Power Grid of the Future Saves Energy

Cars and trucks race down the highway, turn off into town, wait at traffic lights and move slowly through side streets. Electricity flows in a similar way -- from the power plant via high voltage lines to transformer substations. The flow is controlled as if by traffic lights. Cables then take the electricity into the city centre. Numerous switching points reduce the voltage, so that equipment can tap into the electricity at low voltage. Thanks to this highly complex infrastructure, the electricity customer can use all kinds of electrical devices just by switching them on.

"A reliable power supply is the key to all this, and major changes will take place in the coming years to safeguard this reliability. The transport and power networks will grow together more strongly as a result of electromobility, because electric vehicles will not only tank up on electricity but will also make their batteries available to the power grid as storage devices. Renewable energy sources will become available on a wider scale, with individual households also contributing electricity they have generated," says Professor Lothar Frey, Director of the Fraunhofer Institute for Integrated Systems and Device Technology IISB in Erlangen.

In major projects such as Desertec, solar thermal power plants in sun-rich regions of North Africa and the Middle East will in the future produce electricity for Europe. The energy will then flow to the consumer via long high-voltage power lines or undersea cables. The existing cables, systems and components need to be adapted to the future energy mix now, so that the electricity will get to the consumer as reliably and with as few losses as possible. The power electronics experts at the IISB are working on technological solutions, and are developing components for the efficient conversion of electrical energy.

For energy transmission over distances of more than 500 kilometers or for undersea cables direct current is being increasingly used. This possesses a constant voltage and only loses up to seven percent of its energy over long distances. By comparison, the loss rate for alternating current can reach 40 percent. Additional converter stations are, however, required to convert the high voltage of the direct current into the alternating current needed by the consumer.

"In cooperation with Siemens Energy we are developing high-power switches. These are necessary for transmitting the direct voltage in the power grid and are crucial for projects like Desertec. The switches have to be more reliable, more scaleable and more versatile than previous solutions in order to meet the requirements of future energy supply networks," says Dipl.-Ing. Markus Billmann from the IISB. To this end, the research scientists are using low-cost semiconductor cells which with previous switching techniques could not be used for high-voltage direct-current transmission (HVDCT).

"At each end of a HVDCT system there is a converter station," explains the research scientist."For the converters we use interruptible devices which can be operated at higher switching frequencies, resulting in smaller systems that are easier to control." A major challenge is to protect the cells from damage. Each converter station will contain about 5,000 modules, connected in series, and if more than a few of them failed at the same time and affected their neighboring modules a chain reaction could be triggered which would destroy the entire station."We have now solved this problem. With our cooperation partners we are working on tailor-made materials and components so that in future the equipment will need less energy," says Billmann.

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'Green' Way to Generate Heat and Electricity With Use of Fuel Cells

An SOFC fuel cell produces electricity and heat with a very high efficiency. That means less carbon emissions for each kW produced. Furthermore, the production of electricity happens with nearly no emissions of pollutants such as nitrogen and sulphur oxides. Thus, SOFC fuel cells are a strong card in the future climate-friendly energy supply. SOFC fuel cells are flat and thin as a piece of paper, providing a voltage of approx. 1 volt. They are put together in stacks to achieve the desired voltage and wattage.

The results from the research at Risø DTU are known internationally and have spread in ever-widening circles. Risø DTU entered into a long-term strategic cooperation agreement with Topsoe Fuel Cell, which developed fuel cell stacks into a commercial stage and is now marketing them under the name Topsoe PowerCores™. Topsoe Fuel Cell has subsequently entered into a long-term cooperation agreement with the Danish company Dantherm Power, which is selling small CHP plants, among other things. So long-term research conducted in Risø DTU's laboratories is now turning into concrete revolutionary products to be used in the supply of power and heat.

Each home will have a micro CHP plant of its own

To accommodate more renewable energy, the future electricity system will look significantly different from now. E.g. it is believed that today's large, central CHP plants will be supplemented with numerous quite small CHP plants of a few kW, in each home. These micro CHP plants in homes can help balance energy in the future energy system, where more energy will be coming from renewable energy sources such as the wind and the sun. The micro CHP plants will be taking over energy production, for example, when there is no wind, and when the sun is hiding behind a cloud.

"Topsoe Fuel Cell provides the engine, we produce the rest of what is to surround the engine in order to finally end up having a fully operational micro CHP plant," says Jesper Themsen from Dantherm Power. The core technology at Topsoe Fuel Cell is based on fuel cells developed at Risø DTU.

"At the moment, we are developing compact micro CHP plants, similar to a conventional oil or gas furnace when it comes to generating heat for the home. What's new about micro CHP plants, is that they also produce the power the home needs. In this way, you avoid transmission loss in the electricity and district heating network," says Jesper Themsen, technical director at Dantherm Power. Simultaneously, the micro CHP plants emit no or very little pollution and less carbon.

"In the spring of 2010 we produced a few micro CHP plants as part of the project 'Danish micro cogeneration'. Now we're doing tomorrow's micro CHP plant in cooperation with Topsoe Fuel Cell, and in October 2010, we produced two systems that we will put into operation among professional users, for example plumbers or electricians. People with craftsman experience who can help us solve the problems that naturally arise with the plants during the first phase,"says Jesper Themsen. The first plants will generate 1 kW of power and 1 kW of heat and will be powered by natural gas.

"Subsequently, we will produce five micro CHP plants, which will also be put into operation among professional users. We are still in the early process of the technological launch and need to gather as much experience with these systems as possible," says Jesper Themsen.

The micro CHP plants are based on Topsoe PowerCores™. Dantherm Power will build the rest around them. It should be possible to add natural gas purified of sulphur and with the correct pressure. There must be supply of fresh air, a heat exchanger and a heat store. The necessary electronic control for the micro CHP plant to be connected to the grid will be incorporated. Last but not least, the micro CHP plants will have to gain security clearance.

Currently, micro CHP plants are the size of an overgrown American fridge."It's not that we cannot make them smaller, but here to start with it should not be too compact, but easy for one to supervise and maintain the various parts of the plant," says Jesper Themsen.

Dantherm Power expects to have seven micro CHP plants in operation in early 2011, which will be in operation throughout the entire heating season and well into spring 2011.

In September 2011, Dantherm Power plans to produce 15 new micro CHP plants based on experiences from the first seven."They'll be so reliable that we can install them in private homes in Southern Jutland," says Jesper Themsen and continues:"In 2012, we believe that SOFC micro CHP plants will be affordable and have the desired properties, allowing ordinary people to easily replace their old furnace with a SOFC micro CHP plant."

Jesper Themsen expects a major breakthrough to happen in 2013 -- 2015 and that many Danish families in 2015 will be having a SOFC micro CHP plant, which will not take up more space than a dishwasher. Fuels will initially be natural gas, later it could be methanol and liquefied petroleum gas. In the long term, biofuels could also prove useful.

"We are having a long-term strategic cooperation with Topsoe Fuel Cell on SOFC micro CHP plants, and we are working mutually to make SOFC fuel cell power plants a commercial success," says Jesper Themsen.

In the long term, he imagines that fuel cell power plants will replace generators powered by diesel or gas. They are used as backup in countries where the grid is not as stable as in Denmark. Here they are in operation continuously for many hours with the purpose of using the fuel efficiently.

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More Efficient Polymer Solar Cells Fabricated

"Our technology efficiently utilizes the light trapping scheme," said Sumit Chaudhary, an Iowa State assistant professor of electrical and computer engineering and an associate of the U.S. Department of Energy's Ames Laboratory."And so solar cell efficiency improved by 20 percent."

Details of the fabrication technology were recently published online by the journalAdvanced Materials.

Chaudhary said the key to improving the performance of solar cells made from flexible, lightweight and easy-to-manufacture polymers was to find a textured substrate pattern that allowed deposition of a light-absorbing layer that's uniformly thin -- even as it goes up and down flat-topped ridges that are less than a millionth of a meter high.

The result is a polymer solar cell that captures more light within those ridges -- including light that's reflected from one ridge to another, he said. The cell is also able to maintain the good electrical transport properties of a thin, uniform light-absorbing layer.

Tests indicated the research team's light-trapping cells increased power conversion efficiency by 20 percent over flat solar cells made from polymers, Chaudhary said. Tests also indicated that light captured at the red/near infrared band edge increased by 100 percent over flat cells.

Researchers working with Chaudhary on the solar cell project are Kai-Ming Ho, an Iowa State Distinguished Professor of Physics and Astronomy and an Ames Laboratory faculty scientist; Joong-Mok Park, an assistant scientist with the Ames Laboratory; and Kanwar Singh Nalwa, a graduate student in electrical and computer engineering and a student associate of the Ames Laboratory. The research was supported by the Iowa Power Fund, the Ames Laboratory and the Department of Energy's Office of Basic Energy Sciences.

The idea of boosting the performance of polymer solar cells by using a textured substrate is not a new one, Chaudhary said. The technology is commonly used in traditional, silicon-based solar cells.

But previous attempts to use textured substrates in polymer solar cells have failed because they require extra processing steps or technically challenging coating technologies. Some attempts produced a light-absorbing layer with air gaps or a too-thin layer over the ridges or a too-thick layer over the valleys. The result was a loss of charges and short circuiting at the valleys and ridges, resulting in poor solar cell performance.

But, get the substrate texture and the solution-based coating just right,"and we're getting more power out," Nalwa said.

The Iowa State University Research Foundation Inc. has filed a patent for the substrate and coating technology and is working to license the technology to solar cell manufacturers.

"This may be an old idea we're using," Chaudhary said,"but it's never before been successfully implemented in polymer solar cells."

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Electrocution of Birds and Collision With Power Lines: Solutions to a Global Problem

Bird death by electrocution is a global problem that has been aggravated by increases in the energy demand of certain regions and is particularly prevalent in natural areas where the introduction of power lines is a cause of significant disruption to local species. In Catalonia, electrocution is the primary cause of death of the Bonelli's Eagle (Aquila fasciata), and across the rest of the Iberian Peninsula it affects particularly large numbers of the endangered Iberian Imperial Eagle (Aquila adalberti) and many other ecologically valuable species. In the United States, the problem has a particular impact on the highly symbolic Bald Eagle (Haliaeetus leucocephalus). In Africa, common victims include the Cape Vulture (Gyps coprotheres) and the Egyptian Vulture (Neophron percnopterus).

Electrocution: Threats and solutions

Electrocution occurs when a bird comes into contact with two wires or when it perches on a conductive pylon (for example, a metal structure) and comes into simultaneous contact with a wire. In Catalonia, there are more than 1000 different models of electricity pylons, which pose different levels of threat to birds. The article published in theJournal of Wildlife Managementconfirms the validity of the predictive model designed by the UB research group to determine the risk of electrocution according to pylon design and location, as well as verifying the effectiveness of corrective measures implemented at electrocution blackspots.

Joan Real explains that,"The threat posed by a pylon depends on the electrotechnical design and the natural features around it. If we apply the predictive model we can correct power lines more effectively without having to apply measures to entire spans of the transmission network." The model makes it possible to select and act on the most dangerous pylons and correct them effectively. According to Joan Real, applying correction measures"to only 6% of the most dangerous pylons could reduce bird mortality by up to 70%."

Effectiveness of corrective measures

The article reviews more than ten years of pioneering work by the UB team on the detection and correction of potentially dangerous pylons and the evaluation of anti-electrocution measures over an area of 210,000 hectares in the Barcelona pre-littoral mountains. In the design of the predictive tool, the team modelled the risk of bird electrocution posed by 3,869 electricity pylons. Next, the team worked with power companies to apply corrective measures to the most dangerous pylons identified by the model (those with wires or connectors above the cross-arms and located in natural habitats or areas selected by bird species for specific activities). The study confirms that these anti-electrocution measures are effective and reduce the number of birds electrocuted in their natural habitats.

As Joan Real explains,"The predictive model is effective in identifying the pylons that present the greatest risk of electrocution. The results also show the effectiveness of corrective measures in preventing bird death through electrocution." Through its research, the Conservation Biology Group has developed a strategic analytical tool that will be of use to any public or private body involved in environment management in areas where transmission infrastructures have had adverse effects on bird life -- a specific environmental problem recognized by the Convention on Migratory Species (Bonn Convention, 2002) and in many EU conservation directives, as well as receiving specific mention in the recent decree on power transmission lines announced by the Spanish government.

Collision: A hidden threat

Electrocution is not the only threat that power lines pose to bird species. Collision also has an impact on the survival of birds, in particular endangered species and those with wider home ranges, which include various species of eagles. The findings of an article produced by the UB's Conservation Biology Group, published in the journalBird Conservation International, suggest that the problem is more serious than previously thought.

"Collision with power lines is a lesser-known problem than electrocution and is harder to detect because it can occur at any point along the transmission line," exaplins Joan Real. In the case of power lines, the bird collides with one of the wires, generally the earth wire, which is less visible. In the study, the UB team presents a predictive model for determining which lines and spans create the greatest risk of collision, describing the most effective strategies for reducing the number of accidents caused by transmission lines. The results of the article, based on a radio-tracking study of Bonelli's eagle populations in the Barcelona and Tarragona area, suggest that collision risk is influenced by a number of factors, including the topography of surrounding terrain and the proximity of lines and pylons to nests and other areas used frequently by local species.

Since 1980, the Conservation Biology Group has carried out applied research for the conservation of endangered species aimed at identifying effective preventive measures which can be applied by conservation managers and other stakeholders. The group is supported by the Miquel Torres Foundation in Vilafranca Penedès, and funding for its most recent studies has been provided by Barcelona Regional Council and the companies FECSA-ENDESA, Estabanell i Paysa S.A., Electra Caldense S.A. and Red Eléctrica de España, S.A.

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Manufacturing 'Made to Measure' Atomic-Scale Electrodes

Results were published in the journalNature Nanotechnology.

One of the key problems in nanotechnology is the formation of electrical contacts at an atomic scale. This demands the detailed characterisation of the current flowing through extremely small circuits– so small that their components can be individual atoms or molecules. It is precisely this miniature nature of the system, of typically nanometric dimensions (1 metro = a thousand million nanometers), where the difficulty of this yet unresolved problem arises. In particular, in unions formed by a single molecule, it has been shown that the number of individual atoms making up the contact and their positions are crucial when determining the electric current that is flowing. To date, there has been no experiment where it has been possible to control these parameters with sufficient precision.

In the research published in theNature Nanotechnologyjournal, however, these scientists have revealed and explained the changes that the electric current flowing through a molecular union (metal/molecule/metal) undergoes, depending on the area of contact uniting the molecule to the metallic electrodes. Basically, changing the number of atoms in contact with the molecule, one by one, it goes from a low state (bad contact) to another, higher one (good contact) of conduction. With bad contact the current is limited by the area of contact, while with good contact the current is limited by the intrinsic properties of the molecule.

Taking part in this collaboration project were scientists from the Donostia International Physics Center (DIPC), from the Physics of Materials Centre at the CSIC-University of the Basque Country (UPV/EHU) Mixed Centre and from the Department of the Physics of Materials at the Chemistry Faculty of the UPV/EHU.

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Electron 'Pairing': Triplet Superconductivity Proven Experientially for First Time

The researchers reported on their findings in the American Physical Society's journalPhysical Review B.

If it were possible to eliminate electrical resistance we could reduce our electric bill significantly and make a significant contribution to solving the energy problem, if it were not for a few other problems. Many metals as well as oxides demonstrate a superconductive state, however only at low temperatures. The superconductive effect results from Cooper pairs that migrate through the metal together"without resistance." The electrons in each Cooper pair are arranged so that their composite angular momentum is zero. Each electron has an angular momentum, the so-called spin, with a value of 1/2. When one electron spins counterclockwise (-1/2) and the other clockwise (+1/2), the total of the two spin values is zero. This effect, found only in superconductors, is called the singlet state.

If a superconductor is brought into contact with a ferromagnetic material, the Cooper pairs are broken up along the shortest path and the superconductor becomes a normal conductor. Cooper pairs cannot continue to exist in a singlet state in a ferromagnetic material. Researches at RUB (Prof. Konstantin Efetov, Solid State Physics) among others have, however, theoretically predicted a new type of Cooper pair, which has a better chance of survival in ferromagnetic materials. In such Cooper pairs the electrons spin in parallel with one another so that they have a finite spin with a value of 1. Since this angular momentum can have three orientations in space, it is also known as the triplet state."Obviously there can also be only one certain, small fraction of Cooper pairs in a triplet state, which then quickly revert to the singlet state" explained Prof. Kurt Westerholt."The challenge was to verify these triplet Cooper pairs experimentally."

Superconductors allow us to produce highly sensitive detectors for magnetic fields, which even allow detection of magnetic fields resulting from brain waves. These detectors are called SQUID's (superconducting quantum interference devices) -- components which use the superconductive quantum properties. The central feature in these components consists of so-called tunnel barriers with a series of layers made up of a superconductor, insulator and another superconductor. Quantum mechanics allows a Cooper pair to be"tunneled" through a very thin insulating layer. Tunneling of a large number of Cooper pairs results in a tunnel current."Naturally the barrier cannot be too thick, otherwise the tunnel current subsides. A thickness of one to two nanometers is ideal," according to Prof. Hermann Kohlstedt (CAU).

If part of the tunnel barrier is replaced by a ferromagnetic layer, the Cooper pairs are broken up while they are still in the barrier and do not reach the superconductor on the other side. The tunnel current decreases drastically."Triplet Cooper pairs can, however, be tunneled much better through such a ferromagnetic barrier," says Dirk Sprungmann, who was involved as Ph.D. student. If we are successful in converting a portion of the singlet Cooper pairs to triplet Cooper pairs, the tunnel current should be significantly stronger and be able to pass through a thicker ferromagnetic layer. This is precisely what the physicists in Bochum and Kiel tested. They allowed the Cooper pairs to pass through ferromagnetic barriers with thicknesses of up to 10 nanometers. With this attempt the physicists achieved a double success. On the one hand they were able to experimentally verify the existence of triplet Cooper pairs, and, on the other, they demonstrated that the tunnel current is greater than for singlet Cooper pairs in conventional tunnel contacts."These new ferromagnetic tunnel barriers may possibly be used for new types of components," states Dr. Martin Weides (Santa Barbara). With their research findings the scientists confirmed, among other things, the theoretical work of a Norwegian research team published only a few weeks before.

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Declining Energy Quality Could Be Root Cause of Current Recession, Expert Suggests

Many economists have pointed to a bursting real estate bubble as the initial trigger for the current recession, which in turn caused global investments in U.S. real estate to turn sour and drag down the global economy. King suggests the real estate bubble burst because individuals were forced to pay a higher and higher percentage of their income for energy -- including electricity, gasoline and heating oil -- leaving less money for their home mortgages.

In economic terms, the quality of the nation's energy supply is referred to as Energy Return on Energy Investment (EROI). For example, if an oil company uses a 10th of a barrel of oil to drill, pump, transport and refine one barrel of oil, the EROI for the refined fuel is 10.

"Many economists don't think of energy as being a limiting factor to economic growth," says King, a research associate in the university's Center for International Energy and Environmental Policy."They think continual improvements in technology and efficiency have completely decoupled the two factors. My research is part of a growing body of evidence that says that's just not true. Energy still plays a big role."

In a paper published this November in the journalEnvironmental Research Letters, King introduced a new way to measure energy quality, the Energy Intensity Ratio (EIR), that is easier to calculate, highly correlated to EROI and in some ways more powerful than EROI. EIR measures how much profit is obtained by energy consumers relative to energy producers. The higher the EIR, the more economic value consumers (including businesses, governments and people) get from their energy.

When King plots EIR for various fuels every year since World War II, the graphs indicate two large declines, one before the recessions of the mid-1970s and early 1980s and the other during the 2000s, leading up to the current economic recession. There have been other recessions in the U.S. since World War II, but the longest and deepest were preceded by sustained declines in EIR for all fossil fuels.

EIR is proportional to EROI, meaning they rise and fall together, but the basic data behind the EIR calculations come out annually as opposed to every five years for EROI. EIR also gives insight into different parts of the supply chain such as at the refinery or at the gas pump, which are harder to study with EROI.

King's analysis suggests if EIR falls below a certain threshold, the economy stops growing. For example, in 1972, EIR for gasoline was 5.9 and in 2008 it was 5.5. During times of robust economic growth, such as the 1990s, EIR for gasoline was well over eight. Compare that to some estimates of EROI and EIR for corn ethanol of around one, and it's clear why corn ethanol has been widely criticized as a low quality energy source.

To get the U.S. economy growing again, King says Americans will have to produce and use energy more efficiently. That's essentially what the U.S. did after the last energy crisis by raising fuel efficiency standards for cars, increasing use of natural gas for electric power generation and developing new technologies such as Enhanced Oil Recovery to coax more oil out of the ground.

"If we aren't fundamentally changing the way we produce or consume energy now, don't expect the economy to grow as much as the past two decades," he says.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

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Imaging With Neutrons: Magnetic Domains Shown for the First Time in 3-D

Up until now, it has only been possible to image magnetic domains in 2 dimensions. Now, for the first time, scientists at Helmholtz-Zentrum Berlin have managed to create 3-dimensional images of these domains deep within magnetic materials.

Every magnetic material is divided into such magnetic domains. Scientists call them"Weiss domains" after physicist Pierre-Ernest Weiss, who predicted their existence theoretically more than a hundred years ago. In 1907, he recognized that the magnetic moments of atoms within a bounded domain are equally aligned.

All pursuit of this theory has so far been limited to two-dimensional images and material surfaces. Accordingly, researchers have only ever been able to see a domain in cross section. Together with colleagues from the German Federal Institute for Materials Research and Testing and the Swiss Paul-Scherrer-Institute, Dr. Ingo Manke and his group at the Institute of Applied Material Research at HZB have developed a method by which they can image the full spatial structure of magnetic domains -- even deep within materials. To do this, special iron-silicon crystals were produced at the Leibniz Institute for Solid State and Materials Research Dresden, for which the research group of Rudolf Schäfer had already developed model representations. Their actual existence has now been proven for the first time. With it, the researchers have solved a decade-old problem in imaging. 

Most magnetic materials consist of a complex network of magnetic domains. The researchers' newly developed method exploits the areas where the domains meet -- the so-called domain walls. Within a domain, all magnetic moments are the same, but the magnetic alignment is different from one domain to another. So, at each domain wall, the direction of the magnetic field changes. The researchers exploit these changes for their radiographic method in which they use not light, but neutrons.

Magnetic fields deflect the neutrons slightly from their flight path, just as water diverts light. An object under water cannot be directly perceived because of this phenomenon; the object appears distorted and in a different location. Similarly, the neutrons pass through domain walls along their path through the magnetic material. At these walls, they are diverted into different directions.

This diversion, however, is only a very weak effect. It is typically invisible in a neutron radiogram, since it is overshadowed by non-diverted rays. The researchers therefore employ several diffraction gratings in order to separate the diverted rays. During a measurement, they rotate the sample and shoot rays through it from all directions. From the separated rays, they can calculate all domain shapes and generate an image of the domain network in its entirety.

Magnetic domains are important for understanding material properties and the natural laws of physics. They also play an important role in everyday life: most notably in storage media such as hard disks, for example, or battery chargers for laptops or electric vehicles. If the domain properties are carefully chosen to minimize electricity loss at the domain walls, the storage medium becomes more efficient.

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Enhancing the Efficiency of Wind Turbines

New ideas for enhancing the efficiency of wind turbines are being presented this week at the American Physical Society Division of Fluid Dynamics meeting in Long Beach, CA.

One issue confronting the efficiency of wind energy is the wind itself -- specifically, its changeability. The aerodynamic performance of a wind turbine is best under steady wind flow, and the efficiency of the blades degrades when exposed to conditions such as wind gusts, turbulent flow, upstream turbine wakes, and wind shear.

Now a new type of air-flow technology may soon increase the efficiency of large wind turbines under many different wind conditions.

Syracuse University researchers Guannan Wang, Basman El Hadidi, Jakub Walczak, Mark Glauser and Hiroshi Higuchi are testing new intelligent-systems-based active flow control methods with support from the U.S. Department of Energy through the University of Minnesota Wind Energy Consortium. The approach estimates the flow conditions over the blade surfaces from surface measurements and then feeds this information to an intelligent controller to implement real-time actuation on the blades to control the airflow and increase the overall efficiency of the wind turbine system. The work may also reduce excessive noise and vibration due to flow separation.

Initial simulation results suggest that flow control applied on the outboard side of the blade beyond the half radius could significantly enlarge the overall operational range of the wind turbine with the same rated power output or considerably increase the rated output power for the same level of operational range. The team is also investigating a characteristic airfoil in a new anechoic wind tunnel facility at Syracuse University to determine the airfoil lift and drag characteristics with appropriate flow control while exposed to large-scale flow unsteadiness. In addition, the effects of flow control on the noise spectrum of the wind turbine will be also assessed and measured in the anechoic chamber.

Another problem with wind energy is drag, the resistance felt by the turbine blades as they beat the air. Scientists at the University of Minnesota have been looking at the drag-reduction effect of placing tiny grooves on turbine blades. The grooves are in the form of triangular riblets scored into a coating on the blade surface. They are so shallow (between 40 and 225 microns) that they can't be seen by the human eye -- leaving the blades looking perfectly smooth.

Using wind-tunnel tests of 2.5 megawatt turbine airfoil surfaces (becoming one of the popular industry standards) and computer simulations, they are looking at the efficacies of various groove geometries and angles of attack (how the blades are positioned relative to the air stream).

Riblets like these have been used before, in the sails on sailboats taking part in the last America's Cup regatta and on the Airbus airliner, where they produced a drag reduction of about 6 percent. The design of wind turbine blades was, at first, closely analogous to that of airplane wings. But owing to different engineering concerns, such as turbine blades having a much thicker cross section close to the hub and wind turbines having to cope with peculiar turbulence near the ground, drag reduction won't be quite the same for wind turbines.

University of Minnesota researchers Roger Arndt, Leonardo P. Chamorro and Fotis Sotiropoulos believe that riblets will increase wind turbine efficiency by about 3 percent.

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Electrowetting Breakthrough May Lead to Disposable E-Readers Fast Enough for Video

In the research, Steckl and UC doctoral student Duk Young Kim demonstrated that paper could be used as a flexible host material for an electrowetting device. Electrowetting (EW) involves applying an electric field to colored droplets within a display in order to reveal content such as type, photographs and video. Steckl's discovery that paper could be used as the host material has far-reaching implications considering other popular e-readers on the market such as the Kindle and iPad rely on complex circuitry printed over a rigid glass substrate.

"One of the main goals of e-paper is to replicate the look and feel of actual ink on paper," the researchers stated in the ACS article."We have, therefore, investigated the use of paper as the perfect substrate for EW devices to accomplish e-paper on paper."

Importantly, they found that the performance of the electrowetting device on paper is equivalent to that of glass, which is the gold standard in the field.

"It is pretty exciting," said Steckl."With the right paper, the right process and the right device fabrication technique, you can get results that are as good as you would get on glass, and our results are good enough for a video-style e-reader."

Steckl imagines a future device that is rollable, feels like paper yet delivers books, news and even high-resolution color video in bright-light conditions.

"Nothing looks better than paper for reading," said Steckl, an Ohio Eminent Scholar."We hope to have something that would actually look like paper but behave like a computer monitor in terms of its ability to store information. We would have something that is very cheap, very fast, full-color and at the end of the day or the end of the week, you could pitch it into the trash."

Disposing of a paper-based e-reader, Steckl points out, is also far simpler in terms of the environmental impact.

"In general, this is an elegant method for reducing device complexity and cost, resulting in one-time-use devices that can be totally disposed after use," the researchers pointed out.

Steckl's goal is attract commercial interest in the technology for next-stage development, which he expects will take three to five years to get to market.

The work was supported, in part, by a grant from the National Science Foundation and was conducted at the Nanoelectronics Laboratory at the University of Cincinnati College of Engineering and Applied Science.

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Short, on-Chip Light Pulses Will Enable Ultrafast Data Transfer Within Computers

Details appeared online in the journalNature Communicationson November 16.

This miniaturized short pulse generator eliminates a roadblock on the way to optical interconnects for use in PCs, data centers, imaging applications and beyond. These optical interconnects, which will aggregate slower data channels with pulse compression, will have far higher data rates and generate less heat than the copper wires they will replace. Such aggregation devices will be critical for future optical connections within and between high speed digital electronic processors in future digital information systems.

"Our pulse compressor is implemented on a chip, so we can easily integrate it with computer processors," said Dawn Tan, the Ph.D. candidate in the Department of Electrical and Computer Engineering at UC San Diego Jacobs School of Engineering who led development of the pulse compressor.

"Next generation computer networks and computer architectures will likely replace copper interconnects with their optical counterparts, and these have to be complementary metal oxide semiconductor (CMOS) compatible. This is why we created our pulse compressor on silicon," said Tan, an electrical engineering graduate student researcher at UC San Diego, and part of the National Science Foundation funded Center for Integrated Access Networks.

The pulse compressor will also provide a cost effective method to derive short pulses for a variety of imaging technologies such as time resolved spectroscopy -- which can be used to study lasers and electron behavior, and optical coherence tomography -- which can capture biological tissues in three dimensions.

In addition to increasing data transfer rates, switching from copper wires to optical interconnects will reduce power consumption caused by heat dissipation, switching and transmission of electrical signals.

"At UC San Diego, we recognized the enabling power of nanophotonics for integration of information systems close to 20 years ago when we first started to use nano-scale lithographic tools to create new optical functionalities of materials and devices -- and most importantly, to enable their integration with electronics on a chip. This Nature Communications paper demonstrates such integration of a few optical signal processing device functionalities on a CMOS compatible silicon-on-insulator material platform," said Yeshaiahu Fainman, a professor in the Department of Electrical and Computer Engineering in the UC San Diego Jacobs School of Engineering. Fainman acknowledged DARPA support in developing silicon photonics technologies which helped to enable this work, through programs such as Silicon-based Photonic Analog Signal Processing Engines with Reconfigurability (Si-PhASER) and Ultraperformance Nanophotonic Intrachip Communications (UNIC).

Pulse Compression for On-Chip Optical Interconnects

The compressed pulses are seven times shorter than the original -- the largest compression demonstrated to date on a chip.

Until now, pulse compression featuring such high compression factors was only possible using bulk optics or fiber-based systems, both of which are bulky and not practical for optical interconnects for computers and other electronics.

The combination of high compression and miniaturization are possible due to a nanoscale, light-guiding tool called an"integrated dispersive element" developed and designed primarily by electrical engineering Ph.D. candidate Dawn Tan.

The new dispersive element offers a much needed component to the on-chip nanophotonics tool kit.

The pulse compressor works in two steps. In step one, the spectrum of incoming laser light is broadened. For example, if green laser light were the input, the output would be red, green and blue laser light. In step two, the new integrated dispersive element developed by the electrical engineers manipulates the light so each spectrum in the pulse is travelling at the same speed. This speed synchronization is where pulse compression occurs.

Imagine the laser light as a series of cars. Looking down from above, the cars are initially in a long caravan. This is analogous to a long pulse of laser light. After stage one of pulse compression, the cars are no longer in a single line and they are moving at different speeds. Next, the cars move through the new dispersive grating where some cars are sped up and others are slowed down until each car is moving at the same speed. Viewed from above, the cars are all lined up and pass the finish line at the same moment.

This example illustrates how the on-chip pulse compressor transforms a long pulse of light into a spectrally broader and temporally shorter pulse of light. This temporally compressed pulse will enable multiplexing of data to achieve much higher data speeds.

"In communications, there is this technique called optical time division multiplexing or OTDM, where different signals are interleaved in time to produce a single data stream with higher data rates, on the order of terabytes per second. We've created a compression component that is essential for OTDM," said Tan.

The UC San Diego electrical engineers say they are the first to report a pulse compressor on a CMOS-compatible integrated platform that is strong enough for OTDM.

"In the future, this work will enable integrating multiple 'slow' bandwidth channels with pulse compression into a single ultra-high-bandwidth OTDM channel on a chip. Such aggregation devices will be critical for future inter- and intra-high speed digital electronic processors interconnections for numerous applications such as data centers, field-programmable gate arrays, high performance computing and more," said Fainman, holder of the Cymer Inc. Endowed Chair in Advanced Optical Technologies at the UC San Diego Jacobs School of Engineering and Deputy Director of the NSF-funded Center for Integrated Access Networks.

This work was supported by the Defense Advanced Research Projects Agency, the National Science Foundation (NSF) through Electrical, Communications and Cyber Systems (ECCS) grants, the NSF Center for Integrated Access Networks ERC, the Cymer Corporation and the U.S. Army Research Office.

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Methane-Powered Laptops? Materials Scientists Unveil Tiny, Low-Temperature Methane Fuel Cells

With advances in nanostructured devices, lower operating temperatures, and the use of an abundant fuel source and cheaper materials, a group of researchers led by Shriram Ramanathan at the Harvard School of Engineering and Applied Sciences (SEAS) are increasingly optimistic about the commercial viability of the technology.

Ramanathan, an expert and innovator in the development of solid-oxide fuel cells (SOFCs), says they may, in fact, soon become the go-to technology for those on the go.

Electrochemical fuel cells have long been viewed as a potential eco-friendly alternative to fossil fuels -- especially as most SOFCs leave behind little more than water as waste.

The obstacles to using SOFCs to charge laptops and phones or drive the next generation of cars and trucks have remained reliability, temperature, and cost.

Fuel cells operate by converting chemical energy (from hydrogen or a hydrocarbon fuel such as methane) into an electric current. Oxygen ions travel from the cathode through the electrolyte toward the anode, where they oxidize the fuel to produce a current of electrons back toward the cathode.

That may seem simple enough in principle, but until now, SOFCs have been more suited for the laboratory rather than the office or garage. In two studies appearing in theJournal of Power Sourcesthis month, Ramanathan's team reported several critical advances in SOFC technology that may quicken their pace to market.

In the first paper, Ramanathan's group demonstrated stable and functional all-ceramic thin-film SOFCs that do not contain any platinum.

In thin-film SOFCs, the electrolyte is reduced to a hundredth or even a thousandth of its usual scale, using densely packed layers of special ceramic films, each just nanometers in thickness. These micro-SOFCs usually incorporate platinum electrodes, but they can be expensive and unreliable.

"If you use porous metal electrodes," explains Ramanathan,"they tend to be inherently unstable over long periods of time. They start to agglomerate and create open circuits in the fuel cells."

Ramanathan's platinum-free micro-SOFC eliminates this problem, resulting in a win-win: lower cost and higher reliability.

In a second paper published this month, the team demonstrated a methane-fueled micro-SOFC operating at less than 500° Celsius, a feat that is relatively rare in the field.

Traditional SOFCs have been operating at about 800-1000°C, but such high temperatures are only practical for stationary power generation. In short, using them to power up a smartphone mid-commute is not feasible.

In recent years, materials scientists have been working to reduce the required operating temperature to about 300-500°C, a range Ramanathan calls the"sweet spot."

Moreover, when fuel cells operate at lower temperatures, material reliability is less critical -- allowing, for example, the use of less expensive ceramics and metallic interconnects -- and the start-up time can be shorter.

"Low temperature is a holy grail in this field," says Ramanathan."If you can realize high-performance solid-oxide fuel cells that operate in the 300-500°C range, you can use them in transportation vehicles and portable electronics, and with different types of fuels."

The use of methane, an abundant and cheap natural gas, in the team's SOFC was also of note. Until recently, hydrogen has been the primary fuel for SOFCs. Pure hydrogen, however, requires a greater amount of processing.

"It's expensive to make pure hydrogen," says Ramanathan,"and that severely limits the range of applications."

As methane begins to take over as the fuel of choice, the advances in temperature, reliability, and affordability should continue to reinforce each other.

"Future research at SEAS will explore new types of catalysts for methane SOFCs, with the goal of identifying affordable, earth-abundant materials that can help lower the operating temperature even further," adds Ramanathan.

Fuel cell research at SEAS is funded by the same NSF grant that enabled the"Robobees" project led by Robert J. Wood, Assistant Professor of Electrical Engineering. Wood and Ramanathan hope that micro-SOFCs will provide the tiny power source necessary to get the flying robots off the ground.

Ramanathan's co-authors on the papers were Bo Kuai Lai, a Research Associate at SEAS, and Ph.D. candidate Kian Kerman '14.

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New Breed of Space Vehicle: Researchers Developing Conceptual Design for a Mars 'Hopper'

Their research findings have been published this month by theProceedings of the Royal Society A.

Robots exploring Mars can carry scientific instruments that measure the physical and chemical characteristics of the Martian surface and subsurface, analyse the environment and look for evidence of past or present life. Wheeled rovers have made extraordinary discoveries despite only exploring a small fraction of the planet.

The research has an international flavour. The University of Leicester has been working with a number of collaborators including Astrium Ltd in the UK and Center for Space Nuclear Research, Idaho, USA. The focus in the UK has been the development of a large-scale (400 kg) Mars Hopper concept that can fly in 1km 'hops'. This is an exciting concept that should be considered further as a complement to rover and orbital missions.

The Hopper can collect fuel between hops by compressing gas from the Martian atmosphere and can fly quickly between sites, powered by a long-life radioisotope power source. It could therefore study hundreds of locations over a lifetime of several years.

The Leicester research focused on the rocket motor, looking at its size and materials.

Dr Richard Ambrosi, at the Leicester Space Research Centre, commented:

"The improved mobility and range of a hopping vehicle will tell us more about the evolution of Mars and of the Solar System and may answer questions as to whether there was life in the past, whether Mars was wetter in the past and if so where that water went."

Dr Nigel Bannister added:"The Hopper is different from other rovers because of its power source. In one mode the heat source generates electric power to drive a compressor to gather the carbon dioxide propellant from the Martian atmosphere. The heat source then stores thermal energy and injects it into the propellant, which is accelerated out of a rocket nozzle to provide thrust."

Dr Hugo Williams said:"At Leicester we have concentrated on the motor and design features which translate into the performance of the vehicle.

"Our findings have resulted in a hop range of 1km, for a relatively large vehicle with a large suite of scientific instruments on board. We also looked at the geometry and the best materials for the motor core.

"Our interest in the materials aspect is particularly relevant because we are also engaged in collaborative research with our colleagues in Materials Engineering here at Leicester, and Queen Mary University of London to explore how material properties of materials for use in the space nuclear systems of the future can be enhanced through novel processing and manufacturing techniques."

A Royal Society interview with Dr Richard Ambrosi, Dr Hugo Williams and Dr Nigel Bannister is available online at:http://rspa.royalsocietypublishing.org/content/early/2010/11/11/rspa.2010.0438/suppl/DC2

A video illustrating the concept of the Mars vehicle is available on YouTube at:http://www.youtube.com/watch?v=grffBimdwUg

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