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      MIT Energy Conference focuses on climate’s toughest challenges

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      This year’s MIT Energy Conference, the largest student-led event of its kind, included keynote talks and panels that tackled some of the thorniest remaining challenges in the global effort to cut back on climate-altering emissions. These include the production of construction materials such as steel and cement, and the role of transportation including aviation and shipping. While the challenges are formidable, approaches incorporating methods such as fusion, heat pumps, energy efficiency, and the use of hydrogen hold promise, participants said.

      The two-day conference, held on March 31 and April 1 for more than 900 participants, included keynote lectures, 14 panel discussions, a fireside chat, networking events, and more. The event this year included the final round of the annual MIT Climate and Energy Prize, whose winning team receives $100,000 and other support. The prize, awarded since 2007, has led to the creation of more than 220 companies and $1.1 billion in investments.

      This year’s winner is a project that hopes to provide an innovative, efficient waterless washing machine aimed at the vast majority of the world’s people, who still do laundry by hand.

      “A truly consequential moment in history”

      In his opening keynote address Fatih Birol, executive director of the International Energy Agency, noted that this year’s conference was taking place during the unprovoked invasion of Ukraine by Russia, a leading gas and oil exporter. As a result, “global oil markets are going through a major turmoil,” he said.

      He said that Russian oil exports are expected to drop by 3 million barrels a day, and that international efforts to release reserves and promote increased production elsewhere will help, but will not suffice. “We have to look to other measures” to make up the shortfall, he said, noting that his agency has produced a 10-point plan of measures to help reduce global demand for oil.

      Europe gets 45 percent of its natural gas from Russia, and the agency also has developed a 10-point plan to help alleviate expected shortages there, including measures to improve energy efficiency in homes and industries, promote renewable heating sources, and postpone retirement of some nuclear plants. But he emphasized that “our goals to reach our climate targets should not be yet another victim of Mr. Putin and his allies.”  Unfortunately, Birol said, “I see that addressing climate change is sliding down in the policy agenda of many governments.”

      But he sees reasons for optimism as well, in terms of the feasibility of achieving the global emissions reduction target, agreed to by countries representing 80 percent of the global economy, of reaching net zero carbon dioxide emissions by 2050. The IEA has developed a roadmap for the entire energy sector to get there, which is now used by many governments as a benchmark, according to Birol.

      In addition, the trend is already clear, he said. “More than 90 percent of all power plants installed in the world [last year] were renewable energy,” mainly solar and wind. And 10 percent of cars sold worldwide last year, and 20 percent in Europe, were electric cars. “Please remember that in 2019 it was only 2 percent!” he said. He also predicted that “nuclear is going to make a comeback in many countries,” both in terms of large plants and newer small modular reactors.

      Birol said that “I hope that the current crisis gives governments the impetus to address the energy security concerns, to reach our climate goals, and … [to] choose the right direction at this very important turning point.”

      The conference’s second day began with keynote talks by Gina McCarthy, national climate advisor at the White House Office of Domestic Climate Policy, and Maria Zuber, MIT’s vice president for research. In her address, Zuber said, “This conference comes at a truly consequential moment in history — a moment that puts into stark relief the enormous risks created by our current fossil-fuel based energy system — risks we cannot continue to accept.”

      She added that “time is not on our side.” To meet global commitments for limiting climate impacts, the world needs to reduce emissions by about half by 2030, and get to net zero by 2050. “In other words, we need to transform our entire global energy system in a few decades,” she said. She cited MIT’s “Fast Forward” climate action plan, issued last year, as presenting the two tracks that the world needs to pursue simultaneously: going as far as possible, as fast as possible, with the tools that exist now, while also innovating and investing in new ideas, technologies, practices, and institutions that may be needed to reach the net-zero goal.

      On the first track, she said, citing an IEA report, “from here until 2040, we can get most of the emissions reductions we need with technologies that are currently available or on the verge of becoming commercially available.” These include electrifying and boosting efficiency in buildings, industry, and transportation; increasing the portion of electricity coming from emissions-free sources; and investing in new infrastructure such as electric vehicle charging stations.

      But more than that is needed, she pointed out. For example, the amount of methane that leaks away into the atmosphere from fossil fuel operations is equivalent to all the natural gas used in Europe’s power sector, Zuber said. Recovering and selling that methane can dramatically reduce global methane emissions, often at little or no cost.

      For the longer run, “we need track-two solutions to decarbonize tough industries like aviation, shipping, chemicals, concrete, and steel,” and to remove carbon dioxide from the atmosphere. She described some of the promising technologies that are in the pipeline. Fusion, for example, has moved from being a scientific challenge to an engineering problem whose solution seems well underway, she said.

      Another important area is food-related systems, which currently account for a third of all global emissions. For example, fertilizer production uses a very energy-intensive process, but work on plants engineered to fix nitrogen directly could make a significant dent.

      These and several other advanced research areas may not all pan out, but some undoubtedly will, and will help curb climate change as well as create new jobs and reduce pollution.

      Though the problems we face are complex, they are not insurmountable, Zuber said. “We don’t need a miracle. What we need is to move along the two tracks I’ve outlined with determination, ingenuity, and fierce urgency.”

      The promise and challenges of hydrogen

      Other conference speakers took on some of the less-discussed but crucial areas that also need to be addressed in order to limit global warming to 1.5 degrees. Heavy transportation, and aviation in particular, have been considered especially challenging. In his keynote address, Glenn Llewellyn, vice president for zero-emission aircraft at Airbus, outlined several approaches his company is working on to develop competitive midrange alternative airliners by 2035 that use either batteries or fuel cells powered by hydrogen. The early-stage designs demonstrate that, contrary to some projections, there is a realistic pathway to weaning that industry from its present reliance on fossil fuel, chiefly kerosene.

      Hydrogen has real potential as an aviation fuel, he said, either directly for use in fuel cells for power or burned directly for propulsion, or indirectly as a feedstock for synthetic fuels. Both are being studied by the company, he said, including a hybrid model that uses both hydrogen fuel cells and hydrogen-fueled jet engines. The company projects a range of 2,000 nautical miles for a jet carrying 200 to 300 passengers, he said — all with no direct emissions and no contrails.

      But this vision will not be practical, Llewellyn said, unless economies of scale help to significantly lower the cost of hydrogen production. “Hydrogen is at the hub of aviation decarbonization,” he said. But that kind of price reduction seems quite feasible, he said, given that other major industries are also seriously looking at the use of hydrogen for their own decarbonization plans, including the production of steel and cement.

      Such uses were the subject of a panel discussion entitled “Deploying the Hydrogen Economy.” Hydrogen production technology exists, but not nearly at the scale that’s needed, which is about 500 million tons a year, pointed out moderator Dharik Mallapragada of the MIT Energy Initiative.

      Yet in some applications, the use of hydrogen both reduces emissions and is economically competitive. Preeti Pande of Plug Power said that her company, which produces hydrogen fuel cells, has found a significant market in an unexpected place: fork lifts, used in warehouses and factories worldwide. It turns out that replacing current battery-operated versions with fuel cell versions is a win-win for the companies that use them, saving money while helping to meet decarbonization goals.

      Lindsay Ashby of Avangrid Renewables said that the company has installed fuel-cell buses in Barcelona that run entirely on hydrogen generated by solar panels. The company is also building a 100-megawatt solar facility to produce hydrogen for the production of fertilizer, another major industry in need of decarbonization because of its large emissions footprint. And Brett Perleman of the Center for Houston’s Future said of his city that “we’re already a hydrogen hub today, just not green hydrogen” since the gas is currently mostly produced as a byproduct of fossil fuels. But that is changing rapidly, he said, and Houston, along with several other cities, aims to be a center of activity for hydrogen produced from renewable, non-carbon-emitting sources. They aim to be producing 1,000 tons a day by 2028, “and I think we’ll end up exceeding that,” he said.

      For industries that can switch to renewably generated electricity, that is typically the best choice, Perleman said. “But for those that can’t, hydrogen is a great option,” and that includes aviation, shipping, and rail. “The big oil companies all have plans in place” to develop clean hydrogen production, he said. “It’s not just a dream, but a reality.”

      For shipping, which tends to rely on bunker fuel, a particularly high-emissions fossil fuel, another potential option could be a new generation of small nuclear plants, said Jeff Navin of Terrapower, a company currently developing such units. “Finding replacements for coal, oil, or natural gas for industrial purposes is very hard,” he said, but often what these processes require is consistent high heat, which nuclear can deliver, as long as costs and regulatory issues can be resolved.  

      MIT professor of nuclear engineering Jacopo Buongiorno pointed out that the primary reasons for delays and cost overruns in nuclear plants have had to do with issues at the construction site, many of which could be alleviated by having smaller, factory-built modular plants, or by building multiple units at a time of a standardized design. If the government would take on the nuclear waste disposal, as some other countries have done, then nuclear power could play an important part in the decarbonization of many industries, he said.

      Student-led startups

      The two-day conference concluded with the final round of the annual MIT Climate and Energy Prize, consisting of the five finalist teams presenting brief pitches for their startup company ideas, followed by questions from the panel of judges. This year’s finalists included a team called Muket, dedicated to finding ways of reducing methane emissions from cattle and dairy farms. Feed additives or other measures could cut the emissions by 50 percent, the team estimates.

      A team called Ivu Biologics described a system for incorporating nitrogen-fixing microbes into the coatings of seeds, thereby reducing the need for added fertilizers, whose production is a major greenhouse gas source. The company is making use of seed-coating technology developed at MIT over the last few years. Another team, called Mesophase, also based on MIT-developed technology, aims to replace the condensers used in power plants and other industrial systems with much more efficient versions, thus increasing the energy output from a given amount of fuel or other heat source.

      A team called TerraTrade aims to facilitate the adoption of power purchase agreements by companies, institutions and governments, by acting as a kind of broker to create and administer such agreements, making it easier for even smaller entities to take part in these plans, which help to enable rapid development of renewable fossil-fuel-free energy production.

      The grand prize of $100,000 was awarded to a team called Ultropia, which is developing a combined clothes washer and drier that uses ultrasound instead of water for its cleaning. The system does use a small amount of water, but this can be recycled, making these usable even in areas where water availability is limited. The devices could have a great impact on the estimated 6 billion people in the world today who are still limited to washing clothes by hand, the team says, and because the machines would be so efficient, they would require very little energy to run — a significant improvement over the wider adoption of conventional washers and driers. More

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      How to clean solar panels without water

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      Solar power is expected to reach 10 percent of global power generation by the year 2030, and much of that is likely to be located in desert areas, where sunlight is abundant. But the accumulation of dust on solar panels or mirrors is already a significant issue — it can reduce the output of photovoltaic panels by as much as 30 percent in just one month — so regular cleaning is essential for such installations.

      But cleaning solar panels currently is estimated to use about 10 billion gallons of water per year — enough to supply drinking water for up to 2 million people. Attempts at waterless cleaning are labor intensive and tend to cause irreversible scratching of the surfaces, which also reduces efficiency. Now, a team of researchers at MIT has devised a way of automatically cleaning solar panels, or the mirrors of solar thermal plants, in a waterless, no-contact system that could significantly reduce the dust problem, they say.

      The new system uses electrostatic repulsion to cause dust particles to detach and virtually leap off the panel’s surface, without the need for water or brushes. To activate the system, a simple electrode passes just above the solar panel’s surface, imparting an electrical charge to the dust particles, which are then repelled by a charge applied to the panel itself. The system can be operated automatically using a simple electric motor and guide rails along the side of the panel. The research is described today in the journal Science Advances, in a paper by MIT graduate student Sreedath Panat and professor of mechanical engineering Kripa Varanasi.

      Play video

      Despite concerted efforts worldwide to develop ever more efficient solar panels, Varanasi says, “a mundane problem like dust can actually put a serious dent in the whole thing.” Lab tests conducted by Panat and Varanasi showed that the dropoff of energy output from the panels happens steeply at the very beginning of the process of dust accumulation and can easily reach 30 percent reduction after just one month without cleaning. Even a 1 percent reduction in power, for a 150-megawatt solar installation, they calculated, could result in a $200,000 loss in annual revenue. The researchers say that globally, a 3 to 4 percent reduction in power output from solar plants would amount to a loss of between $3.3 billion and $5.5 billion.

      “There is so much work going on in solar materials,” Varanasi says. “They’re pushing the boundaries, trying to gain a few percent here and there in improving the efficiency, and here you have something that can obliterate all of that right away.”

      Many of the largest solar power installations in the world, including ones in China, India, the U.A.E., and the U.S., are located in desert regions. The water used for cleaning these solar panels using pressurized water jets has to be trucked in from a distance, and it has to be very pure to avoid leaving behind deposits on the surfaces. Dry scrubbing is sometimes used but is less effective at cleaning the surfaces and can cause permanent scratching that also reduces light transmission.

      Water cleaning makes up about 10 percent of the operating costs of solar installations. The new system could potentially reduce these costs while improving the overall power output by allowing for more frequent automated cleanings, the researchers say.

      “The water footprint of the solar industry is mind boggling,” Varanasi says, and it will be increasing as these installations continue to expand worldwide. “So, the industry has to be very careful and thoughtful about how to make this a sustainable solution.”

      Other groups have tried to develop electrostatic based solutions, but these have relied on a layer called an electrodynamic screen, using interdigitated electrodes. These screens can have defects that allow moisture in and cause them to fail, Varanasi says. While they might be useful on a place like Mars, he says, where moisture is not an issue, even in desert environments on Earth this can be a serious problem.

      The new system they developed only requires an electrode, which can be a simple metal bar, to pass over the panel, producing an electric field that imparts a charge to the dust particles as it goes. An opposite charge applied to a transparent conductive layer just a few nanometers thick deposited on the glass covering of the the solar panel then repels the particles, and by calculating the right voltage to apply, the researchers were able to find a voltage range sufficient to overcome the pull of gravity and adhesion forces, and cause the dust to lift away.

      Using specially prepared laboratory samples of dust with a range of particle sizes, experiments proved that the process works effectively on a laboratory-scale test installation, Panat says. The tests showed that humidity in the air provided a thin coating of water on the particles, which turned out to be crucial to making the effect work. “We performed experiments at varying humidities from 5 percent to 95 percent,” Panat says. “As long as the ambient humidity is greater than 30 percent, you can remove almost all of the particles from the surface, but as humidity decreases, it becomes harder.”

      Varanasi says that “the good news is that when you get to 30 percent humidity, most deserts actually fall in this regime.” And even those that are typically drier than that tend to have higher humidity in the early morning hours, leading to dew formation, so the cleaning could be timed accordingly.

      “Moreover, unlike some of the prior work on electrodynamic screens, which actually do not work at high or even moderate humidity, our system can work at humidity even as high as 95 percent, indefinitely,” Panat says.

      In practice, at scale, each solar panel could be fitted with railings on each side, with an electrode spanning across the panel. A small electric motor, perhaps using a tiny portion of the output from the panel itself, would drive a belt system to move the electrode from one end of the panel to the other, causing all the dust to fall away. The whole process could be automated or controlled remotely. Alternatively, thin strips of conductive transparent material could be permanently arranged above the panel, eliminating the need for moving parts.

      By eliminating the dependency on trucked-in water, by eliminating the buildup of dust that can contain corrosive compounds, and by lowering the overall operational costs, such systems have the potential to significantly improve the overall efficiency and reliability of solar installations, Varanasi says.

      The research was supported by Italian energy firm Eni. S.p.A. through the MIT Energy Initiative. More

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      in Energy

      New power sources

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      In the mid-1990s, a few energy activists in Massachusetts had a vision: What if citizens had choice about the energy they consumed? Instead of being force-fed electricity sources selected by a utility company, what if cities, towns, and groups of individuals could purchase power that was cleaner and cheaper?

      The small group of activists — including a journalist, the head of a small nonprofit, a local county official, and a legislative aide — drafted model legislation along these lines that reached the state Senate in 1995. The measure stalled out. In 1997, they tried again. Massachusetts legislators were busy passing a bill to reform the state power industry in other ways, and this time the activists got their low-profile policy idea included in it — as a provision so marginal it only got a brief mention in The Boston Globe’s coverage of the bill.

      Today, this idea, often known as Community Choice Aggregation (CCA), is used by roughly 36 million people in the U.S., or 11 percent of the population. Local residents, as a bloc, purchase energy with certain specifications attached, and over 1,800 communities have adopted CCA in six states, with others testing CCA pilot programs. From such modest beginnings, CCA has become a big deal.

      “It started small, then had a profound impact,” says David Hsu, an associate professor at MIT who studies energy policy issues. Indeed, the trajectory of CCA is so striking that Hsu has researched its origins, combing through a variety of archival sources and interviewing the principals. He has now written a journal article examining the lessons and implications of this episode.

      Hsu’s paper, “Straight out of Cape Cod: The origin of community choice aggregation and its spread to other states,” appears in advance online form in the journal Energy Research and Social Science, and in the April print edition of the publication.

      “I wanted to show people that a small idea could take off into something big,” Hsu says. “For me that’s a really hopeful democratic story, where people could do something without feeling they had to take on a whole giant system that wouldn’t immediately respond to only one person.”

      Local control

      Aggregating consumers to purchase energy was not a novelty in the 1990s. Companies within many industries have long joined forces to gain purchasing power for energy. And Rhode Island tried a form of CCA slightly earlier than Massachusetts did.

      However, it is the Massachusetts model that has been adopted widely: Cities or towns can require power purchases from, say, renewable sources, while individual citizens can opt out of those agreements. More state funding (for things like efficiency improvements) is redirected to cities and towns as well.

      In both ways, CCA policies provide more local control over energy delivery. They have been adopted in California, Illinois, New Jersey, New York, and Ohio. Meanwhile, Maryland, New Hampshire, and Virginia have recently passed similar legislation (also known as municipal or government aggregation, or community choice energy).

      For cities and towns, Hsu says, “Maybe you don’t own outright the whole energy system, but let’s take away one particular function of the utility, which is procurement.”

      That vision motivated a handful of Massachusetts activists and policy experts in the 1990s, including journalist Scott Ridley, who co-wrote a 1986 book, “Power Struggle,” with the University of Massachusetts historian Richard Rudolph and had spent years thinking about ways to reconfigure the energy system; Matt Patrick, chair of a local nonprofit focused on energy efficiency; Rob O’Leary, a local official in Barnstable County, on Cape Cod; and Paul Fenn, a staff aide to the state senator who chaired the legislature’s energy committee.

      “It started with these political activists,” Hsu says.

      Hsu’s research emphasizes several lessons to be learned from the fact the legislation first failed in 1995, before unexpectedly passing in 1997. Ridley remained an author and public figure; Patrick and O’Leary would each eventually be elected to the state legislature, but only after 2000; and Fenn had left his staff position by 1995 and worked with the group long-distance from California (where he became a long-term advocate about the issue). Thus, at the time CCA passed in 1997, none of its main advocates held an insider position in state politics. How did it succeed?

      Lessons of the legislation

      In the first place, Hsu believes, a legislative process resembles what the political theorist John Kingdon has called a “multiple streams framework,” in which “many elements of the policymaking process are separate, meandering, and uncertain.” Legislation isn’t entirely controlled by big donors or other interest groups, and “policy entrepreneurs” can find success in unpredictable windows of opportunity.

      “It’s the most true-to-life theory,” says Hsu.  

      Second, Hsu emphasizes, finding allies is crucial. In the case of CCA, that came about in a few ways. Many towns in Massachusetts have a town-level legislature known as Town Meeting; the activists got those bodies in about 20 towns to pass nonbinding resolutions in favor of community choice. O’Leary helped create a regional county commission in Barnstable County, while Patrick crafted an energy plan for it. High electricity rates were affecting all of Cape Cod at the time, so community choice also served as an economic benefit for Cape Cod’s working-class service-industry employees. The activists also found that adding an opt-out clause to the 1997 version appealed to legislators, who would support CCA if their constituents were not all bound to it.

      “You really have to stick with it, and you have to look for coalition partners,” Hsu says. “It’s fun to hear them [the activists] talk about going to Town Meetings, and how they tried to build grassroots support. If you look for allies, you can get things done. [I hope] the people can see [themselves] in other people’s activism even if they’re not exactly the same as you are.”

      By 1997, the CCA legislation had more geographic support, was understood as both an economic and environmental benefit for voters, and would not force membership upon anyone. The activists, while giving media interviews, and holding conferences, had found additional traction in the principle of citizen choice.

      “It’s interesting to me how the rhetoric of [citizen] choice and the rhetoric of democracy proves to be effective,” Hsu says. “Legislators feel like they have to give everyone some choice. And it expresses a collective desire for a choice that the utilities take away by being monopolies.”

      He adds: “We need to set out principles that shape systems, rather than just taking the system as a given and trying to justify principles that are 150 years old.”

      One last element in CCA passage was good timing. The governor and legislature in Massachusetts were already seeking a “grand bargain” to restructure electricity delivery and loosen the grip of utilities; the CCA fit in as part of this larger reform movement. Still, CCA adoption has been gradual; about one-third of Massachusetts towns with CCA have only adopted it within the last five years.

      CCA’s growth does not mean it’s invulnerable to repeal or utility-funded opposition efforts — “In California there’s been pretty intense pushback,” Hsu notes. Still, Hsu concludes, the fact that a handful of activists could start a national energy-policy movement is a useful reminder that everyone’s actions can make a difference.

      “It wasn’t like they went charging through a barricade, they just found a way around it,” Hsu says. “I want my students to know you can organize and rethink the future. It takes some commitment and work over a long time.” More

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      in Security

      Solar-powered system offers a route to inexpensive desalination

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      An estimated two-thirds of humanity is affected by shortages of water, and many such areas in the developing world also face a lack of dependable electricity. Widespread research efforts have thus focused on ways to desalinate seawater or brackish water using just solar heat. Many such efforts have run into problems with fouling of equipment caused by salt buildup, however, which often adds complexity and expense.

      Now, a team of researchers at MIT and in China has come up with a solution to the problem of salt accumulation — and in the process developed a desalination system that is both more efficient and less expensive than previous solar desalination methods. The process could also be used to treat contaminated wastewater or to generate steam for sterilizing medical instruments, all without requiring any power source other than sunlight itself.

      The findings are described today in the journal Nature Communications, in a paper by MIT graduate student Lenan Zhang, postdoc Xiangyu Li, professor of mechanical engineering Evelyn Wang, and four others.

      “There have been a lot of demonstrations of really high-performing, salt-rejecting, solar-based evaporation designs of various devices,” Wang says. “The challenge has been the salt fouling issue, that people haven’t really addressed. So, we see these very attractive performance numbers, but they’re often limited because of longevity. Over time, things will foul.”

      Many attempts at solar desalination systems rely on some kind of wick to draw the saline water through the device, but these wicks are vulnerable to salt accumulation and relatively difficult to clean. The team focused on developing a wick-free system instead. The result is a layered system, with dark material at the top to absorb the sun’s heat, then a thin layer of water above a perforated layer of material, sitting atop a deep reservoir of the salty water such as a tank or a pond. After careful calculations and experiments, the researchers determined the optimal size for the holes drilled through the perforated material, which in their tests was made of polyurethane. At 2.5 millimeters across, these holes can be easily made using commonly available waterjets.

      The holes are large enough to allow for a natural convective circulation between the warmer upper layer of water and the colder reservoir below. That circulation naturally draws the salt from the thin layer above down into the much larger body of water below, where it becomes well-diluted and no longer a problem. “It allows us to achieve high performance and yet also prevent this salt accumulation,” says Wang, who is the Ford Professor of Engineering and head of the Department of Mechanical Engineering.

      Li says that the advantages of this system are “both the high performance and the reliable operation, especially under extreme conditions, where we can actually work with near-saturation saline water. And that means it’s also very useful for wastewater treatment.”

      He adds that much work on such solar-powered desalination has focused on novel materials. “But in our case, we use really low-cost, almost household materials.” The key was analyzing and understanding the convective flow that drives this entirely passive system, he says. “People say you always need new materials, expensive ones, or complicated structures or wicking structures to do that. And this is, I believe, the first one that does this without wicking structures.”

      This new approach “provides a promising and efficient path for desalination of high salinity solutions, and could be a game changer in solar water desalination,” says Hadi Ghasemi, a professor of chemical and biomolecular engineering at the University of Houston, who was not associated with this work. “Further work is required for assessment of this concept in large settings and in long runs,” he adds.

      Just as hot air rises and cold air falls, Zhang explains, natural convection drives the desalination process in this device. In the confined water layer near the top, “the evaporation happens at the very top interface. Because of the salt, the density of water at the very top interface is higher, and the bottom water has lower density. So, this is an original driving force for this natural convection because the higher density at the top drives the salty liquid to go down.” The water evaporated from the top of the system can then be collected on a condensing surface, providing pure fresh water.

      The rejection of salt to the water below could also cause heat to be lost in the process, so preventing that required careful engineering, including making the perforated layer out of highly insulating material to keep the heat concentrated above. The solar heating at the top is accomplished through a simple layer of black paint.

      This gif shows fluid flow visualized by food dye. The left-side shows the slow transport of colored de-ionized water from the top to the bottom bulk water. The right-side shows the fast transport of colored saline water from the top to the bottom bulk water driven by the natural convection effect.

      So far, the team has proven the concept using small benchtop devices, so the next step will be starting to scale up to devices that could have practical applications. Based on their calculations, a system with just 1 square meter (about a square yard) of collecting area should be sufficient to provide a family’s daily needs for drinking water, they say. Zhang says they calculated that the necessary materials for a 1-square-meter device would cost only about $4.

      Their test apparatus operated for a week with no signs of any salt accumulation, Li says. And the device is remarkably stable. “Even if we apply some extreme perturbation, like waves on the seawater or the lake,” where such a device could be installed as a floating platform, “it can return to its original equilibrium position very fast,” he says.

      The necessary work to translate this lab-scale proof of concept into workable commercial devices, and to improve the overall water production rate, should be possible within a few years, Zhang says. The first applications are likely to be providing safe water in remote off-grid locations, or for disaster relief after hurricanes, earthquakes, or other disruptions of normal water supplies.

      Zhang adds that “if we can concentrate the sunlight a little bit, we could use this passive device to generate high-temperature steam to do medical sterilization” for off-grid rural areas.

      “I think a real opportunity is the developing world,” Wang says. “I think that is where there’s most probable impact near-term, because of the simplicity of the design.” But, she adds, “if we really want to get it out there, we also need to work with the end users, to really be able to adopt the way we design it so that they’re willing to use it.”

      “This is a new strategy toward solving the salt accumulation problem in solar evaporation,” says Peng Wang, a professor at King Abdullah University of Science and Technology in Saudi Arabia, who was not associated with this research. “This elegant design will inspire new innovations in the design of advanced solar evaporators. The strategy is very promising due to its high energy efficiency, operation durability, and low cost, which contributes to low-cost and passive water desalination to produce fresh water from various source water with high salinity, e.g., seawater, brine, or brackish groundwater.”

      The team also included Yang Zhong, Arny Leroy, and Lin Zhao at MIT, and Zhenyuan Xu at Shanghai Jiao Tong University in China. The work was supported by the Singapore-MIT Alliance for Research and Technology, the U.S.-Egypt Science and Technology Joint Fund, and used facilities supported by the National Science Foundation. More

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      in Environment

      Reducing methane emissions at landfills

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      The second-largest driver of global warming is methane, a greenhouse gas 28 times more potent than carbon dioxide. Landfills are a major source of methane, which is created when organic material decomposes underground.

      Now a startup that began at MIT is aiming to significantly reduce methane emissions from landfills with a system that requires no extra land, roads, or electric lines to work. The company, Loci Controls, has developed a solar-powered system that optimizes the collection of methane from landfills so more of it can be converted into natural gas.

      At the center of Loci’s (pronounced “low-sigh”) system is a lunchbox-sized device that attaches to methane collection wells, which vacuum the methane up to the surface for processing. The optimal vacuum force changes with factors like atmospheric pressure and temperature. Loci’s system monitors those factors and adjusts the vacuum force at each well far more frequently than is possible with field technicians making manual adjustments.

      “We expect to reduce methane emissions more than any other company in the world over the next five years,” Loci Controls CEO Peter Quigley ’85 says. The company was founded by Melinda Hale Sims SM ’09, PhD ’12 and Andrew Campanella ’05, SM ’13.

      The reason for Quigley’s optimism is the high concentration of landfill methane emissions. Most landfill emissions in the U.S. come from about 1,000 large dumps. Increasing collection of methane at those sites could make a significant dent in the country’s overall emissions.

      In one landfill where Loci’s system was installed, for instance, the company says it increased methane sales at an annual rate of 180,000 metric tons of carbon dioxide equivalent. That’s about the same as removing 40,000 cars from the road for a year.

      Loci’s system is currently installed on wells in 15 different landfills. Quigley says only about 70 of the 1,000 big landfills in the U.S. sell gas profitably. Most of the others burn the gas. But Loci’s team believes increasing public and regulatory pressure will help expands its potential customer base.

      Uncovering a major problem

      The idea for Loci came from a revelation by Sims’ father, serial entrepreneur Michael Hale SM ’85, PhD ’89. The elder Hale was working in wastewater management when he was contacted by a landfill in New York that wanted help using its excess methane gas.

      “He realized if he could help that particular landfill with the problem, it would apply to almost any landfill,” Sims says.

      At the time, Sims was pursuing her PhD in mechanical engineering at MIT and minoring in entrepreneurship.

      Her father didn’t have time to work on the project, but Sims began exploring technology solutions to improve methane capture at landfills in her business classes. The work was unrelated to her PhD, but her advisor, David Hardt, the Ralph E. and Eloise F. Cross Professor in Manufacturing at MIT, was understanding. (Hardt had also served as PhD advisor for Sim’s father, who was, after all, the person to blame for Sim’s new side project.)

      Sims partnered with Andrew Campanella, then a master’s student focused on electrical engineering, and the two went through the delta v summer accelerator program hosted by the Martin Trust Center for MIT Entrepreneurship.

      Quigley was retired but serving on multiple visiting committees at MIT when he began mentoring Loci’s founders. He’d spent his career commercializing reinforced plastic through two companies, one in the high-performance sporting goods industry and the other in oil field services.

      “What captured my imagination was the emissions-reduction opportunity,” Quigley says.

      Methane is generated in landfills when organic waste decomposes. Some landfill operators capture the methane by drilling hundreds of collection wells. The vacuum pressure of those wells needs to be adjusted to maximize the amount of methane collected, but Quigley says technicians can only make those adjustments manually about once a month.

      Loci’s devices monitor gas composition, temperature, and environmental factors like barometric pressure to optimize vacuum power every hour. The data the controllers collect is aggregated in an analytics platform for technicians to monitor remotely. That data can also be used to pinpoint well failure events, such as flooding during rain, and otherwise improve operations to increase the amount of methane captured.

      “We can adjust the valves automatically, but we also have data that allows on-site operators to identify and remedy problems much more quickly,” Quigley explains.

      Furthering a high-impact mission

      Methane capture at landfills is becoming more urgent as improvements in detection technologies are revealing discrepancies between methane emission estimates and reality in the industry. A new airborne methane sensor deployed by NASA, for instance, found that California landfills have been leaking methane at rates as much as six times greater than estimates from the U.S. Environmental Protection Agency. The difference has major implications for the Earth’s atmosphere.

      A reckoning will have to occur to motivate more waste management companies to start collecting methane and to optimize methane capture. That could come in the form of new collection standards or an increased emphasis on methane collection from investors. (Funds controlled by billionaires Bill Gates and Larry Fink are major investors in waste management companies.)

      For now, Loci’s team, including co-founder and current senior advisor Sims, believes it’s on the road to making a meaningful impact under current market conditions.

      “When I was in grad school, the majority of the focus on emissions was on CO2,” Sims says. “I think methane is a really high-impact place to be focused, and I think it’s been underestimated how valuable it could be to apply technology to the industry.” More

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      in Energy

      Preparing global online learners for the clean energy transition

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      After a career devoted to making the electric power system more efficient and resilient, Marija Ilic came to MIT in 2018 eager not just to extend her research in new directions, but to prepare a new generation for the challenges of the clean-energy transition.

      To that end, Ilic, a senior research scientist in MIT’s Laboratory for Information and Decisions Systems (LIDS) and a senior staff member at Lincoln Laboratory in the Energy Systems Group, designed an edX course that captures her methods and vision: Principles of Modeling, Simulation, and Control for Electric Energy Systems.

      EdX is a provider of massive open online courses produced in partnership with MIT, Harvard University, and other leading universities. Ilic’s class made its online debut in June 2021, running for 12 weeks, and it is one of an expanding set of online courses funded by the MIT Energy Initiative (MITEI) to provide global learners with a view of the shifting energy landscape.

      Ilic first taught a version of the class while a professor at Carnegie Mellon University, rolled out a second iteration at MIT just as the pandemic struck, and then revamped the class for its current online presentation. But no matter the course location, Ilic focuses on a central theme: “With the need for decarbonization, which will mean accommodating new energy sources such as solar and wind, we must rethink how we operate power systems,” she says. “This class is about how to pose and solve the kinds of problems we will face during this transformation.”

      Hot global topic

      The edX class has been designed to welcome a broad mix of students. In summer 2021, more than 2,000 signed up from 109 countries, ranging from high school students to retirees. In surveys, some said they were drawn to the class by the opportunity to advance their knowledge of modeling. Many others hoped to learn about the move to decarbonize energy systems.

      “The energy transition is a hot topic everywhere in the world, not just in the U.S.,” says teaching assistant Miroslav Kosanic. “In the class, there were veterans of the oil industry and others working in investment and finance jobs related to energy who wanted to understand the potential impacts of changes in energy systems, as well as students from different fields and professors seeking to update their curricula — all gathered into a community.”

      Kosanic, who is currently a PhD student at MIT in electrical engineering and computer science, had taken this class remotely in the spring semester of 2021, while he was still in college in Serbia. “I knew I was interested in power systems, but this course was eye-opening for me, showing how to apply control theory and to model different components of these systems,” he says. “I finished the course and thought, this is just the beginning, and I’d like to learn a lot more.” Kosanic performed so well online that Ilic recruited him to MIT, as a LIDS researcher and edX course teaching assistant, where he grades homework assignments and moderates a lively learner community forum.

      A platform for problem-solving

      The course starts with fundamental concepts in electric power systems operations and management, and it steadily adds layers of complexity, posing real-world problems along the way. Ilic explains how voltage travels from point to point across transmission lines and how grid managers modulate systems to ensure that enough, but not too much, electricity flows. “To deliver power from one location to the next one, operators must constantly make adjustments to ensure that the receiving end can handle the voltage transmitted, optimizing voltage to avoid overheating the wires,” she says.

      In her early lectures, Ilic notes the fundamental constraints of current grid operations, organized around a hierarchy of regional managers dealing with a handful of very large oil, gas, coal, and nuclear power plants, and occupied primarily with the steady delivery of megawatt-hours to far-flung customers. But historically, this top-down structure doesn’t do a good job of preventing loss of energy due to sub-optimal transmission conditions or due to outages related to extreme weather events.

      These issues promise to grow for grid operators as distributed resources such as solar and wind enter the picture, Ilic tells students. In the United States, under new rules dictated by the Federal Energy Regulatory Commission, utilities must begin to integrate the distributed, intermittent electricity produced by wind farms, solar complexes, and even by homes and cars, which flows at voltages much lower than electricity produced by large power plants.

      Finding ways to optimize existing energy systems and to accommodate low- and zero-carbon energy sources requires powerful new modes of analysis and problem-solving. This is where Ilic’s toolbox comes in: a mathematical modeling strategy and companion software that simplifies the input and output of electrical systems, no matter how large or how small. “In the last part of the course, we take up modeling different solutions to electric service in a way that is technology-agnostic, where it only matters how much a black-box energy source produces, and the rates of production and consumption,” says Ilic.

      This black-box modeling approach, which Ilic pioneered in her research, enables students to see, for instance, “what is happening with their own household consumption, and how it affects the larger system,” says Rupamathi Jaddivada PhD ’20, a co-instructor of the edX class and a postdoc in electrical engineering and computer science. “Without getting lost in details of current or voltage, or how different components work, we think about electric energy systems as dynamical components interacting with each other, at different spatial scales.” This means that with just a basic knowledge of physical laws, high school and undergraduate students can take advantage of the course “and get excited about cleaner and more reliable energy,” adds Ilic.

      What Jaddivada and Ilic describe as “zoom in, zoom out” systems thinking leverages the ubiquity of digital communications and the so-called “internet of things.” Energy devices of all scales can link directly to other devices in a network instead of just to a central operations hub, allowing for real-time adjustments in voltage, for instance, vastly improving the potential for optimizing energy flows.

      “In the course, we discuss how information exchange will be key to integrating new end-to-end energy resources and, because of this interactivity, how we can model better ways of controlling entire energy networks,” says Ilic. “It’s a big lesson of the course to show the value of information and software in enabling us to decarbonize the system and build resilience, rather than just building hardware.”

      By the end of the course, students are invited to pursue independent research projects. Some might model the impact of a new energy source on a local grid or investigate different options for reducing energy loss in transmission lines.

      “It would be nice if they see that we don’t have to rely on hardware or large-scale solutions to bring about improved electric service and a clean and resilient grid, but instead on information technologies such as smart components exchanging data in real time, or microgrids in neighborhoods that sustain themselves even when they lose power,” says Ilic. “I hope students walk away convinced that it does make sense to rethink how we operate our basic power systems and that with systematic, physics-based modeling and IT methods we can enable better, more flexible operation in the future.”

      This article appears in the Autumn 2021 issue of Energy Futures, the magazine of the MIT Energy Initiative More

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      in Energy

      MIT Energy Initiative launches the Future Energy Systems Center

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      The MIT Energy Initiative (MITEI) has launched a new research consortium — the Future Energy Systems Center — to address the climate crisis and the role energy systems can play in solving it. This integrated effort engages researchers from across all of MIT to help the global community reach its goal of net-zero carbon emissions. The center examines the accelerating energy transition and collaborates with industrial leaders to reform the world’s energy systems. The center is part of “Fast Forward: MIT’s Climate Action Plan for the Decade,” MIT’s multi-pronged effort announced last year to address the climate crisis.

      The Future Energy Systems Center investigates the emerging technology, policy, demographics, and economics reshaping the landscape of energy supply and demand. The center conducts integrative analysis of the entire energy system — a holistic approach essential to understanding the cross-sectorial impact of the energy transition.

      “We must act quickly to get to net-zero greenhouse gas emissions. At the same time, we have a billion people around the world with inadequate access, or no access, to electricity — and we need to deliver it to them,” says MITEI Director Robert C. Armstrong, the Chevron Professor of Chemical Engineering. “The Future Energy Systems Center combines MIT’s deep knowledge of energy science and technology with advanced tools for systems analysis to examine how advances in technology and system economics may respond to various policy scenarios.”  

      The overarching focus of the center is integrative analysis of the entire energy system, providing insights into the complex multi-sectorial transformations needed to alter the three major energy-consuming sectors of the economy — transportation, industry, and buildings — in conjunction with three major decarbonization-enabling technologies — electricity, energy storage and low-carbon fuels, and carbon management. “Deep decarbonization of our energy system requires an economy-wide perspective on the technology options, energy flows, materials flows, life-cycle emissions, costs, policies, and socioeconomics consequences,” says Randall Field, the center’s executive director. “A systems approach is essential in enabling cross-disciplinary teams to work collaboratively together to address the existential crisis of climate change.”

      Through techno-economic and systems-oriented research, the center analyzes these important interactions. For example:

      •  Increased reliance on variable renewable energy, such as wind and solar, and greater electrification of transportation, industry, and buildings will require expansion of demand management and other solutions for balancing of electricity supply and demand across these areas.

      •  Likewise, balancing supply and demand will require deploying grid-scale energy storage and converting the electricity to low-carbon fuels (hydrogen and liquid fuels), which can in turn play a vital role in the energy transition for hard-to-decarbonize segments of transportation, industry, and buildings.

      •  Carbon management (carbon dioxide capture from industry point sources and from air and oceans; utilization/conversion to valuable products; transport; storage) will also play a critical role in decarbonizing industry, electricity, and fuels — both as carbon-mitigation and negative-carbon solutions.

      As a member-supported research consortium, the center collaborates with industrial experts and leaders — from both energy’s consumer and supplier sides — to gain insights to help researchers anticipate challenges and opportunities of deploying technology at the scale needed to achieve decarbonization. “The Future Energy Systems Center gives us a powerful way to engage with industry to accelerate the energy transition,” says Armstrong. “Working together, we can better understand how our current technology toolbox can be more effectively put to use now to reduce emissions, and what new technologies and policies will ultimately be needed to reach net-zero.”

      A steering committee, made up of 11 MIT professors and led by Armstrong, selects projects to create a research program with high impact on decarbonization, while leveraging MIT strengths and addressing interests of center members in pragmatic and scalable solutions. “MIT — through our recently released climate action plan — is committed to moving with urgency and speed to help wring carbon dioxide emissions out the global economy to resolve the growing climate crisis,” says Armstrong. “We have no time to waste.”

      The center members to date are: AECI, Analog Devices, Chevron, ConocoPhillips, Copec, Dominion, Duke Energy, Enerjisa, Eneva, Eni, Equinor, Eversource, Exelon, ExxonMobil, Ferrovial, Iberdrola, IHI, National Grid, Raizen, Repsol, Rio Tinto, Shell, Tata Power, Toyota Research Institute, and Washington Gas. More

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      in Environment

      A tool to speed development of new solar cells

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      In the ongoing race to develop ever-better materials and configurations for solar cells, there are many variables that can be adjusted to try to improve performance, including material type, thickness, and geometric arrangement. Developing new solar cells has generally been a tedious process of making small changes to one of these parameters at a time. While computational simulators have made it possible to evaluate such changes without having to actually build each new variation for testing, the process remains slow.

      Now, researchers at MIT and Google Brain have developed a system that makes it possible not just to evaluate one proposed design at a time, but to provide information about which changes will provide the desired improvements. This could greatly increase the rate for the discovery of new, improved configurations.

      The new system, called a differentiable solar cell simulator, is described in a paper published today in the journal Computer Physics Communications, written by MIT junior Sean Mann, research scientist Giuseppe Romano of MIT’s Institute for Soldier Nanotechnologies, and four others at MIT and at Google Brain.

      Traditional solar cell simulators, Romano explains, take the details of a solar cell configuration and produce as their output a predicted efficiency — that is, what percentage of the energy of incoming sunlight actually gets converted to an electric current. But this new simulator both predicts the efficiency and shows how much that output is affected by any one of the input parameters. “It tells you directly what happens to the efficiency if we make this layer a little bit thicker, or what happens to the efficiency if we for example change the property of the material,” he says.

      In short, he says, “we didn’t discover a new device, but we developed a tool that will enable others to discover more quickly other higher performance devices.” Using this system, “we are decreasing the number of times that we need to run a simulator to give quicker access to a wider space of optimized structures.” In addition, he says, “our tool can identify a unique set of material parameters that has been hidden so far because it’s very complex to run those simulations.”

      While traditional approaches use essentially a random search of possible variations, Mann says, with his tool “we can follow a trajectory of change because the simulator tells you what direction you want to be changing your device. That makes the process much faster because instead of exploring the entire space of opportunities, you can just follow a single path” that leads directly to improved performance.

      Since advanced solar cells often are composed of multiple layers interlaced with conductive materials to carry electric charge from one to the other, this computational tool reveals how changing the relative thicknesses of these different layers will affect the device’s output. “This is very important because the thickness is critical. There is a strong interplay between light propagation and the thickness of each layer and the absorption of each layer,” Mann explains.

      Other variables that can be evaluated include the amount of doping (the introduction of atoms of another element) that each layer receives, or the dielectric constant of insulating layers, or the bandgap, a measure of the energy levels of photons of light that can be captured by different materials used in the layers.

      This simulator is now available as an open-source tool that can be used immediately to help guide research in this field, Romano says. “It is ready, and can be taken up by industry experts.” To make use of it, researchers would couple this device’s computations with an optimization algorithm, or even a machine learning system, to rapidly assess a wide variety of possible changes and home in quickly on the most promising alternatives.

      At this point, the simulator is based on just a one-dimensional version of the solar cell, so the next step will be to expand its capabilities to include two- and three-dimensional configurations. But even this 1D version “can cover the majority of cells that are currently under production,” Romano says. Certain variations, such as so-called tandem cells using different materials, cannot yet be simulated directly by this tool, but “there are ways to approximate a tandem solar cell by simulating each of the individual cells,” Mann says.

      The simulator is “end-to-end,” Romano says, meaning it computes the sensitivity of the efficiency, also taking into account light absorption. He adds: “An appealing future direction is composing our simulator with advanced existing differentiable light-propagation simulators, to achieve enhanced accuracy.”

      Moving forward, Romano says, because this is an open-source code, “that means that once it’s up there, the community can contribute to it. And that’s why we are really excited.” Although this research group is “just a handful of people,” he says, now anyone working in the field can make their own enhancements and improvements to the code and introduce new capabilities.

      “Differentiable physics is going to provide new capabilities for the simulations of engineered systems,” says Venkat Viswanathan, an associate professor of mechanical engineering at Carnegie Mellon University, who was not associated with this work. “The  differentiable solar cell simulator is an incredible example of differentiable physics, that can now provide new capabilities to optimize solar cell device performance,” he says, calling the study “an exciting step forward.”

      In addition to Mann and Romano, the team included Eric Fadel and Steven Johnson at MIT, and Samuel Schoenholz and Ekin Cubuk at Google Brain. The work was supported in part by Eni S.p.A. and the MIT Energy Initiative, and the MIT Quest for Intelligence. More