Resource World Magazine

meteorological factors, like air pressure, humidity and temperature. The figures on precipitation amounts and the duration of sunshine complete the data set. "We have achieved a unique sensory device that allows us to determine the impact of these parameters on wind conditions," says Klaas. The detailed measurements help determine the optimal alignment of wind turbines and the appropriate dimensions. This is the precondition for ensuring, for example, that the turbines are built at the correct height and designed with the least mass necessary. WAste siLiCON Gets NeW LiFe iN LithiuM-iON BAtteries Researchers at Rice University and the Université Catholique de Louvain, Belgium, have developed a way to make flexible components for rechargeable lithium-ion (LI) batteries from discarded silicon. Silicon absorbs 10 times more lithium than the carbon commonly used in LI batteries, but because it expands and contracts as it charges and discharges, it breaks down quickly. The researchers hope their devices are a step toward a new generation of flexible, efficient, inexpensive batteries that can conform to any shape. Samples of the material made at Rice look like strips of white tape or bandages. They used an established process, colloidal nanosphere lithography, to make a silicon corrosion mask by spreading polystyrene beads suspended in liquid onto a silicon wafer. The beads on the wafer self-assembled into a hexagonal grid – and stayed put when shrunken chemically. A thin layer of gold was sprayed on and the polystyrene removed, which left a fine gold mask with evenly spaced holes on top of the wafer. "Etching is not a new process," Reddy said. "But the bottleneck for battery appliNOVEMBER 2012 cations had always been taking nanowires off the silicon wafer because pure, freestanding nanowires quickly crumble." The electrolyte engulfs the nanowire array in a flexible matrix and facilitates its easy removal. "We just touch it with the razor blade and it peels right off," he said. The mask is left on the unperturbed wafer to etch a new anode. The Army Research Office supported research at Rice, and the National Scientific Research Foundation, the Special Research Fund, the TINTIN project – ARC, the French Community of Belgium, the Fund for Scientific Research and the Wallonne Region (Programme ERABLE) supported research in Belgium. WiND POWer MAY sustAiN GLOBAL eNerGY DeMANDs A recent study focused on finding the point at which wind energy extraction is highest and determined that wind energy could eventually sustain global energy needs. By using models, researchers were able to determine that more than 400 terawatts of power could be extracted from surface winds, and more than 1,800 terawatts could be generated by winds extracted throughout the atmosphere. Led by Kate Marvel, of Lawrence Livermore National Laboratory, who began this research at Carnegie Institute, a team used models to quantify the amount of power that could be generated from both surface and atmospheric winds. Surface winds were defined as those that can be accessed by turbines supported by towers on land or rising out of the sea. Highaltitude winds were defined as those that can be accessed by technology merging turbines and kites. The study looked only at the geophysical limitations of these techniques, not technical or economic factors. Turbines create drag, or resistance, which removes momentum from the winds and tends to slow them. As the number of wind turbines increase, the amount of energy that is extracted increases. But at some point, the winds would be slowed so much that adding more turbines would not generate more electricity. Civilization uses about 18 TW of power. Near-surface winds could provide more than 20 times today's global power demand and wind turbines on kites could potentially capture 100 times the current global power demand. At maximum levels of power extraction, there would be substantial climate effects to wind harvesting. But the study found that the climate effects of extracting wind energy at the level of current global demand would be small, as long as the turbines were spread out and not clustered in just a few regions. CONVeNtiON AtteNDees PeDAL tO eVeNts iN tAMPA AND ChArLOtte Humana Inc.'s [HUM-NYSE] Freewheelin pedal-powered, bike bus program recently provided transportation for the Republican National Convention (RNC), held in Tampa, Florida, and for the Democratic National Convention (DNC), held in Charlotte North Carolina. Over the two weeks of the conventions, Freewheelin participants, from across the nation, took 2,583 rides, pedaled 1,849 miles, and participated in 667 blood pressure and health screenings. The Freewheelin pedal bus is a first-ofits-kind design. The pedal bus is primarily made of stainless steel, aluminum alloy, powder-coated steel and premium marinegrade cloth to withstand the challenges of harsh atmospheres, such as salt air environments. Each bus accommodated up to 8 people and was furnished with a driver. To continue the Freewheelin legacy, Humana donated five pedal buses and one fruit cart to the Tampa Downtown Partnership (RNC) and Mecklenburg County Park and Recreation (DNC) in Charlotte. n www.resourceworld.com 59

• Cover