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Cylindrical solar tubes from Solyndra.

Business is beginning to take shape at Solyndra, and the shape it’s taking is tubular. The Fremont, Calif.-based solar power manufacturer began selling its novel cylindrical-shaped solar tubes in July ‘08 and, according to CEO Chris Gronet, the firm already has racked up $1.2 billion in contracted orders. The differences between Solyndra’s solar tubes and conventional solar panels are many. The obvious difference is their shape. Unlike conventional solar flat panels, a single Solyndra “panel” is comprised of 40 glass cylinders placed horizontally side-by-side. Their tubular shape allows each cylinder to collect sunlight from any angle, the company says.

By painting a roof white, the firm even enables cylinders to capture reflected sunlight from their “down” side. Differences also occur in installation. Traditional solar flat panels must be precisely angled with devices that add cost and time, a Solyndra press release explains. It also claims exact spacing must be provided between panels so they don’t obstruct each other’s performance, and they must be anchored by ballast or “rooftop penetration” to meet wind-loading requirements. In contrast, Solyndra’s solar tubes can be laid beside each other in straight lines across a roof. Angling and extra spacing isn’t necessary and, because the wind blows around and through Solyndra panels, the need for rooftop anchoring is also reduced.

All this adds up to a Solyndra installation costing about half that of a regular flat-panel installation, Solyndra CEO Gronet says. Another major difference between the solar alternatives is in the way they are manufactured. While traditional flat panels are assembled from photovoltaic cells made from silicon, Solyndra tubes are made from a less expensive thin-film of semiconductor material. This material - comprised of copper, indium, gallium and selenium - is deposited on a glass tube, which is nested inside another glass tube. The outer tube concentrates sunlight and protects the solar film on the inside tube. Finally, unlike most traditional solar-panel makers, Solyndra’s management is not targeting the residential market. Instead, Solyndra’s solar tubes are being sold through installers exclusively to the commercial rooftop market. Gronet figures this market adds up to about 30 billion square feet of warehouse, supermarket, factory and other commercial rooftop space in the U.S. alone.

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Rice's Vicki Colvin, codirector of new fullerene study.

Rice University is undertaking a new study, funded by the National Science Foundation, that will track “tagged nanoparticles” as they travel through the environment. The purpose of the study, which focuses on fullerenes, is to learn how these nanoparticles impact the environment and natural systems, according to a university press release. Rice’s research team will be jointly headed by Vicki Colvin and Pedro Alvarez.

Colvin, the university’s Pitzer-Schlumberger Professor of Chemistry, also directs the Center for Biological and Environmental Nanotechnology. Alvarez is Rice’s George R. Brown Professor and chair of its Civil and Environmental Engineering Department. “Nanotechnology is full of initially promising qualities, but you have to consider the potential for environmental damage. For example, look at DDT. Hans Mueller won the Nobel Prize in 1948 for using DDT to fight malaria, but now we know the environmental damage impact,” the release quotes Alvarez as saying. According to the release, Alvarez and Colvin are “turning the tables” on conventional research because they are not only investigating the impact fullerenes have on the environment but also looking at the effect the environment has on these nanoparticles. “When you alter the structure of fullerenes via bacterial means, fungi or enzymes, you may also affect their toxicity or reactivity,” Alvarez says. Fullerenes comprised of 14C, a mildly radioactive carbon isotope, are being manufactured and tagged for the study, as they can be “tracked easily as they are altered by microbes, specifically fungi, and even monitored if they are completely broken down into carbon dioxide molecules,” the release explains.

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SCI Files Patent for Nano Enhanced Bamboo Friday, October 17, 2008 For Immediate Release– Survival Consultants Int’l. LLC has filed a patent on the methodology of growing nano enhanced bamboo. Bamboo is a world wide resource. The entire human race has become so entrenched in the uses of steel, copper, etc..(all building materials.) Our Patent defines the method of infusing specific nanites into bamboo. This will be distributed world wide, at world locale prevailing prices. SCI has also entered the BFI.ORG Challenge. This is the Buckminster Fuller Institutes competition. It matters not whether we win or not, it is more important to demonstrate the reality of SCI’s claims. Currently, SCI is culturing the above specified “Organic Nanite Enhanced Bamboo. Now known as “ONE BAMBOO.”

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Sands (left) and team member at reactor. (Credit: Purdue)

Experts at Purdue University say the United States could cut its total energy consumption and related carbon emissions by approximately 10 percent through the broad adoption of light-emitting diode technology. Known to be about four times more efficient than incandescent lights, one LED “negative” has prevented the technology’s widespread domestic use: prohibitive cost. LEDs are “at least 20 times” more expensive than incandescent and fluorescent bulbs, a Purdue press release says. This situation may be about to change, however, based on the same release’s announcement that Purdue researchers have developed a new technique that promises to lower the cost of producing LEDs.

As described in the journal Applied Physics Letters, the technique enables sapphire, a costly LED component, to be replaced with cheaper silicon. The technique owes its development to a research team headed by Timothy Sands, director of the Birck Nanotechnology Center at Purdue, the release says. In the release, Sands - a professor of materials, electrical and computer engineering - explains that sapphire more expensive than silicon and doesn’t offer silicon’s scalability. Another factor that adds to a sapphire LED’s costliness, Sands says, is that they “require a separate mirror-like collector to reflect light that ordinarily would be lost.” Costly collectors aren’t required in silicon-based LEDs, Sands says, because the Purdue team “metallized” the silicon substrate with a “built-in reflective layer of zirconium nitride.”

The team overcame zirconium nitride’s natural tendency to become unstable in the presence of silicon “by placing an insulating layer of alumininum nitride between the silicon substrate and the zirconium nitride,” he says. Sands stresses that this step is crucial to the success of his technique. In fact, he calls “placing a barrier on the silicon substrate to keep the zirconium nitride from reacting,” one of his work’s “main achievements.” The achievement was accomplished by utilizing reactive sputter deposition. This enabled Sands’ team to shower “the metals zirconium and aluminum with positively charged ions of argon gas in a vacuum chamber. The argon ions caused metal atoms to be ejected, and a reaction with nitrogen in the chamber resulted in the deposition of aluminum nitride and zirconium nitride onto the silicon surface.” The release then describes how Sands’ team deposited gallium nitride, the light-emitting ingredient in LEDs, onto the silicon via organometallic vapor phase epitaxy, performed in a reactor, at temperatures of about 1000°C. As the zirconium nitride, aluminum nitride and gallium nitride are deposited on the silicon, they self assemble into a crystalline structure that matches that of silicon. “We call this epitaxial growth, or the ordered arrangement of atoms on top of the substrate,” Sands says. “The atoms travel to the substrate, and they move around on the silicon until they find the right spot.” This crystalline formation, he says, is “critical” to the proper performance of silicon LEDs. “It all starts with silicon, which is a crystal, and you end up with gallium nitride that’s oriented with respect to the silicon through these intermediate layers of zirconium nitride and aluminum nitride,” he explains. “If you just deposited gallium nitride on a glass slide, for example, you wouldn’t get the ordered crystalline structure and the LED would not operate efficiently.” Sands says, because many LEDs can be manufacturered from a large silicon wafer, silicon-based LED technology also will enable manufacturers to “scale up” processing and, thereby, further reduce production costs. He notes similar economies of scale are “not possible using sapphire.”

One major obstacle remains before silicon-based LED technology will be ready for market, Sands admits. He says his team must find a way to prevent the gallium nitride layer from cracking while the silicon wafer cools after manufacturing.”The silicon wafer expands and contracts less than the gallium nitride,” Sands explains. “When you cool it down, the silicon does not contract as fast as the gallium nitride, and the gallium nitride tends to crack.” The Purdue professor is optimistic, however, and calls this challenge an “engineering issue” and “not a major show stopper.” For this reason, he believes affordable silicon LEDs will be “on the market within two years.”

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Circuit diagram (top frame) and optical images of a stretchable, "wavy" silicon ring oscillator circuit on a rubber substrate, in the "as fabricated" flat state (top micrograph) and in moderate and high states of biaxial compression (middle and bottom micrographs, respectively). Credit: Rogers.

Researchers led by John Rogers, a professor of materials science and engineering at the University of Illinois at Urbana-Champaign, have developed a new form of flexible, stretchable silicon integrated circuit. Not only can these new silicon circuits wrap around complex shapes, but they can do so without sacrificing electrical performance while stretching, compressing and folding is taking place, the researchers say. “The notion that silicon cannot be used in such applications because it is intrinsically brittle and rigid has been tossed out the window,” says Rogers, whose findings have been published in Science Magazine and posted on its  ScienceXpress website.”Through carefully optimized mechanical layouts and structural configurations, we can now use silicon in integrated circuits that are fully foldable and stretchable,” Rogers says. The development could lead to new types of sensors that can be integrated into artificial muscles, wearable health-monitoring systems or electrical devices that can wrap around aircraft wings and fuselages to monitor structural properties.

‘Wavy’ electronics

Rogers and his UI research team had previously reported the development of a one-dimensional, stretchable form of single-crystal silicon with micron-sized, wave-like geometries in 2005. He said then that the configuration allowed reversible stretching in one direction without significantly altering electrical properties, but only at the level of individual material elements and devices. Now Rogers and collaborators at the UI, Northwestern University, and the Institute of High Performance Computing in Singapore are reporting the extension of this earlier “wavy” development to two dimensions capable of yielding functional integrated circuit systems. Rogers reports constructing integrated circuits consisting of transistors, oscillators, logic gates and amplifiers and notes that these circuits exhibited extreme levels of bendability and stretchability, demonstrating electronic properties comparable to those of similar circuits built on conventional silicon wafers. “We’ve gone way beyond just isolated material elements and individual devices to complete, fully integrated circuits in a manner that is applicable to systems with nearly arbitrary levels of complexity,” Rogers says.

Methodology

To create fully stretchable integrated circuits, the researchers apply a sacrificial layer of polymer to a rigid carrier substrate, Rogers says. On top of the sacrificial layer, they deposit a very thin plastic coating that supported the integrated circuit. He notes that the circuit components are then crafted using conventional techniques for planar-device fabrication, along with printing methods for integrating aligned arrays of nanoribbons of single-crystal silicon. The researchers’ next step, according to Rogers, is to wash away the sacrificial polymer layer and bond the plastic coating and integrated circuit to a piece of pre-strained silicone rubber. Lastly, he says, they relieve the strain and - as the rubber springs back to its initial shape - apply compressive stresses to the circuit sheet. These stresses spontaneously lead to a complex pattern of buckling, creating a geometry that then allowed the circuit to be folded or stretched in different directions, giving it the ability to conform to complex shapes or to accommodate to the mechanical deformations that occur during use. “The wavy concept now incorporates optimized mechanical designs and diverse sets of materials, all integrated together in systems that involve spatially varying thicknesses and material types,” he explains, adding that the “overall buckling process yields wavy shapes that vary from place to place on the integrated circuit, in a complex but theoretically predictable fashion.”

Rogers stresses that attaining high degrees of mechanical flexibility or foldability is important to sustaining the wavy shapes. “The more robust the circuits are under bending, the more easily they will adopt the wavy shapes which, in turn, allow overall system stretchability,” he says. “For this purpose, we use ultra thin circuit sheets designed to locate the most fragile materials in a neutral plane, minimizing their exposure to mechanical strains during bending.” “We’re opening an engineering design space for electronics and optoelectronics that goes well beyond what planar configurations on semiconductor wafers can offer,” Rogers states, indicating that NSF and DOE are funding his research.

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