Posts Tagged ‘Oak Ridge National Laboratory’
Wednesday, October 21, 2015 @ 04:10 PM gHale
Advances in ultrathin films have made solar panels and semiconductor devices more efficient and less costly, and now there is a way to manufacture the films more easily, too.
Typically the films — used by organic bulk heterojunction solar cells (BHJs) to convert solar energy into electricity — end up created in a solution by mixing together conjugated polymers and fullerenes, soccer ball-like carbon molecules also known as buckyballs.
Next, the mixture is spin cast on a rotating substrate to ensure uniformity, then sent to post-processing to end up annealed. Annealing the material — heating then cooling it — reduces the material’s hardness while increasing its toughness, which makes it easier to work with.
Pliability makes BHJs more appealing than their more costly crystalline silicon counterparts, but the annealing process is time consuming, said researchers at the Department of Energy’s Oak Ridge National Laboratory (ORNL).
Now ORNL researchers said a simple solvent may make thermal annealing a thing of the past.
In a collaboration between ORNL’s Spallation Neutron Source (SNS) and the Center for Nanophase Materials Sciences (CNMS), postdoctoral researcher Nuradhika Herath led a team of neutron and materials scientists in a study of the morphology, or structure, of BHJ films.
“Optimizing a film’s morphology is the key to improving device performance,” Herath said. “What we want to find out is the relationship between the blend structures and photovoltaic performance.” Finding ways to tune the film’s morphology is as important as answering why certain film morphologies are more favorable than others, she added.
Researchers compared thermal annealing with a method that adds a small amount of solvent that aids in dissolving the fullerenes within the blend and helps to make the film’s structure more uniform.
The idea is to get the most uniform mixture of light absorbing molecules and fullerenes throughout the film. If the mixture is not uniform, clusters form and cause passing electrons to get absorbed, weakening the film’s ability to transport electrical current, which in turn decreases device performance.
Because the films are typically about 100 nanometers thick and the depth profile of the composition is highly complex, special instruments end up needed to measure the material’s morphology. For this, researchers turned to neutron scattering.
After mixing and spin casting two different samples at CNMS — one annealed, the other with solvent additive — the team put both films under the eye of SNS’s Magnetism Reflectometer (MR), beam line 4A. MR provided them with an accurate depiction of the structural profiles, which revealed exactly how the polymers and fullerenes were arranging themselves throughout both films. The difference between them was evident.
Whereas the annealed sample’s morphology clearly showed significant separation between the polymers and fullerenes, the sample containing the solvent additive was consistent throughout and performed better.
“The reason is that when we use a solvent instead of annealing, the sample dries very slowly, so there is enough time for the system to become fully optimized,” said MR Lead Instrument Scientist Valeria Lauter. “We see that additional annealing is not necessary because, in a sense, the system is already as perfect as it can be.”
Neutron reflectometry is a powerful method because it effectively makes many materials transparent, Lauter said. Instead of searching for the key that opens the metaphorical black box that prevents researchers from seeing a material’s atomic structure, neutrons simply go straight through it, giving researchers qualitative and quantitative information about their problem, she said.
Not only will the information obtained from neutrons help increase the efficiency of solar cells’ performance, but they will also streamline the process of manufacturing them. Using solvent additives to optimize the morphology of BHJ films could negate the need to invest more into a less effective process — a savings of time, money, and resources.
“In addition, optimization of photovoltaic properties provides information to manufacture solar cells with fully controlled morphology and device performance,” Herath said. “These findings will aid in developing ‘ideal’ photovoltaics, which gets us one step closer to producing commercialized devices.”
Friday, October 2, 2015 @ 03:10 PM gHale
Lock Data Solutions just licensed Data Diode technology from Oak Ridge National Laboratory designed to protect a company’s data from internal and external threats.
Data Diode, developed by ORNL’s Lawrence MacIntyre and Nate Paul, uses a defense-in-depth computer network strategy to create an environment in which an organization’s approved users can work freely inside an enclave of protected data but restricts file transfers outside the network.
Donald McGuire, chief executive at Lock Data Solutions, said the technology is a perfect fit for his company, noting his management team consists of professionals who have enjoyed commercial success with various technologies, including a secured wireless communication technology for the Navy. After picking up the license, he will bring to market the company’s Lock Data CounterX, a software suite that includes ORNL’s Data Diode technology.
“With the help of the technology being licensed today, we expect to create a sea change in the balance of power between those protecting data and those seeking to steal it,” McGuire said.
Armed with CounterX, an intruder who has penetrated the network can see the protected information but cannot download the actual data, McGuire said. And during the time it takes the intruder to search for a way around the obstacle, the network’s detection can locate and thwart the malicious intent of the intruder.
“Hackers are going to get in,” said Paul, a member of ORNL’s Cyber and Information Security Research group. “Employees can accidentally put confidential data at risk. The ORNL Data Diode addresses this problem by restricting important data from being copied out of network, thereby alleviating and alerting such specific and unauthorized activities.”
Paul said banks are vulnerable and have trusted consumer data including social security numbers, addresses and birth dates. A recent breach compromised data for 76 million households.
Lock Data Solutions LLC, located in New York City, is a technology company dedicated to bringing cutting edge solutions to cloud and network cyber security.
Monday, July 13, 2015 @ 07:07 PM gHale
Turning trees, grass, and other biomass into fuel for automobiles and airplanes is a costly and complex process, but it is not impossible.
The goal is to have cellulosic ethanol, an alcohol derived from plant sugars, as common and affordable at the gas station as gasoline.
That goal will end up accomplished after researchers unravel the tightly wound network of molecules — cellulose, hemicellulose, and lignin — that make up the cell wall of plants for easier biofuel processing.
Using high-performance computing, a group of researchers at Oak Ridge National Laboratory (ORNL) provided insight into how this might occur by simulating a well-established genetic modification to the lignin of an aspen tree in atomic-level detail.
The team’s conclusion: Hydrophobic, or water repelling, lignin binds less with hydrophilic, or water attracting, hemicelluloses. That knowledge points researchers toward a promising way to engineer better plants for biofuel.
The study is important because lignin, which is critical to the survival of plants in the wild, poses a problem for ethanol production, preventing enzymes from breaking down cellulose into simple sugars for fermentation.
Jeremy Smith, the director of ORNL’s Center for Molecular Biophysics and a Governor’s Chair at the University of Tennessee, led the project. His team’s simulation of a genetically modified lignin molecule linked to a hemicellulose molecule adds context to work conducted by researchers at the Department of Energy’s (DoE) BioEnergy Science Center (BESC), who demonstrated genetic modification of lignin can boost the amount of biofuel derived from plant material without compromising the structural integrity of the plant.
“BESC scientists created lots of different lignins randomly through genetic modification,” Smith said. “They found one that worked for them, but they wanted to know why it worked.”
To find the answer, Smith’s team turned to Titan, a 27-petaflop supercomputer at the Oak Ridge Leadership Computing Facility (OLCF).
Altering a Tree
Aspens are among the most widespread trees in North America, with a habitable zone that extends across the northern United States and Canada. As part of the genus Populus, which includes poplars and cottonwoods, they are fast growing and have the ability to adapt to diverse environments. Those are two qualities that make them prime candidates for cellulosic ethanol. Compared to traditional biofuel crops like corn and sugarcane, aspens require minimal care; they also can grow in areas where food crops cannot grow.
But the hardiness that allows aspens to thrive in nature makes them resistant to enzymatic breakdown during fermentation, an important step for converting biomass into ethanol. This problem can trace back to the molecular makeup of the plant cell wall, where lignin and hemicellulose bond to form a tangled mesh around cellulose.
Cellulose, a complex carbohydrate made up of glucose strands, comprises nearly half of all plant matter. It gives plants their structure, and it’s the critical substance needed to make cellulosic ethanol. To break down cellulose, one must get past lignin, a waste product of biofuel production that requires expensive treatments to isolate and remove. By throwing a wrench in the plant cell’s lignin assembly line, BESC scientists found they could boost biofuel production by 38 percent.
In nature, lignin adds strength to cellulosic fibers and protects the plant from predators and disease. Lignin molecules consist of multiple chemical groups made up of carbon, oxygen, and hydrogen assembled within the cell during a process called biosynthesis. During assembly, enzymes catalyze molecules into more complex units. By suppressing a key enzyme, Cinnamyl-alcohol dehydrogenase, BESC scientists created an “incomplete” lignin molecule. Instead of a hydrophilic alcohol group (an oxygen–hydrogen molecule bound to a hydrogen-saturated carbon atom), the final lignin polymer contained a hydrophobic aldehyde group (a carbon atom double-bonded to an oxygen atom).
“We wanted to see if there was a difference in the lignin–hemicellulose network if you substituted water-resisting aldehydes in the lignin for water-attracting alcohols,” said Loukas Petridis, an ORNL staff scientist. “Geneticists knew the modified plant could be more easily broken down, but they didn’t have an atomic-level explanation that a supercomputer like Titan can provide.”
Finding a Shortcut
Using a molecular dynamics code called NAMD, the team ran simulations of the wild lignin and the genetically modified lignin in a water cube, modeling the presence of the aldehydes by altering the partial charges of the oxygen and hydrogen atoms on the modified lignin’s allylic site.
The team simulated multiple runs of each 100,000-atom system for a few hundred nanoseconds, tracking the position of atoms in time increments of a femtosecond, or 1 thousand trillionth of a second. A comparison of the simulations showed weaker interaction between hemicellulose and the modified lignin than with wild lignin, suggesting that hydrophobic lignin interacts less with hydrophilic hemicellulose.
“From this you could make the testable assumption that making lignin more hydrophobic may lead to plants that are easier to deconstruct for biofuel,” Petridis said. “That’s the kind of rational insight we can provide using computer simulation.
“It took a decade of work to determine all the steps of lignin biosynthesis and find ways to manipulate genes. In the future, we hope to circumvent some of the work by continuing to test our models against experiment and making good suggestions about genes using supercomputers. That’s where the predictive power of molecular dynamic codes like NAMD comes in.”
“This modification is a bit more subtle and more complex to simulate,” Petridis said. “Finding out how good a predictive tool NAMD can be is the next step.”
Tuesday, January 20, 2015 @ 12:01 PM gHale
One of the issues behind detecting malware is how can you discover the bad software if you don’t even know it is bad software.
That issue can soon go away as a cyber security technology created at the Department of Energy’s (DoE) Oak Ridge National Laboratory (ORNL), can recognize malicious software even if the specific program has not been identified as a threat.
By computing and analyzing program behaviors associated with harmful intent, ORNL’s Hyperion technology can look inside an executable program to determine the software’s behavior without using its source code or running the program, said one of its inventors, Stacy Prowell of ORNL’s Cyber Warfare Research team.
“These behaviors can be automatically checked for known malicious operations as well as domain-specific problems,” Prowell said. “This technology helps detect vulnerabilities and can uncover malicious content before it has a chance to execute.”
Hyperion, which has been under development for a decade, offers more comprehensive scanning capabilities than existing cyber security methods.
“This approach is better than signature detection, which only searches for patterns of bytes,” Prowell said. “It’s easy for somebody to hide that — they can break it up and scatter it about the program so it won’t match any signature.”
Washington, D.C.-based R&K Cyber Solutions LLC (R&K) licensed Hyperion and is looking to go to market with the program this month.
“Software behavior computation is an emerging science and technology that will have a profound effect on malware analysis and software assurance,” said R&K Cyber Solutions Chief Executive Joseph Carter. “Computed behavior based on deep functional semantics is a much-needed cyber security approach that has not been previously available. Unlike current methods, behavior computation does not look at surface structure. Rather, it looks at deeper behavioral patterns.”
Carter said technology’s malware analysis capabilities can apply to multiple related cyber security problems, including software assurance in the absence of source code, hardware and software data exploitation and forensics, supply chain security analysis, anti-tamper analysis and potential first intrusion detection systems based on behavior semantics.
The licensed intellectual property includes two patent-pending technologies invented by Kirk Sayre of the Computational Sciences and Engineering Division and Richard Willems and former ORNL employee Stephen Lindberg of the Electrical and Electronics Systems Research Division. Others contributing to the technology were David Heise, Kelly Huffer, Logan Lamb, Mark Pleszkoch and Joel Reed of the Computational Sciences and Engineering Division.
Hyperion strengthens the cyber security of critical energy infrastructure by providing evidence of the secure functioning of energy delivery control system devices without requiring disclosure of the source code. This can advance resilient energy delivery systems designed, installed, operated and maintained to survive a cyber incident while sustaining critical functions.
Wednesday, November 12, 2014 @ 04:11 PM gHale
There are benefits for microgrids, small systems powered by renewables and energy storage devices, to break away from the main grid and working off its own island.
The benefit is microgrids can disconnect from larger utility grids and continue to provide power locally.
“If the microgrid is always connected to the main grid, what’s the point?” Department of Energy and Oak Ridge National Laboratory researcher Yan Xu asked. “If something goes wrong with the main grid, like a dramatic drop in voltage, for example, you may want to disconnect.”
The idea behind microgrids is to not only continue power to local units such as neighborhoods, hospitals or industrial parks, but also improve energy efficiency and reduce cost when connected to the main grid.
Researchers predict an energy future more like a marketplace in which utility customers with access to solar panels, battery packs, plug-in vehicles and other sources of distributed energy can compare energy prices, switch on the best deals and even sell back unused power to utility companies.
However, before interested consumers can plug into their own energy islands, researchers at facilities such as ORNL’s Distributed Energy Control and Communication (DECC) lab need to develop tools for controlling a reliable, safe and efficient microgrid.
To simulate real scenarios where energy would end up used on a microgrid, DECC houses a functional microgrid with a generation capacity of 250 kilowatts (kW) that seamlessly switches on and off the main grid.
This grid includes an energy storage system that generates 25kW of power and uses 50kW hours of energy built from second-use electric vehicle batteries, a 50kW- and a 13.5 kW-solar system and two smart inverters that serve as the grid interfaces for the distributed energy emulators. Programmable load banks that mimic equipment consuming energy on the grid can provide sudden large load changes and second-by-second energy profiles.
“A microgrid should run an automated optimization frequently, about every five to 10 minutes,” Xu said.
To optimize grid operations, microgrid generators, power flow controllers, switches and loads must end up outfitted with sensors and communication links that can provide real-time information to a central communications control.
“Microgrids are not widely deployed yet. Today, functional microgrids are in the R&D phase, and their communications are not standardized,” Xu said. “We want to standardize microgrid communications and systems so they are compatible with the main grid and each other.”
Now two years into the inception of ORNL’s microgrid project — “Complete System-Level Efficient and Interoperable Solution for Microgrid Integrated Controls,” or CSEISMIC — the microgrid test bed at DECC is functional and employs an algorithm developed at ORNL that directs automatic transition on and off ORNL’s main grid.
Xu said the next year will focus on getting the energy management system (EMS) running. The EMS will drive optimization by allowing microgrid components to fluctuate an operation based on parameters such as demand and cost.
“The EMS may, for instance, tell the PVs [solar cells] how much power to generate for the next five to 10 minutes based on the time of day and energy demand,” Xu said.
The CSEISMIC team has long-term goals of partnering with industries to conduct field demonstrations of standardized grid prototypes.
“As soon as microgrids are standardized and easy to integrate into the main grid,” Xu said, “we’ll start seeing them in areas with a high penetration of renewables and high energy prices.”
Friday, April 25, 2014 @ 11:04 AM gHale
Treating cadmium-telluride (CdTe) solar cell materials with cadmium-chloride improves their efficiency, but how that happens remained a mystery – until now.
After an atomic-scale examination of the thin-film solar cells, the light bulb has turned on and this decades-long debate about the materials’ photovoltaic efficiency increase after treatment appears solved.
A research team from led by the Department of Energy’s (DoE) Oak Ridge National Laboratory (ORNL), the University of Toledo and DoE’s National Renewable Energy Laboratory used electron microscopy and computational simulations to explore the physical origins of the unexplained treatment process.
Thin-film CdTe solar cells are a potential rival to silicon-based photovoltaic systems because of their theoretically low cost per power output and ease of fabrication. Their comparatively low historical efficiency in converting sunlight into energy, however, has limited the technology’s widespread use.
Research in the 1980s showed that treating CdTe thin films with cadmium-chloride significantly raises the cell’s efficiency, but scientists have been unable to determine the underlying causes. ORNL’s Chen Li, first author of a study on the subject, said the answer lay in investigating the material at an atomic level.
“We knew that chlorine was responsible for this magical effect, but we needed to find out where it went in the material’s structure,” Li said. “Only by understanding the structure can we understand what’s wrong in this solar cell — why the efficiency is not high enough, and how can we push it further.”
By comparing the solar cells before and after chlorine treatment, the researchers realized atom-scale grain boundaries ended up implicated in the enhanced performance. Grain boundaries are tiny defects that normally act as roadblocks to efficiency, because they inhibit carrier collection which greatly reduces the solar cell power.
Using state of the art electron microscopy techniques to study the thin films’ structure and chemical composition after treatment, the researchers found chlorine atoms replaced tellurium atoms within the grain boundaries. This atomic substitution creates local electric fields at the grain boundaries that boost the material’s photovoltaic performance instead of damaging it.
The research team’s finding, in addition to providing a long-awaited explanation, could help guide engineering of higher-efficiency CdTe solar cells. Controlling the grain boundary structure is a new direction that could help raise the cell efficiencies closer to the theoretical maximum of 32 percent light-to-energy conversion, Li said. Currently, the record CdTe cell efficiency is only 20.4 percent.
“We think that if all the grain boundaries in a thin film material could be aligned in same direction, it could improve cell efficiency even further,” Li said.