For First Time, Researchers Demonstrate Heat and Sound Are Magnetic

 Photo: Ohio State University

Earlier this month, we reported on research demonstrating that heat propagates as a wave through graphene rather than as vibrations of atoms the way it does in 3-D materials. In 3-D materials, the collective state of those vibrating atoms is known as phonons.

For the first time, researchers at Ohio State University (OSU) have demonstrated that acoustic phonons, which can carry both heat and sound, have magnetic properties that allow them to be manipulated with magnetism.

In research published in the journal Nature Materials, the OSU researchers applied a magnetic field equivalent to that inside a magnetic resonance imaging (MRI) device (in this case, the magnet was reported to be fairly powerful at seven Tesla). They discovered that they could reduce the amount of heat flowing through a semiconductor by 12 percent.

“This adds a new dimension to our understanding of acoustic waves,” said Joseph Heremans, professor of mechanical engineering at Ohio State, in a press release. “We’ve shown that we can steer heat magnetically. With a strong enough magnetic field, we should be able to steer sound waves, too.”

Before anyone starts thinking about the discovery’s applicability to heat management in computers, they should keep in mind that the semiconductor had to be kept at temperatures very close to absolute zero (specifically, -268 degrees Celsius) in order for the researchers to measure the movements of the phonons.

In fact, it was the complexity of taking the measurements that had prevented researchers from recognizing the magnetic properties of phonons previously. In order to take thermal measurements at such a low temperature, Hyungyu Jin, a postdoctoral researcher and lead author of the study, used the semiconductor indium antimonide and shaped it into a lopsided tuning fork in which one arm was 4 millimeters wide and the other was 1 mm wide. Then he placed a heater at the base of each arm.

At normal temperatures, the ability of the material to transfer heat would be solely dependent on the kind of atoms in the material. But near absolute zero, the ability of the material to transfer heat can be determined by the physical size of the material. In this case, the difference in the sizes of the fork arms was significant. Phonons more easily filled the wider arm.

“Imagine that the tuning fork is a track, and the phonons flowing up from the base are runners on the track,” explained Heremans in the press release. “The runners who take the narrow side of the fork barely have enough room to squeeze through, and they keep bumping into the walls of the track, which slows them down. The runners who take the wider track can run faster, because they have lots of room.”

Eventually they all end up at their respective finish lines. But the track’s geometry determines just how quickly.

With this understanding, Jin was able to compare the temperature changes in the two fork arms. He first took the measurements without a magnet and then with one. With the magnet on, the heat flow through the larger arm slowed down by 12 percent.

Now that the researchers have measured magnetism’s effect on heat, they want to move on to see if they can use it to deflect sound waves.

Learn More Ohio State Universitygrapheneheatmagnetismphononssemiconductorssound waves

ORIGINAL: Spectrum
By Dexter Johnson
24 Mar 2015

(Energy) Harvest Festival

ORIGINAL: Traffic Technology International
August/September 2013

Illustration courtesy of Patrick George

The energy produced by vehicles driving on our roadways is a potentially huge source of untapped electricity. Louise Smyth meets the people who will have cause to celebrate if the concept sparks into life

Although the ideas of piezoelectric generation and embedding functionality into roads are not new, the notion of merging the two is novel. We've long embedded technologies in roadways, a case in point being the much-maligned loop detector Meanwhile, we've used piezoelectric materials for numerous applications over the years. So when considering a marriage between the two, a simple question to ask is, can any of the power created by vehicles driving over our roads be harnessed? Answering how this could be achieved is rather more complicated.

Simple thingsA piezoelectric energy harvesting system for roads is relatively straightforward. Vehicles drive over the surface, their tires place pressure on piezoelectric crystals embedded in the road, wíuch subsequently produce a small amount of energy. Multiply that scenario over a stretch of road with many vehicles traveling over the top and thousands of embedded crystals and you can almost envision a day when the lights of the Golden Gate Bridge could be powered by the vehicles driving over it We're not there yet We're at the academic and research stages, although some commercial outfits are taking the tentative steps to forming a compelling business case, as well as selling energy-harvesting equipment designed for roads. The potential would seem to be enormous, but fulfilling it is not without major challenges - something that anyone who's worked in the área can testify. John Gambatese, professor in the School of Civil and Construction Engineering at Oregon State University, is festival one of those researchers. Hot on the heels of Oregon’s successful solar highway deployment, he submitted his Research Problem Statement on energy harvesting for roadways to Oregon DOT at the end of 2012. 

“We leave a lot of energy on the road in different ways,” he says. “Whether it’s the vibration on a bridge or roadway, or the wind produced by the traffic, there’s energy there that can be harvested. It might only be a small amount at each location but when you add it up, it could help to power our traffic infrastructure, our streetlighting, or other electrical requirements we may have.”

So if that goes according to plan, what about selling the surplus back into the grid? 

“For now we’re just trying to develop the technology so we can start collecting energy,” Gambatese says. “Once we do that, we can monitor how much we obtain and then there’s a chance we can optimize the technologies with the goal being to feed electricity back into the grid. Whether or not we’ll have that capability in the next five to 10 years, though, I’m not so sure.”

From research to reality?
The FHWA is funding work on energy harvesting for roads, indicating that it sees some future potential in the concept. The Administration’s Eric Weaver reveals how the testing is being conducted and what the initial results have shown

The Virginia in Tech Transportation Institute (VTTI) presence is a notable in the testing of piezoelectric energy harvesting for roads and is currently involved in a US$1M FHWA-funded project.  The stated aim isn’t to assess commercially available systems but to put a VTTI-developed system through its paces. The research is being overseen by Eric Weaver, a research civil engineer in the FHWA’s Office of Infrastructure, R&D, and an expert in this sector. “We are currently exploring the potential," says a cautiously optimistic Weaver about the technology. “Our initial research indicates that the amount of energy harvested might be modest but could theoretically offset some utility costs or provide power in areas that  are currently inaccessible to the grid.”

Like many people in the field, Weaver foresees any power generated being used only where it is harvested, for th short term at least. "It's meant to provide energy within the energy right-of-way to be used for transportation infrastructure demands,” he continues. “However, depending on the application and the infrastructure demand, excess energy could potentially be transferred back to the grid, provided that the electric grid infrastructure is updated to enable this.

 “Our work has involved a significant amount of analytical modeling, as well as laboratory trial and error with different  geometric configurations of piezoelectric generators and the materials that encase them. Virginia Tech researchers have installed some sensors at two locations in the state, one of which is at a truck weigh station and the other at a full-scale test road called the VA Smart Road."

Interestingly, for comparison purposes, researchers also installed sensors from the Israeli company Innowattech in at least one of those locations.

Although Weaver reveals that the results so far are perhaps not as encouraging as vendors or proponents of the technology might hope, the work is helping to identify teething problems that likey be overcome. “So far in our research, low power output is observed with each axle load application. Part of the reason for this is that the wheel load doesn’t always pass directly over the generator, because they’re centered in the wheel path, where the wheels don’t onsistently track. To mitigate this problem, researchers are exploring other generator geometries that provide more spatial coverage.”

“The sensors have been rugged enough so far to hold up to the traffic loading they have received,” Weaver continues. “A further benefit is that the data from this project has been used to support another study performed for the California Energy Commission to evaluate the feasibility of all piezoelectric generation technologies currently on the market.”

Complete Text: Traffic Technology International August/September 2013 

"Depending on the application and the infrastructure demand, excess energy could potentially be transferred back to the grid"

www.TrafficTechnologyToday.com

The Science of Stowaways

ORIGINAL: The Scientist

By Hayley Dunning
October 1, 2012

A dock dislodged by 2011's Japanese tsunami washes ashore in Oregon, posing an invasive species threat, but also serving as an unprecedented natural experiment in open-ocean dispersal.

EXOTIC MUSSELS: Mytilus edulis and M. galloprovincialismussels cling to the derelict dock among unidentified barnacles. Oregon Parks and Recreation department

This June a dock weighing more than 180 tons washed up on the Oregon coast, about a year after being dislodged from Japan’s seashore during the devastating earthquake and tsunami that struck there in March 2011. The dock is one of the largest pieces of debris to wash up on the opposite side of the Pacific, and it arrived earlier than anyone expected. But a bigger surprise for researchers and natural-resource managers dealing with the debris was the profusion of marine organisms clinging to the dock, many of which have already been pegged as potentially aggressive invasive species. “We have already identified very bad things on this debris,” says John Chapman, an expert on marine invasive species at Oregon State University. “We can already see things that we definitely do not want.”

One species clinging to the dock that is causing concern to Chapman and his colleagues is wakame (Undaria pinnatifida), a brown alga that can suffocate entire ecosystems when its natural predators are not around to keep it in check. Chapman likens the alga’s rapacious effect to “cutting down the whole forest,” and warns that the consequences of an invasion by such a prolific species might not be known for years to come. And there were many more invasive organisms present, including a thriving population of Mytilus galloprovincialis, a blue mussel that was itself introduced to Asia from the Mediterranean.

Pre-tsunami, the mussels only covered the part of the dock that was below the water’s surface. But when the structure was ripped from its pilings, it sank a little and dipped a fresh surface into the ocean. This previously high-and-dry surface was also covered in mussels by the time the dock reached Oregon, making M. galloprovincialis the dominant species on the structure.

There were very few small mussels on the dock. Did the entire population grow rapidly in Japanese waters as the dock bobbed just offshore before setting off on its open ocean journey? Or did the mussels continue to grow, encountering nutrients along the way? To try to answer these questions, marine ecologist Jessica Miller, also at Oregon State University, is working to unravel growth patterns from the creatures’ shells.

DOCK WORKERS: Oregon Department of Fish and Wildlife staff and volunteers remove marine organisms from the wayward dock, which landed at Agate Beach.

CREDIT: OREGON PARKS AND RECREATION DEPARTMENT

Much as trees’ yearly rings record environmental changes, hard-shelled marine organisms lay down annual layers of shell—slower growth and unfavorable seasons corresponding to thinner lines. The age and nutritional history of any mussel can therefore be determined, but chemical analyses of changes in elements across growth lines can also tell Miller something about the proximity to shore and the temperature at which the organism grew, allowing her to reconstruct the colonization history of the dock. “This chance natural experiment gives a better opportunity to understand transoceanic dispersal,” she says.

Many of the dock organisms were collected and await analysis in freezers and labs across North America; much of the remaining biomass has been obliterated in an effort to restrict the spread of invasive species. Scientists recovered around 23–27 kg of organisms for research, but local responders scraped off and disposed of another 2 tons of material. Miller says that 92 species have already been identified from what was saved, and the team is confident they destroyed a large percentage of the total species present.

But when Chapman and his team looked for organisms that might have made landfall as the dock crashed into the Oregon coast, they found a large debris field of non-native mussels stretching down the beach. Chapman says they’ll try to determine what proportion of organisms was pulverized as the dock came to shore and what was washed up on the beach. “The remainder is what we’re afraid of—what’s offshore and didn’t get crushed, and could still be alive,” he says.

Invasive species expert Rick Boatner of the Oregon Department of Fish and Wildlife says it could be a while before we really know which, if any, species have managed to take hold on the Oregon coastline. He says that the clean-up operation on the dock was largely successful and the department is ready for another invasion, noting that at least one other Japanese dock is known to be adrift, along with ships and other large debris. However, he says, removing the first dock cost almost $100,000, and further funding is an issue, even in the face of the severe economic havoc invasive species can wreak. “If [an invasive species] got into the oyster aquaculture, it could devastate that,” Boatner says.

Among the fears, though, Chapman sees the silver lining: an experiment that could never have been simulated. Many invasive species travel in ship ballast water, but these are typically discovered only after they have become established, with researchers left trying to reconstruct when and how they arrived.

“This is the first time in history that a dispersal event could be really watched,” Chapman says. Boatner agrees: “As a biologist, it’s kind of a cool thing. As an invasive species person, I don’t care for it.”