Southern University of Science & Technology

Engineers have designed a system that can efficiently produce 'solar thermochemical hydrogen.' It harnesses the sun's heat to split water and generate hydrogen -- a clean fuel that emits no greenhouse gas emissions.  MIT engineers aim to produce totally green, carbon-free hydrogen fuel with a new, train-like system of reactors that is driven solely by the sun. In a study appearing today in Solar Energy Journal, the engineers lay out the conceptual design for a system that can efficiently produce "solar thermochemical hydrogen." The system harnesses the sun's heat to directly split water and generate hydrogen -- a clean fuel that can power long-distance trucks, ships, and planes, while in the process emitting no greenhouse gas emissions. Today, hydrogen is largely produced through processes that involve natural gas and other fossil fuels, making the otherwise green fuel more of a "grey" energy source when considered from the start of its production to its end use. In contrast, solar thermochemical hydrogen, or STCH, offers a totally emissions-free alternative, as it relies entirely on renewable solar energy to drive hydrogen production. But so far, existing STCH designs have limited efficiency: Only about 7 percent of incoming sunlight is used to make hydrogen. The results so far have been low-yield and high-cost. In a big step toward realizing solar-made fuels, the MIT team estimates its new design could harness up to 40 percent of the sun's heat to generate that much more hydrogen. The increase in efficiency could drive down the system's overall cost, making STCH a potentially scalable, affordable option to help decarbonize the transportation industry. "We're thinking of hydrogen as the fuel of the future, and there's a need to generate it cheaply and at scale," says the study's lead author, Ahmed Ghoniem, the Ronald C. Crane Professor of Mechanical Engineering at MIT. "We're trying to achieve the Department of Energy's goal, which is to make green hydrogen by 2030, at $1 per kilogram. To improve the economics, we have to improve the efficiency and make sure most of the solar energy we collect is used in the production of hydrogen." Ghoniem's study co-authors are Aniket Patankar, first author and MIT postdoc; Harry Tuller, MIT professor of materials science and engineering; Xiao-Yu Wu of the University of Waterloo; and Wonjae Choi at Ewha Womans University in South Korea. Solar stations Similar to other proposed designs, the MIT system would be paired with an existing source of solar heat, such as a concentrated solar plant (CSP) -- a circular array of hundreds of mirrors that collect and reflect sunlight to a central receiving tower. An STCH system then absorbs the receiver's heat and directs it to split water and produce hydrogen. This process is very different from electrolysis, which uses electricity instead of heat to split water. At the heart of a conceptual STCH system is a two-step thermochemical reaction. In the first step, water in the form of steam is exposed to a metal. This causes the metal to grab oxygen from steam, leaving hydrogen behind. This metal "oxidation" is similar to the rusting of iron in the presence of water, but it occurs much faster. Once hydrogen is separated, the oxidized (or rusted) metal is reheated in a vacuum, which acts to reverse the rusting process and regenerate the metal. With the oxygen removed, the metal can be cooled and exposed to steam again to produce more hydrogen. This process can be repeated hundreds of times. The MIT system is designed to optimize this process. The system as a whole resembles a train of box-shaped reactors running on a circular track. In practice, this track would be set around a solar thermal source, such as a CSP tower. Each reactor in the train would house the metal that undergoes the redox, or reversible rusting, process. Each reactor would first pass through a hot station, where it would be exposed to the sun's heat at temperatures of up to 1,500 degrees Celsius. This extreme heat would effectively pull oxygen out of a reactor's metal. That metal would then be in a "reduced" state -- ready to grab oxygen from steam. For this to happen, the reactor would move to a cooler station at temperatures around 1,000 C, where it would be exposed to steam to produce hydrogen. Rust and rails Other similar STCH concepts have run up against a common obstacle: what to do with the heat released by the reduced reactor as it is cooled. Without recovering and reusing this heat, the system's efficiency is too low to be practical. A second challenge has to do with creating an energy-efficient vacuum where metal can de-rust. Some prototypes generate a vacuum using mechanical pumps, though the pumps are too energy-intensive and costly for large-scale hydrogen production. To address these challenges, the MIT design incorporates several energy-saving workarounds. To recover most of the heat that would otherwise escape from the system, reactors on opposite sides of the circular track are allowed to exchange heat through thermal radiation; hot reactors get cooled while cool reactors get heated. This keeps the heat within the system. The researchers also added a second set of reactors that would circle around the first train, moving in the opposite direction. This outer train of reactors would operate at generally cooler temperatures and would be used to evacuate oxygen from the hotter inner train, without the need for energy-consuming mechanical pumps. These outer reactors would carry a second type of metal that can also easily oxidize. As they circle around, the outer reactors would absorb oxygen from the inner reactors, effectively de-rusting the original metal, without having to use energy-intensive vacuum pumps. Both reactor trains would run continuously and would enerate separate streams of pure hydrogen and oxygen. The researchers carried out detailed simulations of the conceptual design, and found that it would significantly boost the efficiency of solar thermochemical hydrogen production, from 7 percent, as previous designs have demonstrated, to 40 percent. "We have to think of every bit of energy in the system, and how to use it, to minimize the cost," Ghoniem says. "And with this design, we found that everything can be powered by heat coming from the sun. It is able to use 40 percent of the sun's heat to produce hydrogen." In the next year, the team will be building a prototype of the system that they plan to test in concentrated solar power facilities at laboratories of the Department of Energy, which is currently funding the project. "When fully implemented, this system would be housed in a little building in the middle of a solar field," Patankar explains. "Inside the building, there could be one or more trains each having about 50 reactors. And we think this could be a modular system, where you can add reactors to a conveyor belt, to scale up hydrogen production." This work was supported by the Centers for Mechanical Engineering Research and Education at MIT and SUSTech.

Exploding populations of wild pigs and macaque monkeys in Southeast Asia are threatening native forests and disease outbreaks in livestock and people, according to new research. Exploding populations of wild pigs and macaque monkeys in Southeast Asia are threatening native forests and disease outbreaks in livestock and people, according to research led by The University of Queensland. Dr Matthew Luskin, from UQ's School of the Environment, and his team collated and analysed species population data from across the region, some of it collected with a network of cameras. "Macaques and wild pigs are taking over Southeast Asia's disturbed forests," Dr Luskin said. "Humans are largely to blame for this by altering forests with logging and establishing palm oil farms which provide food and ideal breeding conditions for these animals. "We saw that wild boar and macaque numbers were 400 per cent higher in forests near the plantations than in untouched environments. "These animals take full advantage of the farmland, raiding crops and thriving on calorie-rich foods." Setting and monitoring the camera traps provided Dr Luskin with an up-close experience of the exploding numbers. "I encountered huge troops of macaques in Thailand, Malaysia, and Indonesia -- they were everywhere in the forest edges, following us and interfering with our equipment," Dr Luskin said. "At first it was frustrating but then was eerie as we became completely surrounded." Dr Luskin said there were significant human health risks in the rising pig and macaque populations. "The wildlife origins of the COVID-19 pandemic show that mammals in human-modified ecosystems often host high pathogen loads and pose serious zoonotic disease risks," he said. "Both pigs and macaques are recognised as carriers of diseases that can be transmitted to people and they're the most common species in a region considered to be the global zoonotic disease hotspot." Collaborator, Professor Carlos Peres from the University of East Anglia (UK), said abnormally high populations of wildlife species that are disease reservoirs often occur in human-modified tropical forests. "This study again shows that densely settled rural areas in Southeast Asia may be a source of future human epidemics," he said. University of East Anglia and Southern University of Science and Technology (China) PhD candidate, Jonathan Moore, said the immediate effects of the population explosions could be seen on native flora in the affected regions. "Both pigs and macaques trigger negative cascading impacts in these pristine ecosystems," Mr Moore said. "They kill the seeds and seedlings of native plants and eat bird and reptile eggs. "The Malaysian pigs alone were found to reduce rainforest tree regeneration by 62 per cent." The researchers say action is needed to minimise population expansions of wild pigs and macaques. "Efforts to manage the populations of these species have failed in the past because of their rapid reproductive capacity and public outcry," Dr Luskin said. "Nobody favours needless killing of wildlife but the negative social and ecological impacts from hyperabundant pest species does demand ethical and urgent management solutions."

Researchers have developed a 'heart attack on a chip,' a device that could one day serve as a test-bed to develop new heart drugs and even personalized medicines. Researchers at the University of Southern California Alfred E. Mann Department of Biomedical Engineering have developed a "heart attack on a chip," a device that could one day serve as a testbed to develop new heart drugs and even personalized medicines. "Our device replicates some key features of a heart attack in a relatively simple and easy to use system," said Megan McCain, an associate professor of biomedical engineering and stem cell biology and regenerative medicine, who developed the device with postdoctoral researcher Megan Rexius-Hall. "This enables us to more clearly understand how the heart is changing after a heart attack. From there, we and others can develop and test drugs that will be most effective for limiting the further degradation of heart tissue that can occur after a heart attack," added McCain. McCain, a "cardiac tissue engineer," whose work previously included co-developing a heart on a chip, and Rexius-Hall detail their findings in a recently released article in the journal Science Advances titled "A Myocardial Infarct Border-Zone-On-A-Chip Demonstrates Distinct Regulation of Cardiac Tissue Function by an Oxygen Gradient." America's No. 1 killer Coronary heart disease is America's No. 1 killer. In 2018, 360,900 Americans succumbed to it, making heart disease responsible for 12.6% of all deaths in the United States, according to the AHA. Severe coronary heart disease can cause a heart attack, which accounts for much of that pain and suffering. Heart attacks occur when fat, cholesterol and other substances in the coronary arteries severely reduce the flow of oxygen-rich blood to part of the heart. Between 2005 and 2014, an average of 805,000 Americans per year had heart attacks. Even if a patient survives a heart attack, over time they can become increasingly fatigued, enervated and sick; some even die due to heart failure. That's because heart cells don't regenerate like other muscle cells. Instead, immune cells appear at the site of injury, some of which can be harmful. Additionally, scarring develops that weakens the heart and the amount of blood it can pump. However, scientists don't completely understand this process, especially how heart cells in the healthy and injured parts of the heart communicate with each other and how and why they change after a heart attack. McCain and Rexius-Hall believe their heart attack on a chip can shed some light on those mysteries. "Fundamentally, we want to have a model that can lead to a better understanding of heart attack injury," Rexius-Hall said. Heart Attack On a Chip The heart attack on a chip is literally built from the ground up. At the base is a 22-millimeter-by-22-millimeter square microfluidic device slightly larger than a quarter -- made from a rubber-like polymer called PDMS -- with two channels on opposing sides through which gases flow. Above that sits a very thin layer of the same rubber material, which is permeable to oxygen. A micro layer of protein is then patterned on the top of the chip, "so that the heart cells align and form the same architecture that we have in our hearts," McCain said. Finally, rodent heart cells are grown atop the protein. To mimic a heart attack, gas with oxygen and gas without oxygen is released through each channel of the microfluidic device, "exposing our heart on a chip to an oxygen gradient, similar to what really happens in a heart attack," McCain said. Because the microfluidic device is small, clear, and easy to see on a microscope, McCain added, it also allows researchers to observe in real time functional changes that sometimes happen in the heart after an attack, including an arrythmia, or an irregular heartbeat, and contractile dysfunction, or decreases in the contraction strength of the heart. In the future, researchers can make the model more complex by adding immune cells or fibroblasts, the cells that generate the scar after a heart attack. By contrast, researchers cannot watch changes to heart tissue in real time with animal models. Additionally, traditional cell culture models uniformly expose heart cells to high, medium or low levels of oxygen, but not a gradient. That means they cannot mimic what really happens to damaged heart cells in the so-called border zone after a heart attack, Rexius-Hall said. Added McCain: It is very exciting and rewarding to envision our device having a positive impact on patient lives in the near future, especially for heart attacks, which are extremely prevalent." Other co-authors on this paper include Natalie Khalil, a USC Viterbi Ph.D. student in biomedical engineering; Sean Escopete and Sarah Parker of the Smidt Heart Institute at Cedars-Sinai Medical Center; and Xin Li, Jiayi Hu, Hongyan Yuan of the Department of Mechanics and Aerospace Engineering at Southern University of Science and Technology in China. The National Heart, Lung, and Blood Institute and the American Heart Association (AHA) supported this research.