June 13, 20256 min readAir-Conditioning Can Surprisingly Help the Power Grid during Extreme HeatSwitching on air-conditioning during extreme heat doesn’t have to make us feel guilty—it can actually boost power grid reliability and help bring more renewable energy onlineBy Johanna Mathieu & The Conversation US Imagedepotpro/Getty ImagesThe following essay is reprinted with permission from The Conversation, an online publication covering the latest research.As summer arrives, people are turning on air conditioners in most of the U.S. But if you’re like me, you always feel a little guilty about that. Past generations managed without air conditioning – do I really need it? And how bad is it to use all this electricity for cooling in a warming world?If I leave my air conditioner off, I get too hot. But if everyone turns on their air conditioner at the same time, electricity demand spikes, which can force power grid operators to activate some of the most expensive, and dirtiest, power plants. Sometimes those spikes can ask too much of the grid and lead to brownouts or blackouts.On supporting science journalismIf you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.Research I recently published with a team of scholars makes me feel a little better, though. We have found that it is possible to coordinate the operation of large numbers of home air-conditioning units, balancing supply and demand on the power grid – and without making people endure high temperatures inside their homes.Studies along these lines, using remote control of air conditioners to support the grid, have for many years explored theoretical possibilities like this. However, few approaches have been demonstrated in practice and never for such a high-value application and at this scale. The system we developed not only demonstrated the ability to balance the grid on timescales of seconds, but also proved it was possible to do so without affecting residents’ comfort.The benefits include increasing the reliability of the power grid, which makes it easier for the grid to accept more renewable energy. Our goal is to turn air conditioners from a challenge for the power grid into an asset, supporting a shift away from fossil fuels toward cleaner energy.Adjustable equipmentMy research focuses on batteries, solar panels and electric equipment – such as electric vehicles, water heaters, air conditioners and heat pumps – that can adjust itself to consume different amounts of energy at different times.Originally, the U.S. electric grid was built to transport electricity from large power plants to customers’ homes and businesses. And originally, power plants were large, centralized operations that burned coal or natural gas, or harvested energy from nuclear reactions. These plants were typically always available and could adjust how much power they generated in response to customer demand, so the grid would be balanced between power coming in from producers and being used by consumers.But the grid has changed. There are more renewable energy sources, from which power isn’t always available – like solar panels at night or wind turbines on calm days. And there are the devices and equipment I study. These newer options, called “distributed energy resources,” generate or store energy near where consumers need it – or adjust how much energy they’re using in real time.One aspect of the grid hasn’t changed, though: There’s not much storage built into the system. So every time you turn on a light, for a moment there’s not enough electricity to supply everything that wants it right then: The grid needs a power producer to generate a little more power. And when you turn off a light, there’s a little too much: A power producer needs to ramp down.The way power plants know what real-time power adjustments are needed is by closely monitoring the grid frequency. The goal is to provide electricity at a constant frequency – 60 hertz – at all times. If more power is needed than is being produced, the frequency drops and a power plant boosts output. If there’s too much power being produced, the frequency rises and a power plant slows production a little. These actions, a process called “frequency regulation,” happen in a matter of seconds to keep the grid balanced.This output flexibility, primarily from power plants, is key to keeping the lights on for everyone.Finding new optionsI’m interested in how distributed energy resources can improve flexibility in the grid. They can release more energy, or consume less, to respond to the changing supply or demand, and help balance the grid, ensuring the frequency remains near 60 hertz.Some people fear that doing so might be invasive, giving someone outside your home the ability to control your battery or air conditioner. Therefore, we wanted to see if we could help balance the grid with frequency regulation using home air-conditioning units rather than power plants – without affecting how residents use their appliances or how comfortable they are in their homes.From 2019 to 2023, my group at the University of Michigan tried this approach, in collaboration with researchers at Pecan Street Inc., Los Alamos National Laboratory and the University of California, Berkeley, with funding from the U.S. Department of Energy Advanced Research Projects Agency-Energy.We recruited 100 homeowners in Austin, Texas, to do a real-world test of our system. All the homes had whole-house forced-air cooling systems, which we connected to custom control boards and sensors the owners allowed us to install in their homes. This equipment let us send instructions to the air-conditioning units based on the frequency of the grid.Before I explain how the system worked, I first need to explain how thermostats work. When people set thermostats, they pick a temperature, and the thermostat switches the air-conditioning compressor on and off to maintain the air temperature within a small range around that set point. If the temperature is set at 68 degrees, the thermostat turns the AC on when the temperature is, say, 70, and turns it off when it’s cooled down to, say, 66.Every few seconds, our system slightly changed the timing of air-conditioning compressor switching for some of the 100 air conditioners, causing the units’ aggregate power consumption to change. In this way, our small group of home air conditioners reacted to grid changes the way a power plant would – using more or less energy to balance the grid and keep the frequency near 60 hertz.Moreover, our system was designed to keep home temperatures within the same small temperature range around the set point.Testing the approachWe ran our system in four tests, each lasting one hour. We found two encouraging results.First, the air conditioners were able to provide frequency regulation at least as accurately as a traditional power plant. Therefore, we showed that air conditioners could play a significant role in increasing grid flexibility. But perhaps more importantly – at least in terms of encouraging people to participate in these types of systems – we found that we were able to do so without affecting people’s comfort in their homes.We found that home temperatures did not deviate more than 1.6 Fahrenheit from their set point. Homeowners were allowed to override the controls if they got uncomfortable, but most didn’t. For most tests, we received zero override requests. In the worst case, we received override requests from two of the 100 homes in our test.In practice, this sort of technology could be added to commercially available internet-connected thermostats. In exchange for credits on their energy bills, users could choose to join a service run by the thermostat company, their utility provider or some other third party.Then people could turn on the air conditioning in the summer heat without that pang of guilt, knowing they were helping to make the grid more reliable and more capable of accommodating renewable energy sources – without sacrificing their own comfort in the process.This article was originally published on The Conversation. Read the original article.

Sienna Net-Zero Home / billionBricksSave this picture!© Ron Mendoza , Mark Twain C , BB teamHouses, Sustainability•Quezon City, Philippines Architects: billionBricks Area Area of this architecture project Area:  45 m² Year Completion year of this architecture project Year:  2024 Photographs Photographs:Ron Mendoza , Mark Twain C , BB teamMore SpecsLess Specs Save this picture! Text description provided by the architects. Built to address homelessness and climate change, the Sienna Net-Zero Home is a self-sustaining, solar-powered, cost-efficient, and compact housing solution. This climate-responsive and affordable home, located in Quezon City, Philippines, represents a revolutionary vision for social housing through its integration of thoughtful design, sustainability, and energy self-sufficiency.Save this picture!Save this picture!Save this picture!Designed with the unique tropical climate of the Philippines in mind, the Sienna Home prioritizes natural ventilation, passive cooling, and rainwater management to enhance indoor comfort and reduce reliance on artificial cooling systems. The compact 4.5m x 5.1m floor plan has been meticulously optimized for functionality, offering a flexible layout that grows and adapts to the families living in them.Save this picture!Save this picture!Save this picture!A key architectural feature is BillionBricks' innovative Powershade technology - an advanced solar roofing system that serves multiple purposes. Beyond generating clean, renewable energy, it acts as a protective heat barrier, reducing indoor temperatures and improving thermal comfort. Unlike conventional solar panels, Powershade seamlessly integrates with the home's structure, providing reliable energy generation while doubling as a durable roof. This makes the Sienna Home energy-positive, meaning it produces more electricity than it consumes, lowering utility costs and promoting long-term energy independence. Excess power can also be stored or sold back to the grid, creating an additional financial benefit for homeowners.Save this picture!When multiple Sienna Homes are built together, the innovative PowerShade roofing solution transcends its role as an individual energy source and transforms into a utility-scale solar rooftop farm, capable of powering essential community facilities and generating additional income. This shared energy infrastructure fosters a sense of collective empowerment, enabling residents to actively participate in a sustainable and financially rewarding energy ecosystem.Save this picture!Save this picture!The Sienna Home is built using lightweight prefabricated components, allowing for rapid on-site assembly while maintaining durability and structural integrity. This modular approach enables scalability, making it an ideal prototype for large-scale, cost-effective housing developments. The design also allows for future expansions, giving homeowners the flexibility to adapt their living spaces over time.Save this picture!Adhering to BP 220 social housing regulations, the unit features a 3-meter front setback and a 2-meter rear setback, ensuring proper ventilation, safety, and community-friendly spaces. Additionally, corner units include a 1.5-meter offset, enhancing privacy and accessibility within neighborhood layouts. Beyond providing a single-family residence, the Sienna House is designed to function within a larger sustainable community model, integrating shared green spaces, pedestrian pathways, and decentralized utilities. By promoting energy independence and environmental resilience, the project sets a new precedent for affordable yet high-quality housing solutions in rapidly urbanizing regions.Save this picture!The Sienna Home in Quezon City serves as a blueprint for future developments, proving that low-cost housing can be both architecturally compelling and socially transformative. By rethinking traditional housing models, BillionBricks is pioneering a future where affordability and sustainability are seamlessly integrated. Project gallerySee allShow less About this officebillionBricksOffice••• Published on June 15, 2025Cite: "Sienna Net-Zero Home / billionBricks" 14 Jun 2025. ArchDaily. Accessed . <https://www.archdaily.com/1031072/sienna-billionbricks&gt ISSN 0719-8884Save世界上最受欢迎的建筑网站现已推出你的母语版本!想浏览ArchDaily中国吗?是否 You've started following your first account!Did you know?You'll now receive updates based on what you follow! Personalize your stream and start following your favorite authors, offices and users.Go to my stream

Al Hajar Mountains in OmanL_B_Photography/Shutters​tock A section of Earth’s mantle beneath Oman appears to be unusually warm, in what researchers say may be the first known “ghost plume” – a column of hot rock emanating from the lower mantle without apparent volcanic activity on the surface. Mantle plumes are mysterious upwellings of molten rock believed to transmit heat from the core-mantle boundary to the Earth’s surface, far from the edges of tectonic plates. There are a dozen or so examples thought to occur underneath the middle of continental plates – for instance, beneath Yellowstone and the East African rift. “But these are all cases where you do have surface volcanism,” says Simone Pilia at the King Fahd University of Petroleum and Minerals in Saudi Arabia. Oman has no such volcanic clues. Pilia first came to suspect there was a plume beneath Oman “serendipitously” after he began analysing new seismic data from the region. He observed the velocity of waves generated by distant earthquakes slowed down in a cylindrical area beneath eastern Oman, indicating the rocks there were less rigid than the surrounding material due to high temperatures. Other independent seismic measurements showed key boundaries where minerals deep in the Earth change phases in a way consistent with a hot plume. These measurements suggest the plume extends more than 660 kilometres below the surface. The presence of a plume could also explain why the region has continued to rise in elevation long after tectonic compression – a geological process where the Earth’s crust is squeezed together – stopped. It also fits with models of what could have caused a shift in the movement of the Indian tectonic plate. “The more we gathered evidence, the more we were convinced that it is a plume,” says Pilia, who named the geologic feature the “Dani plume” after his son. Unmissable news about our planet delivered straight to your inbox every month. Sign up to newsletter “It’s plausible” that a plume indeed exists there, says Saskia Goes at Imperial College London, adding the study is “thorough”. However, she points out narrow plumes are notoriously difficult to detect. If it does exist, however, the presence of a “ghost plume” contained within the mantle by the relatively thick rocky layer beneath Oman would suggest there are others, says Pilia. “We’re convinced that the Dani plume is not alone.” If there are many other hidden plumes, it could mean more heat from the core is flowing directly through the mantle via plumes, rather than through slower convection, says Goes. “It has implications, potentially, for the evolution of the Earth if we get a different estimate of how much heat comes out of the mantle.” Journal referenceEarth and Planetary Science Letters DOI: 10.1016/j.epsl.2025.119467 Topics:

DJI Osmo Action 4. Adrian Kingsley-Hughes/ZDNETMultiple DJI Osmo Action 4 packages are on sale at Amazon. Both the Essential and Standard Combos have been discounted to $249, while the Adventure Combo has dropped to $349.DJI might not be the first name on people's lips when it comes to action cameras, but the company that's better known for its drones also has a really solid line of action cameras. And its latest device, the Osmo Action 4 camera, has some very impressive tricks up its sleeve.Also: One of the most versatile cameras I've used is not from Sony or Canon and it's on saleSo, what sets this action camera apart from the competition? Let's take a look. details View at Amazon First off, this is not just an action camera -- it's a pro-grade action camera.From a hardware point of view, the Osmo Action 4 features a 1/1.3-inch image sensor that can record 4K at up to 120 frames per second (fps). This sensor is combined with a wide-angle f/2.8 aperture lens that provides an ultra-wide field of view of up to 155°. And that's wide. Build quality and fit and finish are second to none. Adrian Kingsley-Hughes/ZDNETFor when the going gets rough, the Osmo Action 4 offers 360° HorizonSteady stabilization modes, including RockSteady 3.0/3.0+ for first-person video footage and HorizonBalancing/HorizonSteady modes for horizontal shots. That's pro-grade hardware right there.Also: This new AI video editor is an all-in-one production service for filmmakers - how to try itThe Osmo Action 4 also features a 10-bit D-Log M color mode. This mode allows the sensor to record over one billion colors and offers a wider dynamic range, giving you a video that is more vivid and that offers greater detail in the highlights and shadows. This mode, combined with an advanced color temperature sensor, means that the colors have a true-to-life feel regardless of whether you're shooting outdoors, indoors, or even underwater. The DJI Osmo Action 4 ready for action. Adrian Kingsley-Hughes/ZDNETI've added some video output from the Osmo Action 4 below. There are examples in both 1080p and 4K. To test the stabilization, I attached the camera to the truck and took it on some roads, some of which are pretty rough. The Osmo Action 4 had no problem with that terrain. I also popped the camera into the sea, just because. And again, no problem.I've also captured a few time-lapses with the camera -- not because I like clouds (well, actually, I do like clouds), but pointing a camera at a sky can be a good test of how it handles changing light. Also: I recommend this action camera to beginners and professional creators. Here's whyTimelapses with action cameras can suffer from unsightly exposure changes that cause the image to pulse, a condition known as exposure pumping. This issue can also cause the white balance to change noticeably in a video, but the Osmo Action 4 handled this test well.All the footage I've shot is what I've come to expect from a DJI camera, whether it's from an action camera or drone -- crisp, clear, vivid, and also nice and stable.The Osmo Action 4 is packed with various electronic image-stabilization (EIS) tech to ensure that your footage is smooth and on the horizon. It's worth noting the limitations of EIS -- it's not supported in slow-motion and timelapse modes, and the HorizonSteady and HorizonBalancing features are only available for video recorded at 1080p (16:9) or 2.7K (16:9) with a frame rate of 60fps or below. On the durability front, I've no concerns. I've subjected the Osmo Action 4 to a hard few days of testing, and it's not let me down or complained once. It takes impacts like a champ, and being underwater or in dirt and sand is no problem at all. Also: I'm a full-time Canon photographer, but this Nikon camera made me wonder if I'm missing outYou might think that this heavy-duty testing would be hard on the camera's tiny batteries, but you'd be wrong. Remember I said the Osmo Action 4 offered hours of battery life? Well, I wasn't kidding.  The Osmo Action 4's ultra-long life batteries are incredible.  Adrian Kingsley-Hughes/ZDNETDJI says that a single battery can deliver up to 160 minutes of 1080p/24fps video recording (at room temperature, with RockSteady on, Wi-Fi off, and screen off). That's over two and a half hours of recording time. In the real world, I was blown away by how much a single battery can deliver. I shot video and timelapse, messed around with a load of camera settings, and then transferred that footage to my iPhone, and still had 16% battery left.No action camera has delivered so much for me on one battery. The two extra batteries and the multifunction case that come as part of the Adventure Combo are worth the extra $100. Adrian Kingsley-Hughes/ZDNETAnd when you're ready to recharge, a 30W USB-C charger can take a battery from zero to 80% in 18 minutes. That's also impressive.What's more, the batteries are resistant to cold, offering up to 150 minutes of 1080p/24fps recording in temperatures as low as -20°C (-4°F). This resistance also blows the competition away.Even taking into account all these strong points, the Osmo Action 4 offers even more.The camera has 2x digital zoom for better composition, Voice Prompts that let you know what the camera is doing without looking, and Voice Control that lets you operate the device without touching the screen or using the app. The Osmo Action 4 also digitally hides the selfie stick from a variety of different shots, and you can even connect the DJI Mic to the camera via the USB-C port for better audio capture.Also: Yes, an Android tablet finally made me reconsider my iPad Pro loyaltyAs for price, the Osmo Action 4 Standard Combo bundle comes in at $399, while the Osmo Action 4 Adventure Combo, which comes with two extra Osmo Action Extreme batteries, an additional mini Osmo Action quick-release adapter mount, a battery case that acts as a power bank, and a 1.5-meter selfie stick, is $499.I'm in love with the Osmo Action 4. It's hands down the best, most versatile, most powerful action camera on the market today, offering pro-grade features at a price that definitely isn't pro-grade.  Everything included in the Action Combo bundle. DJIDJI Osmo Action 4 tech specsDimensions: 70.5×44.2×32.8mmWeight: 145gWaterproof: 18m, up to 60m with the optional waterproof case Microphones: 3Sensor 1/1.3-inch CMOSLens: FOV 155°, aperture f/2.8, focus distance 0.4m to ∞Max Photo Resolution: 3648×2736Max Video Resolution: 4K (4:3): 3840×2880@24/25/30/48/50/60fps and 4K (16:9): 3840×2160@24/25/30/48/50/60/100/120fpsISO Range: 100-12800Front Screen: 1.4-inch, 323ppi, 320×320Rear Screen: 2.25-inch, 326ppi, 360×640Front/Rear Screen Brightness: 750±50 cd/m² Storage: microSD (up to 512GB)Battery: 1770mAh, lab tested to offer up to 160 minutes of runtime (tested at room temperature - 25°C/77°F - and 1080p/24fps, with RockSteady on, Wi-Fi off, and screen off)Operating Temperature: -20° to 45° C (-4° to 113° F)This article was originally published in August of 2023 and updated in March 2025.Featured reviews

June 13, 20255 min readFive Climate Issues to Watch When Trump Goes to CanadaPresident Trump will attend the G7 summit on Sunday in a nation he threatened to annex. He will also be an outlier on climate issuesBy Sara Schonhardt & E&E News Saul Loeb/AFP via Getty ImagesCLIMATEWIRE | The world’s richest nations are gathering Sunday in the Canadian Rockies for a summit that could reveal whether President Donald Trump's policies are shaking global climate efforts.The Group of Seven meeting comes at a challenging time for international climate policy. Trump’s tariff seesaw has cast a shade over the global economy, and his domestic policies have threatened billions of dollars in funding for clean energy programs. Those pressures are colliding with record-breaking temperatures worldwide and explosive demand for energy, driven by power-hungry data centers linked to artificial intelligence technologies.On top of that, Trump has threatened to annex the host of the meeting — Canada — and members of his Cabinet have taken swipes at Europe’s use of renewable energy. Rather than being aligned with much of the world's assertion that fossil fuels should be tempered, Trump embraces the opposite position — drill for more oil and gas and keep burning coal, while repealing environmental regulations on the biggest sources of U.S. carbon pollution.On supporting science journalismIf you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.Those moves illustrate his rejection of climate science and underscore his outlying positions on global warming in the G7.Here are five things to know about the summit.Who will be there?The group comprises Canada, France, Germany, Italy, Japan, the United Kingdom and the United States — plus the European Union. Together they account for more than 40 percent of gross domestic product globally and around a quarter of all energy-related carbon dioxide pollution, according to the International Energy Agency. The U.S. is the only one among them that is not trying to hit a carbon reduction goal.Some emerging economies have also been invited, including Mexico, India, South Africa and Brazil, the host of this year’s COP30 climate talks in November.Ahead of the meeting, the office of Canada's prime minister, Mark Carney, said he and Brazilian President Luiz Inácio Lula da Silva agreed to strengthen cooperation on energy security and critical minerals. White House press secretary Karoline Leavitt said Trump would be having "quite a few" bilateral meetings but that his schedule was in flux.The G7 first came together 50 years ago following the Arab oil embargo. Since then, its seven members have all joined the United Nations Framework Convention on Climate Change and the Paris Agreement. The U.S. is the only nation in the group that has withdrawn from the Paris Agreement, which counts almost every country in the world as a signatory.What’s on the table?Among Canada’s top priorities as host are strengthening energy security and fortifying critical mineral supply chains. Carney would also like to see some agreement on joint wildfire action.Expanding supply chains for critical minerals — and competing more aggressively with China over those resources — could be areas of common ground among the leaders. Climate change is expected to remain divisive. Looming over the discussions will be tariffs — which Trump has applied across the board — because they will have an impact on the clean energy transition.“I think probably the majority of the conversation will be less about climate per se, or certainly not using climate action as the frame, but more about energy transition and infrastructure as a way of kind of bridging the known gaps between most of the G7 and where the United States is right now,” said Dan Baer, director of the Europe program at the Carnegie Endowment for International Peace.What are the possible outcomes?The leaders could issue a communique at the end of their meeting, but those statements are based on consensus, something that would be difficult to reach without other G7 countries capitulating to Trump. Bloomberg reported Wednesday that nations won’t try to reach a joint agreement, in part because bridging gaps on climate change could be too hard.Instead, Carney could issue a chair’s summary or joint statements based on certain issues.The question is how far Canada will go to accommodate the U.S., which could try to roll back past statements on advancing clean energy, said Andrew Light, former assistant secretary of Energy for international affairs, who led ministerial-level negotiations for the G7.“They might say, rather than watering everything down that we accomplished in the last four years, we just do a chair's statement, which summarizes the debate,” Light said. “That will show you that you didn't get consensus, but you also didn't get capitulation.”What to watch forIf there is a communique, Light says he’ll be looking for whether there is tougher language on China and any signal of support for science and the Paris Agreement. During his first term, Trump refused to support the Paris accord in the G7 and G20 declarations.The statement could avoid climate and energy issues entirely. But if it backtracks on those issues, that could be a sign that countries made a deal by trading climate-related language for something else, Light said.Baer of Carnegie said a statement framed around energy security and infrastructure could be seen as a “pragmatic adaptation” to the U.S. administration, rather than an indication that other leaders aren’t concerned about climate change.Climate activists have lower expectations.“Realistically, we can expect very little, if any, mention of climate change,” said Caroline Brouillette, executive director of Climate Action Network Canada.“The message we should be expecting from those leaders is that climate action remains a priority for the rest of the G7 … whether it's on the transition away from fossil fuels and supporting developing countries through climate finance,” she said. “Especially now that the U.S. is stepping back, we need countries, including Canada, to be stepping up.”Best- and worst-case scenariosThe challenge for Carney will be preventing any further rupture with Trump, analysts said.In 2018, Trump made a hasty exit from the G7 summit, also in Canada that year, due largely to trade disagreements. He retracted his support for the joint statement.“The best, [most] realistic case outcome is that things don't get worse,” said Baer.The worst-case scenario? Some kind of “highly personalized spat” that could add to the sense of disorder, he added.“I think the G7 on the one hand has the potential to be more important than ever, as fewer and fewer platforms for international cooperation seem to be able to take action,” Baer said. “So it's both very important and also I don't have super-high expectations.”Reprinted from E&E News with permission from POLITICO, LLC. Copyright 2025. E&E News provides essential news for energy and environment professionals.

June 13, 20253 min readCould Iran Have Been Close to Making a Nuclear Weapon? Uranium Enrichment ExplainedWhen Israeli aircraft recently struck a uranium-enrichment complex in the nation, Iran could have been days away from achieving “breakout,” the ability to quickly turn “yellowcake” uranium into bomb-grade fuel, with its new high-speed centrifugesBy Deni Ellis Béchard edited by Dean VisserMen work inside of a uranium conversion facility just outside the city of Isfahan, Iran, on March 30, 2005. The facility in Isfahan made hexaflouride gas, which was then enriched by feeding it into centrifuges at a facility in Natanz, Iran. Getty ImagesIn the predawn darkness on Friday local time, Israeli military aircraft struck one of Iran’s uranium-enrichment complexes near the city of Natanz. The warheads aimed to do more than shatter concrete; they were meant to buy time, according to news reports. For months, Iran had seemed to be edging ever closer to “breakout,” the point at which its growing stockpile of partially enriched uranium could be converted into fuel for a nuclear bomb. (Iran has denied that it has been pursuing nuclear weapons development.)But why did the strike occur now? One consideration could involve the way enrichment complexes work. Natural uranium is composed almost entirely of uranium 238, or U-238, an isotope that is relatively “heavy” (meaning it has more neutrons in its nucleus). Only about 0.7 percent is uranium 235 (U-235), a lighter isotope that is capable of sustaining a nuclear chain reaction. That means that in natural uranium, only seven atoms in 1,000 are the lighter, fission-ready U-235; “enrichment” simply means raising the percentage of U-235.U-235 can be used in warheads because its nucleus can easily be split. The International Atomic Energy Agency uses 25 kilograms of contained U-235 as the benchmark amount deemed sufficient for a first-generation implosion bomb. In such a weapon, the U-235 is surrounded by conventional explosives that, when detonated, compress the isotope. A separate device releases a neutron stream. (Neutrons are the neutral subatomic particle in an atom’s nucleus that adds to their mass.) Each time a neutron strikes a U-235 atom, the atom fissions; it divides and spits out, on average, two or three fresh neutrons—plus a burst of energy in the form of heat and gamma radiation. And the emitted neutrons in turn strike other U-235 nuclei, creating a self-sustaining chain reaction among the U-235 atoms that have been packed together into a critical mass. The result is a nuclear explosion. By contrast, the more common isotope, U-238, usually absorbs slow neutrons without splitting and cannot drive such a devastating chain reaction.On supporting science journalismIf you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.To enrich uranium so that it contains enough U-235, the “yellowcake” uranium powder that comes out of a mine must go through a lengthy process of conversions to transform it from a solid into the gas uranium hexafluoride. First, a series of chemical processes refine the uranium and then, at high temperatures, each uranium atom is bound to six fluorine atoms. The result, uranium hexafluoride, is unusual: below 56 degrees Celsius (132.8 degrees Fahrenheit) it is a white, waxy solid, but just above that temperature, it sublimates into a dense, invisible gas.During enrichment, this uranium hexafluoride is loaded into a centrifuge: a metal cylinder that spins at tens of thousands of revolutions per minute—faster than the blades of a jet engine. As the heavier U-238 molecules drift toward the cylinder wall, the lighter U-235 molecules remain closer to the center and are siphoned off. This new, slightly U-235-richer gas is then put into the next centrifuge. The process is repeated 10 to 20 times as ever more enriched gas is sent through a series of centrifuges.Enrichment is a slow process, but the Iranian government has been working on this for years and already holds roughly 400 kilograms of uranium enriched to 60 percent U-235. This falls short of the 90 percent required for nuclear weapons. But whereas Iran’s first-generation IR-1 centrifuges whirl at about 63,000 revolutions per minute and do relatively modest work, its newer IR-6 models, built from high-strength carbon fiber, spin faster and produce enriched uranium far more quickly.Iran has been installing thousands of these units, especially at Fordow, an underground enrichment facility built beneath 80 to 90 meters of rock. According to a report released on Monday by the Institute for Science and International Security, the new centrifuges could produce enough 90 percent U-235 uranium for a warhead “in as little as two to three days” and enough for nine nuclear weapons in three weeks—or 19 by the end of the third month.

Solar air heating is among the most cost-effective applications of solar thermal energy. These systems are used for space heating and preheating fresh air for ventilation, typically using glazed or unglazed perforated solar collectors. The collectors draw in outside air, heat it using solar energy, and then distribute it through ductwork to meet building heating and fresh air needs. In 2024, Canada led again the world for the at least seventh year in a row in solar air heating adoption. The four key suppliers – Trigo Energies, Conserval Engineering, Matrix Energy, and Aéronergie – reported a combined 26,203 m2 (282,046 ft2) of collector area sold last year. Several of these providers are optimistic about the growing demand. These findings come from the newly released Canadian Solar Thermal Market Survey 2024, commissioned by Natural Resources Canada. Canada is the global leader in solar air heating. The market is driven by a strong network of experienced system suppliers, optimized technologies, and a few small favorable funding programs – especially in the province of Quebec. Architects and developers are increasingly turning to these cost-effective, façade-integrated systems as a practical solution for reducing onsite natural gas consumption. Despite its cold climate, Canada benefits from strong solar potential with solar irradiance in many areas rivaling or even exceeding that of parts of Europe. This makes solar air heating not only viable, but especially valuable in buildings with high fresh air requirements including schools, hospitals, and offices. The projects highlighted in this article showcase the versatility and relevance of solar air heating across a range of building types, from new constructions to retrofits. Figure 1: Preheating air for industrial buildings: 2,750 m2 (29,600 ft2) of Calento SL solar air collectors cover all south-west and south-east facing facades of the FAB3R factory in Trois-Rivières, Quebec. The hourly unitary flow rate is set at 41 m3/m2 or 2.23 cfm/ft2 of collector area, at the lower range because only a limited number of intake fans was close enough to the solar façade to avoid long ventilation ductwork. Photo: Trigo Energies Quebec’s solar air heating boom: the Trigo Energies story Trigo Energies makes almost 90 per cent of its sales in Quebec. “We profit from great subsidies, as solar air systems are supported by several organizations in our province – the electricity utility Hydro Quebec, the gas utility Energir and the Ministry of Natural Resources,” explained Christian Vachon, Vice President Technologies and R&D at Trigo Energies. Trigo Energies currently has nine employees directly involved in planning, engineering and installing solar air heating systems and teams up with several partner contractors to install mostly retrofit projects. “A high degree of engineering is required to fit a solar heating system into an existing factory,” emphasized Vachon. “Knowledge about HVAC engineering is as important as experience with solar thermal and architecture.” One recent Trigo installation is at the FAB3R factory in Trois-Rivières. FAB3R specializes in manufacturing, repairing, and refurbishing large industrial equipment. Its air heating and ventilation system needed urgent renovation because of leakages and discomfort for the workers. “Due to many positive references he had from industries in the area, the owner of FAB3R contacted us,” explained Vachon. “The existence of subsidies helped the client to go for a retrofitting project including solar façade at once instead of fixing the problems one bit at a time.” Approximately 50 per cent of the investment costs for both the solar air heating and the renovation of the indoor ventilation system were covered by grants and subsidies. FAB3R profited from an Energir grant targeted at solar preheating, plus an investment subsidy from the Government of Quebec’s EcoPerformance Programme.   Blue or black, but always efficient: the advanced absorber coating In October 2024, the majority of the new 2,750 m² (29,600 ft2) solar façade at FAB3R began operation (see figure 1). According to Vachon, the system is expected to cover approximately 13 per cent of the factory’s annual heating demand, which is otherwise met by natural gas. Trigo Energies equipped the façade with its high-performance Calento SL collectors, featuring a notable innovation: a selective, low-emissivity coating that withstands outdoor conditions. Introduced by Trigo in 2019 and manufactured by Almeco Group from Italy, this advanced coating is engineered to maximize solar absorption while minimizing heat loss via infrared emission, enhancing the overall efficiency of the system. The high efficiency coating is now standard in Trigo’s air heating systems. According to the manufacturer, the improved collector design shows a 25 to 35 per cent increase in yield over the former generation of solar air collectors with black paint. Testing conducted at Queen’s University confirms this performance advantage. Researchers measured the performance of transpired solar air collectors both with and without a selective coating, mounted side-by-side on a south-facing vertical wall. The results showed that the collectors with the selective coating produced 1.3 to 1.5 times more energy than those without it. In 2024, the monitoring results were jointly published by Queen’s University and Canmat Energy in a paper titled Performance Comparison of a Transpired Air Solar Collector with Low-E Surface Coating. Selective coating, also used on other solar thermal technologies including glazed flat plate or vacuum tube collectors, has a distinctive blue color. Trigo customers can, however, choose between blue and black finishes. “By going from the normal blue selective coating to black selective coating, which Almeco is specially producing for Trigo, we lose about 1 per cent in solar efficiency,” explained Vachon. Figure 2: Building-integrated solar air heating façade with MatrixAir collectors at the firehall building in Mont Saint Hilaire, south of Montreal. The 190 m2 (2,045 ft2) south-facing wall preheats the fresh air, reducing natural gas consumption by 18 per cent compared to the conventional make-up system. Architect: Leclerc Architecture. Photo: Matrix Energy Matrix Energy: collaborating with architects and engineers in new builds The key target customer group of Matrix Energy are public buildings – mainly new construction. “Since the pandemic, schools are more conscious about fresh air, and solar preheating of the incoming fresh air has a positive impact over the entire school year,” noted Brian Wilkinson, President of Matrix Energy. Matrix Energy supplies systems across Canada, working with local partners to source and process the metal sheets used in their MatrixAir collectors. These metal sheets are perforated and then formed into architectural cladding profiles. The company exclusively offers unglazed, single-stage collectors, citing fire safety concerns associated with polymeric covers. “We have strong relationships with many architects and engineers who appreciate the simplicity and cost-effectiveness of transpired solar air heating systems,” said President Brian Wilkinson, describing the company’s sales approach. “Matrix handles system design and supplies the necessary materials, while installation is carried out by specialized cladding and HVAC contractors overseen by on-site architects and engineers,” Wilkinson added. Finding the right flow: the importance of unitary airflow rates One of the key design factors in solar air heating systems is the amount of air that passes through each square meter of the perforated metal absorber,  known as the unitary airflow rate. The principle is straightforward: higher airflow rates deliver more total heat to the building, while lower flow rates result in higher outlet air temperatures. Striking the right balance between air volume and temperature gain is essential for efficient system performance. For unglazed collectors mounted on building façades, typical hourly flow rates should range between 120 and 170 (m3/h/m2), or 6.6 to 9.4 cfm/ft2. However, Wilkinson suggests that an hourly airflow rate of around 130 m³/h/m² (7.2 cfm/ft2) offers the best cost-benefit balance for building owners. If the airflow is lower, the system will deliver higher air temperatures, but it would then need a much larger collector area to achieve the same air volume and optimum performance, he explained. It’s also crucial for the flow rate to overcome external wind pressure. As wind passes over the absorber, air flow through the collector’s perforations is reduced, resulting in heat losses to the environment. This effect becomes even more pronounced in taller buildings, where wind exposure is greater. To ensure the system performs well even in these conditions, higher hourly airflow rates typically between 150 and 170 m³/m² (8.3 to 9.4 cfm/ft2)  are necessary. Figure 3: One of three apartment blocks of the Maple House in Toronto’s Canary District. Around 160 m2 (1,722 ft2) of SolarWall collectors clad the two-storey mechanical penthouse on the roof. The rental flats have been occupied since the beginning of 2024. Collaborators: architects-Alliance, Claude Cormier et Associés, Thornton Tomasetti, RWDI, Cole Engineering, DesignAgency, MVShore, BA Group, EllisDon. Photo: Conserval Engineering Solar air heating systems support LEED-certified building designs Solar air collectors are also well-suited for use in multi-unit residential buildings. A prime example is the Canary District in Toronto (see Figure 3), where single-stage SolarWall collectors from Conserval Engineering have been installed on several MURBs to clad the mechanical penthouses. “These penthouses are an ideal location for our air heating collectors, as they contain the make-up air units that supply corridor ventilation throughout the building,” explained Victoria Hollick, Vice President of Conserval Engineering. “The walls are typically finished with metal façades, which can be seamlessly replaced with a SolarWall system – maintaining the architectural language without disruption.” To date, nine solar air heating systems have been commissioned in the Canary District, covering a total collector area of over 1,000 m² (10,764 ft2). “Our customers have many motivations to integrate SolarWall technology into their new construction or retrofit projects, either carbon reduction, ESG, or green building certification targets,” explained Hollick. The use of solar air collectors in the Canary District was proposed by architects from the Danish firm Cobe. The black-colored SolarWall system preheats incoming air before it is distributed to the building’s corridors and common areas, reducing reliance on natural gas heating and supporting the pursuit of LEED Gold certification. Hollick estimates the amount of gas saved between 10 to 20 per cent of the total heating load for the corridor ventilation of the multi-unit residential buildings. Additional energy-saving strategies include a 50/50 window-to-wall ratio with high-performance glazing, green roofs, high-efficiency mechanical systems, LED lighting, and Energy Star-certified appliances. The ideal orientation for a SolarWall system is due south. However, the systems can be built at any orientation up to 90° east and west, explained Hollick. A SolarWall at 90° would have approximately 60 per cent of the energy production of the same area facing south.Canada’s expertise in solar air heating continues to set a global benchmark, driven by supporting R&D, by innovative technologies, strategic partnerships, and a growing portfolio of high-impact projects. With strong policy support and proven performance, solar air heating is poised to play a key role in the country’s energy-efficient building future. Figure 4: Claude-Bechard Building in Quebec is a showcase project for sustainable architecture with a 72 m2 (775 ft2) Lubi solar air heating wall from Aéronergie. It serves as a regional administrative center. Architectural firm: Goulet et Lebel Architectes. Photo: Art Massif Bärbel Epp is the general manager of the German Agency solrico, whose focus is on solar market research and international communication. The post Op-ed: Canada’s leadership in solar air heating—Innovation and flagship projects appeared first on Canadian Architect.

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