Evelyn Reynolds

Latest story

50 Shares14 Views

Catherine Wolfram: High-energy scholar

by

In the mid 2000s, Catherine Wolfram PhD ’96 reached what she calls “an inflection point” in her career. After about a decade of studying U.S. electricity markets, she had come to recognize that “you couldn’t study the energy industries without thinking about climate mitigation,” as she puts it.At the same time, Wolfram understood that the trajectory of energy use in the developing world was a massively important part of the climate picture. To get a comprehensive grasp on global dynamics, she says, “I realized I needed to start thinking about the rest of the world.”An accomplished scholar and policy expert, Wolfram has been on the faculty at Harvard University, the University of California at Berkeley — and now MIT, where she is the William Barton Rogers Professor in Energy. She has also served as deputy assistant secretary for climate and energy economics at the U.S. Treasury.Yet even leading experts want to keep learning. So, when she hit that inflection point, Wolfram started carving out a new phase of her research career.“One of the things I love about being an academic is, I could just decide to do that,” Wolfram says. “I didn’t need to check with a boss. I could just pivot my career to being more focused to thinking about energy in the developing world.”Over the last decade, Wolfram has published a wide array of original studies about energy consumption in the developing world. From Kenya to Mexico to South Asia, she has shed light on the dynamics of economics growth and energy consumption — while spending some of that time serving the government too. Last year, Wolfram joined the faculty of the MIT Sloan School of Management, where her work bolsters the Institute’s growing effort to combat climate change.Studying at MITWolfram largely grew up in Minnesota, where her father was a legal scholar, although he moved to Cornell University around the time she started high school. As an undergraduate, she majored in economics at Harvard University, and after graduation she worked first for a consultant, then for the Massachusetts Department of Public Utilities, the agency regulating energy rates. In the latter job, Wolfram kept noticing that people were often citing the research of an MIT scholar named Paul Joskow (who is now the Elizabeth and James Killian Professor of Economics Emeritus in MIT’s Department of Economics) and Richard Schmalensee (a former dean of the MIT Sloan School of Management and now the Howard W. Johnson Professor of Management Emeritus). Seeing how consequential economics research could be for policymaking, Wolfram decided to get a PhD in the field and was accepted into MIT’s doctoral program.“I went into graduate school with an unusually specific view of what I wanted to do,” Wolfram says. “I wanted to work with Paul Joskow and Dick Schmalensee on electricity markets, and that’s how I wound up here.”At MIT, Wolfram also ended up working extensively with Nancy Rose, the Charles P. Kindleberger Professor of Applied Economics and a former head of the Department of Economics, who helped oversee Wolfram’s thesis; Rose has extensively studied market regulation as well.Wolfram’s dissertation research largely focused on price-setting behavior in the U.K.’s newly deregulated electricity markets, which, it turned out, applied handily to the U.S., where a similar process was taking place. “I was fortunate because this was around the time California was thinking about restructuring, as it was known,” Wolfram says. She spent four years on the faculty at Harvard, then moved to UC Berkeley. Wolfram’s studies have shown that deregulation has had some medium-term benefits, for instance in making power plants operate more efficiently.Turning on the ACBy around 2010, though, Wolfram began shifting her scholarly focus in earnest, conducting innovative studies about energy in the developing world. One strand of her research has centered on Kenya, to better understand how more energy access for people without electricity might fit into growth in the developing world.In this case, Wolfram’s perhaps surprising conclusion is that electrification itself is not a magic ticket to prosperity; people without electricity are more eager to adopt it when they have a practical economic need for it. Meanwhile, they have other essential needs that are not necessarily being addressed.“The 800 million people in the world who don’t have electricity also don’t have access to good health care or running water,” Wolfram says. “Giving them better housing infrastructure is important, and harder to tackle. It’s not clear that bringing people electricity alone is the single most useful thing from a development perspective. Although electricity is a super-important component of modern living.”Wolfram has even delved into topics such as air conditioner use in the developing world — an important driver of energy use. As her research shows, many countries, with a combined population far bigger than the U.S., are among the fastest-growing adopters of air conditioners and have an even greater need for them, based on their climates. Adoption of air conditioning within those countries also is characterized by marked economic inequality.From early 2021 until late 2022, Wolfram also served in the administration of President Joe Biden, where her work also centered on global energy issues. Among other things, Wolfram was part of the team working out a price-cap policy for Russian oil exports, a concept that she thinks could be applied to many other products globally. Although, she notes, working with countries heavily dependent on exporting energy materials will always require careful engagement.“We need to be mindful of that dependence and importance as we go through this massive effort to decarbonize the energy sector and shift it to a whole new paradigm,” Wolfram says.At MIT againStill, she notes, the world does need a whole new energy paradigm, and fast. Her arrival at MIT overlaps with the emergence of a new Institute-wide effort, the Climate Project at MIT, that aims to accelerate and scale climate solutions and good climate policy, including through the new Climate Policy Center at MIT Sloan. That kind of effort, Wolfram says, matters to her.“It’s part of why I’ve come to MIT,” Wolfram says. “Technology will be one part of the climate solution, but I do think an innovative mindset, how can we think about doing things better, can be productively applied to climate policy.” On being at MIT, she adds: “It’s great, it’s awesome. One of the things that pleasantly surprised me is how tight-knit and friendly the MIT faculty all are, and how many interactions I’ve had with people from other departments.”Wolfram has also been enjoying her teaching at MIT, and will be offering a large class in spring 2025, 15.016 (Climate and Energy in the Global Economy), that she debuted this past academic year.“It’s super fun to have students from around the world, who have personal stories and knowledge of energy systems in their countries and can contribute to our discussions,” she says.When it comes to tackling climate change, many things seem daunting. But there is still a world of knowledge to be acquired while we try to keep the planet from overheating, and Wolfram has a can-do attitude about learning more and applying those lessons.“We’ve made a lot of progress,” Wolfram says. “But we still have a lot more to do.” More

More stories

  • 50 Shares14 Views

    in Energy

    Catherine Wolfram: High-energy scholar

    In the mid 2000s, Catherine Wolfram PhD ’96 reached what she calls “an inflection point” in her career. After about a decade of studying U.S. electricity markets, she had come to recognize that “you couldn’t study the energy industries without thinking about climate mitigation,” as she puts it.At the same time, Wolfram understood that the trajectory of energy use in the developing world was a massively important part of the climate picture. To get a comprehensive grasp on global dynamics, she says, “I realized I needed to start thinking about the rest of the world.”An accomplished scholar and policy expert, Wolfram has been on the faculty at Harvard University, the University of California at Berkeley — and now MIT, where she is the William Barton Rogers Professor in Energy. She has also served as deputy assistant secretary for climate and energy economics at the U.S. Treasury.Yet even leading experts want to keep learning. So, when she hit that inflection point, Wolfram started carving out a new phase of her research career.“One of the things I love about being an academic is, I could just decide to do that,” Wolfram says. “I didn’t need to check with a boss. I could just pivot my career to being more focused to thinking about energy in the developing world.”Over the last decade, Wolfram has published a wide array of original studies about energy consumption in the developing world. From Kenya to Mexico to South Asia, she has shed light on the dynamics of economics growth and energy consumption — while spending some of that time serving the government too. Last year, Wolfram joined the faculty of the MIT Sloan School of Management, where her work bolsters the Institute’s growing effort to combat climate change.Studying at MITWolfram largely grew up in Minnesota, where her father was a legal scholar, although he moved to Cornell University around the time she started high school. As an undergraduate, she majored in economics at Harvard University, and after graduation she worked first for a consultant, then for the Massachusetts Department of Public Utilities, the agency regulating energy rates. In the latter job, Wolfram kept noticing that people were often citing the research of an MIT scholar named Paul Joskow (who is now the Elizabeth and James Killian Professor of Economics Emeritus in MIT’s Department of Economics) and Richard Schmalensee (a former dean of the MIT Sloan School of Management and now the Howard W. Johnson Professor of Management Emeritus). Seeing how consequential economics research could be for policymaking, Wolfram decided to get a PhD in the field and was accepted into MIT’s doctoral program.“I went into graduate school with an unusually specific view of what I wanted to do,” Wolfram says. “I wanted to work with Paul Joskow and Dick Schmalensee on electricity markets, and that’s how I wound up here.”At MIT, Wolfram also ended up working extensively with Nancy Rose, the Charles P. Kindleberger Professor of Applied Economics and a former head of the Department of Economics, who helped oversee Wolfram’s thesis; Rose has extensively studied market regulation as well.Wolfram’s dissertation research largely focused on price-setting behavior in the U.K.’s newly deregulated electricity markets, which, it turned out, applied handily to the U.S., where a similar process was taking place. “I was fortunate because this was around the time California was thinking about restructuring, as it was known,” Wolfram says. She spent four years on the faculty at Harvard, then moved to UC Berkeley. Wolfram’s studies have shown that deregulation has had some medium-term benefits, for instance in making power plants operate more efficiently.Turning on the ACBy around 2010, though, Wolfram began shifting her scholarly focus in earnest, conducting innovative studies about energy in the developing world. One strand of her research has centered on Kenya, to better understand how more energy access for people without electricity might fit into growth in the developing world.In this case, Wolfram’s perhaps surprising conclusion is that electrification itself is not a magic ticket to prosperity; people without electricity are more eager to adopt it when they have a practical economic need for it. Meanwhile, they have other essential needs that are not necessarily being addressed.“The 800 million people in the world who don’t have electricity also don’t have access to good health care or running water,” Wolfram says. “Giving them better housing infrastructure is important, and harder to tackle. It’s not clear that bringing people electricity alone is the single most useful thing from a development perspective. Although electricity is a super-important component of modern living.”Wolfram has even delved into topics such as air conditioner use in the developing world — an important driver of energy use. As her research shows, many countries, with a combined population far bigger than the U.S., are among the fastest-growing adopters of air conditioners and have an even greater need for them, based on their climates. Adoption of air conditioning within those countries also is characterized by marked economic inequality.From early 2021 until late 2022, Wolfram also served in the administration of President Joe Biden, where her work also centered on global energy issues. Among other things, Wolfram was part of the team working out a price-cap policy for Russian oil exports, a concept that she thinks could be applied to many other products globally. Although, she notes, working with countries heavily dependent on exporting energy materials will always require careful engagement.“We need to be mindful of that dependence and importance as we go through this massive effort to decarbonize the energy sector and shift it to a whole new paradigm,” Wolfram says.At MIT againStill, she notes, the world does need a whole new energy paradigm, and fast. Her arrival at MIT overlaps with the emergence of a new Institute-wide effort, the Climate Project at MIT, that aims to accelerate and scale climate solutions and good climate policy, including through the new Climate Policy Center at MIT Sloan. That kind of effort, Wolfram says, matters to her.“It’s part of why I’ve come to MIT,” Wolfram says. “Technology will be one part of the climate solution, but I do think an innovative mindset, how can we think about doing things better, can be productively applied to climate policy.” On being at MIT, she adds: “It’s great, it’s awesome. One of the things that pleasantly surprised me is how tight-knit and friendly the MIT faculty all are, and how many interactions I’ve had with people from other departments.”Wolfram has also been enjoying her teaching at MIT, and will be offering a large class in spring 2025, 15.016 (Climate and Energy in the Global Economy), that she debuted this past academic year.“It’s super fun to have students from around the world, who have personal stories and knowledge of energy systems in their countries and can contribute to our discussions,” she says.When it comes to tackling climate change, many things seem daunting. But there is still a world of knowledge to be acquired while we try to keep the planet from overheating, and Wolfram has a can-do attitude about learning more and applying those lessons.“We’ve made a lot of progress,” Wolfram says. “But we still have a lot more to do.” More

  • 113 Shares34 Views

    in Energy

    A nonflammable battery to power a safer, decarbonized future

    Lithium-ion batteries are the workhorses of home electronics and are powering an electric revolution in transportation. But they are not suitable for every application.A key drawback is their flammability and toxicity, which make large-scale lithium-ion energy storage a bad fit in densely populated city centers and near metal processing or chemical manufacturing plants.Now Alsym Energy has developed a nonflammable, nontoxic alternative to lithium-ion batteries to help renewables like wind and solar bridge the gap in a broader range of sectors. The company’s electrodes use relatively stable, abundant materials, and its electrolyte is primarily water with some nontoxic add-ons.“Renewables are intermittent, so you need storage, and to really solve the decarbonization problem, we need to be able to make these batteries anywhere at low cost,” says Alsym co-founder and MIT Professor Kripa Varanasi.The company believes its batteries, which are currently being tested by potential customers around the world, hold enormous potential to decarbonize the high-emissions industrial manufacturing sector, and they see other applications ranging from mining to powering data centers, homes, and utilities.“We are enabling a decarbonization of markets that was not possible before,” Alsym co-founder and CEO Mukesh Chatter says. “No chemical or steel plant would dare put a lithium battery close to their premises because of the flammability, and industrial emissions are a much bigger problem than passenger cars. With this approach, we’re able to offer a new path.”Helping 1 billion peopleChatter started a telecommunications company with serial entrepreneurs and longtime members of the MIT community Ray Stata ’57, SM ’58 and Alec Dingee ’52 in 1997. Since the company was acquired in 1999, Chatter and his wife have started other ventures and invested in some startups, but after losing his mother to cancer in 2012, Chatter decided he wanted to maximize his impact by only working on technologies that could reach 1 billion people or more.The problem Chatter decided to focus on was electricity access.“The intent was to light up the homes of at least 1 billion people around the world who either did not have electricity, or only got it part of the time, condemning them basically to a life of poverty in the 19th century,” Chatter says. “When you don’t have access to electricity, you also don’t have the internet, cell phones, education, etc.”To solve the problem, Chatter decided to fund research into a new kind of battery. The battery had to be cheap enough to be adopted in low-resource settings, safe enough to be deployed in crowded areas, and work well enough to support two light bulbs, a fan, a refrigerator, and an internet modem.At first, Chatter was surprised how few takers he had to start the research, even from researchers at the top universities in the world.“It’s a burning problem, but the risk of failure was so high that nobody wanted to take the chance,” Chatter recalls.He finally found his partners in Varanasi, Rensselaer Polytechnic Institute Professor Nikhil Koratkar and Rensselaer researcher Rahul Mukherjee. Varanasi, who notes he’s been at MIT for 22 years, says the Institute’s culture gave him the confidence to tackle big problems.“My students, postdocs, and colleagues are inspirational to me,” he says. “The MIT ecosystem infuses us with this resolve to go after problems that look insurmountable.”Varanasi leads an interdisciplinary lab at MIT dedicated to understanding physicochemical and biological phenomena. His research has spurred the creation of materials, devices, products, and processes to tackle challenges in energy, agriculture, and other sectors, as well as startup companies to commercialize this work.“Working at the interfaces of matter has unlocked numerous new research pathways across various fields, and MIT has provided me the creative freedom to explore, discover, and learn, and apply that knowledge to solve critical challenges,” he says. “I was able to draw significantly from my learnings as we set out to develop the new battery technology.”Alsym’s founding team began by trying to design a battery from scratch based on new materials that could fit the parameters defined by Chatter. To make it nonflammable and nontoxic, the founders wanted to avoid lithium and cobalt.After evaluating many different chemistries, the founders settled on Alsym’s current approach, which was finalized in 2020.Although the full makeup of Alsym’s battery is still under wraps as the company waits to be granted patents, one of Alsym’s electrodes is made mostly of manganese oxide while the other is primarily made of a metal oxide. The electrolyte is primarily water.There are several advantages to Alsym’s new battery chemistry. Because the battery is inherently safer and more sustainable than lithium-ion, the company doesn’t need the same safety protections or cooling equipment, and it can pack its batteries close to each other without fear of fires or explosions. Varanasi also says the battery can be manufactured in any of today’s lithium-ion plants with minimal changes and at significantly lower operating cost.“We are very excited right now,” Chatter says. “We started out wanting to light up 1 billion people’s homes, and now in addition to the original goal we have a chance to impact the entire globe if we are successful at cutting back industrial emissions.”A new platform for energy storageAlthough the batteries don’t quite reach the energy density of lithium-ion batteries, Varanasi says Alsym is first among alternative chemistries at the system-level. He says 20-foot containers of Alsym’s batteries can provide 1.7 megawatt hours of electricity. The batteries can also fast-charge over four hours and can be configured to discharge over anywhere from two to 110 hours.“We’re highly configurable, and that’s important because depending on where you are, you can sometimes run on two cycles a day with solar, and in combination with wind, you could truly get 24/7 electricity,” Chatter says. “The need to do multiday or long duration storage is a small part of the market, but we support that too.”Alsym has been manufacturing prototypes at a small facility in Woburn, Massachusetts, for the last two years, and early this year it expanded its capacity and began to send samples to customers for field testing.In addition to large utilities, the company is working with municipalities, generator manufacturers, and providers of behind-the-meter power for residential and commercial buildings. The company is also in discussion with a large chemical manufacturers and metal processing plants to provide energy storage system to reduce their carbon footprint, something they say was not feasible with lithium-ion batteries, due to their flammability, or with nonlithium batteries, due to their large space requirements.Another critical area is data centers. With the growth of AI, the demand for data centers — and their energy consumption — is set to surge.“We must power the AI and digitization revolution without compromising our planet,” says Varanasi, adding that lithium batteries are unsuitable for co-location with data centers due to flammability risks. “Alsym batteries are well-positioned to offer a safer, more sustainable alternative. Intermittency is also a key issue for electrolyzers used in green hydrogen production and other markets.”Varanasi sees Alsym as a platform company, and Chatter says Alsym is already working on other battery chemistries that have higher densities and maintain performance at even more extreme temperatures.“When you use a single material in any battery, and the whole world starts to use it, you run out of that material,” Varanasi says. “What we have is a platform that has enabled us to not just to come up with just one chemistry, but at least three or four chemistries targeted at different applications so no one particular set of materials will be stressed in terms of supply.” More

  • 138 Shares22 Views

    in Energy

    Reality check on technologies to remove carbon dioxide from the air

    In 2015, 195 nations plus the European Union signed the Paris Agreement and pledged to undertake plans designed to limit the global temperature increase to 1.5 degrees Celsius. Yet in 2023, the world exceeded that target for most, if not all of, the year — calling into question the long-term feasibility of achieving that target.To do so, the world must reduce the levels of greenhouse gases in the atmosphere, and strategies for achieving levels that will “stabilize the climate” have been both proposed and adopted. Many of those strategies combine dramatic cuts in carbon dioxide (CO2) emissions with the use of direct air capture (DAC), a technology that removes CO2 from the ambient air. As a reality check, a team of researchers in the MIT Energy Initiative (MITEI) examined those strategies, and what they found was alarming: The strategies rely on overly optimistic — indeed, unrealistic — assumptions about how much CO2 could be removed by DAC. As a result, the strategies won’t perform as predicted. Nevertheless, the MITEI team recommends that work to develop the DAC technology continue so that it’s ready to help with the energy transition — even if it’s not the silver bullet that solves the world’s decarbonization challenge.DAC: The promise and the realityIncluding DAC in plans to stabilize the climate makes sense. Much work is now under way to develop DAC systems, and the technology looks promising. While companies may never run their own DAC systems, they can already buy “carbon credits” based on DAC. Today, a multibillion-dollar market exists on which entities or individuals that face high costs or excessive disruptions to reduce their own carbon emissions can pay others to take emissions-reducing actions on their behalf. Those actions can involve undertaking new renewable energy projects or “carbon-removal” initiatives such as DAC or afforestation/reforestation (planting trees in areas that have never been forested or that were forested in the past). DAC-based credits are especially appealing for several reasons, explains Howard Herzog, a senior research engineer at MITEI. With DAC, measuring and verifying the amount of carbon removed is straightforward; the removal is immediate, unlike with planting forests, which may take decades to have an impact; and when DAC is coupled with CO2 storage in geologic formations, the CO2 is kept out of the atmosphere essentially permanently — in contrast to, for example, sequestering it in trees, which may one day burn and release the stored CO2.Will current plans that rely on DAC be effective in stabilizing the climate in the coming years? To find out, Herzog and his colleagues Jennifer Morris and Angelo Gurgel, both MITEI principal research scientists, and Sergey Paltsev, a MITEI senior research scientist — all affiliated with the MIT Center for Sustainability Science and Strategy (CS3) — took a close look at the modeling studies on which those plans are based.Their investigation identified three unavoidable engineering challenges that together lead to a fourth challenge — high costs for removing a single ton of CO2 from the atmosphere. The details of their findings are reported in a paper published in the journal One Earth on Sept. 20.Challenge 1: Scaling upWhen it comes to removing CO2 from the air, nature presents “a major, non-negotiable challenge,” notes the MITEI team: The concentration of CO2 in the air is extremely low — just 420 parts per million, or roughly 0.04 percent. In contrast, the CO2 concentration in flue gases emitted by power plants and industrial processes ranges from 3 percent to 20 percent. Companies now use various carbon capture and sequestration (CCS) technologies to capture CO2 from their flue gases, but capturing CO2 from the air is much more difficult. To explain, the researchers offer the following analogy: “The difference is akin to needing to find 10 red marbles in a jar of 25,000 marbles of which 24,990 are blue [the task representing DAC] versus needing to find about 10 red marbles in a jar of 100 marbles of which 90 are blue [the task for CCS].”Given that low concentration, removing a single metric ton (tonne) of CO2 from air requires processing about 1.8 million cubic meters of air, which is roughly equivalent to the volume of 720 Olympic-sized swimming pools. And all that air must be moved across a CO2-capturing sorbent — a feat requiring large equipment. For example, one recently proposed design for capturing 1 million tonnes of CO2 per year would require an “air contactor” equivalent in size to a structure about three stories high and three miles long.Recent modeling studies project DAC deployment on the scale of 5 to 40 gigatonnes of CO2 removed per year. (A gigatonne equals 1 billion metric tonnes.) But in their paper, the researchers conclude that the likelihood of deploying DAC at the gigatonne scale is “highly uncertain.”Challenge 2: Energy requirementGiven the low concentration of CO2 in the air and the need to move large quantities of air to capture it, it’s no surprise that even the best DAC processes proposed today would consume large amounts of energy — energy that’s generally supplied by a combination of electricity and heat. Including the energy needed to compress the captured CO2 for transportation and storage, most proposed processes require an equivalent of at least 1.2 megawatt-hours of electricity for each tonne of CO2 removed.The source of that electricity is critical. For example, using coal-based electricity to drive an all-electric DAC process would generate 1.2 tonnes of CO2 for each tonne of CO2 captured. The result would be a net increase in emissions, defeating the whole purpose of the DAC. So clearly, the energy requirement must be satisfied using either low-carbon electricity or electricity generated using fossil fuels with CCS. All-electric DAC deployed at large scale — say, 10 gigatonnes of CO2 removed annually — would require 12,000 terawatt-hours of electricity, which is more than 40 percent of total global electricity generation today.Electricity consumption is expected to grow due to increasing overall electrification of the world economy, so low-carbon electricity will be in high demand for many competing uses — for example, in power generation, transportation, industry, and building operations. Using clean electricity for DAC instead of for reducing CO2 emissions in other critical areas raises concerns about the best uses of clean electricity.Many studies assume that a DAC unit could also get energy from “waste heat” generated by some industrial process or facility nearby. In the MITEI researchers’ opinion, “that may be more wishful thinking than reality.” The heat source would need to be within a few miles of the DAC plant for transporting the heat to be economical; given its high capital cost, the DAC plant would need to run nonstop, requiring constant heat delivery; and heat at the temperature required by the DAC plant would have competing uses, for example, for heating buildings. Finally, if DAC is deployed at the gigatonne per year scale, waste heat will likely be able to provide only a small fraction of the needed energy.Challenge 3: SitingSome analysts have asserted that, because air is everywhere, DAC units can be located anywhere. But in reality, siting a DAC plant involves many complex issues. As noted above, DAC plants require significant amounts of energy, so having access to enough low-carbon energy is critical. Likewise, having nearby options for storing the removed CO2 is also critical. If storage sites or pipelines to such sites don’t exist, major new infrastructure will need to be built, and building new infrastructure of any kind is expensive and complicated, involving issues related to permitting, environmental justice, and public acceptability — issues that are, in the words of the researchers, “commonly underestimated in the real world and neglected in models.”Two more siting needs must be considered. First, meteorological conditions must be acceptable. By definition, any DAC unit will be exposed to the elements, and factors like temperature and humidity will affect process performance and process availability. And second, a DAC plant will require some dedicated land — though how much is unclear, as the optimal spacing of units is as yet unresolved. Like wind turbines, DAC units need to be properly spaced to ensure maximum performance such that one unit is not sucking in CO2-depleted air from another unit.Challenge 4: CostConsidering the first three challenges, the final challenge is clear: the cost per tonne of CO2 removed is inevitably high. Recent modeling studies assume DAC costs as low as $100 to $200 per ton of CO2 removed. But the researchers found evidence suggesting far higher costs.To start, they cite typical costs for power plants and industrial sites that now use CCS to remove CO2 from their flue gases. The cost of CCS in such applications is estimated to be in the range of $50 to $150 per ton of CO2 removed. As explained above, the far lower concentration of CO2 in the air will lead to substantially higher costs.As explained under Challenge 1, the DAC units needed to capture the required amount of air are massive. The capital cost of building them will be high, given labor, materials, permitting costs, and so on. Some estimates in the literature exceed $5,000 per tonne captured per year.Then there are the ongoing costs of energy. As noted under Challenge 2, removing 1 tonne of CO2 requires the equivalent of 1.2 megawatt-hours of electricity. If that electricity costs $0.10 per kilowatt-hour, the cost of just the electricity needed to remove 1 tonne of CO2 is $120. The researchers point out that assuming such a low price is “questionable,” given the expected increase in electricity demand, future competition for clean energy, and higher costs on a system dominated by renewable — but intermittent — energy sources.Then there’s the cost of storage, which is ignored in many DAC cost estimates.Clearly, many considerations show that prices of $100 to $200 per tonne are unrealistic, and assuming such low prices will distort assessments of strategies, leading them to underperform going forward.The bottom lineIn their paper, the MITEI team calls DAC a “very seductive concept.” Using DAC to suck CO2 out of the air and generate high-quality carbon-removal credits can offset reduction requirements for industries that have hard-to-abate emissions. By doing so, DAC would minimize disruptions to key parts of the world’s economy, including air travel, certain carbon-intensive industries, and agriculture. However, the world would need to generate billions of tonnes of CO2 credits at an affordable price. That prospect doesn’t look likely. The largest DAC plant in operation today removes just 4,000 tonnes of CO2 per year, and the price to buy the company’s carbon-removal credits on the market today is $1,500 per tonne.The researchers recognize that there is room for energy efficiency improvements in the future, but DAC units will always be subject to higher work requirements than CCS applied to power plant or industrial flue gases, and there is not a clear pathway to reducing work requirements much below the levels of current DAC technologies.Nevertheless, the researchers recommend that work to develop DAC continue “because it may be needed for meeting net-zero emissions goals, especially given the current pace of emissions.” But their paper concludes with this warning: “Given the high stakes of climate change, it is foolhardy to rely on DAC to be the hero that comes to our rescue.” More

  • 138 Shares48 Views

    in Energy

    Turning automotive engines into modular chemical plants to make green fuels

    Reducing methane emissions is a top priority in the fight against climate change because of its propensity to trap heat in the atmosphere: Methane’s warming effects are 84 times more potent than CO2 over a 20-year timescale.And yet, as the main component of natural gas, methane is also a valuable fuel and a precursor to several important chemicals. The main barrier to using methane emissions to create carbon-negative materials is that human sources of methane gas — landfills, farms, and oil and gas wells — are relatively small and spread out across large areas, while traditional chemical processing facilities are huge and centralized. That makes it prohibitively expensive to capture, transport, and convert methane gas into anything useful. As a result, most companies burn or “flare” their methane at the site where it’s emitted, seeing it as a sunk cost and an environmental liability.The MIT spinout Emvolon is taking a new approach to processing methane by repurposing automotive engines to serve as modular, cost-effective chemical plants. The company’s systems can take methane gas and produce liquid fuels like methanol and ammonia on-site; these fuels can then be used or transported in standard truck containers.”We see this as a new way of chemical manufacturing,” Emvolon co-founder and CEO Emmanuel Kasseris SM ’07, PhD ’11 says. “We’re starting with methane because methane is an abundant emission that we can use as a resource. With methane, we can solve two problems at the same time: About 15 percent of global greenhouse gas emissions come from hard-to-abate sectors that need green fuel, like shipping, aviation, heavy heavy-duty trucks, and rail. Then another 15 percent of emissions come from distributed methane emissions like landfills and oil wells.”By using mass-produced engines and eliminating the need to invest in infrastructure like pipelines, the company says it’s making methane conversion economically attractive enough to be adopted at scale. The system can also take green hydrogen produced by intermittent renewables and turn it into ammonia, another fuel that can also be used to decarbonize fertilizers.“In the future, we’re going to need green fuels because you can’t electrify a large ship or plane — you have to use a high-energy-density, low-carbon-footprint, low-cost liquid fuel,” Kasseris says. “The energy resources to produce those green fuels are either distributed, as is the case with methane, or variable, like wind. So, you cannot have a massive plant [producing green fuels] that has its own zip code. You either have to be distributed or variable, and both of those approaches lend themselves to this modular design.”From a “crazy idea” to a companyKasseris first came to MIT to study mechanical engineering as a graduate student in 2004, when he worked in the Sloan Automotive Lab on a report on the future of transportation. For his PhD, he developed a novel technology for improving internal combustion engine fuel efficiency for a consortium of automotive and energy companies, which he then went to work for after graduation.Around 2014, he was approached by Leslie Bromberg ’73, PhD ’77, a serial inventor with more than 100 patents, who has been a principal research engineer in MIT’s Plasma Science and Fusion Center for nearly 50 years.“Leslie had this crazy idea of repurposing an internal combustion engine as a reactor,” Kasseris recalls. “I had looked at that while working in industry, and I liked it, but my company at the time thought the work needed more validation.”Bromberg had done that validation through a U.S. Department of Energy-funded project in which he used a diesel engine to “reform” methane — a high-pressure chemical reaction in which methane is combined with steam and oxygen to produce hydrogen. The work impressed Kasseris enough to bring him back to MIT as a research scientist in 2016.“We worked on that idea in addition to some other projects, and eventually it had reached the point where we decided to license the work from MIT and go full throttle,” Kasseris recalls. “It’s very easy to work with MIT’s Technology Licensing Office when you are an MIT inventor. You can get a low-cost licensing option, and you can do a lot with that, which is important for a new company. Then, once you are ready, you can finalize the license, so MIT was instrumental.”Emvolon continued working with MIT’s research community, sponsoring projects with Professor Emeritus John Heywood and participating in the MIT Venture Mentoring Service and the MIT Industrial Liaison Program.An engine-powered chemical plantAt the core of Emvolon’s system is an off-the-shelf automotive engine that runs “fuel rich” — with a higher ratio of fuel to air than what is needed for complete combustion.“That’s easy to say, but it takes a lot of [intellectual property], and that’s what was developed at MIT,” Kasseris says. “Instead of burning the methane in the gas to carbon dioxide and water, you partially burn it, or partially oxidize it, to carbon monoxide and hydrogen, which are the building blocks to synthesize a variety of chemicals.”The hydrogen and carbon monoxide are intermediate products used to synthesize different chemicals through further reactions. Those processing steps take place right next to the engine, which makes its own power. Each of Emvolon’s standalone systems fits within a 40-foot shipping container and can produce about 8 tons of methanol per day from 300,000 standard cubic feet of methane gas.The company is starting with green methanol because it’s an ideal fuel for hard-to-abate sectors such as shipping and heavy-duty transport, as well as an excellent feedstock for other high-value chemicals, such as sustainable aviation fuel. Many shipping vessels have already converted to run on green methanol in an effort to meet decarbonization goals.This summer, the company also received a grant from the Department of Energy to adapt its process to produce clean liquid fuels from power sources like solar and wind.“We’d like to expand to other chemicals like ammonia, but also other feedstocks, such as biomass and hydrogen from renewable electricity, and we already have promising results in that direction” Kasseris says. “We think we have a good solution for the energy transition and, in the later stages of the transition, for e-manufacturing.”A scalable approachEmvolon has already built a system capable of producing up to six barrels of green methanol a day in its 5,000 square-foot headquarters in Woburn, Massachusetts.“For chemical technologies, people talk about scale up risk, but with an engine, if it works in a single cylinder, we know it will work in a multicylinder engine,” Kasseris says. “It’s just engineering.”Last month, Emvolon announced an agreement with Montauk Renewables to build a commercial-scale demonstration unit next to a Texas landfill that will initially produce up to 15,000 gallons of green methanol a year and later scale up to 2.5 million gallons. That project could be expanded tenfold by scaling across Montauk’s other sites.“Our whole process was designed to be a very realistic approach to the energy transition,” Kasseris says. “Our solution is designed to produce green fuels and chemicals at prices that the markets are willing to pay today, without the need for subsidies. Using the engines as chemical plants, we can get the capital expenditure per unit output close to that of a large plant, but at a modular scale that enables us to be next to low-cost feedstock. Furthermore, our modular systems require small investments — of $1 to 10 million — that are quickly deployed, one at a time, within weeks, as opposed to massive chemical plants that require multiyear capital construction projects and cost hundreds of millions.” More

  • 50 Shares45 Views

    in Energy

    Ensuring a durable transition

    To fend off the worst impacts of climate change, “we have to decarbonize, and do it even faster,” said William H. Green, director of the MIT Energy Initiative (MITEI) and Hoyt C. Hottel Professor, MIT Department of Chemical Engineering, at MITEI’s Annual Research Conference.“But how the heck do we actually achieve this goal when the United States is in the middle of a divisive election campaign, and globally, we’re facing all kinds of geopolitical conflicts, trade protectionism, weather disasters, increasing demand from developing countries building a middle class, and data centers in countries like the U.S.?”Researchers, government officials, and business leaders convened in Cambridge, Massachusetts, Sept. 25-26 to wrestle with this vexing question at the conference that was themed, “A durable energy transition: How to stay on track in the face of increasing demand and unpredictable obstacles.”“In this room we have a lot of power,” said Green, “if we work together, convey to all of society what we see as real pathways and policies to solve problems, and take collective action.”The critical role of consensus-building in driving the energy transition arose repeatedly in conference sessions, whether the topic involved developing and adopting new technologies, constructing and siting infrastructure, drafting and passing vital energy policies, or attracting and retaining a skilled workforce.Resolving conflictsThere is “blowback and a social cost” in transitioning away from fossil fuels, said Stephen Ansolabehere, the Frank G. Thompson Professor of Government at Harvard University, in a panel on the social barriers to decarbonization. “Companies need to engage differently and recognize the rights of communities,” he said.Nora DeDontney, director of development at Vineyard Offshore, described her company’s two years of outreach and negotiations to bring large cables from ocean-based wind turbines onshore.“Our motto is, ‘community first,’” she said. Her company works to mitigate any impacts towns might feel because of offshore wind infrastructure construction with projects, such as sewer upgrades; provides workforce training to Tribal Nations; and lays out wind turbines in a manner that provides safe and reliable areas for local fisheries.Elsa A. Olivetti, professor in the Department of Materials Science and Engineering at MIT and the lead of the Decarbonization Mission of MIT’s new Climate Project, discussed the urgent need for rapid scale-up of mineral extraction. “Estimates indicate that to electrify the vehicle fleet by 2050, about six new large copper mines need to come on line each year,” she said. To meet the demand for metals in the United States means pushing into Indigenous lands and environmentally sensitive habitats. “The timeline of permitting is not aligned with the temporal acceleration needed,” she said.Larry Susskind, the Ford Professor of Urban and Environmental Planning in the MIT Department of Urban Studies and Planning, is trying to resolve such tensions with universities playing the role of mediators. He is creating renewable energy clinics where students train to participate in emerging disputes over siting. “Talk to people before decisions are made, conduct joint fact finding, so that facilities reduce harms and share the benefits,” he said.Clean energy boom and pressureA relatively recent and unforeseen increase in demand for energy comes from data centers, which are being built by large technology companies for new offerings, such as artificial intelligence.“General energy demand was flat for 20 years — and now, boom,” said Sean James, Microsoft’s senior director of data center research. “It caught utilities flatfooted.” With the expansion of AI, the rush to provision data centers with upwards of 35 gigawatts of new (and mainly renewable) power in the near future, intensifies pressure on big companies to balance the concerns of stakeholders across multiple domains. Google is pursuing 24/7 carbon-free energy by 2030, said Devon Swezey, the company’s senior manager for global energy and climate.“We’re pursuing this by purchasing more and different types of clean energy locally, and accelerating technological innovation such as next-generation geothermal projects,” he said. Pedro Gómez Lopez, strategy and development director, Ferrovial Digital, which designs and constructs data centers, incorporates renewable energy into their projects, which contributes to decarbonization goals and benefits to locales where they are sited. “We can create a new supply of power, taking the heat generated by a data center to residences or industries in neighborhoods through District Heating initiatives,” he said.The Inflation Reduction Act and other legislation has ramped up employment opportunities in clean energy nationwide, touching every region, including those most tied to fossil fuels. “At the start of 2024 there were about 3.5 million clean energy jobs, with ‘red’ states showing the fastest growth in clean energy jobs,” said David S. Miller, managing partner at Clean Energy Ventures. “The majority (58 percent) of new jobs in energy are now in clean energy — that transition has happened. And one-in-16 new jobs nationwide were in clean energy, with clean energy jobs growing more than three times faster than job growth economy-wide”In this rapid expansion, the U.S. Department of Energy (DoE) is prioritizing economically marginalized places, according to Zoe Lipman, lead for good jobs and labor standards in the Office of Energy Jobs at the DoE. “The community benefit process is integrated into our funding,” she said. “We are creating the foundation of a virtuous circle,” encouraging benefits to flow to disadvantaged and energy communities, spurring workforce training partnerships, and promoting well-paid union jobs. “These policies incentivize proactive community and labor engagement, and deliver community benefits, both of which are key to building support for technological change.”Hydrogen opportunity and challengeWhile engagement with stakeholders helps clear the path for implementation of technology and the spread of infrastructure, there remain enormous policy, scientific, and engineering challenges to solve, said multiple conference participants. In a “fireside chat,” Prasanna V. Joshi, vice president of low-carbon-solutions technology at ExxonMobil, and Ernest J. Moniz, professor of physics and special advisor to the president at MIT, discussed efforts to replace natural gas and coal with zero-carbon hydrogen in order to reduce greenhouse gas emissions in such major industries as steel and fertilizer manufacturing.“We have gone into an era of industrial policy,” said Moniz, citing a new DoE program offering incentives to generate demand for hydrogen — more costly than conventional fossil fuels — in end-use applications. “We are going to have to transition from our current approach, which I would call carrots-and-twigs, to ultimately, carrots-and-sticks,” Moniz warned, in order to create “a self-sustaining, major, scalable, affordable hydrogen economy.”To achieve net zero emissions by 2050, ExxonMobil intends to use carbon capture and sequestration in natural gas-based hydrogen and ammonia production. Ammonia can also serve as a zero-carbon fuel. Industry is exploring burning ammonia directly in coal-fired power plants to extend the hydrogen value chain. But there are challenges. “How do you burn 100 percent ammonia?”, asked Joshi. “That’s one of the key technology breakthroughs that’s needed.” Joshi believes that collaboration with MIT’s “ecosystem of breakthrough innovation” will be essential to breaking logjams around the hydrogen and ammonia-based industries.MIT ingenuity essentialThe energy transition is placing very different demands on different regions around the world. Take India, where today per capita power consumption is one of the lowest. But Indians “are an aspirational people … and with increasing urbanization and industrial activity, the growth in power demand is expected to triple by 2050,” said Praveer Sinha, CEO and managing director of the Tata Power Co. Ltd., in his keynote speech. For that nation, which currently relies on coal, the move to clean energy means bringing another 300 gigawatts of zero-carbon capacity online in the next five years. Sinha sees this power coming from wind, solar, and hydro, supplemented by nuclear energy.“India plans to triple nuclear power generation capacity by 2032, and is focusing on advancing small modular reactors,” said Sinha. “The country also needs the rapid deployment of storage solutions to firm up the intermittent power.” The goal is to provide reliable electricity 24/7 to a population living both in large cities and in geographically remote villages, with the help of long-range transmission lines and local microgrids. “India’s energy transition will require innovative and affordable technology solutions, and there is no better place to go than MIT, where you have the best brains, startups, and technology,” he said.These assets were on full display at the conference. Among them a cluster of young businesses, including:the MIT spinout Form Energy, which has developed a 100-hour iron battery as a backstop to renewable energy sources in case of multi-day interruptions;startup Noya that aims for direct air capture of atmospheric CO2 using carbon-based materials;the firm Active Surfaces, with a lightweight material for putting solar photovoltaics in previously inaccessible places;Copernic Catalysts, with new chemistry for making ammonia and sustainable aviation fuel far more inexpensively than current processes; andSesame Sustainability, a software platform spun out of MITEI that gives industries a full financial analysis of the costs and benefits of decarbonization.The pipeline of research talent extended into the undergraduate ranks, with a conference “slam” competition showcasing students’ summer research projects in areas from carbon capture using enzymes to 3D design for the coils used in fusion energy confinement.“MIT students like me are looking to be the next generation of energy leaders, looking for careers where we can apply our engineering skills to tackle exciting climate problems and make a tangible impact,” said Trent Lee, a junior in mechanical engineering researching improvements in lithium-ion energy storage. “We are stoked by the energy transition, because it’s not just the future, but our chance to build it.” More

  • 75 Shares107 Views

    in Energy

    Preparing Taiwan for a decarbonized economy

    The operations of Taiwan’s electronics, manufacturing, and financial firms vary widely, but their leaders all have at least one thing in common: They recognize the role that a changing energy landscape will play in their future success, and they’re actively planning for that transition.“They’re all interested in how Taiwan can supply energy for its economy going forward — energy that meets global goals for decarbonization,” says Robert C. Armstrong, the Chevron Professor of Chemical Engineering Emeritus at MIT, as well as a principal investigator for the Taiwan Innovative Green Economy Roadmap (TIGER) program. “Each company is going to have its own particular needs. For example, financial companies have data centers that need energy 24/7, with no interruptions. But the need for a robust, reliable, resilient energy system is shared among all of them.”Ten Taiwanese companies are participating in TIGER, a two-year program with the MIT Energy Initiative (MITEI) to explore various ways that industry and government can promote and adopt technologies, practices, and policies that will keep Taiwan competitive amid a quickly changing energy landscape. MIT research teams are exploring a set of six topics during the first year of the program, with plans to tackle a second set of topics during the second year, eventually leading to a roadmap to green energy security for Taiwan.“We are helping them to understand green energy technologies, we are helping them to understand how policies around the world might affect supply chains, and we are helping them to understand different pathways for their domestic policies,” says Sergey Paltsev, a principal investigator for the TIGER program, as well as a deputy director of the MIT Center for Sustainability Science and Strategy and a senior research scientist at MITEI. “We are looking at how Taiwan will be affected in terms of the cost of doing business and how to preserve the competitive advantage of its export-oriented industries.”“The biggest question,” Paltsev adds, “is how Taiwanese companies can decarbonize their energy in a sustainable manner.”Why Taiwan?Paul Hsu, founding partner of the Taiwanese business consultancy Paul Hsu and Partners (one of the 10 participating TIGER companies), as well as founding chair and current board member of the Epoch Foundation, has been working for more than 30 years to forge collaborations between business leaders in Taiwan and MIT researchers. The energy challenges facing Taiwanese businesses, as well as their place in the global supply chain, make the TIGER program critical not only to improve environmental sustainability, but also to ensure future competitiveness, he says. “The energy field is facing revolution,” Hsu says. “Taiwanese companies are not operating in Taiwan alone, but also operating worldwide, and we are affected by the global supply chain. We need to diversify our businesses and our energy resources, and the first thing we’re looking for in this partnership is education — an understanding about how to orient Taiwanese industry toward the future of energy.”Wendy Duan, the program director of the Asia Pacific program at MITEI, notes that Taiwan has a number of similarities to places such as Singapore and Japan. The lessons learned through the TIGER program, she says, will likely be applicable — at least on some level — to other markets throughout Asia, and even around the world.“Taiwan is very much dependent on imported energy,” Duan notes. “Many countries in East Asia are facing similar challenges, and if Taiwan has a good roadmap for the future of energy, it can be a good role model.”“Taiwan is a great place for this sort of collaboration,” Armstrong says. “Their industry is very innovative, and it’s a place where businesses are willing to implement new, important ideas. At the same time, their economy is highly dependent on trade, and they import a lot of fossil fuels today. To compete in a decarbonized global economy, they’re going to have to find alternatives to that. If you can develop a path from today’s economy in Taiwan to a future manufacturing economy that is decarbonized, then that gives you a lot of interesting tools you could bring to bear in other economies.”Uncovering solutionsStakeholders from MIT and the participating companies meet for monthly webinars and biannual in-person workshops (alternating between Cambridge, Massachusetts, and Taipei) to discuss progress. The research addresses options for Taiwan to increase its supply of green energy, methods for storing and distributing that energy more efficiently, policy levers for implementing these changes, and Taiwan’s place in the global energy economy.“The project on the electric grid, the project on storage, and the project on hydrogen — all three of those are related to the issue of how to decarbonize power generation and delivery,” notes Paltsev. “But we also need to understand how things in other parts of the world are going to affect demand for the products that are produced in Taiwan. If there is a huge change in demand for certain products due to decarbonization, Taiwanese companies are going to feel it. Therefore, the companies want to understand where the demand is going to be coming from, and how to adjust their business strategies.”One of the research projects is looking closely at advanced nuclear power. There are significant political roadblocks standing in the way, but business leaders are intrigued by the prospect of nuclear energy in Taiwan, where available land for wind and solar power generation is sparse.“So far, Taiwan government policy is anti-nuclear,” Hsu says. “The current ruling party is against it. They are still thinking about what happened in the 1960s and 1970s, and they think nuclear is very dangerous. But if you look into it, nuclear generation technology has really improved.”Implementing a green economy roadmapTIGER participants’ interest in green energy solutions is, of course, not merely academic. Ultimately, the success of the program will be determined not only by the insights from the research produced over these two years, but by how these findings constructively inform both the private and public sectors.“MIT and TIGER participants are united in their commitment to advancing regional industrial and economic development, while championing decarbonization and sustainability efforts in Taiwan,” Duan says. “MIT researchers are informed by insights and domain expertise contributed by TIGER participants, believing that their collaborative efforts can help other nations facing similar geo-economic challenges.”“We are helping the companies understand how to stay leaders in this changing world,” says Paltsev. “We want to make sure that we are not painting an unrealistically rosy picture, or conveying that it will be easy to decarbonize. On the contrary, we want to stay realistic and try to show them both where they can make advances and where we see challenges.”The goal, Armstrong says, is not energy independence for Taiwan, but rather energy security. “Energy security requires diversity of supply,” he says. “So, you have a diverse set of suppliers, who are trusted trading partners, but it doesn’t mean you’re on your own. That’s the goal for Taiwan.”What will that mean, more specifically? Well, that’s what TIGER researchers aim to learn. “It probably means a mix of energy sources,” Armstrong says. “It could be that nuclear fission provides a core of energy that companies need for their industrial operations, it could be that they can import hydrogen in the form of ammonia or another carrier, and it could be that they leverage the renewable resources they have, together with storage technologies, to provide some pretty inexpensive energy for their manufacturing sector.”“We don’t know,” Armstrong adds. “But that’s what we’re looking at, to see if we can figure out a pathway that gets them to their goals. We are optimistic that we can get there.”The companies participating in the TIGER program include AcBel Polytech Inc., CDIB Capital Group / KGI Bank Co., Ltd.; Delta Electronics, Inc.; Fubon Financial Holding Co., Ltd.; Paul Hsu and Partners Co., Ltd.; Ta Ya Electric Wire & Cable Co., Ltd.; TCC Group Holdings Co. Ltd.; Walsin Lihwa Corporation; Wistron Corporation; and Zhen Ding Technology Holding, Ltd. More

  • 88 Shares84 Views

    in Energy

    Nanoscale transistors could enable more efficient electronics

    Silicon transistors, which are used to amplify and switch signals, are a critical component in most electronic devices, from smartphones to automobiles. But silicon semiconductor technology is held back by a fundamental physical limit that prevents transistors from operating below a certain voltage.This limit, known as “Boltzmann tyranny,” hinders the energy efficiency of computers and other electronics, especially with the rapid development of artificial intelligence technologies that demand faster computation.In an effort to overcome this fundamental limit of silicon, MIT researchers fabricated a different type of three-dimensional transistor using a unique set of ultrathin semiconductor materials.Their devices, featuring vertical nanowires only a few nanometers wide, can deliver performance comparable to state-of-the-art silicon transistors while operating efficiently at much lower voltages than conventional devices.“This is a technology with the potential to replace silicon, so you could use it with all the functions that silicon currently has, but with much better energy efficiency,” says Yanjie Shao, an MIT postdoc and lead author of a paper on the new transistors.The transistors leverage quantum mechanical properties to simultaneously achieve low-voltage operation and high performance within an area of just a few square nanometers. Their extremely small size would enable more of these 3D transistors to be packed onto a computer chip, resulting in fast, powerful electronics that are also more energy-efficient.“With conventional physics, there is only so far you can go. The work of Yanjie shows that we can do better than that, but we have to use different physics. There are many challenges yet to be overcome for this approach to be commercial in the future, but conceptually, it really is a breakthrough,” says senior author Jesús del Alamo, the Donner Professor of Engineering in the MIT Department of Electrical Engineering and Computer Science (EECS).They are joined on the paper by Ju Li, the Tokyo Electric Power Company Professor in Nuclear Engineering and professor of materials science and engineering at MIT; EECS graduate student Hao Tang; MIT postdoc Baoming Wang; and professors Marco Pala and David Esseni of the University of Udine in Italy. The research appears today in Nature Electronics.Surpassing siliconIn electronic devices, silicon transistors often operate as switches. Applying a voltage to the transistor causes electrons to move over an energy barrier from one side to the other, switching the transistor from “off” to “on.” By switching, transistors represent binary digits to perform computation.A transistor’s switching slope reflects the sharpness of the “off” to “on” transition. The steeper the slope, the less voltage is needed to turn on the transistor and the greater its energy efficiency.But because of how electrons move across an energy barrier, Boltzmann tyranny requires a certain minimum voltage to switch the transistor at room temperature.To overcome the physical limit of silicon, the MIT researchers used a different set of semiconductor materials — gallium antimonide and indium arsenide — and designed their devices to leverage a unique phenomenon in quantum mechanics called quantum tunneling.Quantum tunneling is the ability of electrons to penetrate barriers. The researchers fabricated tunneling transistors, which leverage this property to encourage electrons to push through the energy barrier rather than going over it.“Now, you can turn the device on and off very easily,” Shao says.But while tunneling transistors can enable sharp switching slopes, they typically operate with low current, which hampers the performance of an electronic device. Higher current is necessary to create powerful transistor switches for demanding applications.Fine-grained fabricationUsing tools at MIT.nano, MIT’s state-of-the-art facility for nanoscale research, the engineers were able to carefully control the 3D geometry of their transistors, creating vertical nanowire heterostructures with a diameter of only 6 nanometers. They believe these are the smallest 3D transistors reported to date.Such precise engineering enabled them to achieve a sharp switching slope and high current simultaneously. This is possible because of a phenomenon called quantum confinement.Quantum confinement occurs when an electron is confined to a space that is so small that it can’t move around. When this happens, the effective mass of the electron and the properties of the material change, enabling stronger tunneling of the electron through a barrier.Because the transistors are so small, the researchers can engineer a very strong quantum confinement effect while also fabricating an extremely thin barrier.“We have a lot of flexibility to design these material heterostructures so we can achieve a very thin tunneling barrier, which enables us to get very high current,” Shao says.Precisely fabricating devices that were small enough to accomplish this was a major challenge.“We are really into single-nanometer dimensions with this work. Very few groups in the world can make good transistors in that range. Yanjie is extraordinarily capable to craft such well-functioning transistors that are so extremely small,” says del Alamo.When the researchers tested their devices, the sharpness of the switching slope was below the fundamental limit that can be achieved with conventional silicon transistors. Their devices also performed about 20 times better than similar tunneling transistors.“This is the first time we have been able to achieve such sharp switching steepness with this design,” Shao adds.The researchers are now striving to enhance their fabrication methods to make transistors more uniform across an entire chip. With such small devices, even a 1-nanometer variance can change the behavior of the electrons and affect device operation. They are also exploring vertical fin-shaped structures, in addition to vertical nanowire transistors, which could potentially improve the uniformity of devices on a chip.“This work definitively steps in the right direction, significantly improving the broken-gap tunnel field effect transistor (TFET) performance. It demonstrates steep-slope together with a record drive-current. It highlights the importance of small dimensions, extreme confinement, and low-defectivity materials and interfaces in the fabricated broken-gap TFET. These features have been realized through a well-mastered and nanometer-size-controlled process,” says Aryan Afzalian, a principal member of the technical staff at the nanoelectronics research organization imec, who was not involved with this work.This research is funded, in part, by Intel Corporation. More

  • 125 Shares89 Views

    in Energy

    Smart handling of neutrons is crucial to fusion power success

    In fall 2009, when Ethan Peterson ’13 arrived at MIT as an undergraduate, he already had some ideas about possible career options. He’d always liked building things, even as a child, so he imagined his future work would involve engineering of some sort. He also liked physics. And he’d recently become intent on reducing our dependence on fossil fuels and simultaneously curbing greenhouse gas emissions, which made him consider studying solar and wind energy, among other renewable sources.Things crystallized for him in the spring semester of 2010, when he took an introductory course on nuclear fusion, taught by Anne White, during which he discovered that when a deuterium nucleus and a tritium nucleus combine to produce a helium nucleus, an energetic (14 mega electron volt) neutron — traveling at one-sixth the speed of light — is released. Moreover, 1020 (100 billion billion) of these neutrons would be produced every second that a 500-megawatt fusion power plant operates. “It was eye-opening for me to learn just how energy-dense the fusion process is,” says Peterson, who became the Class of 1956 Career Development Professor of nuclear science and engineering in July 2024. “I was struck by the richness and interdisciplinary nature of the fusion field. This was an engineering discipline where I could apply physics to solve a real-world problem in a way that was both interesting and beautiful.”He soon became a physics and nuclear engineering double major, and by the time he graduated from MIT in 2013, the U.S. Department of Energy (DoE) had already decided to cut funding for MIT’s Alcator C-Mod fusion project. In view of that facility’s impending closure, Peterson opted to pursue graduate studies at the University of Wisconsin. There, he acquired a basic science background in plasma physics, which is central not only to nuclear fusion but also to astrophysical phenomena such as the solar wind.When Peterson received his PhD from Wisconsin in 2019, nuclear fusion had rebounded at MIT with the launch, a year earlier, of the SPARC project — a collaborative effort being carried out with the newly founded MIT spinout Commonwealth Fusion Systems. He returned to his alma mater as a postdoc and then a research scientist in the Plasma Science and Fusion Center, taking his time, at first, to figure out how to best make his mark in the field.Minding your neutronsAround that time, Peterson was participating in a community planning process, sponsored by the DoE, that focused on critical gaps that needed to be closed for a successful fusion program. In the course of these discussions, he came to realize that inadequate attention had been paid to the handling of neutrons, which carry 80 percent of the energy coming out of a fusion reaction — energy that needs to be harnessed for electrical generation. However, these neutrons are so energetic that they can penetrate through many tens of centimeters of material, potentially undermining the structural integrity of components and damaging vital equipment such as superconducting magnets. Shielding is also essential for protecting humans from harmful radiation.One goal, Peterson says, is to minimize the number of neutrons that escape and, in so doing, to reduce the amount of lost energy. A complementary objective, he adds, “is to get neutrons to deposit heat where you want them to and to stop them from depositing heat where you don’t want them to.” These considerations, in turn, can have a profound influence on fusion reactor design. This branch of nuclear engineering, called neutronics — which analyzes where neutrons are created and where they end up going — has become Peterson’s specialty.It was never a high-profile area of research in the fusion community — as plasma physics, for example, has always garnered more of the spotlight and more of the funding. That’s exactly why Peterson has stepped up. “The impacts of neutrons on fusion reactor design haven’t been a high priority for a long time,” he says. “I felt that some initiative needed to be taken,” and that prompted him to make the switch from plasma physics to neutronics. It has been his principal focus ever since — as a postdoc, a research scientist, and now as a faculty member.A code to design byThe best way to get a neutron to transfer its energy is to make it collide with a light atom. Lithium, with an atomic number of three, or lithium-containing materials are normally good choices — and necessary for producing tritium fuel. The placement of lithium “blankets,” which are intended to absorb energy from neutrons and produce tritium, “is a critical part of the design of fusion reactors,” Peterson says. High-density materials, such as lead and tungsten, can be used, conversely, to block the passage of neutrons and other types of radiation. “You might want to layer these high- and low-density materials in a complicated way that isn’t immediately intuitive” he adds. Determining which materials to put where — and of what thickness and mass — amounts to a tricky optimization problem, which will affect the size, cost, and efficiency of a fusion power plant.To that end, Peterson has developed modelling tools that can make analyses of these sorts easier and faster, thereby facilitating the design process. “This has traditionally been the step that takes the longest time and causes the biggest holdups,” he says. The models and algorithms that he and his colleagues are devising are general enough, moreover, to be compatible with a diverse range of fusion power plant concepts, including those that use magnets or lasers to confine the plasma.Now that he’s become a professor, Peterson is in a position to introduce more people to nuclear engineering, and to neutronics in particular. “I love teaching and mentoring students, sharing the things I’m excited about,” he says. “I was inspired by all the professors I had in physics and nuclear engineering at MIT, and I hope to give back to the community in the same way.”He also believes that if you are going to work on fusion, there is no better place to be than MIT, “where the facilities are second-to-none. People here are extremely innovative and passionate. And the sheer number of people who excel in their fields is staggering.” Great ideas can sometimes be sparked by off-the-cuff conversations in the hallway — something that happens more frequently than you expect, Peterson remarks. “All of these things taken together makes MIT a very special place.” More