Transistors, the building blocks of modern electronics, are typically made of silicon. Because it’s a semiconductor, this material can control the flow of electricity in a circuit. But silicon has fundamental physical limits that restrict how compact and energy-efficient a transistor can be.

MIT researchers have now replaced silicon with a magnetic semiconductor, creating a magnetic transistor that could enable smaller, faster, and more energy-efficient circuits. The material’s magnetism strongly influences its electronic behavior, leading to more efficient control of the flow of electricity. 

The team used a novel magnetic material and an optimization process that reduces the material’s defects, which boosts the transistor’s performance.

The material’s unique magnetic properties also allow for transistors with built-in memory, which would simplify circuit design and unlock new applications for high-performance electronics.

“People have known about magnets for thousands of years, but there are very limited ways to incorporate magnetism into electronics. We have shown a new way to efficiently utilize magnetism that opens up a lot of possibilities for future applications and research,” says Chung-Tao Chou, an MIT graduate student in the departments of Electrical Engineering and Computer Science (EECS) and Physics, and co-lead author of a paper on this advance.

Chou is joined on the paper by co-lead author Eugene Park, a graduate student in the Department of Materials Science and Engineering (DMSE); Julian Klein, a DMSE research scientist; Josep Ingla-Aynes, a postdoc in the MIT Plasma Science and Fusion Center; Jagadeesh S. Moodera, a senior research scientist in the Department of Physics; and senior authors Frances Ross, TDK Professor in DMSE; and Luqiao Liu, an associate professor in EECS, and a member of the Research Laboratory of Electronics; as well as others at the University of Chemistry and Technology in Prague. The paper appears today in Physical Review Letters.

Overcoming the limits

In an electronic device, silicon semiconductor transistors act like tiny light switches that turn a circuit on and off, or amplify weak signals in a communication system. They do this using a small input voltage.

But a fundamental physical limit of silicon semiconductors prevents a transistor from operating below a certain voltage, which hinders its energy efficiency.

To make more efficient electronics, researchers have spent decades working toward magnetic transistors that utilize electron spin to control the flow of electricity. Electron spin is a fundamental property that enables electrons to behave like tiny magnets.

So far, scientists have mostly been limited to using certain magnetic materials. These lack the favorable electronic properties of semiconductors, constraining device performance.

“In this work, we combine magnetism and semiconductor physics to realize useful spintronic devices,” Liu says.

The researchers replace the silicon in the surface layer of a transistor with chromium sulfur bromide, a two-dimensional material that acts as a magnetic semiconductor.

Due to the material’s structure, researchers can switch between two magnetic states very cleanly. This makes it ideal for use in a transistor that smoothly switches between “on” and “off.”

“One of the biggest challenges we faced was finding the right material. We tried many other materials that didn’t work,” Chou says.

They discovered that changing these magnetic states modifies the material’s electronic properties, enabling low-energy operation. And unlike many other 2D materials, chromium sulfur bromide remains stable in air.

To make a transistor, the researchers pattern electrodes onto a silicon substrate, then carefully align and transfer the 2D material on top. They use tape to pick up a tiny piece of material, only a few tens of nanometers thick, and place it onto the substrate.

“A lot of researchers will use solvents or glue to do the transfer, but transistors require a very clean surface. We eliminate all those risks by simplifying this step,” Chou says.

Leveraging magnetism

This lack of contamination enables their device to outperform existing magnetic transistors. Most others can only create a weak magnetic effect, changing the flow of current by a few percent or less. Their new transistor can switch or amplify the electric current by a factor of 10.

They use an external magnetic field to change the magnetic state of the material, switching the transistor using significantly less energy than would usually be required.

The material also allows them to control the magnetic states with electric current. This is important because engineers cannot apply magnetic fields to individual transistors in an electronic device. They need to control each one electrically.

The material’s magnetic properties could also enable transistors with built-in memory, simplifying the design of logic or memory circuits.

A typical memory device has a magnetic cell to store information and a transistor to read it out. Their method can combine both into one magnetic transistor.

“Now, not only are transistors turning on and off, they are also remembering information. And because we can switch the transistor with greater magnitude, the signal is much stronger so we can read out the information faster, and in a much more reliable way,” Liu says.

Building on this demonstration, the researchers plan to further study the use of electrical current to control the device. They are also working to make their method scalable so they can fabricate arrays of transistors.

This research was supported, in part, by the Semiconductor Research Corporation, the U.S. Defense Advanced Research Projects Agency (DARPA), the U.S. National Science Foundation (NSF), the U.S. Department of Energy, the U.S. Army Research Office, and the Czech Ministry of Education, Youth, and Sports. The work was partially carried out at the MIT.nano facilities.

Millions of people around the world use EFF's Privacy Badger. This browser extension blocks the hidden trackers that twist your web browsing into a commodity for Big Tech, advertisers, scammers, and data brokers. But did you know that we’re trying to solve an issue that’s even bigger than creepy ads and user profiling? You can help.

JOIN EFF

Online tracking isn't just creepy and unethical. It also enables government surveillance. Widespread commercial surveillance and weak privacy laws allow data brokers to harvest your data and sell it to law enforcement agencies including the FBI, CBP, and ICE. The government exploits this system to buy sensitive information about you that they would ordinarily need a warrant to collect, like your location over time. 

With your help, EFF is fighting back. Our team is working to enact stronger laws to uphold your privacy. We’re advocating for consumer rights in the courts. We’re investigating how these technologies affect our communities. And we’re cutting off surveillance advertising at the source with tools like Privacy Badger for everyone. You can support this work as an EFF member.

End Mass Surveillance

Privacy is a human right because it gives you a fundamental measure of security and freedom. That is why we at EFF focus on your ability to have private conversations and interact with the world using technologies that you choose. But when tools that many of us must rely on serve corporate surveillance, they also feed government surveillance. We owe it to ourselves to fight the mass spying used to control and intimidate people. Let’s do this.

For a limited time, you can join EFF as a monthly or one-time donor and pick up a new Privacy Badger Crewneck sweatshirt. The embroidered Privacy Badger mascot appears above Traditional Chinese for "privacy” because human rights are universal.

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Claw Back! This year’s member t-shirt is hot off the press featuring an orange cat swatting at the street-level surveillance equipment multiplying in our communities. You might empathize with him, but there’s a better way. Let’s end the law enforcement contracts, harmful practices, and twisted logic that enable mass spying in the first place.

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As statehouses ramp up for 2026, we’re seeing a familiar and concerning trend of lawmakers rushing to regulate the internet based on shockingly shaky science. From the California State Assembly to the Massachusetts and Minnesota legislatures, a wave of bills is crashing against the digital lives of young people, with proponents of these measures framing social media access as a "public health epidemic," or a "mental health crisis," even though we have yet to see any of the settled science that those labels usually invoke.

As a digital rights organization dedicated to the civil liberties of all users, EFF’s expertise lies in reminding lawmakers that young people enjoy largely the same free speech and privacy rights as adults. EFF is not a social science research shop, but we can read the emerging research. What that research shows is much more nuanced than what is claimed by those proposing to ban young people from social media, and it is clear that research and theories used to justify these sweeping bans is far from settled. The rush to ban access to digital platforms is being fueled by "pop psychology" narratives and a collection of statistically flawed studies that do not meet the rigorous standards required for such a massive infringement on youth autonomy and constitutional rights.

The Lie of A "Settled" Consensus

The current legislative push relies heavily on a specific, media-friendly narrative that the "great rewiring" of the adolescent brain is a proven fact. This theory suggests that smartphones and social media are the primary, if not sole, drivers of a global uptick in teen anxiety, depression, eating disorders, self harm, etc. While this narrative makes for a compelling airport-bookstore read, it quickly collapses under the scrutiny of the broader scientific community.

Independent researchers, including developmental psychologists from institutions like the University of California, Irvine, and Brown University, have repeatedly found that the evidence for such claims is mixed, blurry, and often contradictory. Large-scale meta-analyses covering dozens of countries have failed to show a consistent, measurable association between the rollout of social media and a decline in global well-being. In reality, we are seeing a classic case of what many of our middle school science teachers warned us about: "correlation" being sold as “causation."  

Additionally, the studies used to support these measures often fail to account for or exclude significant alternative explanations for rising teen anxiety and depression, such as the lasting impact of pandemic-era isolation, the persistent threat of school gun violence, and mounting economic or climate-related stress. By focusing narrowly on social media, these findings frequently overlook the broader societal factors that also impact youth mental health.

The Cult of the "Anxious" Expert

The current push for blanket social media bans relies almost exclusively on the work of Jonathan Haidt, particularly his book The Anxious Generation. While Haidt is an amiable and brilliant storyteller, he is not a clinical psychologist or a specialist in child development. He is a social psychologist who writes about moral psychology at a business school. Nonetheless, the book has made it to every Best Seller list, and with Haidt revered as an expert on podcasts with massive reach, like Oprah, Joe Rogan, Michelle Obama, and Trevor Noah—his message has been heard by a large subset of society, which primarily relies on: no smartphones or social media before age 16, phone-free schools, and more “unsupervised, real-world independence.”

To highlight Haidt’s reach when it comes to legislation banning social media: the California committee analysis for the proposed California social media ban mentions Haidt 20 times; the Governor of Utah promoted the book as a “must-read” months before signing the nation’s first social media ban; Haidt is cited in bill analysis for the bill banning social media in Florida; his work is mentioned in a federal bill aiming to ban phones in schools; and he provided formal testimony before the U.S. Senate Judiciary Committee (Subcommittee on Technology, Privacy, and the Law) in May 2022. 

While Haidt’s research has been paramount to legislation stripping millions of young people of their rights to expression and connection, his conclusions are not without challenge, and many experts in the field argue that the evidence is less than ironclad. 

The “Bad Science” Fueling Social Media Bans

While we can admit that Jonathan Haidt’s "great rewiring" theory makes for a gripping narrative, we cannot ignore that independent researchers and statisticians have identified significant flaws in the data used to justify it. Which means we are currently watching policymakers legislate blanket bans based on evidence that would be rejected in almost any other field of public health.

The reality is that research has consistently disproven the oft-assumed link between social media use and poor mental health in youth, and actually indicates that moderate internet use is a net positive for teens’ development, and negative outcomes are usually due to either lack of access or excessive use. In one major study of 100,000 adolescents, a “U-shaped association emerged where moderate social media use was associated with the best well-being outcomes, while both no use and highest use were associated with poorer well-being.” We also know that young people’s relationship with social media is complex, as it provides them essential spaces for civic engagement, identity exploration, and community building—particularly for LGBTQ+ and marginalized youth who may lack support in their physical environments. 

But again, the image Haidt presents in his book is increasingly at odds with the broader academic consensus. As mentioned, critics argue that the evidence for the mental health impacts of social media is mixed, blurry, and often misinterpreted. NYU statistics expert Aaron Brown, writing for Reason, notes that many of the studies in Haidt’s exhaustive reference list are statistically unreliable or fail to show a strong causal link. Prof. Candace Odgers, a leading voice in psychological science, explains the "selection effect" that legislators often ignore:

“Hundreds of researchers, myself included, have searched for the kind of large effects suggested by Haidt. Our efforts have produced a mix of no, small and mixed associations. Most data are correlative. When associations over time are found, they suggest not that social-media use predicts or causes depression, but that young people who already have mental-health problems use such platforms more often or in different ways from their healthy peers.”

This raises a fundamental question of legislative responsibility: If the science is not settled, how can legislators confidently declare a “public health crisis” to justify stripping away young people’s First Amendment rights? By bypassing the rigorous, nuanced findings of the scientific community in favor of a more convenient narrative, legislators are choosing emotion over evidence. Before imposing such draconian restrictions on young people’s access to information, policymakers have an obligation to do the heavy lifting: to dig into the actual research and listen to the experts who are sounding the alarm on oversimplified conclusions.

The Dangers of "Social Contagion" Narrative

Perhaps the most troubling aspect of Haidt’s crusade is its overlap with ideological rhetoric that pathologizes the identities of marginalized youth, and how that makes its way through efforts to ban social media for youth. A recurring theme in the literature favored by proponents of social media bans is the idea of "social contagion"—specifically regarding the rise in young people identifying as transgender or non-binary. Haidt dedicates an entire chapter of his book to this (ch.6, pt 3, p. 165), talking about “Why Social Media Harms Girls More Than Boys,” stating that: 

“The recent growth in diagnoses of gender dysphoria may also be related in part to social media trends, [...] the fact that gender dysphoria is now being diagnosed among many adolescents who showed no signs of it as children all indicate the social influence and sociogenic transmission may be at work as well.”

These harmful theories suggesting that social media is "infecting" young people with gender dysphoria are false and not supported by peer-reviewed clinical research. But by legitimizing "experts" who promote these debunked theories, legislators—especially those in states like California who pride themselves on being a sanctuary for LGBTQ+ youth—are inadvertently platforming the same rhetoric used in other states to ban gender affirming care for youth. This "social contagion" narrative is a tool of exclusion, not a scientific reality, and we must be wary of any "public health" argument that treats community-building and self-discovery among marginalized young people as a "purported mental illness" spread via TikTok.

A Better Path: Digital Wellness, Not Bans

Fortunately, there is a measured, evidence-based alternative already emerging. California's A.B. 2071, for instance, is a student-authored "digital wellness" bill that offers a measured, evidence-based alternative rather than prohibition. The bill advocates for a curriculum that teaches students how to manage algorithms, recognize cyberbullying, and regulate their own relationship with technology. Instead of trying to completely shield young people from social media, education-based approaches empower young people and have the benefit of providing skills that stay with a young person long after they leave the classroom. 

JustLeadershipUSA, a criminal justice organization, has a slogan that rings true in this instance too: “Those closest to the problem are closest to the solution.” So let’s start listening to what our young people are asking us for—more education—instead of imposing paternalistic, disempowering bans.

Legislating With Precision instead of Emotion 

Adolescent mental health struggles are a complex, multifaceted crisis. It is a crisis that has existed for as long as time, and has been driven by economic instability, the opioid epidemic, the threat of school violence, amongst other issues. To pin all of society's woes on a smartphone app is not just a scientific error; it is a policy failure that ignores the real, material needs of young people both online and off.

Legislators must stop legislating as "anxious parents" and start acting as measured policymakers. Because for some youth, social media platforms are a lifeline. UNICEF and other global human rights organizations have warned that age-related restrictions and blanket bans can backfire in three critical ways: isolating marginalized youth (like LGBTQ+ youth, students in rural areas, foster youth, or those with disabilities) who social media is often the only place they can find a supportive community; necessitating invasive mass collection of biometric data or government-issued IDs from all users, including adults; and pushing young people toward less-regulated, "darker" corners of the web where content moderation is non-existent and the risks of actual exploitation are significantly higher.

Legislators have a valid interest in protecting children, but that interest must be pursued through tailored, measured approaches. We cannot allow emotions or a collection of flawed data sets to justify a historic rollback of digital rights. 

The UK’s AI Security Institute evaluated GPT-5.5’s ability to find security vulnerabilities, and found that it is comparable to Claude Mythos. Note that the OpenAI model is generally available.

Here is the Institute’s evaluation of Mythos.

And here is an analysis of a smaller, cheaper model. It requires more scaffolding from the prompter, but it is also just as good.

The two countries are headed in different directions on energy.

The question is when, not if, U.S. and European auto markets will open up to Chinese EV investment.

Karen Evans, who had led the agency since December, is the latest official to be removed from FEMA.

The nation's government said such cases create "uncertainty" for business. The effort mirrors those of Republicans in the U.S.

EPA and the State Department say the lawsuit is undermining federal authority. DOJ has lost similar cases against states.

Atoco's shipping-container-sized machine will produce up to 1,057 gallons of water daily and can be installed at data centers, hospitals and other critical infrastructure.

This year’s early season wildfires have overwhelmed fire crews in Argentina, Chile and Japan, while fueling historic blazes in the U.S. and Southeast Asia.

The move sets up a fight with the United States, which opposes carbon pricing.

Mozambique, South Africa and Zimbabwe experienced unusually heavy rains in recent months, with the region's worst flooding in years.

MIT engineers have developed a new way to amplify the T-cell response to mRNA vaccines — an advance that could lead to much more powerful cancer vaccines and stronger protection against infectious diseases.

Most vaccines generate both antibodies and T cells that can target the vaccine antigen by activating antigen-presenting cells, such as dendritic cells. In this study, the researchers boosted the T-cell response with a new type of vaccine adjuvant (a material that can help stimulate the immune system). The new adjuvant consists of mRNA molecules encoding genes that turn on immune signaling pathways and promote a supercharged T-cell response. 

In studies in mice, this mRNA-encoded adjuvant enabled the immune system to completely eradicate most tumors, either on its own or delivered along with a tumor antigen. The adjuvant also boosted the T-cell response to vaccines against influenza and Covid-19.

“When these adjuvant mRNAs are included in the vaccines, the number of antigen-targeted T cells is substantially increased. These T cells play an important role in the immune response, assisting in the clearance of virally infected cells or, in the case of cancer, killing cancerous cells,” says Daniel Anderson, a professor in MIT’s Department of Chemical Engineering and a member of MIT’s Koch Institute for Integrative Cancer Research and Institute for Medical Engineering and Science.

Anderson and Christopher Garris, an assistant professor at Harvard Medical School and Massachusetts General Hospital, are the senior authors of the study, which appears today in Nature Biotechnology. The paper’s lead authors are Akash Gupta, a former Koch Institute research scientist who is now an assistant professor at the University of Houston; Kaelan Reed, an MIT graduate student; and Riddha Das, a research fellow at Harvard Medical School and MGH. Robert Langer, the David H. Koch Institute Professor at MIT, and Ralph Weissleder, a professor of radiology and systems biology at MGH and Harvard Medical School, are also authors.

More powerful vaccines

Vaccines that stimulate the body’s immune system to attack tumors have shown promise in clinical trials, and a handful have been FDA-approved for certain cancers. In some patients, these vaccines stimulate a strong response, but in others, a weak response fails to kill the cancerous cells.

The MIT-MGH team wanted to find a way to make those immune responses more powerful. One way to do that is to deliver immune-stimulating molecules called cytokines along with a vaccine. However, cytokines can overstimulate the immune system, leading to potentially severe side effects.

As an alternative approach, the researchers decided to deliver mRNA strands encoding two genes, IRF8 and NIK, which are involved in antigen presentation and can switch immune cells into a more active state.

NIK is an enzyme that activates a signaling pathway involved in immunity and inflammation, while IRF8 is a transcription factor that helps program dendritic cells, particularly a subset called cDC1, which are especially effective at activating T cells. These antigen-presenting cells can digest foreign antigens and present them to T cells, stimulating the T cells to mount an immune response against the antigen.

“We see that the dendritic cells start shifting toward a more cDC1 phenotype, which is the most important dendritic cell phenotype and can generate a stronger T-cell response,” Gupta says. 

The researchers packaged the mRNA in lipid nanoparticles similar to those used to deliver mRNA Covid vaccines, but with a different chemical composition that promotes their delivery to the spleen after being injected intravenously. 

Inside the spleen, the particles encounter antigen-presenting cells, including dendritic cells. Within 24 hours, these cells begin expressing IRF8 and NIK, and both of these pathways help drive dendritic cells to mature and become activated so that they can prime an anti-tumor response. 

Over a few days to a week, the T-cell population expands. These T cells, along with other immune cells such as natural killer (NK) cells, can then recognize and attack tumors.

“Most cancer immunotherapies rely on external signals to activate immune cells. We take a different approach — reprogramming immune cells from within by targeting their internal signaling machinery, enabling a more potent and durable anti-tumor response,” Das says. 

Stronger T cells

The researchers tested the immune-remodeling mRNAs in several mouse models of cancer, including an aggressive bladder cancer, colon carcinoma, melanoma, and metastatic lung cancer. In nearly all of these mice, the injected mRNA stimulated a strong T-cell response that significantly slowed tumor growth and in many cases completely eradicated the tumors. This happened even when the mice were not given a vaccine against a specific cancer antigen. When they were, the response was even stronger.

“We showed that you can get an anti-cancer response with these adjuvants without including the antigen, just by activating the immune system. However, cancer-specific antigens with the adjuvants in a vaccine further improved the responses,” Anderson says.

The mRNA adjuvant also enhanced the immune response to immunotherapy drugs called checkpoint blockade inhibitors. These drugs, which work by lifting a brake that tumor cells put on T cells, are FDA-approved to treat several kinds of cancer. These drugs don’t work for all patients, but combining them with the mRNA vaccine adjuvant could offer a way to make them more effective, the researchers say.

“The microenvironment of solid tumors is often hostile to T cells and represents a major barrier to effective immunotherapy. We find that immune remodeling with these adjuvants creates a T cell–permissive environment and promotes tumor rejection,” Garris says.

The researchers also explored whether their new adjuvant could boost the immune response to vaccination against viral infection. When they delivered the mRNA particles along with Covid or flu vaccines, they found that the vaccine generated a 10-to-15-fold stronger T cell response in the mice.

The researchers now plan to test this approach in additional animal models, in hopes of developing it for use in both cancer and infectious diseases. 

“While there are differences between the mouse systems that we’ve worked in and humans, we are optimistic that these adjuvants will work in humans and could improve a range of different vaccines,” Anderson says.

The research was funded by Sanofi, the National Institutes of Health, the Marble Center for Cancer Nanomedicine, and the Koch Institute Support (core) Grant from the National Cancer Institute.

Nature Climate Change, Published online: 13 May 2026; doi:10.1038/s41558-026-02631-y

Assessments of coastal ecosystem resilience typically consider the impacts of annual mean sea-level rise, while increases in the seasonal sea-level cycle could also affect intertidal ecosystems. The authors show how such increases can threaten intertidal zones through altering the frequency and duration of inundation and emergence events.

Nature Climate Change, Published online: 13 May 2026; doi:10.1038/s41558-026-02630-z

Climate-friendly intentions do not always translate into action. This Review synthesizes evidence on the intrapersonal, social and structural mechanisms underlying this gap and outlines interventions that offer actionable strategies to close it.

Nature Climate Change, Published online: 13 May 2026; doi:10.1038/s41558-026-02639-4

The carbon sink of tropical forests is in part constrained by biomass turnover. This study assesses aboveground biomass turnover in the Amazon and finds that convective storms are the main driver of spatial variation in turnover and future climate impacts will lead to accelerated biomass turnover.

Last week, Instagram ended its opt-in, and therefore rarely used, end-to-end encryption feature. Years after publicly promising to provide the privacy protections of end-to-end encryption across its platforms by default, it instead gave up on that technical challenge. Now, we've all lost an option for safer conversations on one of the biggest social media platforms in the world.

In an announcement in 2023, Meta bragged about how it had successfully encrypted Messenger, and teased that Instagram was in progress. Even before then, they’d talked about how important encryption was in Messenger and Instagram in a white paper published in 2022, stating: 

We want people to have a trusted private space that’s safe and secure, which is why we’re taking our time to thoughtfully build and implement e2ee by default across Messenger and Instagram DMs.

So where did the reversal come from? In a statement, Meta claimed that, “Very few people were opting in to end-to-end encrypted messaging in DMs.” This isn’t all that surprising, as turning it on was an optional four-step process that few people knew about. Defaults matter, and Meta’s choice to blame people for failing to opt into this feature is proof of how much. In that same statement, the company pointed people to WhatsApp for access to encrypted messaging. Yet if Meta truly wanted people to have a trusted private space to communicate, it would meet them everywhere they are: on WhatsApp, on Messenger, and on Instagram.

But at least Meta was straightforward about the fact that it will not continue to support or work on this feature. That's rare. Most tech company promises aren’t broken explicitly, they just remain undelivered long enough to be forgotten. 

This is particularly disappointing as other companies take even bigger swings, like Google and Apple working together to implement end-to-end encryption over Rich Communication Services (RCS), and Signal’s continued work to make its app simpler and easier to use for everyone.

Meta abandoning this principle is disheartening, especially as we are still waiting for other promised features from the company, like end-to-end encryption in Facebook Messenger group messages. Instead of blaming users for not using these sorts of features and then abandoning the promise of delivery, Meta—and other tech companies—should start by enabling strong privacy protective features by default.

On April 28, 2025, the power grid serving continental Spain and Portugal went down, causing gridlock in cities, cutting communications networks, and stranding people on trains, in airports, and in elevators all across the Iberian peninsula and briefly in a small area in southwest France close to the Spanish border. The unprecedented, massive blackout lasted as long as 12 hours in some areas, including in the capital city, Madrid. Not surprisingly, placing blame for the outage was rapid. Quick reactions pointed to cyberattack, sabotage, and natural phenomena such as solar flares. 

But such theories were quickly laid to rest, and a panel of experts was formed to determine exactly what caused the blackout. After a year following the outage — and after much analysis by many experts — there isn’t a simple answer: In short, no one technology was to blame. While solar and wind generation was high, experts agree that the renewables weren’t at fault. 

In this Q&A, Pablo Duenas-Martinez, a research scientist at the MIT Energy Initiative and an assistant professor at Universidad Pontificia Comillas in Madrid, provides an update.

Q: How does a proper, well-functioning power grid behave, and what does the system operator do to help?

A: There are two components to the flows on a power grid. One is “active power” — the part that lights up our light bulbs and runs our engines. With active power, the demand on the grid must always equal supply. The other component is “reactive power,” the part we can’t see but controls the voltage at which the power is delivered so it suits our devices. If voltage is too low, lights will flicker. If voltage is too high, devices may not only fail to work, but be damaged beyond repair.

The operator of the transmission system — the TSO — must control both components, and that can be tricky. Active power supply and demand are largely coordinated through markets. But controlling reactive power is harder. The main way the TSO can control it is to call on operators of conventional power generators, so generators burning natural gas, or coal, or nuclear plants. Those systems can be adjusted to either absorb or inject reactive power as needed to control voltage on the power grid — indeed, they are typically required by law to provide “reactive power control.”

In contrast, solar and wind generators always absorb reactive power. The large solar and wind sources can provide reactive power control when it’s needed, but doing so is costly for them — and in Spain, unlike in most countries, it’s not mandated by law, so they typically don’t do it. Meanwhile, there are many small solar systems — imagine lots of rooftop solar installations and small solar farms. Those small systems are directly connected to the distribution system. As a result, they’re not controlled by the TSO; the TSO may not even know whether they’ve shut down or are still running and absorbing reactive power.

Sometimes, fluctuations in voltage called “oscillations” can happen on a power grid: for example, when a transmission line or a generator is connected or disconnected. Oscillations can increase and decrease the voltage rapidly, and if voltage gets too high, generators and user devices can start “tripping” — that is, automatically disconnecting to prevent being damaged. Operators have standard protocols to follow to bring oscillations under control.

Q: So what happened on April 28 of last year?

A: The Spanish grid is loosely connected to the French grid and in practice is merged with the grid serving Portugal. Within Spain, we have many large solar and wind farms and lots of small installations of solar systems, many located in the southwestern area of the country. On April 28 — as on most spring days, when demand is low — about two-thirds of the power on the grid came from renewable sources. The rest came from a mix of nuclear and natural gas plants.

The day before the blackout, the TSO confirmed that there were no conventional generators scheduled to run. So, to ensure safe operation the next day, the TSO took steps that included dispatching 12 conventional generators, 10 of them to provide reactive power control. One of the units in the south called him back and said, “I won’t be available. I cannot switch on tomorrow.” The TSO thought he had things under control and continued operations with only nine units available to provide reactive power control.

During the morning on April 28, several small oscillations on the power grid were detected coming from Europe, plus one from Spain. To stabilize the weakened grid, the TSO connected additional transmission lines and took other technical actions.

At 12:19 p.m., a major oscillation was detected on the grid, again coming from Europe. In response, the TSO — again following standard protocol — reduced exports to Portugal, switched the flows to France from alternating current to direct current, and connected five more transmission lines within Spain. While those steps stabilized the voltage, the TSO recognized that there was now limited capacity on the system to control voltage. So, he called on a different conventional generator to begin running. But that unit couldn’t be available for an hour.

Suddenly, as a consequence of the previous actions, the voltage increased dramatically, and generating units began to trip. Within half-a-second, many of the small solar generators — especially prone to damage from high voltages — automatically shut down. Twenty milliseconds later, a big solar plant in southwestern Spain tripped. Because the solar plants were no longer absorbing reactive power, voltage on the system went up even more, and more systems shut down. The grid went into what some have called a death spiral, resulting in a total blackout across the Iberian peninsula and some areas of southern France.

Q: What have we learned from this Iberian blackout, and have changes been implemented to ensure that the same won’t happen again — or happen elsewhere?

A: A resilient power system must prevent, mitigate, respond, and recover. In this case, the first three components clearly failed. Preventive mechanisms were insufficient; they initially mitigated the oscillatory events, but left the system in a weakened state, and the response triggered the death spiral that led to the final blackout.

The good news is that the recovery was quick. The northern and southern sections of the peninsula had power back within a few hours. I live in the suburbs of Madrid, and I had power back just six hours later. My parents live downtown, so that was far more challenging — a big city with a large, complex load. Even so, they had power back in 12 hours — and 12 hours is quick for such a major, widespread blackout.

In the end, experts and analysts have agreed that the blackout was caused by a series of events that were all happening in the same place, at the same time. And the experience did provide a number of valuable learnings:

Lesson 1

The experience clearly demonstrated the importance of having a sufficient number of conventional power plants prepared to provide reactive power control, or to turn on right away when called on. There’s a recommendation calling for a set ratio between conventional generators and renewables on a power grid. Conventional facilities such as nuclear, hydroelectric, and fossil fuel plants rely on heavy metal wheels to generate electricity. Those massive rotating wheels have high inertia, so they’ll keep running and can help stabilize frequency and voltage even when solar and wind plants shut down. Before the blackout, Spain had a sufficient number of “rotating units” to meet the recommended ratio. However, in southern Spain, there was just one such unit — well below the recommended number, given the huge number of small solar units plus several large solar units in the area.

The message here is that you can't just look at the country as a whole. You have to look at regions. Voltage is a local problem that can propagate at the system level. Before the blackout, southern Spain typically had at most three conventional power plants. Now the region usually has six or seven at the ready to help with reactive power control.

Lesson 2

The rules or protocols for controlling reactive power and dealing with oscillations were not well designed. By law, rotating generators must automatically — and without being paid — do a defined amount of reactive power control. But making the needed operational change costs money, and a plant can do less than the required amount and not incur any kind of penalty. However, the TSO doesn’t know in advance how much reactive power control a given plant will actually do. Now that loophole in the law has been reviewed by the regulator.

The main rules have been updated, and now also require large solar and wind power plants — those above 5 megawatts — to provide reactive power control. More importantly, voltage control will be auctioned and remunerated, incentivizing rotating conventional generators and bringing in a new money stream for solar and wind power plants. Those power plants that do not upgrade their installation for voltage control might be disconnected by the TSO if local voltage issues arise.

Lesson 3

Another learning concerns the many small solar power generators and the protections that cause them to trip. The TSO doesn’t know in advance when this may happen because the small solar sources are directly connected to the distribution system, and therefore are under the umbrella of the distribution system operator. So, the learning here is that there should be more communication and coordination between the operator of the transmission system — the TSO — and the operator of the distribution system.

Lesson 4

In most countries, laws dictate a range of voltage that is approved. In Spain, the upper limit is high — in fact, it’s very near a voltage at which equipment may be damaged. And the Spanish grid tends to hover close to that upper limit, even during normal operation, and that can be a big problem: If there are strong oscillations — as there were leading up to the blackout — voltage can reach that upper limit, and protections on devices will automatically trip. The panel of experts has strongly recommended to lower this upper limit in Spain and align it with the rules in neighboring countries, including Portugal and France. The TSO is still studying the recommended change.

Lesson 5

During normal operation, the TSO controls voltage by activating rotating generators that can provide reactive power control. But as we saw in conditions leading up to the blackout, the TSO doesn’t always have rotating generators available.

Theoretically, TSOs have two more ways to control voltage. They can connect a device called a shunt reactor, which absorbs reactive power — a means of dealing with voltage rise. And they can regulate voltage directly using a “STATCOM,” a special device that provides rapid, dynamic voltage control.

However, neither the shunt reactors nor the STATCOM could help prevent the blackout. The shunt reactors available at that time were operated manually, and collapse of the grid happened so quickly that the TSO didn’t have time to connect them. And at that time, there was a single STATCOM device on the Spanish system. Planning was under way to install three more devices — and that installation is being rapidly completed.

From newspaper articles and off-the-record conversations, I’ve learned that the system has — due to similar external circumstances — been close to blackout again during the past year. But in part due to the learnings and to changes that have been implemented as a result, it didn’t happen again.

The hallowed history of student pranks (often known as hacks) at MIT includes the annual Baker House Piano Drop and the MIT weather balloon at the Harvard-Yale football game in 1982. One hack that has shown remarkable staying power in local lore is the 1958 measurement of the Massachusetts Ave. Bridge in “smoots,” a now accepted unit of meausrement named for the 5-foot, 7-inch Oliver R. Smoot Jr. ’62. Then a first-year pledge at the Lambda Chi Alpha fraternity, Smoot famously laid down hundreds of times across the span one storied night as his peers painted markers across the bridge, totaling 364.4 smoots (plus 1 ear). Nearly 70 years later, the smoot markings remain.

On April 4, an MIT team set out on a similar journey across the Charles River to pull off a new hack, this time measuring the Longfellow Bridge in “kleins.” This new measurement is named after Smoot’s classmate Martin Klein ’62. One klein (4 feet, 9.5 inches) is equal to 0.85820896 smoots. The expedition was undertaken in honor of both Smoot and the 85th birthday of Klein.

Known as the father of commercial side-scan sonar, Martin Klein serves on the MIT Sea Grant Advisory Board and the MIT Museum Collections Committee. He is a life fellow of both the Marine Technology Society and the Explorers Club, an international organization dedicated to the advancement of field exploration and scientific inquiry. His sonar technology has been used worldwide to help locate countless famous shipwrecks, including the Titanic, the World War I ocean liner RMS Lusitania, and the treasure-laden Nuestra Señora de Atocha.

Appropriately, the MIT team used a “side-scan” method to survey the Longfellow Bridge. Reclined on a custom-engineered wooden cart topped with a mission-specific chaise lounge pillow, Klein himself acted as the official observation device — by looking to the sides — as the team pulled him along the bridge. Some of the noted anomalies and discoveries included a Duck Boat passing underneath, a mermaid tail, a kayak paddle, a sleeping goose, and a tenacious survey team.

The initiative was spearheaded by Makenna Reilly, a second-year undergraduate in mechanical engineering, and Andrew Bennett ’85, PhD ’97, MIT Sea Grant education administrator and senior lecturer in the Department of Mechanical Engineering (MechE). Over a dozen surveyors joined the expedition, including alumni, faculty, and staff from MechE, MIT Sea Grant, MIT Edgerton Center, MIT Museum Hart Nautical Collections, Harvard Extension School, and Woods Hole Oceanographic Institution. MIT students also joined the effort, including senior Teagan Sullivan, junior Adrienne Lai, and graduate students Ansel Garcia-Langley, Erin Menezes, Manuel Valencia, and Gerardo Berlanga Molina.

The Longfellow Bridge was determined to be 442 kleins (plus 2 legs) and was celebrated as the “Shortfellow Bridge” in a ceremony following the event. 

One klein = 57.5 inches = 146.05 centimeters = 1.4605 meters = .0009075126 miles = 1.597222 yards = 4.791667 feet = .0007886069 nautical miles = .007260087 furlongs = 0.7986111 fathoms = 172.5 barleycorns = 292,100,000 beard seconds = 647.4421 Ligne = 14.375 horse hands = 4.819655 shaku = .85820896 smoots.

Additional participants in the event include:

• Elisabeth (Libby) Meier, assistant curator for the Hart Nautical Collections at the MIT Museum;
• Dana Yoerger, PhD ’82, senior scientist applied ocean physics and engineering at WHOI;
• Professor George Buckley, assistant director of sustainability at Harvard University Extension School and diver of the year of the Boston Sea Rovers;
• Paul K. Matthias, senior program manager of the Ocean Observatories Initiative at the WHOI;
• Jim Bales, associate director of the Edgerton Center at MIT;
• John Freidah of MechE; and
• Joice Himawan ’83.