Lighter, Stronger, and Morphable

Dean Sigler Sustainable Aviation 2 Comments

If you have a pre-teen roaming around the house, you more than likely know the shared delight of assembling the biggest possible thing you can make from Lego® blocks.  There must be something of that delight in the Center for Bits and Atoms at the Massachusetts Institute of Technology (MIT). There, researchers have invented, “A new approach to assembling big structures — even airplanes and bridges — out of small interlocking composite components,” according to a story by David L. Chandler of the MIT News Office. Neil Gershenfeld, director of the Center, and post-doctoral student Kenneth Cheung recently co-authored a paper published in the journal Science, in which they describe assembling strong lightweight structures with “cubocts,” lattice structures that are the lightest and strongest in existence, as stated in the Center’s publications. The Center claims 12.3 megaPascals, or 1,784 pound per square inch strength for the 7.3 milligrams per cubic centimeter material (about 0.45 pounds per cubic foot).  Balsa wood, …

Thinner than Kleenex®, as Powerful as the Sun

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David L. Chandler of the Massachusetts Institute of Technology (MIT) News Office reports that an MIT research team headed by Jeffrey Grossman has found a way to make sheets that push “towards the ultimate power conversion from a material” for solar power.  His team has managed to fabricate molecule-thick photovoltaic sheets which could pack hundreds of times more power per weight than conventional solar cells. Senior author of a new paper on the team’s study in Nano Letters, Grossman found that despite the interest in two-dimensional materials such as graphene – only an atom thick – few have studied their potential for solar applications.  Grossman says, “They’re not only OK, but it’s amazing how well they do.” Stacking sheets of graphene and materials such as molybdenum disulfide would make solar cells with one to two percent efficiency in converting sunlight to electricity.  That seems disappointingly low compared to the 15 to 20 percent efficiency of commercially available silicon solar cells. …

Making Graphene and Carbon Fibers Even Lighter and Stronger

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While scientists at Columbia University have used chemical vapor deposition (CVD) to create large sheets of stronger-than-average graphene, a research team at Massachusetts Institute of Technology (MIT) has found ways to weave stronger carbon nanotubes. James Hone and Jeffrey Kysar, professors of mechanical engineering at Columbia University, learned that the enormous strength of graphene is usually achieved in only small patches.  The “grain boundaries” for larger sheets were often far weaker than the theoretical strengths of which the material is capable. That strength is phenomenal.  Hone explains, “It would take an elephant, balanced on a pencil, to break through a sheet of graphene the thickness of Saran Wrap.” Results of their study were published in the journal Science. The paper’s lead author, Gwan-Hyoung Lee, a postdoctoral fellow in the Hone lab, says, “Our findings clearly correct the mistaken consensus that grain boundaries of graphene are weak. This is great news because graphene offers such a plethora of opportunities both for …

Ionic Thrusters Offer Quiet Flight

Dean Sigler Electric Powerplants, Feedback, Sustainable Aviation 3 Comments

Gizmag and Science Daily both covered a propulsion system that’s been with us for many decades, but which is just now seeing practical applications in space flight, and may be adapted to terrestrial winged vehicles. Your editor might have passed it over as overhyped, but the research came from the Massachusetts Institute of Technology (MIT) and was published in The Proceeding of the Royal Academy – two good indicators of veracity. Jennifer Chu of MIT’s News Office explains, “When a current passes between two electrodes — one thinner than the other — it creates a wind in the air between. If enough voltage is applied, the resulting wind can produce a thrust without the help of motors or fuel.”  That phrase, “If enough voltage is applied…” is a significant qualification. “Electrohydrodynamic thrust,” or “ionic wind” has been known since the 1960s, but limited to hobbyists and science fair projects.  This video from China demonstrates the use of electric thrusters to …

On a Clear Day, I Can See My iPad

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Dr. Brien Seeley, President of the CAFE Foundation, shared the news of an exciting breakthrough that could make the see-through parts of an airplane’s solar collectors.  Most solar collectors have a black or near-black look because they are absorbing light in the visible spectrum.  Pulling energy from infrared or ultraviolet spectra invisible to the human eye allows Ubiquitous Energy’s Clearview Power translucent film of to be laid over iPad and Kindle screens and keep them charged constantly. Consider the possibilities of such films covering the Plexiglas or carbonate canopies on aircraft.  Even those portions could then be energy collectors.  On craft such as electric sustainer motor powered sailplanes, the glazed area comprises a large part of the total fuselage surface area. According to the MIT Technology Review, “…The transparent solar cells are made of various organic layers, deposited one at a time on top of a glass or film. This process could easily be integrated into thin-film deposition systems found …

New “Leaf” Turns Over More Energy

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Scientists have been working on imitating nature’s ability to photosynthesize the sun’s energy, much as plants turn that energy into food for their health and growth.  Daniel Nocera, for instance, created an artificial leaf that split water into oxygen and hydrogen that could fire up a small fuel cell and run an electric light.  According to a Science Pub lecture your editor recently attended, an eight-ounce glass of water can power a 60-Watt bulb for 20 hours.  Nocera, in a Pop! Tech talk, claims an Olympic-size swimming pool could supply all the world’s energy needs. Nocera now works at Harvard, but researchers at Massachusetts Institute of Technology (MIT), his former home, are taking his work further, detailing all the limitations that keep his “artificial leaf” from giving off more storable energy. As explained in the MIT press release, “The original demonstration leaf, in 2011, had low efficiencies, converting less than 4.7 percent of sunlight into fuel… But the team’s new …

Cambridge, MIT Chasing Room-Temperature Hydrogen

Dean Sigler Electric Powerplants, Sustainable Aviation 1 Comment

News from Cambridge University shows some promise for inexpensive production of hydrogen, an elusive process considering the lightest element in creation is also the most common, said to make up 90 percent of the visible universe.  On earth, it readily combines with oxygen to form water, a handy thing to have around for the benefit of our species. Getting hydrogen out of the water so that we can burn it in our cars and airplanes is a frustrating process, though, often requiring more energy for the extraction than can be obtained from its combustion. According the National Renewable Energy Laboratory, “To make [hydrogen] usable in fuel cells or otherwise provide energy, we must expend energy or modify another energy source to extract it from the fossil fuel, biomass, water, or other compound in which it is found. Nearly all hydrogen production in the United States today is by steam reformation of natural gas. This, however, releases carbon dioxide in the …

A Layer of Graphene, A Layer of Nanowires…

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Combine nano-anything with graphene, and that seems to describe most of what’s driving physics and chemistry laboratories at our major universities.  The blog reported last week on Princeton researchers who’ve created a thin, flexible solar cell that absorbs 96-percent of received light and draws energy from off-axis and varied wavelengths of light. MIT researchers, too, have created a thin, flexible solar cell, but one based on layers of flexible graphene sheets, each coated with a layer of nanowires.  Besides flexibility, these sheets offer transparency, enabling their use on windows as well as other surfaces. David Chandler, reporting for MIT states that the new cells may prove to be far less expensive than today’s silicon equivalents, which require high-purity silicon that undergoes crystallization and extremely thin slicing.  Alternatives use indium tin oxide (ITO), itself an expensive substitute for or adjunct to silicon.  Nanostructured cells such as that from Princeton may allow lower-priced material, although one version uses a gold foil top layer. Silvija …

There’s Light at the End of the Funnel

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Solar cells are relatively inefficient at gathering the total range of sunlight’s spectrum that falls on them every day.  Trying to find a way to capture more than a single wavelength or narrow band of the solar light, scientists at Massachusetts Institute of Technology (MIT) and at Peking University in China propose putting a strain on solar cells, creating a spatially varying bandgap that would react to more of the colors in light and thus give off more electricity.  Changing the bandgap in a solar collector’s material enables excitation of electrons from not just visible light, but from energy sources such as infrared radiation. This has the potential to increase the cell’s energy output enormously since most of the sun’s radiation is in invisible form.   Bandgap is a complex concept, and MIT provides a brief tutorial here. MIT’s news office reports: “’We’re trying to use elastic strains to produce unprecedented properties,’ says Ju Li, an MIT professor and corresponding …

Spinach, Photosynthesis, and Solar Energy

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Spinach is the Rodney Dangerfield of the vegetable kingdom, and despite the best efforts of nutritionists, Popeye, and school lunch ladies to boost its respect levels, goes unwanted by many. But not by the team at Vanderbilt University who have combined it with silicon in a “biohybrid” solar cell. According to Vanderbilt’s David Cliffel, associate professor of chemistry, “This combination produces current levels almost 1,000 times higher than we were able to achieve by depositing the protein on various types of metals. It also produces a modest increase in voltage.” Cliffel collaborated on the project with Kane Jennings, professor of chemical and biomolecular engineering. “If we can continue on our current trajectory of increasing voltage and current levels, we could reach the range of mature solar conversion technologies in three years.” Over 40 years ago, scientists found that Photosystem 1 (PS1), a protein involved in photosynthesis, continued to produce photosynthetic energy even after it was removed from its host plant. …