Monthly Archives: June 2013

CLEANING UP DIESEL TRUCKS COULD REDUCE CLIMATE CHANGE

 

Cutting our overall use of fossil fuels has proved a daunting challenge, but it might be possible to get some relief from the effects of climate change by selectively reducing the particulate pollution we produce. Recent research suggests that if we can clean up diesel engines and primitive cookstoves in India and China, for example, that could delay the effects of greenhouse-gas buildup even if pollution from coal-fired power plants persists. A studyreleased last week concludes that if every country were to do what California has done in the last couple of decades to clean up diesel emissions, it would slow down global warming by 15 percent. Reducing similar pollution from sources such as ships and cookstoves—which weren’t included in the study—could help even more.

The study comes as governments in India and China are deciding how to address their increasing pollution, which can contribute to fatal human health problems. Over the weekend, state-controlled media in China announced new pollution rules targeting both power plants and emissions from cars and trucks.

 

Highway Traffic Jam

Aerosol pollutants such as sulfur dioxide, soot, and ozone are all bad for human health, but they have different effects on the climate. “Some of the aerosols are warming the planet, and some are cooling the planet,” says Phil Rasch, a fellow at the Pacific Northwest National Laboratory in Richland, Washington. For example, sulfates that form from coal-plant exhaust reflect sunlight back into space, acting to shade the planet and cool it off. Black-carbon particles from diesel exhaust, on the other hand, absorb sunlight and heat up, warming the atmosphere.

“When you add them together, we think that on balance they’re cooling the planet,” Rasch says. That is, they mask some of the temperature increase that would have occurred as a result of carbon dioxide emissions, the main human contribution to global warming. But this effect would be more significant if the particulates that help heat up the atmosphere were removed. “If we could get rid of the ones that are warming the planet,” he says, “then that would buy us some more time.”

http://www.technologyreview.com/news/515961/cleaning-up-diesel-trucks-and-cooking-stoves-could-reduce-climate-change/

 

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New all-solid sulfur based battery outperforms lithium-ion technology

Scientists at the Department of Energy’s Oak Ridge National Laboratory have designed and tested an all-solid lithium-sulfur battery with approximately four times the energy density of conventional lithium-ion technologies that power today’s electronics.

The ORNL battery design, which uses abundant low-cost elemental sulfur, also addresses flammability concerns experienced by other chemistries.

“Our approach is a complete change from the current battery concept of two electrodes joined by a liquid electrolyte, which has been used over the last 150 to 200 years,” said Chengdu Liang, lead author on the ORNL study published this week in Angewandte Chemie International Edition.

Scientists have been excited about the potential of lithium-sulfur batteries for decades, but long-lasting, large-scale versions for commercial applications have proven elusive. Researchers were stuck with a catch-22 created by the battery’s use of liquid electrolytes: On one hand, the liquid helped conduct ions through the battery by allowing lithium polysulfide compounds to dissolve. The downside, however, was that the same dissolution process caused the battery to prematurely break down.

The ORNL team overcame these barriers by first synthesizing a never-before-seen class of sulfur-rich materials that conduct ions as well as the lithium metal oxides conventionally used in the battery’s cathode. Liang’s team then combined the new sulfur-rich cathode and a lithium anode with a solid electrolyte material, also developed at ORNL, to create an energy-dense, all-solid battery.

“This game-changing shift from liquid to solid electrolytes eliminates the problem of sulfur dissolution and enables us to deliver on the promise of lithium-sulfur batteries,” Liang said. “Our battery design has real potential to reduce cost, increase energy density and improve safety compared with existing lithium-ion technologies.”

The new ionically-conductive cathode enabled the ORNL battery to maintain a capacity of 1200 milliamp-hours (mAh) per gram after 300 charge-discharge cycles at 60 degrees Celsius. For comparison, a traditional lithium-ion battery cathode has an average capacity between 140-170 mAh/g. Because lithium-sulfur batteries deliver about half the voltage of lithium-ion versions, this eight-fold increase in capacity demonstrated in the ORNL battery cathode translates into four times the gravimetric energy density of lithium-ion technologies, explained Liang.

The team’s all-solid design also increases battery safety by eliminating flammable liquid electrolytes that can react with lithium metal. Chief among the ORNL battery’s other advantages is its use of elemental sulfur, a plentiful industrial byproduct of petroleum processing.

“Sulfur is practically free,” Liang said. “Not only does sulfur store much more energy than the transition metal compounds used in lithium-ion battery cathodes, but a lithium-sulfur device could help recycle a waste product into a useful technology.”

Although the team’s new battery is still in the demonstration stage, Liang and his colleagues hope to see their research move quickly from the laboratory into commercial applications. A patent on the team’s design is pending.

“This project represents a synergy between basic science and applied research,” Liang said. “We used fundamental research to understand a scientific phenomenon, identified the problem and then created the right material to solve that problem, which led to the success of a device with real-world applications.”

The study is published as “Lithium Polysulfidophosphates: A Family of Lithium-Conducting Sulfur-Rich Compounds for Lithium-Sulfur Batteries,” and is available online at http://dx.doi.org/10.1002/anie.201300680 . In addition to Liang, coauthors are ORNL’s Zhan Lin, Zengcai Liu, Wujun Fu and Nancy Dudney.

The research was sponsored by the U.S. Department of Energy, through the Office of Energy Efficiency and Renewable Energy’s Vehicle Technologies Office. The investigation of the ionic conductivity of the new compounds was supported by the Department’s Office of Science.

The synthesis and characterization was conducted at the Center for Nanophase Materials Sciences at ORNL. CNMS is one of the five DOE Nanoscale Science Research Centers supported by the DOE Office of Science, premier national user facilities for interdisciplinary research at the nanoscale. Together the NSRCs comprise a suite of complementary facilities that provide researchers with state-of-the-art capabilities to fabricate, process, characterize and model nanoscale materials, and constitute the largest infrastructure investment of the National Nanotechnology Initiative. The NSRCs are located at DOE’s Argonne, Brookhaven, Lawrence Berkeley, Oak Ridge and Sandia and Los Alamos national laboratories.For more information about the DOE NSRCs, please visithttp://science.energy.gov/bes/suf/user-facilities/nanoscale-science-research-centers .

http://www.ornl.gov/info/press_releases/get_press_release.cfm?ReleaseNumber=mr20130605-00