A Better Way to Make Hydrogen?

A Purdue researcher claims aluminum alloys could make fuel-cell vehicles practical.

By Kevin Bullis

Gassing up: This aluminum alloy quickly pulls oxygen from water, in the process forming aluminum oxide and releasing hydrogen gas. The hydrogen could be used in place of gasoline in cars.
Credit: Jerry Woodall, Purdue University

A new process for using aluminum alloys to generate hydrogen from water could make fuel-cell vehicles more practical, says Jerry Woodall, a professor of electrical and computer engineering at Purdue.

Hydrogen fuel cells are attractive because they produce no harmful emissions, but hydrogen gas is hard to transport, and hydrogen vehicles have a limited range because it's difficult to store large amounts of hydrogen onboard. Many researchers are developing methods for storing more hydrogen, including packing it into carbon nanotubes or temporarily storing it in chemical compounds. Woodall's solution is to store hydrogen as water, splitting hydrogen from oxygen only when it's needed to power the vehicle.

Earlier this year, Woodall reported successfully generating significant amounts of hydrogen using a combination of aluminum and gallium. In those experiments, however, the alloy contained mostly gallium, which both limited the hydrogen-generating capacity of the material and kept costs high. At a nanotechnology conference on Friday, Woodall will present new work that shows that the process succeeds with an alloy containing 80 percent aluminum. This could make the system far more practical by reducing the amount of expensive gallium while increasing the amount of active material.

Woodall's process works because of aluminum's strong affinity for oxygen, which causes the metal to break water apart, forming aluminum oxide and releasing hydrogen. This basic chemical process is, of course, well known, but the problem has been that as soon as aluminum is exposed to air, it quickly forms a thin layer of aluminum oxide that seals off the bulk of the aluminum and prevents it from reacting with water. Woodall's insight, says Sunita Satyapal, who heads the Department of Energy's (DOE) hydrogen-storage program, is to use gallium to prevent this layer from completely sealing off the aluminum. Although the molecular mechanisms are still not understood, it's known that the gallium causes gaps in the oxide layer that allow the aluminum to react quickly with the oxygen in water, but not with the oxygen in air.

Woodall envisions a system in which aluminum pellets would be delivered to fueling stations where drivers would load about 50 kilograms of pellets and 20 kilograms of water into separate containers, with the two mixed as needed to generate hydrogen and aluminum oxide. (This would provide the equivalent of about 60 kilograms of gasoline, Woodall says.) The aluminum oxide can be recycled employing the same process used for aluminum cans, and the gallium can be easily separated from the aluminum oxide and used again.

But the electricity needed to recycle the aluminum could be a problem, since it would be a major source of pollution unless it comes from clean sources such as solar or wind. Also, Satyapal says that the energy efficiency of the process falls short of DOE goals.

The DOE, together with oil and car companies, has set goals for the amount of hydrogen that should be stored onboard a vehicle, aiming to provide the same range as gasoline-powered cars without changing vehicle designs or reducing cargo and passenger space. Woodall says that he can meet the goals for cars and other light vehicles, in part by recycling water produced by the fuel cells. The DOE, however, estimates that Woodall's process would take up too much room because, among other reasons, recycling water will likely not be practical, Satyapal says.

Woodall is working with AlGalCo, a startup based in West Lafayette, IN, to commercialize the process. The company's initial products will be fuel-cell generators that run on hydrogen produced with a version of his aluminum alloy.

Source: http://www.technologyreview.com

A Better Gauge on Battery Life

A new battery-gauge chip could make mobile phones more reliable and help them last longer on a single charge.
By Kevin Bullis

Credit: Istockphoto.com

Texas Instruments (TI), based in Dallas, has developed a battery-gauge chip that can tell mobile-phone users down to the minute how much talking or standby time they have left--a degree of accuracy much greater than that provided by existing battery gauges. Such a precise gauge could allow smart-phone developers to squeeze more energy out of the battery, potentially increasing by half or more the amount of time that it lasts between charges.
The new TI gauge is more accurate than today's gauges, which measure a battery's voltage, because it measures a number of electrical properties. Voltage-only-based gauges are erratic and unreliable because voltage doesn't fall steadily as the battery is discharged. What's more, the voltage changes as the battery ages and experiences different temperatures. It also varies with different power demands on the battery.
The TI gauge is more accurate--to within 1 percent of the actual energy left in the battery--because it measures electrical properties besides voltage. Most important, it measures a feature of battery cells that is at the root of the voltage changes that make today's gauges unreliable. This feature, called impedance, is a measure of the opposition to current flow, and it changes with temperature, battery age, and the power demands on a battery.
Knowing the changes in impedance allows the chip to reinterpret voltage changes, keeping it from being fooled by voltage changes caused by these factors. For example, when a person makes a call, the voltage drops as soon as the phone transmits the signal. A conventional gauge would interpret this as a sudden drop in the amount of energy left in the battery, which could engage battery-saving measures in power-management software. The new gauge would recognize that the cell still has plenty of energy. The approach also works with low voltages caused by cell age.
The new gauge chip, which is incorporated either into the circuit boards of a phone or directly into a battery pack, could be particularly useful in smart phones. Some phone users have to assume that after the gauge has reached the halfway point, the battery could die at any moment. What's more, poor battery gauges make it difficult to employ power-management software on phones that could extend battery capacity. Power-management software slows down processors, turns off the camera's flash, and dims the screen to save the battery once it's low. It may also save data and shut down applications just before the battery dies. Such software, however, may engage power-saving measures too soon if it relies on an inaccurate battery gauge, resulting in sluggish device performance while there is still plenty of charge.
The problem gets worse as the battery ages and, as the battery is depleted, voltage drops more quickly. With conventional gauges, this could trigger the phone to shut down when there is still quite a bit of energy left. Indeed, much of the perceived loss in battery life in older phones is actually just a problem with the battery gauge. "You can lose 30 percent of the energy in a battery simply because the device shuts itself down too early," says Richard DelRossi, an engineer at TI. He says that the new, more accurate battery gauge could increase the usable battery capacity by as much as 50 to 100 percent, depending on the power-management strategy.
Other phone and chip makers are also developing better battery gauges. Approaches taken by Motorola, based in Schaumburg, IL, and PowerPrecise, a chip maker based in Herndon, VA, that's funded by Intel, combine voltage data with current measurements to determine how much energy has been used. Subtracting the amount of energy used can give a good idea of how much is left, as long as it's known how much energy was there to start with. But the capacity of the battery, as with the voltage, depends on certain conditions, such as temperature, battery age, and power demand. To adjust for these factors, these systems can refer to models of battery behavior based on earlier tests to guess how these conditions will affect the battery's overall capacity. Such a system gives a much more accurate gauge of battery charge than do voltage measurements alone, says Jerry Hallmark, who heads Motorola's research on energy consumption in mobile devices.

Source: http://www.technologyreview.com

Tiny Device Stores Light

IBM researchers have fabricated a silicon device that's a significant advance in making practical optical interconnects.

By Prachi Patel-Predd
An SEM image of an optical-delay line that has up to 100 microrings, all connected to a common silicon nanowire. The optical buffer can store up to 10 optical bits.
Credit: IBM

By forcing light to circle multiple times through ring-shaped structures carved into silicon, researchers at IBM have been able to delay the flow of light on a microchip. Being able to delay light is crucial for high-performance, ultrafast optical computers of the future that will process information using light and electrical signals.

It's easy to store electronic data in computer memory; light is harder to control. The new silicon device, described in this week's issue of Nature Photonics, is ten times smaller than those made in the past. It also works much better at high data speeds. "This work is approximately a factor of ten over the best achieved with [ring-shaped devices] so far," says Keren Bergman, an electrical-engineering professor at Columbia University.

Storing light on silicon is key for electronic-optical hybrid computers that researchers believe will be available a decade from now. In these computers, devices will compute using electrons but will move data to other devices and components using light--avoiding the use of copper wires or interconnects that tend to heat up at high computer frequencies.

But the optical interconnects would have to be laid out in an intelligent network, just as the copper wires on today's chips are. To transfer data packets efficiently between devices, the copper network on a chip has nodes where many interconnects converge. If a processor is sending data to a logic circuit, the data travels from node to node until it gets to the logic circuit. Each node in the network reads and processes the data packet to route it correctly to the next node. While the node makes a routing decision, it temporarily stores the data in electronic memory. To process and route data at the nodes of an optical-interconnect network, one would need to store, or delay, light so the node can make the routing decision.

Yurii Vlasov and his colleagues at IBM's T.J. Watson Research Center delay light on a silicon microchip by circulating it 60 to 70 times through ring-shaped structures, called resonators. The researchers make these resonators on a thin silicon layer mounted on an insulting silicon-oxide layer. They etch parallel trenches into the silicon that reach down to the oxide. The raised portion between the trenches acts like a silicon wire that shuttles light.

The researchers employ the same silicon wafers and techniques that are used to fabricate microprocessors at IBM. This makes it easy to "think of combining optical circuitry with electrical circuitry on the same chip," Vlasov says.

By connecting many rings, the researchers can build up the delay. With 56 rings connected to a common silicon wire, they get the longest delay: about half a nanosecond--which amounts to storing 10 optical bits--at a data speed of 20 gigabits per second.

Other researchers have made resonators on silicon before. But the smallest resonators so far have been about 100 micrometers wide, and cascading tens of them yields a device that is a few millimeters long--too big to be integrated into an electronic circuit. The IBM researchers make rings that are 12 micrometers in diameter, and they can fit up to 100 ring resonators into an area that is less than one-tenth of a square millimeter.

The size of the device is a major advance, Bergman says: "It is very close to the kinds of densities you would like to have on chip for optical interconnects." Achieving a delay of 10 bits at gigabits-per-second speeds, which would be typical of the data speed that optical interconnects of the future would be handling, is a breakthrough, she says. "This is a major step towards making optical interconnects a reality."

The device loses more light than would be acceptable in practical circuits, and Vlasov says that he and his team are working to reduce these losses. Once they do that, he says, they could put thousands of resonators together to store even more optical bits. For practical optical interconnects, you would need to store hundreds and thousands of bits.

It might take another 10 years before we see optical interconnects in computers, but the IBM research shows that the technology is viable, says Risto Puhakka, president of market-research firm VLSI Research, in Santa Clara, CA. "There are legs on this technology, and it could eventually be integrated with current circuits into chips."

Source: http://www.technologyreview.com

Saving Power in Handhelds

Taking advantage of human error tolerance could make cell phones more energy efficient.

By Larry Hardesty
Credit: Sándor Kelemen, Istockphoto.com

With the advent of the Apple iPhone and its big, clear screen, the idea of using the morning commute to catch up on missed episodes of Lost became a lot more attractive. But video chews through a handheld's battery much faster than, say, playing MP3s does. In the most recent issue of the Association for Computing Machinery's Transactions on Embedded Computing Systems, researchers at the University of Maryland describe a simple way for multimedia devices to save power. In simulations, the researchers applied their technique to several common digital-signal-processing chores and found that, on average, it would cut power consumption by about two-thirds.

The premise of the technique, says Gang Qu, one of its developers, is that in multimedia applications, "the end user can tolerate some execution failure." Much digital video, for example, plays at a rate of 30 frames per second. But "in the old movie theaters, they played at 24 frames per second," Qu says. "That's about 80 percent. If you can get 80 percent of the frames consistently correct, human beings will not be able to tell you've made mistakes."

Unlike the movies in the old theaters, a digital video isn't stored on reels of wound plastic; it's stored as a sequence of 1s and 0s. That sequence is decoded as the video plays, and the decoding time can vary from one frame to the next. So digital media systems are designed to work rapidly enough that even the hardest-to-decode frames will be ready to be displayed on time.

Qu thinks that's a waste of processing power. If the viewer won't miss the extra six frames of video per second, there's no reason to decode them. Lower decoding standards would mean less work for the video player's processor, and thus lower power consumption.

The straightforward way to ensure a decoding rate of 80 percent would be to decode, say, eight frames in a row and ignore the next two. That approach--which Qu calls the "naive approach"--did introduce power savings in the Maryland researchers' simulations. The problem is that such a system doesn't distinguish frames that are hard to decode from those that are easy: if frame five is the hardest, the decoder will still plow through it; if frame nine is the easiest, the decoder will still skip it.

Qu and his colleagues wrote an algorithm that imposes a series of time limits on the decoding process; if any of the limits is exceeded, the decoding is aborted. "You set certain milestones," Qu says, "and you say, 'Okay, after this time I still haven't reached that first milestone, so it seems this is a hard task. Let me drop this one.'" Using statistics on the durations of particular tasks, the researchers can tune the algorithm to guarantee any desired completion rate.

Raj Rajkumar, director of the Real-Time and Multimedia Systems Laboratory at Carnegie Mellon University, mentions that his colleague John Lehoczky and the University of Wisconsin's Parmesh Ramanathan have investigated approaches similar to Qu's. But he says that Qu's work is "the logical extension of earlier work. I think that what Gang did is very useful." Ramanathan adds that with Qu's approach, "my guess is that there will be considerable savings in power consumption. I think one can save quite a bit."

Indeed, the Maryland researchers' algorithm fared well in simulations, offering a 54 percent energy savings over the naive approach. "If you are using the current approach, which is going to keep on decoding everything," Qu says, "we are going to probably consume only slightly more than one-third of that energy. That means you can probably extend the battery life by three times."

Qu is quick to point out that the researchers' simulations involved signals similar, but not identical, to video signals; real video decoding might not produce such dramatic results. On the other hand, Qu says that more-recent video-coding standards call for frame rates higher than 30 frames per second. That means the decoding rate could drop below 80 percent, saving even more power.

And the tested algorithms do accurately model cell-phone voice decoding. In some handheld devices--notably the iPhone--voice communication is almost as big a battery drain as video playback. Without the handy reference of a near-century of analog movies, however, user tolerance for error in voice is harder to gauge.

Qu says his and his colleagues' power-saving scheme could be implemented in either hardware or software, although in the near term, software would certainly be the cheaper option. He adds that the work has drawn some corporate interest, but that there are no plans to commercialize it at the moment. Nonetheless, "if we got some partners," Qu says, "if they have a top engineer trying to work with us, this could be done in half a year."

Source: http://www.technologyreview.com

Intel's New Strategy: Power Efficiency

Spurred by competitor AMD's rapid success, Intel is shifting its strategy toward more power-efficient microprocessors.

By Kate Greene

Amid increasing competition from Advanced Micro Devices (AMD), Intel is changing its chip-making philosophy: it's paying more attention to the power requirements of its microprocessors.

In July 2006, the chip-making giant will release a new microprocessor, called Core 2 Duo, designed for laptops and desktops. The new chip is based on Intel's current chip architecture, which replaced traditional single-core processing with two processing centers on a single chip. The company says that the Core 2 Duo will perform better than its current dual-core chip, and will be more energy-efficient, which could make laptop batteries last longer and desktop towers run cooler.

Paying attention to power consumption in microprocessors is a relatively new concept for the company, says Steve Pawlowski, a senior fellow at Intel, adding that the move may help Intel regain market share from its rival AMD. Historically, the most important metric in the industry has been processor performance -- the speed at which a processor can complete a task, such as calculating a spreadsheet. "We've always focused on performance at the expense of power [use]," Pawlowski says.

But basic changes have occurred in the PC market, which first led AMD, and now Intel, to rethink microprocessor designs. First, mobile devices have become the primary PC for many consumers -- who don't want a device that quickly drains a battery or gets too hot. Furthermore, as the size of transistors shrink, they're more likely to waste electricity through a physical process called "leakage," says Kevin McGrath, an AMD fellow -- and the more transistors on a chip, the more electricity is wasted.

AMD has been working on more-efficient microprocessors for several years, and now Intel is trying to level the playing field. Both Intel and AMD have tackled part of the problem by converting their chip line-ups to dual-core processors (see "Multicore Mania," December 2005), which turns out to be one way to increase efficiency. "Interestingly, going to multiple cores can be a very power-efficient way of computation," says Milo Martin, professor in the computer and information sciences department at the University of Pennsylvania.

Three aspects of multicore chips make them more efficient. First, when a chip has more than one core, the speed at which each core computes can be slowed down without impeding the speed of the entire chip. By slowing down the clock speed, explains Martin, engineers can decrease the computational rate of a single core by a factor of five, from one gigahertz to 200 megahertz, and the core consumes only one-30th of the power. Then, he says, even if five of those cores are assembled onto a single chip, only one-sixth of the power is consumed, yet the total computational rate of one gigahertz is maintained.

Second, smaller processor sizes reduce power consumption. The number of transistors each core has and the amount of silicon real-estate they take up determines the amount of power the core uses -- smaller processors have fewer transistors and thus use less power than larger processors. In a dual-core chip, the total number of transistors is greater than it is in a single-core chip, but each core has fewer transistors, making it more power efficient.

Third, some of the processor functions, such as controlling memory, can be shared between cores, so that each core consumes less energy by not performing a redundant task.

So transitioning to a multicore architecture is an obvious way to save power, and both Intel and AMD have done so. But they're looking at other ways to create efficiency. As Pawlowski explains, managing processors at the circuit and individual transistor level can also save power. For instance, specific circuits on a transistor are designated to control the manipulation of a photo or to play a DVD. When that circuit needs to be used, the transistors that comprise the circuit are turned on with a certain voltage. In a perfectly efficient chip, those transistors would turn on and off only when they're needed. However, even when a circuit is idle, its transistors are using a small voltage that slowly leaks out of the transistor, says Pawlowski. This leakage produces heat and wastes electricity.

While there is much overlap in the ways that AMD and Intel are approaching this problem of waste and leakage at the circuit level, their solutions are different. Intel is working to solve the problem by designating "sleep transistors" on a chip to micromanage the circuits in each core. These transistors completely turn off the voltage to transistors in circuits that are dormant.

AMD also puts portions of the processor to sleep, explains McGrath; but it does so by having an algorithm instruct the processor to go into various levels of sleep, by shutting down its clock speed so that standby computations aren't carried out as quickly. The algorithm "can ask a part to go into its lowest power state," he says, "there are five or six of these power states that are used depending on the load of the processor."

Intel has announced prices for its new energy-efficient chips -- they're less expensive than AMD's current offerings, which will put pressure on its rival. For Intel, though, the test of whether its power-saving chips can compete well against AMD's offerings won't come until its new processors hit the market.

Global 'sunscreen' has likely thinned

A new NASA study has found that an important counter-balance to the warming of our planet by greenhouse gases sunlight blocked by dust, pollution and other aerosol particles appears to have lost ground.

The thinning of Earths "sunscreen" of aerosols since the early 1990s could have given an extra push to the rise in global surface temperatures. The finding, published recently in the journal Science, may lead to an improved understanding of recent climate change. In a related study published last week, scientists found that the opposing forces of global warming and the cooling from aerosol-induced "global dimming" can occur at the same time.

"When more sunlight can get through the atmosphere and warm Earth's surface, you're going to have an effect on climate and temperature," said lead author Michael Mishchenko of NASA's Goddard Institute for Space Studies (GISS), New York. "Knowing what aerosols are doing globally gives us an important missing piece of the big picture of the forces at work on climate".

The study uses the longest uninterrupted satellite record of aerosols in the lower atmosphere, a unique set of global estimates funded by NASA. Scientists at GISS created the Global Aerosol Climatology Project by extracting a clear aerosol signal from satellite measurements originally designed to observe clouds and weather systems that date back to 1978. The resulting data show large, short-lived spikes in global aerosols caused by major volcanic eruptions in 1982 and 1991, but a gradual decline since about 1990. By 2005, global aerosols had dropped as much as 20 percent from the relatively stable level between 1986 and 1991.

The NASA study also sheds light on the puzzling observations by other scientists that the amount of sunlight reaching Earth's surface, which had been steadily declining in recent decades, suddenly started to rebound around 1990. This switch from a "global dimming" trend to a "brightening" trend happened just as global aerosol levels started to decline, Mishchenko said.

While the Science paper does not prove that aerosols are behind the recent dimming and brightening trends changes in cloud cover have not been ruled out another new research result supports that conclusion In a paper published March 8 in the American Geophysical Union's Geophysical Research Letters, a research team led by Anastasia Romanou of Columbia University's Department of Applied Physics and Mathematics, New York, also showed that the apparently opposing forces of global warming and global dimming can occur at the same time.

The GISS research team conducted the most comprehensive experiment to date using computer simulations of Earth's 20th-century climate to investigate the dimming trend. The combined results from nine state-of-the-art climate models, including three from GISS, showed that due to increasing greenhouse gases and aerosols, the planet warmed at the same time that direct solar radiation reaching the surface decreased. The dimming in the simulations closely matched actual measurements of sunlight declines recorded from the 1960s to 1990.

Further simulations using one of the Goddard climate models revealed that aerosols blocking sunlight or trapping some of the sun's heat high in the atmosphere were the major driver in 20th-century global dimming. "Much of the dimming trend over the Northern Hemisphere stems from these direct aerosol effects," Romanou said. "Aerosols have other effects that contribute to dimming, such as making clouds more reflective and longer-lasting. These effects were found to be almost as important as the direct effects".

The combined effect of global dimming and warming may account for why one of the major impacts of a warmer climate the spinning up of the water cycle of evaporation, more cloud formation and more rainfall has not yet been observed. "Less sunlight reaching the surface counteracts the effect of warmer air temperatures, so evaporation does not change very much," said Gavin Schmidt of GISS, a co-author of the paper. "Increased aerosols probably slowed the expected change in the hydrological cycle".

Whether the recent decline in global aerosols will continue is an open question. A major complicating factor is that aerosols are not uniformly distributed across the world and come from many different sources, some natural and some produced by humans. While global estimates of total aerosols are improving and being extended with new observations by NASA's latest generation of Earth-observing satellites, finding out whether the recent rise and fall of aerosols is due to human activity or natural changes will have to await the planned launch of NASA's Glory Mission in 2008.

"One of Glory's two instruments, the Aerosol Polarimetry Sensor, will have the unique ability to measure globally the properties of natural and human-made aerosols to unprecedented levels of accuracy," said Mishchenko, who is project scientist on the mission.


Posted by: Brooke Source

Sound Waves to Ignite Sun's Ring of Fire

Researchers have found that the sun's magnetic field allows the release of wave energy from its interior, permitting sound waves to travel through thin fountains, or "spicules", upward and into the chromosphere. The chromosphere is the region of the sun that looks like a red ring of fire during an eclipse.
Credit: Zina Deretsky, National Science Foundation

Sound waves escaping the sun's interior create fountains of hot gas that shape and power a thin region of the sun's atmosphere which appears as a ruby red "ring of fire" around the moon during a total solar eclipse, as per research funded by the National Science Foundation (NSF) and NASA.

The results are presented today at the American Astronomical Society's Solar Physics Division meeting in Hawaii.

This region, called the chromosphere because of its color, is largely responsible for the deep ultraviolet radiation that bathes the Earth, producing the atmosphere's ozone layer.

It also has the strongest solar connection to climate variability.

"The sun's interior vibrates with the peal of millions of bells, but the bells are all on the inside of the building," said Scott McIntosh of the Southwest Research Institute in Boulder, Colo., lead member of the research team. "We've been able to show how the sound can escape the building and travel a long way using the magnetic field as a guide".

The new result also helps explain a mystery that's existed since the middle of the last century -- why the sun's chromosphere (and the corona above) is much hotter than the visible surface of the star. "It's getting warmer as you move away from the fire instead of cooler, certainly not what you would expect," said McIntosh.

"Researchers have long realized that observations of solar magnetic fields are the keys that will unlock the secrets of the sun's interior," said Paul Bellaire, program director in NSF's division of atmospheric sciences, which funded the research. "These scientists have found an ingenious way of using magnetic keys to pick those locks".

Using spacecraft, ground-based telescopes, and computer simulations, the results show that the sun's magnetic field allows the release of wave energy from its interior, permitting the sound waves to travel through thin fountains upward and into the solar chromosphere. The magnetic fountains form the mold for the chromosphere.

Scientists say that it's like standing in Yellowstone National Park and being surrounded by musical geysers that pop up at random, sending out shrill sound waves and hot water shooting high into the air.

"This work finds the missing piece of the puzzle that has fascinated a number of generations of solar astronomers," said Alexei Pevtsov, program scientist at NASA. "If you fit this piece into place, the whole picture of chromosphere heating becomes more clear".

Over the past twenty years, researchers have studied energetic sound waves as probes of the Sun's interior because the waves are largely trapped by the sun's visible surface -- the photosphere. The research observed that some of these waves can escape the photosphere into the chromosphere and corona.

To make the discovery, the team used observations from the SOHO and TRACE spacecraft combined with those from the Magneto-Optical filters at Two Heights, or MOTH, instrument in Antarctica, and the Swedish 1-meter Solar Telescope on the Canary Islands.

The observations gave detailed insights into how some of the trapped waves and their pent-up energy manage to leak out through magnetic "cracks" in the photosphere, sending mass and energy shooting upwards into the atmosphere above.

By analyzing motions of the solar atmosphere in detail, the researchers found that where there are strong knots in the Sun's magnetic field, sound waves from the interior can leak out and propagate upward into its atmosphere.

"The constantly evolving magnetic field above the solar surface acts like a doorman opening and closing the door for the waves that are constantly passing by," said Bart De Pontieu, a scientist at the Lockheed Martin Solar and Astrophysics Laboratory in Palo Alto, Calif.

These results were confirmed by state-of-the-art computer simulations that show how the leaking waves propel fountains of hot gas upward into the sun's atmosphere, and fall back to its surface a few minutes later.

Other research team members are Stuart Jeffries of the University of Hawaii and Viggo Hansteen of the University of Oslo and the Lockheed Martin Solar and Astrophysics Laboratory.


Posted by: Brooke Source

Life elsewhere in Solar System

The search for life elsewhere in the solar system and beyond should include efforts to detect what researchers sometimes refer to as "weird" life -- that is, life with an alternative biochemistry to that of life on Earth -- says a new report from the National Research Council. The committee that wrote the report observed that the fundamental requirements for life as we generally know it -- a liquid water biosolvent, carbon-based metabolism, molecular system capable of evolution, and the ability to exchange energy with the environment -- are not the only ways to support phenomena recognized as life. "Our investigation made clear that life is possible in forms different than those on Earth," said committee chair John Baross, professor of oceanography at the University of Washington, Seattle.

The report emphasizes that "no discovery that we can make in our exploration of the solar system would have greater impact on our view of our position in the cosmos, or be more inspiring, than the discovery of an alien life form, even a primitive one. At the same time, it is clear that nothing would be more tragic in the American exploration of space than to encounter alien life without recognizing it".

The tacit assumption that alien life would utilize the same biochemical architecture as life on Earth does means that researchers have artificially limited the scope of their thinking as to where extraterrestrial life might be found, the report says. The assumption that life requires water, for example, has limited thinking about likely habitats on Mars to those places where liquid water is believed to be present or have once flowed, such as the deep subsurface. However, as per the committee, liquids such as ammonia or formamide could also work as biosolvents -- liquids that dissolve substances within an organism -- albeit through a different biochemistry. The recent evidence that liquid water-ammonia mixtures may exist in the interior of Saturn's moon Titan suggests that increased priority be given to a follow-on mission to probe Titan, a locale the committee considers the solar system's most likely home for weird life.

"It is critical to know what to look for in the search for life in the solar system," said Baross. "The search so far has focused on Earth-like life because that's all we know, but life that may have originated elsewhere could be unrecognizable compared with life here. Advances throughout the last decade in biology and biochemistry show that the basic requirements for life might not be as concrete as we thought".

Besides the possibility of alternative biosolvents, studies show that variations on some of the other basic tenets for life also might be able to support weird life. DNA on Earth works through the pairing of four chemical compounds called nucleotides, but experiments in synthetic biology have created structures with six or more nucleotides that can also encode genetic information and, potentially, support Darwinian evolution. Additionally, studies in chemistry show that an organism could utilize energy from alternative sources, such as through a reaction of sodium hydroxide and hydrochloric acid, meaning that such an organism could have an entirely non-carbon-based metabolism.

Scientists need to further explore variations of the requirements for life with particular emphasis on origin-of-life studies, which will help determine if life can exist without water or in environments where water is only present under extreme conditions, the report says. Most planets and moons in this solar system fall into one of these categories. Research should also focus on how organisms break down key elements, as even non-carbon-based life would need elements for energy, structure, and chemical reactions.

The report also stresses that the future search for alien life should not exclude additional research into terrestrial life. Through examination of extreme environments, such as deserts and deep under the oceans, studies have determined that life exists essentially anywhere water and a source of energy are found together on Earth. Field scientists should therefore seek out organisms with novel biochemistries and those that exist in areas where vital resources are scarce to better understand how life on Earth truly operates, the committee said. This improved understanding will contribute greatly toward seeking Earth-like life where the conditions necessary for its existence might be met, as in the case of subsurface Mars.

Space missions will need adjustment to increase the breadth of their search for life. Planned Mars missions, for example, should include instruments that detect components of light elements -- particularly carbon, hydrogen, oxygen, phosphorous, and sulfur -- as well as simple organic functional groups and organic carbon. Recent evidence indicates that another moon of Saturn, Enceladus, has active water geysers, raising the prospect that habitable environments may exist there and greatly increasing the priority of additional studies of this body.


Posted by: Jaison Source

Silicon Lasers Get Up to Speed

A new silicon-based laser emits the short, high-frequency light pulses that are necessary for today's telecommunications networks.

By Kate Greene
Scintillating silicon: This image illustrates the design for a new hybrid silicon laser. The gray and orange base consists of two layers of silicon sandwiching a layer of silicon dioxide. Indium phosphide, the light-emitting material, is bonded to the top of the silicon with a thin layer of glass glue. Emitted photons bounce back and forth in a channel etched into the top layer of silicon, until they emerge as laser light.
Credit: Peter Allen, University of California, Santa Barbara

Researchers at the University of California, Santa Barbara (UCSB), have designed a silicon-based laser that emits ultrashort pulses of light at high frequencies--two characteristics that are crucial if silicon-based lasers are to become practical. Eventually, the researchers hope that the new laser could replace other, more expensive lasers in optical communication networks. It could even lead to faster computers that shuttle data around using light instead of electricity.

Modern telecommunications networks use three distinct gadgets--lasers, modulators, and detectors--to produce, encode, and detect light. Currently, all three are made of nonsilicon semiconductors, such as indium phosphide, that are difficult to mass-produce; as a consequence, they tend to be expensive and bulky. But if they could instead be made from silicon, they could be integrated on individual chips, says John Bowers, professor of electrical and computer engineering at UCSB. Devices that currently cost hundreds of dollars each could then be made in bulk for pennies, and the cost of bandwidth would plummet. The one snag in the plan is that it's hard to make silicon produce light.

In September 2006, however, the UCSB team and Intel announced a new hybrid laser that, although it still used indium phosphide, was built on a silicon base. (See "Bringing Light to Silicon.") The manufacture of the device began with a wafer that consisted of a layer of silicon dioxide sandwiched between two layers of silicon. In the top layer of silicon, the researchers etched a channel, called a waveguide, within which light bounced back and forth. To the top of the wafer, they bonded strips of indium phosphide, using a layer of glass glue only 25 atoms thick. Adding this additional layer, says Bowers, isn't much different from adding layers of other materials to silicon, something that's regularly done in today's manufacturing process.

To turn the laser on, the researchers applied electrical current to metal contacts on top of the indium phosphide. Indium phosphide is a naturally light-emitting material, so the strips of it on top of the wafer produced photons that got trapped in the channel below, bouncing back and forth along the length of the silicon waveguide. In certain materials, that bouncing is enough to amplify normal light into laser light, but not in silicon. So the device was designed to let a small amount of light, called the evanescent tail, sneak back into the indium phosphide, where it was amplified. The benefit of this design is that it avoids the costly fabrication of an indium-phosphide waveguide.

For the new laser, which is described in a recent issue of Optics Express, the researchers made their design slightly more complex. "We needed to turn it into a device with multiple sections," explains Alexander Fang, a graduate student who worked on the project. He says that he had to make sure the lengths of the cavities were precise, and that regions that amplified light and absorbed light were electrically isolated from each other.

The result is a laser that emits picosecond pulses of light at a frequency of 40 gigahertz. "This thing puts out short pulses of light, which is what you need for high-speed communication," says Bowers. "If you pulse at 40 gigahertz and combine that with a modulator [which puts information onto the light], then you have a light source."

The work "represents some nice progress toward proving a laser source on a silicon wafer," says Ivan Kaminow, professor of electrical engineering and computer science at the University of California, Berkeley, but he cautions that silicon photonics still has a long way to go. "Silicon is not an optimum photonic material," he says. "The hybrid approach is a compromise and, as such, is far from optimum performance." For instance, the hybrid laser can't operate at the same high temperatures that silicon circuits do.

Bowers agrees that there is still work to be done, and improving the device's temperature threshold is on the list. "This is pretty far-out research," he says. "Our goal last year was just to make a good laser on silicon, and now we're expanding that not just to do lasers, but photonic integrated-circuit technology." He suspects that silicon photonic devices based on his group's approach could appear in products as early as 2012.

Networking the Hudson River

The Hudson could become the world's largest environmental-monitoring system.

By Brittany Sauser
Modeling the Hudson: A new data acquisition and analysis system from IBM will receive data from a network of sensors distributed throughout the Hudson River. The system will examine the data and prioritize it, learning to recognize patterns and trends and automatically focusing resources on areas of interest. The system also includes visualization technologies that, fed with mapping data, can synthesize a virtual river, as shown above. This 3-D model will let researchers observe what is happening in the river in real time and track changes in the ecosystem.
Credit: The Beacon Institute

IBM and the Beacon Institute, a nonprofit scientific-research organization in Beacon, NY, have announced a collaboration with several other research institutions to create an environmental-monitoring system for New York's Hudson River. Their plan is to turn all 315 miles of the river into a distributed network of sensors that will collect biological, physical, and chemical information and transmit it to a central location, where it will be analyzed by IBM's new data acquisition and analysis system. According to John Cronin, CEO of the Beacon Institute, the project is now in its "design phase," which should be complete within a year and a half to two years.

The network's sensors will be deployed in a variety of ways. Some will be mounted on a new robotic underwater vehicle developed by Rensselaer Polytechnic Institute (RPI) and the Woods Hole Oceanographic Institute, both collaborators on the project; the vehicle will be powered by solar cells and can operate either autonomously or under human remote control. Other sensors will be suspended from buoys or fixed in place along the riverbed.

"In terms of having an integrated network of sensors, and given the magnitude of it for the Hudson River, this project is without a doubt a huge advancement and on a much larger scale than anything that has been done before," says Sandra Nierzwicki-Bauer, director of the Darrin Fresh Water Institute at RPI and a member of the science-research committee at the Beacon Institute.

The scale of the network and the variety of its sensors will demand a massive new data-analysis system, which IBM will provide. Comprising both distributed-processing hardware and analytical software, the system is designed to take heterogeneous data from a variety of sources and make sense of it in real time. The software learns to recognize data patterns and trends and prioritizes useful data. If some data stream begins to exhibit even minor variations, the system automatically redirects resources toward it. The system will also be equipped with IBM's visualization technologies; fed with mapping data, they can create a virtual model of the river and simulate its ecosystem in real time.

The IBM system "enables us to do a great deal of work in the area of data integration and data management for very large values and different types of data," says Harry Kolar, Global Alliance executive at IBM. "Another reason we are working in this sensor area is that we can actually build end-to-end solutions, meaning from the smallest device to a large back-end system."

Sensor networks to monitor everything from sewage systems to battlefields have been under development for many years, at companies like Intel, Sun, and Siemens and at academic institutions like the University of California, Los Angeles. But what the "research community has not had is the making-meaning part," says David Culler, a professor of computer science at the University of California, Berkeley. That's what the IBM system is intended to provide.

"A lot of what the research community has been focused on is getting sensors and delivering them through reliable, energy-efficient networks to the computing infrastructure," says Culler. "But once you have the data, what do you do with it, and how do you sort it?"

Much of the data the IBM system will be called upon to sort will be sensor reports on temperature, pressure, salinity, dissolved oxygen content, and pH levels, which will indicate whether pollutants have entered the river. Other sensors will be directed toward sea life, says Nierzwicki-Bauer, and will be used to study species and determine how communities of microscopic organisms change over time.

The exact number of sensors, their types, and their specific locations along the river have not yet been determined. But Cronin says that the sensors will easily number in the many hundreds, and the collaborators plan to develop new sensors along the way. IBM is also working to interconnect the sensors. According to Kolar, fiber-optic cables will be used in some cases and wireless connections in others, depending on Beacon's research requirements. And since the Hudson River flows into the Atlantic Ocean, the river network will be designed with the idea of connecting it to oceanic observatory networks as well.

For Beacon, the project is an opportunity to extract new information from the ecosystem of the river and estuary in order to resolve environmental and policy issues. And what makes the Hudson an unusual subject for environmental monitoring--as well as a challenge to network--is that it is host to lots of human activity, says Cronin. The river is used by tankers, tugboats, barges, recreational vessels, and fishermen, and it's a source of drinking water for six communities. It is also an energy source for sewage treatment plants and industries along the river--in addition to being a home for marine life.

Once the monitoring system is in place, Beacon hopes to extend its efforts globally to create the same type of 24-hour monitoring system in developing countries where rivers are vital to local communities. IBM sees this as a unique opportunity to test and refine some of its advanced hardware and software, as well as develop new technologies for this particular application.

Culler is excited to see IBM involved in an environmental project. "I expect that you are now going to see quite a significant second wave of this [sensor network] technology. We were all really excited about it in 2003, and now in 2007 it is really mature enough that vision can come to reality."

Harvesting Power from the Ocean

A new technology could generate electricity from waves.

By Kevin Bullis

Wave power: A buoy that generates electricity from the motion of waves. The clear cylinder in the middle of the buoy (see bottom image) contains a roll of rubberlike material that stretches and contracts as the buoy bobs up and down, separating and bringing together electrodes.
Credit: SRI International

Researchers from SRI International, based in Menlo Park, CA, recently completed the first ocean tests of a system that uses a so-called artificial muscle to generate power from the motion of a buoy riding up and down on the waves. Although the prototype produces very little electricity, the researchers say that wave farms based on the technology could eventually rival wind turbines in power output, providing a significant source of clean energy.

Technology for harnessing the ocean's energy already exists, but it has not been widely adopted, largely because it has trouble withstanding the pounding of the waves. The new system could prove both cheaper and more reliable, the researchers say.

Earlier systems used more-conventional electromagnetic devices, such as dynamos with complex transmissions, hydraulic pistons, and turbines. The gears of a transmission, in particular, are vulnerable to wear and tear from the erratic surging of ocean waves.

In contrast, the SRI system is not much more than a sheet of rubber attached to a weight. It has "the mechanical complexity of a rubber band," says SRI senior researcher Roy Kornbluh. As a consequence, it is better able to absorb the shock of waves, says Yoseph Bar-Cohen, a senior research scientist at NASA's Jet Propulsion Laboratory, in Pasadena, CA. What's more, Bar-Cohen adds, the materials that the system is made from are cheap, which could help it compete in price with other sources of electricity.

The polymer-based system at the heart of the new generator is a variation on an artificial muscle--a device developed as an alternative to electric motors in applications such as robots. An artificial muscle will expand or contract when a voltage is applied to it, but the same process can work in reverse: if the muscle is stretched by an outside force, it can generate electricity. A few years ago, SRI developed a small device that, embedded in the heel of a shoe, enabled the wearer to charge a cell phone simply by walking. The wave-harvesting system is basically a larger version of the same technology.

The SRI researchers built their generator by sandwiching a commercially available rubbery material between two electrodes, which are themselves made of a greasy polymer containing conductive materials. The rubber sheet and electrodes are then rolled up, like a scroll, to form a hollow tube. When the tube is pulled by an outside force, the rubber layer is stretched thin, narrowing the gap between the electrodes. Initially, a small battery applies a voltage across the electrodes; when the rubber springs back into its original shape, it forces the electrodes apart, increasing the voltage between them. This excess energy can be siphoned off to generate a current. Part of that current feeds back into the system, so the battery is used only for the first cycle.

The researchers recently tested the system off the coast of Florida. A couple of square meters of rubber rolled into the shape of a hollow tube were attached to a weight and mounted at the center of a buoy. As the buoy bobs in the water, it causes the weight to rise and fall, repeatedly stretching the rubber and allowing it to rebound, generating electricity.

So far, this prototype produces only about five watts of power--enough for a small light bulb. But because the rubber is thin--about 0.1 millimeters thick--it's possible to roll up much more of it and still fit it into the same buoy. A bundle of rubber about a meter long and half a meter thick, with optimized electronics and an improved buoy design, could generate a kilowatt of electricity, Kornbluh says. A string of buoys or larger floating structures could then generate appreciable amounts of electricity. (A thousand buoys could power about 750 houses.) An alternative design could involve submerged sheets of rubber that generate power as the force of currents or tides makes them flap back and forth. Such a system might prove more resilient than the turbines recently used in the East River in New York: their mechanical parts proved unable to withstand tidal forces.

The SRI system produces high voltages, in the range of a kilovolt. That was a problem for the shoe generator, which required a transformer to decrease the voltage enough that it wouldn't fry cell phones and other devices but still had to fit in a shoe. But for the buoy application, high voltage is an advantage, since it makes it more efficient to transmit electricity back to shore along underwater cables. The main challenge moving forward, the researchers say, is to develop a reliable manufacturing process. Their recent tests of the system also underscored the importance of designing new buoys that respond to waves in the best way for generating power. And they'll need to design electronics that, by varying the voltage across the polymer, can modify the stiffness of the system to adapt to different weather conditions.

The system's first commercial applications will likely be in systems for powering navigation, communications, and sensor buoys, and these could come within two years, Kornbluh estimates. But it could be five to ten years before the system can be ramped up for large-scale electricity generation.

"It's very exciting," says Ray Baughman, a professor of chemistry at the University of Texas at Dallas. "It's a promising direction for harvesting energy, not only for remote devices in the ocean but also perhaps for larger-scale energy harvesting."

Silicon Nanocrystals for Superefficient Solar Cells

Research shows that silicon can wring two electrons from each photon of incoming light.

By Kevin Bullis
Souped-up silicon: A micrograph of a seven-nanometer chunk of crystalline silicon, called a nanocrystal or quantum dot. Such structures could dramatically increase the efficiency of solar cells.
Credit: Arthur Nozik, National Renewable Energy Laboratory

A typical solar cell generates only one electron per photon of incoming sunlight. Some exotic materials are thought to produce multiple electrons per photon, but for the first time, the same effect has been seen in silicon. Researchers at the National Renewable Energy Laboratory (NREL), in Golden, CO, showed that silicon nanocrystals can produce two or three electrons per photon of high-energy sunlight. The effect, they say, could lead to a new type of solar cell that is both cheap and more than twice as efficient as today's typical photovoltaics.

As in earlier work with other materials, the extra electrons come from photons of blue and ultraviolet light, which have much more energy than those from the rest of the solar spectrum, especially red and infrared light. In most solar cells, the extra energy in blue and ultraviolet light is wasted as heat. But the small size of nanoscale crystals, also called quantum dots, leads to novel quantum-mechanical effects that convert this energy into electrons instead.

By generating multiple electrons from high-energy photons, solar cells made of silicon nanocrystals could theoretically convert more than 40 percent of the energy in light into electrical power, says Arthur Nozik, a senior research fellow at NREL. In contrast, today's flat rooftop solar panels are at best just over 20 percent efficient and are theoretically limited to about 30 percent efficiency. Concentrating sunlight with mirrors or lenses could raise that figure to about 40 percent, but the same approach could boost the efficiency of a silicon-nanocrystal solar cell to well over 60 percent, Nozik says.

What's more, solar cells made of silicon nanocrystals could prove to be cheap, giving them a significant advantage over other approaches to high-efficiency solar cells. For example, advanced "multijunction" cells have shown efficiencies of more than 40 percent. But these require complicated manufacturing processes that combine expensive semiconductors optimized for different parts of the solar spectrum. Silicon nanocrystals, in contrast, are relatively easy to make, even compared with the material in conventional solar cells, the best of which are made of very large, single crystals of silicon.

Silicon nanocrystals also have marked advantages over the other nanocrystal materials that have shown the multielectron effect. Some of these materials contain toxic elements such as lead or cadmium, and others rely on elements such as indium that are in limited supply. But silicon is both safe and abundant. It's also well studied, says Christiana Honsberg, professor of electrical and computer engineering at the University of Delaware, so engineers know how to work with it to make solar cells. Indeed, for many of the same reasons, silicon is by far the most common material in solar cells today, and it's attractive as the basis for broader deployment of photovoltaics in the future.

Before the NREL work, researchers had believed that silicon crystals small enough to produce the multielectron effect would be impractical as a photovoltaic material. At the nanoscale, the optical properties of silicon change so that it converts less light from the red end of the spectrum into electrons. As a result, any gains from more efficiently converting blue and ultraviolet light would be offset. Nozik and his colleagues found that the nanocrystals did not have to be as small as was previously thought, skirting this problem.

To be sure, the NREL work is only a first step. Making solar cells that take advantage of multielectron generation is a challenge. That's because the extra electrons are very short-lived, making it difficult to extract them from the nanocrystals to generate an electrical current. Indeed, this has proved so difficult that evidence of the effect has come from indirect methods such as spectroscopy rather than from current generated by a solar cell. The use of the indirect measures has led some prominent experts to question whether the extra electrons are actually being produced, although Nozik says that the effect has been confirmed using multiple techniques. Nozik and his colleagues are now working to make solar cells out of silicon nanocrystals--they're exploring a number of novel designs--and he says they've recently made direct measurements indicating that their cells are releasing multiple electrons per photon absorbed. (Their results have yet to be published.)

Honsberg is cautiously optimistic, calling the finding of the multiple-electron effect in silicon nanocrystals a breakthrough, but only "one breakthrough out of maybe three or four" needed to produce cheap, superefficient solar cells.

A Wirelessly Powered Lightbulb

Researchers at MIT have created a revolutionary device that could remotely charge batteries and power household appliances.

By Kate Greene
Cutting the cord: MIT researchers have shown that it’s possible to wirelessly power a 60-watt lightbulb from two meters away. Above, a coil (background) creates a magnetic field that is able to pass through an obstruction. The foreground coil resonates at the frequency of the magnetic field, picking up its energy to power the bulb.
Credit: Science

Researchers at MIT have shown that it's possible to wirelessly power a 60-watt lightbulb sitting about two meters away from a power source. Using a remarkably simple setup--basically consisting of two metal coils--they have demonstrated, for the first time, that it is feasible to efficiently send that much power over such a distance. The experiment paves the way for wirelessly charging batteries in laptops, mobile phones, and music players, as well as cutting the electric cords on household appliances, says Marin Soljačić, professor of physics at MIT, who led the team with physics professor John Joannopoulos.

The research, published in the June 7 edition of Science Express (the online publication of Science magazine), is the experimental demonstration of a theory outlined last November by the MIT team. (See "Charging Batteries without Wires.") "We had strong confidence in the theory," says Soljačić. "And experiment indeed confirmed that this worked as predicted."

The setup is straightforward, explains Andre Kurs, an MIT graduate student and the lead author of the paper. Two copper helices, with diameters of 60 centimeters, are separated from each other by a distance of about two meters. One is connected to a power source--effectively plugged into a wall--and the other is connected to a lightbulb waiting to be turned on. When the power from the wall is turned on, electricity from the first metal coil creates a magnetic field around that coil. The coil attached to the lightbulb picks up the magnetic field, which in turn creates a current within the second coil, turning on the bulb.

This type of energy transfer is similar to a well-known phenomenon called magnetic inductive coupling, used in power transformers. However, the MIT scheme is somewhat different because it's based on something called resonant coupling. Transformer coils can only transfer power when they are centimeters apart--any farther, and the magnetic fields don't affect each other in the same way. In order for the MIT researchers to achieve the range of two meters, explains Soljačić, they used coils that resonate at a frequency of 10 megahertz. When the electrical current flows through the first coil, it produces a 10-megahertz magnetic field; since the second coil resonates at this same frequency, it's able to pick up on the field, even from relatively far away. If the second coil resonated at a different frequency, the energy from the first coil would have been ignored.

The researchers' approach, says Soljačić, also makes the energy transfer efficient. If they were to emit power from an antenna in the same way that information is wirelessly transmitted, most of the power would be wasted as it radiates away in all directions. Indeed, with the method used to transfer information, it would be difficult to send enough energy to be useful for powering gadgets. In contrast, the researchers use what's known as nonradiative energy that is bound up near the coils. In this first demonstration, they showed that the scheme can transfer power with an efficiency of 45 percent.

Wireless power transfer is an idea that's more than 100 years old. In the 1890s, physicist and electrical engineer Nikola Tesla proposed beaming electricity through the air. However, soon thereafter, power cables became the commonly accepted means of transporting electricity across distances. But with the widespread adoption of small, portable devices with batteries in need of constant recharging, people's attention is again turning to wireless power. In fact, the startup Powercast, based in Ligonier, PA, has, using a different approach from that of the MIT team, developed a wireless power system that can transmit low wattages across a distance of about a meter. To start, the company is targeting devices with low power consumption, such as sensors, but it's hoping to ramp up to more power-hungry gadgets in the future.

One concern that people might have, says Sir John Pendry, professor of physics at Imperial College in London, is health effects. "There will be safety issues, real or imagined," he says. "After all, the power has to pass through space in some form or other, and pass through any bodies lying in its path. The [MIT] team has minimized this problem by making sure that the power is mainly in the form of a magnetic field, a form of energy to which the body is almost entirely insensitive."

Based on calculations, Soljačić believes that the scheme is safe, even for people with implanted medical devices, such as pacemakers. Although the researchers have not made a detailed study to test how the system interferes with pacemakers, Soljačić says that they don't expect it to interact strongly with objects that don't resonate at the same frequencies used to transfer power.

At this point, the team has applied for a number of patents and is planning to commercialize the technology, although the researchers expect that it could take a few years before devices with such wireless power systems will make it to consumers. In the meantime, the team is exploring different materials and alternate coil geometries to try to extend the range and ramp up the power.

Wireless Power

New physics theory could cut the cord on power chargers for gadgets.

By Kate Greene

One night in 2002, MIT physicist Marin Soljacˇic´ heard the chirps of his cell phone letting him know that its battery was losing the last of its juice. Annoyed, he began to wonder if there were any physics principles that would allow the phone's battery to be charged in a more convenient way. Over the next three years, Soljacˇic´, graduate student Aristeidis Karalis, and physics professor John Joannopoulos worked on and off to devise a theoretical scheme for charging gadgets wirelessly.

"We are very good at transmitting information wirelessly," says Soljacˇic´. But it's been much more difficult to transmit power in the same way, because the radiation spreads out, and most of it is lost in the environment. Soljacˇic´ and his team propose developing a power "base station" that would plug into a wall, much like a Wi-Fi base station; but it would emit great energy at close range. Theoretically, when devices such as mobile phones or laptops came within range of the power base station, they would pick up its energy.

In the 1890s, before power cables commonly transported electricity over great distances, physicist and electrical engineer Nikola Tesla proposed beaming it through the air. Today, a form of wireless energy transfer called inductive coupling is used to charge electric toothbrushes. Electricity flowing through the wires in a toothbrush's base station produces a magnetic field; that field induces a current in the wires of a nearby toothbrush handle, charging the toothbrush's battery. This technique has limited range, however.

In his wireless energy system, explains Soljacˇic´, the base station would fill a space with a low-­frequency electromagnetic field in the range of a few megahertz. A gadget would be equipped with a receiver, like the power-­harvesting circuits used in RFID tags to collect ambient energy. Soljacˇic´'s circuit would be designed to resonate at the same frequency as the radiation emitted by the power station. When the device came within a couple of meters of the station, circuitry would absorb the energy, charging the device's battery. The system could even power household electronics like televisions and toasters.

Most of the radiation emitted from the base station would stay in the vi­cinity, in a surrounding sphere with a radius of only a couple of meters. Soljacˇic´ says his calculations, and the known health effects of the proposed radio waves, suggest that his wireless power scheme poses no threat to people or other living things.

While the work is still in the realm of theory, Soljacˇic´ has applied for patents, and the group is working on an experimental demonstration. Soljacˇic´ says that he envisions houses with power hubs on the ceiling of each room. Then, as long as a mobile phone is inside, it will be charging, not chirping, through the night.

Charging Batteries without Wires

New MIT research reveals a way to send wireless energy to mobile phones and laptops.

By Kate Greene

Small, battery-powered gadgets make powerful computing portable. Unfortunately, there's still a continual need to recharge the batteries of phones, laptops, cameras, and MP3 players by hooking them up to a tangle of wires. Now researchers at MIT have proposed a way to cut the cords by wirelessly supplying power to devices.

"We are very good at transmitting information wirelessly," says Marin Soljačić, professor of physics at MIT. But, he says, historically, it's been much more difficult to transmit energy to power devices in the same way. Soljačić, who was a 2006 TR35 winner (see "2006 Young Innovator"), and MIT colleagues Aristeidis Karalis and John Joannopoulos have worked out a theoretical scheme for a wireless-energy transfer that could charge or power devices within a couple of meters of a small power "base station" plugged into an electrical outlet. They presented the approach on Tuesday at the American Institute of Physics's Industrial Physics Forum, in San Francisco.

The idea of beaming power through the air has been around for nearly two centuries, and it is used to some extent today to power some types of radio-frequency identification (RFID) tags. The phenomenon behind this sort of wireless-energy transfer is called inductive coupling, and it occurs when an electric current passes through wires in, for instance, an RFID reader. When the current flows, it produces a magnetic field around the wires; the magnetic field in turn induces a current in a nearby wire in, for example, an RFID tag. This technique has limited range, however, and because of this, it wouldn't be well suited for powering a roomful of gadgets.

To create a mid-range wireless-energy solution, the researchers propose an entirely new scheme. In it, a power base station would be plugged into an electrical outlet and emit low-frequency electromagnetic radiation in the range of 4 to 10 megahertz, explains Soljačić. A receiver within a gadget--such as a power-harvesting circuit--can be designed to resonate at the same frequency emitted by the power station. When it comes within a couple of meters of the station, it absorbs the energy. But to a nonresonant device, the radiation is undetectable.

Importantly, the energy that's accessed by the device is nonradiative--that is, it doesn't propagate over great distances. This is due to the low frequency of the radio waves, says John Pendry, professor of physics at Imperial College, in London. Electromagnetic radiation comes in two flavors: near-field and far-field. The intensity of low-frequency radiation drops quickly as a person moves farther away from the base station. In other words, the far-field radiation that propagates out in all directions isn't very strong at low frequencies, hence is essentially useless. (Wi-Fi signals, in comparison, are able to remain strong for tens of meters because they operate at a higher frequency of 2.4 gigahertz.)

However, the near-field radiation, which stays close to the base station, contains quite a bit of energy. "If you don't do anything with it, it just sits there," says Pendry. "It doesn't leak away." This bound-up energy, which extends for a couple of meters, is extracted when a resonant receiver on a gadget comes within range.

At this point, the work is still theoretical, but the researchers have filed patents and are working to build a prototype system that might be ready within a year. Even without a prototype, though, the physics behind the concept is sound, says Freeman Dyson, professor of physics at the Institute for Advanced Study, in Princeton, NJ. "It's a nice idea and I have no reason to believe that it won't work."

Pendry suspects that people might be squeamish about the idea of wireless energy radiating throughout the air. "Whenever there's powerful energy sources, people worry about safety," he says. Depending on the application, he says, either the electric or the magnetic portion of the near-field radiation could be handy. Using the electric field would pose a health risk, and would be better employed in applications in which people aren't nearby, he says. Conversely, using the magnetic field would be much safer and could be implemented just as easily. "I can't think of any reason to worry [about health concerns]," he says, "but people will."

Soljačić also suspects that the wireless power systems would be safe, based on his calculations and on the known health effects of low-frequency radio waves.

Ideally, says Soljačić, the system would be about 50 percent as efficient as plugging into an outlet, which would mean that charging a device might take longer. But the vision for this sort of wireless-energy setup, he says, is to place power hubs on the ceiling of each room in the house so that a phone or laptop can be constantly charging from any location in a home.

A More Efficient Engine

A new type of engine could be relatively inexpensive.

By Kevin Bullis

A new version of the internal combustion engine, which could significantly cut gas consumption, might be surprisingly practical and easy to deploy, according to recent findings by researchers at MIT. Tests on a prototype based on the technology, which allows engines to switch between conventional technology and the new gas-saving type of combustion, show that it does not require a special fuel, and engines using the technology can be cheaply made out of conventional auto parts.

The gas-saving technology, called homogeneous charge compression ignition, or HCCI, uses a form of combustion that is much more efficient than conventional spark ignition. Under some conditions, it can reduce fuel consumption by 25 percent, says William Green, a professor of chemical engineering at MIT who was coauthor of the new study. That's very similar to the efficiency of a diesel engine, which also achieves combustion by compression rather than a spark. But unlike diesel engines, HCCI results in a more uniform combustion and is thus much cleaner. A system that combines HCCI with conventional combustion could improve fuel economy by a few miles per gallon on average, Green says.

Several research groups are working on the new type of combustion. Volvo, for example, has built a hybrid system that can switch between conventional spark ignition and HCCI. Some experts, however, had expected that the new type of engine would require special fuel.

The MIT research shows that an HCCI engine can operate with any of the varieties of gasoline sold in North America, making a special fuel unnecessary. The researchers tested a range of different gasolines made at different refineries. They found that the HCCI engine "was less sensitive to the fuel than people had feared," says Green.

While the HCCI has several performance limitations, these can be addressed using a hybrid approach, in which an engine could switch between HCCI and conventional spark ignition. Using already mass-produced parts could make it relatively inexpensive to build such a hybrid, Green says.

In conventional gasoline engines, a spark ignites a mixture of fuel and air in a combustion chamber, creating an explosion that drives a piston. While this happens very efficiently when the engine is working hard, it's less efficient at lower loads, such as during cruising, when less gasoline is being pumped into the combustion chamber. At these times, to keep the ratio of fuel to oxygen optimized, a partial vacuum is created in the chamber. It takes extra energy to make this vacuum, which decreases the engine's efficiency.

The HCCI technology avoids the use of an energy-wasting vacuum. Instead, hot gases from a previous combustion cycle remain in the chamber; the engine uses a combination of heat from these hot gases and heat generated by compressing the mixture to raise temperatures high enough that the mixture explodes.

But if the engine's temperature is too low, such as when it's being started or being operated under very low loads, the mixture doesn't get hot enough to combust. And at high loads, when the temperature is high, the mixture can combust too early, out of sync with the cycling of the engine, causing a potentially damaging phenomenon called knock. Differences in fuels can also affect precisely when the mixture combusts.

The hybrid system switches between the two forms of combustion. To do this requires changing the way the engine deals with combusted gases. During spark combustion, the gases are forced out through an open valve. In HCCI, the timing of the opening of that valve is changed so that it closes before the gases completely escape, trapping them inside.

John Heywood, a professor of mechanical engineering at MIT who was not involved with this work, says that HCCI could eventually provide even greater benefits as researchers find ways to adapt the engine so that they can use it for a wider range of loads. What's more, it could be used in combination with other gas-saving technologies already available on many vehicles. The extent to which HCCI can be combined with other approaches could determine how widely it's adopted, suggests Heywood.

Global Warming Video

Global Warming
July 2006
Scientists speak out about the threat and how to deal with it.
(6min 10sec)

Source: http://www.technologyreview.com/

Mining the Moon

Lab experiments suggest that future fusion reactors could use helium-3 gathered from the moon.
By Mark Williams

Hot gases: Researchers at the University of Wisconsin-Madison’s Fusion Technology Institute are testing this fusion reactor, shown with a view of the grid in which interial electrostatic confinement takes place. Credit: Fusion Technology Institute-University of Wisconsin-Madison


At the 21st century's start, few would have predicted that by 2007, a second race for the moon would be under way. Yet the signs are that this is now the case. Furthermore, in today's moon race, unlike the one that took place between the United States and the U.S.S.R. in the 1960s, a full roster of 21st-century global powers, including China and India, are competing.
Even more surprising is that one reason for much of the interest appears to be plans to mine helium-3--purportedly an ideal fuel for fusion reactors but almost unavailable on Earth--from the moon's surface. NASA's Vision for Space Exploration has U.S. astronauts scheduled to be back on the moon in 2020 and permanently staffing a base there by 2024. While the U.S. space agency has neither announced nor denied any desire to mine helium-3, it has nevertheless placed advocates of mining He3 in influential positions. For its part, Russia claims that the aim of any lunar program of its own--for what it's worth, the rocket corporation Energia recently started blustering, Soviet-style, that it will build a permanent moon base by 2015-2020--will be extracting He3.
The Chinese, too, apparently believe that helium-3 from the moon can enable fusion plants on Earth. This fall, the People's Republic expects to orbit a satellite around the moon and then land an unmanned vehicle there in 2011.
Nor does India intend to be left out. (See "India's Space Ambitions Soar.") This past spring, its president, A.P.J. Kalam, and its prime minister, Manmohan Singh, made major speeches asserting that, besides constructing giant solar collectors in orbit and on the moon, the world's largest democracy likewise intends to mine He3 from the lunar surface. India's probe, Chandrayaan-1, will take off next year, and ISRO, the Indian Space Research Organization, is talking about sending Chandrayaan-2, a surface rover, in 2010 or 2011. Simultaneously, Japan and Germany are also making noises about launching their own moon missions at around that time, and talking up the possibility of mining He3 and bringing it back to fuel fusion-based nuclear reactors on Earth.
Could He3 from the moon truly be a feasible solution to our power needs on Earth? Practical nuclear fusion is nowadays projected to be five decades off--the same prediction that was made at the 1958 Atoms for Peace conference in Brussels. If fusion power's arrival date has remained constantly 50 years away since 1958, why would helium-3 suddenly make fusion power more feasible?
Advocates of He3-based fusion point to the fact that current efforts to develop fusion-based power generation, like the ITER megaproject, use the deuterium-tritium fuel cycle, which is problematical. (See "International Fusion Research.") Deuterium and tritium are both hydrogen isotopes, and when they're fused in a superheated plasma, two nuclei come together to create a helium nucleus--consisting of two protons and two neutrons--and a high-energy neutron. A deuterium-tritium fusion reaction releases 80 percent of its energy in a stream of high-energy neutrons, which are highly destructive for anything they hit, including a reactor's containment vessel. Since tritium is highly radioactive, that makes containment a big problem as structures weaken and need to be replaced. Thus, whatever materials are used in a deuterium-tritium fusion power plant will have to endure serious punishment. And if that's achievable, when that fusion reactor is eventually decommissioned, there will still be a lot of radioactive waste.
Helium-3 advocates claim that it, conversely, would be nonradioactive, obviating all those problems. But a serious critic has charged that in reality, He3-based fusion isn't even a feasible option. In the August issue of Physics World, theoretical physicist Frank Close, at Oxford in the UK, has published an article called "Fears Over Factoids" in which, among other things, he summarizes some claims of the "helium aficionados," then dismisses those claims as essentially fantasy.
Close points out that in a tokamak--a machine that generates a doughnut-shaped magnetic field to confine the superheated plasmas necessary for fusion--deuterium reacts up to 100 times more slowly with helium-3 than it does with tritium. In a plasma contained in a tokamak, Close stresses, all the nuclei in the fuel get mixed together, so what's most probable is that two deuterium nuclei will rapidly fuse and produce a tritium nucleus and proton. That tritium, in turn, will likely fuse with deuterium and finally yield one helium-4 atom and a neutron. In short, Close says, if helium-3 is mined from the moon and brought to Earth, in a standard tokamak the final result will still be deuterium-tritium fusion.
Second, Close rejects the claim that two helium-3 nuclei could realistically be made to fuse with each other to produce deuterium, an alpha particle and energy. That reaction occurs even more slowly than deuterium-tritium fusion, and the fuel would have to be heated to impractically high temperatures--six times the heat of the sun's interior, by some calculations--that would be beyond the reach of any tokamak. Hence, Close concludes, "the lunar-helium-3 story is, to my mind, moonshine."
So, is He3-based fusion untenable? In fact, Close is correct in his claims about how impracticable both deuterium-helium-3 fusion and pure helium-3 fusion in tokamak-based reactors would be. But there might be alternatives. For example, Gerald Kulcinski, a professor of nuclear engineering at the University of Wisconsin-Madison, has maintained the only helium-3 fusion reactor in the world on an annual budget that's barely into six figures.
Kulcinski's He3-based fusion reactor, located in the Fusion Technology Institute at the University of Wisconsin, is very small. When running, it contains a spherical plasma roughly 10 centimeters in diameter that can produce sustained fusion with 200 million reactions per second. To produce a milliwatt of power, unfortunately, the reactor consumes a kilowatt. Close's response is, therefore, valid enough: "When practical fusion occurs with a demonstrated net power output, I--and the world's fusion community--can take note."
Still, that critique applies equally to ITER and the tokamak-based reactor effort, which also haven't yet achieved breakeven (the point at which a fusion reactor produces as much energy as it consumes). What's significant about the reactor in Wisconsin is that, as Kulcinski says, "We are doing both deuterium-He3 and He3-He3 reactions. We run deuterium-He3 fusion reactions daily, so we are very familiar with that reaction. We are also doing He3-He3 because if we can control that, it will have immense potential."
The reactor at the Fusion Technology Institute uses a technology called inertial electrostatic confinement (IEC). Kulcinski explains: "If we used a tokamak to do deuterium-helium-3, it would need to be bigger than the ITER device, which already is stretching the bounds of credibility. Our IEC devices, on the other hand, are tabletop-sized, and during our deuterium-He3 runs, we do get some neutrons produced by side reaction with deuterium." Nevertheless, Kulcinski continues, when side reactions occur that involve two deuterium nuclei fusing to produce a tritium nucleus and proton, the tritium produced is at such a higher energy level than the confinement system that it immediately escapes. "Consequently, the radioactivity in our deuterium-He3 system is only 2 percent of the radioactivity in a deuterium-tritium system."
More significant is the He3-He3 fusion reaction that Kulcinski and his assistants produce with their IEC-based reactor. In Kulcinski's reactor, two helium-3 nuclei, each with two protons and one neutron, instead fuse to produce one helium-4 nucleus, consisting of two protons and two neutrons, and two highly energetic protons.
"He3-He3 is not an easy reaction to promote," Kulcinski says. "But He3-He3 fusion has the greatest potential." That's because helium-3, unlike tritium, is nonradioactive, which, first, means that Kulcinski's reactor doesn't need the massive containment vessel that deuterium-tritium fusion requires. Second, the protons it produces--unlike the neutrons produced by deuterium-tritium reactions--possess charges and can be contained using electric and magnetic fields, which in turn results in direct electricity generation. Kulcinski says that one of his graduate assistants at the Fusion Technology Institute is working on a solid-state device to capture the protons and convert their energy directly into electricity.
Still, Kulcinski's reactor proves only the theoretical feasibility and advantages of He3-He3 fusion, with commercial viability lying decades in the future. "Currently," he says, "the Department of Energy will tell us, 'We'll make fusion work. But you're never going to go back to the moon, and that's the only way you'll get massive amounts of helium-3. So forget it.' Meanwhile, the NASA folks tell us, 'We can get the helium-3. But you'll never get fusion to work.' So DOE doesn't think NASA can do its job, NASA doesn't think that DOE can do its job, and we're in between trying to get the two to work together." Right now, Kulcinski's funding comes from two wealthy individuals who are, he says, only interested in the research and without expectation of financial profit.
Overall, then, helium-3 is not the low-hanging fruit among potential fuels to create practical fusion power, and it's one that we will have to reach the moon to pluck. That said, if pure He3-based fusion power is realizable, it would have immense advantages.
Source: http://www.technologyreview.com