Wednesday, January 18, 2012

One-third of car fuel consumption is due to friction loss

No less than one third of a car's fuel consumption is spent in overcoming friction, and this friction loss has a direct impact on both fuel consumption and emissions. However, new technology can reduce friction by anything from 10% to 80% in various components of a car, according to a joint study by VTT Technical Research Centre of Finland and Argonne National Laboratory (ANL) in USA. It should thus be possible to reduce car's fuel consumption and emissions by 18% within the next 5 to 10 years and up to 61% within 15 to 25 years.

There are 612 million cars in the world today. The average car clocks up about 13,000 km per year, and in the meantime burns 340 litres of fuel just to overcome friction, costing the driver EUR 510 per year.

Of the energy output of fuel in a car engine, 33% is spent in exhaust, 29% in cooling and 38% in mechanical energy, of which friction losses account for 33% and air resistance for 5%. By comparison, an electric car has only half the friction loss of that of a car with a conventional internal combustion engine.

Annual friction loss in an average car worldwide amounts to 11,860 MJ: of this, 35% is spent in overcoming rolling resistance in the wheels, 35% in the engine itself, 15% in the gearbox and 15% in braking. With current technology, only 21.5% of the energy output of the fuel is used to actually move the car; the rest is wasted.

Worldwide savings with new technology

A recent VTT and ANL study shows that friction in cars can be reduced with new technologies such as new surface coatings, surface textures, lubricant additives, low-viscosity lubricants, ionic liquids and low-friction tyres inflated to pressures higher than normal.

Friction can be reduced by 10% to 50% using new surface technologies such as diamond-like carbon materials and nanocomposites. Laser texturing can be employed to etch a microtopography on the surface of the material to guide the lubricant flow and internal pressures so as to reduce friction by 25% to 50% and fuel consumption by 4%. Ionic liquids are made up of electrically charged molecules that repel one another, enabling a further 25% to 50% reduction in friction.

In 2009, a total of 208,000 million litres of fuel was burned in cars worldwide just to overcome friction; this amounts to 7.3 million TJ (terajoules) of energy. Theoretically, introducing the best current technological solutions in all of the world's cars could save EUR 348,000 million per year; the best scientifically proven solutions known today could save EUR 576,000 million per year, and the best solutions to emerge over the next 10 years could save EUR 659,000 million per year.

Realistically, though, over a period of 5 to 10 years of enhanced action and product development measures could be expected to enable savings of 117,000 million litres in fuel consumption per year, representing an 18% reduction from the present level. Furthermore, in realistic terms, carbon dioxide emissions could be expected to decrease by 290 million tonnes per year and financial savings to amount to EUR 174,000 million per year in the short term.

Drivers can influence fuel consumption

A driver can significantly influence the fuel consumption of his or her car.. A reduction of 10% in driving speed, e.g. from 110 km/h to 100 km/h, translates into a 16% saving in fuel consumption. Slower speeds also allow for higher tyre pressures; an increase from 2 bar to 2.5 bar can translate into a 3% saving in fuel consumption.

VTT and ANL calculated friction loss in cars worldwide using a method that incorporated total crude oil consumption and fuel consumption of cars, the energy consumption of an average car, and the energy that an average car uses to overcome friction.

Friction losses were accounted for in the subsystems of a car -- tyres, engine, gearbox, brakes -- and also in its components, such as gears, bearings, gaskets and pistons. The friction losses caused at friction points and lubrication points were also considered.

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The above story is reprinted from materials provided by VTT Technical Research Centre of Finland, via AlphaGalileo.

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Journal Reference:

Kenneth Holmberg, Peter Andersson, Ali Erdemir. Global energy consumption due to friction in passenger cars. Tribology International, 2011; DOI: 10.1016/j.triboint.2011.11.022

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Keeping electronics cool: Findings on modified form of graphene could have impacts in managing heat dissipation

A University of California, Riverside engineering professor and a team of researchers have made a breakthrough discovery with graphene, a material that could play a major role in keeping laptops and other electronic devices from overheating.

Alexander Balandin, a professor of electrical engineering at the UC Riverside Bourns College of Engineering, and researchers from The University of Texas at Austin, The University of Texas at Dallas and Xiamen University in China, have shown that the thermal properties of isotopically engineered graphene are far superior to those of graphene in its natural state.

The research efforts were led by the Professor Rodney S. Ruoff of UT Austin and Balandin, a corresponding author for the paper, "Thermal conductivity of isotopically modified graphene." It was published online Jan. 8 by the journal Nature Materials and will later appear in the print publication.

The results bring graphene -- a single-atom thick carbon crystal with unique properties, including superior electrical and heat conductivity, mechanical strength and unique optical absorption -- one step closer to being used as a thermal conductor for managing heat dissipation in everything from electronics to photovoltaic solar cells to radars.

"The important finding is the possibility of a strong enhancement of thermal conduction properties of isotopically pure graphene without substantial alteration of electrical, optical and other physical properties," Balandin said. "Isotopically pure graphene can become an excellent choice for many practical applications provided that the cost of the material is kept under control."

He added: "The experimental data on heat conduction in isotopically engineered graphene is also crucially important for developing an accurate theory of thermal conductivity in graphene and other two-dimensional crystals."

The research used the optothermal Raman method, a thermal conductivity measuring technique developed by Balandin. In 2008, Balandin and his group members demonstrated experimentally that graphene is an excellent heat conductor. They also developed the first detailed theory of heat conduction in graphene and related two-dimensional crystals.

The work presented in the Nature Materials paper shows that the thermal conductivity of isotopically engineered graphene is strongly enhanced compared to graphene in its natural state.

Naturally occurring carbon materials, including graphene, are made up of two stable isotopes: about 99 percent of 12C (referred to as "carbon 12") and 1 percent of 13C (referred to as "carbon 13"). The difference between isotopes is in the atomic mass of the carbon atoms. The removal of just about 1 percent of carbon 13, also called isotopic purification, modifies the dynamic properties of crystal lattices and affects their thermal conductivity.

The importance of the present research is explained by practical needs for materials with high thermal conductivity. Heat removal has become a crucial issue for continuing progress in the electronics industry, owing to increased levels of dissipated power as the devices become smaller and smaller. The search for materials that conduct heat well has become essential for the design of the next generation of integrated circuits and three-dimensional electronics.

Balandin, who is also founding chair of the materials science and engineering (MS&E) program at UC Riverside, believes graphene will gradually be incorporated into different devices.

Initially, it will likely be used in some niche applications such as thermal interface materials for chip packaging or transparent electrodes in photovoltaic solar cells or flexible displays, he said.

In a few years, it could be used with silicon in computer chips, for example as interconnect wiring or heat spreaders. It also has the potential to benefit other electronic applications, including analog high-frequency transistors, which are used in wireless communications, radar, security systems and imaging.

Balandin and the following researchers contributed to the findings in the Nature Materials paper:

The team at UT Austin, which performed the isotopic purification of graphene, included Ruoff, Shanshan Chen, a post-doctoral fellow, Weiwei Cai a former post-doctoral researcher who is now a professor at the Xiamen University and Columbia Mishra, a graduate student.

The team at UT Dallas, who performed molecular dynamics simulations that compared well with the stronger thermal connectivity of the isotopically engineered graphene, included Kyeongjae Cho, a professor, and Hengji Zhang, graduate student.

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Helping chemistry become more environmentally-friendly

 Chemists often have to resort to destructive methods to analyse samples. For instance, they need to extract samples and apply substances like nitric acid to measure the concentration of metals in sediments. Ainara Gredilla of the University of the Basque Country (UPV/EHU) has laid the first foundations so that "greener" techniques can be used in the future.

She has analysed the concentration of metals in the estuary of Bilbao using traditional methods, and has created statistical models with the help of these data; she is hoping that the data obtained through traditional techniques in today's sediments can be used for tomorrow's sediments, and that way, further extractions of samples and the use of destructive substances can be avoided.

Her thesis is entitled Metalak eta metaloideak itsasadarretan: kutsadura jarraitzeko erreminta analitikoen garapena (Metals and metalloids in estuaries: development of analytical tools for monitoring contamination).

The work was carried out by the Analytical Research and Innovation (IBeA) group. In actual fact, her thesis supervisor and IBeA colleague Silvia Fernandez studied the concentrations of metal in the waters and sediments of the Nervión-Ibaizabal estuary (Bilbao) between 2005 and 2007, and Gredilla has followed up that piece of research. She gathered samples every three months, between April 2008 and October 2010. "I conducted a more specific spatial observation. We usually take samples of sediments and water in eight spots, but in this case we did so in 49," she explains.

The researcher has confirmed that the estuary is improving, but it still contains a higher concentration of metal than it should. She has come across peaks and troughs similar to those of between 2005 and 2007, but there are subtle differences. "As far as metal contaminants are concerned, in the waters an upward trend can be found, whereas in the sediments there is a downward trend," she says. The most robust hypothesis to account for this fact is the movement of contaminants between the sediments and the water: "The contamination comes from a spot located upriver from the estuary, and when salt water enters, the metal particles accumulate in the sediments. But if physico-chemical changes take place in the water, the particles could shift and return to it."

Spectra and chemometrics

However, the advances in 'green' chemistry constitute the main contribution of this work. She has obtained data from the Nervión-Ibaizabal estuary by means of the usual methods, but at the same time these data have enabled her to open up alternative techniques. These consist of infrared spectroscopy and X-rays, and this way it is possible to obtain data on a sediment sample without using chemical substances that destroy the sample.

In actual fact, this researcher has taken steps to interweave the results obtained in the traditional method with those from the alternative method. What happens is that a certain concentration of metal in a sedimentary sample (traditional method) corresponds to a specific projection when infrared spectroscopy or X-rays are applied (alternative method). So if information on the relation between the two values were to be compiled, there would be a possibility of predicting the data on the concentration of metal in each case using 'green' methods alone.

And how does one weave the relational network between these two types of values? By means of chemometrics. In other words, by applying mathematical and statistical methods to chemical data. "We combine the spectra deriving from the X-rays and the infrared spectroscopy with the concentrations of metal obtained through the previous method. So by adding the use of chemometric techniques we have developed some mathematical models. For example, they enable me to analyse 14 metals and come up with a model for each one and thus predict the concentration existing in each case," says Gredilla. This researcher spent three months at the University of Copenhagen during which she learnt the details of chemometric techniques for identifying groups.

So far she has only been able to develop the mathematical models for predicting the metal content on a theoretical level, but the aim is that this should be applicable in the future, "that one day it will be possible to determine the metal content of a sediment sample just by focussing X-rays on it. It would not be a question of taking fewer samples, but of making the analysis more straightforward and cutting the cost of it, as well as making it greener." Gredilla is now in fact getting ready to check the reliability of the models developed by applying them to sediments in other rivers worldwide. And she has just been offered the chance to participate in an international project alongside various European and South American researchers.

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The above story is reprinted from materials provided by Elhuyar Fundazioa.

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Trapping butterfly wings' qualities

A team of researchers from the United States and South Korea looked to the eye-catching blue wings of the male mountain swallowtail butterfly when they wanted a natural model for making better materials. The wings shed water easily because of that trap air and create a cushion between water and wing which allows water to roll easily off the surface. Because of the unique structure of the wing with miniscule hills and valleys, the of the water droplet is higher than the tension between the water and the wing -- enabling droplets to push off cleanly from the wings.

Engineers have long sought to create similarly water-repellent surfaces, but past attempts at artificial air traps tended to lose their contents over time due to external perturbations. In Australia, where the mountain swallowtail lives, the butterfly can be spotted at a distance of hundreds of meters away as sudden bright blue flashes.

"Mimicking biological surfaces in nature is an important part in a variety of practical applications," said Sang Ho Yun, a researcher in materials physics at the Royal Institute of Technology, in Kista, Sweden and the lead author of the new study, which will be published in an upcoming issue of the journal .

To create a new material, the researchers used a unique etching process to carve out tiny bumps and grooves on a wafer of silicon that trap both air and light, making a surface that eschewed water even under harsh conditions. They used many layers of silicon to trap air, and the intricate structure of pores, cones, bumps, and grooves also succeeded in catching light, almost perfectly absorbing wavelengths just above the .

"Owing to the simple , the present approach will certainly expand to generating other biomimetic surfaces on various organic and inorganic materials," said Yun.

According to Yun, the unique structure can be used as a model structure for studying other surfaces that could be made water-resistant for a long period of time. The biologically inspired surface could find uses in infrared imaging detectors, chemical sensors, and devices that combine electrical and optical components.

Other researchers have also found inspiration in the tiny bumps and brilliant colors of butterfly wings. According to Di Zhang, Director of State Key Lab of Metal Matrix Composites at Shanghai Jiao Tong University in China, most of the interest in butterfly wing scales comes from the tiny subtle microstructure. His group works on replicating the optical structure of the wings to create improved solar cells with a better ability to absorb light and convert it to electricity.

Zhang said that the etching process used by the other team is a very effective way to mimic the wings' natural structure in the lab.

"Moreover, they may have found the key structure parameters which have an influenced on the hydrophobicity," Zhang said, adding that those structures can help to create both waterproof and self-cleaning materials.

Other researchers point out that there are more ways to take cues from the natural world. According to Glen McHale, a professor of materials physics at Nottingham Trent University in Nottingham, U.K., some diving insects have sparse, rigid waterproof hairs to create a kind of shell for underwater breathing, and then have a denser set of hairs to prevent drowning if the first layer is penetrated -- and the new material takes a similar approach with its grooves and ridges.

McHale adds that are a good model for biomimicry experts because they are large enough to fly in the rain, while smaller insects hurry for cover. Their wing surfaces are covered in overlapping scales so they do not retain water and become heavy. Several recent studies have shed light on the inner workings of those scales in nature: they typically bend, but do not collapse, under the pressure of a water droplet. The scales can also shoot water in a particular direction, but removing them by damage or mutation will reduce the lifespan of the insects.

Provided by Inside Science News Service (news : web)

New materials remove CO2 from smokestacks, tailpipes and even the air

Alain Goeppert, G. K. Surya Prakash, chemistry Nobel Laureate George A. Olah and colleagues explain that controlling emissions of (CO2) is one of the biggest challenges facing humanity in the 21st century. They point out that existing methods for removing carbon dioxide from smokestacks and other sources, including the atmosphere, are energy intensive, don't work well and have other drawbacks. In an effort to overcome such obstacles, the group turned to solid materials based on polyethylenimine, a readily available and inexpensive polymeric material.

Their tests showed that these inexpensive materials achieved some of the highest carbon dioxide removal rates ever reported for humid air, under conditions that stymie other related materials. After capturing carbon dioxide, the materials give it up easily so that the CO2 can be used in making other substances, or permanently isolated from the environment. The capture material then can be recycled and reused many times over without losing efficiency. The researchers suggest the may be useful on submarines, in smokestacks or out in the open atmosphere, where they could clean up carbon dioxide pollution that comes from small point sources like cars or home heaters, representing about half of the total CO2 emissions related to human activity.

More information: Carbon Dioxide Capture from the Air Using a Polyamine Based Regenerable Solid Adsorbent, J. Am. Chem. Soc., 2011, 133 (50), pp 20164–20167. DOI: 10.1021/ja2100005

Easy to prepare solid materials based on fumed silica impregnated with polyethylenimine (PEI) were found to be superior adsorbents for the capture of carbon dioxide directly from air. During the initial hours of the experiments, these adsorbents effectively scrubbed all the CO2 from the air despite its very low concentration. The effect of moisture on the adsorption characteristics and capacity was studied at room temperature. Regenerative ability was also determined in a short series of adsorption/desorption cycles.

Provided by American Chemical Society (news : web)