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    Fast-tracking fusion energy’s arrival with AI and accessibility

    As the impacts of climate change continue to grow, so does interest in fusion’s potential as a clean energy source. While fusion reactions have been studied in laboratories since the 1930s, there are still many critical questions scientists must answer to make fusion power a reality, and time is of the essence. As part of their strategy to accelerate fusion energy’s arrival and reach carbon neutrality by 2050, the U.S. Department of Energy (DoE) has announced new funding for a project led by researchers at MIT’s Plasma Science and Fusion Center (PSFC) and four collaborating institutions.

    Cristina Rea, a research scientist and group leader at the PSFC, will serve as the primary investigator for the newly funded three-year collaboration to pilot the integration of fusion data into a system that can be read by AI-powered tools. The PSFC, together with scientists from the College of William and Mary, the University of Wisconsin at Madison, Auburn University, and the nonprofit HDF Group, plan to create a holistic fusion data platform, the elements of which could offer unprecedented access for researchers, especially underrepresented students. The project aims to encourage diverse participation in fusion and data science, both in academia and the workforce, through outreach programs led by the group’s co-investigators, of whom four out of five are women. 

    The DoE’s award, part of a $29 million funding package for seven projects across 19 institutions, will support the group’s efforts to distribute data produced by fusion devices like the PSFC’s Alcator C-Mod, a donut-shaped “tokamak” that utilized powerful magnets to control and confine fusion reactions. Alcator C-Mod operated from 1991 to 2016 and its data are still being studied, thanks in part to the PSFC’s commitment to the free exchange of knowledge.

    Currently, there are nearly 50 public experimental magnetic confinement-type fusion devices; however, both historical and current data from these devices can be difficult to access. Some fusion databases require signing user agreements, and not all data are catalogued and organized the same way. Moreover, it can be difficult to leverage machine learning, a class of AI tools, for data analysis and to enable scientific discovery without time-consuming data reorganization. The result is fewer scientists working on fusion, greater barriers to discovery, and a bottleneck in harnessing AI to accelerate progress.

    The project’s proposed data platform addresses technical barriers by being FAIR — Findable, Interoperable, Accessible, Reusable — and by adhering to UNESCO’s Open Science (OS) recommendations to improve the transparency and inclusivity of science; all of the researchers’ deliverables will adhere to FAIR and OS principles, as required by the DoE. The platform’s databases will be built using MDSplusML, an upgraded version of the MDSplus open-source software developed by PSFC researchers in the 1980s to catalogue the results of Alcator C-Mod’s experiments. Today, nearly 40 fusion research institutes use MDSplus to store and provide external access to their fusion data. The release of MDSplusML aims to continue that legacy of open collaboration.

    The researchers intend to address barriers to participation for women and disadvantaged groups not only by improving general access to fusion data, but also through a subsidized summer school that will focus on topics at the intersection of fusion and machine learning, which will be held at William and Mary for the next three years.

    Of the importance of their research, Rea says, “This project is about responding to the fusion community’s needs and setting ourselves up for success. Scientific advancements in fusion are enabled via multidisciplinary collaboration and cross-pollination, so accessibility is absolutely essential. I think we all understand now that diverse communities have more diverse ideas, and they allow faster problem-solving.”

    The collaboration’s work also aligns with vital areas of research identified in the International Atomic Energy Agency’s “AI for Fusion” Coordinated Research Project (CRP). Rea was selected as the technical coordinator for the IAEA’s CRP emphasizing community engagement and knowledge access to accelerate fusion research and development. In a letter of support written for the group’s proposed project, the IAEA stated that, “the work [the researchers] will carry out […] will be beneficial not only to our CRP but also to the international fusion community in large.”

    PSFC Director and Hitachi America Professor of Engineering Dennis Whyte adds, “I am thrilled to see PSFC and our collaborators be at the forefront of applying new AI tools while simultaneously encouraging and enabling extraction of critical data from our experiments.”

    “Having the opportunity to lead such an important project is extremely meaningful, and I feel a responsibility to show that women are leaders in STEM,” says Rea. “We have an incredible team, strongly motivated to improve our fusion ecosystem and to contribute to making fusion energy a reality.” More

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    Ms. Nuclear Energy is winning over nuclear skeptics

    First-year MIT nuclear science and engineering (NSE) doctoral student Kaylee Cunningham is not the first person to notice that nuclear energy has a public relations problem. But her commitment to dispel myths about the alternative power source has earned her the moniker “Ms. Nuclear Energy” on TikTok and a devoted fan base on the social media platform.

    Cunningham’s activism kicked into place shortly after a week-long trip to Iceland to study geothermal energy. During a discussion about how the country was going to achieve its net zero energy goals, a representative from the University of Reykjavik balked at Cunnigham’s suggestion of including a nuclear option in the alternative energy mix. “The response I got was that we’re a peace-loving nation, we don’t do that,” Cunningham remembers. “I was appalled by the reaction, I mean we’re talking energy not weapons here, right?” she asks. Incredulous, Cunningham made a TikTok that targeted misinformation. Overnight she garnered 10,000 followers and “Ms. Nuclear Energy” was off to the races. Ms. Nuclear Energy is now Cunningham’s TikTok handle.

    Kaylee Cunningham: Dispelling myths and winning over skeptics

    A theater and science nerd

    TikTok is a fitting platform for a theater nerd like Cunningham. Born in Melrose, Massachusetts, Cunningham’s childhood was punctuated by moves to places where her roofer father’s work took the family. She moved to North Carolina shortly after fifth grade and fell in love with theater. “I was doing theater classes, the spring musical, it was my entire world,” Cunningham remembers. When she moved again, this time to Florida halfway through her first year of high school, she found the spring musical had already been cast. But she could help behind the scenes. Through that work, Cunningham gained her first real exposure to hands-on tech. She was hooked.

    Soon Cunningham was part of a team that represented her high school at the student Astronaut Challenge, an aerospace competition run by Florida State University. Statewide winners got to fly a space shuttle simulator at the Kennedy Space Center and participate in additional engineering challenges. Cunningham’s team was involved in creating a proposal to help NASA’s Asteroid Redirect Mission, designed to help the agency gather a large boulder from a near-earth asteroid. The task was Cunningham’s induction into an understanding of radiation and “anything nuclear.” Her high school engineering teacher, Nirmala Arunachalam, encouraged Cunningham’s interest in the subject.

    The Astronaut Challenge might just have been the end of Cunningham’s path in nuclear engineering had it not been for her mother. In high school, Cunningham had also enrolled in computer science classes and her love of the subject earned her a scholarship at Norwich University in Vermont where she had pursued a camp in cybersecurity. Cunningham had already laid down the college deposit for Norwich.

    But Cunningham’s mother persuaded her daughter to pay another visit to the University of Florida, where she had expressed interest in pursuing nuclear engineering. To her pleasant surprise, the department chair, Professor James Baciak, pulled out all the stops, bringing mother and daughter on a tour of the on-campus nuclear reactor and promising Cunningham a paid research position. Cunningham was sold and Backiak has been a mentor throughout her research career.

    Merging nuclear engineering and computer science

    Undergraduate research internships, including one at Oak Ridge National Laboratory, where she could combine her two loves, nuclear engineering and computer science, convinced Cunningham she wanted to pursue a similar path in graduate school.

    Cunningham’s undergraduate application to MIT had been rejected but that didn’t deter her from applying to NSE for graduate school. Having spent her early years in an elementary school barely 20 minutes from campus, she had grown up hearing that “the smartest people in the world go to MIT.” Cunningham figured that if she got into MIT, it would be “like going back home to Massachusetts” and that she could fit right in.

    Under the advisement of Professor Michael Short, Cunningham is looking to pursue her passions in both computer science and nuclear engineering in her doctoral studies.

    The activism continues

    Simultaneously, Cunningham is determined to keep her activism going.

    Her ability to digest “complex topics into something understandable to people who have no connection to academia” has helped Cunningham on TikTok. “It’s been something I’ve been doing all my life with my parents and siblings and extended family,” she says.

    Punctuating her video snippets with humor — a Simpsons reference is par for the course — helps Cunningham break through to her audience who love her goofy and tongue-in-cheek approach to the subject matter without compromising accuracy. “Sometimes I do stupid dances and make a total fool of myself, but I’ve really found my niche by being willing to engage and entertain people and educate them at the same time.”

    Such education needs to be an important part of an industry that’s received its share of misunderstandings, Cunningham says. “Technical people trying to communicate in a way that the general people don’t understand is such a concerning thing,” she adds. Case in point: the response in the wake of the Three Mile Island accident, which prevented massive contamination leaks. It was a perfect example of how well our safety regulations actually work, Cunningham says, “but you’d never guess from the PR fallout from it all.”

    As Ms. Nuclear Energy, Cunningham receives her share of skepticism. One viewer questioned the safety of nuclear reactors if “tons of pollution” was spewing out from them. Cunningham produced a TikTok that addressed this misconception. Pointing to the “pollution” in a photo, Cunningham clarifies that it’s just water vapor. The TikTok has garnered over a million views. “It really goes to show how starving for accurate information the public really is,” Cunningham says, “ in this age of having all the information we could ever want at our fingertips, it’s hard to sift through and decide what’s real and accurate and what isn’t.”

    Another reason for her advocacy: doing her part to encourage young people toward a nuclear science or engineering career. “If we’re going to start putting up tons of small modular reactors around the country, we need people to build them, people to run them, and we need regulatory bodies to inspect and keep them safe,” Cunningham points out. “ And we don’t have enough people entering the workforce in comparison to those that are retiring from the workforce,” she adds. “I’m able to engage those younger audiences and put nuclear engineering on their radar,” Cunningham says. The advocacy has been paying off: Cunningham regularly receives — and responds to — inquiries from high school junior girls looking for advice on pursuing nuclear engineering.

    All the activism is in service toward a clear end goal. “At the end of the day, the fight is to save the planet,” Cunningham says, “I honestly believe that nuclear power is the best chance we’ve got to fight climate change and keep our planet alive.” More

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    To improve solar and other clean energy tech, look beyond hardware

    To continue reducing the costs of solar energy and other clean energy technologies, scientists and engineers will likely need to focus, at least in part, on improving technology features that are not based on hardware, according to MIT researchers. They describe this finding and the mechanisms behind it today in Nature Energy.

    While the cost of installing a solar energy system has dropped by more than 99 percent since 1980, this new analysis shows that “soft technology” features, such as the codified permitting practices, supply chain management techniques, and system design processes that go into deploying a solar energy plant, contributed only 10 to 15 percent of total cost declines. Improvements to hardware features were responsible for the lion’s share.

    But because soft technology is increasingly dominating the total costs of installing solar energy systems, this trend threatens to slow future cost savings and hamper the global transition to clean energy, says the study’s senior author, Jessika Trancik, a professor in MIT’s Institute for Data, Systems, and Society (IDSS).

    Trancik’s co-authors include lead author Magdalena M. Klemun, a former IDSS graduate student and postdoc who is now an assistant professor at the Hong Kong University of Science and Technology; Goksin Kavlak, a former IDSS graduate student and postdoc who is now an associate at the Brattle Group; and James McNerney, a former IDSS postdoc and now senior research fellow at the Harvard Kennedy School.

    The team created a quantitative model to analyze the cost evolution of solar energy systems, which captures the contributions of both hardware technology features and soft technology features.

    The framework shows that soft technology hasn’t improved much over time — and that soft technology features contributed even less to overall cost declines than previously estimated.

    Their findings indicate that to reverse this trend and accelerate cost declines, engineers could look at making solar energy systems less reliant on soft technology to begin with, or they could tackle the problem directly by improving inefficient deployment processes.  

    “Really understanding where the efficiencies and inefficiencies are, and how to address those inefficiencies, is critical in supporting the clean energy transition. We are making huge investments of public dollars into this, and soft technology is going to be absolutely essential to making those funds count,” says Trancik.

    “However,” Klemun adds, “we haven’t been thinking about soft technology design as systematically as we have for hardware. That needs to change.”

    The hard truth about soft costs

    Researchers have observed that the so-called “soft costs” of building a solar power plant — the costs of designing and installing the plant — are becoming a much larger share of total costs. In fact, the share of soft costs now typically ranges from 35 to 64 percent.

    “We wanted to take a closer look at where these soft costs were coming from and why they weren’t coming down over time as quickly as the hardware costs,” Trancik says.

    In the past, scientists have modeled the change in solar energy costs by dividing total costs into additive components — hardware components and nonhardware components — and then tracking how these components changed over time.

    “But if you really want to understand where those rates of change are coming from, you need to go one level deeper to look at the technology features. Then things split out differently,” Trancik says.

    The researchers developed a quantitative approach that models the change in solar energy costs over time by assigning contributions to the individual technology features, including both hardware features and soft technology features.

    For instance, their framework would capture how much of the decline in system installation costs — a soft cost — is due to standardized practices of certified installers — a soft technology feature. It would also capture how that same soft cost is affected by increased photovoltaic module efficiency — a hardware technology feature.

    With this approach, the researchers saw that improvements in hardware had the greatest impacts on driving down soft costs in solar energy systems. For example, the efficiency of photovoltaic modules doubled between 1980 and 2017, reducing overall system costs by 17 percent. But about 40 percent of that overall decline could be attributed to reductions in soft costs tied to improved module efficiency.

    The framework shows that, while hardware technology features tend to improve many cost components, soft technology features affect only a few.

    “You can see this structural difference even before you collect data on how the technologies have changed over time. That’s why mapping out a technology’s network of cost dependencies is a useful first step to identify levers of change, for solar PV and for other technologies as well,” Klemun notes.  

    Static soft technology

    The researchers used their model to study several countries, since soft costs can vary widely around the world. For instance, solar energy soft costs in Germany are about 50 percent less than those in the U.S.

    The fact that hardware technology improvements are often shared globally led to dramatic declines in costs over the past few decades across locations, the analysis showed. Soft technology innovations typically aren’t shared across borders. Moreover, the team found that countries with better soft technology performance 20 years ago still have better performance today, while those with worse performance didn’t see much improvement.

    This country-by-country difference could be driven by regulation and permitting processes, cultural factors, or by market dynamics such as how firms interact with each other, Trancik says.

    “But not all soft technology variables are ones that you would want to change in a cost-reducing direction, like lower wages. So, there are other considerations, beyond just bringing the cost of the technology down, that we need to think about when interpreting these results,” she says.

    Their analysis points to two strategies for reducing soft costs. For one, scientists could focus on developing hardware improvements that make soft costs more dependent on hardware technology variables and less on soft technology variables, such as by creating simpler, more standardized equipment that could reduce on-site installation time.

    Or researchers could directly target soft technology features without changing hardware, perhaps by creating more efficient workflows for system installation or automated permitting platforms.

    “In practice, engineers will often pursue both approaches, but separating the two in a formal model makes it easier to target innovation efforts by leveraging specific relationships between technology characteristics and costs,” Klemun says.

    “Often, when we think about information processing, we are leaving out processes that still happen in a very low-tech way through people communicating with one another. But it is just as important to think about that as a technology as it is to design fancy software,” Trancik notes.

    In the future, she and her collaborators want to apply their quantitative model to study the soft costs related to other technologies, such as electrical vehicle charging and nuclear fission. They are also interested in better understanding the limits of soft technology improvement, and how one could design better soft technology from the outset.

    This research is funded by the U.S. Department of Energy Solar Energy Technologies Office. More

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    Megawatt electrical motor designed by MIT engineers could help electrify aviation

    Aviation’s huge carbon footprint could shrink significantly with electrification. To date, however, only small all-electric planes have gotten off the ground. Their electric motors generate hundreds of kilowatts of power. To electrify larger, heavier jets, such as commercial airliners, megawatt-scale motors are required. These would be propelled by hybrid or turbo-electric propulsion systems where an electrical machine is coupled with a gas turbine aero-engine.

    To meet this need, a team of MIT engineers is now creating a 1-megawatt motor that could be a key stepping stone toward electrifying larger aircraft. The team has designed and tested the major components of the motor, and shown through detailed computations that the coupled components can work as a whole to generate one megawatt of power, at a weight and size competitive with current small aero-engines.

    For all-electric applications, the team envisions the motor could be paired with a source of electricity such as a battery or a fuel cell. The motor could then turn the electrical energy into mechanical work to power a plane’s propellers. The electrical machine could also be paired with a traditional turbofan jet engine to run as a hybrid propulsion system, providing electric propulsion during certain phases of a flight.

    “No matter what we use as an energy carrier — batteries, hydrogen, ammonia, or sustainable aviation fuel — independent of all that, megawatt-class motors will be a key enabler for greening aviation,” says Zoltan Spakovszky, the T. Wilson Professor in Aeronautics and the Director of the Gas Turbine Laboratory (GTL) at MIT, who leads the project.

    Spakovszky and members of his team, along with industry collaborators, will present their work at a special session of the American Institute of Aeronautics and Astronautics – Electric Aircraft Technologies Symposium (EATS) at the Aviation conference in June.

    The MIT team is composed of faculty, students, and research staff from GTL and the MIT Laboratory for Electromagnetic and Electronic Systems: Henry Andersen Yuankang Chen, Zachary Cordero, David Cuadrado,  Edward Greitzer, Charlotte Gump, James Kirtley, Jr., Jeffrey Lang, David Otten, David Perreault, and Mohammad Qasim,  along with Marc Amato of Innova-Logic LLC. The project is sponsored by Mitsubishi Heavy Industries (MHI).

    Heavy stuff

    To prevent the worst impacts from human-induced climate change, scientists have determined that global emissions of carbon dioxide must reach net zero by 2050. Meeting this target for aviation, Spakovszky says, will require “step-change achievements” in the design of unconventional aircraft, smart and flexible fuel systems, advanced materials, and safe and efficient electrified propulsion. Multiple aerospace companies are focused on electrified propulsion and the design of megawatt-scale electric machines that are powerful and light enough to propel passenger aircraft.

    “There is no silver bullet to make this happen, and the devil is in the details,” Spakovszky says. “This is hard engineering, in terms of co-optimizing individual components and making them compatible with each other while maximizing overall performance. To do this means we have to push the boundaries in materials, manufacturing, thermal management, structures and rotordynamics, and power electronics”

    Broadly speaking, an electric motor uses electromagnetic force to generate motion. Electric motors, such as those that power the fan in your laptop, use electrical energy — from a battery or power supply — to generate a magnetic field, typically through copper coils. In response, a magnet, set near the coils, then spins in the direction of the generated field and can then drive a fan or propeller.

    Electric machines have been around for over 150 years, with the understanding that, the bigger the appliance or vehicle, the larger the copper coils  and the magnetic rotor, making the machine heavier. The more power the electrical machine generates, the more heat it produces, which requires additional elements to keep the components cool — all of which can take up space and add significant weight to the system, making it challenging for airplane applications.

    “Heavy stuff doesn’t go on airplanes,” Spakovszky says. “So we had to come up with a compact, lightweight, and powerful architecture.”

    Good trajectory

    As designed, the MIT electric motor and power electronics are each about the size of a checked suitcase weighing less than an adult passenger.

    The motor’s main components are: a high-speed rotor, lined with an array of magnets with varying orientation of polarity; a compact low-loss stator that fits inside the rotor and contains an intricate array of copper windings; an advanced heat exchanger that keeps the components cool while transmitting the torque of the machine; and a distributed power electronics system, made from 30 custom-built circuit boards, that precisely change the currents running through each of the stator’s copper windings, at high frequency.

    “I believe this is the first truly co-optimized integrated design,” Spakovszky says. “Which means we did a very extensive design space exploration where all considerations from thermal management, to rotor dynamics, to power electronics and electrical machine architecture were assessed in an integrated way to find out what is the best possible combination to get the required specific power at one megawatt.”

    As a whole system, the motor is designed such that the distributed circuit boards are close coupled with the electrical machine to minimize transmission loss and to allow effective air cooling through the integrated heat exchanger.

    “This is a high-speed machine, and to keep it rotating while creating torque, the magnetic fields have to be traveling very quickly, which we can do through our circuit boards switching at high frequency,” Spakovszky says.

    To mitigate risk, the team has built and tested each of the major components individually, and shown that they can operate as designed and at conditions exceeding normal operational demands. The researchers plan to assemble the first fully working electric motor, and start testing it in the fall.

    “The electrification of aircraft has been on a steady rise,” says Phillip Ansell, director of the Center for Sustainable Aviation at the University of Illinois Urbana-Champaign, who was not involved in the project. “This group’s design uses a wonderful combination of conventional and cutting-edge methods for electric machine development, allowing it to offer both robustness and efficiency to meet the practical needs of aircraft of the future.”

    Once the MIT team can demonstrate the electric motor as a whole, they say the design could power regional aircraft and could also be a companion to conventional jet engines, to enable hybrid-electric propulsion systems. The team also envision that multiple one-megawatt motors could power multiple fans distributed along the wing on future aircraft configurations. Looking ahead, the foundations of the one-megawatt electrical machine design could potentially be scaled up to multi-megawatt motors, to power larger passenger planes.

    “I think we’re on a good trajectory,” says Spakovszky, whose group and research have focused on more than just gas turbines. “We are not electrical engineers by training, but addressing the 2050 climate grand challenge is of utmost importance; working with electrical engineering faculty, staff and students for this goal can draw on MIT’s breadth of technologies so the whole is greater than the sum of the parts. So we are reinventing ourselves in new areas. And MIT gives you the opportunity to do that.” More

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    Understanding boiling to help the nuclear industry and space missions

    To launch extended missions in space, the National Aeronautics and Space Administration (NASA) is borrowing a page from the nuclear engineering industry: It is trying to understand how boiling works.

    Planning for long-term missions has NASA researching ways of packing the least amount of cryogenic fuel possible for efficient liftoff. One potential solution is to refuel the rocket in space using fuel depots placed in low Earth orbits. This way, the spacecraft can carry the lightest fuel load — enough to reach the low Earth orbit to refuel as necessary and complete the mission. But refueling in space requires a thorough knowledge of cryogenic fuels.

    “We [need to understand] how boiling of cryogens behaves in microgravity conditions [encountered in space],” says Florian Chavagnat, a sixth-year doctoral candidate in the Department of Nuclear Science and Engineering (NSE). After all, understanding how cryogens boil in space is critical to NASA’s fuel management strategy. The vast majority of studies on boiling evaluate fluids that boil at high temperatures, which doesn’t necessarily apply to cryogens. Under the advisement of Matteo Bucci and Emilio Baglietto, Chavagnat is working on NASA-sponsored research about cryogens and the way the lack of buoyancy in space affects boiling.

    A childhood spent tinkering

    A deep understanding of engineering and physical phenomena is exactly what Chavagnat developed growing up in Boussy-Saint-Antoine, a suburb of Paris, with parents who worked for SNCF, the national state-owned rail company. Chavagnat remembers discussing the working of trains and motors with his engineer dad and building a variety of balsa-wood models. One of his memorable projects was a sailboat propelled by a motor from an electric toothbrush.

    By the time he was a teenager, Chavagnat received a metal lathe as a gift. His tinkering became an obsession; a compressed air engine was a favorite project. Soon his parents’ small shed, meant for gardening, became a factory, Chavagnat recalls, laughing.

    A lifelong love of math and physics propelled a path to the National Institute of Applied Science in Rouen, Normandy, where Chavagnat studied energetics and propulsion as part of a five-year engineering program. In his final year, Chavagnat studied atomic engineering from INSTN Paris-Saclay, part of the esteemed French Alternative Energies and Atomic Energy Commission (CEA).

    The final year of studies at CEA required a six-month-long internship, which traditionally sets the course for a job. Chavagnat decided to take a chance and apply for an internship at MIT NSE instead, knowing his future course might be uncertain. “I didn’t take a lot of risk in my life, but this one was a big risk,” Chavagnat says. The gamble paid off: Chavagnat won the internship with Charles Forsberg, which paved the way for his admission as a doctoral student. “I selected MIT because it has always been my dream school,” Chavagnat says. He also enjoyed the idea of challenging himself to improve his English-speaking skills.

    A love of physics and heat transfer

    Chavagnat loves physics — “if I can study any problem in physics, I’d be happy” he says — which led him to working on heat transfer, more specifically on boiling heat transfer. His early doctoral research focused on transient boiling in nuclear reactors, part of which has been published in the International Journal of Heat and Mass Transfer.

    Chavagnat’s research targets a specific kind of nuclear reactor called a material test reactor (MTR). Nuclear scientists use MTRs to understand how materials used in plant operations might behave under long-term use. Densely packed nuclear fuel, running at high power, simulates long-term effects using a very intense neutron flux.

    To prevent failure, operators limit reactor temperature by flowing very cold water at high velocity. When reactor heat power increases uncontrollably, the piped water begins to boil. Boiling works to prevent meltdown by altering neutron moderation and extracting heat from the fuel. “[Unfortunately], that only works until you reach a certain heat flux at the fuel cladding, after which the efficiency completely drops,” Chavagnat says. Once the critical heat flux is reached, water vapor starts to blanket and insulate the fuel elements, leading to rapidly rising cladding temperatures and potential burnout.

    The key is to figure out the behavior of maximum boiling heat flux under routine MTR conditions — cold water, high flow velocity, and narrow spacing between the fuel elements.

    Study of cryogenic boiling

    Boiling continues to occupy center stage as Chavagnat pursues the question for NASA. Cryogens boil at very low temperatures, so the question of how to prevent fuel loss from routine space-based operations is an important one to answer.

    Chavagnat is studying how boiling would behave under reduced or absent buoyancy, which are the conditions cryogenic rocket fuel will encounter in space.

    To reproduce space-like conditions on Earth, buoyancy can be modified without going to space. Chavagnat is manipulating the inclination of the boiling surface — placing it upside down is an example — such that buoyancy does not do what it usually does: help bubbles break away from the surface. He is also performing boiling experiments in parabolic flights to simulate microgravity, similar to what is experienced aboard the International Space Station.

    Chavagnat designed and built equipment which can perform both methods with minimum changes. “We observed nitrogen boiling on our surface by imaging it using two high-speed video cameras,” he says. The experiment was approved to go on board the parabolic flights operated by Zero-G, a company that operates weightless flights. The team successfully completed four parabolic flights in 2022.

    “Flying an experiment aboard an aircraft and operating it in microgravity is an incredible experience, but is challenging,” Chavagnat says, “Knowing the details the experiment is a must, but other skills are quite useful — in particular, working as a team, being able to manage high stress levels, and being able to work while being motion-sick.” Another challenge is that the majority of issues cannot be fixed once aboard, as aircraft pilots perform the parabola (each lasting 17 seconds) almost back-to-back.

    Throughout his research at MIT, Chavagnat has been captivated by how complex a simple phenomenon like boiling can truly be. “In your childhood, you have a certain idea of how boiling looks, relatively slow bubbles that you can see with the naked eye,” he says, “but you don’t realize the complexity until you see it with your own eyes.”

    In his infrequent spare time, Chavagnat plays soccer with the NSE’s team, the Atom Smashers. The group meets only five times a semester so it’s a low-key commitment, says Chavagnat who spends most of his time at the lab. “I am doing mostly experiments at MIT; it turns out the skills I learned in my shed when I was 15 are actually quite useful here,” he laughs. More

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    The answer may be blowing in the wind

    Capturing energy from the winds gusting off the coasts of the United States could more than double the nation’s electricity generation. It’s no wonder the Biden administration views this immense, clean-energy resource as central to its ambitious climate goals of 100 percent carbon-emissions-free electricity by 2035 and a net-zero emissions economy by 2050. The White House is aiming for 30 gigawatts of offshore wind by 2030 — enough to power 10 million homes.

    At the MIT Energy Initiative’s Spring Symposium, academic experts, energy analysts, wind developers, government officials, and utility representatives explored the immense opportunities and formidable challenges of tapping this titanic resource, both in the United States and elsewhere in the world.

    “There’s a lot of work to do to figure out how to use this resource economically — and sooner rather than later,” said Robert C. Armstrong, MITEI director and the Chevron Professor of Chemical Engineering, in his introduction to the event. 

    In sessions devoted to technology, deployment and integration, policy, and regulation, participants framed the issues critical to the development of offshore wind, described threats to its rapid rollout, and offered potential paths for breaking through gridlock.

    R&D advances

    Moderating a panel on MIT research that is moving the industry forward, Robert Stoner, MITEI’s deputy director for science and technology, provided context for the audience about the industry.

    “We have a high degree of geographic coincidence between where that wind capacity is and where most of us are, and it’s complementary to solar,” he said. Turbines sited in deeper, offshore waters gain the advantage of higher-velocity winds. “You can make these machines huge, creating substantial economies of scale,” said Stoner. An onshore turbine generates approximately 3 megawatts; offshore structures can each produce 15 to 17 megawatts, with blades the length of a football field and heights greater than the Washington Monument.

    To harness the power of wind farms spread over hundreds of nautical miles in deep water, Stoner said, researchers must first address some serious issues, including building and maintaining these massive rigs in harsh environments, laying out wind farms to optimize generation, and creating reliable and socially acceptable connections to the onshore grid. MIT scientists described how they are tackling a number of these problems.

    “When you design a floating structure, you have to prepare for the worst possible conditions,” said Paul Sclavounos, a professor of mechanical engineering and naval architecture who is developing turbines that can withstand severe storms that batter turbine blades and towers with thousands of tons of wind force. Sclavounos described systems used in the oil industry for tethering giant, buoyant rigs to the ocean floor that could be adapted for wind platforms. Relatively inexpensive components such as polyester mooring lines and composite materials “can mitigate the impact of high waves and big, big wind loads.”

    To extract the maximum power from individual turbines, developers must take into account the aerodynamics among turbines in a single wind farm and between adjacent wind farms, according to Michael Howland, the Esther and Harold E. Edgerton Assistant Professor of Civil and Environmental Engineering. Howland’s work modeling turbulence in the atmosphere and wind speeds has demonstrated that angling turbines by just a small amount relative to each other can increase power production significantly for offshore installations, dramatically improving their efficiencies. Howland hopes his research will promote “changing the design of wind farms from the beginning of the process.”

    There’s a staggering complexity to integrating electricity from offshore wind into regional grids such as the one operated by ISO New England, whether converting voltages or monitoring utility load. Steven B. Leeb, a professor of electrical engineering and computer science and of mechanical engineering, is developing sensors that can indicate electronic failures in a micro grid connected to a wind farm. And Marija Ilić, a joint adjunct professor in the Department of Electrical Engineering and Computer Science and a senior research scientist at the Laboratory for Information and Decision Systems, is developing software that would enable real-time scheduling of controllable equipment to compensate for the variable power generated by wind and other variable renewable resources. She is also working on adaptive distributed automation of this equipment to ensure a stable electric power grid.

    “How do we get from here to there?”

    Symposium speakers provided snapshots of the emerging offshore industry, sharing their sense of urgency as well as some frustrations.

    Climate poses “an existential crisis” that calls for “a massive war-footing undertaking,” said Melissa Hoffer, who occupies the newly created cabinet position of climate chief for the Commonwealth of Massachusetts. She views wind power “as the backbone of electric sector decarbonization.” With the Vineyard Wind project, the state will be one of the first in the nation to add offshore wind to the grid. “We are actually going to see the first 400 megawatts … likely interconnected and coming online by the end of this year, which is a fantastic milestone for us,” said Hoffer.

    The journey to completing Vineyard Wind involved a plethora of painstaking environmental reviews, lawsuits over lease siting, negotiations over the price of the electricity it will produce, buy-in from towns where its underground cable comes ashore, and travels to an Eversource substation. It’s a familiar story to Alla Weinstein, founder and CEO of Trident Winds, Inc. On the West Coast, where deep waters (greater than 60 meters) begin closer to shore, Weinstein is trying to launch floating offshore wind projects. “I’ve been in marine renewables for 20 years, and when people ask why I do what I do, I tell them it’s because it matters,” she said. “Because if we don’t do it, we may not have a planet that’s suitable for humans.”

    Weinstein’s “picture of reality” describes a multiyear process during which Trident Winds must address the concerns of such stakeholders as tribal communities and the fishing industry and ensure compliance with, among other regulations, the Marine Mammal Protection Act and the Migratory Bird Species Act. Construction of these massive floating platforms, when it finally happens, will require as-yet unbuilt specialized port infrastructure and boats, and a large skilled labor force for assembly and transmission. “This is a once-in-a-lifetime opportunity to create a new industry,” she said, but “how do we get from here to there?”

    Danielle Jensen, technical manager for Shell’s Offshore Wind Americas, is working on a project off of Rhode Island. The blueprint calls for high-voltage, direct-current cable snaking to landfall in Massachusetts, where direct-current lines switch to alternating current to connect to the grid. “None of this exists, so we have to find a space, the lands, and the right types of cables, tie into the interconnection point, and work with interconnection operators to do that safely and reliably,” she said.

    Utilities are partnering with developers to begin clearing some of these obstacles. Julia Bovey, director of offshore wind for Eversource, described her firm’s redevelopment or improvement of five ports, and new transport vessels for offshore assembly of wind farm components in Atlantic waters. The utility is also digging under roads to lay cables for new power lines. Bovey notes that snags in supply chains and inflation have been driving up costs. This makes determining future electricity rates more complex, especially since utility contracts and markets work differently in each state.

    Just seven up

    Other nations hold a commanding lead in offshore wind: To date, the United States claims just seven operating turbines, while Denmark boasts 6,200 and the U.K. 2,600. Europe’s combined offshore power capacity stands at 30 gigawatts — which, as MITEI Research Scientist Tim Schittekatte notes, is the U.S. goal for 2030.

    The European Union wants 400 gigawatts of offshore wind by 2050, a target made all the more urgent by threats to Europe’s energy security from the war in Ukraine. “The idea is to connect all those windmills, creating a mesh offshore grid,” Schittekatte said, aided by E.U. regulations that establish “a harmonized process to build cross-border infrastructure.”

    Morten Pindstrup, the international chief engineer at Energinet, Denmark’s state-owned energy enterprise, described one component of this pan-European plan: a hybrid Danish-German offshore wind network. Energinet is also constructing energy islands in the North Sea and the Baltic to pool power from offshore wind farms and feed power to different countries.

    The European wind industry benefits from centralized planning, regulation, and markets, said Johannes P. Pfeifenberger, a principal of The Brattle Group. “The grid planning process in the U.S. is not suitable today to find cost-effective solutions to get us to a clean energy grid in time,” he said. Pfeifenberger recommended that the United States immediately pursue a series of moves including a multistate agreement for cooperating on offshore wind and establishment by grid operators of compatible transmission technologies.

    Symposium speakers expressed sharp concerns that complicated and prolonged approvals, as well as partisan politics, could hobble the nation’s nascent offshore industry. “You can develop whatever you want and agree on what you’re doing, and then the people in charge change, and everything falls apart,” said Weinstein. “We can’t slow down, and we actually need to accelerate.”

    Larry Susskind, the Ford Professor of Urban and Environmental Planning, had ideas for breaking through permitting and political gridlock. A negotiations expert, he suggested convening confidential meetings for stakeholders with competing interests for collaborative problem-solving sessions. He announced the creation of a Renewable Energy Facility Siting Clinic at MIT. “We get people to agree that there is a problem, and to accept that without a solution, the system won’t work in the future, and we have to start fixing it now.”

    Other symposium participants were more sanguine about the success of offshore wind. “Trust me, floating wind is not a pie-in-the-sky, exotic technology that is difficult to implement,” said Sclavounos. “There will be companies investing in this technology because it produces huge amounts of energy, and even though the process may not be streamlined, the economics will work itself out.” More

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    Exploring new sides of climate and sustainability research

    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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    Engineers solve a mystery on the path to smaller, lighter batteries

    A discovery by MIT researchers could finally unlock the door to the design of a new kind of rechargeable lithium battery that is more lightweight, compact, and safe than current versions, and that has been pursued by labs around the world for years.

    The key to this potential leap in battery technology is replacing the liquid electrolyte that sits between the positive and negative electrodes with a much thinner, lighter layer of solid ceramic material, and replacing one of the electrodes with solid lithium metal. This would greatly reduce the overall size and weight of the battery and remove the safety risk associated with liquid electrolytes, which are flammable. But that quest has been beset with one big problem: dendrites.

    Dendrites, whose name comes from the Latin for branches, are projections of metal that can build up on the lithium surface and penetrate into the solid electrolyte, eventually crossing from one electrode to the other and shorting out the battery cell. Researchers haven’t been able to agree on what gives rise to these metal filaments, nor has there been much progress on how to prevent them and thus make lightweight solid-state batteries a practical option.

    The new research, being published today in the journal Joule in a paper by MIT Professor Yet-Ming Chiang, graduate student Cole Fincher, and five others at MIT and Brown University, seems to resolve the question of what causes dendrite formation. It also shows how dendrites can be prevented from crossing through the electrolyte.

    Chiang says in the group’s earlier work, they made a “surprising and unexpected” finding, which was that the hard, solid electrolyte material used for a solid-state battery can be penetrated by lithium, which is a very soft metal, during the process of charging and discharging the battery, as ions of lithium move between the two sides.

    This shuttling back and forth of ions causes the volume of the electrodes to change. That inevitably causes stresses in the solid electrolyte, which has to remain fully in contact with both of the electrodes that it is sandwiched between. “To deposit this metal, there has to be an expansion of the volume because you’re adding new mass,” Chiang says. “So, there’s an increase in volume on the side of the cell where the lithium is being deposited. And if there are even microscopic flaws present, this will generate a pressure on those flaws that can cause cracking.”

    Those stresses, the team has now shown, cause the cracks that allow dendrites to form. The solution to the problem turns out to be more stress, applied in just the right direction and with the right amount of force.

    While previously, some researchers thought that dendrites formed by a purely electrochemical process, rather than a mechanical one, the team’s experiments demonstrate that it is mechanical stresses that cause the problem.

    The process of dendrite formation normally takes place deep within the opaque materials of the battery cell and cannot be observed directly, so Fincher developed a way of making thin cells using a transparent electrolyte, allowing the whole process to be directly seen and recorded. “You can see what happens when you put a compression on the system, and you can see whether or not the dendrites behave in a way that’s commensurate with a corrosion process or a fracture process,” he says.

    The team demonstrated that they could directly manipulate the growth of dendrites simply by applying and releasing pressure, causing the dendrites to zig and zag in perfect alignment with the direction of the force.

    Applying mechanical stresses to the solid electrolyte doesn’t eliminate the formation of dendrites, but it does control the direction of their growth. This means they can be directed to remain parallel to the two electrodes and prevented from ever crossing to the other side, and thus rendered harmless.

    In their tests, the researchers used pressure induced by bending the material, which was formed into a beam with a weight at one end. But they say that in practice, there could be many different ways of producing the needed stress. For example, the electrolyte could be made with two layers of material that have different amounts of thermal expansion, so that there is an inherent bending of the material, as is done in some thermostats.

    Another approach would be to “dope” the material with atoms that would become embedded in it, distorting it and leaving it in a permanently stressed state. This is the same method used to produce the super-hard glass used in the screens of smart phones and tablets, Chiang explains. And the amount of pressure needed is not extreme: The experiments showed that pressures of 150 to 200 megapascals were sufficient to stop the dendrites from crossing the electrolyte.

    The required pressure is “commensurate with stresses that are commonly induced in commercial film growth processes and many other manufacturing processes,” so should not be difficult to implement in practice, Fincher adds.

    In fact, a different kind of stress, called stack pressure, is often applied to battery cells, by essentially squishing the material in the direction perpendicular to the battery’s plates — somewhat like compressing a sandwich by putting a weight on top of it. It was thought that this might help prevent the layers from separating. But the experiments have now demonstrated that pressure in that direction actually exacerbates dendrite formation. “We showed that this type of stack pressure actually accelerates dendrite-induced failure,” Fincher says.

    What is needed instead is pressure along the plane of the plates, as if the sandwich were being squeezed from the sides. “What we have shown in this work is that when you apply a compressive force you can force the dendrites to travel in the direction of the compression,” Fincher says, and if that direction is along the plane of the plates, the dendrites “will never get to the other side.”

    That could finally make it practical to produce batteries using solid electrolyte and metallic lithium electrodes. Not only would these pack more energy into a given volume and weight, but they would eliminate the need for liquid electrolytes, which are flammable materials.

    Having demonstrated the basic principles involved, the team’s next step will be to try to apply these to the creation of a functional prototype battery, Chiang says, and then to figure out exactly what manufacturing processes would be needed to produce such batteries in quantity. Though they have filed for a patent, the researchers don’t plan to commercialize the system themselves, he says, as there are already companies working on the development of solid-state batteries. “I would say this is an understanding of failure modes in solid-state batteries that we believe the industry needs to be aware of and try to use in designing better products,” he says.

    The research team included Christos Athanasiou and Brian Sheldon at Brown University, and Colin Gilgenbach, Michael Wang, and W. Craig Carter at MIT. The work was supported by the U.S. National Science Foundation, the U.S. Department of Defense, the U.S. Defense Advanced Research Projects Agency, and the U.S. Department of Energy. More