperature, they could achieve a particle morphology that would optimize the performance of their materials.

      Best of all, the particles formed in seconds. Assuming the time needed for conventional annealing and deagglomerating, the new setup could synthesize the finished cathode material in half the total time needed for coprecipitation. Moreover, the first stage of the coprecipitation system is replaced by a far simpler setup — a savings in capital costs.

      “We were very happy,” says Deng. “But then we thought, if we’ve changed the precursor side so the lithium is mixed well with the salts, do we need to have the same process for the second stage? Maybe not!”

      Improving the second stage

      The key time- and energy-consuming step in the second stage is the annealing. In today’s coprecipitation process, the strategy is to anneal at a low temperature for a long time, giving the operator time to manipulate and control the process. But running a furnace for some 20 hours — even at a low temperature — consumes a lot of energy.

      Based on their studies thus far, Deng thought, “What if we slightly increase the temperature but reduce the annealing time by orders of magnitude? Then we could cut energy consumption, and we might still achieve the desired crystal structure.”

      However, experiments at slightly elevated temperatures and short treatment times didn’t bring the results they had hoped for. In transmission electron microscope (TEM) images, the particles that formed had clouds of light-looking nanoscale particles attached to their surfaces. When the researchers performed the same experiments without adding the lithium, those nanoparticles didn’t appear. Based on that and other tests, they concluded that the nanoparticles were pure lithium. So, it seemed like long-duration annealing would be needed to ensure that the lithium made its way inside the particles.

      But they then came up with a different solution to the lithium-distribution problem. They added a small amount — just 1 percent by weight — of an inexpensive compound called urea to their mixture. In TEM images of the particles formed, the “undesirable nanoparticles were largely gone,” says Deng.

      Experiments in the laboratory coin cells showed that the addition of urea significantly altered the response to changes in the annealing temperature. When the urea was absent, raising the annealing temperature led to a dramatic decline in performance of the cathode material that formed. But with the urea present, the performance of the material that formed was unaffected by any temperature change.

      That result meant that — as long as the urea was added with the other precursors — they could push up the temperature, shrink the annealing time, and omit the gradual ramp-up and cool-down process. Further imaging studies confirmed that their approach yields the desired crystal structure and the homogeneous elemental distribution of the cobalt, nickel, manganese, and lithium within the particles. Moreover, in tests of various performance measures, their materials did as well as materials produced by coprecipitation or by other methods using long-time heat treatment. Indeed, the performance was comparable to that of commercial batteries with cathodes made of NCM811.

      So now the long and expensive second stage required in standard coprecipitation could be replaced by just 20 minutes of annealing at about 870 C plus 20 minutes of cooling down at room temperature.

      Theory, continuing work, and planning for scale-up

      While experimental evidence supports their approach, Deng and her group are now working to understand why it works. “Getting the underlying physics right will help us design the process to control the morphology and to scale up the process,” says Deng. And they have a hypothesis for why the lithium nanoparticles in their flame synthesis process end up on the surfaces of the larger particles — and why the presence of urea solves that problem.

      According to their theory, without the added urea, the metal and lithium atoms are initially well-mixed within the droplet. But as heating progresses, the lithium diffuses to the surface and ends up as nanoparticles attached to the solidified particle. As a result, a long annealing process is needed to move the lithium in among the other atoms.

      When the urea is present, it starts out mixed with the lithium and other atoms inside the droplet. As temperatures rise, the urea decomposes, forming bubbles. As heating progresses, the bubbles burst, increasing circulation, which keeps the lithium from diffusing to the surface. The lithium ends up uniformly distributed, so the final heat treatment can be very short.

      The researchers are now designing a system to suspend a droplet of their mixture so they can observe the circulation inside it, with and without the urea present. They’re also developing experiments to examine how droplets vaporize, employing tools and methods they have used in the past to study how hydrocarbons vaporize inside internal combustion engines.

      They also have ideas about how to streamline and scale up their process. In coprecipitation, the first stage takes 10 to 20 hours, so one batch at a time moves on to the second stage to be annealed. In contrast, the novel FASP process generates particles in 20 minutes or less — a rate that’s consistent with continuous processing. In their design for an “integrated synthesis system,” the particles coming out of the baghouse are deposited on a belt that carries them for 10 or 20 minutes through a furnace. A deagglomerator then breaks any attached particles apart, and the cathode powder emerges, ready to be fabricated into a high-performance cathode for a lithium-ion battery. The cathode powders for high-performance lithium-ion batteries would thus be manufactured at unprecedented speed, low cost, and low energy use.

      Deng notes that every component in their integrated system is already used in industry, generally at a large scale and high flow-through rate. “That’s why we see great potential for our technology to be commercialized and scaled up,” she says. “Where our expertise comes into play is in designing the combustion chamber to control the temperature and heating rate so as to produce particles with the desired morphology.” And while a detailed economic analysis has yet to be performed, it seems clear that their technique will be faster, the equipment simpler, and the energy use lower than other methods of manufacturing cathode materials for lithium-ion batteries — potentially a major contribution to the ongoing energy transition.

      This research was supported by the MIT Department of Mechanical Engineering.

      This article appears in the Winter 2023 issue of Energy Futures, the magazine of the MIT Energy Initiative. More