Evelyn Reynolds

As researchers push the boundaries of battery design, seeking to pack ever greater amounts of power and energy into a given amount of space or weight, one of the more promising technologies being studied is lithium-ion batteries that use a solid electrolyte material between the two electrodes, rather than the typical liquid.

But such batteries have been plagued by a tendency for branch-like projections of metal called dendrites to form on one of the electrodes, eventually bridging the electrolyte and shorting out the battery cell. Now, researchers at MIT and elsewhere have found a way to prevent such dendrite formation, potentially unleashing the potential of this new type of high-powered battery.

The findings are described in the journal Nature Energy, in a paper by MIT graduate student Richard Park, professors Yet-Ming Chiang and Craig Carter, and seven others at MIT, Texas A&M University, Brown University, and Carnegie Mellon University.

Solid-state batteries, Chiang explains, have been a long-sought technology for two reasons: safety and energy density. But, he says, “the only way you can reach the energy densities that are interesting is if you use a metal electrode.” And while it’s possible to couple that metal electrode with a liquid electrolyte and still get good energy density, that does not provide the same safety advantage as a solid electrolyte does, he says.

Solid state batteries only make sense with metal electrodes, he says, but attempts to develop such batteries have been hampered by the growth of dendrites, which eventually bridge the gap between the two electrode plates and short out the circuit, weakening or inactivating that cell in a battery.

It’s been known that dendrites form more rapidly when the current flow is higher — which is generally desirable in order to allow rapid charging. So far, the current densities that have been achieved in experimental solid-state batteries have been far short of what would be needed for a practical commercial rechargeable battery. But the promise is worth pursuing, Chiang says, because the amount of energy that can be stored in experimental versions of such cells, is already nearly double that of conventional lithium-ion batteries.

The team solved the dendrite problem by adopting a compromise between solid and liquid states. They made a semisolid electrode, in contact with a solid electrolyte material. The semisolid electrode provided a kind of self-healing surface at the interface, rather than the brittle surface of a solid that could lead to tiny cracks that provide the initial seeds for dendrite formation.

The idea was inspired by experimental high-temperature batteries, in which one or both electrodes consist of molten metal. According to Park, the first author of the paper, the hundreds-of-degrees temperatures of molten-metal batteries would never be practical for a portable device, but the work did demonstrate that a liquid interface can enable high current densities with no dendrite formation. “The motivation here was to develop electrodes that are based on carefully selected alloys in order to introduce a liquid phase that can serve as a self-healing component of the metal electrode,” Park says.

The material is more solid than liquid, he explains, but resembles the amalgam dentists use to fill a cavity — solid metal, but still able to flow and be shaped. At the ordinary temperatures that the battery operates in, “it stays in a regime where you have both a solid phase and a liquid phase,” in this case made of a mixture of sodium and potassium. The team demonstrated that it was possible to run the system at 20 times greater current than using solid lithium, without forming any dendrites, Chiang says. The next step was to replicate that performance with an actual lithium-containing electrode.

In a second version of their solid battery, the team introduced a very thin layer of liquid sodium potassium alloy in between a solid lithium electrode and a solid electrolyte. They showed that this approach could also overcome the dendrite problem, providing an alternative approach for further research.

The new approaches, Chiang says, could easily be adapted to many different versions of solid-state lithium batteries that are being investigated by researchers around the world. He says the team’s next step will be to demonstrate this system’s applicability to a variety of battery architectures. Co-author Viswanathan, professor of mechanical engineering at Carnegie Mellon University, says, “We think we can translate this approach to really any solid-state lithium-ion battery. We think it could be used immediately in cell development for a wide range of applications, from handheld devices to electric vehicles to electric aviation.”

“Metal penetration through solid electrolyte separators is a key challenge facing high energy-density batteries, and to date much attention has been directed toward the properties of the separator material through which the metal penetrates,” says Paul Albertus, an associate professor of chemical and biomolecular engineering at the University of Maryland, who was not associated with this research. Noting that the new work focuses instead on the properties of the metal electrode itself, he says the research “is important for both setting scientific priorities for understanding metal penetration, as well as developing innovations to help mitigate this important failure mode.”

The team also included Christopher Eschler, Cole Fincher, and Andres Badel at MIT; Pinwen Guan at Carnegie Mellon University; and Brian Sheldon at Brown University. The work was supported by the U.S. Department of Energy, the National Science Foundation, and the MIT-Skoltech Next Generation Program. More

“I had always expected I’d stay at MIT for the four years, get my undergraduate degree at the end and probably return to the UK.”

Richard Ibekwe recalls his early assumptions about his academic path at MIT. Now he is a nuclear science and engineering (NSE) PhD candidate working at the Plasma Science and Fusion Center (PSFC), dedicated to long-term fusion research at MIT, focusing on magnet technology. Recipient of multiple undergraduate awards, Ibekwe has earned graduate-level support from the MIT Energy Initiative, which has enlisted him as an MIT Energy Fellow, sponsored by Commonwealth Fusion Systems. He is also the current president of the MIT student chapter of the American Nuclear Society (ANS).                                                              

“Three things that have always fascinated me,” he says, “have been learning how things work, finding how to fix them, and using that knowledge to serve and care for those around me. Growing up, that manifested in building and tinkering with things — first toys, and then DIY around the house. Now I see fusion fitting into that interest: There are few problems as hard to solve or that might have as profound a potential positive impact on our planet and the whole of humanity.”

Fusion, the reaction that fuels the sun and other stars, is a potentially endless source of carbon-free energy on Earth, if it can only be harnessed. Much research has favored heating hydrogen fuel inside a donut-shaped device called a tokamak, creating plasma that is hot and dense enough for fusion to occur. Because plasma will follow magnetic field lines, these devices are wrapped with magnets to keep the hot fuel from damaging the chamber walls.

Ibekwe’s interest in fusion developed only in his senior year, after taking an introductory design class from NSE Assistant Professor Zachary Hartwig.

“As an undergrad, from a distance, fusion seemed a very esoteric, very physics-heavy endeavor. My background was much more engineering-focused,” he says. “I was inspired by Zach’s teaching, and by the way he fused the science and engineering of fusion research.”

When Ibekwe applied to join Hartwig’s team as a PhD student he was not aware of the future that was taking shape at the PSFC. A tokamak called SPARC was being designed using a new high-temperature superconductor (HTS), a tape allowing larger electric currents and higher magnetic fields than traditional superconducting coils: It suggested a path to a smaller, less-expensive fusion power plant that could be built more quickly than currently funded international projects.

“I just thought that fusion would be a cool subject to get involved with,” says Ibekwe. “It was a happy surprise to discover SPARC was in the works.”

Because so much of SPARC’s success depends on the new superconducting technology, it is not surprising that Ibekwe and his colleagues are researching it. Because high-temperature superconductors can handle greater magnetic fields than regular superconductors, they are ideal for tokamaks. 

“It turns out that almost everything about the fusion process gets much better and more favorable when you increase the magnetic field,” Ibekwe says. But he wonders what might negatively impact this process. How might flaws in the HTS tapes affect tokamak performance?

As they fabricate magnets with these thin HTS tapes, Ibekwe and his colleagues ask one key question: What is the critical current? What is the maximum current the tapes can carry before they cease to be superconducting, losing the features that make them central to a tokamak’s success, like their ability to conduct large electric currents with no electrical resistance?

“When producing these tapes — these thin, ribbon-shaped wires — the goal is to make them as high-quality as possible so that the maximum current is high and uniform throughout the wire’s length. It turns out that when manufacturing these tapes, because perhaps it gets dented, or a speck of dust falls on the tape when growing the crystal, it results in regions where the critical current is much lower. We call those dropouts.”

The critical current drops out at those locations, and the superconductor experiences electrical resistance. The area heats up, producing a situation where the heat expands, causing the entire cable to lose conductivity. To make the best of this situation, engineers can try to cut out any defects in the tape and use a shorter length, or they can produce a new length of tape to get what they want. But this corrective process can be expensive and time-consuming.

Ibekwe is embracing the imperfections, doing a deep dive into HTS tape flaws in an attempt to offer pragmatic solutions. 

“First,” he says, “let’s measure and understand the effect of these defects on the performance of the superconducting tapes, which hasn’t really been done before in detail. Second, we need to figure out quantitatively how bad a defect we can withstand. Thirdly, how can we create magnets that contain defects in such a way that we can still make usable, efficient magnets?”

Ibekwe believes he may have inherited his pragmatic approach from his parents, who had moved from Nigeria to study in London before Richard was born. His mother completed her PhD in child nutrition while he was growing up. 

“I think I got the academic influence from her,” he says. “My father is a building contractor. There’s the element of the practical aspect in me from him.”

Ibekwe’s preliminary research suggests the HTS tape magnets he’s been working on are intrinsically more tolerant to the presence of defects than low-temperature superconductors.

“The challenge,” he says, “is to come up with a design guide that will show engineers building these magnets what’s acceptable and what’s not.”

Ibekwe wants to continue working on the challenging problems in fusion and related fields, taking a holistic approach that is inspired in part by his leadership in ANS, which this year provided opportunities to address issues related to health, isolation, diversity, equity, and inclusion. He foresees an academic career as a good way to achieve this goal.

“I want to wrestle not only with the scientific and engineering questions, but also with the societal and political, the philosophical and ethical questions,” he says. “I think the university is the best place to do that.” More

Before you scramble to clean your room or attempt to make your pajamas look a bit less like pajamas, here is a good excuse to keep your video off during your next virtual meeting: reducing your environmental impact. New research shows that if you turn your camera off during a videoconference, you can reduce your environmental footprint in that meeting by 96 percent.
Conducted by a team from MIT, Purdue University, and Yale University, the study uncovers the impacts that internet use has on the environment. This is especially significant considering that many countries have reported at least a 20 percent increase in internet use since March 2020 due to the Covid-19 lockdowns.
While the shift to a more digital world has made an impressive dent in global emissions overall — thanks in large part to the likely temporary emissions reductions associated with travel — the impact of our increasingly virtual lifestyles should not be overlooked.
“The goal of this paper is to raise awareness,” says Maryam Arbabzadeh, a postdoc at the MIT Energy Initiative and a co-author of the study. “It is great that we are reducing emissions in some sectors; but at the same time, using the internet also has an environmental impact contributing to the aggregate. The electricity used to power the internet, with its associated carbon, water, and land footprints, isn’t the only thing impacting the environment; the transmission and storage of data also requires water to cool the systems within them.”
One hour of streaming or videoconferencing can emit between 150 and 1,000 grams of carbon dioxide, depending on the service. By comparison, a car produces about 8,887 grams from burning one gallon of gasoline. That hour also requires 2-12 liters of water and a land area about the size of an iPad Mini. Those hours add up in our daily lives with all the time we’re spending on video — and so does the associated environmental footprint.
According to the researchers, if remote work continues through the end of 2021, the global carbon footprint could grow by 34.3 million tons in greenhouse gas emissions. To give a sense of the scale: This increase in emissions would require a forest twice the size of Portugal to fully sequester it all. Meanwhile, the associated water footprint would be enough to fill more than 300,000 Olympic-sized swimming pools, and the land footprint would be equal to roughly the size of Los Angeles.
To store and transmit all of the data powering the internet, data centers consume enough electricity to account for 1 percent of global energy demand — which is more than the total consumption for many countries. Even before the pandemic, the internet’s carbon footprint had been increasing and accounted for about 3.7 percent of global greenhouse gas emissions.
While there have been studies evaluating the carbon footprint of internet data transmission, storage, and use, the associated water and land footprints have been largely overlooked. To address this gap, the researchers in this study analyze the three major environmental footprints — water, land, and carbon — as they pertain to internet use and infrastructure, providing a more holistic look at environmental impact. Their findings are published in Resources, Conservation and Recycling.
Using publicly available data, the researchers give a rough estimate of the carbon, water, and land footprints associated with each gigabyte of data used in common online apps such as Netflix, Instagram, TikTok, Zoom, and 14 other platforms, as well as general web surfing and online gaming. They find that the more video used, the higher the footprints.
A common streaming service, like Netflix or Hulu, requires 7 gigabytes per hour of high-quality video streaming, translating to an average of 441 g CO2e (grams per carbon dioxide equivalent) per hour. If someone is streaming for four hours a day at this quality for a month, the emissions rise to 53 kg CO2e. However, if that person were to instead stream in standard definition, the monthly footprint would only be 2.5 kg CO2e. That decision would save emissions equivalent to driving a car from Baltimore, Maryland to Philadelphia, Pennsylvania, about 93 miles.
Now multiply these savings across 70 million users all streaming in standard definition rather than high definition. That behavioral change would result in a decrease of 3.5 million tons of CO2e — equating to the elimination of 1.7 million tons of coal, which is about 6% of the total monthly consumption of coal in the United States.
“Banking systems tell you the positive environmental impact of going paperless, but no one tells you the benefit of turning off your camera or reducing your streaming quality. So, without your consent, these platforms are increasing your environmental footprint,” says Kaveh Madan, who led and directed this study while a visiting fellow at the Yale MacMillan Center.
While many service providers and data centers have been working to improve operational efficiency and reduce their carbon footprints by diversifying their energy portfolios, measures still need to be taken to reduce the footprint of the product. A streaming service’s video quality is one of the largest determinants of its environmental footprint. Currently, the default for many services is high-definition, putting the onus on the user to reduce the quality of their video in order to improve their footprint. Not many people will be interested in reducing their video quality, especially if the benefits of this action are not well known.
“We need companies to give users the opportunity to make informed, sustainable choices,” says Arbabzadeh. “Companies could change their default actions to lead to less environmental impact, such as setting video quality to standard definition and allowing users to upgrade to high definition. This will also require policymakers to be involved — enacting regulations and requiring transparency about the environmental footprint of digital products to encourage both companies and users to make these changes.”
The researchers also look at specific countries to understand how different energy systems impact the environmental footprints for an average unit of energy used in data processing and transmission. The data show wide variation in carbon, land, and water intensity. In the United States, where natural gas and coal make up the largest share of electricity generation, the carbon footprint is 9 percent higher than the world median, but the water footprint is 45 percent lower and the land footprint is 58 percent lower. Meanwhile, in Brazil, where nearly 70 percent of the electricity comes from hydropower, the median carbon footprint is about 68 percent lower than the world median. The water footprint, on the other hand, is 210 percent higher than the world median, and increasing reliance on hydropower at the expense of fragile rainforest ecosystems has other substantial environmental costs.
“All of these sectors are related to each other,” says Arbabzadeh. “In data centers where electricity comes from a cleaner source, the emissions will be lower; and if it’s coming from fossil fuels, then the impact will be higher.”
“Right now, we have virtual meetings all over, and we’re spending more of our leisure time than ever streaming video content. There is definitely a paradigm shift,” she adds. “With some small behavior changes, like unsubscribing from junk emails or reducing cloud storage, we can have an impact on emissions. It is important that we raise public awareness so that, collectively, we can implement meaningful personal and systemic changes to reduce the internet’s environmental impact and successfully transition to a low-carbon economy.”
The study was supported by the MIT Energy Initiative, Purdue Climate Change Research Center, the Purdue Center for the Environment, and the Yale MacMillan Center. More

Climate action is among the top priorities for the Institute and one that demands global solutions. With Denmark’s reputation as a leader in sustainable thinking, finding a way to bring the two together presented a natural synergy for the MIT-Denmark program. Part of MIT International Science and Technology Initiatives (MISTI), MIT-Denmark connects students and faculty with institutions and industry in Denmark to advance critical research, build new technologies, and create innovative partnerships. Despite the recent challenges due to pandemic-imposed travel restrictions, developing these meaningful international collaborations continues to be a top priority for both MIT students and their counterparts abroad.
The Green Campus Challenge was launched with these goals in mind, tasking student teams to develop proposals to make a more sustainable campus and also broaden their cross-cultural competencies and learn about how sustainability is perceived in another culture.
“We need to work together to make our future more sustainable, and our campuses are the perfect place to start,” says Madeline Smith, program manager for MIT-Denmark. Smith hosted the event alongside the Confederation of Danish Industry (Dansk Industri) with additional collaboration from the MIT Office of Sustainability and the MIT Design for America Club. In the challenge, students ideated solutions and developed plans to make their university campus more sustainable within the areas of architecture/community spaces, energy, and food/waste. They tackled these issues from a global perspective, working in teams that included both MIT and Danish university students.
MIT students joining the challenge came from a variety of class years and majors, from first-year students to PhD candidates, with interests ranging from computer science to civil engineering to urban planning. Danish university students came from top universities across the country, including Aalborg University (AAU), Copenhagen Business School (CBS), the Technical University of Denmark (DTU), University of Copenhagen (KU), and Southern Denmark University (SDU).
Beyond science and technology
Challenge organizers enhanced the experience by providing student teams with mentorship from campus stakeholders, experts in academia and entrepreneurship, and some of Denmark’s most innovative companies. Danfoss advised students on district energy solutions, while mentors from KU and MIT Office of Sustainability provided information about food and waste systems. Other mentors included representatives from Rambøll, SPACE10, Blue Lobster, EcoTree, and DTU Skylab.
“Working on this event was very exciting for us,” says Miha Bobič, vice president of business development and product portfolio at Danfoss, who joined the Green Campus Challenge both as a mentor and on the jury for finalist pitches. “Due to current circumstances, we could not get the experience of face-to-face meetings and mentorship, but students still showed a great deal of engagement and developed innovative ideas, which, if properly developed, could end up as new startups.”
In between mentorship and team brainstorming, there were workshops to help students develop innovative thinking processes, consider project stakeholders, and learn how to pitch their idea to a sustainability-minded audience. Students found time for some fun as well and joined together for MIT and Denmark-themed trivia, yoga, and even a food waste-preventing cooking class organized by Danish startup, Too Good To Go.  
“It was a great experience diving into ideation, collaborating with our international teammates, learning more about their culture and approach to innovation and sustainability,” says Allison Lee, a master of city planning candidate at MIT.
The event culminated with teams presenting their pitches to a panel of judges from the U.S. and Denmark, including Franklin Carrero-Martinez (U.S. National Academy of Sciences, Engineering, and Math), Kinga Christensen (Dansk Industri), Susy Jones (MIT Sustainability), and Tomas Refslund Poulsen (KU Green Campus Initiative), as well as a jury from Danfoss, which selected a winner to recognize within the field of energy innovation.
“It was inspiring to see talented students from MIT and Danish universities pitching their ideas to create sustainable campuses for the future,” says Kinga Christensen, deputy director general for the Confederation of Danish Industry. “By bringing together their skills and perspectives, alongside the mentorship they received from Danish companies and university experts, they were able to develop some truly innovative sustainability proposals.”
Teams find winning solutions
Winning the grand prize was team Green-(In)-Spire, who proposed a campus sustainability world fair. Their plan would include a designated space on campus to showcase technologies and inventions that address campus sustainability through events and “world fairs.” The team members were Allison Lee (MIT), Anna Worning (AAU), Erik Koors (SDU), John Liu (MIT), and Kiara Wahnschafft (MIT).
Team FreeCyclers received runner-up honors for their idea to create a centralized freecycle space. This space would allow students to donate and pick up items too good to throw away, such as books, kitchen equipment, clothing, and more. The team included Eva Smerekanych (MIT), Isabel Dolp (CBS), Niklas Ludvigsen (CBS), Melissa Møller (AAU), and Shristi Rijal (SDU).
For innovations in energy, the Danfoss Prize was awarded to the team UniGreen Farmers for their idea to develop UniGreen Farms, university-led urban rooftop research facilities where interdisciplinary research could take place between senior and entry-level researchers and students. Team members were Brian Li (MIT), Federico D’Ascanio (KU), Frederik Bøllingtoft (AAU), Julia Romero (KU), and Kosmas Subashi (KU).
“This pandemic hasn’t made international collaboration easy,” says Smith. “But seeing students from MIT and Danish universities finish the Green Campus Challenge both eager to make a sustainability impact on their campus community and excited about the international network they’ve developed demonstrates the value of these types of cross-cultural experiences.”
With support from the Danish Industry Foundation and the Confederation of Danish Industry, MIT-Denmark connects MIT students and faculty with institutions and industry in Denmark. MISTI’s global experiential learning programs are made possible through the generosity of individuals, corporations, and foundations. For more information, email misti@mit.edu or contact country program managers directly. MISTI is an experiential program in the Center for International Studies within the School of Humanities, Arts, and Social Sciences. More

The King Climate Action Initiative (K-CAI), a research and policy initiative of MIT’s Abdul Latif Jameel Poverty Action Lab (J-PAL), announced the results of its first competition aimed at identifying and scaling innovative solutions at the intersection of poverty and climate change. K-CAI will fund 10 research studies to generate evidence and four projects that will take evidence-informed approaches to scale. 
Launched in July 2020 in partnership with King Philanthropies, the $25 million initiative is among the first major climate change initiatives focused on generating evidence in real-world settings, and translating that evidence into effective solutions at the nexus of climate change and poverty alleviation worldwide. 
K-CAI’s inaugural competition comes at a pivotal movement in the fight against climate change. The Biden administration recently took executive action to address climate change, including issuing a memorandum to promote evidence-informed decision-making. This action signals a renewed vigor to fight the climate crisis from the United States, and there is hope for greater global cooperation and focus on scientific evidence. 
Without urgent and collective efforts, the effects of climate change will be felt more deeply, particularly by people experiencing extreme poverty. Climate solutions need to not only reduce emissions and pollution, but also address adaption and energy access challenges to protect the most vulnerable populations.
“At King Philanthropies, we aim to improve the lives of the world’s poorest people by supporting high-performing leaders and organizations that are pursuing evidence-based strategies,” says Kim Starkey, president and CEO of King Philanthropies. “Today, climate change is worsening the problem of extreme poverty. We welcome this opportunity to work with the King Climate Action Initiative at J-PAL in identifying and scaling effective solutions that address these two crises simultaneously.”
There is still a critical lack of research on the real-world impacts of climate solutions. Lab-generated evidence can fail to account for human behavior, such as imperfect implementation or low take-up. To ensure the most effective solutions are scaled, investments in real-world evaluations are crucial.  
K-CAI addresses this research need by funding randomized evaluations that will generate rigorous evidence and catalyze the scale-up of effective climate policy and technology solutions. To that end, winners of the first competition are addressing urgent policy priorities across K-CAI’s four main focus areas: climate change mitigation, pollution reduction, adaption, and energy access. 
Climate change mitigation
In order to mitigate the worst effects of climate change, we must significantly reduce global greenhouse gas emissions. The adoption of innovative technologies or increased efficiencies can reduce industrial emission intensity and its harmful effects. One K-CAI-funded study led by Robert Metcalfe, J-PAL affiliate and visiting associate professor in economics at the University of Southern California, is dedicated to reducing greenhouse gas emissions in the shipping industry will evaluate whether changing management practices can increase fuel efficiency in the shipping industry. 
There is also a significant opportunity to reduce emissions through conservation and reduced deforestation. Adapting lessons from a previous randomized evaluation that examined the impacts of paying farmers to reduce deforestation in Uganda, K-CAI is funding a scale-up project led by Seema Jayachandran ’93, J-PAL Gender sector co-chair and professor of economics at Northwestern University; Santiago Izquierdo-Tort, ecological economist at Instituto Tecnológico Autónomo de México; and Santiago Saavedra, assistant professor of economics at Universidad del Rosario that aims to improve the cost-effectiveness of a similar program in Mexico by encouraging participants to enroll more of their eligible land.
Pollution reduction
Local pollutants, such as particulate matter, have harmful effects on health and productivity. Building on evidence from a 2019 randomized evaluation in Gujarat, India, a new project led by Michael Greenstone, J-PAL Energy, Environment, and Climate Change sector co-chair and Milton Friedman Professor of Economics at the University of Chicago; Rohini Pande, J-PAL Political Economy and Governance sector co-chair, professor of economics, and director of the Economic Growth Center at Yale University; Nick Ryan PhD ’12, J-PAL affiliate and assistant professor of economics at Yale University; and Anant Sudarshan, South Asia director at the Energy Policy Institute at the University of Chicago will support regulators in piloting and scaling an emissions trading program to incentivize reducing air pollutants in Punjab and Gujarat. The goal of this effort is to reduce pollution and make it more affordable for businesses to comply with environmental regulations. 
Similarly, K-CAI is funding a study with Douglas Almond, professor of economics and international and public affairs at Columbia University and Shuang Zhang, associate professor of economics at the University of Colorado at Boulder to leverage monitoring systems that provide objective and real-time emissions data to improve environmental inspections in China. The aim of this study is to understand if, when provided with better emissions data, environmental inspectors can improve enforcement and reduce industrial air pollution. 
Climate change adaptation
Climate change is increasing the frequency and severity of extreme weather events, from wildfires to hurricanes to droughts and floods. Increasing resilience to these extreme weather events is critical, especially for low-income communities and countries. 
A new K-CAI-funded study led by Rohini Pande and Maulik Jagnani, assistant professor of economics at the University of Colorado at Denver addresses this challenge through the first randomized evaluation of a flood early warning system in India, which will leverage forecasting and alerting systems, as well as grassroots volunteers trained in community outreach. This will generate insights on how to disseminate time-sensitive forecasts that encourage behavior that protects individuals from flood risks, despite the high initial costs of those behaviors.
Energy access
As economies in low- and middle-income countries grow, so will energy demand. The city of Cape Town, South Africa, is currently facing this challenge and exploring evidence-informed policy solutions.  
Cape Town provides free basic electricity to low-income households and has committed to net carbon neutrality by 2050. The city government must balance equitable growth goals with demand for utilities, but has limited tools at its disposal. A new scale-up project, led by B. Kelsey Jack, J-PAL Energy, Environment, and Climate Change sector co-chair and associate professor of environmental and development economics at the University of California at Santa Barbara, will adapt evidence on targeting to improve the delivery of electricity subsidies to low-income households in Cape Town, building on long-term partnerships between J-PAL Africa, Jack, and the local government. 
Next steps for climate solutions
Funding these projects is a critical first step in developing long-term, evidence-based, and effective climate change solutions focused on both mitigation and adaptation.
“Evidence-informed solutions are critical in the global fight against climate change, and K-CAI’s first round of competition winners demonstrate that it is possible to rigorously evaluate climate policies in real-world settings,” said Iqbal Dhaliwal, global executive director of J-PAL.
These studies and scaling projects utilize an innovative combination of high- and low-tech solutions in order to adapt climate solutions to low- and middle-income country contexts. Not only is this technological innovation key, but their focus on enabling policies is equally important to ensuring solutions are both effective and equitable. K-CAI-funded researchers will work with regulators, companies, and utilities to learn about program effectiveness as they take policy action.
Claire Walsh, project director of K-CAI, notes, “Policy innovation and evaluation, just like technological innovation, is vital for confronting climate change. It can help build the case for policy action and ensure that good technologies achieve their ultimate goals.” 
K-CAI will run two competitions each year to further its mission to identify, generate, and scale cost-effective solutions across its four focus areas. 
To stay up to date with environment, energy, and climate change research and policy, subscribe to J-PAL newsletters and select “Environment & Energy” as an interest area. More

Electricity generated by fusion power plants could play an important role in decarbonizing the U.S. energy sector by mid-century, says a new consensus study report from the National Academies of Sciences, Engineering, and Medicine, which also lays out for the first time a set of technical, economic, and regulatory standards and a timeline for a U.S. fusion pilot plant that would begin producing energy in the 2035-40 time frame.
To achieve this key step toward commercialization, the report calls for an aggressive public-private effort to produce by 2028 a pilot plant design that can, when built, accommodate any of the developmental approaches seeking to realize fusion’s potential as a safe, carbon-free, on-demand energy source.
These include what it calls the “leading fusion concept, a deuterium-tritium fueled tokamak,” like that being pursued at MIT spinout Commonwealth Fusion Systems (CFS) with support from the Institute’s Plasma Science and Fusion Center (PSFC) and Department of Nuclear Science and Engineering. Martin Greenwald, deputy director of the PSFC, notes that “the report can be seen as confirming and validating the vision that motivated the founding of CFS in 2018.” The new report follows and extends a 2018 National Academies study that (while acknowledging the significant scientific and technical challenges still faced by fusion) saw promise in the tokamak approach, called for continued U.S. participation in the international ITER fusion experiment, and suggested a pilot plant effort .
PSFC director and Hitachi America Professor of Engineering Dennis Whyte helped develop the new study as a member of the National Academies’ Committee on the Key Goals and Innovation Needed for a U.S. Fusion Pilot Plant, which also included representatives from other universities, national laboratories, and private companies. It sought out a broad range of expertise from government, academic, and private-sector sources, including U.S. utilities and energy companies.  
“The biggest thing,” says Whyte, is that the diverse group “came to a consensus that fusion is relevant, and that this effort is important.” Driving factors include utility industry commitments to deep cuts in carbon emissions in coming decades, along with a combination of simultaneous synergistic advances in fusion science and technology, application of new resources from areas outside the traditional fusion community, and particularly the rise of interest in private fusion developers like CFS, which collectively have received some $2 billion in funding in recent years.
There has also been a broad pivot by much of the nation’s fusion research community away from a focus on science and toward a mission of practical energy production. This consensus was expressed in a recent report by the Federal Energy Sciences Advisory Committee (FESAC) that urged the nation to “move aggressively toward the deployment of fusion energy, which could substantially power modern society while mitigating climate change,” and suggested development of a pilot plant. The new National Academies study advances the concept with specifics on what a successful pilot plant would look like.
The report’s authors took a marketplace-driven approach to defining the pilot plant’s characteristics, based on discussions with utilities and other energy-sector organizations that would ultimately be the builders, owners, and operators of fusion generating facilities, says Whyte. “Setting those goal posts is very important, laying out the technical, regulatory, and economic performance requirements for the pilot plant,” he explains. “They’re demanding, but they should be, because that’s what’s needed to make fusion viable.”
Those requirements include a total pilot plant cost of less than $5-6 billion and generating capacity of at least 50 megawatts. In addition to proving the ability to create reliable, sustained net energy gain and power production from fusion for steadily increasing periods of time, says the report, the plant must provide “cost certainty to the marketplace in terms of capital cost, construction time, control of radioactive effluents including tritium, the cost of electricity, and the maintenance/operating schedule and cost.”
These results would inform subsequent construction of first-of-a-kind commercial fusion plants in the 2040s, and then broader propagation of fusion energy facilities onto the grid around mid-century, by which time major U.S. utilities have committed to deep reductions in their carbon emissions.
A key near-term factor in achieving these goals is formation of multiple public-private teams to conceptualize and design aspects of the pilot plant over the next seven years. These include improved fusion confinement and control, materials that can withstand the withering temperatures and stresses produced during fusion, methods of extracting fusion-generated heat and harnessing it for generation, and development of a closed fuel cycle. All are technically challenging and also require close attention to cost, manufacturability, maintainability, and other system-level considerations.
Combining resources from national labs, academic institutions, and private industry is a good approach to addressing these tasks, says Martin Greenwald, deputy director of the PSFC and senior research scientist. “Technologies like fusion come to market through the private sector, especially in the U.S., and once you understand that you can see appropriate roles for government labs that can do basic research, universities that are free to work with private industry, and companies that can use their own capital to pick up and commercialize the work.” Private space programs provide an example, he notes, with companies building rockets and using NASA facilities for things like testing and launch.
“The question,” adds Greenwald, “is whether we can collectively gather the resources and investments and execute in a way that meets the pace. We don’t want to be complacent about how audacious this is, but we have to be audacious if we’re going to meet the need.”
Bob Mumgaard, chief executive officer of CFS, says the new report is another indication of fusion’s growing momentum. In addition to the two National Academies studies, growing private investment, and FESAC’s community-driven recommendations, he points to the January enactment of federal appropriations legislation that funded both domestic and international fusion activities, including ongoing participation in ITER.
“For first time in 40 years, the U.S. government has a policy of building a new energy industry, a whole ecosystem,” says Mumgaard. “The legislation sort of pre-authorized many of the things the National Academies report says are good ideas, like the pivot into energy technology, the more-aggressive timeline, and getting regulation sorted out, which is going pretty well, actually — that’s all in the bill. It lays the groundwork for the broad community to take all this to heart and start doing the work. It’s very different from isolated companies doing their own thing, and universities running experiments, and has been very rapid in terms of how these things usually go. We are entering a whole new era for fusion.”
Cecil and Ida Green Professor Emeritus Ernest Moniz, who served as U.S. secretary of energy during the Obama administration, adds that “The academy report alerts the scientific community, the Congress, and the Biden Administration, which is prioritizing climate change risk mitigation, to the incredible progress over the last years towards fusion as a viable energy source — innovation along several technology pathways, supported largely by private capital. Public-private partnerships can help take several of these technologies to demonstrations in this decade, allowing fusion to be a critical enabler of a decarbonized electric grid before mid-century.” More

Perovskites are a leading candidate for eventually replacing silicon as the material of choice for solar panels. They offer the potential for low-cost, low-temperature manufacturing of ultrathin, lightweight flexible cells, but so far their efficiency at converting sunlight to electricity has lagged behind that of silicon and some other alternatives.
Now, a new approach to the design of perovskite cells has pushed the material to match or exceed the efficiency of today’s typical silicon cell, which generally ranges from 20 to 22 percent, laying the groundwork for further improvements.
By adding a specially treated conductive layer of tin dioxide bonded to the perovskite material, which provides an improved path for the charge carriers in the cell, and by modifying the perovskite formula, researchers have boosted its overall efficiency as a solar cell to 25.2 percent — a near-record for such materials, which eclipses the efficiency of many existing solar panels. (Perovskites still lag significantly in longevity compared to silicon, however, a challenge being worked on by teams around the world.)
The findings are described in a paper in the journal Nature by recent MIT graduate Jason Yoo PhD ’20, professor of chemistry and Lester Wolfe Professor Moungi Bawendi, professor of electrical engineering and computer science and Fariborz Maseeh Professor in Emerging Technology Vladimir Bulović, and 11 others at MIT, in South Korea, and in Georgia.
Perovskites are a broad class of materials defined by the fact that they have a particular kind of molecular arrangement, or lattice, that resembles that of the naturally occurring mineral perovskite. There are vast numbers of possible chemical combinations that can make perovskites, and Yoo explains that these materials have attracted worldwide interest because “at least on paper, they could be made much more cheaply than silicon or gallium arsenide,” one of the other leading contenders. That’s partly because of the much simpler processing and manufacturing processes, which for silicon or gallium arsenide requires sustained heat of over 1,000 degrees Celsius. In contrast, perovskites can be processed at less than 200 C, either in solution or by vapor deposition.
The other major advantage of perovskite over silicon or many other candidate replacements is that it forms extremely thin layers while still efficiently capturing solar energy. “Perovskite cells have the potential to be lightweight compared to silicon, by orders of magnitude,” Bawendi says.
Perovskites have a higher bandgap than silicon, which means they absorb a different part of the light spectrum and thus can complement silicon cells to provide even greater combined efficiencies. But even using only perovskite, Yoo says, “what we’re demonstrating is that even with a single active layer, we can make efficiencies that threaten silicon, and hopefully within punching distance of gallium arsenide. And both of those technologies have been around for much longer than perovskites have.”
One of the keys to the team’s improvement of the material’s efficiency, Bawendi explains, was in the precise engineering of one layer of the sandwich that makes up a perovskite solar cell — the electron transport layer. The perovskite itself is layered with a transparent conductive layer used to carry an electric current from the cell out to where it can be used. However, if the conductive layer is directly attached to the perovskite itself, the electrons and their counterparts, called holes, simply recombine on the spot and no current flows. In the researchers’ design, the perovskite and the conductive layer are separated by an improved type of intermediate layer that can let the electrons through while preventing the recombination.
This middle electron transport layer, and especially the interfaces where it connects to the layers on each side of it, tend to be where inefficiencies occur. By studying these mechanisms and designing a layer, consisting of tin oxide, that more perfectly conforms with those adjacent to it, the researchers were able to greatly reduce the losses.
The method they use is called chemical bath deposition. “It’s like slow cooking in a Crock-Pot,” Bawendi says. With a bath at 90 degrees Celsius, precursor chemicals slowly decompose to form the layer of tin dioxide in place. “The team realized that if we understood the decomposition mechanisms of these precursors, then we’d have a better understanding of how these films form. We were able to find the right window in which the electron transport layer with ideal properties can be synthesized.”
After a series of controlled experiments, they found that different mixtures of intermediate compounds would form, depending on the acidity of the precursor solution. They also identified a sweet spot of precursor compositions that allowed the reaction to produce a much more effective film.
The researchers combined these steps with an optimization of the perovskite layer itself. They used a set of additives to the perovskite recipe to improve its stability, which had been tried before but had an undesired effect on the material’s bandgap, making it a less efficient light absorber. The team found that by adding much smaller amounts of these additives — less than 1 percent — they could still get the beneficial effects without altering the bandgap.
The resulting improvement in efficiency has already driven the material to over 80 percent of the theoretical maximum efficiency that such materials could have, Yoo says.
While these high efficiencies were demonstrated in tiny lab-scale devices, Bawendi says that “the kind of insights we provide in this paper, and some of the tricks we provide, could potentially be applied to the methods that people are now developing for large-scale, manufacturable perovskite cells, and therefore boost those efficiencies.”
In pursuing the research further, there are two important avenues, he says: to continue pushing the limits on better efficiency, and to focus on increasing the material’s long-term stability, which currently is measured in months, compared to decades for silicon cells. But for some purposes, Bawendi points out, longevity may not be so essential. Many electronic devices such as cellphones, for example, tend to be replaced within a few years anyway, so there may be some useful applications even for relatively short-lived solar cells.
“I don’t think we’re there yet with these cells, even for these kind of shorter-term applications,” he says. “But people are getting close, so combining our ideas in this paper with ideas that other people have with increasing stability could lead to something really interesting.”
Robert Hoye, a lecturer in materials at Imperial College London, who was not part of the study, says, “This is excellent work by an international team.” He adds, “This could lead to greater reproducibility and the excellent device efficiencies achieved in the lab translating to commercialized modules. In terms of scientific milestones, not only do they achieve an efficiency that was the certified record for perovskite solar cells for much of last year, they also achieve open-circuit voltages up to 97 percent of the radiative limit. This is an astonishing achievement for solar cells grown from solution.”
The team included researchers at the Korea Research Institute of Chemical Technology, the Korea Advanced Institute of Science and Technology, the Ulsan National Institute of Science and Technology, and Georgia Tech. The work was supported by MIT’s Institute for Soldier Nanotechnology, NASA, the Italian company Eni SpA through the MIT Energy Initiative, the National Research Foundation of Korea, and the National Research Council of Science and Technology. More

“That was your warmup. Now we’re really in the thick of it.” 
Daniel Korsun ’20 is reflecting on his four years of undergraduate preparation and research at MIT as he enters “the thick” of graduate study at the Institute’s Plasma Science and Fusion Center (PSFC). The nuclear science and engineering student’s “warmup” included enough fusion research on the SPARC tokamak to establish him as part of the PSFC community.
“I already have this network of peers and professors and staff,” he notes with enthusiasm. “I’ve been kind of training for this for four years.”
Korsun arrived on the MIT campus in 2016 prepared to focus on chemistry, but quickly developed a fascination for the nuclear side of physics. Postponing one of his undergraduate course requirements, he indulged in Professor Mike Short’s Introduction to Nuclear Science class. After that he was “super hooked,” especially by the subject of fusion, a carbon-free, potentially endless source of energy.
Learning from his class colleague Monica Pham ’19 about a summer Undergraduate Research Opportunity Program (UROP) opening at the PSFC, Korsun applied and quickly found himself in the center’s accelerator laboratory, which is co-operated jointly with the Department of Nuclear Science and Engineering (NSE).
“I’ve always been interested in clean energy, advanced solar, climate change. When I actually got into the depths of fusion, seeing what the PSFC was doing — nothing ever compared.”
Korsun’s continuing excitement for research at the PSFC ultimately landed him in MIT’s SuperUROP undergraduate research program during his junior year. Guided by NSE Assistant Professor Zach Hartwig and his graduate students, Korsun was learning about the fusion research that remains his focus today, including SPARC, a next-generation fusion experiment that is prototype to a planned energy-producing fusion furnace called ARC.
Both these tokamak designs are being developed by MIT in association with Commonwealth Fusion Systems (CFS), and are dependent on game-changing, high-temperature superconducting (HTS) tape. Magnets created from this tape will wrap around the tokamak’s donut-shaped vacuum chamber, confining the hot plasma.
Korsun is exploring the effect of radiation, produced during the fusion process, on the HTS tapes. To do this he needs to test the critical current of the tapes, the maximum amount of current a superconductor can conduct while remaining in a superconducting state. Because radiation damage impacts how well superconductors can carry current, the critical current of the tapes changes in relation to how much they are irradiated.
“You can irradiate anything at room temperature,” he notes. “You just blast it with protons or neutrons. But that information is not really useful, because your SPARC and ARC magnets will be at cryogenic temperatures, and they’ll be operating in extremely strong magnetic fields as well. What if these low temperatures and high fields actually impact how the material responds to damage?”
Pursuing this question as an undergraduate took him with his teammates as far as Japan and New Zealand, where they could use special facilities to test the critical current of HTS tape under relevant conditions. “On our Japan trip to the High Field Laboratory for Superconducting Materials at Tohoku University, we conducted the SPARC project’s first-ever tests of HTS tape at the actual SPARC toroidal field magnetic field and temperature. It was a grueling trip — we generally worked about 15 or 16 hours a day in the lab — but incredible.”
The necessity of leaving campus in the spring of his senior year due to the Covid lockdown meant that Korsun would graduate virtually.
“It was not ideal. I’m not the kind of person to sit on my parents’ couch for six months.”
He made the most of his summer by securing a virtual internship at CFS, where he helped to refine ARC’s design based on what had been learned from SPARC research.
“Crazy amounts of knowledge have been gained that were not even fathomable five years ago, when it was designed.”
Korsun looks forward to the day when SPARC is operating, inspiring even more updates to the ARC design.
“It’s so easy to get excited about SPARC,” he says. “Everyone is, and I am, too. But it’s not quite the end goal. We’ve got to keep an eye on the distance.” More