Energy

Subterms

    More stories

    • 88 Shares169 Views

      in Energy

      More durable metals for fusion power reactors

      by

      For many decades, nuclear fusion power has been viewed as the ultimate energy source. A fusion power plant could generate carbon-free energy at a scale needed to address climate change. And it could be fueled by deuterium recovered from an essentially endless source — seawater.Decades of work and billions of dollars in research funding have yielded many advances, but challenges remain. To Ju Li, the TEPCO Professor in Nuclear Science and Engineering and a professor of materials science and engineering at MIT, there are still two big challenges. The first is to build a fusion power plant that generates more energy than is put into it; in other words, it produces a net output of power. Researchers worldwide are making progress toward meeting that goal.The second challenge that Li cites sounds straightforward: “How do we get the heat out?” But understanding the problem and finding a solution are both far from obvious.Research in the MIT Energy Initiative (MITEI) includes development and testing of advanced materials that may help address those challenges, as well as many other challenges of the energy transition. MITEI has multiple corporate members that have been supporting MIT’s efforts to advance technologies required to harness fusion energy.The problem: An abundance of helium, a destructive forceKey to a fusion reactor is a superheated plasma — an ionized gas — that’s reacting inside a vacuum vessel. As light atoms in the plasma combine to form heavier ones, they release fast neutrons with high kinetic energy that shoot through the surrounding vacuum vessel into a coolant. During this process, those fast neutrons gradually lose their energy by causing radiation damage and generating heat. The heat that’s transferred to the coolant is eventually used to raise steam that drives an electricity-generating turbine.The problem is finding a material for the vacuum vessel that remains strong enough to keep the reacting plasma and the coolant apart, while allowing the fast neutrons to pass through to the coolant. If one considers only the damage due to neutrons knocking atoms out of position in the metal structure, the vacuum vessel should last a full decade. However, depending on what materials are used in the fabrication of the vacuum vessel, some projections indicate that the vacuum vessel will last only six to 12 months. Why is that? Today’s nuclear fission reactors also generate neutrons, and those reactors last far longer than a year.The difference is that fusion neutrons possess much higher kinetic energy than fission neutrons do, and as they penetrate the vacuum vessel walls, some of them interact with the nuclei of atoms in the structural material, giving off particles that rapidly turn into helium atoms. The result is hundreds of times more helium atoms than are present in a fission reactor. Those helium atoms look for somewhere to land — a place with low “embedding energy,” a measure that indicates how much energy it takes for a helium atom to be absorbed. As Li explains, “The helium atoms like to go to places with low helium embedding energy.” And in the metals used in fusion vacuum vessels, there are places with relatively low helium embedding energy — namely, naturally occurring openings called grain boundaries.Metals are made up of individual grains inside which atoms are lined up in an orderly fashion. Where the grains come together there are gaps where the atoms don’t line up as well. That open space has relatively low helium embedding energy, so the helium atoms congregate there. Worse still, helium atoms have a repellent interaction with other atoms, so the helium atoms basically push open the grain boundary. Over time, the opening grows into a continuous crack, and the vacuum vessel breaks.That congregation of helium atoms explains why the structure fails much sooner than expected based just on the number of helium atoms that are present. Li offers an analogy to illustrate. “Babylon is a city of a million people. But the claim is that 100 bad persons can destroy the whole city — if all those bad persons work at the city hall.” The solution? Give those bad persons other, more attractive places to go, ideally in their own villages.To Li, the problem and possible solution are the same in a fusion reactor. If many helium atoms go to the grain boundary at once, they can destroy the metal wall. The solution? Add a small amount of a material that has a helium embedding energy even lower than that of the grain boundary. And over the past two years, Li and his team have demonstrated — both theoretically and experimentally — that their diversionary tactic works. By adding nanoscale particles of a carefully selected second material to the metal wall, they’ve found they can keep the helium atoms that form from congregating in the structurally vulnerable grain boundaries in the metal.Looking for helium-absorbing compoundsTo test their idea, So Yeon Kim ScD ’23 of the Department of Materials Science and Engineering and Haowei Xu PhD ’23 of the Department of Nuclear Science and Engineering acquired a sample composed of two materials, or “phases,” one with a lower helium embedding energy than the other. They and their collaborators then implanted helium ions into the sample at a temperature similar to that in a fusion reactor and watched as bubbles of helium formed. Transmission electron microscope images confirmed that the helium bubbles occurred predominantly in the phase with the lower helium embedding energy. As Li notes, “All the damage is in that phase — evidence that it protected the phase with the higher embedding energy.”Having confirmed their approach, the researchers were ready to search for helium-absorbing compounds that would work well with iron, which is often the principal metal in vacuum vessel walls. “But calculating helium embedding energy for all sorts of different materials would be computationally demanding and expensive,” says Kim. “We wanted to find a metric that is easy to compute and a reliable indicator of helium embedding energy.”They found such a metric: the “atomic-scale free volume,” which is basically the maximum size of the internal vacant space available for helium atoms to potentially settle. “This is just the radius of the largest sphere that can fit into a given crystal structure,” explains Kim. “It is a simple calculation.” Examination of a series of possible helium-absorbing ceramic materials confirmed that atomic free volume correlates well with helium embedding energy. Moreover, many of the ceramics they investigated have higher free volume, thus lower embedding energy, than the grain boundaries do.However, in order to identify options for the nuclear fusion application, the screening needed to include some other factors. For example, in addition to the atomic free volume, a good second phase must be mechanically robust (able to sustain a load); it must not get very radioactive with neutron exposure; and it must be compatible — but not too cozy — with the surrounding metal, so it disperses well but does not dissolve into the metal. “We want to disperse the ceramic phase uniformly in the bulk metal to ensure that all grain boundary regions are close to the dispersed ceramic phase so it can provide protection to those regions,” says Li. “The two phases need to coexist, so the ceramic won’t either clump together or totally dissolve in the iron.”Using their analytical tools, Kim and Xu examined about 50,000 compounds and identified 750 potential candidates. Of those, a good option for inclusion in a vacuum vessel wall made mainly of iron was iron silicate.Experimental testingThe researchers were ready to examine samples in the lab. To make the composite material for proof-of-concept demonstrations, Kim and collaborators dispersed nanoscale particles of iron silicate into iron and implanted helium into that composite material. She took X-ray diffraction (XRD) images before and after implanting the helium and also computed the XRD patterns. The ratio between the implanted helium and the dispersed iron silicate was carefully controlled to allow a direct comparison between the experimental and computed XRD patterns. The measured XRD intensity changed with the helium implantation exactly as the calculations had predicted. “That agreement confirms that atomic helium is being stored within the bulk lattice of the iron silicate,” says Kim.To follow up, Kim directly counted the number of helium bubbles in the composite. In iron samples without the iron silicate added, grain boundaries were flanked by many helium bubbles. In contrast, in the iron samples with the iron silicate ceramic phase added, helium bubbles were spread throughout the material, with many fewer occurring along the grain boundaries. Thus, the iron silicate had provided sites with low helium-embedding energy that lured the helium atoms away from the grain boundaries, protecting those vulnerable openings and preventing cracks from opening up and causing the vacuum vessel to fail catastrophically.The researchers conclude that adding just 1 percent (by volume) of iron silicate to the iron walls of the vacuum vessel will cut the number of helium bubbles in half and also reduce their diameter by 20 percent — “and having a lot of small bubbles is OK if they’re not in the grain boundaries,” explains Li.Next stepsThus far, Li and his team have gone from computational studies of the problem and a possible solution to experimental demonstrations that confirm their approach. And they’re well on their way to commercial fabrication of components. “We’ve made powders that are compatible with existing commercial 3D printers and are preloaded with helium-absorbing ceramics,” says Li. The helium-absorbing nanoparticles are well dispersed and should provide sufficient helium uptake to protect the vulnerable grain boundaries in the structural metals of the vessel walls. While Li confirms that there’s more scientific and engineering work to be done, he, along with Alexander O’Brien PhD ’23 of the Department of Nuclear Science and Engineering and Kang Pyo So, a former postdoc in the same department, have already developed a startup company that’s ready to 3D print structural materials that can meet all the challenges faced by the vacuum vessel inside a fusion reactor.This research was supported by Eni S.p.A. through the MIT Energy Initiative. Additional support was provided by a Kwajeong Scholarship; the U.S. Department of Energy (DOE) Laboratory Directed Research and Development program at Idaho National Laboratory; U.S. DOE Lawrence Livermore National Laboratory; and Creative Materials Discovery Program through the National Research Foundation of Korea. More

    • 113 Shares179 Views

      in Energy

      MIT engineers design tiny batteries for powering cell-sized robots

      by

      A tiny battery designed by MIT engineers could enable the deployment of cell-sized, autonomous robots for drug delivery within in the human body, as well as other applications such as locating leaks in gas pipelines.The new battery, which is 0.1 millimeters long and 0.002 millimeters thick — roughly the thickness of a human hair — can capture oxygen from air and use it to oxidize zinc, creating a current of up to 1 volt. That is enough to power a small circuit, sensor, or actuator, the researchers showed.“We think this is going to be very enabling for robotics,” says Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering at MIT and the senior author of the study. “We’re building robotic functions onto the battery and starting to put these components together into devices.”Ge Zhang PhD ’22 and Sungyun Yang, an MIT graduate student, are the lead author of the paper, which appears in Science Robotics.Powered by batteriesFor several years, Strano’s lab has been working on tiny robots that can sense and respond to stimuli in their environment. One of the major challenges in developing such tiny robots is making sure that they have enough power.Other researchers have shown that they can power microscale devices using solar power, but the limitation to that approach is that the robots must have a laser or another light source pointed at them at all times. Such devices are known as “marionettes” because they are controlled by an external power source. Putting a power source such as a battery inside these tiny devices could free them to roam much farther.“The marionette systems don’t really need a battery because they’re getting all the energy they need from outside,” Strano says. “But if you want a small robot to be able to get into spaces that you couldn’t access otherwise, it needs to have a greater level of autonomy. A battery is essential for something that’s not going to be tethered to the outside world.”To create robots that could become more autonomous, Strano’s lab decided to use a type of battery known as a zinc-air battery. These batteries, which have a longer lifespan than many other types of batteries due to their high energy density, are often used in hearing aids.The battery that they designed consists of a zinc electrode connected to a platinum electrode, embedded into a strip of a polymer called SU-8, which is commonly used for microelectronics. When these electrodes interact with oxygen molecules from the air, the zinc becomes oxidized and releases electrons that flow to the platinum electrode, creating a current.In this study, the researchers showed that this battery could provide enough energy to power an actuator — in this case, a robotic arm that can be raised and lowered. The battery could also power a memristor, an electrical component that can store memories of events by changing its electrical resistance, and a clock circuit, which allows robotic devices to keep track of time.The battery also provides enough power to run two different types of sensors that change their electrical resistance when they encounter chemicals in the environment. One of the sensors is made from atomically thin molybdenum disulfide and the other from carbon nanotubes.“We’re making the basic building blocks in order to build up functions at the cellular level,” Strano says.Robotic swarmsIn this study, the researchers used a wire to connect their battery to an external device, but in future work they plan to build robots in which the battery is incorporated into a device.“This is going to form the core of a lot of our robotic efforts,” Strano says. “You can build a robot around an energy source, sort of like you can build an electric car around the battery.”One of those efforts revolves around designing tiny robots that could be injected into the human body, where they could seek out a target site and then release a drug such as insulin. For use in the human body, the researchers envision that the devices would be made of biocompatible materials that would break apart once they were no longer needed.The researchers are also working on increasing the voltage of the battery, which may enable additional applications.The research was funded by the U.S. Army Research Office, the U.S. Department of Energy, the National Science Foundation, and a MathWorks Engineering Fellowship. More

    • 150 Shares169 Views

      in Energy

      D-Lab off-grid brooder saves chicks and money using locally manufactured thermal batteries

      by

      MIT D-Lab students and instructors are improving the efficacy and economics of a brooder technology for newborn chicks that utilizes a practical, local resource: beeswax.Developed through participatory design with agricultural partners in Cameroon, their Off-Grid Brooder is a solution aimed at improving the profitability of the African nation’s small- and medium-scale poultry farms. Since it is common for smallholders in places with poor electricity supply to tend open fires overnight to keep chicks warm, the invention might also let farmers catch up on their sleep.“The target is eight hours. If farmers can sustain the warmth for eight hours, then they get to sleep,” says D-Lab instructor and former student Ahmad (Zak) Zakka SM ’23, who traveled to Cameroon in May to work on implementing brooder improvements tested at the D-Lab, along with D-Lab students, collaborators from African Solar Generation (ASG), and the African Diaspora Council of Switzerland – Branch Cameroon (CDAS–BC).Poultry farming is heavily concentrated in lower- and middle-income countries, where it is an important component of rural economies and provides an inexpensive source of protein for residents. Raising chickens is fraught with economic risk, however, largely because it is hard for small-scale farmers to keep newborn chicks warm enough to survive (33 to 35 degrees Celsius, or 91 to 95 degrees Fahrenheit, depending on age). After the cost of feed, firewood used to heat the chick space is the biggest input for rural poultry farmers.According to D-Lab researchers, an average smallholder in Cameroon using traditional brooding methods spends $17 per month on firewood, achieves a 10 percent profit margin, and experiences chick mortality that can be as high as a total loss due to overheating or insufficient heat. The Off-Grid Brooder is designed to replace open fires with inexpensive, renewable, and locally available beeswax — a phase-change material used to make thermal batteries.ASG initially developed a brooder technology, the SolarBox, that used photovoltaic panels and electric batteries to power incandescent bulbs. While this provided effective heating, it was prohibitively expensive and difficult to maintain. In 2020, students from the D-Lab Energy class took on the challenge of reducing the cost and complexity of the SolarBox heating system to make it more accessible to small farmers in Cameroon. Through participatory design — a collaborative approach that involves all stakeholders in early stages of the design process — the team discovered a unique solution. Beeswax stored in a used glass container (such as a mayonnaise jar) is melted using a double boiler over a fire and then installed inside insulated brooder boxes alongside the chicks. As the beeswax cools and solidifies, it releases heat for several hours, keeping the brooder within the temperature range that chicks need to grow and develop. Farmers can then recharge the cooled wax batteries and repeat the process again and again. “The big challenge was how to get heat,” says D-Lab Research Scientist Daniel Sweeney, who, with Zakka, co-teaches two D-Lab classes, 2.651/EC.711 (Introduction to Energy in Global Development), and 2.652/EC.712 (Applications of Energy in Global Development). “Decoupling the heat supplied by biomass (wood) from the heat the chicks need at night in the brooder, that’s the core of the innovation here.”D-Lab instructors, researchers, and students have tested and tuned the system with partners in Cameroon. A research box constructed during a D-Lab trip to Cameroon in January 2023 worked well, but was “very expensive to build,” Zakka says. “The research box was a proof of concept in the field. The next step was to figure out how to make it affordable,” he continues.A new brooder box, made entirely of locally sourced recycled materials at 5 percent of the cost of the research prototype, was developed during D-Lab’s January 2024 trip to Cameroon. Designed and produced in collaboration with CDAS-BC, the new brooder is much more affordable, but its functionality still needs fine-tuning. From late-May through mid-June, the D-Lab team, led by Zakka, worked with Cameroonian collaborators to improve the system again. This time, they assessed the efficacy of using straw, a readily available and low-cost material, arranged in panels to insulate the brooder box.The MIT team was hosted by CDAS-BC, including its president and founder Carole Erlemann Mengue and secretary and treasurer Kathrin Witschi, who operate an organic poultry farm in Afambassi, Cameroon. “The students will experiment with the box and try to improve the insulation of the box without neglecting that the chicks will need ventilation,” they say.In addition, the CDAS-BC partners say that they hoped to explore increasing the number of chicks that the box can keep warm. “If the system could heat 500 to 1,000 chicks at a time,” they note, “it would help farmers save firewood, to sleep through the night, and to minimize the risk of fire in the building and the risk of stepping on chicks while replacing firewood.” Earlier this spring, Erlemann Mengue and Witschi tested the low-cost Off-Grid Brooder Box, which can hold 30 to 40 chicks in its current design.“They were very interested in partnering with us to evaluate the technology. They are running the tests and doing a lot of technical measurement to track the temperature inside the brooder over time,” says Sweeney, adding that the CDAS-BC partners are amassing datasets that they send to the MIT D-Lab team. Sweeney and Zakka, along with PhD candidate Aly Kombargi, who worked on the research box in Cameroon last year, hope to not only improve the functionality of the Off-Grid Poultry Brooder but also broaden its use beyond Cameroon.“The goal of our trip was to have a working prototype, and the goal since then has been to scale this up,” Kombargi says. “It’s absolutely scalable.”Concurring that “the technology should work across developing countries in small-scale poultry sectors,” Zakka says this spring’s D-Lab trip included workshops for area poultry farmers to teach them about benefits of the Off-Grid Brooder and how to make their own. “I’m excited to see if we can get people excited about pushing this as a business … to see if they would build and sell it to other people in the community,” Zakka says.Adds Sweeney, “This isn’t rocket science. If we have some guidance and some open-source information we could share, I’m pretty sure (farmers) could put them together on their own.”Already, he says, partners identified through MIT’s networks in Zambia and Uganda are building their own brooders based on the D-Lab design.MIT’s Abdul Latif Jameel Water and Food Systems Lab (J-WAFS), which supports research, innovation, and cross-disciplinary collaborations involving water and food systems, awarded the Off-Grid Brooder project a $25,000 research and development grant in 2022. The program is “pleased that the project’s approach was grounded in engagement with MIT students and community collaborators,” says Executive Director Renee Robins. “The participatory design process helped produce innovative prototypes that are already making positive impacts for smallholder poultry farmers.”That process and the very real impact on communities in Cameroon is what draws students to the project and keeps them committed.Sweeney says a recent D-Lab design review for the chick brooder highlighted that the project continued to attract the attention and curiosity of students who participated in earlier stages and still want to be involved.“There’s something about this project. There’s this whole tribe of students that are still active on the broader project,” he says. “There’s something about it.” More

    • 50 Shares149 Views

      in Energy

      Going Dutch on climate

      by

      When MIT senior Rudiba Laiba saw that stores in the Netherlands eschewed plastic bags to save the planet, her first thought was, “that doesn’t happen in Bangladesh.”Laiba is one of eight MIT students who traveled to the Netherlands in June as part of an MIT Energy Initiative (MITEI)-sponsored trip to experience first-hand the country’s approach to the energy transition. The Netherlands aims to be carbon neutral by 2050, making it one of the top 10 countries leading the charge on climate change, according to U.S. News and World Report.MITEI sponsored the week-long trip to allow undergraduate and graduate students to collaboratively explore clean energy efforts with researchers, corporate leaders, and nongovernmental organizations. The students heard about projects ranging from creating hydrogen pipelines in the North Sea to climate-proofing a fuel-guzzling, asphalt-dense neighborhood.Felipe Abreu from Kissimmee, Florida, a rising second-year student studying materials science and engineering, is working this summer on ways to melt and reuse metal scraps discarded in manufacturing processes. “When MITEI put out this notice about visiting the Netherlands, I wanted to see if there were more advanced approaches to renewable energy that I’d never been exposed to,” Abreu says.Laiba notes that her native Bangladesh has not yet achieved the Netherlands’ nearly universal buy-in to tackling climate change, even though this South Asian country, like the Netherlands, is particularly vulnerable to rising sea levels due to topography and high population density.Laiba, who spent part of her childhood in New York City and lived in Bangladesh from ages 8 to 18, calls Bangladesh “on the front lines of climate change.“Even if I didn’t want to care about climate change, I had to, because I would see the effects of it,” she says.Key playersThe MIT students conducted hands-on exercises on how to switch from traditional energy sources to zero-carbon technologies. “We talked a lot about infrastructure, particularly how to repurpose natural gas infrastructure for hydrogen,” says Antje Danielson, director of education at MITEI, who led the trip with Em Schule, MITEI research and programming assistant. “The students were challenged to grapple with real-world decision-making.”The northern section of the Netherlands is known as the “hydrogen valley” of Europe. At the University of Groningen and Hanze University School of Applied Sciences, also in Groningen, the students heard about how the region profiles itself as a world capital for the energy transition through its push toward a hydrogen-based economy and its state-of-the-art global climate models.Erick Liang, a rising junior from Boston’s Roslindale neighborhood pursuing a dual major in nuclear science and engineering and physics, was intrigued by a massive wind farm in the port city of Eemshaven, one of the group’s first stops in the north of the country. “It was impressive as an engineering challenge, because they must have figured out ways to cheaply and effectively manufacture all these wind turbines,” he says.They visited German energy company RWE, which is generating 15 percent of Eemshaven’s electricity from biomass, replacing coal.Laiba, who is majoring in molecular biology and electrical engineering and computer science with a minor in business management, was intrigued by a presentation on biofuels. “It piqued my interest to see if they would use biomass on a large scale” because of the challenges and unpredictability associated with it as a fuel source.In Paddepoel, the students toured the first of several neighborhoods that once lacked greenery and used fossil fuel-based heating systems and now aim to generate more energy than they consume.“The students got to see what the size of the district heating pipes would be, and how they go through people’s gardens into the houses. We talked about the physical impact on the neighborhood of installing these pipes, as well as the potential social and political implications connected to a really difficult transition like this,” Danielson says.Going greenGreen hydrogen promises to be a key player in the energy transition, and Netherlands officials say they have committed to the new infrastructure and business models needed to move ahead with hydrogen as a fuel source.The students explored how green hydrogen differs from fossil fuel-generated hydrogen. They saw how Dutch companies grappled with siting hydrogen production facilities and handling hydrogen as a gas, which, unlike natural gas, does not yet have a detectable artificial odor. The students heard from energy network operator Gasunie about the science and engineering behind repurposing existing natural gas pipelines for a hydrogen network in the North Sea, and were challenged to solve the puzzle of combining hydrogen production with offshore wind energy. In the port of Rotterdam, they saw how the startup Battolyser Systems — which is working with Delft University of Technology on an electrolysis device that splits water into hydrogen and oxygen and doubles as a battery — is transitioning from lab bench to market.Laiba was impressed by how much capital was going into high-risk ventures and startups, “not only because they’re trying to make something revolutionary, but also because society needs to accept and use” their products.Abreu says that at Battolyser Systems, “I saw people my age on the forefront of green hydrogen, trying to make a difference.”The students visited the Global Center on Adaptation’s carbon-neutral floating offices and learned how this international organization supports climate adaptation actions around the world and the practice of mitigation.Also in Rotterdam, international marine contractor Van Oord took students to view a ship that installs wind turbines and explained how their new technology reduces the sound shockwave impact of the installations on marine life.At the Port of Rotterdam, the students heard about the challenges faced by Europe’s largest port in terms of global shipping and choosing the fuels of the future. The speaker tasked the MIT students with coming up with a plan to transition the privately owned, owner-inhabited barges that ply the region’s inland waterways to a zero-carbon system.“The Port Authority uses this exercise to illustrate the enormous complexity faced by companies in the energy transition,” Danielson says. “The fact that our students performed really well on the spot shows that we are doing something right at MIT.”Defining a path forwardLiang, Abreu, and Laiba were struck by how the Netherlands has come together as a country over climate change. “In the U.S., a lot of people disagree with the concept of climate change as a whole,” Liang says. “But in the Netherlands, everyone is on the same page that this is an issue that we should be working toward. They’re capable of seeing a path forward and trying to take action whenever possible.”Liang, a member of the MIT Solar Electric Vehicle Team, is doing undergraduate research sponsored by MITEI this summer, working to accelerate fusion manufacturing and development at the MIT Plasma Science and Fusion Center. He’s improving 3D printing processes to manufacture components that can accommodate the high temperatures and small space within a tokamak reactor, which uses magnetic fields to confine plasma and produce controlled thermonuclear fusion.“I personally would like to try finding a new solution” to achieving carbon neutrality, he says. That solution, to Liang, is fusion energy, with some entities hoping to demonstrate net energy gain through fusion in the next five years.Laiba is a researcher with the MIT Office of Sustainability, looking at ways to quantify and reduce the level of MIT’s Scope 3 greenhouse gas emissions. Scope 3 emissions are tied to the purchase of goods that use fossil fuels in their manufacture. She says, ​“Whatever I decide to do in the future will involve making a more sustainable future. And to me, renewable energy is the driving force behind that.”In the Netherlands, she says, “what we learned through the entire trip was that renewable energy powers the country to a large amount. Things I could see tangibly was Starbucks having paper cups even for our iced drinks, which I think would flop very hard in the U.S. I don’t think society’s ready for that yet.”Abreu says, “In America, sustainability has always been in the back seat while other things take the forefront. So going to a country where everybody you talk to has a stake (in sustainability) and actually cares, and they’re all pushing together for this common goal, it was inspiring. It gave me hope.” More

    • 100 Shares99 Views

      in Energy

      Proton-conducting materials could enable new green energy technologies

      by

      As the name suggests, most electronic devices today work through the movement of electrons. But materials that can efficiently conduct protons — the nucleus of the hydrogen atom — could be key to a number of important technologies for combating global climate change.Most proton-conducting inorganic materials available now require undesirably high temperatures to achieve sufficiently high conductivity. However, lower-temperature alternatives could enable a variety of technologies, such as more efficient and durable fuel cells to produce clean electricity from hydrogen, electrolyzers to make clean fuels such as hydrogen for transportation, solid-state proton batteries, and even new kinds of computing devices based on iono-electronic effects.In order to advance the development of proton conductors, MIT engineers have identified certain traits of materials that give rise to fast proton conduction. Using those traits quantitatively, the team identified a half-dozen new candidates that show promise as fast proton conductors. Simulations suggest these candidates will perform far better than existing materials, although they still need to be conformed experimentally. In addition to uncovering potential new materials, the research also provides a deeper understanding at the atomic level of how such materials work.The new findings are described in the journal Energy and Environmental Sciences, in a paper by MIT professors Bilge Yildiz and Ju Li, postdocs Pjotrs Zguns and Konstantin Klyukin, and their collaborator Sossina Haile and her students from Northwestern University. Yildiz is the Breene M. Kerr Professor in the departments of Nuclear Science and Engineering, and Materials Science and Engineering.“Proton conductors are needed in clean energy conversion applications such as fuel cells, where we use hydrogen to produce carbon dioxide-free electricity,” Yildiz explains. “We want to do this process efficiently, and therefore we need materials that can transport protons very fast through such devices.”Present methods of producing hydrogen, for example steam methane reforming, emit a great deal of carbon dioxide. “One way to eliminate that is to electrochemically produce hydrogen from water vapor, and that needs very good proton conductors,” Yildiz says. Production of other important industrial chemicals and potential fuels, such as ammonia, can also be carried out through efficient electrochemical systems that require good proton conductors.But most inorganic materials that conduct protons can only operate at temperatures of 200 to 600 degrees Celsius (roughly 450 to 1,100 Fahrenheit), or even higher. Such temperatures require energy to maintain and can cause degradation of materials. “Going to higher temperatures is not desirable because that makes the whole system more challenging, and the material durability becomes an issue,” Yildiz says. “There is no good inorganic proton conductor at room temperature.” Today, the only known room-temperature proton conductor is a polymeric material that is not practical for applications in computing devices because it can’t easily be scaled down to the nanometer regime, she says.To tackle the problem, the team first needed to develop a basic and quantitative understanding of exactly how proton conduction works, taking a class of inorganic proton conductors, called solid acids. “One has to first understand what governs proton conduction in these inorganic compounds,” she says. While looking at the materials’ atomic configurations, the researchers identified a pair of characteristics that directly relates to the materials’ proton-carrying potential.As Yildiz explains, proton conduction first involves a proton “hopping from a donor oxygen atom to an acceptor oxygen. And then the environment has to reorganize and take the accepted proton away, so that it can hop to another neighboring acceptor, enabling long-range proton diffusion.” This process happens in many inorganic solids, she says. Figuring out how that last part works — how the atomic lattice gets reorganized to take the accepted proton away from the original donor atom — was a key part of this research, she says.The researchers used computer simulations to study a class of materials called solid acids that become good proton conductors above 200 degrees Celsius. This class of materials has a substructure called the polyanion group sublattice, and these groups have to rotate and take the proton away from its original site so it can then transfer to other sites. The researchers were able to identify the phonons that contribute to the flexibility of this sublattice, which is essential for proton conduction. Then they used this information to comb through vast databases of theoretically and experimentally possible compounds, in search of better proton conducting materials.As a result, they found solid acid compounds that are promising proton conductors and that have been developed and produced for a variety of different applications but never before studied as proton conductors; these compounds turned out to have just the right characteristics of lattice flexibility. The team then carried out computer simulations of how the specific materials they identified in their initial screening would perform under relevant temperatures, to confirm their suitability as proton conductors for fuel cells or other uses. Sure enough, they found six promising materials, with predicted proton conduction speeds faster than the best existing solid acid proton conductors.“There are uncertainties in these simulations,” Yildiz cautions. “I don’t want to say exactly how much higher the conductivity will be, but these look very promising. Hopefully this motivates the experimental field to try to synthesize them in different forms and make use of these compounds as proton conductors.”Translating these theoretical findings into practical devices could take some years, she says. The likely first applications would be for electrochemical cells to produce fuels and chemical feedstocks such as hydrogen and ammonia, she says.The work was supported by the U.S. Department of Energy, the Wallenberg Foundation, and the U.S. National Science Foundation. More

    • 113 Shares129 Views

      in Energy

      AI method radically speeds predictions of materials’ thermal properties

      by

      It is estimated that about 70 percent of the energy generated worldwide ends up as waste heat.If scientists could better predict how heat moves through semiconductors and insulators, they could design more efficient power generation systems. However, the thermal properties of materials can be exceedingly difficult to model.The trouble comes from phonons, which are subatomic particles that carry heat. Some of a material’s thermal properties depend on a measurement called the phonon dispersion relation, which can be incredibly hard to obtain, let alone utilize in the design of a system.A team of researchers from MIT and elsewhere tackled this challenge by rethinking the problem from the ground up. The result of their work is a new machine-learning framework that can predict phonon dispersion relations up to 1,000 times faster than other AI-based techniques, with comparable or even better accuracy. Compared to more traditional, non-AI-based approaches, it could be 1 million times faster.This method could help engineers design energy generation systems that produce more power, more efficiently. It could also be used to develop more efficient microelectronics, since managing heat remains a major bottleneck to speeding up electronics.“Phonons are the culprit for the thermal loss, yet obtaining their properties is notoriously challenging, either computationally or experimentally,” says Mingda Li, associate professor of nuclear science and engineering and senior author of a paper on this technique.Li is joined on the paper by co-lead authors Ryotaro Okabe, a chemistry graduate student; and Abhijatmedhi Chotrattanapituk, an electrical engineering and computer science graduate student; Tommi Jaakkola, the Thomas Siebel Professor of Electrical Engineering and Computer Science at MIT; as well as others at MIT, Argonne National Laboratory, Harvard University, the University of South Carolina, Emory University, the University of California at Santa Barbara, and Oak Ridge National Laboratory. The research appears in Nature Computational Science.Predicting phononsHeat-carrying phonons are tricky to predict because they have an extremely wide frequency range, and the particles interact and travel at different speeds.A material’s phonon dispersion relation is the relationship between energy and momentum of phonons in its crystal structure. For years, researchers have tried to predict phonon dispersion relations using machine learning, but there are so many high-precision calculations involved that models get bogged down.“If you have 100 CPUs and a few weeks, you could probably calculate the phonon dispersion relation for one material. The whole community really wants a more efficient way to do this,” says Okabe.The machine-learning models scientists often use for these calculations are known as graph neural networks (GNN). A GNN converts a material’s atomic structure into a crystal graph comprising multiple nodes, which represent atoms, connected by edges, which represent the interatomic bonding between atoms.While GNNs work well for calculating many quantities, like magnetization or electrical polarization, they are not flexible enough to efficiently predict an extremely high-dimensional quantity like the phonon dispersion relation. Because phonons can travel around atoms on X, Y, and Z axes, their momentum space is hard to model with a fixed graph structure.To gain the flexibility they needed, Li and his collaborators devised virtual nodes.They create what they call a virtual node graph neural network (VGNN) by adding a series of flexible virtual nodes to the fixed crystal structure to represent phonons. The virtual nodes enable the output of the neural network to vary in size, so it is not restricted by the fixed crystal structure.Virtual nodes are connected to the graph in such a way that they can only receive messages from real nodes. While virtual nodes will be updated as the model updates real nodes during computation, they do not affect the accuracy of the model.“The way we do this is very efficient in coding. You just generate a few more nodes in your GNN. The physical location doesn’t matter, and the real nodes don’t even know the virtual nodes are there,” says Chotrattanapituk.Cutting out complexitySince it has virtual nodes to represent phonons, the VGNN can skip many complex calculations when estimating phonon dispersion relations, which makes the method more efficient than a standard GNN. The researchers proposed three different versions of VGNNs with increasing complexity. Each can be used to predict phonons directly from a material’s atomic coordinates.Because their approach has the flexibility to rapidly model high-dimensional properties, they can use it to estimate phonon dispersion relations in alloy systems. These complex combinations of metals and nonmetals are especially challenging for traditional approaches to model.The researchers also found that VGNNs offered slightly greater accuracy when predicting a material’s heat capacity. In some instances, prediction errors were two orders of magnitude lower with their technique.A VGNN could be used to calculate phonon dispersion relations for a few thousand materials in just a few seconds with a personal computer, Li says.This efficiency could enable scientists to search a larger space when seeking materials with certain thermal properties, such as superior thermal storage, energy conversion, or superconductivity.Moreover, the virtual node technique is not exclusive to phonons, and could also be used to predict challenging optical and magnetic properties.In the future, the researchers want to refine the technique so virtual nodes have greater sensitivity to capture small changes that can affect phonon structure.“Researchers got too comfortable using graph nodes to represent atoms, but we can rethink that. Graph nodes can be anything. And virtual nodes are a very generic approach you could use to predict a lot of high-dimensional quantities,” Li says.“The authors’ innovative approach significantly augments the graph neural network description of solids by incorporating key physics-informed elements through virtual nodes, for instance, informing wave-vector dependent band-structures and dynamical matrices,” says Olivier Delaire, associate professor in the Thomas Lord Department of Mechanical Engineering and Materials Science at Duke University, who was not involved with this work. “I find that the level of acceleration in predicting complex phonon properties is amazing, several orders of magnitude faster than a state-of-the-art universal machine-learning interatomic potential. Impressively, the advanced neural net captures fine features and obeys physical rules. There is great potential to expand the model to describe other important material properties: Electronic, optical, and magnetic spectra and band structures come to mind.”This work is supported by the U.S. Department of Energy, National Science Foundation, a Mathworks Fellowship, a Sow-Hsin Chen Fellowship, the Harvard Quantum Initiative, and the Oak Ridge National Laboratory. More

    • 138 Shares159 Views

      in Energy

      Startup aims to transform the power grid with superconducting transmission lines

      by

      Last year in Woburn, Massachusetts, a power line was deployed across a 100-foot stretch of land. Passersby wouldn’t have found much interesting about the installation: The line was supported by standard utility poles, the likes of which most of us have driven by millions of times. In fact, the familiarity of the sight is a key part of the technology’s promise.The lines are designed to transport five to 10 times the amount of power of conventional transmission lines, using essentially the same footprint and voltage level. That will be key to helping them overcome the regulatory hurdles and community opposition that has made increasing transmission capacity nearly impossible across large swaths of the globe, particularly in America and Europe, where new power distribution systems play a vital role in the shift to renewable energy and the resilience of the grid.The lines are the product of years of work by the startup VEIR, which was co-founded by Tim Heidel ’05, SM ’06, SM ’09, PhD ’10. They make use of superconducting cables and a proprietary cooling system that will enable initial transmission capacity up to 400 megawatts and, in future versions, up to several gigawatts.“We can deploy much higher power levels at much lower voltage, and so we can deploy the same high power but with a footprint and visual impact that is far less intrusive, and therefore can overcome a lot of the public opposition as well as siting and permitting barriers,” Heidel says.VEIR’s solution comes at a time when more than 10,000 renewable energy projects at various stages of development are seeking permission to connect to U.S. grids. The White House has said the U.S. must more than double existing regional transmission capacity in order to reach 2035 decarbonization goals.All of this comes as electricity demand is skyrocketing amid the increasing use of data centers and AI, and the electrification of everything from passenger vehicles to home heating systems.Despite those trends, building high-power transmission lines remains stubbornly difficult.“Building high-power transmission infrastructure can take a decade or more, and there’s been quite a few examples of projects that folks have had to abandon because they realize that there’s just so much opposition, or there’s too much complexity to pull it off cost effectively,” Heidel says. “We can drop down in voltage but carry the same amount of power because we can build systems that operate at much higher current levels, and that’s how our lines are able to melt into the background and avoid the same opposition.”Heidel says VEIR has built a pipeline of interested customers including utilities, data center operators, industrial companies, and renewable energy developers. VEIR is aiming to complete its first commercial-scale pilot carrying high power in 2026.A career in energyOver more than a decade at MIT, Heidel went from learning about the fundamentals of electrical engineering to studying the electric grid and the power sector more broadly. That journey included earning a bachelor’s, master’s, and PhD from MIT’s Department of Electrical Engineering and Computer Science as well as a master’s in MIT’s Technology and Policy Program, which he earned while working toward his PhD.“I got the energy bug and started to focus exclusively on energy and climate in graduate school,” Heidel says.Following his PhD, Heidel was named research director of MIT’s Future of the Electric Grid study, which was completed in 2011.“That was a fantastic opportunity at the outset of my career to survey the entire landscape and understand challenges facing the power grid and the power sector more broadly,” Heidel says. “It gave me a good foundation for understanding the grid, how it works, who’s involved, how decisions get made, how expansion works, and it looked out over the next 30 years.”After leaving MIT, Heidel worked at the Department of Energy’s Advanced Research Projects Agency-Energy (ARPA-E) and then at Bill Gates’ Breakthrough Energy Ventures (BEV) investment firm, where he continued studying transmission.“Just about every single decarbonization scenario and study that’s been published in the last two decades concludes that to achieve aggressive greenhouse gas emissions reductions, we’re going to have to double or triple the scale of power grids around the world,” Heidel says. “But when we looked at the data on how fast grids were being expanded, the ease with which transmission lines could be built, the cost of building new transmission, just about every indicator was heading in the wrong direction. Transmission was getting more expensive over time and taking longer to build. We desperately need to find a new solution.”Unlike traditional transmission lines made from steel and aluminum, VEIR’s transmission lines leverage decades of progress in the development of high-temperature superconducting tapes and other materials. Some of that progress has been driven by the nuclear fusion industry, which incorporates superconducting materials into some of their nuclear reactor designs.But the core innovation at VEIR is the cooling system. VEIR co-founder and advisor Steve Ashworth developed the rough idea for the cooling system more than 15 years ago at Los Alamos National Laboratory as part of a larger Department of Energy-funded research project. When the project was shut down, the idea was largely forgotten.Heidel and others at Breakthrough Energy Ventures became aware of the innovation in 2019 while researching transmission. Today VEIR’s system is passively cooled with nitrogen, which runs through a vacuum-insulated pipe that surrounds a superconducting cable. Heat exchange units are also used on some transmission towers.Heidel says transmission lines designed to carry that much power are typically far bigger than VEIR’s design, and other attempts at shrinking the footprint of high-power lines were limited to short distances underground.“High power requires high voltage, and high voltage requires tall towers and wide right of ways, and those tall towers and those wide right of ways are deeply unpopular,” Heidel says. “That is a universal truth across just about the entire world.”Moving power around the worldVEIR’s first alternating current (AC) overhead product line is capable of transmission capacities up to 400 megawatts and voltages of up to 69 kilovolts, and the company plans to scale to higher voltage and higher-power products in the future, including direct current (DC) lines.VEIR will sell its equipment to the companies installing transmission lines, with a primary focus on the U.S. market.In the longer term, Heidel believes VEIR’s technology is needed as soon as possible to meet rising electricity demands and new renewable energy projects around the globe. More

    • 113 Shares139 Views

      in Energy

      Students research pathways for MIT to reach decarbonization goals

      by

      A number of emerging technologies hold promise for helping organizations move away from fossil fuels and achieve deep decarbonization. The challenge is deciding which technologies to adopt, and when.MIT, which has a goal of eliminating direct campus emissions by 2050, must make such decisions sooner than most to achieve its mission. That was the challenge at the heart of the recently concluded class 4.s42 (Building Technology — Carbon Reduction Pathways for the MIT Campus).The class brought together undergraduate and graduate students from across the Institute to learn about different technologies and decide on the best path forward. It concluded with a final report as well as student presentations to members of MIT’s Climate Nucleus on May 9.“The mission of the class is to put together a cohesive document outlining how MIT can reach its goal of decarbonization by 2050,” says Morgan Johnson Quamina, an undergraduate in the Department of Civil and Environmental Engineering. “We’re evaluating how MIT can reach these goals on time, what sorts of technologies can help, and how quickly and aggressively we’ll have to move. The final report details a ton of scenarios for partial and full implementation of different technologies, outlines timelines for everything, and features recommendations.”The class was taught by professor of architecture Christoph Reinhart but included presentations by other faculty about low- and zero-carbon technology areas in their fields, including advanced nuclear reactors, deep geothermal energy, carbon capture, and more.The students’ work served as an extension of MIT’s Campus Decarbonization Working Group, which Reinhart co-chairs with Director of Sustainability Julie Newman. The group is charged with developing a technology roadmap for the campus to reach its goal of decarbonizing its energy systems.Reinhart says the class was a way to leverage the energy and creativity of students to accelerate his group’s work.“It’s very much focused on establishing a vision for what could happen at MIT,” Reinhart says. “We are trying to bring these technologies together so that we see how this [decarbonization process] would actually look on our campus.”A class with impactThroughout the semester, every Thursday from 9 a.m. to 12 p.m., around 20 students gathered to explore different decarbonization technology pathways. They also discussed energy policies, methods for evaluating risk, and future electric grid supply changes in New England.“I love that this work can have a real-world impact,” says Emile Germonpre, a master’s student in the Department of Nuclear Science and Engineering. “You can tell people aren’t thinking about grades or workload — I think people would’ve loved it even if the workload was doubled. Everyone is just intrinsically motivated to help solve this problem.”The classes typically began with an introduction to one of 10 different technologies. The introductions covered technical maturity, ease of implementation, costs, and how to model the technology’s impact on campus emissions. Students were then split into teams to evaluate each technology’s feasibility.“I’ve learned a lot about decarbonization and climate change,” says Johnson Quamina. “As an undergrad, I haven’t had many focused classes like this. But it was really beneficial to learn about some of these technologies I hadn’t even heard of before. It’s awesome to be contributing to the community like this.”As part of the class, students also developed a model that visualizes each intervention’s effect on emissions, allowing users to select interventions or combinations of interventions to see how they shape emissions trajectories.“We have a physics-based model that takes into account every building,” says Reinhart. “You can look at variants where we retrofit buildings, where we add rooftop photovoltaics, nuclear, carbon capture, and adopting different types of district underground heating systems. The point is you can start to see how fast we could do something like this and what the real game-changers are.”The class also designed and conducted a preliminary survey, to be expanded in the fall, that captures the MIT community’s attitudes towards the different technologies. Preliminary results were shared with the Climate Nucleus during students’ May 9 presentations.“I think it’s this unique and wonderful intersection of the forward-looking and innovative nature of academia with real world impact and specificity that you’d typically only find in industry,” Germonpre says. “It lets you work on a tangible project, the MIT campus, while exploring technologies that companies today find too risky to be the first mover on.”From MIT’s campus to the worldThe students recommended MIT form a building energy team to audit and retrofit all campus buildings. They also suggested MIT order a comprehensive geological feasibility survey to support planning regarding shallow and deep borehole fields for harvesting underground heat. A third recommendation was to communicate with the MIT community as well as with regulators and policymakers in the area about the deployment of nuclear batteries and deep geothermal boreholes on campus.The students’ modeling tool can also help members of the working group explore various decarbonization pathways. For instance, installing rooftop photovoltaics now would effectively reduce emissions, but installing them in a few decades, when the regional electricity grid is expected to be reducing its reliance on fossil fuels anyways, would have a much smaller impact.“When you have students working together, the recommendations are a little less filtered, which I think is a good thing,” Reinhart says. “I think there’s a real sense of urgency in the class. For certain choices, we have to basically act now.”Reinhart plans to do more activities related to the Working Group and the class’ recommendations in the fall, and he says he’s currently engaged with the Massachusetts Governor’s Office to explore doing something similar for the state.Students say they plan to keep working on the survey this summer and continue studying their technology areas. In the longer term, they believe the experience will help them in their careers.“Decarbonization is really important, and understanding how we can implement new technologies on campuses or in buildings provides me with a more well-rounded vision for what I could design in my career,” says Johnson Quamina, who wants to work as a structural or environmental engineer but says the class has also inspired her to consider careers in energy.The students’ findings also have implications beyond MIT campus. In accordance with MIT’s 2015 climate plan that committed to using the campus community as a “test bed for change,” the students’ recommendations also hold value for organizations around the world.“The mission is definitely broader than just MIT,” Germonpre says. “We don’t just want to solve MIT’s problem. We’ve dismissed technologies that were too specific to MIT. The goal is for MIT to lead by example and help certain technologies mature so that we can accelerate their impact.” More