Archive for solar thin films
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Elsewhere on the materials front:
(Wall Street Journal) Aviation safety investigators are examining whether the formation of microscopic structures known as dendrites inside the Boeing Co. 787’s lithium-ion batteries played a role in twin incidents that prompted the fleet to be grounded nearly a month ago. The new information from the National Transportation Safety Board offers a glimpse into what could become an important line of inquiry for the investigation into a Jan. 7 battery fire aboard a Japan Airlines Co. Dreamliner parked in Boston. Investigators have so far said they know that fire was triggered by short circuits, but haven’t been able to determine the original cause of the incident, or of another one in which an overheating battery forced an All Nippon Airways Co. in Japan to make an emergency landing. Japanese investigators have said the battery in that ANA incident also experienced an internal short-circuit and a “thermal runaway.” Dendrites are tiny deposits of lithium resembling microscopic whiskers that can grow within the cells of a battery, potentially causing short circuits and significant heat and even fire. They are often a byproduct of rapid or uneven charging of lithium-ion batteries, according to experts.
Thanks to new research by an international team of researchers led by the DOE’s Argonne National Laboratory, physicists have developed new methods for controlling magnetic order in a particular class of materials known as “magnetoelectrics.” Magnetoelectrics get their name from the fact that their magnetic and electric properties are coupled to each other. Because this physical link potentially allows control of their magnetic behavior with an electrical signal or vice versa, scientists have taken a special interest in magnetoelectric materials. The Argonne-led team focused on europium-titanium oxide, which has a simple atomic structure that suited it especially well to the experiment. The titanium atom sits in the middle of a cage constructed of the europium and oxygen atoms. By first compressing the cage through growing a thin film of EuTiO3 on a similar crystal with a smaller lattice and then applying a voltage, the titanium shifts slightly, electrically polarizing the system, and more importantly, changing the magnetic order of the material.
At the Photonics West, the leading international fair for photonics, a spin-off of Karlsruhe Institute of Technology (KIT), presented the world’s fastest 3D printer of micro- and nanostructures. With this printer, the smallest three-dimensional objects, often smaller than the diameter of a human hair, can be manufactured with minimum time consumption and maximum resolution. The printer is based on a novel laser lithography method. “The success of Nanoscribe is an example of KIT’s excellent entrepreneurial culture and confirms our strategy of specifically supporting spin-offs. In this way, research results are transferred rapidly and sustainably to the market,” says Peter Fritz, KIT vice president for research and innovation. In early 2008, Nanoscribe was founded as the first spin-off of KIT and has since established itself as the world’s market and technology leader in the area of 3D laser lithography. With the new laser lithography method, printing speed is increased by factor of about 100. This increase in speed results from the use of a galvo mirror system, a technology that is also applied in laser show devices or scanning units of CD and DVD drives. Reflecting a laser beam off the rotating galvo mirrors facilitates rapid and precise laser focus positioning.
The Photovoltaics-Laboratory of EPFL’s Insitute of Microengineering is well known as a pioneer in the development of thin-film silicon solar cells, and as a precursor in the use of microcrystalline silicon as a photoactive material in thin-film silicon photovoltaic devices. A remarkable step was achieved by the team led by Fanny Meillaud and Matthieu Despeisse with a new world record efficiency of 10.7 percent for a single-junction microcrystalline silicon solar cell, independently confirmed at Fraunhofer Institute for Solar Energy Systems. Importantly, the employed processes can be up-scaled to the module level. While standard wafer-based crystalline silicon PV technology implements absorber layers with a thickness of about 180 micrometers for module conversion efficiency of 15 to 20 percent, 10.7% efficiency was reached here with only 1.8 micrometers of silicon material, i.e. 100 times less material than for conventional technologies, and with cell fabrication temperature never exceeding 200°C.
The contemporary industrial metabolism is not sustainable. Critical problems arise at both the input and the output side of the complex: Although affordable fossil fuels and mineral resources are declining, the waste products of the current production and consumption schemes (especially CO2 emissions, particulate air pollution, and radioactive residua) cause increasing environmental and social costs. Most challenges are associated with the incumbent energy economy that is unlikely to subsist. However, the crucial question is whether a swift transition to its sustainable alternative, based on renewable sources, can be achieved. The answer requires a deep analysis of the structural conditions responsible for the rigidity of the fossil-nuclear energy system. We argue that the resilience of the fossil-nuclear energy system results mainly from a dynamic lock-in pattern known in operations research as the “Success to the Successful” mode. The present way of generating, distributing, and consuming energy-the largest business on Earth-expands through a combination of factors such as the longevity of pertinent infrastructure, the information technology revolution, the growth of the global population, and even the recent financial crises: Renewable-energy industries evidently suffer more than the conventional-energy industries under recession conditions. Our analysis indicates that the rigidity of the existing energy economy would be reduced considerably by the assignment of unlimited liabilities to the shareholders.
Physicists at the University of Oldenburg, Germany, have now developed a new method for analysing the elastic characteristics of mechanical structures subjected to disturbances, akin to the turbulences affecting wind turbines. A significant percentage of the costs of wind energy is due to wind turbine failures, as components are weakened under turbulent air flow conditions and need to be replaced. The challenge for the team was to find a method for detecting fatigue in the wind turbines’ parts without having to remove each of the components and while the turbine is in operation. Until now, standard methods have relied on so-called spectral analysis, which looks at the different frequency response. But these measurements are distorted by the turbulent working conditions. As a result, these detection methods often only detect really major damages, like a crack that covers more than 50 percent of a blade. The authors used a simple experimental set-up of undamaged and damaged beam structures and exposed them to excitations containing an element of interfering vibrations, or noise, made by different turbulent wind conditions.
Tosoh SMD, a maker of the type of sputtering targets often used by photovoltaic manufacturers, says it has developed a new transparent conducting oxide target that can add a 1 percent gain to the solar conversion efficiencies of thin films.
According to a company news release, the new TCO targets (available in either indium tin oxide or aluminum zinc oxide flavors, with planar and rotary options) have been specially doped to have improved transparency and other optical properties. It says they “are highly transparent, especially in the visible to infrared range, and that feature high thermal stability, including under humid conditions … [and] enable the deposition of textured surfaces that feature enhanced light-trapping capability. Compared with thin films from conventional TCO targets, a single-junction thin film deposited by a Tosoh AZO TCO target in a silicon solar cell shows a one-point gain in conversion efficiency. Thin films, meanwhile, produced with Tosoh’s ITO TCO target achieve a similar gain in a copper indium gallium selenide-based solar cell.”
One CIGS expert seems to be happy with this. According to the release Makoto Konagai, of the Tokyo Institute of Technology, says that “this invention will contribute to achieving the goal of 18% energy conversion efficiency with a focus on low-cost and large-scale production.”
Just to clarify, I think Konagai’s reference to 18% conversion efficiency is to volume-produced CIGS, not lab tests. The NREL reached a CIGS thin-film efficiency mark of 19.9 % back in 2008, and has confirmed that at least one manufacturer has commercial units available that reach the 15.5 % conversion level.
Despite some nifty technical developments, interest in thin-film makers, especially in the United States, has waned as processing and manufacturing prices for traditional silicon PV units has continued to fall.
Tosoh is hoping to attract worldwide customers who are interested in lowering their overall cost per watt of production. I suspect some of the company’s timing of this announcement may be linked to Europe’s “Thin Film Solar Summit” that starts March 3 in Berlin.
Today the Administration announced that the DOE agreed to guarantee large loans for two separate solar power equipment makers, Abengoa Solar and Abound Solar Manufacturing.
The Abengoa project involves using a $1.45 billion loan to build a 250 MW concentrating solar facility in Solana, Ariz.
“Abengoa Solar estimates that the Solana project will employ approximately 1,600 workers during the construction phase of the project and create over 80 skilled permanent jobs for the plant’s operation. Over 70 percent of the components and products used for Solana will be made in the United States. Two assembly factories will be constructed on the Solana site, and as a result of Solana’s large need for mirrors (over 900,000), a new mirror manufacturing facility will be sited just outside of the Phoenix area, contributing additional direct investment and adding more jobs to Arizona’s economy.
The Abound Solar $400 million loan will accelerate the first manufacturing of cadmium-telluride thin-film solar panels. The panels will be made in Longmont, Colo. and the other in Tipton, Ind. The company says it is aiming for a 840 MW production level per year. The CdTe technology is the result of work done by Colorado State University, NREL and NSF.
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.