Protecting the nation from threats at home and abroad requires an assured supply of clean drinking water – and lots of it.
Together with researchers from Washington University in St. Louis, HDIAC Subject Matter Expert Joel Hewett discusses new technologies in development that can help assure an uninterrupted supply of drinking water for those who need it most.
“With possible applications in catalysis, chemical separations, biosensing, and drug delivery, MSNs (mesoporous silica nanoparticles) are the focus of intense scientific research.”
Advanced nuclear magnetic resonance (NMR) techniques at the U.S. Department of Energy’s Ames Laboratory have revealed surprising details about the structure of a key group of materials in nanotechology, mesoporous silica nanoparticles (MSNs), and the placement of their active chemical sites.
MSNs are honeycombed with tiny (about 2-15 nm wide) three-dimensionally ordered tunnels or pores, and serve as supports for organic functional groups tailored to a wide range of needs. With possible applications in catalysis, chemical separations, biosensing, and drug delivery, MSNs are the focus of intense scientific research.
“Since the development of MSNs, people have been trying to control the way they function,” said Takeshi Kobayashi, an NMR scientist with the Division of Chemical and Biological Sciences at Ames Laboratory.
“Research has explored doing this through modifying particle size and shape, pore size, and by deploying various organic functional groups on their surfaces to accomplish the desired chemical tasks. However, understanding of the results of these synthetic efforts can be very challenging.”
Ames Laboratory scientist Marek Pruski explained that despite the existence of different techniques for MSNs’ functionalization, no one knew exactlyhowthey were different. In particular, atomic-scale description of how the organic groups were distributed on the surface was lacking until recently.
“It is one thing to detect and quantify these functional groups, or even determine their structure,” said Pruski. “But elucidating their spatial arrangement poses additional challenges.
Do they reside on the surfaces or are they partly embedded in the silica walls? Are they uniformly distributed on surfaces? If there are multiple types of functionalities, are they randomly mixed or do they form domains?
Conventional NMR, as well as other analytical techniques, have struggled to provide satisfactory answers to these important questions.”
Kobayashi, Pruski, and other researchers used DNP-NMR to obtain a much clearer picture of the structures of functionalized MSNs. “DNP” stands for “dynamic nuclear polarization,” a method which uses microwaves to excite unpaired electrons in radicals and transfer their high spin polarization to the nuclei in the sample being analyzed, offering drastically higher sensitivity, often by two orders of magnitude, and even larger savings of experimental time.
Conventional NMR, which measures the responses of the nuclei of atoms placed in a magnetic field to direct radio-frequency excitation, lacks the sensitivity needed to identify the internuclear interactions between different sites and functionalities on surfaces.
When paired with DNP, as well as fast magic angle spinning (MAS), NMR can be used to detect such interactions with unprecedented sensitivity.
Not only did the DNP-NMR methods elicit the atomic-scale location and distribution of the functional groups, but the results disproved some of the existing notions of how MSNs are made and how the different synthetic strategies influenced the dispersion of functional groups throughout the silica pores.
“By examining the role of various experimental conditions, our NMR techniques can give scientists the mechanistic insight they need to guide the synthesis of MSNs in a more controlled way,” said Kobayashi.
Ames Laboratory is a U.S. Department of EnergyOffice of Science national laboratory operated by Iowa State University. Ames Laboratory creates innovative materials, technologies and energy solutions. We use our expertise, unique capabilities and interdisciplinary collaborations to solve global problems.
The U.S. Department of Energy’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit https://energy.gov/science.
UC Berkeley and Berkeley Lab researchers created a new crystal built of a spiraling stack of atomically thin
UC Berkeley and Berkeley Lab researchers created a new crystal built of a spiraling stack of atomically thin germanium sulfide sheets. Credit: UC Berkeley image by Yin Liu
With a simple twist of the fingers, one can create a beautiful spiral from a deck of cards. In the same way, scientists at the University of California, Berkeley, and Lawrence Berkeley National Laboratory (Berkeley Lab) have created new inorganic crystals made of stacks of atomically thin sheets that unexpectedly spiral like a nanoscale card deck.
Their surprising structures, reported in a new study appearing online Wednesday, June 20, in the journal Nature, may yield unique optical, electronic and thermal properties, including superconductivity, the researchers say.
These helical crystals are made of stacked layers of germanium sulfide, a semiconductor material that, like graphene, readily forms sheets that are only a few atoms or even a single atom thick. Such “nanosheets” are usually referred to as “2-D materials.”
“No one expected 2-D materials to grow in such a way. It’s like a surprise gift,” said Jie Yao, an assistant professor of materials science and engineering at UC Berkeley. “We believe that it may bring great opportunities for materials research.”
While the shape of the crystals may resemble that of DNA, whose helical structure is critical to its job of carrying genetic information, their underlying structure is actually quite different. Unlike “organic” DNA, which is primarily built of familiar atoms like carbon, oxygen and hydrogen, these “inorganic” crystals are built of more far-flung elements of the periodic table—in this case, sulfur and germanium. And while organic molecules often take all sorts of zany shapes, due to unique properties of their primary component, carbon, inorganic molecules tend more toward the straight and narrow.
To create the twisted structures, the team took advantage of a crystal defect called a screw dislocation, a “mistake” in the orderly crystal structure that gives it a bit of a twisting force. This “Eshelby Twist,” named after scientist John D. Eshelby, has been used to create nanowires that spiral like pine trees. But this study is the first time the Eshelby Twist has been used to make crystals built of stacked 2-D layers of an atomically thin semiconductor.
The helical crystals may yield surprising new properties, like superconductivity. Credit: UC Berkeley image by Yin Liu
“Usually, people hate defects in a material—they want to have a perfect crystal,” said Yao, who also serves as a faculty scientist at Berkeley Lab. “But it turns out that, this time, we have to thank the defects. They allowed us to create a natural twist between the material layers.”
In a major discovery last year, scientists reported that graphene becomes superconductive when two atomically thin sheets of the material are stacked and twisted at what’s called a “magic angle.” While other researchers have succeeded at stacking two layers at a time, the new paper provides a recipe for synthesizing stacked structures that are hundreds of thousands or even millions of layers thick in a continuously twisting fashion.
“We observed the formation of discrete steps in the twisted crystal, which transforms the smoothly twisted crystal to circular staircases, a new phenomenon associated with the Eshelby Twist mechanism,” said Yin Liu, co-first author of the paper and a graduate student in materials science and engineering at UC Berkeley. “It’s quite amazing how interplay of materials could result in many different, beautiful geometries.”
By adjusting the material synthesis conditions and length, the researchers could change the angle between the layers, creating a twisted structure that is tight, like a spring, or loose, like an uncoiled Slinky. And while the research team demonstrated the technique by growing helical crystals of germanium sulfide, it could likely be used to grow layers of other materials that form similar atomically thin layers.
“The twisted structure arises from a competition between stored energy and the energy cost of slipping two material layers relative to one another,” said Daryl Chrzan, chair of the Department of Materials Science and Engineering and senior theorist on the paper. “There is no reason to expect that this competition is limited to germanium sulfide, and similar structures should be possible in other 2-D material systems.”
“The twisted behavior of these layered materials, typically with only two layers twisted at different angles, has already showed great potential and attracted a lot of attention from the physics and chemistry communities. Now, it becomes highly intriguing to find out, with all of these twisted layers combined in our new material, if will they show quite different material properties than regular stacking of these materials,” Yao said. “But at this moment, we have very limited understanding of what these properties could be, because this form of material is so new. New opportunities are waiting for us.”
Researchers have created an ink made of graphene nanosheets, and demonstrated that the ink can be used to print 3-D structures. As the graphene-based ink can be mass-produced in an inexpensive and environmentally friendly manner, the new methods pave the way toward developing a wide variety of printable energy storage devices.
The researchers, led by Jingyu Sun and Zhongfan Liu at Soochow University and the Beijing Graphene Institute, and Ya-yun Li at Shenzhen University, have published a paper on their work in a recent issue ofACS Nano.
“Our work realizes the scalable and green synthesis of nitrogen-dopedgraphenenanosheets on a salt template by direct chemical vapor deposition,” Sun toldPhys.org. “This allows us to further explore thus-derived inks in the field of printable energy storage.”
As the scientists explain, a key goal in graphene research is the mass production of graphene with high quality and at low cost. Energy-storage applications typically require graphene in powder form, but so far production methods have resulted in powders with a large number of structural defects and chemical impurities, as well as nonuniform layer thickness. This has made it difficult to prepare high-quality graphene inks.
In the new paper, the researchers have demonstrated a new method for preparing graphene inks that overcomes these challenges. The method involves growing nitrogen-doped graphene nanosheets over NaCl crystals using direct chemical vapor deposition, which causes molecular fragments of nitrogen and carbon to diffuse on the surface of the NaCl crystals. The researchers chose NaCl due to its natural abundance and low cost, as well as its water solubility.
To remove the NaCl, the coated crystals are submerged in water, which causes the NaCl to dissolve and leave behind pure nitrogen-doped graphene cages. In the final step, treating the cages with ultrasound transforms the cages into 2-D nanosheets, each about 5-7 graphite layers thick.
The resulting nitrogen-doped graphene nanosheets have relatively few defects and an ideal size (about 5 micrometers in side length) for printing, as larger flakes can block the nozzle.
To demonstrate the nanosheets’ effectiveness, the researchers printed a wide variety of 3-D structures using inks based on the graphene sheets.
Among their demonstrations, the researchers used the ink as a conductive additive for anelectrode material(vanadium nitride) and used the composite ink to print flexible electrodes for supercapacitors with high power density and good cyclic stability.
In a second demonstration, the researchers created a composite ink made of the graphene sheets along with binder material (polypropylene) for printing interlayers for Li−S batteries.
Compared to batteries with separators made only of the conventional material, those made with the composite material exhibited enhanced conductivity, leading to an overall improvement in battery performance.
“In the future, we plan to exploit the directchemical vapor depositiontechnique for the mass production of high-quality graphene powders toward emerging printable energy storage applications,” Sun said.
More information:Nan Wei et al. “Scalable Salt-Templated Synthesis of Nitrogen-Doped Graphene Nanosheets toward Printable Energy Storage.”ACS Nano. DOI:10.1021/acsnano.9b03157
A protective layer of epoxy resin helps prevent the leakage of pollutants from perovskite solar cells (PSCs), according to scientists from the Okinawa Institute of Science and Technology Graduate University (OIST). Adding a “self-healing” polymer to the top of a PSC can radically reduce how much lead it discharges into the environment. This gives a strong boost to prospects for commercializing the technology.
With atmospheric carbon dioxide levels reaching their highest recorded levels in history, and extreme weather events continuing to rise in number, the world is moving away from legacy energy systems relying on fossil fuels towards renewables such as solar. Perovskite solar technology is promising, but one key challenge to commercialization is that it may release pollutants such as lead into the environment—especially under extreme weather conditions.
“Although PSCs are efficient at converting sunlight into electricity at an affordable cost, the fact that they contain lead raises considerable environmental concern,” explains Professor Yabing Qi, head of the Energy Materials and Surface Sciences Unit, who led the study, published in Nature Energy.
“While so-called ‘lead-free’ technology is worth exploring, it has not yet achieved efficiency and stability comparable to lead-based approaches. Finding ways of using lead in PSCs while keeping it from leaking into the environment, therefore, is a crucial step for commercialization.”
Testing to destruction
Qi’s team, supported by the OIST Technology Development and Innovation Center’s Proof-of-Concept Program, first explored encapsulation methods for adding protective layers to PSCs to understand which materials might best prevent the leakage of lead. They exposed cells encapsulated with different materials to many conditions designed to simulate the sorts of weather to which the cells would be exposed in reality.
They wanted to test the solar cells in a worst-case weather scenario, to understand the maximum lead leakage that could occur. First, they smashed the solar cells using a large ball, mimicking extreme hail that could break down their structure and allow lead to be leaked. Next, they doused the cells with acidic water, to simulate the rainwater that would transport leaked lead into the environment.
Using mass spectroscopy, the team analyzed the acidic rain to determine how much lead leaked from the cells. They found that an epoxy resin layer allowed only minimal lead leakage—orders of magnitude lower than the other materials.
Enabling commercial viability
Epoxy resin also performed best under a number of weather conditions in which sunlight, rainwater and temperature were altered to simulate the environments in which PSCs must operate. In all scenarios, including extreme rain, epoxy resin outperformed rival encapsulation materials.
Epoxy resin works so well due to its “self-healing” properties. After its structure is damaged by hail, for example, the polymer partially reforms its original shape when heated by sunlight. This limits the amount of lead that leaks from inside the cell. This self-healing property could make epoxy resin the encapsulation layer of choice for future photovoltaic products.
“Epoxy resin is certainly a strong candidate, yet other self-healing polymers may be even better,” explains Qi. “At this stage, we are pleased to be promoting photovoltaic industry standards, and bringing the safety of this technology into the discussion. Next, we can build on these data to confirm which is truly the best polymer.”
Beyond lead leakage, another challenge will be to scale up perovskite solar cells into perovskite solar panels. While cells are just a few centimeters long, panels can span a few meters, and will be more relevant to potential consumers. The team will also direct their attention to the long-standing challenge of renewable energy storage.
The World Health Organization (WHO) estimates that by 2025, about half of the world’s population will live in areas where there is a shortage of clean drinking water. Is it possible that the solution to the global water crisis is, literally, right under our noses? Technion researchers have developed a model for a system that separates the moisture naturally present in the air around us and converts it into drinking water. The patented system, and how it can help prevent the water crisis that awaits the world, was recently presented by Associate Professor David Broday of Technion’s Faculty of Civil and Environmental Engineering at a seminar on water, energy, treatment, and recycling.
“Water is available and free to everyone”
Associate Professor Broday, who developed the system together with his colleague Associate Professor Eran Friedler, explains that the idea is to take advantage of a resource that is constantly and abundantly present around us.
“The atmosphere is everywhere, and there is humidity everywhere,” says Broday. “No atmosphere is completely dry; there is humidity even in the air of the arid Sahara Desert. In fact, the amount of moisture in the atmosphere is equal to the amount of fresh liquid water in the world (i.e. not accounting for glaciers). This is a huge amount of water freely available to everyone with no restrictions.”
Harvesting moisture from the air is not new, and there are several companies around the world that have already developed technologies around this concept. This existing technology, says Broday, is similar to a domestic air conditioner that cools air that comes from the outdoors, uses the cold air, and discards the water condensed during the cooling process. In the case of moisture harvesting technology, it is the air that is discarded and the water that is used. “The existing technology actually takes air and cools it to extract the moisture from it,” explains Broday. “It is brought to a state where the moisture condenses on a cold surface and drips from it, then it is collected and used for drinking.”
But, says Prof. Broday, there is a problem with this technology. “Air is composed not only of moisture but also of other gases like oxygen and nitrogen, and this technology invests in cooling them along with the humidity,” he explains. “Air volume contains only 4 to 5 percent humidity, at best, which is a very small part. A lot of energy is invested in cooling something of which more than 90 percent doesn’t get used at all. This is an ineffective use of energy. This process is expensive to begin with, and in effect most of the energy goes towards cooling material that we are not at all interested in.”
With their system, the researchers propose to optimize this process by separating moisture from the air before cooling it. Doing so will make it possible to invest energy in cooling only the moisture itself and converting it into available water.
The Technion system is also a radical departure from attempts by others who are trying to develop membranes that will separate the moisture out of the air (like the desalination process in which membranes separate salt from seawater).
“The alternative we are proposing is based on the use of an absorbent substance called a desiccant, which is a highly concentrated saline solution that naturally absorbs the moisture from the air when it comes into contact with it,” Broday explains. “The idea is to use this material to absorb a large amount of moisture from the air, and to cool the moisture only after this has been accomplished.”
“Our system is composed of several stages,” he explains. “In the first stage, it will circulate air to transfer moisture from the air to the dessicant, which is in a liquid state. This cycle is repeated over and over again, as the dessicant collects more and more moisture from the air. In the second stage, we transfer a small portion of the dessicant to another part of the system, where we produce conditions that cause the desiccant to release the moisture. This moisture is then condensed and turned into water. For this to happen, we need to cool it down – this is the third stage, which is actually similar to what happens in existing systems; but unlike them, at this stage we cool 100 percent humidity rather than air, only a fraction of which is relevant to our needs.”
Drinkable water in the middle of the desert
According to the researchers, their proposed system isn’t just more energy-efficient. It also provides cleaner water. After cooling, the water collected in the system should be suitable for immediate drinking, as opposed to existing technologies in which air is cooled in its entirety. “If the air spinning in a system – in addition to moisture – contains disease-causing bacteria, when it is cooled and the water condenses, the bacteria in the air may also find their way into the water,” Broday explains. “This means this water may require purification to make it fit for consumption.
“In our system, the air does not meet the cooling coils at all – only the moisture that is separated from it. As a result, even if the air contains substances we do not want to reach the water, they are absorbed into the dessicant but not released in the next stage,” he says. “Even if bacteria, dust, and the like have accumulated, because it is a very concentrated salt solution, it simply dries up. So the resulting moisture would be clean, and the water, pure. Of course they would be tested, but the need for water treatment processes would probably be much smaller, which is expected to lower the price of using it.”
Using the system would not be without cost, and the researchers emphasize that their method of producing water is more expensive than desalination.
“Where water can be desalinated – that is, in proximity to a source of water such as a sea or brackish lakes – desalination is the preferred option,” explains Broday. “Economically speaking, it makes sense to desalinate and produce a system for transporting water to places that are up to about 62 miles away. Any further than this, and the cost of transportation becomes more expensive than the cost of desalination. There are also towns located close to rivers where water is suitable for use. But when we take all of these out of the equation, there are quite a few places in the world where desalination and direct use are not economically viable.”
The Technion researchers’ system has not yet been built, but they have already performed simulations with a model to see how the system would function in different climatic and humidity conditions. “We wanted to see whether the system can be used in areas where the air is arid,” says Broday, “for example in the Sahara Desert, and in Yemen, which is currently experiencing a severe hunger crisis and lack of drinking water.” He says the system is both relatively small and allows for distributed production of water that does not depend on one source from which the water must be piped to all the other localities.
“We strongly believe in the idea and the preliminary results,” says Broday. “But we still have to put the theory into practice. That’s the next stage.”
The Technion-Israel Institute of Technology is a major source of the innovation and brainpower that drives the Israeli economy, and a key to Israel’s renown as the world’s “Start-Up Nation.” Its three Nobel Prize winners exemplify academic excellence. Technion people, ideas and inventions make immeasurable contributions to the world including life-saving medicine, sustainable energy, computer science, water conservation and nanotechnology.
American Technion Society (ATS) donors provide critical support for the Technion—nearly $2.5 billion since its inception in 1940. Based in New York City, the ATS and its network of supporters across the U.S. provide funds for scholarships, fellowships, faculty recruitment and chairs, research, buildings, laboratories, classrooms and dormitories, and more.
Rice University’s solar-powered approach for purifying salt water with sunlight and nanoparticles is even more efficient than its creators first believed.
Researchers in Rice’s Laboratory for Nanophotonics (LANP) this week showed they could boost the efficiency of their solar-powered desalination system by more than 50% simply by adding inexpensive plastic lenses to concentrate sunlight into “hot spots.” The results are available online in the Proceedings of the National Academy of Sciences.
“The typical way to boost performance in solar-driven systems is to add solar concentrators and bring in more light,” said Pratiksha Dongare, a graduate student in applied physics at Rice’s Brown School of Engineering and co-lead author of the paper. “The big difference here is that we’re using the same amount of light. We’ve shown it’s possible to inexpensively redistribute that power and dramatically increase the rate of purified water production.”
In conventional membrane distillation, hot, salty water is flowed across one side of a sheetlike membrane while cool, filtered water flows across the other. The temperature difference creates a difference in vapor pressure that drives water vapor from the heated side through the membrane toward the cooler, lower-pressure side. Scaling up the technology is difficult because the temperature difference across the membrane—and the resulting output of clean water—decreases as the size of the membrane increases. Rice’s “nanophotonics-enabled solar membrane distillation” (NESMD) technology addresses this by using light-absorbing nanoparticles to turn the membrane itself into a solar-driven heating element.
Dongare and colleagues, including study co-lead author Alessandro Alabastri, coat the top layer of their membranes with low-cost, commercially available nanoparticles that are designed to convert more than 80% of sunlight energy into heat. The solar-driven nanoparticle heating reduces production costs, and Rice engineers are working to scale up the technology for applications in remote areas that have no access to electricity.
The concept and particles used in NESMD were first demonstrated in 2012 by LANP director Naomi Halas and research scientist Oara Neumann, who are both co-authors on the new study. In this week’s study, Halas, Dongare, Alabastri, Neumann and LANP physicist Peter Nordlander found they could exploit an inherent and previously unrecognized nonlinear relationship between incident light intensity and vapor pressure.
Alabastri, a physicist and Texas Instruments Research Assistant Professor in Rice’s Department of Electrical and Computer Engineering, used a simple mathematical example to describe the difference between a linear and nonlinear relationship. “If you take any two numbers that equal 10—seven and three, five and five, six and four—you will always get 10 if you add them together. But if the process is nonlinear, you might square them or even cube them before adding. So if we have nine and one, that would be nine squared, or 81, plus one squared, which equals 82. That is far better than 10, which is the best you can do with a linear relationship.”
In the case of NESMD, the nonlinear improvement comes from concentrating sunlight into tiny spots, much like a child might with a magnifying glass on a sunny day. Concentrating the light on a tiny spot on the membrane results in a linear increase in heat, but the heating, in turn, produces a nonlinear increase in vapor pressure. And the increased pressure forces more purified steam through the membrane in less time.
“We showed that it’s always better to have more photons in a smaller area than to have a homogeneous distribution of photons across the entire membrane,” Alabastri said.
Halas, a chemist and engineer who’s spent more than 25 years pioneering the use of light-activated nanomaterials, said, “The efficiencies provided by this nonlinear optical process are important because water scarcity is a daily reality for about half of the world’s people, and efficient solar distillation could change that.
“Beyond water purification, this nonlinear optical effect also could improve technologies that use solar heating to drive chemical processes like photocatalysis,” Halas said.
For example, LANP is developing a copper-based nanoparticle for converting ammonia into hydrogen fuel at ambient pressure.
Halas is the Stanley C. Moore Professor of Electrical and Computer Engineering, director of Rice’s Smalley-Curl Institute and a professor of chemistry, bioengineering, physics and astronomy, and materials science and nanoengineering.
NESMD is in development at the Rice-based Center for Nanotechnology Enabled Water Treatment (NEWT) and won research and development funding from the Department of Energy’s Solar Desalination program in 2018.
Rivian’s appearance at Amazon’s tech-focused re:MARS event this week drew some more attention from the celebrity crowd. Former NBA player Shaquille O’Neal paid a visit to the all-electric startup’s display and surprised onlookers by fitting his 7’1″, 300+ lb frame into the R1T pickup truck. “Shaq fits,” CEO RJ Scaringe tweeted after with a photo of the superstar in the driver’s seat.
Shaq himself posted a video of the event on his Instagram account. Rivian’s team is seen in the background,seemingly proud to have yet another celebrity take noticeof the amazing work they’ve done with their vehicles. Singer Rihanna attended the company’s local invite-only preview before its appearance at the New York International Auto Show in April.
Another major figure to visit Rivian at re:MARS, albeit not a surprising one given he’s the CEO of Amazon, was Jeff Bezos. In a video posted to Twitter, he’s seen walking around the event and having a look at all the tech on display.
“Got a chance to scout some of the cool tech at the first #reMARS event,”he posted, tagging Rivian and the other companies featured in the clip. During Amazon’s all-hands meeting in March, Bezos stated that he is fascinated by the emerging trends in the auto industry and referred to Scaringe as “one of the most missionary entrepreneurs [he’s] ever met.” Amazon invested $700 million dollars into Rivian during a funding round earlier this year.
Amazon’s re:MARS 2019 event is an information and networking conference sponsored by the online retail giant focused on artificial intelligence (AI), robotics, and other related Earth and space technologies, including self-driving. The latest research, scientific advancements, and industry innovations are shared during four-days of networking, keynotes, and information sessions. This was the first year for the event and it took place from June 4-7 at the Aria Resort & Casino in Las Vegas, Nevada.
Rivian’s appearance at re:MARS was announced via tweet on its official Twitter account. “What happens when you combine a thirst for adventure with automotive tech and AI? Meet the world’s first Electric Adventure Vehicle at #reMARS to find out,” it said, tagging Rivian andincluding the hashtag #alexaauto. RJ Scaringe has teased “Jurassic Park” style tours with its vehicles that would implement the self-driving technology the company also has in the works. Perhaps Amazon’s Alexa digital assistant could narrate, if speculating about connections between the two companies.
Rivian’s CEO also shared some new insights recently about the R1T pickup truck and the R1S SUV in an interview withThe Drive. In a discussion about the electric adventure company’s battery technology, Scaringe noted thatRivian is preparing solutions that will enable drivers to recharge their vehicles off the grid, such as auxiliary battery packs. He also added that the the cars would be capable of vehicle-to-vehicle charging, allowing two Rivians to charge each other. “We’ve designed the vehicle so you can have auxiliary battery packs. You can also charge Rivian-to-Rivian, which is a neat thing. You connect the two vehicles, and then I could hand you some electrons,” Scaringe said.
Overall, Rivian seems to be very well focused on developing its technology and appealing to a wide audience of future buyers.
Solar panels are fantastic pieces of technology, but we need to work out how to make them evenmore efficient– and scientists just solved a 40-year-old mystery around one of the key obstacles to increased efficiency.
A new study outlines a material defect in silicon used to produce solar cells that has previously gone undetected. It could be responsible for the 2 percent efficiency drop that solar cells can see in the first hours of use: Light Induced Degradation (LID).
Multiplied by the increasing number of panels installed at solar farms around the world, that drop equals a significant cost in gigawatts that non-renewable energy sources have to make up for.
In fact, the estimated loss in efficiency worldwide from LID is estimated to equate to more energy than can be generated by the UK’s 15 nuclear power plants. The new discovery could help scientists make up some of that shortfall.
“Because of the environmental and financial impact solar panel ‘efficiency degradation’ has been the topic of much scientific and engineering interest in the last four decades,” says one of the researchers, Tony Peaker from the University of Manchester in the UK.
“However, despite some of the best minds in the business working on it, the problem has steadfastly resisted resolution until now.”
To find what 270 research papers across four decades had previously been unable to determine, the latest study used an electrical and optical technique calleddeep-level transient spectroscopy (DLTS) to find weaknesses in the silicon.
Here’s what the DLTS analysis found: As the electronic charge in the solar cells gets transformed into sunlight, the flow of electrons gets trapped; in turn, that reduces the level of electrical power that can be produced.
This defect lies dormant until the solar panel gets heated, the team found.
“We’ve proved the defect exists, its now an engineering fix that is needed,”says one of the researchers, Iain Crowe from the University of Manchester.
The researchers also found that higher quality silicon had charge carriers (electrons which carry the photon energy) with a longer ‘lifetime’, which backs up the idea that these traps are linked to the efficiency degradation.
What’s more, heating the material in the dark, a process often used to remove traps from silicon, seems to reverse the degradation.
The work to push solar panel efficiency rates higher continues, with breakthroughs continuing to happenin the lab, and nature offering up plenty ofefficiency tipsas well. Now that the Light Induced Degradation mystery has been solved, solar farms across the globe should benefit.
“An absolute drop of 2 percent in efficiency may not seem like a big deal, but when you consider that these solar panels are now responsible for delivering a large and exponentially growing fraction of the world’s total energy needs, it’s a significant loss of electricity generating capacity,”says Peaker.
Since the Birth of the Space Age the dream of catching a ride to another solar system has been hobbled by the “tyranny ofthe rocket equation,” which sets hard limits on the speed and size of the spacecraft we sling into the cosmos.
Of the advanced propulsion concepts that could theoretically pull that off, few have generated as much excitement—and controversy—as the EmDrive.
First described nearly two decades ago, the EmDrive works by converting electricity into microwaves and channeling this electromagnetic radiation through a conical chamber. In theory, the microwaves can exert force against the walls of the chamber to produce enough thrust to propel a spacecraft once it’s in space.
At this point, however, the EmDrive exists only as a laboratory prototype, and it’s still unclear whether it’s able to produce thrust at all. If it does, the forces it generates aren’t strong enough to be registered by the naked eye, much less propel a spacecraft.
Over the past few years, however, a handful of research teams, including one from NASA, claim to have successfully produced thrust with an EmDrive. If true, it would amount to one of the biggest breakthroughs in the history of space exploration. The problem is that the thrust observed in these experiments is so small that it’s hard to tell if it’s real.
The resolution lies in designing a tool that can measure these minuscule amounts of thrust. So a team of physicists at Germany’s Technische Universität Dresden set out to create a device that would fill this need. Led by physicist Martin Tajmar, theSpaceDrive projectaims to create an instrument so sensitive and immune to interference that it would put an end to the debate once and for all.
In October, Tajmar and his team presented their second set of experimental EmDrivemeasurementsat the International Astronautical Congress, and their results will be published inActa Astronauticathis August. Based on the results of these experiments, Tajmar says a resolution to the EmDrive saga may only be a few months away.
Many scientists and engineers dismiss the EmDrive because it appears to violate the laws of physics. Microwaves pushing on the walls of an EmDrive chamber seem to generate thrust ex nihilo, which runs afoul of the conservation of momentum—it’s all action and no reaction. Proponents of the EmDrive, in turn, have appealed to fringe interpretations of quantum mechanics to explain how the EmDrive might work without violating Newtonian physics.
“From the theory point of view, no one takes this seriously,” Tajmar says. If the EmDrive is able to produce thrust, as some groups have claimed, he says they have “no clue where this thrust is coming from.” When there’s a theoretical rift of this magnitude in science, Tajmar sees only one way to close it: experimentation.
In late 2016, Tajmar and 25 other physicists gathered in Estes Park, Colorado, for thefirst conferencededicated to the EmDrive and related exotic propulsion systems. One of the most exciting presentations was given by Paul March, a physicist at NASA’sEagleworks lab, where he and his colleague Harold White had been testing various EmDrive prototypes. According to March’s presentation and a subsequent paperpublishedin theJournal of Propulsion and Power, he and White observed several dozen micro-newtons of thrust in their EmDrive prototype. (For the sake of comparison, a single SpaceX Merlin engine produces around 845,000 Newtons of thrust at sea level.)
The problem for Harold and White, however, was that their experimental setup allowed for several sources of interference, so they couldn’t say for sure whether what they observed was thrust.
Tajmar and the Dresden group used a close replica of the EmDrive prototype used by Harold and White in their tests at NASA. It consists of a copper frustum—a cone with its top lopped off—that is just under a foot long. This design can be traced back to the engineer Roger Shawyer, who first described the EmDrive in 2001. During tests, the EmDrive cone is placed in a vacuum chamber. Outside the chamber, a device generates a microwave signal that gets relayed, using coaxial cables, to antennas inside the cone.
This isn’t the first time the Dresden team has sought to measure nearly imperceptible amounts of force. They built similar contraptions for their work on ion thrusters, which are used to precisely position satellites in space. These micro-newton thrusters are the kind that were used by the LISA Pathfinder mission, which needs extremely precise positioning ability to detect faint phenomena like gravitational waves. But to study the EmDrive and similar propellantless propulsion systems, Tajmar says, required nano-newton resolution.
Their approach was to use a torsion balance, a pendulum-type balance that measures the amount of torque applied to the axis of the pendulum. A less sensitive version of this balance was also used by the NASA team when they thought their EmDrive produced thrust.
To accurately gauge the small amount of force, the Dresden team used a laser interferometer to measure the physical displacement of the balance scales produced by the EmDrive. According to Tajmar, their torsion scale has a nano-newton resolution and supports thrusters weighing several pounds, making it the most sensitive thrust balance in existence.
But a really sensitive thrust balance isn’t much use unless you can also determine whether the detected force is in fact thrust and not an artifact of outside interference. And there are plenty of alternate explanations for Harold and White’s observations.
To determine whether an EmDrive actually produces thrust, researchers must be able to shield the device from interference caused by the Earth’s magnetic poles, seismic vibrations from the environment, and the thermal expansion of the EmDrive due to heating from the microwaves.
Tweaks to the design of the torsion balance—to better control the EmDrive’s power supply and shield it from magnetic fields—took care of some of the interference issues, Tajmar says. A more difficult problem was how to address “thermal drift.” When power flows to the EmDrive, the copper cone heats up and expands, which shifts its center of gravity just enough to cause the torsion balance to register force that can be mistaken as thrust. Tajmar and his team hoped that changing the orientation of the thruster helped address that issue.
Over the course of 55 experiments, Tajmar and his colleagues registered an average of 3.4 micro-newtons of force from the EmDrive, which was very similar to what the NASA team found. Alas, these forces did not appear to pass the thermal drift test. The forces seen in the data were more indicative of thermal expansion than thrust.
All hope is not lost for the EmDrive, however. Tajmar and his colleagues are also developing two additional types of thrust balances, including a superconducting balance that will, among other things, help to eliminate false positives produced by thermal drift.
If they detect force from an EmDrive on these balances, there’s a high probability that it is actually thrust. But if no force is registered on these balances, it likely means that all the previous EmDrive thrust observations were false positives. Tajmar says he hopes to have a final verdict by the end of the year.
But even a negative result from that work might not kill the EmDrive for good. There are many other propellantless propulsion designs to pursue. And if scientists ever do develop new forms of weak propulsion, the hyper-sensitive thrust balances developed by Tajmar and the Dresden team will almost certainly play a role in sorting science fact from science fiction.