Solar power could get boost from new light absorption design

ScienceDaily (Nov. 2, 2011) — Solar power may be on the rise, but solar cells are only as efficient as the amount of sunlight they collect. Under the direction of a new McCormick professor, researchers have developed a new material that absorbs a wide range of wavelengths and could lead to more efficient and less expensive solar technology.

A paper describing the findings, "Broadband polarization-independent resonant light absorption using ultrathin plasmonic super absorbers," was published November 1 in the journal Nature Communications.

"The solar spectrum is not like a laser -- it's very broadband, starting with UV and going up to near-infrared," said Koray Aydin, assistant professor of electrical engineering and computer science and the paper's lead author. "To capture this light most efficiently, a solar cell needs to have a broadband response. This design allows us to achieve that."

The researchers used two unconventional materials -- metal and silicon oxide -- to create thin but complex, trapezoid-shaped metal gratings on the nanoscale that can trap a wider range of visible light. The use of these materials is unusual because on their own, they do not absorb light; however, they worked together on the nanoscale to achieve very high absorption rates, Aydin said.

The uniquely shaped grating captured a wide range of wavelengths due to the local optical resonances, causing light to spend more time inside the material until it gets absorbed. This composite metamaterial was also able to collect light from many different angles -- a useful quality when dealing with sunlight, which hits solar cells at different angles as sun moves from east to west throughout the day.

This research is not directly applicable to solar cell technology because metal and silicon oxide cannot convert light to electricity; in fact, the photons are converted to heat and might allow novel ways to control the heat flow at the nanoscale. However, the innovative trapezoid shape could be replicated in semiconducting materials that could be used in solar cells, Aydin said.

If applied to semiconducting materials, the technology could lead to thinner, lower-cost, and more efficient solar cells, he said.

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The above story is reprinted from materials provided by Northwestern University. The original article was written by Sarah Ostman.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Koray Aydin, Vivian E. Ferry, Ryan M. Briggs, Harry A. Atwater. Broadband polarization-independent resonant light absorption using ultrathin plasmonic super absorbers. Nature Communications, 2011; 2: 517 DOI: 10.1038/ncomms1528

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Nature offers key lessons on harvesting solar power, say chemists

ScienceDaily (Sep. 24, 2011) — Clean solutions to human energy demands are essential to our future. While sunlight is the most abundant source of energy at our disposal, we have yet to learn how to capture, transfer and store solar energy efficiently. According to University of Toronto chemistry professor Greg Scholes, the answers can be found in the complex systems at work in nature.

"Solar fuel production often starts with the energy from light being absorbed by an assembly of molecules," said Scholes, the D.J. LeRoy Distinguished Professor at U of T. "The energy is stored fleetingly as vibrating electrons and then transferred to a suitable reactor. It is the same in biological systems. In photosynthesis, for example, antenna complexes composed of chlorophyll capture sunlight and direct the energy to special proteins called reaction centres that help make oxygen and sugars. It is like plugging those proteins into a solar power socket."

In an article in Nature Chemistry to be published Sept. 23, Scholes and colleagues from several other universities examine the latest research in various natural antenna complexes. Using lessons learned from these natural phenomena, they provide a framework for how to design light harvesting systems that will route the flow of energy in sophisticated ways and over long distances, providing a microscopic "energy grid" to regulate solar energy conversion.

A key challenge is that the energy from sunlight is captured by coloured molecules called dyes or pigments, but is stored for only a billionth of a second. This leaves little time to route the energy from pigments to molecular machinery that produces fuel or electricity. How can we harvest sunlight and utilize its energy before it is lost?

"This is why natural photosynthesis is so inspiring," said Scholes. "More than 10 million billion photons of light strike a leaf each second. Of these, almost every red-coloured photon is captured by chlorophyll pigments which feed plant growth." Learning the workings of these natural light-harvesting systems fostered a vision, proposed by Scholes and his co-authors, to design and demonstrate molecular "circuitry" that is 10 times smaller than the thinnest electrical wire in computer processors. These energy circuits could control, regulate, direct and amplify raw solar energy which has been captured by human-made pigments, thus preventing the loss of precious energy before it is utilized.

Last year, Scholes led a team that showed that marine algae, a normally functioning biological system, uses quantum mechanics in order to optimize photosynthesis, a process essential to its survival. These and other insights from the natural world promise to revolutionize our ability to harness the power of the sun.

"Lessons from nature about solar light harvesting" was written by Scholes, Graham Fleming of the University of California, Berkeley, Alexandra Olaya-Castro of University College, London UK and Rienk van Grondelle of VU University in Amsterdam, The Netherlands.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Toronto.

Journal Reference:

Gregory D. Scholes, Graham R. Fleming, Alexandra Olaya-Castro, Rienk van Grondelle. Lessons from nature about solar light harvesting. Nature Chemistry, 2011; 3 (10): 763 DOI: 10.1038/nchem.1145

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Nature offers key lessons on harvesting solar power, say chemists

ScienceDaily (Sep. 24, 2011) — Clean solutions to human energy demands are essential to our future. While sunlight is the most abundant source of energy at our disposal, we have yet to learn how to capture, transfer and store solar energy efficiently. According to University of Toronto chemistry professor Greg Scholes, the answers can be found in the complex systems at work in nature.

"Solar fuel production often starts with the energy from light being absorbed by an assembly of molecules," said Scholes, the D.J. LeRoy Distinguished Professor at U of T. "The energy is stored fleetingly as vibrating electrons and then transferred to a suitable reactor. It is the same in biological systems. In photosynthesis, for example, antenna complexes composed of chlorophyll capture sunlight and direct the energy to special proteins called reaction centres that help make oxygen and sugars. It is like plugging those proteins into a solar power socket."

In an article in Nature Chemistry to be published Sept. 23, Scholes and colleagues from several other universities examine the latest research in various natural antenna complexes. Using lessons learned from these natural phenomena, they provide a framework for how to design light harvesting systems that will route the flow of energy in sophisticated ways and over long distances, providing a microscopic "energy grid" to regulate solar energy conversion.

A key challenge is that the energy from sunlight is captured by coloured molecules called dyes or pigments, but is stored for only a billionth of a second. This leaves little time to route the energy from pigments to molecular machinery that produces fuel or electricity. How can we harvest sunlight and utilize its energy before it is lost?

"This is why natural photosynthesis is so inspiring," said Scholes. "More than 10 million billion photons of light strike a leaf each second. Of these, almost every red-coloured photon is captured by chlorophyll pigments which feed plant growth." Learning the workings of these natural light-harvesting systems fostered a vision, proposed by Scholes and his co-authors, to design and demonstrate molecular "circuitry" that is 10 times smaller than the thinnest electrical wire in computer processors. These energy circuits could control, regulate, direct and amplify raw solar energy which has been captured by human-made pigments, thus preventing the loss of precious energy before it is utilized.

Last year, Scholes led a team that showed that marine algae, a normally functioning biological system, uses quantum mechanics in order to optimize photosynthesis, a process essential to its survival. These and other insights from the natural world promise to revolutionize our ability to harness the power of the sun.

"Lessons from nature about solar light harvesting" was written by Scholes, Graham Fleming of the University of California, Berkeley, Alexandra Olaya-Castro of University College, London UK and Rienk van Grondelle of VU University in Amsterdam, The Netherlands.

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Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Toronto.

Journal Reference:

Gregory D. Scholes, Graham R. Fleming, Alexandra Olaya-Castro, Rienk van Grondelle. Lessons from nature about solar light harvesting. Nature Chemistry, 2011; 3 (10): 763 DOI: 10.1038/nchem.1145

Note: If no author is given, the source is cited instead.

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

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Miniature power plants for aircraft bodies

ScienceDaily (June 14, 2011) — Sensor networks are supposed to pervade the body shell of airplanes in the future -- much like a nervous system. Thanks to a joint research project of EADS Germany and the Vienna University of Technology, these sensors do not require any external power supply.

Aircraft maintenance can be time consuming and expensive. It is much simpler if the airplane itself reports, where maintenance is required. The best solution is a sensor system, which even has its own power supply and is therefore independent of electrical wiring -- and this is what has now been developed by EADS Germany, in cooperation with the Institute of Sensor and Actuator Systems at Vienna University of Technology (TU Vienna). For each individual sensor, electricity is produced by a thermoelectric generator with a small water tank, storing thermal energy. The electricity is simply generated from the temperature difference between the icy cold air in high altitudes and the air close to the ground. This new sensor technology could not only facilitate aircraft maintenance, but also increase comfort for travelers.

Energy from the "Energy Harvester Module"

Even small collisions can easily lead to damage in the body of the aircraft. On aluminum bodies, a slight dent may be visible -- but on modern carbon materials, it is much harder to detect damage. Tiny, invisible cracks may appear, which are very hard to detect. With suitable sensors connected directly to the body of the aircraft, this could be constantly monitored. "A major problem with these sensors is the energy supply. Wiring up hundreds of sensors in the aircraft body is complicated and expensive," professor Ulrich Schmid from the Institute for Sensor and Actuator Systems at TU Vienna explains. For this reason, he -- together with Dominik Samson and professor Thomas Becker (EADS Germany) -- developed the idea of the "thermoelectric energy harvester" as an energy source, in order to be completely independent of batteries and wiring.

Electrical Current from Differences in Temperature

When an airplane rises to an altitude of thousands of meters, the exterior wall cools down. "From the temperature difference between the exterior and the interior, we can harvest energy for the sensor element, using a thermoelectric generator," Dominik Samson explains. In the energy-harvester module, there is a little water tank which can store the ground temperature for a while. Water is especially well suited for this task, because it can store large quantities of energy in terms of heat. The inner part of the module with the water tank is connected to the cold exterior wall via the thermoelectric generator. Therefore, a gradient in temperature arises at the generator, which can be used to create electrical voltage. During landing, it works the other way around: The plane heats up again, whereas the inner part of the module is still cold -- and again, electricity can be produced.

Whenever there is no thermoelectric current, for instance right after takeoff and during the landing, sophisticated electronics controls storage and transfer of electrical energy. The electronics and the components which create electricity only take up very little space: They fit on the palm of a hand and can easily be integrated into the aircraft body. The size can be adjusted for the individual energy demand of different applications.

No Wires, no Batteries

The data collected by the sensor can be transmitted wirelessly. Wireless technology does not only make maintenance easier, it also minimizes potential causes of defect and it reduces the weight of the airplane. During one flight, the energy harvester can provide the energy of eight to ten milliwatt hours -- which is sufficient for a wireless sensor. "A plane has a durability of roughly thirty years. If the sensors were operated with batteries, each of them would use up about one hundred batteries during this time," Dominik Samson estimates. Using a large number of sensors, this would not only require costly maintenance but it would also create unnecessary amounts of waste.

The concept of generating electricity in the airplane by utilizing differences in temperature could also be used for other purposes. Sensors could monitor whether the passengers have fastened their seatbelts or whether the tables are in an upright position. At the push of a button, a wireless signal could be transmitted to the flight attendants -- without expensive and complicated wiring, just powered by the body heat of the passengers. "The first and most important step has been taken. We are confident that this wireless sensor technology will travel on board of many airplanes soon," Ulrich Schmid says.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Vienna University of Technology, TU Vienna, via AlphaGalileo.

Note: If no author is given, the source is cited instead.

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

View the original article here

Pocket Particle Accelerators Like This One Could Bring Safer Nuclear Power to Neighborhoods

Meet EMMA, the Electron Model of Many Applications
EMMA Installation Science and Technology Facilities Council-UK

A wee particle accelerator in the English countryside could be a harbinger of a safer, cleaner future of energy. Specifically, nuclear energy, but not the type that has wrought havoc in Japan and controversy throughout Europe and the U.S. It would be based on thorium, a radioactive element that is much more abundant, and much more safe, than traditional sources of nuclear power.

Some advocates believe small nuclear reactors powered by thorium could wean the world off coal and natural gas, and do it more safely than traditional nuclear. Thorium is not only abundant, but more efficient than uranium or coal — one ton of the silver metal can produce as much energy as 200 tons of uranium, or 3.5 million tons of coal, as the Mail on Sunday calculates it.

The newspaper took a tour of a small particle accelerator that could be used to power future thorium reactors. Nicknamed EMMA — the Electron Model of Many Applications — the accelerator would be used to jump-start fissile nuclear reactions inside a small-scale thorium power plant.

Thorium reactors would not melt down, in part because they require an external input to produce fission. Thorium atoms would release energy when bombarded by high-energy neutrons, such as the type supplied in a particle accelerator.

Providing that stimulus is one obstacle to building small thorium reactors — but a new generation of accelerators like EMMA, and someday potentially even smaller, luggage-sized ones — could do the job.

EMMA is the first non- scaling, fixed-field, alternating-gradient (NS-FFAG) accelerator, qualities that make it easier to operate and maintain, more reliable and compact, more flexible and more efficient, according to British researchers. Other particle accelerators use alternating electric fields, which require special safety measures to guard against microwave exposure, for instance. EMMA’s alternating magnetic field gradients are a more efficient and cheaper way to accelerate particles to higher energies. (Brookhaven National Laboratory explains in more detail here.)

EMMA operates at operates around 20 MeV, or 20 million electronvolts, a paltry amount for an atom accelerator. The Tevatron, for instance, accelerates particles to 1 tera-electron volts. The Large Hadron Collider is designed to speed them to 7 TeV. But thorium reactors would not need such high energies to initiate fusion.

British scientists are already working on a successor called PAMELA, the Particle Accelerator for Medical Applications, which will be used to treat cancer.

Click through to the Mail for a full tour of EMMA, its sister apparatus ALICE (Accelerators and Lasers In Combined Experiments), and a description of British efforts to produce thorium power.

[Mail on Sunday]

View the original article here

Miniature power plants for aircraft bodies

ScienceDaily (June 14, 2011) — Sensor networks are supposed to pervade the body shell of airplanes in the future -- much like a nervous system. Thanks to a joint research project of EADS Germany and the Vienna University of Technology, these sensors do not require any external power supply.

Aircraft maintenance can be time consuming and expensive. It is much simpler if the airplane itself reports, where maintenance is required. The best solution is a sensor system, which even has its own power supply and is therefore independent of electrical wiring -- and this is what has now been developed by EADS Germany, in cooperation with the Institute of Sensor and Actuator Systems at Vienna University of Technology (TU Vienna). For each individual sensor, electricity is produced by a thermoelectric generator with a small water tank, storing thermal energy. The electricity is simply generated from the temperature difference between the icy cold air in high altitudes and the air close to the ground. This new sensor technology could not only facilitate aircraft maintenance, but also increase comfort for travelers.

Energy from the "Energy Harvester Module"

Even small collisions can easily lead to damage in the body of the aircraft. On aluminum bodies, a slight dent may be visible -- but on modern carbon materials, it is much harder to detect damage. Tiny, invisible cracks may appear, which are very hard to detect. With suitable sensors connected directly to the body of the aircraft, this could be constantly monitored. "A major problem with these sensors is the energy supply. Wiring up hundreds of sensors in the aircraft body is complicated and expensive," professor Ulrich Schmid from the Institute for Sensor and Actuator Systems at TU Vienna explains. For this reason, he -- together with Dominik Samson and professor Thomas Becker (EADS Germany) -- developed the idea of the "thermoelectric energy harvester" as an energy source, in order to be completely independent of batteries and wiring.

Electrical Current from Differences in Temperature

When an airplane rises to an altitude of thousands of meters, the exterior wall cools down. "From the temperature difference between the exterior and the interior, we can harvest energy for the sensor element, using a thermoelectric generator," Dominik Samson explains. In the energy-harvester module, there is a little water tank which can store the ground temperature for a while. Water is especially well suited for this task, because it can store large quantities of energy in terms of heat. The inner part of the module with the water tank is connected to the cold exterior wall via the thermoelectric generator. Therefore, a gradient in temperature arises at the generator, which can be used to create electrical voltage. During landing, it works the other way around: The plane heats up again, whereas the inner part of the module is still cold -- and again, electricity can be produced.

Whenever there is no thermoelectric current, for instance right after takeoff and during the landing, sophisticated electronics controls storage and transfer of electrical energy. The electronics and the components which create electricity only take up very little space: They fit on the palm of a hand and can easily be integrated into the aircraft body. The size can be adjusted for the individual energy demand of different applications.

No Wires, no Batteries

The data collected by the sensor can be transmitted wirelessly. Wireless technology does not only make maintenance easier, it also minimizes potential causes of defect and it reduces the weight of the airplane. During one flight, the energy harvester can provide the energy of eight to ten milliwatt hours -- which is sufficient for a wireless sensor. "A plane has a durability of roughly thirty years. If the sensors were operated with batteries, each of them would use up about one hundred batteries during this time," Dominik Samson estimates. Using a large number of sensors, this would not only require costly maintenance but it would also create unnecessary amounts of waste.

The concept of generating electricity in the airplane by utilizing differences in temperature could also be used for other purposes. Sensors could monitor whether the passengers have fastened their seatbelts or whether the tables are in an upright position. At the push of a button, a wireless signal could be transmitted to the flight attendants -- without expensive and complicated wiring, just powered by the body heat of the passengers. "The first and most important step has been taken. We are confident that this wireless sensor technology will travel on board of many airplanes soon," Ulrich Schmid says.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Vienna University of Technology, TU Vienna, via AlphaGalileo.

Note: If no author is given, the source is cited instead.

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

View the original article here

Novel artificial material could facilitate wireless power

ScienceDaily (May 24, 2011) — Electrical engineers at Duke University have determined that unique artificial materials should theoretically make it possible to improve the power transfer to small devices, such as laptops or cell phones, or ultimately to larger ones, such as cars or elevators, without wires.

This advance is made possible by the recent ability to fabricate exotic composite materials known as metamaterials, which are not so much a single substance, but an entire human-made structure that can be engineered to exhibit properties not readily found in nature. In fact, the metamaterial used in earlier Duke studies, and which would likely be used in future wireless power transmission systems, resembles a miniature set of tan Venetian blinds.

Theoretically, this metamaterial can improve the efficiency of "recharging" devices without wires. As power passes from the transmitting device to the receiving device, most if not all of it scatters and dissipates unless the two devices are extremely close together. However, the metamaterial postulated by the Duke researchers, which would be situated between the energy source and the "recipient" device, greatly refocuses the energy transmitted and permits the energy to traverse the open space between with minimal loss of power.

"We currently have the ability to transmit small amounts of power over short distances, such as in radio frequency identification (RFID) devices," said Yaroslav Urzhumov, assistant research professor in electrical and computer engineering at Duke's Pratt School of Engineering. "However, larger amounts of energy, such as that seen in lasers or microwaves, would burn up anything in its path.

"Based on our calculations, it should be possible to use these novel metamaterials to increase the amount of power transmitted without the negative effects," Urzhumov said.

The results of the Duke research were published online in the journal Physical Review B. Urzhumov works in the laboratory of David R. Smith, William Bevan Professor of electrical and computer engineering at Pratt School of Engineering. Smith's team was the first demonstrate that similar metamaterials could act as a cloaking device in 2006.

Just as the metamaterial in the cloaking device appeared to make a volume of space "disappear," in the latest work, the metamaterial would make it seem as if there was no space between the transmitter and the recipient, Urzhumov said. Therefore, he said, the loss of power should be minimal.

Urzhumov's research is an offshoot of "superlens" research conducted in Smith's laboratory. Traditional lenses get their focusing power by controlling rays as they pass through the two outside surfaces of the lens. On the other hand, the superlens, which is in fact a metamaterial, directs waves within the bulk of the lens between the outside surfaces, giving researchers a much greater control over whatever passes through it.

The metamaterial used in wireless power transmission would likely be made of hundreds to thousands -- depending on the application -- of individual thin conducting loops arranged into an array. Each piece is made from the same copper-on-fiberglass substrate used in printed circuit boards, with excess copper etched away. These pieces can then be arranged in an almost infinite variety of configurations.

"The system would need to be tailored to the specific recipient device, in essence the source and target would need to be 'tuned' to each other," Urzhumov said. "This new understanding of how matematerials can be fabricated and arranged should help make the design of wireless power transmission systems more focused."

The analysis performed at Duke was inspired by recent studies at Mitsubishi Electric Research Labs (MERL), an industrial partner of the Duke Center for Metamaterials and Integrated Plasmonics. MERL is currently investigating metamaterials for wireless power transfer. The Duke researchers said that with these new insights into the effects of metamaterials, developing actual devices can be more targeted and efficient.

The Duke University research was supported by a Multidisciplinary University Research Initiative (MURI) grant through the Air Force Office of Scientific Research and the U.S. Army Research Office.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Duke University, via EurekAlert!, a service of AAAS.

Journal Reference:

Yaroslav Urzhumov, David Smith. Metamaterial-enhanced coupling between magnetic dipoles for efficient wireless power transfer. Physical Review B, 2011; 83 (20) DOI: 10.1103/PhysRevB.83.205114

Note: If no author is given, the source is cited instead.

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

View the original article here

Novel artificial material could facilitate wireless power

ScienceDaily (May 24, 2011) — Electrical engineers at Duke University have determined that unique artificial materials should theoretically make it possible to improve the power transfer to small devices, such as laptops or cell phones, or ultimately to larger ones, such as cars or elevators, without wires.

This advance is made possible by the recent ability to fabricate exotic composite materials known as metamaterials, which are not so much a single substance, but an entire human-made structure that can be engineered to exhibit properties not readily found in nature. In fact, the metamaterial used in earlier Duke studies, and which would likely be used in future wireless power transmission systems, resembles a miniature set of tan Venetian blinds.

Theoretically, this metamaterial can improve the efficiency of "recharging" devices without wires. As power passes from the transmitting device to the receiving device, most if not all of it scatters and dissipates unless the two devices are extremely close together. However, the metamaterial postulated by the Duke researchers, which would be situated between the energy source and the "recipient" device, greatly refocuses the energy transmitted and permits the energy to traverse the open space between with minimal loss of power.

"We currently have the ability to transmit small amounts of power over short distances, such as in radio frequency identification (RFID) devices," said Yaroslav Urzhumov, assistant research professor in electrical and computer engineering at Duke's Pratt School of Engineering. "However, larger amounts of energy, such as that seen in lasers or microwaves, would burn up anything in its path.

"Based on our calculations, it should be possible to use these novel metamaterials to increase the amount of power transmitted without the negative effects," Urzhumov said.

The results of the Duke research were published online in the journal Physical Review B. Urzhumov works in the laboratory of David R. Smith, William Bevan Professor of electrical and computer engineering at Pratt School of Engineering. Smith's team was the first demonstrate that similar metamaterials could act as a cloaking device in 2006.

Just as the metamaterial in the cloaking device appeared to make a volume of space "disappear," in the latest work, the metamaterial would make it seem as if there was no space between the transmitter and the recipient, Urzhumov said. Therefore, he said, the loss of power should be minimal.

Urzhumov's research is an offshoot of "superlens" research conducted in Smith's laboratory. Traditional lenses get their focusing power by controlling rays as they pass through the two outside surfaces of the lens. On the other hand, the superlens, which is in fact a metamaterial, directs waves within the bulk of the lens between the outside surfaces, giving researchers a much greater control over whatever passes through it.

The metamaterial used in wireless power transmission would likely be made of hundreds to thousands -- depending on the application -- of individual thin conducting loops arranged into an array. Each piece is made from the same copper-on-fiberglass substrate used in printed circuit boards, with excess copper etched away. These pieces can then be arranged in an almost infinite variety of configurations.

"The system would need to be tailored to the specific recipient device, in essence the source and target would need to be 'tuned' to each other," Urzhumov said. "This new understanding of how matematerials can be fabricated and arranged should help make the design of wireless power transmission systems more focused."

The analysis performed at Duke was inspired by recent studies at Mitsubishi Electric Research Labs (MERL), an industrial partner of the Duke Center for Metamaterials and Integrated Plasmonics. MERL is currently investigating metamaterials for wireless power transfer. The Duke researchers said that with these new insights into the effects of metamaterials, developing actual devices can be more targeted and efficient.

The Duke University research was supported by a Multidisciplinary University Research Initiative (MURI) grant through the Air Force Office of Scientific Research and the U.S. Army Research Office.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Duke University, via EurekAlert!, a service of AAAS.

Journal Reference:

Yaroslav Urzhumov, David Smith. Metamaterial-enhanced coupling between magnetic dipoles for efficient wireless power transfer. Physical Review B, 2011; 83 (20) DOI: 10.1103/PhysRevB.83.205114

Note: If no author is given, the source is cited instead.

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

View the original article here

Portable tech might provide drinking water, power to villages

ScienceDaily (May 4, 2011) — Researchers have developed an aluminum alloy that could be used in a new type of mobile technology to convert non-potable water into drinking water while also extracting hydrogen to generate electricity.

Such a technology might be used to provide power and drinking water to villages and also for military operations, said Jerry Woodall, a Purdue University distinguished professor of electrical and computer engineering.

The alloy contains aluminum, gallium, indium and tin. Immersing the alloy in freshwater or saltwater causes a spontaneous reaction, splitting the water into hydrogen and oxygen molecules. The hydrogen could then be fed to a fuel cell to generate electricity, producing water in the form of steam as a byproduct, he said.

"The steam would kill any bacteria contained in the water, and then it would condense to purified water," Woodall said. "So, you are converting undrinkable water to drinking water."

Because the technology works with saltwater, it might have marine applications, such as powering boats and robotic underwater vehicles. The technology also might be used to desalinate water, said Woodall, who is working with doctoral student Go Choi.

A patent on the design is pending.

Woodall envisions a new portable technology for regions that aren't connected to a power grid, such as villages in Africa and other remote areas.

"There is a big need for this sort of technology in places lacking connectivity to a power grid and where potable water is in short supply," he said. "Because aluminum is a low-cost, non-hazardous metal that is the third-most abundant metal on Earth, this technology promises to enable a global-scale potable water and power technology, especially for off-grid and remote locations."

The potable water could be produced for about $1 per gallon, and electricity could be generated for about 35 cents per kilowatt hour of energy.

"There is no other technology to compare it against, economically, but it's obvious that 34 cents per kilowatt hour is cheap compared to building a power plant and installing power lines, especially in remote areas," Woodall said.

The unit, including the alloy, the reactor and fuel cell might weigh less than 100 pounds.

"You could drop the alloy, a small reaction vessel and a fuel cell into a remote area via parachute," Woodall said. "Then the reactor could be assembled along with the fuel cell. The polluted water or the seawater would be added to the reactor and the reaction converts the aluminum and water into aluminum hydroxide, heat and hydrogen gas on demand."

The aluminum hydroxide waste is non-toxic and could be disposed of in a landfill.

The researchers have a design but haven't built a prototype.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Purdue University. The original article was written by Emil Venere.

Note: If no author is given, the source is cited instead.

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

View the original article here

Portable tech might provide drinking water, power to villages

ScienceDaily (May 4, 2011) — Researchers have developed an aluminum alloy that could be used in a new type of mobile technology to convert non-potable water into drinking water while also extracting hydrogen to generate electricity.

Such a technology might be used to provide power and drinking water to villages and also for military operations, said Jerry Woodall, a Purdue University distinguished professor of electrical and computer engineering.

The alloy contains aluminum, gallium, indium and tin. Immersing the alloy in freshwater or saltwater causes a spontaneous reaction, splitting the water into hydrogen and oxygen molecules. The hydrogen could then be fed to a fuel cell to generate electricity, producing water in the form of steam as a byproduct, he said.

"The steam would kill any bacteria contained in the water, and then it would condense to purified water," Woodall said. "So, you are converting undrinkable water to drinking water."

Because the technology works with saltwater, it might have marine applications, such as powering boats and robotic underwater vehicles. The technology also might be used to desalinate water, said Woodall, who is working with doctoral student Go Choi.

A patent on the design is pending.

Woodall envisions a new portable technology for regions that aren't connected to a power grid, such as villages in Africa and other remote areas.

"There is a big need for this sort of technology in places lacking connectivity to a power grid and where potable water is in short supply," he said. "Because aluminum is a low-cost, non-hazardous metal that is the third-most abundant metal on Earth, this technology promises to enable a global-scale potable water and power technology, especially for off-grid and remote locations."

The potable water could be produced for about $1 per gallon, and electricity could be generated for about 35 cents per kilowatt hour of energy.

"There is no other technology to compare it against, economically, but it's obvious that 34 cents per kilowatt hour is cheap compared to building a power plant and installing power lines, especially in remote areas," Woodall said.

The unit, including the alloy, the reactor and fuel cell might weigh less than 100 pounds.

"You could drop the alloy, a small reaction vessel and a fuel cell into a remote area via parachute," Woodall said. "Then the reactor could be assembled along with the fuel cell. The polluted water or the seawater would be added to the reactor and the reaction converts the aluminum and water into aluminum hydroxide, heat and hydrogen gas on demand."

The aluminum hydroxide waste is non-toxic and could be disposed of in a landfill.

The researchers have a design but haven't built a prototype.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Purdue University. The original article was written by Emil Venere.

Note: If no author is given, the source is cited instead.

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Portable tech might provide drinking water, power to villages

ScienceDaily (May 3, 2011) — Researchers have developed an aluminum alloy that could be used in a new type of mobile technology to convert non-potable water into drinking water while also extracting hydrogen to generate electricity.

Such a technology might be used to provide power and drinking water to villages and also for military operations, said Jerry Woodall, a Purdue University distinguished professor of electrical and computer engineering.

The alloy contains aluminum, gallium, indium and tin. Immersing the alloy in freshwater or saltwater causes a spontaneous reaction, splitting the water into hydrogen and oxygen molecules. The hydrogen could then be fed to a fuel cell to generate electricity, producing water in the form of steam as a byproduct, he said.

"The steam would kill any bacteria contained in the water, and then it would condense to purified water," Woodall said. "So, you are converting undrinkable water to drinking water."

Because the technology works with saltwater, it might have marine applications, such as powering boats and robotic underwater vehicles. The technology also might be used to desalinate water, said Woodall, who is working with doctoral student Go Choi.

A patent on the design is pending.

Woodall envisions a new portable technology for regions that aren't connected to a power grid, such as villages in Africa and other remote areas.

"There is a big need for this sort of technology in places lacking connectivity to a power grid and where potable water is in short supply," he said. "Because aluminum is a low-cost, non-hazardous metal that is the third-most abundant metal on Earth, this technology promises to enable a global-scale potable water and power technology, especially for off-grid and remote locations."

The potable water could be produced for about $1 per gallon, and electricity could be generated for about 35 cents per kilowatt hour of energy.

"There is no other technology to compare it against, economically, but it's obvious that 34 cents per kilowatt hour is cheap compared to building a power plant and installing power lines, especially in remote areas," Woodall said.

The unit, including the alloy, the reactor and fuel cell might weigh less than 100 pounds.

"You could drop the alloy, a small reaction vessel and a fuel cell into a remote area via parachute," Woodall said. "Then the reactor could be assembled along with the fuel cell. The polluted water or the seawater would be added to the reactor and the reaction converts the aluminum and water into aluminum hydroxide, heat and hydrogen gas on demand."

The aluminum hydroxide waste is non-toxic and could be disposed of in a landfill.

The researchers have a design but haven't built a prototype.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Purdue University. The original article was written by Emil Venere.

Note: If no author is given, the source is cited instead.

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

View the original article here

Solar power goes viral: Researchers use virus to improve solar-cell efficiency

ScienceDaily (Apr. 25, 2011) — Researchers at MIT have found a way to make significant improvements to the power-conversion efficiency of solar cells by enlisting the services of tiny viruses to perform detailed assembly work at the microscopic level.

In a solar cell, sunlight hits a light-harvesting material, causing it to release electrons that can be harnessed to produce an electric current. The new MIT research, published online in the journal Nature Nanotechnology, is based on findings that carbon nanotubes -- microscopic, hollow cylinders of pure carbon -- can enhance the efficiency of electron collection from a solar cell's surface.

Previous attempts to use the nanotubes, however, had been thwarted by two problems. First, the making of carbon nanotubes generally produces a mix of two types, some of which act as semiconductors (sometimes allowing an electric current to flow, sometimes not) or metals (which act like wires, allowing current to flow easily). The new research, for the first time, showed that the effects of these two types tend to be different, because the semiconducting nanotubes can enhance the performance of solar cells, but the metallic ones have the opposite effect. Second, nanotubes tend to clump together, which reduces their effectiveness.

And that's where viruses come to the rescue. Graduate students Xiangnan Dang and Hyunjung Yi -- working with Angela Belcher, the W. M. Keck Professor of Energy, and several other researchers -- found that a genetically engineered version of a virus called M13, which normally infects bacteria, can be used to control the arrangement of the nanotubes on a surface, keeping the tubes separate so they can't short out the circuits, and keeping the tubes apart so they don't clump.

The system the researchers tested used a type of solar cell known as dye-sensitized solar cells, a lightweight and inexpensive type where the active layer is composed of titanium dioxide, rather than the silicon used in conventional solar cells. But the same technique could be applied to other types as well, including quantum-dot and organic solar cells, the researchers say. In their tests, adding the virus-built structures enhanced the power conversion efficiency to 10.6 percent from 8 percent -- almost a one-third improvement.

This dramatic improvement takes place even though the viruses and the nanotubes make up only 0.1 percent by weight of the finished cell. "A little biology goes a long way," Belcher says. With further work, the researchers think they can ramp up the efficiency even further.

The viruses are used to help improve one particular step in the process of converting sunlight to electricity. In a solar cell, the first step is for the energy of the light to knock electrons loose from the solar-cell material (usually silicon); then, those electrons need to be funneled toward a collector, from which they can form a current that flows to charge a battery or power a device. After that, they return to the original material, where the cycle can start again. The new system is intended to enhance the efficiency of the second step, helping the electrons find their way: Adding the carbon nanotubes to the cell "provides a more direct path to the current collector," Belcher says.

The viruses actually perform two different functions in this process. First, they possess short proteins called peptides that can bind tightly to the carbon nanotubes, holding them in place and keeping them separated from each other. Each virus can hold five to 10 nanotubes, each of which is held firmly in place by about 300 of the virus's peptide molecules. In addition, the virus was engineered to produce a coating of titanium dioxide (TiO2), a key ingredient for dye-sensitized solar cells, over each of the nanotubes, putting the titanium dioxide in close proximity to the wire-like nanotubes that carry the electrons.

The two functions are carried out in succession by the same virus, whose activity is "switched" from one function to the next by changing the acidity of its environment. This switching feature is an important new capability that has been demonstrated for the first time in this research, Belcher says.

In addition, the viruses make the nanotubes soluble in water, which makes it possible to incorporate the nanotubes into the solar cell using a water-based process that works at room temperature.

Prashant Kamat, a professor of chemistry and biochemistry at Notre Dame University who has done extensive work on dye-sensitized solar cells, says that while others have attempted to use carbon nanotubes to improve solar cell efficiency, "the improvements observed in earlier studies were marginal," while the improvements by the MIT team using the virus assembly method are "impressive."

"It is likely that the virus template assembly has enabled the researchers to establish a better contact between the TiO2 nanoparticles and carbon nanotubes. Such close contact with TiO2 nanoparticles is essential to drive away the photo-generated electrons quickly and transport it efficiently to the collecting electrode surface."

Kamat thinks the process could well lead to a viable commercial product: "Dye-sensitized solar cells have already been commercialized in Japan, Korea and Taiwan," he says. If the addition of carbon nanotubes via the virus process can improve their efficiency, "the industry is likely to adopt such processes."

Belcher and her colleagues have previously used differently engineered versions of the same virus to enhance the performance of batteries and other devices, but the method used to enhance solar cell performance is quite different, she says.

Because the process would just add one simple step to a standard solar-cell manufacturing process, it should be quite easy to adapt existing production facilities and thus should be possible to implement relatively rapidly, Belcher says.

The research team also included Paula Hammond, the Bayer Professor of Chemical Engineering; Michael Strano, the Charles (1951) and Hilda Roddey Career Development Associate Professor of Chemical Engineering; and four other graduate students and postdoctoral researchers. The work was funded by the Italian company Eni, through the MIT Energy Initiative's Solar Futures Program.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Massachusetts Institute of Technology. The original article was written by David Chandler, MIT News Office.

Journal Reference:

Xiangnan Dang, Hyunjung Yi, Moon-Ho Ham, Jifa Qi, Dong Soo Yun, Rebecca Ladewski, Michael S. Strano, Paula T. Hammond, Angela M. Belcher. Virus-templated self-assembled single-walled carbon nanotubes for highly efficient electron collection in photovoltaic devices. Nature Nanotechnology, 2011; DOI: 10.1038/nnano.2011.50

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