Researchers Discover a Simple Way to Increase Solar Cell Efficiency

January 3, 2014

By modifying the molecular structure of a polymer used in solar cells, an international team of researchers has increased solar efficiency by more than thirty percent.

Researchers from North Carolina State University and the Chinese Academy of Sciences have found an easy way to modify the molecular structure of a polymer commonly used in solar cells. Their modification can increase solar cell efficiency by more than 30 percent.

Polymer-based solar cells have two domains, consisting of an electron acceptor and an electron donor material. Excitons are the energy particles created by solar cells when light is absorbed. In order to be harnessed effectively as an energy source, excitons must be able to travel quickly to the interface of the donor and acceptor domains and retain as much of the light’s energy as possible.

One way to increase solar cell efficiency is to adjust the difference between the highest occupied molecular orbit (HOMO) of the acceptor and lowest unoccupied molecular orbit (LUMO) levels of the polymer so that the exciton can be harvested with minimal loss. One of the most common ways to accomplish this is by adding a fluorine atom to the polymer’s molecular backbone, a difficult, multi-step process that can increase the solar cell’s performance, but has considerable material fabrication costs.

A team of chemists led by Jianhui Hou from the Chinese Academy of Sciences created a polymer known as PBT-OP from two commercially available monomers and one easily synthesized monomer. Wei Ma, a post-doctoral physics researcher from NC State and corresponding author on a paper describing the research, conducted the X-ray analysis of the polymer’s structure and the donor:acceptor morphology.

PBT-OP was not only easier to make than other commonly used polymers, but a simple manipulation of its chemical structure gave it a lower HOMO level than had been seen in other polymers with the same molecular backbone. PBT-OP showed an open circuit voltage (the voltage available from a solar cell) value of 0.78 volts, a 36 percent increase over the ~ 0.6 volt average from similar polymers.

According to NC State physicist and co-author Harald Ade, the team’s approach has several advantages. “The possible drawback in changing the molecular structure of these materials is that you may enhance one aspect of the solar cell but inadvertently create unintended consequences in devices that defeat the initial intent,” he says. “In this case, we have found a chemically easy way to change the electronic structure and enhance device efficiency by capturing a lager fraction of the light’s energy, without changing the material’s ability to absorb, create and transport energy.”

The researchers’ findings appear in Advanced Materials. The research was funded by the U.S. Department of Energy, Office of Science, Basic Energy Science and the Chinese Ministry of Science and Technology. Dr. Maojie Zhang synthesized the polymers; Xia Guo,Shaoqing Zhang and Lijun Huo from the Chinese Academy of Sciences also contributed to the work.

Publication: Maojie Zhang, et al., “An Easy and Effective Method to Modulate Molecular Energy Level of the Polymer Based on Benzodithiophene for the Application in Polymer Solar Cells,” Advanced Matererilas, 2013; doi: 10.1002/adma.201304631
Source: Tracey Peake, North Carolina State University
Image: Maojie Zhang, et al. doi: 10.1002/adma.201304631

To calculate long-term conservation pay off, factor in people

          

This is a village in Wolong, Sichuan Province, China, where many residents are paid for their actions which help with conservation efforts. Credit: Jianguo

Paying people to protect their natural environment is a popular conservation tool around the world – but figure out that return on investment, for both people and nature, is a thorny problem, especially since such efforts typically stretch on for years.

"Short attention-span worlds with long attention-span problems" is how Xiaodong Chen, a former Michigan State University doctoral student now on faculty at the University of North Carolina-Chapel Hill sums it up.

Chen, with his adviser Jianguo "Jack" Liu, director of the MSU Center for Systems Integration and Sustainability (CSIS) and others, have developed a new way to evaluate and model the long-term effectiveness of conservation investments. Their achievement is not only factoring in ecological gains – like, more trees growing – but also putting the actions and reactions of people into the equation.

The paper, Assessing the Effectiveness of Payments for Ecosystem Services: an Agent-Based Modeling Approach, appears in this week's online edition of Ecology and Society.

The paper examines payments for ecosystem services – the practice of paying people to perform tasks or engage in practices that aid conservation. The authors examined one of China's most sweeping – the National Forest Conservation Program, in which residents in Wolong Nature Reserve are paid to stop chopping down trees for timber and fuel wood.

Chen explained they tapped into both social data and environmental information to be able to create a computer model to simulate how the policy would fare over many years in a variety of scenarios.
Studies documenting results on land cover change and panda habitat dynamics were merged with studies revealing how people were likely to behave if new households were formed or incentives for conservation activities were varied.

"Usually studies are developed in either the social sciences or the natural sciences, and the importance of the other perspectives are not built into scientific exploration," Chen said. "We were able to develop this kind of simulation because of collaborative interdisciplinary research - by putting people with different backgrounds together."

He also said the model's ability to run scenarios about how policy could work over decades is crucial because many goals of conservation, like restoring wildlife habitat, can take decades. In the meantime, the actions of individuals living in the area can change.

Explore further: Tallying the wins and losses of policy

Journal reference: Ecology and Society
Provided by Michigan State University

Read more at: http://phys.org/news/2014-01-long-term-factor-people.html#jCp

Energy is the Key to Solving Income Inequality

Posted on January 29, 2014 at 5:48 pm by David Holt in Electricity, featured, Jobs & Career Advice, People, Politics/Policy   

When exploring solutions to income inequality policy makers pay close attention to the costs. The cost of healthcare. The cost of food. The cost of child care. The cost of housing.

What about the cost of energy?

According to the Bureau of Labor Statistics, in 2012 the average U.S. family spent over $4,600 or about 9 percent of their budget to heat and power their homes and fuel their vehicles. Families in the bottom fifth of income earners spent nearly 33 percent more of their budget on energy costs than average $2,500 a year or 12% of their annual budget.

Reference the chart to the left and you will find that low-income families spend two and half times more on energy than on health services. Unlike food and housing, consumers cannot shop around for the lowest cost energy. Bargains can be found in the supermarket, but, prices at the pump do not vary from one station to the next. Conservation similarly is not an option when it’s a choice between driving to work or saving a gallon of gasoline.

A solution to remedying income inequality is tackling rising energy costs. The U.S. Energy Information Administration projects the price of electricity will rise 13.6 percent and the price of gasoline by 15.7 percent from now until 2040. Rising global demand, aging and insufficient energy infrastructure and restrictive government policies all play a role in increasing costs.President Obama has the ability to reverse this trend and lessen the blow to all consumers.

Take the shale gas boom for example. Increasing access to private and state lands and sound state regulatory programs have boosted production of natural gas and led to a significant lowering of prices. IHS CERA predicted that the shale revolution lifted household income by more than $1,200 in 2012 through lower energy costs, more job opportunities and greater federal and state tax revenues.

Policy makers should promote responsible energy development with the knowledge that it will have a positive affect on even the most vulnerable. The president has the power to act. Permitting energy infrastructure – including the Keystone XL Pipeline, opening new offshore areas to oil and natural gas development, and finalizing the nuclear waste confidence rulemaking, could transform the energy economy.

If policy makers want to take meaningful action to help our nation’s low income families, they must pursue actions that help lower – not raise – the cost of energy.

What Actually Happens While You Sleep and How It Affects Your Every Waking Moment

by Maria Popova

“We are living in an age when sleep is more comfortable than ever and yet more elusive.”

The Ancient Greeks believed that one fell asleep when the brain filled with blood and awakened once it drained back out. Nineteenth-century philosophers contended that sleep happened when the brain was emptied of ambitions and stimulating thoughts. “If sleep doesn’t serve an absolutely vital function, it is the greatest mistake evolution ever made,” biologist Allan Rechtschaffen once remarked. Even today, sleep remains one of the most poorly understood human biological functions, despite some recent strides in understanding the “social jetlag” of our internal clocks and the relationship between dreaming and depression. In Dreamland: Adventures in the Strange Science of Sleep (public library), journalist David K. Randall — who stumbled upon the idea after crashing violently into a wall while sleepwalking — explores “the largest overlooked part of your life and how it affects you even if you don’t have a sleep problem.” From gender differences to how come some people snore and others don’t to why we dream, he dives deep into this mysterious third of human existence to illuminate what happens when night falls and how it impacts every aspect of our days.

Most of us will spend a full third of our lives asleep, and yet we don’t have the faintest idea of what it does for our bodies and our brains. Research labs offer surprisingly few answers. Sleep is one of the dirty little secrets of science. My neurologist wasn’t kidding when he said there was a lot that we don’t know about sleep, starting with the most obvious question of all — why we, and every other animal, need to sleep in the first place.

But before we get too anthropocentrically arrogant in our assumptions, it turns out the quantitative requirement of sleep isn’t correlated with how high up the evolutionary chain an organism is:

Lions and gerbils sleep about thirteen hours a day. Tigers and squirrels nod off for about fifteen hours. At the other end of the spectrum, elephants typically sleep three and a half hours at a time, which seems lavish compared to the hour and a half of shut-eye that the average giraffe gets each night.

Humans need roughly one hour of sleep for every two hours they are awake, and the body innately knows when this ratio becomes out of whack. Each hour of missed sleep one night will result in deeper sleep the next, until the body’s sleep debt is wiped clean.

What, then, happens as we doze off, exactly? Like all science, our understanding of sleep seems to be a constant “revision in progress”:

Despite taking up so much of life, sleep is one of the youngest fields of science. Until the middle of the twentieth century, scientists thought that sleep was an unchanging condition during which time the brain was quiet. The discovery of rapid eye movements in the 1950s upended that. Researchers then realized that sleep is made up of five distinct stages that the body cycles through over roughly ninety-minute periods. The first is so light that if you wake up from it, you might not realize that you have been sleeping. The second is marked by the appearance of sleep-specific brain waves that last only a few seconds at a time. If you reach this point in the cycle, you will know you have been sleeping when you wake up. This stage marks the last drop before your brain takes a long ride away from consciousness. Stages three and four are considered deep sleep. In three, the brain sends out long, rhythmic bursts called delta waves. Stage four is known as slow-wave sleep for the speed of its accompanying brain waves. The deepest form of sleep, this is the farthest that your brain travels from conscious thought. If you are woken up while in stage four, you will be disoriented, unable to answer basic questions, and want nothing more than to go back to sleep, a condition that researchers call sleep drunkenness. The final stage is REM sleep, so named because of the rapid movements of your eyes dancing against your eyelids. In this stage of sleep, the brain is as active as it is when it is awake. This is when most dreams occur.

(Recall the role of REM sleep in regulating negative emotions.)

Randall’s most urgent point, however, echoes what we’ve already heard from German chronobiologist Till Roenneberg, who studies internal time — in our blind lust for the “luxuries” of modern life, with all its 24-hour news cycles, artificial lighting on demand, and expectations of round-the-clock telecommunications availability, we’ve thrown ourselves into a kind of circadian schizophrenia:

We are living in an age when sleep is more comfortable than ever and yet more elusive. Even the worst dorm-room mattress in America is luxurious compared to sleeping arrangements that were common not long ago. During the Victorian era, for instance, laborers living in workhouses slept sitting on benches, with their arms dangling over a taut rope in front of them. They paid for this privilege, implying that it was better than the alternatives. Families up to the time of the Industrial Revolution engaged in the nightly ritual of checking for rats and mites burrowing in the one shared bedroom. Modernity brought about a drastic improvement in living standards, but with it came electric lights, television, and other kinds of entertainment that have thrown our sleep patterns into chaos.

Work has morphed into a twenty-four-hour fact of life, bringing its own set of standards and expectations when it comes to sleep … Sleep is ingrained in our cultural ethos as something that can be put off, dosed with coffee, or ignored. And yet maintaining a healthy sleep schedule is now thought of as one of the best forms of preventative medicine.

Reflecting on his findings, Randall marvels:

As I spent more time investigating the science of sleep, I began to understand that these strange hours of the night underpin nearly every moment of our lives.

Indeed, Dreamland goes on to explore how sleep — its mechanisms, its absence, its cultural norms — affects everyone from police officers and truck drivers to artists and entrepreneurs, permeating everything from our decision-making to our emotional intelligence.

Final Keystone XL report: No major boost in greenhouse gasses

By Deena Winter  /   January 31, 2014           

                        

AP photo

YOUR TURN: Now it’s up to Secretary of State John Kerry to make a recommendation to President Obama on the fate of the proposed Keystone XL pipeline.

By Deena Winter | Nebraska Watchdog
Updated 4:05 p.m.

LINCOLN, Neb. — The U.S. State Department’s final environmental review of the proposed Keystone XL oil pipeline mirrors earlier conclusions that the pipeline wouldn’t significantly contribute to greenhouse gas emissions.

The report reiterated last year’s draft report conclusion that the pipeline is unlikely to significantly impact the rate of extraction of oil sands or the continued demand for heavy crude oil in the U.S.
Now that the State Department’s environmental review of TransCanada’s application for a federal permit to build the pipeline is complete, a 90-day review by various federal agencies will commence to determine whether the pipeline is in the national interest, since it crosses a national border. The final decision is expected to be made by Secretary of State John Kerry and President Obama.

Canadian pipeline company TransCanada first applied for permission to build the pipeline in late 2008, but it ran into a wall of opposition in Nebraska. Nebraska pipeline fighters have taken part in and helped organize protests from the governor’s mansion to Washington, D.C., even as most of the Republican statewide public officials have pushed for approval.

Courtesy photo

REPORT: The U.S. State Department released its final environmental report Friday on the proposed Keystone XL oil pipeline that would cross America. The report found the pipeline would not significantly affect greenhouse gas emissions.

The Keystone XL pipeline would bisect Nebraska, with nearly 200 miles of pipe buried in a dozen counties. A grassroots group called Bold Nebraska has battled against a foreign company having the power to take land from landowners and possible contamination of the massive Ogallala Aquifer by oil spills.

Pipeline opponents successfully lobbied Obama to reject TransCanada’s initial application in late 2011 and forced the company to reroute the pipeline around the ecologically fragile Sandhills. That’s the route reviewed in the latest State Department reports.

The new report noted that most pipeline spills are small: of the 1,692 incidents between 2002 and 2012, 79 percent were small (up to 2,100 gallons) and just 4 percent were large spills where the oil would migrate away from the release site. It also said modeling indicates “aquifer characteristics would inhibit the spread of released oil, and impacts from a release on water quality would be limited.”

Pipeline opponents in Nebraska have questioned why TransCanada didn’t build the pipeline parallel to its existing Keystone One pipeline that crosses eastern Nebraska, away from the Sandhills and aquifer. The report noted this, but concluded it wasn’t a reasonable alternative because it wouldn’t meet Keystone’s contractual obligations to transport 100,000 barrels per day of crude oil from the Bakken oil play in North Dakota. Also, the corridor would be longer, increasing the risk of spills.

The proposed pipeline has put Obama in a difficult position where he must decide whether to live up to his promises to combat climate change or appease labor unions that generally support the pipeline and jobs it would bring. Obama said last year the pipeline should only be built if it doesn’t increase carbon emissions.

Russ Girling, TransCanada president and chief executive officer, told reporters Friday that while opponents will continue to make noise, “The science continues to show that this pipeline can and will be built safety.”

“This pipeline certainly is in the national interest of the United States,” he said.

Bold Nebraska Executive Director Jane Kleeb saw victories in the fact that the report acknowledged the revised route still crosses the Sandhills, which she called a “big shift” from earlier reports.
Environmental groups vowed to keep the pressure on Obama to reject the project.

“Our side continues to gain ground because landowners and environmentalists are now working together,” Kleeb said Friday.

Regardless of the president’s final verdict, a Nebraska lawsuit could still throw another obstacle in the path of the proposed 1,179-mile pipeline. Landowners who oppose the pipeline sued the state, challenging the constitutionality of a law that changed the pipeline route approval process, giving the governor and state environmental regulators the authority to approve or deny the revised route through Nebraska, rather than the Public Service Commission.

If the route review process is deemed unconstitutional, TransCanada would have to go back to square one with siting. A district judge hasn’t yet made a ruling after a one-day trial in September.
Contact Deena Winter at deena@nebraskawatchdog.org.

Researchers report on new catalyst to convert greenhouse gases into chemicals

By Karen B. Roberts

(Phys.org) —A team of researchers at the University of Delaware has developed a highly selective catalyst capable of electrochemically converting carbon dioxide—a greenhouse gas—to carbon monoxide with 92 percent efficiency. The carbon monoxide then can be used to develop useful chemicals.
The researchers recently reported their findings in Nature Communications.

"Converting carbon dioxide to useful chemicals in a selective and efficient way remains a major challenge in renewable and sustainable energy research," according to Feng Jiao, assistant professor of chemical and biomolecular engineering and the project's lead researcher.

Co-authors on the paper include Qi Lu, a postdoctoral fellow, and Jonathan Rosen, a graduate student, working with Jiao.

The researchers found that when they used a nano-porous silver electrocatalyst, it was 3,000 times more active than polycrystalline silver, a catalyst commonly used in converting carbon dioxide to useful chemicals.

Silver is considered a promising material for a carbon dioxide reduction catalyst because of it offers high selectivity—approximately 81 percent—and because it costs much less than other precious metal catalysts. Additionally, because it is inorganic, silver remains more stable under harsh catalytic environments.

The exceptionally high activity, Jiao said, is likely due to the UD-developed electrocatalyst's extremely large and highly curved internal surface, which is approximately 150 times larger and 20 times intrinsically more active than polycrystalline silver.
   
A UD engineering research team led by Feng Jiao has developed a highly selective catalyst capable of electrochemically converting carbon dioxide to carbon monoxide with 92 percent efficiency.
Credit: Evan Krape        

Jiao explained that the active sites on the curved internal surface required a much smaller than expected voltage to overcome the activation energy barrier needed drive the reaction.
The resulting carbon monoxide, he continued, can be used as an industry feedstock for producing synthetic fuels, while reducing industrial carbon dioxide emissions by as much as 40 percent.
To validate whether their findings were unique, the researchers compared the UD-developed nano-porous silver catalyst with other potential carbon dioxide electrocatalysts including polycrystalline silver and other silver nanostructures such as nanoparticles and nanowires.

Testing under identical conditions confirmed the non-porous silver catalyst's significant advantages over other silver catalysts in water environments.

Reducing greenhouse carbon dioxide emissions from fossil fuel use is considered critical for human society. Over the last 20 years, electrocatalytic carbon dioxide reduction has attracted attention because of the ability to use electricity from renewable energy sources such as wind, solar and wave.

Ideally, Jiao said, one would like to convert carbon dioxide produced in power plants, refineries and petrochemical plants to fuels or other chemicals through renewable energy use.
A 2007 Intergovernmental Panel on Climate Change report stated that 19 percent of greenhouse gas emissions resulted from industry in 2004, according to the Environmental Protection Agency's website.

"Selective conversion of carbon dioxide to carbon monoxide is a promising route for clean energy but it is a technically difficult process to accomplish," said Jiao. "We're hopeful that the catalyst we've developed can pave the way toward future advances in this area."

Explore further: Process holds promise for production of synthetic gasoline

More information: A selective and efficient electrocatalyst for carbon dioxide reduction." Qi Lu, Jonathan Rosen, Yang Zhou, Gregory S. Hutchings, Yannick C. Kimmel, Jingguang G. Chen, Feng Jiao. Nature Communications 5, Article number: 3242 DOI: 10.1038/ncomms4242 . Received 10 September 2013 Accepted 10 January 2014 Published 30 January 2014

Journal reference: Nature Communications

Provided by University of Delaware
Read more at: http://phys.org/news/2014-01-catalyst-greenhouse-gases-chemicals.html#jCp

 Read more at: http://phys.org/news/2014-01-catalyst-greenhouse-gases-chemicals.html#jCp

Glass that bends but doesn’t break

Natural forms inspire McGill researchers to develop a technique to make glass less brittle     

Published: 29 Jan 2014

Normally when you drop a drinking glass on the floor it shatters. But, in future, thanks to a technique developed in McGill’s Department of Mechanical Engineering, when the same thing happens the glass is likely to simply bend and become slightly deformed. That’s because Prof. François Barthelat and his team have successfully taken inspiration from the mechanics of natural structures like seashells in order to significantly increase the toughness of glass.

Normally when you drop a drinking glass on the floor it shatters. But, in future, thanks to a technique developed in McGill’s Department of Mechanical Engineering, when the same thing happens the glass is likely to simply bend and become slightly deformed. That’s because Prof. François Barthelat and his team have successfully taken inspiration from the mechanics of natural structures like seashells in order to significantly increase the toughness of glass.

“Mollusk shells are made up of about 95 per cent chalk, which is very brittle in its pure form,” says Barthelat. “But nacre, or mother-of-pearl, which coats the inner shells, is made up of microscopic tablets that are a bit like miniature Lego building blocks, is known to be extremely strong and tough, which is why people have been studying its structure for the past twenty years.”

Previous attempts to recreate the structures of nacre have proved to be challenging, according to Barthelat. “Imagine trying to build a Lego wall with microscopic building blocks. It’s not the easiest thing in the world.” Instead, what he and his team chose to do was to study the internal ‘weak’ boundaries or edges to be found in natural materials like nacre and then use lasers to engrave networks of 3D micro-cracks in glass slides in order to create similar weak boundaries. The results were dramatic.

The researchers were able to increase the toughness of glass slides (the kind of glass rectangles that get put under microscopes) 200 times compared to non-engraved slides. By engraving networks of micro-cracks in configurations of wavy lines in shapes similar to the wavy edges of pieces in a jigsaw puzzle in the surface of borosilicate glass, they were able to stop the cracks from propagating and becoming larger. They then filled these micro-cracks with polyurethane, although according to Barthelat, this second process is not essential since the patterns of micro-cracks in themselves are sufficient to stop the glass from shattering.

The researchers worked with glass slides simply because they were accessible, but Barthelat believes that the process will be very easy to scale up to any size of glass sheet, since people are already engraving logos and patterns on glass panels. He and his team are excited about the work that lies ahead for them.

“What we know now is that we can toughen glass, or other materials, by using patterns of micro-cracks to guide larger cracks, and in the process absorb the energy from an impact,” says Barthelat. “We chose to work with glass because we wanted to work with the archetypal brittle material. But we plan to go on to work with ceramics and polymers in future. Observing the natural world can clearly lead to improved man-made designs.”

To read the full paper: ‘Overcoming the brittleness of glass through bio-inspiration and micro-architecture’ by F. Barthelat et al in Nature Communications: http://www.nature.com/ncomms/2014/140128/ncomms4166/full/ncomms4166.html
The research was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Canada Foundation for Innovation (CFI), with partial support for one of the authors from a McGill Engineering Doctoral Award. The authors acknowledge useful technical advice by the company Vitro.
To contact the researcher directly: François Barthelat | Dept. Of Mechanical Engineering | McGill University | 514-398-6318

Contact Information

Contact: Katherine Gombay

Organization: Media Relations Office

Email: katherine.gombay@mcgill.ca

Office Phone: 514-398-2189