David Bradley Science Writer

Floating wind turbines could capture the energy of higher wind speeds further out to sea and address some of the noise and unsightliness complained about by those with turbines closer to home.

Wind turbines represent one of the most reliable renewable energy solutions, along with solar power and tidal and hydroelectric power. As wind turbine designs increase their size they also get noisier and become more of an eyesore. The solution is either to site them remotely on dry land or to build them at sea with the tower embedded in the seabed of shallow waters, but this restricts them to near-shore waters with depths no greater than 50 metres, which means they cannot utilise the strong winds further out to sea.

Now, naval architect Dominique Roddier of Berkeley, California-based Marine Innovation & Technology has, together with his team, published a feasibility study of a novel platform design – WindFloat – that, as the name suggests uses floating wind turbines. The study is published in the Journal of Renewable and Sustainable Energy this month.

Floating wind turbines could use stronger offshore winds (Credit: Roddier et al/JRSE/American Institute of Physics)

Roddier and colleagues, Christian Cermelli, Alexia Aubault, and Alla Weinstein, have tested a 1:65 scale model in a wave tank, which shows that a three-legged floating platform, based on existing gas and oil offshore platform designs. The team explains the main issue: “A floater supporting a large payload (wind turbine and nacelle) with large aerodynamic loads high above the water surface challenges basic naval architecture principles due to the raised centre of gravity and large overturning moment,” they say. In other words at first glance such a rig would capsize very easily. However, after several years work, their results show that the current design is stable enough to support a 5-megawatt wind turbine, the largest turbine that currently exists. These mammoth turbines are 70 metres tall and have rotors the size of a football field. Just one, Roddier says, produces enough energy “to support a small town.”

The next step is to continue construction of a prototype with electricity operator Energias de Portugal that will help the developers understand the life-cycle cost of such projects and to refine the economic model. The prototype will be tested in open water by the end of summer 2012, Roddier says. “The WindFloat [design] is envisioned to be located 15-20 km offshore so as to minimize risks/nuisance to the general public, and to mitigate the view impact from the coastline,” the team adds.

Links

J Renewable Sustainable Energy, 2010, 2, 3, 033104
Marine Innovation & Technology

David Bradley Science Writer

We’re repeatedly advised to switch off electrical devices, like TVs and DVD players at the mains outlet rather than leaving them in standby mode, to turn to compact fluorescent bulbs and to turn them off when illumination is no longer necessary, to do our laundry at lower temperatures, to run the dishwasher only when it’s full, and to avoid using energy-hungry power showers. All those kilowatts add up to a lot of power wasted if we don’t.

According to a new study into energy use in the UK, by following this advice we might be reducing our carbon footprint a lot more than we thought. Conversely, those who don’t follow the advice might be wasting far more energy than the government thinks and so contributing more to carbon dioxide emissions and so anthropogenic global warming and climate change. Writing in the journal Energy Policy this month, Adam Hawkes, of the Grantham Institute for Climate Change at Imperial College London, has calculated that the figures used by government advisors to estimate the possible carbon dioxide reduction possible might be 60% too low.

Hawkes points out that power stations that supply electricity vary in their carbon dioxide emission rates, depending on the fuel they use: those that burn fossil fuels (coal, gas and oil) have higher emissions than those driven by nuclear power and wind. In general only the fossil fuel power stations are able to respond instantly to changes in electricity demand. He says that the government should keep track of changing carbon emission rates from power stations to ensure that policy decisions for reducing emissions are based on robust scientific evidence.

Hawkes used 60 million data points for electricity production each half-hour period by each power station in Great Britain from 2002 to 2009 and calculated the emissions for each different type of generator by examining government data showing their average annual fuel use. He then calculated emissions rates attributed to a small change in electricity demand from these two data sets.

Montalto power station (Credit: David Bradley)

His new study suggests that excluding power stations with low carbon emission rates, such as wind and nuclear power stations, and focusing on those that deal with fluctuating demand would give a more accurate emission figure. Hawkes’ calculations show that, 0.43 kilograms of carbon dioxide per kilowatt hour of electricity consumed is 60 percent lower than the actual rates observed between 2002 and 2009 (0.69 kilograms of carbon dioxide per kilowatt hour), meaning that policy studies are underestimating the impact of people reducing their electricity use.

“One way governments are trying to mitigate the effects of climate change is to encourage people to reduce their energy consumption and change the types of technologies they use in their homes,” Hawkes says. “However, the UK government currently informs its policy decisions based on an estimate that, according to my research, is lower than it should be.”

Links

Energy Policy, 2010, online

David Bradley Science Writer

Scientists hope that Titan, a moon of Saturn, with its nitrogen-rich atmosphere, could act as a model system for terrestrial chemistry before life began on our planet. Now, another step towards that goal has emerged as researchers at the University of Arizona have incorporated atmospheric nitrogen into organic macromolecules under conditions resembling those on Titan.

“Titan is so interesting because its nitrogen-dominated atmosphere and organic chemistry might give us a clue to the origin of life on our Earth,” explains Hiroshi Imanaka, who is an assistant research scientist in the UA’s Lunar and Planetary Laboratory. “Nitrogen is an essential element of life.” Titan looks orange through a telescope because its atmosphere is a rich smog of organic molecules. Particles in the smog could settle on the surface and be exposed to conditions that might eventually create life, said Imanaka.

Saturn's A and F rings, the small moon Epimetheus and the smog-enshrouded Titan, Saturn’s largest moon. (Credit: NASA/JPL/Space Science Institute)

Of course, nitrogen alone is not enough, nitrogen molecules must be converted to a chemically active form that can drive the necessary biochemical reactions that underpin biological systems.

Imanaka and Mark Smith converted a nitrogen-methane gas mixture similar to Titan’s atmosphere into a collection of nitrogen-containing organic molecules by irradiating the gas with high-energy ultraviolet light. The laboratory set-up was designed to mimic how solar radiation affects Titan’s atmosphere.

Most of the nitrogen simply formed solid compounds directly, rather than gaseous ones, explains Smith, whereas previous theories suggested that nitrogen would move from gaseous compounds to solid ones in stepwise process. But, those settling particles may not contain nitrogen at all. If some of the particles are the same nitrogen-containing organic molecules created by the UA team in the laboratory then it would suggest that conditions conducive to life might just exist on Titan, Smith says.

These and other laboratory observations help scientists planning future space missions to decide on what to look for on other worlds that might hint at life and what instruments should be developed to help in the search.

Links

Proc Natl Acad Sci, 2010, online
Mark A. Smith homepage
UA lunar and planetary laboratory

David Bradley Science Writer

Just when you’d given up hope of another starburst, a third type comes along unannounced! This third class of previously unidentified supernova could help explain some anomalous observations in the night sky and even how our bodies come to contain so much calcium.

Until recently, astronomers had assumed there were just two types of supernovae. The first two types of supernova are either hot, young giants that explode on to the scene violently as they collapse under their own weight, or old, dense white dwarves (type a1) that undergo a thermonuclear explosion to briefly add their light to the night sky.

However, a third class appeared in telescope images in early January, 2005 and scientists, seeing that it had recently begun the process of exploding, started collecting and combining data from different telescope sites around the world, measuring both the amount of material thrown off in the explosion and its chemical composition.

Avishay Gal-Yam and colleagues at the Weizmann Institute in Israel and teams in Canada, Chile, Italy, UK, and USA, soon realised that the new supernova was neither old and dense nor young and hot.

There was too little material being ejected by the 2005 supernova for it to be an exploding giant, but its remote location from stellar nurseries suggested it was old. Moreover, its chemical makeup did not match the second type of supernova. The scientists turned to a computer simulation to see if they could figure out what kind of stellar processes could give rise to this anomalous kind of starburst.

Type Ia supernovae are primarily composed of carbon and oxygen as seen in their spectra, but the newly discovered supernova has unusually high levels of calcium and titanium which derive from nuclear reactions of helium not carbon and oxygen. However, the astronomers were initially at a loss to explain the source of the helium. Their simulations suggested that a pair of white dwarves might have been involved, with one assimilating helium from the other. When the thief star’s helium load rises past a certain point, the explosion occurs. “The donor star is probably completely destroyed in the process, but we’re not quite sure about the fate of the thief star,” says Gal-Yam.

Helium theft may have led to a third class of supernova that gives rise to the calcium in your bones and the titanium in a replacement hip! (Credit: Gal-Yam, Weizmann Institute of Science.

These new supernovae are relatively dim, so may not be as rare as they at first seem. This might explain why calcium is so prevalent in the universe and so in life on earth. The existence of radioactive titanium from these supernovae might also preclude the need for exotic explanations, such as invoking dark matter, of positrons at the heart of our galaxy. “Dark matter may or may not exist,” says Gal-Yam, “but these positrons are perhaps just as easily accounted for by the third type of supernova.”

Links

Avishay Gal-Yam homepage

David Bradley Science Writer

Graphene, a Manchester University discovery, is a material comprising sheets of carbon just one atom thick; graphene is like a single layer of graphite. However, it was the discovery that it has some peculiar electronic properties because of the existence of massless quasiparticles that has led to an explosion of interest in this material. Some researchers suggest that ultimately it will become the material that gives us a post-silicon world in computing.

Now, US scientists have made the first observation of the energy bands of complex particles within graphene known as plasmarons. This small step is an important one in understanding graphene and using it to develop devices for that future of ultrafast chemical computers.

At Berkeley Lab’s Advanced Light Source, an international team led by Aaron Bostwick and Eli Rotenberg have shown that these composite plasmaron particles are vital in generating graphene’s unique properties. “Graphene’s true electronic structure can’t be understood without understanding the many complex interactions of electrons with other particles.”

The electric charge carriers in graphene are negative electrons and positive holes, which in turn are affected by plasmons, oscillations in the density of the material that travel like sound waves through a sea of electrons. A plasmaron is “simply” a charge carrier coupled to a plasmon. “Although plasmarons were proposed theoretically in the late 1960s, and indirect evidence for them has been found, our work is the first observation of their distinct energy bands in graphene, or indeed in any material,” Rotenberg says. The team reported details of their findings in the journal Science in May.

Top: graphene structure. Bottom: a theoretical model of plasmaron interactions in graphene, sheets of carbon one atom thick.

The relationships between charge carriers, plasmons, and plasmarons will be important in the development of plasmonics, the architecture analogous to electronics in conventional silicon semiconductor circuitry. An important aspect of studying these relationships is to produce flat graphene sheets; graphene is usually rumpled like unmade bed linen. “One of the best ways to grow a flat sheet of graphene is by heating a crystal of silicon carbide,” Rotenberg explains, “and it happens that our German colleagues Thomas Seyller from the University of Erlangen and Karsten Horn from the Fritz Haber Institute in Berlin are experts at working with silicon carbide. As the silicon recedes from the surface it leaves a single carbon layer.”

With flat graphene sheets in hand, the team used a beam of low-energy, or soft, X-rays to analyse the materials. The resulting data provided them with an image of the electronic bands created by the electrons themselves. Even from the initial experiments, the team suspected graphene’s behaviour was more complicated than simple theory would suggest and seemed to hint at the existence of bare electrons. Since bare electrons cannot exist, the researchers postulated the fuzziness in their image was due to charge carriers emitting plasmons. Additional experiments with graphene sheets isolated from their support material revealed that electrons detached by the X-rays can leave behind either an ordinary hole or a hole bound to a plasmon – a plasmaron, explains Rotenberg.

“By their nature, plasmons couple strongly to photons, which promises new ways for manipulating light in nanostructures, giving rise to the field of plasmonics,” Rotenberg says. “Now we know that plasmons couple strongly to the charge carriers in graphene, which suggests that graphene may have an important role to play in the merging fields of electronics, photonics, and plasmonics on the nanoscale.”

Links

Science, 2010, 328, 999-1002
Eli Rotenberg homepage

David Bradley Science Writer

A low-temperature plasma probe can identify art fraud without damaging the artwork, which is important should the work turn out to be genuine.

Many priceless works of art are very delicate, so restoration, conservation, dating and authentication require sophisticated technical methods that avoid interfering with the substance of the work. Now, Sichun Zhang and colleagues at Tsinghua University in Beijing, China, have developed a new mass spectrometric imaging technique that can characterise paintings and calligraphy by barely scratching the surface.

In conventional mass spectrometry a substance is vaporised and then ionised to produce electrically charged particles of different sizes depending on the chemical structure of the compound. The ions are accelerated by an electric field and spread out by a magnetic field to produce a spectrum as the magnetic field makes particles of different mass to charge ratio deviate more or less than each other. Imaging mass spectrometry involves scanning a surface and releasing ions directly from the surface using special ionization methods. Unfortunately, these techniques require vacuum conditions, which limits sample size so that previously a tiny cutting would need to be removed from an artwork for analysis.

Probing reveals hidden information about art work without causing damage

The Chinese team has developed a low-temperature plasma probe, which consists of a fused capillary and two electrodes made of aluminium foil. High voltage alternating current applied to this probe induces a discharge in the capillary forming a low-temperature plasma; the probe reaches a mere 30 Celsius. However, in this state the helium plasma has energetic and excited enough to eject a few molecules from the surface of a sample and ionize them without measureable damage to a work of art.

The researchers used their approach to test seals, stamped signatures on Chinese paintings and calligraphy. They could reveal variations in ink composition easily, making it possible to differentiate between authentic and forged seals.

Links

Angew Chem Int Edn, 2010, online
Professor Dr. Xinrong ZHANG

David Bradley Science Writer

Quarks are apparently inseparable elementary particles from which protons and neutrons are composed. They have intriguing quantum properties that are labelled with everyday words, such as colour, strangeness and up and down that belie their mystery and disguise the mathematical analogues of electric charge for which these words are shorthand. One property that has been notoriously difficult to determine, is the mass of a quark.

Now, a research group at Cornell University, formed by physicist Peter Lepage has calculated, with a tiny margin of error, the mass of the three lightest and, therefore, most elusive quarks: up, down and strange. According to their results, the up quark weighs approximately 2 megaelectron volts (MeV), the down quark weighs approximately 4.8 MeV, and the strange quark weighs in at about 92 MeV. For comparison, one megaelectronvolt is about a millionth of the energy of a flying mosquito.

Scientists have known the mass of a proton for almost a century, but determining the mass of an individual quark was an on-going challenge not least because the strong force that binds them together in the proton and neutron is so powerful that they cannot be separated. The new work cuts the margins of error in quark mass by about 10 to 20 times down to a few percent, at least in a supercomputer simulation by separating the quarks virtually.

Determining the mass of an individual quark is difficult because they are apparently inseparable (Credit: Christine Davies/University of Glasgow)

The mass of the different quarks range from the sublime at a mere fraction of the proton mass (the up quark weighs in at 1/470th the mass of a proton). The heaviest, t quark, is 180 times heavier than a proton, which is almost as heavy as an entire atom of lead. Why the quark mass varies so much remains a mystery that might one day be solved by data emerging from the Large Hadron Collider in Geneva, which will pin down the origins of mass if it finds the so-called Higgs boson.

Links

Phys. Rev.Lett., 2010, 104 (13)
Prof G. Peter Lepage

David Bradley Science Writer

A new class of materials formed by combining liquid crystals and metal clusters glow intensely red in the infra-red region of the electromagnetic spectrum when irradiated over a broad range of wavelengths. The materials, dubbed clustomesogens, could be used in analytical instrumentation and potentially in display technologies.

Liquid crystals are well known in display technologies from digital watches to flat panel televisions. As their name suggests, they are at once liquid and can flow, but their molecules can also be oriented into something akin to a crystal state, usually under the influence of an electric field.

A second class of materials of interest to the optoelectronics field is metal clusters. Clusters are aggregates of just a few atoms, and so their properties are not those of individual atoms nor of the bulk metal, but somewhere in between. Indeed, metal clusters show some rather unusual electronic, magnetic, and optical properties because of the presence of the particular types of bonds that form between metals when just a few are present.

Now, Yann Molard, of the University of Rennes, in France, and colleagues there and at the University of Bucharest have united the two classes in clustomesogens to create metal clusters that exist in a liquid-crystalline phase.

Liquid crystals containing bonds between metal atoms are rare and usually limited to compounds in which just two metal atoms are connected in each unit. Molard and colleagues have produced liquid crystals that contains octahedral clusters made of six molybdenum atoms. Eight bromide ions sit on the eight surfaces of the octahedron, six fluorides and an aromatic organic group, or ligand, is at each vertex of the octahedron. These aromatic ligands each have three long hydrocarbon chains also ending in a pair of aromatic rings.

Yann Molard

Simple warming these materials initiates a process of self-organization in which the clusters stretch out to form long, narrow units arranged in what is known as a lamellar, plate-like, structure. The flat rings at the ends of the ligands of neighbouring layers are interleaved and the structure has liquid-crystalline properties.

“The association of mesomorphism with the peculiar properties of metallic clusters should lead to clustomesogens that offer great potential in the design of new electricity-to-light energy conversion systems, optically based sensors, and displays,” the team says.

Links

Angew Chem Int Edn, 2010, 49, 3351-3355
Yann Molard homepage

David Bradley Science Writer

A study of the shape of pumice from three adjacent submarine lava dome volcanoes in the western Pacific reveal that explosive volatility driven by the movement of molten magma is lower in deeper water. The shape of pumice stones, which are formed by expansion of magmatic volatiles as the magma rises to the sea surface, is different depending on the water depth and so can be a useful indicator of the evolution and eruption of underwater volcanoes.

Sharon Allen of the ARC Centre of Excellence in Ore Deposits and the School of Earth Sciences, at the University of Tasmania, Hobart, Australia and colleagues Richard Fiske of the Smithsonian Institution, Washington, DC, and Yoshihiko Tamura of the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), in Yokosuka Japan, used sampling and observations collected by a remotely operated vehicle of the three adjacent submarine lava dome volcanoes of the Sumisu, Izu-Bonin arc in the Western Pacific.

Domes of the volcanic complex have summits at ocean depths of 1100, 600, 245, and 95 metres and are mantled with pumice that is chemically identical but size, distribution, and surface texture varies enormously across the volcanic range.

Sharon Allen

According to a report in the May issue of the journal Geology, pumice generated from lava domes at water depths of more than 500 metres formed as a thick carapace on dense rock whereas at water depths less than 500 m pumice is blasted out. At shallower than 500 metre depths, the pumice occurs as an apron of blocky giant and smaller rough-textured clasts (rock fragments) enclosed by quenched margins and pockmarked by coarse [centimetre-sized] vesicles, a rock fragment within which is trapped a bubble of gas, the team explains.

The study shows that an increase in hydrostatic pressures over a range of 12 megapascals [120 times atmospheric pressure] reduces volatile-driven explosivity of the dome-forming eruptions the team says, it does not affect the formation of rocky “bubbles, the vesicles. “We conclude that metre-size, highly vesicular pumice is diagnostic of subaqueous dome eruptions in water depths of at least 1300 metres, and its morphology can be used to distinguish between explosive and effusive origins,” they conclude.

Links

Geology, 2010, 38(5), 391-394.
Sharon Allen homepage

David Bradley Science Writer

The Andes is the world’s longest continental mountain range and the highest outside Asia, with an average elevation of 4000 metres. The question of how quickly the mountains reached such heights has been a contentious one that University of Michigan paleoclimatologist Christopher Poulsen and graduate student Nadja Insel working with Todd Ehlers of the University of Tuebingen in Germany, believe they may now have settled with a new interpretation of isotopic data. Their work suggests that the rise of the Andes was a very gradual process.

Poulsen’s uplifting work suggests that previous interpretations of the evidence have misconstrued changes in oxygen isotope ratios as being due to a rapid rise of the mountain range whereas the more likely explanation is that the changes are due to shifts in ancient climate.

“In the modern climate, there is a well-known inverse relationship between oxygen isotopic values in rain and elevation,” Poulsen explains.
“As a rain cloud ascends a mountain range, it begins to precipitate.
Because atoms of oxygen-18 are more massive than those of oxygen-16, it is preferentially rained out. Thus, as you go up the mountain, the precipitation becomes more and more depleted in oxygen-18, and the ratio of oxygen-18 to oxygen-16 decreases.” Geologists use the ratio of these isotopes, preserved in rock, to infer past elevations and so the rate of rise of a mountain range.

“If the ratio decreases with time, as the samples get younger, the interpretation would typically be that there has been an increase in elevation at that location,” Poulsen adds. He points out that that is the precise conclusion drawn by a series of papers on the uplift history of The Andes published over the past four years. On the basis of oxygen isotope ratios determined by analysis of carbonate rocks, the authors of those papers suggested that the central Andes rose about 2500 to 3500 metres in a mere three million years, Other geologists had assumed that the rise to those heights took place over tens of millions of years.

Unfortunately, elevation is not the only thing to disturb oxygen isotope ratios in precipitation. “It can also be affected by where the vapour came from and how much it rained,” says Poulsen. “More intense rainfall also causes oxygen-18 to be preferentially precipitated.” He and his colleagues were skeptical of the rapid-rise scenario, and so performed climate modelling experiments to investigate whether something other than altitude might have given rise to the shift in ratio observed in carbonate deposits.

Andes: Credit to http://www.flickr.com/photos/atyt/

“The key result in our modelling study is that we identified an elevation threshold for rainfall,” Poulsen says. “Once The Andes reached an elevation greater than 70 percent of the current elevation, the precipitation rate abruptly increased. In our model, the increased precipitation also caused the ratio of oxygen-18 to oxygen-16 to significantly decrease. Our conclusion, then, is that geologists have misinterpreted the isotopic records in the central Andes. The decrease in the ratio is not recording an abrupt increase in elevation; it is recording an abrupt increase in rainfall.”

This conclusion is backed up by geochemical and sedimentological data, Poulsen said. “There is evidence that the central Andes became less arid at the same time that the isotope records show a decrease in the ratio of oxygen-18 to oxygen-16.”

Links

Christopher Poulsen

Science Express, 2010, online