Research Watch
Prasen Vinchurkar
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Acoustic diode allows sound waves to only travel in one direction
By Ben Coxworth
15:31 July 27, 2011
A schematic of an acoustic diode, showing how the elastic spheres are able to convert the frequency of sound waves (Image: Georgios Theocharis/Caltech)
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When it comes to the sound-proofing of buildings, most people likely think of using materials that simply absorb the sound waves in a noisy room, so they can't proceed into a neighboring quiet room. Researchers at the California Institute of Technology (Caltech), however, are taking a different approach. They have created something known as an acoustic diode, that only allows sound traveling through it to go in one direction. If incorporated into building materials, such diodes would let sound travel from the quiet room to the noisy one, but would simply block noise transmission in the opposite direction.
The acoustic diode works much like a traditional electrical diode, which lets electrical currents pass in one direction, but keeps them from traveling back. In this case, sound waves are taking the place of electrical currents.
"We exploited a physical mechanism that causes a sharp transition between transmitting and nontransmitting states of the diode," said Chiara Daraio, professor of aeronautics and applied physics. "Using experiments, simulations, and analytical predictions, we demonstrated the one-way transmission of sound in an audible frequency range for the first time."
The diode contains an assembly of elastic spheres, made from granular crystals that transmit sound vibrations. The properties of these crystals can be tuned, allowing them to process a wide range of frequencies. They can also "downshift" the frequency of sounds, allowing them to pass through in the one direction, but at a lower frequency. It has even been proposed that this feature could be useful for energy harvesting, wherein sound waves would be converted to a frequency at which they could be converted into electricity.
Although other scientists have created similar systems in the past, those reportedly all lacked the distinct transition between transmitting and nontransmitting states - something that the Caltech team claim is necessary for optimum control of sound waves.
The research was recently published in the journal Nature Materials.
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So mommy and daddy can wrestle and can still hear the kids sleeping in the next room.. awesome....
Michael Mantion
- July 27, 2011 @ 05:38 pm PDT
no more noisy neighbors and dogs barking! Yessss!
dsiple
- July 28, 2011 @ 09:15 am PDT
Just wonder how efficient it is. If it takes a foot of this stuff, you'll have a hard time getting it installed in anything but sound studios.
Eletruk
- July 28, 2011 @ 06:44 pm PDT
@ Eletruk: I hardly think it would take any more than a few centimeters at most of this stuff, and besides, the picture is heavly magnified. It might only be a milimeter or two! This technology is incredible, and I'm proud of this company!
ilovegizmag
- August 14, 2011 @ 06:27 pm PDT
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Prasen Vinchurkar
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Prasen Vinchurkar
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New battery technology may allow for complete recharging within minutes
By Ben Coxworth
15:08 March 21, 2011
A diagram of a lithium-ion battery constructed using Braun's
nanostructured bicontinuous cathode (left), and a scanning electron
microscope image of the nanostructure (right)
(Image: Paul Braun, University of Illinois)
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Of all the criticisms of electric vehicles, probably the most commonly-heard is that their batteries take too long to recharge – after all, limited range wouldn't be such a big deal if the cars could be juiced up while out and about, in just a few minutes. Well, while no one is promising anything, new batteries developed at the University of Illinois, Urbana-Champaign do indeed look like they might be a step very much in the right direction. They are said to offer all the advantages of capacitors and batteries, in one unit.
"This system that we have gives you capacitor-like power with battery-like energy," said U Illinois' Paul Braun, a professor of materials science and engineering. "Most capacitors store very little energy. They can release it very fast, but they can't hold much. Most batteries store a reasonably large amount of energy, but they can't provide or receive energy rapidly. This does both."
The speed at which conventional batteries are able to charge or discharge can be dramatically increased by changing the form of their active material into a thin film, but such films have typically lacked the volume to be able to store a significant amount of energy. In the case of Braun's batteries, however, that thin film has been formed into a three-dimensional structure, thus increasing its storage capacity.
Batteries equipped with the 3D film have been demonstrated to work normally in electrical devices, while being able to charge and discharge 10 to 100 times faster than their conventional counterparts.
To make the three-dimensional thin film, the researchers coated a surface with nanoscale spheres, which self-assembled into a lattice-like arrangement. The spaces between and around the spheres were then coated with metal, after which the spheres were melted or dissolved away, leaving the metal as a framework of empty pores. Electropolishing was then used to enlarge the pores and open up the framework, after which it was coated with a layer of the active material – both lithium-ion and nickel metal hydride batteries were created.
The system utilizes processes already used on a large scale, so it would reportedly be easy to scale up. It could also be used with any type of battery, not just Li-ion and NiMH.
The implications for electric vehicles are particularly exciting. "If you had the ability to charge rapidly, instead of taking hours to charge the vehicle you could potentially have vehicles that would charge in similar times as needed to refuel a car with gasoline," Braun said. "If you had five-minute charge capability, you would think of this the same way you do an internal combustion engine. You would just pull up to a charging station and fill up."
Braun and his team believe that the technology could be used not only for making electric cars more viable, but also for allowing phones or laptops to be able to recharge in seconds or minutes. It could also result in high-power lasers or defibrillators that don't need to warm up before or between pulses.
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Physical limitations inhibit the "just pull up to a charging station and fill 'er up!" idea, what with the incredible amount of voltage/amperage required to transfer that much energy that quickly... not to mention the safety concerns in handling those "quantities" for the average consumer. There's a reason that high-power technicians are specially trained and equipped for dealing with this. Yes, recharging times need to be shorter, but they'll never be comparable to liquified fossil fuels in that regard (and that's okay!)
I think wireless (magnetic field) charging has potential - municipalities placing generating "pads" at traffic signals and public parking spots where the consumer is identified (by the vehicle's tag or RFID) and the power that's delivered is metered and billed accordingly.
Also, this tech (increased energy capacity) will greatly enhance the regen-braking aspect of electric vehicles, as their battery pack's currently limited ability in this area is a primary hindrance.
MzunguMkubwa
- March 22, 2011 @ 05:29 am PDT
This is a winner. One step further would be to have a pre-charged facility capable of dilvering this energy quickly rather than from the grid. That way, a fully-contained fast-charging facility could be made ready during hours of low demand and, like a tanked facility, draw down on its reserves during the day.
Muraculous
- March 22, 2011 @ 08:44 am PDT
MzunguMkubwa,
WHAT "PHYSICAL LIMITATIONS"?
The CHAdeMO fast charge method allows 125 Amps at 500 VDC ... that's 62.5 kW ... the Chevy Volt would charge (from empty ie. 10 kWhr) in about 9 minutes (if GM supported CHAdeMO).
ABB has developed DC fast charging stations that can deliver 125A, 250A or 500A DC current for charging, compatible with CHAdeMO protocols, or up to 250 kW. The Nissan Leaf would charge (from empty ie. 34 kWhr) in about 8 minutes.
With proper engineering, (safe) connectors and cables could handle 1,000 Amps at 1,000 VDC ... that's 1,000 kW or 1 MegaWatt. The Tesla Roadster would charge (from empty ie. 52 kWhr) in about 3 minutes.
The "Grid" needs to be "buffered" with banks of batteries that charge overnight. EVoasis.com EVSTAT Charging Stations have underground battery banks that handle multiple vehicles for fast charging.
EGM
- March 22, 2011 @ 09:51 am PDT
10 minute fast charge batteries exist and are use in Proterra Bus. check out
at around 0:40 sec for the statement
http://www.proterra.com/index.php
Chico Unr
- March 22, 2011 @ 11:51 am PDT
great step to a clean enviorment
Amit Hizak
- March 22, 2011 @ 03:59 pm PDT
""If you had five-minute charge capability, "
Can you imagine the power capacity of the charging station that can dump the amount of electricity into a battery? The average 120 volt plug can supply a maximum of 1,500 watts (or 1.5kw/hr) it takes about 12 hours for a full charge, so that's 12 X 1.5KW or 18 thousand watts...compress this into 5 minutes that's 216 thousand watts of power that will need to flow from the charging station into your batteries! I don't know about you, but I would not want to stand anywhere other than an armored bunker while that thing charges! It's like in the movie Demolition Man where where Wesley Snipes sticks the shock rod into the charging port of a police car....BOOM!
Ed
- March 22, 2011 @ 04:00 pm PDT
"I think wireless (magnetic field) charging has potential - municipalities placing generating "pads" at traffic signals and public parking spots where the consumer is identified (by the vehicle's tag or RFID) and the power that's delivered is metered and billed accordingly."
Take that one step further do it on main arterial roads charge while driving
harry_72
- March 22, 2011 @ 04:34 pm PDT
They do exist, but the point about safety is still valid. Of course, safety is a problem with traditional fuels also, so maybe we need to temper this idea a bit.
The problem I see with these batteries is that their overall lifespan is probably not improved over traditional batteries, because they will have the same problems of surface build-up and holes that cause normal batteries to dramatically reduce in effectiveness in a few years.
Super/ultra capacitors would be a great solution for this if they didn't tend to be tolerant of only low voltages. I still think that we will have to move more toward capacitive solutions than battery solutions to see real long term improvement in EV power.
Charles Bosse
- March 22, 2011 @ 06:27 pm PDT
@EGM and @Muraculous
To really support widespread distribution and use of such stations to the majority of the US populous, the energy grid would have to not only be massively retrofitted, but also supplied by the only reasonable energy source for such an endeavor: nuclear energy.
Unfortunately, that path is most likely dead due to political cowardice. Though, I don't think I'd put any in California...
Racqia Dvorak
- March 22, 2011 @ 07:51 pm PDT
When harry_72 talks about charging while driving on arterial roads, I can't help but think of Scaletrix ... You know - Slot Cars..? Is the future in Kids toys? Wow - the scale speed of those things is fantastic!
Chris Clarke
- March 23, 2011 @ 03:28 am PDT
Batteries have internal resistance, so the electrical energy in them is always 'evaporating'. That's why it's no good to buy old batteries, much of their energy has been consumed after a couple years on the shelf. Therefore one question I would like answered is, how inefficient is an electrical vehicle when it's just sitting there?
Gas gets old too, but if I park my car for a few weeks while I go on holidays, the gas hasn't lost any of its energy.
Grunchy
- March 23, 2011 @ 08:58 pm PDT
So, come back in 6-10 years when it'll be on the market?
The not so great thing about all these battery improvements is that they are a great many years from being on sale.
Still waiting for OLEDs after 5 years... ;)
Oh hum...
Stuart Halliday
- March 28, 2011 @ 07:49 am PDT
The internal resistance means that some of the energy being stored in the battery is lost as heat and has little to nothing to do with why old batteries are useless. Over time the physical arrangement degrades resulting in failed cells and decreased performance.
Also you would not need to retrofit the grid to support charging stations until after a large % of the population have switched to electric vehicles. Cellular communications sites already have a large surplus in routed energy, enough to handle a rapid charging station. Sites are also prolific enough to handle early demand.
Kr0nu5
- April 2, 2011 @ 01:26 pm PDT
Actually, all we need is lead-acid batteries, not advanced Nickel or Lithium; the 1999 EV1 with PSB lead-acid batteries went up to 110 miles on a charge, and the batteries lasted more than 50K miles.
This was a great car to commute in! Fast, fun and almost free to drive.
If you charge it with off-peak energy paid for by your rooftop solar system's daytime peak production, the EV helps the grid both ways:
SLOW charging at night uses electric otherwise unwanted,
Solar energy helps meet daytime peak, generating credits for night-time charging.
Doug Korthof
- April 5, 2011 @ 03:47 pm PDT
If I understand correctly, the thinner the battery plates are the faster they charge and discharge. However this also reduces the number of cycles or the longevity of the battery, meaning the battery will have to be replaced sooner. Plate thickness also influences the ability to keep supplying power over time. Hopefully the new engineering improves these factors somehow as well.
aquasparky007
- April 14, 2011 @ 04:23 am PDT
@ MzunguMkubwa
High amperage shielded cable/connector vs exposed stream of highly volatile liquid... Ya know, I think that the human instinct to live will prevent people from hacking through the cable to get at the power. Just a hunch though.
As for physical limitations, there are none. The infrastructure for recharging electric vehicles is already ready in place. As always, the only drawback to electric cars is stupid people.
Johnathan Switzer
- April 14, 2011 @ 11:54 pm PDT
This sounds almost exactly what I was thinking of when I wrote "Kathleen", a very short short-story about a guy and his car:
http://www.soopergrape.com/kathleen.html
If you have a small engine that puts out a steady supply of high efficiency power that is above your needs for cruising, and your requirements above this amount can be satisfied with a small, lightweight battery system that can instantly pump out and also reabsorb excess power from deceleration as fast as it is produced, as well as efficiently charge using whatever excess power the small powerplant puts out-you effectively have a full electric with a range easily greater than even high mileage diesels. Trickle charging for any unexpected shortage can be accomplished in any number of ways, since the total amount is so small.
Daniel Gooch
- May 16, 2011 @ 06:17 am PDT
MzunguMkubwa - I think you're 100% right - wireless transfer of energy could be a real advance for electric cars - no need for a pantagraph (as in the bar that gets electricicty from the overhead wire to the train) As long as there arent health implications.
Simon Gray
- May 22, 2011 @ 06:57 pm PDT
The comments on the HUGE amount of power for a quick charge are absolutely CORRECT.
For a serious electric car, consider at least 30 kWh. To charge that in 5 min it would demand an electric circuit (wires, connectors, etc) capable of handling 360 kWh.
But there's another hidden danger here:
- Batteries are NOT 100% efficient - part of the energy you feed into them is lost, turned into HEAT.
IF YOU EVER get such a fast-charging 360 kWh circuit, this means all the heat generated INSIDE THE BATTERY WHILE CHARGING would lead to a potentially high TEMPERATURE RISE in the battery.
Assuming 20% losses, 1/5 of the energy would turn into heat inside the battery. Another major issue to handle.
What's the problem of charging at home during the night? Your 8hs of sleep time would be enough even for common household electric installations.
Also, what's the problem of having a 30 - even 60 min charge time at a gas station, while you stretch your body for the additional 300 miles of your trip, drink a cup of coffe, have a snack...
Fast recharge may need very special equipment. Superconductors, anyone?
Keep your feet on the ground - let's use whatever proven technology we have NOW.
Rubin
- May 31, 2011 @ 10:52 am PDT
What about TOKAMAK generated energy (instead of nuclear generated) to power the "wireless grid"?
Marten Alvarado
- July 20, 2011 @ 06:04 pm PDT
solar energy.. bodies constructed out of solar energy panels.. capacitive and this specific battery solutions will eliminate the use of huge unsafe grids and magnetic fields that can disrupt some electronic devices.. http://www.gizmag.com/self-repairing-photovoltaic-technology/16291/ .. harness the power of the sun .. lets not waste it
Marné Nagel
- August 1, 2011 @ 03:38 pm PDT