Wednesday, June 19, 2013
CONTENTS: 1Transparent Hybrid Electrode Advance, Purdue
2On the Fort Bliss Microgrid
3Li-ion Battery Optimization, PARC/ARPA-E
4Basic LED Research: In-clustering and LED Efficiency
5Grid Security Issues
Innovation could bring flexible solar cells, transistors, displays
Electron microscope images show a new material for transparent electrodes that might find uses in solar cells, flexible displays for computers and consumer electronics, and future "optoelectronic" circuits for sensors and information processing. The electrodes are made of silver nanowires covered with a material called graphene. At bottom is a model depicting the "co-percolating" network of graphene and silver nanowires. (Purdue University image/Birck Nanotechnology Center)
WEST LAFAYETTE, Ind. – Researchers have created a new type of transparent electrode that might find uses in solar cells, flexible displays for computers and consumer electronics and future "optoelectronic" circuits for sensors and information processing.
The electrode is made of silver nanowires covered with a material called graphene, an extremely thin layer of carbon. The hybrid material shows promise as a possible replacement for indium tin oxide, or ITO, used in transparent electrodes for touch-screen monitors, cell-phone displays and flat-screen televisions. Industry is seeking alternatives to ITO because of drawbacks: It is relatively expensive due to limited abundance of indium, and it is inflexible and degrades over time, becoming brittle and hindering performance.
"If you try to bend ITO it cracks and then stops functioning properly," said Purdue University doctoral student Suprem Das.
The hybrid material could represent a step toward innovations, including flexible solar cells and color monitors, flexible "heads-up" displays in car windshields and information displays on eyeglasses and visors.
"The key innovation is a material that is transparent, yet electrically conductive and flexible," said David Janes, a professor of electrical and computer engineering.
Research findings were detailed in a paper appearing online in April in the journal Advanced Functional Materials. The paper is available online athttp://onlinelibrary.wiley.com/doi/10.1002/adfm.201300124/full. It was authored by Das; visiting student Ruiyi Chen; graduate students Changwook Jeong and Mohammad Ryyan Khan; Janes and Muhammad A. Alam, a Purdue professor of electrical and computer engineering.
The hybrid concept was proposed in earlier publications by Purdue researchers, including a 2011 paper in the journal Nano Letters. The concept represents a general approach that could apply to many other materials, said Alam, who co-authored the Nano Letters paper.
"This is a beautiful illustration of how theory enables a fundamental new way to engineer material at the nanoscale and tailor its properties," he said.
Such hybrid structures could enable researchers to overcome the "electron-transport bottleneck" of extremely thin films, referred to as two-dimensional materials.
Combining graphene and silver nanowires in a hybrid material overcomes drawbacks of each material individually: the graphene and nanowires conduct electricity with too much resistance to be practical for transparent electrodes. Sheets of graphene are made of individual segments called grains, and resistance increases at the boundaries between these grains. Silver nanowires, on the other hand, have high resistance because they are randomly oriented like a jumble of toothpicks facing in different directions. This random orientation makes for poor contact between nanowires, resulting in high resistance.
"So neither is good for conducting electricity, but when you combine them in a hybrid structure, they are," Janes said.
The graphene is draped over the silver nanowires.
"It's like putting a sheet of cellophane over a bowl of noodles," Janes said. "The graphene wraps around the silver nanowires and stretches around them."
Findings show the material has a low "sheet resistance," or the electrical resistance in very thin layers of material, which is measured in units called "squares." At 22 ohms per square, it is five times better than ITO, which has a sheet resistance of 100 ohms per square.
Moreover, the hybrid structure was found to have little resistance change when bent, whereas ITO shows dramatic increases in resistance when bent.
"The generality of the theoretical concept underlying this experimental demonstration – namely 'percolation-doping' -- suggests that it is likely to apply to a broad range of other 2-D nanocrystaline material, including graphene," Alam said.
A patent application has been filed by Purdue's Office of Technology Commercialization.
Writer: Emil Venere, 765-494-4709, email@example.com
Sources: David Janes, 765-494-9263, firstname.lastname@example.org
Suprem Das, email@example.com
Muhammad A. Alam, 765-494-5988, firstname.lastname@example.org
Note to Journalists: A copy of the research paper is available by contacting Emil Venere, 765-494-4709, email@example.com.
Co-Percolating Graphene-Wrapped Silver Nanowire Network for High Performance, Highly Stable, Transparent Conducting Electrodes
Ruiyi Chen 1,4, Suprem R. Das 2,3, Changwook Jeong 1, Mohammad Ryyan Khan 1, David B. Janes 1,3,*, Muhammad A. Alam 1,*
1School of Electrical and Computer Engineering, Purdue University,
2Department of Physics, Purdue University
3Birck Nanotechnology Center, Purdue University
4 Department of Information Science and Electronic Engineering, Zhejiang University, Hangzhou, 310027, China
Email: David B. Janes (firstname.lastname@example.org), Muhammad A. Alam (email@example.com)
Transparent conducting electrodes (TCEs) require high transparency and low sheet resistance for applications in photovoltaics, photodetectors, flat panel displays, touch screen devices and imagers. Indium tin oxide (ITO), or other transparent conductive oxides, have typically been used, and provide a baseline sheet resistance (RS) vs. transparency (T) relationship. However, ITO is relatively expensive (due to limited abundance of Indium), brittle, unstable, and inflexible; moreover, ITO transparency drops rapidly for wavelengths above 1,000 nm. Motivated by a need for transparent conductors with comparable (or better) R Sat a given T, as well as flexible structures, several alternative material systems have been investigated. Single-layer graphene (SLG) or few-layer graphene provide sufficiently high transparency (≈97% per layer) to be a potential replacement for ITO. However, large-area synthesis approaches, including chemical vapor deposition (CVD), typically yield films with relatively high sheet resistance due to small grain sizes and high-resistance grain boundaries (HGBs). In this paper, we report a hybrid structure employing a CVD SLG film and a network of silver nanowires (AgNWs): RS as low as 22 Ω/□ (stabilized to 13 Ω/□ after 4 months) have been observed at high transparency (88% at λ = 550 nm) in hybrid structures employing relatively low-cost commercial graphene with a starting RSof 770 Ω/□. This sheet resistance is superior to typical reported values for ITO, comparable to the best reported TCEs employing graphene and/or random nanowire networks, and the film properties exhibit impressive stability under mechanical pressure, mechanical bending and over time. The design is inspired by the theory of a co-percolating network where conduction bottlenecks of a 2D film (e.g., SLG, MoS2) are circumvented by a 1D network (e.g., AgNWs, CNTs) and vice versa. The development of these high-performance hybrid structures provides a route towards robust, scalable and low-cost approaches for realizing high-performance TCE.
First-ever military microgrid demonstration marks next phase in the market
May 21, 2013 /Smart Grid News/http://www.smartgridnews.com/artman/publish/Delivery_Microgrids/First-ever-military-microgrid-demonstration-marks-next-phase-in-the-market-5774.html/?fpm#.UZ1Ps7V1w24
Quick Take: We've been telling you about the pending move to microgrids for years. And we've been saying that the U.S. military would lead the way. The military has all the usual reasons to be interested in microgrids, plus the additional motivator of national security. Microgrids offer energy self-sufficiency and a way to keep operating even if the main grid goes down.
We've previously tracked various experiments. Now the U.S. Army has officially launched its first grid-connected microgrid demonstration at Fort Bliss in Texas. You can read more about it in the press release below from contractor Lockheed Martin.
If successful, I predict this project will mark the beginning of a military microgrid growth phase. Give it a year or 18 months to prove out. At that point, I think you can expect bases everywhere to want their own version.
There's big money at stake. Jim Galvin, energy and water program manager for the Defense Department's Environmental Security Technology Certification Program, told the El Paso Timesthat the Pentagon spends $4 billion a year to power 300,000 buildings at 500 military installations across the world. That's a lot of microgrids. - By Jesse Berst
U.S. Army and Lockheed Martin commission microgrid at Fort Bliss
U.S. Army and Lockheed Martin (NYSE: LMT) officials commissioned the first U.S. Department of Defense (DoD) grid-tied microgrid integrating both renewable resources and energy storage during a ribbon cutting ceremony today at Fort Bliss, Texas. The project was funded by the DoD's Environmental Security Technology Certification Program.
The Fort Bliss grid-tied microgrid is designed to reduce overall greenhouse gas emissions and energy costs while providing the capability to operate independent of the electric utility grid when needed to provide energy security.
Events leading up to today's commissioning occurred in phases that involved installing hardware, upgrading software, bridging traditional and renewable energy generation sources and ensuring the microgrid operates efficiently. The program now enters its demonstration phase, which is slated to continue through July.
"We are excited to lead the Army in energy efficiency. This microgrid supports Fort Bliss' Environmental Campaign Plan, aimed at reducing our carbon footprint. This cost-effective project will incorporate renewable energy sources, lowering our electric output," said Major Joe Buccino, Fort Bliss spokesperson. "The tactical utility of this technology is its ability to allow us to operate off the grid. We are entering an age of emerging threats and cyber warfare. We are assuming an unacceptable measure of risk at fixed installations of extended power loss in the event of an attack on the fragile electric grid. This project represents the future of military energy security."
"The Fort Bliss microgrid will provide the DoD and other government and commercial organizations with the data and confidence necessary to transition microgrid technologies into wider scale use," said Jim Gribschaw, director of energy programs at Lockheed Martin. "Microgrids are the key to an energy efficient and secure future for sites such as defense installations, hospitals, universities, commercial businesses and industrial sites."
In 2010, Lockheed Martin received the contract to demonstrate an Intelligent Microgrid at the U.S. Army's Brigade Combat Team complex at Fort Bliss. The microgrid consists of onsite backup generation, a 120 kilowatt solar array, a 300 kilowatt energy storage system, utility grid interconnection and Lockheed Martin's Intelligent Microgrid Control System. The energy storage system is especially critical in lowering cost and maintaining a steady stream of energy. The system also stores energy to respond to high periods of energy demand and to produce reliable power.
Lockheed Martin completed Integrated Smart BEAR Power System (ISBPS) and Hybrid Intelligent Power (HI Power) microgrid system contracts last year. ISBPS equips the U.S. Air Force with lightweight, air-transportable microgrid assets to power a mobile air base. HI Power provides the U.S. Army an efficient, reliable and secure microgrid configuration to reduce fuel consumption at tactical operations centers.
Headquartered in Bethesda, Md., Lockheed Martin is a global security and aerospace company that employs about 118,000 people worldwide and is principally engaged in the research, design, development, manufacture, integration and sustainment of advanced technology systems, products and services. The Corporation's net sales for 2012 were $47.2 billion.
ARPA-E AWARDEE PARC AIMS TO CHANGE THE WAY WE THINK ABOUT BATTERIES
Wednesday, May 22, 2013/http://arpa-e.energy.gov/?q=arpa-e-news-item/arpa-e-awardee-parc-aims-change-way-we-think-about-batteries
We recently sat down with Dr. Eric Shrader, the principal investigator of PARC’s battery co-extrusion project, to talk innovation, reforming the electric vehicle (EV) industry, and changing the way we think about batteries.
Tell us a little about your background and how you arrived at PARC.
I spent most of my career working in printing research. I started work at SRI International, did a lot of work in inkjet printing, founded a startup company during the dot-com boom, and then came to PARC at about the time PARC was spinning out of Xerox. At that point, PARC was ready to look at other applications for its printing technology. So there was a lot of exciting technology and know-how at PARC, and we were poised to be able to use that technology and know-how for other things like this project.
Your project aims to reduce manufacturing costs and improve overall battery performance for Li-ion batteries. How will this innovative design increase the battery’s overall energy storage?
First, it’s important to step back and think a little bit about how batteries are optimized now. There’s always a tradeoff in battery design between energy performance and power performance. We’re developing a design that gives you another lever to adjust those two parameters.
Traditionally, Li-Ion manufacturers make each layer of the battery separately and then integrate the layers together. PARC is working to manufacture a Li-ion battery by printing each layer simultaneously into an integrated battery, streamlining the manufacturing process.
How could this printing process transform the industry? Do you foresee it being used in other energy applications?
I think this technology is transformative because it leverages all of the improvements that have been made in battery manufacturing thus far. Most of the research in batteries today centers on chemistry and materials, so there has been a lot of improvement in both the actual chemistry and the processing of the materials to make them more efficient. This project operates on top of all those advancements; that’s why it’s a very broad-based, transformative idea. It doesn’t just apply to a particular lithium chemistry that you might use in automobiles. As far as other applications, we’ve already used the technology in solar, and we’ve thought about using it for fuel cells as well.
What are the biggest challenges of this project, and how are you trying to overcome them?
One of the biggest challenges is in scaling, so we think a lot about how we get from what we’re able to do on the lab scale to making it viable at the commercial scale. We’re also aiming at cost reduction: by printing all three battery layers at once, we lower the energy yield loss and the amount of material wasted.
Can you talk about why you thought that this project would be perfect for a partnership with ARPA-E?
Well, we already had some of the pieces in place for co-extrusion in batteries, and had been talking to commercial partners about them, but they weren’t really willing to undertake the additional risk associated with the project. I think the ARPA-E partnership is perfect because it will probably de-risk it enough for commercial partners to say “we get it, it does really work.”
You touched on this a little, but what would be your ideal next step or end goal for this project?
One of the nice things about the PARC/ARPA-E partnership is that PARC’s business model is all about getting things out into the world. It fits very well into our business model to partner with companies that are already producing batteries, or investors who want to start companies producing batteries. Our ideal next step for this project is to license this to a battery manufacturer in the U.S. to produce EV batteries, because that’s where the real payoff is for us. This is a really good opportunity for us to revitalize the battery industry in the US: the rest of the world is somewhat ahead of us in producing batteries for other applications, but as far as EV batteries go, the field is still open enough that there are a lot of ways for US companies to compete and we’re trying to help make that happen.
May 22nd, 2013/http://www.nanowerk.com/news2/newsid=30616.php
Atomic-scale investigations solve key puzzle of LED efficiency
(Nanowerk News) From the high-resolution glow of flat screen televisions to light bulbs that last for years, light-emitting diodes (LEDs) continue to transform technology. The celebrated efficiency and versatility of LEDs—and other solid-state technologies including laser diodes and solar photovoltaics—make them increasingly popular. Their full potential, however, remains untapped, in part because the semiconductor alloys that make these devices work continue to puzzle scientists.
A contentious controversy surrounds the high intensity of one leading LED semiconductor—indium gallium nitride (InGaN)—with experts split on whether or not indium-rich clusters within the material provide the LED's remarkable efficiency. Now, researchers from the Massachusetts Institute of Technology (MIT) and the U.S. Department of Energy's (DOE) Brookhaven National Laboratory have demonstrated definitively that clustering is not the source. The results – published online May 16 in Applied Physics Letters ("Revisiting the “In-clustering” question in InGaN through the use of aberration-corrected electron microscopy below the knock-on threshold") – advance fundamental understanding of LED technology and open new research pathways.
"This discovery helps solve a significant mystery in the field of LED research and demonstrates breakthrough experimental techniques that can advance other sensitive and cutting-edge electronics," said Silvija Gradecak, the Thomas Lord Associate Professor of Materials Science and Engineering at MIT and a coauthor on the study. "The work brings us closer to truly mastering solid-state technologies that could supply light and energy with unprecedented efficiency."
These images of the InGaN samples—produced by CFN's low-voltage scanning transmission electron microscope—reveal a lack of structural changes over time. After 16 minutes of scanning, no damage or decomposition is visible, and the higher magnification (c) exhibits none of the clustering previously theorized to be central to LED efficiency.
Building a Better Bulb
Incandescent lights—the classic bulbs that use glowing wires of tungsten or other metals—convert only about five percent of their energy into visible light, with the rest lost as heat. Fluorescent lights push that efficiency up to about 20 percent, still wasting 80 percent of the electricity needed to keep homes and businesses bright. In both of these instances, light is only the byproduct of heat-generating reactions rather than the principal effect, making the technology inherently inefficient.
"Solid-state lights convert electric current directly into photons," said Eric Stach, leader of the Electron Microscopy Group at Brookhaven Lab's Center for Functional Nanomaterials (CFN) and a co-author on the study. "LED bulbs use semiconductors to generate light in a process called electroluminescence. The efficiency of this process could, in theory, be nearly perfect, but the experimental realization has not reached those levels. That disconnect helped motivate this study."
For this study, the scientists looked at the LED compound InGaN (pronounced in-gan), which is particularly promising for practical applications. InGaN alloys contain dislocations—structural imperfections that could inhibit electricity flow and light production—but somehow the alloy performs exceptionally well. To understand the light-emitting reactions, physicists needed to understand what was happening on the atomic scale. After researchers started to investigate, however, not everyone reached the same conclusions.
"Years ago, a team of researchers used electron microscopes to examine InGaN samples, and they identified a surprising phenomenon—the material appeared to be spontaneously decomposing and forming these isolated indium-rich clusters," Stach said. "This behavior could explain the efficient light emission, as the clusters might help electrons avoid the structural problems in the InGaN. But then things became really interesting when another group proposed that the electron microscope itself caused that clustering decomposition. We had a real divide in the semiconductor field."
Rather than using light to examine materials, electron microscopes bombard samples with finely tuned beams of electrons and detect their interactions when they pass through a sample to reveal atomic structures. To achieve high enough resolution to examine the InGaN alloys, the electron microscopes used in the older experiments needed high-voltage beams. The controversy revolved around whether or not the experiment itself produced the clusters, rather than discovering the mechanism behind efficient light emission.
"The state-of-the-art instruments available at Brookhaven Lab's CFN changed the way we could test these promising materials," Gradecak said. "The CFN's aberration-corrected scanning transmission electron microscope (STEM) opened a new and non-destructive window into the LED samples. For the first time, we could get Ångstrom-level details—that's one tenth of one nanometer—without the risk of the device affecting the sample."
The researchers combined the leading STEM techniques with high-resolution electron energy loss spectroscopy (EELS), which measured the energy lost by electrons as they passed through the sample. Post-doctoral researchers Kamal Baloch of MIT—the lead author of the study—and Aaron Johnston-Peck of CFN actually applied these imaging techniques to the same samples that first launched the controversy over clustering, helping further settle the issue.
"We found that the indium-rich clusters do not actually exist in these samples, even though they remain efficient light emitters," Baloch said. "While clustering may still occur in other samples, which may be prepared in different ways, the important point is that we've established a foolproof method for investigating InGaN materials. We can use these non-destructive imaging techniques to explore the fundamental relationship between cluster formation and light emission to help unlock the secrets of this amazing alloy."
Beyond the advanced imaging instruments, researchers used the expertise of Brookhaven Lab physicist Kim Kisslinger, who specializes in nanoscale sample preparation. The InGaN samples were reduced to a thickness of just 20 nanometers, an essential step in priming the materials for STEM and EELS experimentation. The samples were also painstakingly cleaned and polished to eliminate artifacts that might impact image resolution.
The research was supported by the Center for Excitonics, an Energy Frontier Research Center funded by the U.S. Department of Energy's Office of Science. The work at Brookhaven Lab's Center for Functional Nanomaterials was also supported by DOE's Office of Science, with additional work carried out at the MIT Center for Materials Science Engineering.
"The Center for Excitonics gave us the freedom and funding to look at this fundamental question, knowing that these explorations will ultimately push the limits of LED technology," Gradecak said. "This was a strong collaboration between MIT and Brookhaven's CFN, demonstrating the concentration of expertise and instrumentation that really pushes science and technology forward."
Source: Brookhaven National Laboratory
Power company targeted by 10,000 cyberattacks per month
Electric grid is under daily assault, Congressional report finds.
by Jon Brodkin - May 22 2013/Ars Technica/http://arstechnica.com/information-technology/2013/05/power-company-targeted-by-10000-cyber-attacks-per-month/
A Congressional survey of utility companies has revealed that the country's electric grid faces constant assault from hackers, with one power company reporting a whopping 10,000 attempted cyberattacks per month.
US Reps. Edward Markey (D-MA) and Henry Waxman (D-CA) sent 15 questions to more than 150 utilities and received replies from 112 of them. Only 53 of those actually answered all the questions—the others provided incomplete responses or only "a few paragraphs containing non-specific information" without answering any of the questions.
Results from those who did answer show utilities are under continuous assault:
The electric grid is the target of numerous and daily cyberattacks.
· More than a dozen utilities reported “daily,” “constant,” or “frequent” attempted cyberattacks ranging from phishing to malware infection to unfriendly probes.
· One utility reported that it was the target of approximately 10,000 attempted cyberattacks each month.
· More than one public power provider reported being under a “constant state of ‘attack’ from malware and entities seeking to gain access to internal systems.”
· A Northeastern power provider said that it was “under constant cyber attack from cyber criminals including malware and the general threat from the Internet…”
· A Midwestern power provider said that it was “subject to ongoing malicious cyber and physical activity. For example, we see probes on our network to look for vulnerabilities in our systems and applications on a daily basis. Much of this activity is automated and dynamic in nature—able to adapt to what is discovered during its probing process.”
The good news is that none of these utilities reported damage to any of their computer systems. "However, there did not appear to be a uniform process for reporting attempted cyberattacks to the authorities; most respondents indicated that they follow standard requirements for reporting attacks to state and federal authorities, did not describe the circumstances under which these requirements would be triggered, but largely indicated that the incidents they experienced did not rise to reportable levels," Markey and Waxman wrote.
The utilities are a mix of investor-owned entities, municipal power companies, rural electric cooperatives, and "federal entities that own major pieces of the bulk power system."
Reps want Congress to boost grid security
Markey and Waxman revealed the results of their survey yesterday in a report titled "Electric Grid Vulnerability: Industry Responses Reveal Security Gaps." The report examines threats from both cyberattacks and geomagnetic storms. Markey and Waxman noted that "numerous security experts have called on Congress to provide a federal entity with the necessary authority to ensure that the grid is protected from potential cyber-attacks and geomagnetic storms. Despite these calls for action, Congress has not provided any governmental entity with that necessary authority."
The survey found that nearly all responding utilities comply with mandatory standards issued by the North American Electric Reliability Corporation (NERC), but most haven't implemented NERC's voluntary recommendations. The report states:
For example, NERC has established both mandatory standards and voluntary measures to protect against the computer worm known as Stuxnet. Of those that responded, 91% of IOUs [investor-owned utilities], 83% of municipally or cooperatively owned utilities, and 80% of federal entities that own major pieces of the bulk power system reported compliance with the Stuxnet mandatory standards. By contrast, of those that responded to a separate question regarding compliance with voluntary Stuxnet measures, only 21% of IOUs, 44% of municipally or cooperatively owned utilities, and 62.5% of federal entities reported compliance.
Markey and Waxman also found cause for concern in the power companies' readiness for geomagnetic storms. "Most utilities have not taken concrete steps to reduce the vulnerability of the grid to geomagnetic storms and it is unclear whether the number of available spare transformers is adequate," they wrote. "Only 12 of 36 (33%) responding IOUs, 5 of 25 (20%) responding municipally or cooperatively owned utilities, and 2 of 8 (25%) responding federal entities stated that they have taken specific mitigation measures to protect against or respond to geomagnetic storms. Most utilities do not own spare transformers."
There are numerous types of cyberattacks targeting the utility industry. Two US power generation facilities were infected by malware spread by USB drives plugged into critical systems used to control power equipment, we noted in a story in January. Last year, a provider of software that helps the energy industry remotely monitor and control sensitive equipment was targeted by "a sophisticated hacker attack that managed to penetrate its internal defenses."
Markey and Waxman noted that "Cyberattacks can create instant effects at very low cost and are very difficult to positively attribute back to the attacker. It has been reported that actors based in China, Russia, and Iran have conducted cyber probes of US grid systems, and that cyberattacks have been conducted against critical infrastructure in other countries."
In 2010, Markey and US Rep. Fred Upton (R-MI) introduced the GRID Act to boost security of the electric grid. It passed the House but not the Senate. The bill would have authorized the Federal Energy Regulatory Commission "to issue orders for emergency measures to protect the reliability of either the bulk-power system or the defense critical electric infrastructure whenever the President issues a written directive or determination identifying an imminent grid security threat." Markey is still pushing for passage of the act.
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