În cele din urmă: celule solare non-toxice și ieftine, pentru clădiri cu energie zero

Ele pot fi depozitate direct pe materiale ca straturi subtiri facut sunt de 50 de ori mai subtire decat un fir de păr uman, astfel încât nu este nevoie să producă siliciu«napolitana»celule și să le interconecta separat“, a adăugat el. „Ei, de asemenea, să răspundă mai bine decât siliciu la lungimi de unda albastru de lumină, și pot fi stivuite ca un film subțire pe partea de sus a celulelor de siliciu pentru a îmbunătăți performanța generală În cele din urmă.“
Prin posibilitatea de a depozita celule solare CZTS pe diverse suprafețe, echipa Hao cred că acest lucru le pune ferm pe drumul de a face celule fotovoltaice thin-film facut poate fi rigid sau flexibil și durabil și suficient de ieftine pentru a fi integrate pe scară largă în clădiri pentru a genera energie electrică de greve lumina soarelui au structuri, cum ar fi: geamuri, fațade, țigle și ferestre.

Posted: Apr 28, 2016

At last: Non-toxic and cheap thin-film solar cells for zero-energy buildings

(Nanowerk News) ‘Zero-energy’ buildings – which generate as much power as they consume – are now much closer after a team at Australia’s University of New South Wales achieved the world’s highest efficiency using flexible solar cells that are non-toxic and cheap to make.
Until now, the promise of ‘zero-energy’ buildings been held back by two hurdles: the cost of the thin-film solar cells (used in façades, roofs and windows), and the fact they’re made from scarce, and highly toxic, materials.
That’s about to change: the UNSW team, led by Dr Xiaojing Hao of the Australian Centre for Advanced Photovoltaics at the UNSW School of Photovoltaic and Renewable Energy Engineering, have achieved the world’s highest efficiency rating for a full-sized thin-film solar cell using a competing thin-film technology, known as CZTS.
Low-toxicity CZTS Solar Cells
The new high-efficiency, low-toxicity solar cells developed by UNSW’s Australian Centre for Advanced Photovoltaics. (Image: Robert Largent/UNSW)
NREL, the USA’s National Renewable Energy Laboratory, confirmed this world leading 7.6% efficiency in a 1cm2 area CZTS cell this month.
Unlike its thin-film competitors, CZTS cells are made from abundant materials: copper, zinc, tin and sulphur.
And CZTS has none of the toxicity problems of its two thin-film rivals, known as CdTe (cadmium-telluride) and CIGS (copper-indium-gallium-selenide). Cadmium and selenium are toxic at even tiny doses, while tellurium and indium are extremely rare.
„This is the first step on CZTS’s road to beyond 20% efficiency, and marks a milestone in its journey from the lab to commercial product,” said Hao, named one of UNSW’s 20 rising stars last year. „There is still a lot of work needed to catch up with CdTe and CIGS, in both efficiency and cell size, but we are well on the way.”
„In addition to its elements being more commonplace and environmentally benign, we’re interested in these higher bandgap CZTS cells for two reasons,” said Professor Martin Green, a mentor of Dr Hao and a global pioneer of photovoltaic research stretching back 40 years.
„They can be deposited directly onto materials as thin layers that are 50 times thinner than a human hair, so there’s no need to manufacture silicon ‘wafer’ cells and interconnect them separately,” he added. „They also respond better than silicon to blue wavelengths of light, and can be stacked as a thin-film on top of silicon cells to ultimately improve the overall performance.”
By being able to deposit CZTS solar cells on various surfaces, Hao’s team believe this puts them firmly on the road to making thin-film photovoltaic cells that can be rigid or flexible, and durable and cheap enough to be widely integrated into buildings to generate electricity from the sunlight that strikes structures such as glazing, façades, roof tiles and windows.
However, because CZTS is cheaper – and easier to bring from lab to commercialisation than other thin-film solar cells, given already available commercialised manufacturing method – applications are likely even sooner. UNSW is collaborating with a number of large companies keen to develop applications well before it reaches 20% efficiency – probably, Hao says, within the next few years.
„I’m quietly confident we can overcome the technical challenges to further boosting the efficiency of CZTS cells, because there are a lot of tricks we’ve learned over the past 30 years in boosting CdTe and CIGS and even silicon cells, but which haven’t been applied to CZTS,” said Hao.
Currently, thin-film photovoltaic cells like CdTe are used mainly in large solar power farms, as the cadmium toxicity makes them unsuitable for residential systems, while CIGS cells is more commonly used in Japan on rooftops.
First Solar, a US$5 billion behemoth that specialises in large-scale photovoltaic systems, relies entirely on CdTe; while CIGS is the preferred technology of China’s Hanergy, the world’s largest thin-film solar power company.
Thin-film technologies such as CdTe and CIGS are also attractive because they are physically flexible, which increases the number of potential applications, such as curved surfaces, roofing membranes, or transparent and translucent structures like windows and skylights.
But their toxicity has made the construction industry – mindful of its history with asbestos – wary of using them. Scarcity of the elements also renders them unattractive, as price spikes are likely as demand rises. Despite this, the global market for so-called Building-Integrated Photovoltaics (BIPV) is already valued at US$1.6 billion.
Hao believes CZTS’s cheapness, benign environmental profile and abundant elements may be the trigger that finally brings architects and builders onboard to using thin-film solar panels more widely in buildings.
Until now, most architects have used conventional solar panels made from crystalline silicon. While these are even cheaper than CZTS cells, they don’t offer the same flexibility for curved surfaces and other awkward geometries needed to easily integrate into building designs.
Source: University of New South Wales

Read more: At last: Non-toxic and cheap thin-film solar cells for zero-energy buildings

Sisteme de armament Texas (TWS) Flip-Up Gen-3 Câmp de acostare pentru câini AK Cover Top-Rail Cover și Gen-3 AK Tactical Hand Guard(M-LOK) pentru montarea de optică de luptă cu putere variabilă pe AK-47 / AKM / AKS / KALASHNIKOV AK-47 / AKM / Platformel AK-74 pentru pușcă / carabină / SBR (Texas Weapon Systems(TWS) Flip-Up Gen-3 Dog Leg Rail AK Top-Rail Cover and Gen-3 AK Tactical Hand Guard( M-LOK) System for Mounting Variable-Power Combat Optics on the Kalashnikov AK-47/AKM/AK-74 Rifle/Carabine/SBR Platforms )

Sisteme de armament

Mark 23

Echipa de cercetare realizează un fotodetector cu 3 culori(Research team realizes 3-color photodetector)

fotodetector cu infraroșu cu infraroșu cu infraroșu cu trei culori, cu undă scurtă. Cu noul design, dispozitivele pot detecta diferite benzi de frecvență în infraroșu prin simpla variație a tensiunii aplicate. Acest lucru ar putea deschide o gamă largă de aplicații potențiale, inclusiv televizoare color infraroșu și imagini în infraroșu cu trei culori.
„Un dispozitiv capabil să detecteze diferite valuri de infraroșu este foarte de dorit în sistemele de imagistică infraroșie de nouă generație

Posted: Apr 22, 2016

Research team realizes 3-color photodetector

(Nanowerk News) While infrared waves are available in short, mid, and long lengths, most detection devices are unable to harness all three at the same time.
Now Northwestern University’s Manijeh Razeghi and her team have developed a new approach in device design to realize a three-color, shortwave-midwave-longwave infrared photodetector. With the new design, the devices can detect different infrared wavebands by simply varying the applied bias voltage. This could open up a range of potential applications, including infrared color televisions and three-color infrared imaging.
„A device capable of detecting different infrared wavebands is highly desirable in the next generation infrared imaging systems,” said Razeghi, Walter P. Murphy Professor of Electrical Engineering and Computer Science in Northwestern’s McCormick School of Engineering.
Supported by DARPA, the Army Research Laboratory, Air Force Research Laboratory, and NASA, the team’s finding were published on April 7 in Nature Scientific Reports („High performance bias-selectable three-color Short-wave/Mid-wave/Long-wave Infrared Photodetectors based on Type-II InAs/GaSb/AlSb superlattices”).
Led by Razeghi, the researchers invented and investigated the new design for three-color photodiodes without using additional terminal contacts. The resulting photodetector is based on indium-arsenide/gallium-antimonide/aluminum-antimonide type-II superlattices.
As the applied bias voltage varies, the photodetector sequentially exhibits the behavior of three different colors, corresponding to the bandgap of three absorbers, and achieves well-defined cut-off wavelengths and high-quantum efficiency in each channel.
This new research builds on the Razeghi group’s many years of work in Northwestern’s Center for Quantum Devices, including the development of the first single-color, short-wavelength infrared photodetector and two-color, shortwave-midwave infrared photodetector based on type-II superlattices.
„I am fascinated by these results,” Razeghi said. „The initial success in this demonstration will drive us to the new frontier of infrared detection and imaging technology.”
Source: Northwestern University

Curenții oscilanți indică aplicarea practică a izolatoarelor topologice(Oscillating currents point to practical application for topological insulators)

În condițiile corecte, materialul, un compus numit hexaborid de samarium, este un izolator topologic – ceva care conduce electricitatea pe suprafața sa, dar nu prin interiorul său. Primele exemple de izolatoare topologice au fost create recent în laborator, iar descoperirea lor a dat naștere unui mare interes teoretic și experimental.

Posted: Apr 22, 2016

Oscillating currents point to practical application for topological insulators

(Nanowerk News) Scientists studying an exotic material have found a potential application for its unusual properties, a discovery that could improve devices found in most digital electronics.
Under the right conditions the material, a compound called samarium hexaboride, is a topological insulator—something that conducts electricity on its surface but not through its interior. The first examples of topological insulators were only recently created in the lab, and their discovery has sparked a great deal of theoretical and experimental interest.
Now, a team of physicists at JQI and the University of California, Irvine, may have found a use for tiny crystals of samarium hexaboride. When pumped with a small but constant electric current and cooled to near absolute zero, the crystals can produce a current that oscillates. The frequency of that oscillation can be tuned by changing the amount of pump current or the crystal size.
A scanning electron microscope picture of platinum wires on a samarium hexaboride crystal
A scanning electron microscope picture of platinum wires on a samarium hexaboride crystal, which can produce an electric current that flips millions of times a second. (Image: A. Stern/UCI)
This behavior—which mimics that of components in modern cell phones and computers in a much smaller package—is due to a complex interaction between currents carried by protected electronic states on the crystal’s surface and the temperature changes they provoke in the crystal’s interior.
„It’s not often that devices rely on such sophisticated ingredients,” says JQI Fellow Victor Galitski, who partnered with Dmitry Efimkin, a postdoctoral researcher in the Condensed Matter Theory Center at the University of Maryland, as well as experimentalists at UCI on the new work. Galitski and his colleagues published the results April 20 in Physical Review Letters („Radio Frequency Tunable Oscillator Device Based on a SmB6 Microcrystal”).
The work is the latest development in more than four decades of research on samarium hexaboride (link is external), which is known for its unusual properties at low temperatures. At high temperatures, the material acts like an ordinary metal, but as it is cooled down, its resistance to electrical currents increases. Unlike most materials, however, the resistance doesn’t keep increasing. Rather, it plateaus, even as the temperature continues to drop.
In 2010, Galitski and several colleagues hypothesized that this mysterious behavior arose because samarium hexaboride is a particular kind of material, which they dubbed a topological Kondo insulator. They predicted that such a material would exhibit a transition from a conventional metal at high temperatures to a topological insulator when cooled down. Physicists raced to verify the prediction by trying to observe signature surface currents. Along the way a group at UCI noticed that the material could also produce an oscillating current („Limit Cycle and Anomalous Capacitance in the Kondo Insulator SmB6„).
„That was a completely accidental discovery,” says Jing Xia, an associate professor of physics at the University of California, Irvine, and a co-author of the new paper. „We had no clue what was going on.”
The frequency of those early oscillating currents was too low to be useful in modern devices, so Xia and Galitski began parallel investigations, with Xia trying to scale down the crystal size to create faster oscillations and Galitski trying to explain the origin of the fluctuating current.
The new paper is the culmination of their efforts. The crystals are now much smaller—just 100 microns long compared to sizes of millimeters in the previous work. This leads to current oscillations that occur tens of millions of times a second, frequencies which can drive radio transmitters or the clocks found in computer chips.
The small size also created headaches for Alex Stern, a graduate student at UCI and lead author of the paper, who painstakingly connected miniscule platinum wires to the tiny crystals in order to make the measurements. „It was really just getting lucky after doing it several times,” Stern says. „And once you get one wire on, the hardest thing was to get the second one on right next to it.”
Meanwhile, Galitski and Efimkin worked on developing a model to explain the origin of the current oscillations. In the paper, the researchers derive equations that describe how current-carrying charges are transported through the material. Depending on experimental parameters, the charges either flow steadily or fluctuate, the latter corresponding to an oscillating current. Those oscillations appear for only a narrow range of parameters, and the researchers say they were lucky that their sample fall into this regime.
Oscillating currents
Despite the technical complexity of the theory, Galitski says that the physical mechanism that drives these fluctuations is simple. The essential steps are shown in the graphic above. As a current begins to flow on the crystal’s surface, a high resistance causes some of the current’s energy to heat the sample’s interior. This causes the electrical resistance of the interior to decrease slightly, momentarily allowing more current to flow. But the decreased resistance also dissipates less energy, so the interior cools back down and the original resistance is restored. This process repeats itself many times a second to produce the fluctuating current seen in experiments.
The authors suspect that smaller crystals could produce even faster oscillations, on the order of a trillion per second. The team says that this might happen for crystals that are 10 times smaller than the 100-micron long crystals they are using now. They add that there is no fundamental reason that similar devices that support rapid oscillations cannot be engineered to operate at room temperature.
Source: Joint Quantum Institute

Noi instrumente pentru proiectarea colaborării om-mașină(New Tools for Human-Machine Collaborative Desing)

DARPA caută idei inovatoare pentru valorificarea noilor materiale și metode de fabricare.Materialele avansate încorporează din ce în ce mai multe proprietăți contraintuitive, cum ar fi rezistența excesivă și super-ușurință, în timp ce producția de aditivi și alte tehnologii noi îmbunătățesc enorm capacitatea de a modela aceste materiale noi în forme care anterior ar fi fost extrem de costisitoare sau chiar imposibil de creat

New Tools

Materialul nou combină proprietăți utile, de obicei incompatibile(New material combines useful, typically incompatible properties)

au creat un material complet nou, în care pot coexista proprietăți complet contradictorii.
Compusul, despre care cercetatorii au descris intr-un studiu publicat 20 aprilie de revista Nature ( „Metalele polar prin design geometric” ), este un metal polar.

Posted: Apr 21, 2016

New material combines useful, typically incompatible properties

(Nanowerk News) Mild-mannered Dr. Jekyll and malicious Mr. Hyde were opposite aspects of the same man, and their story ended in tragedy because the two couldn’t peacefully coexist.
Most materials, too, are capable of being only one thing at a time, but a team of engineers and physicists at the University of Wisconsin-Madison have created an entirely new material in which completely contradictory properties can coexist.
The compound, which the researchers described in a study published April 20 by the journal Nature („Polar metals by geometric design”), is a polar metal.
„Polar metals should not be possible,” says Chang-Beom Eom, the professor of materials science and engineering who led the research.
Undeterred by the laws of the universe, Eom and colleagues created a compound that is a scientific oxymoron. Through a new synthesis approach supported by computational modeling, the group made a crystal with multiple personalities: part polar, part metallic.
Metals conduct electricity because electrons flow freely throughout them. Polar materials, by contrast, impede the free flow of electrons and work as electrical insulators.
Eom’s team needed to find something that can demonstrate both insulating and conducting properties. First, they separated the polar and metallic parts of the crystal. Some electrons gave rise to the metallic nature, moving within the material to conduct electricity. Other electrons contributed to the polar properties.
However, because the natural molecular structure of the material is symmetrical, even after separating the two components, the material as a whole would not act polar. Equal and opposite arrangements of electrons canceled each other out. To overcome this obstacle, the researchers synthesized the substance with slightly off-kilter atoms, which threw off the internal symmetry enough to make the material polar.
„The initial calculations that the theory suggested did not show the polar nature so we experimentally tested the materials, then went back and improved the models,” says Eom. „We looped between theory and experiments, but most importantly, we actually created the material, demonstrated its polar and metallic properties, and developed an understanding of how this is happening.”
Ultimately, Eom and colleagues made the polar metal by painstakingly growing thin films of material one atom at a time. Crucially, they grew the substance on top of a supporting lattice with a slightly offset molecular organization. Tightly clamping the growing film to this support skewed the internal arrangement of their material, stabilizing its internal geometry in the asymmetrical orientation necessary to maintain polarity.
Synthesizing and characterizing this first-of-its-kind material required patience and precision. The researchers counted every atom deposited on the surface, as the substance slowly grew one layer at a time. They then used multiple complex optical and electronic and structural measurements to determine its properties.
Their approach is an attempt to accelerate the discovery of multifunctional materials with unusual coexisting properties, paving the way to devices with the ability to perform simultaneous electrical, magnetic and optical functions.
„This has been a complex effort, and theoretical and experimental contributions from all collaboration members has been essential. The project would not succeed otherwise,” says Eom.
Source: University of Wisconsin-Madison

Senzorii inteligenți tipăriți monitorizează secvențele de mișcare(Smart printed sensors monitor movement sequences)

continuare a testelor electronice, precum și a testelor de uzură și spălare.
Materialele senzorilor care vin în folosință sunt flexibile, transparente și potrivite pentru diferite aplicații, alături de textile inteligente: Înregistrează presiune și deformare și pot astfel să funcționeze ca senzori de atingere sau mișcare. Sensibilitatea acestora la abaterile de temperatură permite în continuare monitorizarea schimbărilor de temperatură sau a interacțiunii fără contact, de exemplu ca senzori de proximitate.Senzorii din îmbrăcămintea funcțională ar putea ajuta la optimizarea exercițiilor prin monitorizarea secvențelor de mișcare. Un nou material senzor transparent, dezvoltat de Fraunhofer ISC, permite detectarea senzorilor de măsurare a mișcării pe textile. Materialul inovativ va fi prezentat pe IDTechEX Europe la standul F16 din Estrel Berlin, în zilele de 27 și 28 aprilie 2016.

Posted: Apr 21, 2016

Smart printed sensors monitor movement sequences

(Nanowerk News) Wearable technology has caught on to progress health and fitness. Simply worn on the body, smart garments can, for instance, track activity. Sensors in functional clothing could also help optimize exercises by monitoring movement sequences. A novel transparent sensor material developed by Fraunhofer ISC enables movement measuring sensors to be printed onto textiles. The innovative material will be presented on IDTechEX Europe at booth F16 in the Estrel Berlin on 27 and 28 April 2016.
transparent printed sensor
Transparent printed sensors. (Image: K. Selsam-Geißler, Fraunhofer ISC)
Accessories like smart bracelets or smart watches are trending as »personal health coaches«, prompting the bearer to provide for sufficient sleep and activity or a healthy diet. Sensor-embedded textile solutions are a far more challenging and also more expensive approach. Often, function will override appearance. The new materials developed by Fraunhofer ISC might offer a cost-efficient alternative with the extra benefit of more adjustable appearance options.
In cooperation with Fraunhofer ISIT and with support of the project partners from the industry, the new sensor technology will be incorporated into a prototype shirt. This so-called MONI shirt will feature a number of functions but is foremost designed to monitor movement sequences. In an initial step, Fraunhofer ISC has developed novel piezoelectric polymer sensor printing pastes free from toxic solvents while Fraunhofer ISIT has provided the evaluation electronics. The next development steps are planned in close dialogue with the industry partners. They will include field tests on several types of textiles and applications, the further optimization of the electronics as well as wear and washability tests.
The sensor materials coming to use are flexible, transparent and suitable for various applications also beside of smart textiles: They register pressure and deformation and can thus serve as touch or motion sensors. Their sensitivity to temperature deviations further enables monitoring of temperature changes or non-contact interaction, e. g. as proximity sensors.
Non-transparent printed sensor
Non-transparent printed sensors. (Image: K. Selsam-Geißler, Fraunhofer ISC)
A simple screen printing process is all it takes to apply the sensor pastes onto textile fabrics or plastic films. Manufacturing encompasses two steps: First, the pattern is printed. Then, the sensors are subjected to an electric field making the piezolectric polymers align to adopt the targeted pressure sensitivity. The cost-efficient screen printing process is a definite plus when it comes to industrial use. It is the key to mass production of printed sensors on textiles.
Thanks to its transparency and flexibility, the new sensor material offers freedom of design in color and form for textiles and garments. As the sensors are much thinner than a human hair and applicable in whatever form, the wearer will hardly notice them embedded in a garment. There’s yet another benefit: the sensors do not require any power source like a battery. Instead, they harvest energy.
Smart textiles like this could be employed in health care or assisted living. In eldercare, everyday life movement sequences could be monitored and failure noticed. Additionally, it would be possible to monitor body signals of in-patients, such as temperature or breathing. This could be especially beneficial for bedridden patients or babies. Some day, even heart rate surveillance may be possible. Last but not least, functional sensor clothing could achieve cost reductions in the health care system. On top of assuming patient monitoring functions it could add to preventive health care.
In Addition to printed sensors on textiles Fraunhofer ISC shows textilintegrated pressure sensors made of silicone e. g. to measure pressure in shoes.
Source: Fraunhofer-Institut für Silicatforschung

Pe ferma din Africa (On the farm in Africa)

Brățările au atras atenția cercetătorilor din întreaga lume;pentru a evalua benzile de utilizat în monitorizarea expunerilor chimice legate de exploatații agricole și lucrători;ele oferă doar o înregistrare a expunerii cumulative a unei persoane în timp

On the farm

Această tehnologie este concepută pentru a prezice Big Esrthquakes și a salva vieți. De ce nu se poate obține finanțare?(This Technology Is Designed to Predict Big Esrthquakes and Save Lives.So Why Can’t It Get Funding?)

Au fost arătate două metode de salvare a vieților: construirea de clădiri care protejează cutremurele și instalarea unor sisteme care să emită o alarmă când un cutremur loveste, dând oamenilor mai departe de epicentrul de câteva secunde avertizând

This Technology