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Showing posts with label Energy. Show all posts
Showing posts with label Energy. Show all posts

Monday, 4 November 2019

Listen to the energy of lightning

Everyone knows that counting the seconds between the appearance of a lightning and the arrival of thunder gives the distance at which the lightning falls. Researchers at the Jean Le Rond Institute in Alembert and CEA have shown that this sound can also be used to estimate the energy of a lightning bolt. In this work published in Geophysical Research Letters , scientists deduce the geometry of lightning through a network of microphones, then calculate the energy.

© Institut Jean le Rond d'Alembert The acoustic energy of thunder as a function of the observation distance in km at the point of impact on the ground of the lightning. Squares represent simulated flashes and triangles measure HyMeX. Both follow a similar behavior.


Lightning rebalances the electrostatic charge between two clouds, or between a cloud and the ground. This electrostatic discharge locally increases the temperature of several tens of thousands of degrees, causing a shock wave that spreads in the atmosphere : thunder. If we know how to use this sound to estimate the distance at which a lightning struck, researchers at the Jean-Rond d'Alembert Institute (CNRS / Sorbonne University) and the CEA managed to use it to measure the distance power of lightning. A parameter that suffers from an uncertainty of up to three orders of magnitude.

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The team used the data measured in 2012 as part of the European project HyMeX, which studies the Mediterranean climate . Four microphones recorded for two months , and continuously, the sound emanating from the sky of the Cevennes, a region particularly struck by the storms. These recordings were first used to reconstruct the geometry of lightning, proving the correlation between the location of acoustic and electromagnetic sources. Then, the researchers used them again to isolate, within the thunder, the signalacoustics from some of its branches, including the main channel that connects the storm cloud and the ground. Now we can calculate the thunder of a flash from its geometry and its energy. The researchers compared field-collected thunders to a simulated thunderstorm database of 72 virtual flashes, statistically consistent with true lightning. This has shown that acoustic measurements give very good results in estimating the energy of negative-lightning flashes, which represent 90% of the cloud-to-cloud discharges, and at a distance of between three and twelve kilometers from the pickups.


Source

Wednesday, 30 October 2019

A new device captures CO2 from the air, stores it and returns it on demand


With the growth of human industrial activities, the rate of atmospheric carbon dioxide has increased considerably. In recent years, various methods for capturing CO2 in the air and transforming it into useful products have been developed with more or less efficiency. Recently, a team of MIT researchers developed a device to capture CO2 in the air at any concentration, store it, and redistribute it for practical uses such as CO2 injection for agriculture. or the gasification of beverages.

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A new way to remove carbon dioxide from the air could be an important tool in the fight against climate change. The system can operate at virtually any level of concentration, even at the roughly 400 parts per million currently in the atmosphere.

Most methods of removing carbon dioxide from a gas stream require higher concentrations, such as those present in flue gas emissions from fossil fuel plants. Some variants have been developed that can work with the low concentrations found in the air, but the new method consumes much less energy and costs less.

A "battery" to capture and release CO2 on demand

The technique, based on the passage of air through a stack of charged electrochemical plates, is described in the journal Energy and Environmental Science . The device is essentially a large specialized battery that absorbs carbon dioxide from the air (or other gas stream) passing on its electrodes during its charging, then releases the gas during its discharge.

In operation, the device would simply alternate between loading and unloading, with fresh air or feed gas being blown into the system during the loading cycle, and then the pure and concentrated carbon dioxide being expelled during unloading.

As the battery charges, an electrochemical reaction takes place on the surface of each electrode stack. These are covered with a compound called polyanthraquinone, composed of carbon nanotubes.

In this scheme of the new system, the air entering the top right passes into one of the two chambers (gray rectangular structures) containing battery electrodes that attract carbon dioxide. Then, the air flow passes into the other chamber, while the carbon dioxide accumulated in the first chamber is sent to a separate storage tank (right). These alternative flows allow a continuous operation of the process in two stages. Credits: Sahag Voskian / T. Alan Hatton


Electrodes have a natural affinity for carbon dioxide and readily react with its molecules in the airflow or feed gas, even when present at very low concentrations. The reverse reaction occurs when the battery is discharged - at this point, the device can provide some of the power needed for the entire system - and thus ejects a pure carbon dioxide stream. The entire system operates at ambient temperature and at normal atmospheric pressure.

Electrodes optimized to capture CO2 at any concentration

" The biggest advantage of this technology over most other carbon capture or absorption technologies is the binary nature of the adsorbent's affinity for carbon dioxide, " explains Voskian. In other words, the electrode material, by its nature, " has a high affinity or no affinity ", depending on the state of charge or discharge of the battery. Other reactions used for carbon capture require intermediate stages of chemical treatment or the provision of substantial energy such as heat or pressure differences.

Diagram of a unique electro-swing adsorption electrochemical cell, with porous electrodes and electrolyte separators. The outer electrodes, coated with a poly-1,4-anthraquinone composite, can capture CO2 when applying a reducing potential via the carboxylation of the quinone and release the CO2 during the polarity reversal. . Credits: Sahag Voskian / T. Alan Hatton

This binary affinity captures carbon dioxide in any concentration, including 400 parts per million, and releases it into any carrier stream, including 100% CO2, " says Voskian. That is, with any gas passing through the stack of these flat electrochemical cells, the captured carbon dioxide will also be ejected during the discharge. For example, if the desired end product is pure carbon dioxide for use in the carbonation of beverages, a stream of pure gas may be blown through the plates. The captured gas is then released from the plates and joins the stream.

A replacement for fossil fuels currently used to generate CO2

In some non-alcoholic beverage bottling plants, fossil fuels are burned to generate the carbon dioxide needed to make beverages. Similarly, some farmers burn natural gas to produce carbon dioxide to grow their crops in greenhouses. The new system could eliminate this need for fossil fuels in these applications and, at the same time, eliminate greenhouse gases from the air.

Alternatively, the flow of pure carbon dioxide could be compressed and injected underground for long-term disposal, or even converted into fuel through a series of chemical and electrochemical processes. " All of this is done under ambient conditions - no thermal, chemical or pressurized input is needed. It's just these very thin sheets, with both active surfaces, that can be stacked in a box and connected to a power source . "

The new device can be used in many fields requiring the generation and injection of carbon dioxide, replacing fossil fuels. Credits: Sahag Voskian / T. Alan Hatton


We have been striving to develop new technologies to solve a range of environmental problems, avoiding the use of thermal energy sources, changing the system pressure, or adding chemicals to complete the separation cycles. of liberation. This carbon dioxide capture technology is a clear demonstration of the power of electrochemical approaches that require only small voltage variations to drive separations, "says Hatton.

In a working installation, for example in a power plant producing continuous exhaust gas, two sets of cells of this type of electrochemical cells could be mounted side by side to operate in parallel, the combustion gases being directed from first to a first set for carbon capture, then diverted to the second set while the first set enters its discharge cycle.

An efficient, inexpensive method with low energy consumption

By alternating, the system can still capture and evacuate the gas. In the laboratory, the team proved that the system could withstand at least 7000 charge-discharge cycles, with a loss of efficiency of 30% during this period. Researchers estimate that they can easily improve this figure between 20,000 and 50,000 cycles.

The electrodes themselves can be made with standard chemical treatment methods. Although this is done today in a laboratory, they can be adapted so that they can finally be manufactured in large quantities through a roll-to-roll process, similar to a newspaper printing press. " We've developed very cost-effective techniques, " Voskian says, arguing that they could be produced for tens of dollars per square meter of electrode.

Compared to other existing carbon capture technologies, this system consumes little, as it only requires about one gigajoule of energy per tonne of carbon dioxide captured. Other existing methods have energy consumption ranging from 1 to 10 gigajoules per tonne, depending on the input carbon dioxide concentration.

Source

Monday, 29 July 2019

A new device channeling heat into light could bring solar cell efficiency up to 80%!

Gao et al. ACS Photonics, 2019 

Solar cells, or photovoltaic cells, which "turn" sunlight into electricity, are a brilliant element of modern technology. However, one particular aspect has proved to be an important problem: they are not very effective. Indeed, the majority of sunlight absorbed is lost, in the form of heat. As a result, the average efficiency of a commercial solar panel is between 11 and 22% only. But now, a new device could increase this figure up to 80%, which would be absolutely revolutionary.


This new design is based on a set of single-walled carbon nanotubes, which recaptures "thermal" photons from the infrared radiation (heat) lost from solar panels. Then, the device emits this energy in the form of light in a different wavelength, which can in turn be recycled into electricity.

Thermal photons are just photons emitted by a hot body ," said Junichiro Kono of Rice University. " If you look at something hot with an infrared camera, you will see it shine. The camera captures exactly those thermally excited photons , "Kono added.

It should be known that infrared radiation is the part of the sunlight that carries heat. Of course, this is invisible to the human eye, but is on the same electromagnetic spectrum as visible light, radio waves, and X-rays.

This type of infrared radiation is emitted by your stove, by a campfire or even by your cat purring on your lap. In other words, basically, anything that emits heat emits radiation. " The problem is that the thermal radiation is broadband, while the conversion of light into electricity is only effective if the emission is narrowband. The challenge was to bring broadband photons into a narrow band , "said engineer Gururaj Naik.

One of the properties of nanotubes is that the electrons in them can only move in one direction. This produces an effect known as hyperbolic dispersion, in which the films are metal conductors (in one direction), but insulate perpendicular to that direction.

This means that thermal photons can enter from (almost) anywhere, but they can only escape in one direction. This process converts heat into light and from there it can be converted into electricity.

In the device created by the researchers, the carbon nanotube film can withstand temperatures up to 700 degrees Celsius, although the base material is able to withstand a much higher temperature, up to 1600 degrees Celsius.

  Then, the research team exposed their device to a heat source to confirm the narrowband output. Each of the resonator cavities in the film reduced the thermal photon band, producing light. The next research step will therefore be to collect this light using photovoltaic solar cells and to confirm the predicted efficiency.

Xinwe Li, a graduate student from Rice University (left), and Weilu Gao, postdoctoral researcher. Gao contributed to the development of a device to recycle heat lost in photovoltaic cells. This could ultimately improve the efficiency of industrial waste heat recovery. Credits: Jeff Fitlow.

By compressing all the thermal energy wasted in a small spectral region, we can transform it into electricity very efficiently. The theoretical prediction is that we can achieve efficiency up to 80%! Naik said.


Bibliography:

Macroscopically Aligned Carbon Nanotubes as a Refractory Platform for Hyperbolic Thermal Emitters
Weilu GaoChloe F. DoironXinwei LiJunichiro KonoGururaj V. Naik*
ACS Photonics2019671602-1609
https://doi.org/10.1021/acsphotonics.9b00452


Saturday, 20 July 2019

Trapping CO2 in natural "molecular cages" to produce electricity

Methane in flames at the end of a methane hydrate

In view of the tremendous increase in atmospheric CO2 levels, scientists have embarked on a race to effectively reduce the concentration of this greenhouse gas. Several techniques have been proposed in recent years, but all have proved relatively expensive and without any real counterpart. Recently, researchers have proposed a method to trap CO2 in methane hydrates; the methane thus hunted could be burned to produce electricity in return.


A method explored over the last decade could be a step forward, according to a new computer simulation. The process would involve pumping atmospheric CO2 into methane hydrates - large pools of chilled water and methane under the sea floor, under water at a depth of 500 to 1000 meters - where the gas would be stored or sequestered Permanently.

Inbound CO2 would release methane, which would be channeled to the surface and burned to produce electricity. This would fuel the sequestration operation or generate income to pay for it. There are many deposits of methane hydrate along the coast of the Gulf of Mexico and other coasts. Large power plants and CO2-emitting industrial facilities also border the Gulf Coast.

Methane hydrates form naturally at the bottom of the seas and oceans. They constitute cages trapping methane molecules escaping from geological cracks. Credits: Janet Kimantas

An option would be to capture the gas directly from the nearby chimneys, preventing it from reaching the atmosphere. And factories and industries themselves could provide a direct market for the electricity produced.

Trapping atmospheric CO2 in methane hydrates

A methane hydrate is a deposit of frozen water molecules, similar to a crystal lattice. The unstable network includes many empty molecular-size pores, or "cages," that can trap methane molecules rising through cracks in the rock below. The computer simulation shows that the extraction of methane with CO2 is greatly improved if a high concentration of nitrogen is also injected and the gas exchange is a two-step process.

In one step, the nitrogen enters the cages; this destabilizes the imprisoned methane, which escapes from the latter. In a separate step, nitrogen helps CO2 to crystallize in empty cages. The disturbed system " seeks to reach a new equilibrium; the balance goes to more CO2 and less methane e "explains Kris Darnell, lead author of the study published in the journal Water Resources Research.

A methane hydrate forms a real molecular cage that can trap several types of gas. The method proposed by the researchers aims to drive the methane out of the cage and replace it with CO2; the methane is then burned out to produce electricity. Credits: AMU

A group of laboratories, universities and companies tested the technique in a limited 2012 feasibility test on the North Slope of Alaska, where methane hydrates are formed in sandstone under deep permafrost. They sent CO2 and nitrogen through a pipe in the hydrate. Part of the CO2 was eventually stored and methane was released in the same pipe. " It's good that Kris Darnell can make progress, " says Ray Boswell of the US Department of Energy's National Energy Technology Laboratory.

Brine: an alternative to methane hydrates

The new simulation also showed that CO2 exchange for methane would probably be much larger and faster if CO2 penetrated at one end of a hydrate pool and methane was collected at a far end. . The concept of the technique is quite similar to that of Steven Bryant and other researchers at the University of Texas, presented in the early 2010s.

In addition to numerous deposits of methane hydrates, the Gulf Coast includes large pools of warm salt brine in sedimentary rocks beneath the coast. In this system, the pumps would send CO2 down through one end of the deposit, forcing the brine into a pipe at the other end and rising to the surface. There, the hot brine would circulate in a heat exchanger, where the heat could be extracted and used for industrial processes or to generate electricity.

The upstream brine also contains methane that could be siphoned and burned. CO2 dissolves in the underground brine, becomes dense and flows further underground, where it remains theoretically trapped.

Interesting methods still too economically unviable 


Both systems face great practical challenges. A concentrated flow of CO2 is created; gas represents only 0.04% of air and about 10% of stack emissions from a power plant or industrial plant. If an efficient system using methane hydrate or brine requires a 90% CO2 input, for example, the gas concentration will require a huge amount of energy, which makes the process very expensive. " But if you only need a 50% concentration, it could be more interesting, " says Bryant. " You have to reduce the cost of capturing CO2 ".

Another major challenge for the methane hydrate approach is to collect released methane, which could simply escape the deposit through numerous cracks, and in all directions.

Given these realities, there is little economic incentive to use methane hydrates to sequester CO2. But with increasing atmospheric concentrations and global warming, systems capable of capturing gas while providing the energy or revenue needed to run it could become more viable than techniques that simply extract CO2. from the air and trap him without offering anything in return.



Saturday, 6 July 2019

Bacteria and graphene to produce clean energy



If the development of technologies to produce or store clean energy has long rested on law materials, since a few years scientists are investigating methods to combine micro-organisms and materials, in the aim to achieve clean energy. Recently, a team of researchers combined an electricity generating bacteria and oxide Graphene to a get a material biohybride whose energy applications are extremely broad.


Combine with carbon nanomaterials microorganisms could facilitate the transition to renewable energy. Researchers at the KAUST (King Abdullah University of Science and Technology) show that the bacteria and nanomaterials can be used together to form a biohybride material that works well as electrocatalyseur. The material could be used in the production of free carbon to solar fuels and in many other applications of green energy.

A process called response to evolution of oxygen (REL) is at the heart of many clean energy technology. In the case of solar fuel production, for example, OER can use solar electricity to split water into oxygen and hydrogen molecules, thereby producing clean hydrogen that can be used as fuel. Currently, rare and expensive metals are used as electrocatalysts REL.

Bacteria and graphene oxide: a green biohybride material

But biohybrides graphene-based materials could be an inexpensive and eco-friendly alternative, showed Pascal Saikaly and his team. Reduced graphene oxide and graphene are highly conductive, rugged mechanical and widely available. However, they become active catalysts only after having been doped with other elements, such as sulfur, iron, nitrogen, or copper.

The Geobacter sulfurreducens proteobacterie observed with the scanning electron microscope; It generates electricity by reducing the carbon compounds. She is so alone, a source of bio-energy. Credits: Reema Bansal et al. 2015


REL graphene-based catalysts are usually developed by chemical, methods that require conditions of stringent reaction obtained with abundant toxic chemicals and high temperature " explains Shafeer Kalathil, author of the study. A more environmentally friendly alternative is to use bacteria to occupy the surface of reduced graphene oxide. " We used the electric sulfurnucens Geobacter bacteria because it is not pathogenic, rich in the iron-containing proteins and present in abundance in nature ."

A highly effective Bionic electrocatalyseur

When the team mixed the bacteria and graphene oxide in oxygen-free conditions, bacterial cells adhered to the surface and produced iron-rich proteins that interacted with graphene oxide biochemically in the as part of their natural metabolism.

As a result, reduced graphene oxide will eventually be combined with iron, copper and sulfur; becoming a highly effective REL electrocatalyseur. The details have been published in the journal Chemistry of Materials.

The information supplied by the bacteria have transformed catalytically inert graphene in a highly used catalyst. ' OER materials biohybrides activity was greater than expensive catalysts for OER metal "said Kalathil. The bonus is the ecological method used by the team to make it happen.

Saikaly and his team are now working on the production and marketing large scale of this biohybride catalyst. They also develop other types of catalysts biohybrides for other important electro-catalytiques reactions, such as the hydrogen evolution reaction and the reduction of carbon dioxide.




Bibliography:

Bioinspired Synthesis of Reduced Graphene Oxide-Wrapped Geobacter sulfurreducens as a Hybrid Electrocatalyst for Efficient Oxygen Evolution Reaction
Chem. Mater.201931103686-3693
https://doi.org/10.1021/acs.chemmater.9b00394

Monday, 1 July 2019

Artificial electric eel generates energy even underwater

The bionic nanogenerator is extremely simple, but works in any environmental condition. [Image: TAN Puchuan]

Bionic nanogenerator:

Chinese researchers have developed a bionic nanogenerator inspired by electric eels.

Yang Zou and his colleagues say their new technology meets the rigid demands of portable and dressing equipment in terms of stretchability, deformability, biocompatibility and impermeability.

They point out as key applications the creation of a power source for electronic devices that need to operate in the air, earth or water, and in human monitoring, due to their excellent flexibility and mechanical responsiveness.

The nanogenerator mimics the structure of the ionic channels in the citomembrane of the electric eel electrocytes.

The mechanically sensitive bionic channel was created based on the incompatibility of voltage between the polymers PDMS ( polydimethylsiloxane ) and silicone.

The demonstration involved monitoring a swimmer's movements in real time. [Image: TAN Puchuan]

Artificial eel

Like the ion channel of the eels, the nanogenerator can generate an open circuit voltage of up to 10 V underwater and up to 170 V under dry conditions.

This capability was maintained after 50,000 uniaxial tensile tests with a 50% traction rate.

To prove the practicality of the technology, the researchers built an underwater wireless motion monitoring system. Through this system, signals from different swimming movements can be transmitted, displayed and recorded synchronously.



Bibliography:

 The bionic stretchable nanogenerator for underwater sensing and energy harvesting
Yang Zou, Puchuan Tan, Bojing Shi, Han Ouyang, Dongjie Jiang, Zhuo Liu, Hu Li, Min Yu, Chan Wang Xuecheng Qu, Luming Zhao Yubo Fan, Zhong Lin Wang, Zhou Li
 Nature Communications Vol .: 10,
Article number: 2695 
DOI: 10.1038 / s41467-019-10433-4

Friday, 28 June 2019

Researchers have discovered the new property of Light: the autotorque

Like a screw with a heterogeneous thread, the light with autotorque will have immediate technological applications. [Image: Rego et al. - 10.1126 / science.aaw9486]

Twisted light

Spanish researchers have discovered that light has a new property, which they named autotorque.

This discovery opens up exciting possibilities in light-related applications, from consumer appliances to scientific equipment and fiber-optic telecommunications.

In addition to the many known properties - such as intensity and wavelength - the light can be twisted , possessing what is known as angular momentum - the photons travel in a straight line, but spinning around the axis of the beam of light.

Light beams carrying highly structured angular momentum, known as angular orbital momentum (OAM), are known as vortex bundles.

The intensity of these beams, which have a ring-like shape, has applications in optical communications, microscopy, quantum optics and microparticle manipulation.

Vision of longitudinal section of light beam with autotorque. [Image: Rego et al. - 10.1126 / science.aaw9486]

Light with autotorque

Knowing this turn of twisted light, Laura Rego and colleagues at the University of Salamanca wondered if this spin of the photons could not function in a time-dependent way.

It can, and this is precisely what the autotorque consists of: Light beams with their own torque have an angular momentum that changes continuously in time. In other words, light not only twists, but has a different degree of twisting along the length of the beam.

The bundles resemble a croissant, containing more than one octave of orbital angular momentum values ​​along the light pulse.

"This is the first time someone has predicted or even observed this new property of light," said Laura. "For example, we think that we can modulate the orbital angular momentum of light in the same way that frequency is modulated in communications."

If this is indeed possible, telecommunications will be able to jump-start, allowing much more data to be placed on the same optical fibers.

In addition, this new light mode opens new perspectives for optical tweezers , tiny tracers used to trap nanoparticles in cells.




Bibliography:

Generation of extreme-ultraviolet beams with time-varying orbital angular momentum

 Laura Rego, Kevin M. Dorney, Nathan J. Brooks, Quynh L. Nguyen, Chen-Ting Liao, Julio San Roman, David E. Couch, Allison Liu, Emilio Pisanty, Maciej Lewenstein, Luis Plaja, Henry C. Kapteyn, Margaret M. Murnane, Carlos Hernández-García

 Science DOI: 10.1126 / science.aaw9486

Thursday, 27 June 2019

Wireless charging can reduce cell phone battery life

The three modes tested: (a) charging plugged into the network; (b) aligned inductive loading and (c) misaligned inductive loading. [Image: Loveridge et al. - 10.1021 / acsenergylett.9b00663]

Inductive charging

The way you recharge your phone - from the standard charger, plugged in, or the inductive, wireless charging - can change the life expectancy of your battery.

This is the conclusion of Melanie Loveridge and colleagues at the University of Warwick in the UK who compared three modes of charging the cell phone, two of which involved charging wirelessly.

Inductive charging allows a power source to transmit electricity through an air gap , without the use of wiring.

The inclusion of inductive charging coils in several newer models of mobile phones has led to the rapid increase in adoption of the technology. In 2017, automakers announced the inclusion of consoles within 15 models to inductively charge consumer electronics devices, including cellphones - and on a much larger scale, several companies are considering charging electric vehicle batteries in the same way.

The problem is that this charging mode generates a lot of unwanted heat, which harms the battery, decreasing its life.

There are several sources of heat generation associated with any inductive charging system - both in the charger and in the apparatus being charged. This additional heating is aggravated by the fact that the apparatus and the charging base are in physical contact, which means that any heat generated in one of them is transferred to the other by simple conduction and thermal convection.

On cell phones, the coil that receives power is attached to the back cover of the phone, next to the battery and everything else, which limits the possibility of dissipating the heat generated inside the phone or to protect it from the heat coming from the outside.

The life of a battery is closely related to the temperature at which it operates. The higher the temperature, the smaller the number of cycles in which it can be charged and used. 

Batteries and temperature

The batteries of lithium ions are chemical devices, and a rule of thumb - or, more technically, the equation Arrhenuis - establishes that for most chemical reactions, the reaction rate doubles for every 10 ° C increase in temperature.

In a battery, undesired reactions that may occur include the accelerated growth rate of passive films (a fine inert coating rendering the underlying surface non-reactive) on the electrodes of the cell. This occurs through redox reactions, which irreversibly increase the cell's internal resistance, resulting in degradation in performance and, ultimately, failure.


An additional problem encountered by researchers occurs when the coil of the device being charged is not perfectly aligned with the coil of the charger - the results are even worse, with greater heat generation.

Although manufacturers warn of catastrophic failures - explosions, for example - at operating temperatures above 50 or 60 ° C, a lithium-ion battery with a temperature above 30 ° C is typically considered at elevated temperature, exposing the battery to the risk of a shorter life expectancy, say researchers.

So, although the team has not established how much battery life your cell phone will lose in each case - which would require long-term observations and a large number of handsets to establish an average - the message is quite clear: Cell phone heats up with inductive charging, and battery and high temperatures do not.

Alignment between the machine and charger coils is essential for greater wireless charging efficiency. [Image: Loveridge et al. - 10.1021 / acsenergylett.9b00663]

Charging and reducing battery life

In the case of the telephone charged with the charger plugged into the conventional mains, the maximum average temperature reached within 3 hours of charging did not exceed 27 ° C, starting from an ambient temperature of 25 ° C.

In contrast, with the phone being charged by aligned inductive charging, the temperature peaked at 30.5 ° C, which was gradually reduced during the second half of the charging period.

In the case of misaligned inductive loading, the peak temperature was of similar magnitude (30.5 ° C), but this temperature was reached earlier and persisted for much longer at this level (125 minutes, versus 55 minutes for correctly aligned loading) .

The maximum average temperature of the charging base during charging under misalignment reached 35.3 ° C, two degrees above the temperature detected when the phone was aligned, which reached 33 ° C. This signals the deterioration in system efficiency with additional generation of heat attributable to energy losses and parasitic currents.

Also noteworthy was the fact that the maximum input power at the charging base was higher in the test where the phone was misaligned (11W) than with the phone well aligned (9.5 W).

The team's conclusion is that the inductive charging, while convenient, will likely lead to a reduction in the battery life of the mobile phone. For many users, this degradation may be an acceptable price for convenience, but for those who wish to take advantage of the longer phone life, cable charging is still recommended.



Bibliography: 

Temperature Considerations for Charging Li-Ion Batteries: Mains versus Inductive Charging Modes for Portable Electronic Devices
Mel J. Loveridge, Chaou C. Tan, M. Faduma Maddar Guillaume Remy, Mike Abbott, Shaun Dixon, Richard McMahon Ollie Curnick, Mark Ellis, Mike Lain, Anup Barai, Mark Amor-Segan, Rohit Bhagat, Dave Greenwood
 ACS Energy Letters
 Vol .: 4, 5, 1086-1091
 DOI: 10.1021 / acsenergylett.9b00663

Monday, 24 June 2019

Transparent battery stores and generates energy

Scheme of the layers and photo of the prototype, which is flexible in addition to transparent. [Image: 10.1021 / acsami.8b20143]

Transparent rechargeable battery


Researchers from South Korea have created a fully transparent and flexible battery prototype.

More than that, they added a number of other features, composing an almost totally transparent device prototype.

Using a graphene film as an electrode and a "semi-solid" electrolyte, the battery achieves a level of transparency of 77.4%.

In addition, the team designed the structure with self-loading and storage functions. This was done by inserting a power storage panel - a supercapacitor - inside the top layer of the device, and a power conversion panel - a nanogenerator - inside the bottom layer.

That is, it is possible to charge the battery by tightening it or taking advantage of natural movements such as the floor, which makes the device suitable for dressing applications.

Finally, a touch-sensitive layer was placed just below the top-tier power storage panel, allowing you to create a transparent whole device.

"We decided to start this research because we were impressed with the transparent smartphones that appear in the movies.While there is still a long way to go because of high production costs, we will do our best to further this technology now that we have achieved this success in the field of transparent energy storage, "said Professor Changsoon Choi of Daegu Gyeongbuk Institute of Science and Technology (DGIST).



Bibliography:

 Single-Layer Graphene-Based Transparent and Flexible Multifunctional Electronics for Self-Charging Power and Touch-Sensing Systems
Sungwoo Chun, Wonkyeong Son, Gwangyeob Lee, Shi Hyeong Kim, Jong Woo Park, Seon Jeong Kim, Changhyun Pang, Changsoon Choi ACS
Applied Materials & Interfaces
 DOI: 10.1021 / acsami.8b20143

Friday, 21 June 2019

World's Strongest Magnetic Field Generated From A Tiny Magnet

The recorded electromagnet is the size of an empty roll of toilet paper. [Image: MagLab]

World's Strongest Magnet

Engineers at the US High Magnetic Fields Laboratory (MagLab) built the Earth's strongest magnet with a record 45.5 teslas magnetic density flux.

Unlike its gigantic predecessor, the 45T, which held the record for almost two decades, the new configuration is much smaller and uses much less energy.

This was possible with the use of wires of a rare earth compound called copper-barium oxide (REBCO), which becomes superconducting at -196 ° C. This cold end also allows the creation of coils without the need of insulation - the coil reaches 1,260 A / mm2.


The small record holder, however, is not yet a full-fledged working magnet because he was only able to sustain his magnetic field for a few seconds. But the experiment showed that magnets made of copper oxide superconductors are a viable option for longer-lasting versions - the most common is to use niobium.

And it's good news considering that its predecessor, the 45T, which is fully functional, is a monster 6.7 meters tall and 35 tons that consumes 30 MW of energy - it's 15,000 liters of water pumped per minute to keep it going, refrigerated it.

Details of the construction of the strongest electromagnet in the world. [Image: Hahn et al. - 10.1038 / s41586-019-1293-1]

"We are really opening a new door. This technology has very good potential to completely change the horizons of high field applications because of its compact nature," said Seungyong Hahn, a MagLab engineer. 






Bibliography:

 45.5-tesla direct-current magnetic field generated with a superconducting high-temperature magnet
SEUNGYONG Hahn, Kwanglok Kim, Kwangmin Kim, Hu Xinbo, Thomas Painter, Iain Dixon, Seokho Kim, Kabindra R. Bhattarai, So Noguchi, Jan Jaroszynski, David C. Larbalestier 
Nature
 DOI: 10.1038 / s41586-019-1293-1

Wednesday, 19 June 2019

Plastic Laser finally becomes reality

This is the first time that laser emission is achieved in plastic or organic diodes. [Image: COPER / Kyushu University]

Researchers from Japan have demonstrated that an organic semiconductor-based laser diode is indeed possible, paving the way for the expansion of lasers in applications such as biosensors, screens, medical devices and optical communications.

Atula Sandanayaka and her colleagues at Kyushu University claim to have convincingly demonstrated for the first time that organic semiconductor laser diodes have finally come true - earlier allegations of electrically induced laser generation using organic materials have proved to be false on several occasions with other phenomena being confused with the laser emission.

A critical step in the laser is to inject a large amount of electrical current into the organic layers to achieve a condition called population inversion. However, the high resistance to electricity of many organic materials makes it difficult to get enough electrical charges on the materials before they warm up and burn - the organic materials are polymers, or plastics.

In addition, losses inherent to most organic materials and operation under high currents reduce efficiency, further increasing the required current.

Laser emission


To overcome these obstacles, Sandanayaka used a highly efficient organic light emitting material with relatively low resistance to electricity and a low amount of losses - the material is known as BSBCz (4,4'-bis [(N-carbazole) ] biphenyl).

But finding the right stuff was not enough.

He also had to design a grid structure of insulation material on one of the electrodes to inject electricity into the thin organic films. These networks - called distributed feedback structures - were already known to be capable of producing the necessary optical effects for the laser.

"By optimizing such networks, we were able to not only obtain the desired optical properties but also control the flow of electricity in the devices and minimize the amount of electricity needed to observe the laser emission from the thin organic film," said Professor Chihaya Adachi.

Organic laser prototype scheme and photo. [Image: 10.7567 / 1882-0786 / ab1b90] 

Organic laser diode

For a long time considered a "holy grail" in the area of ​​light emitting components, organic laser diodes use carbon-based materials to emit light instead of inorganic semiconductors such as arsenide and gallium nitride used in commercial devices.

Organic lasers are in many ways similar to organic light emitting diodes (OLEDs), in which a thin layer of organic molecules emits light when electricity is applied. OLEDs have become the best choice for cell phone screens because of their high efficiency and vibrant colors, which can be easily altered by synthesizing new organic molecules.

It turns out that organic laser diodes produce much purer light, allowing additional applications, but require currents with magnitudes higher than those used in OLEDs to achieve coherent light emission. These extreme conditions caused the prototypes built so far to sink well before the laser could be observed.

Researchers are so confident in their new components that they founded a company to make the missing developments to create a commercial product and launch the organic laser diodes in the market.


References:

Indication of current-injection lasing from an organic semiconductor
Atula SD Sandanayaka, Toshinori Matsushima, Fatima Bencheikh, Shinobu Terakawa, William J. Potscavage Jr., Chuanjiang Qin, Takashi Fujihara, Kenichi Goushi, Jean-Charles Ribierre, Chihaya Adachi
Applied Physics Express
DOI: 10.7567 / 1882-0786 / ab1b90

Tuesday, 18 June 2019

Biobateria produces clean electricity for days

Simple, small and efficient, the biobattery is ideal for the "internet of disposable things". [Image: Sean Choi]

Bio-battery or bio-cell?

The microbial batteries have been around for some time, but the emergence of the Internet of things can make them return to the headlines.

The good news is that bio-battery technology is not at a standstill, which has made them cheaper and more efficient.

"This new technique, built in the form of a small, compact, disposable package, at a low price, can cheaply connect things to work for a programmed period and then be discarded promptly," said Professor Seokheun Choi of Binghamton University, United States.


In fact, the new biobattery is in the middle between a battery and a microbial fuel cell - a bio-hybrid battery would be a good name.

The team had already developed paper biobanks and full-fledged microbial fuel cells .

"The bio-mass we developed this time is a kind of combined technique of these two, the pot life was significantly increased using solid-state compartments, but the device is a form of battery without complicated energy-consuming fluid-feeding systems and what typical microbial fuel cells require, "said Choi.

In other words, the team managed to get rid of the more complex part of the system.

"We have revolutionized the liquid anolyte, the salt bridge and the cathode compartment in solid counterparts, increasing their densities and enabling their slow and continuous reactions. In addition, the solid phase components will make the device suitable for miniaturization, integration and operation with the internet applications of solid-state things, "wrote the team.

Hybrid microbattery produced a maximum power density of 4 μW / cm 2 (0.3 mW / cm 3) and a current density of 45 μA / cm 2 (0.37 mA / cm 3) after 96 hours of operation, while the earlier, more complex, liquid-based version stopped generating power after 4 hours.




Bibliography:

A solid phase bacterium -based biobattery for low-power, low-cost, internet of Disposable Things
Maedeh Mohammadifar, Seokheun Choi
Journal of Power Sources
Vol .: 429, Pages 105-110
DOI: 10.1016 / j.jpowsour.2019.05. 009

Thursday, 13 June 2019

Cold fusion experiment fails, but Google will keep trying


Almost exactly 30 years ago, chemists Martin Fleischmann and Stanley Pons of the University of Utah in the United States gained instant worldwide fame by announcing that they had detected evidence of cold fusion.

The fusion of atomic nuclei occurs routinely in astrophysical environments, as in the stars, being considered the definitive and inexhaustible option of clean energy because, unlike the nuclear fission, that occurs in the reactors of the present atomic plants, it virtually does not produce radiation.

The joy lasted little because no other laboratory was able to reproduce the results claimed by Fleischmann and Pons. The issue continued to be investigated marginally, including a rare scientific event on cold fusion conducted in 2010.

Then in 2015, Google announced that it had assembled a group of about 30 scientists, from various universities and laboratories, and would do whatever was necessary for the team to develop a series of rigorous experiments that stipulated strictly the conditions under which cold fusion could eventually be carried out. And if the team could detect the phenomenon, a reference experiment would be developed that the broader academic community could examine, verify, and replicate.


The justification was that the lack of evidence of cold fusion is not the same as proof that it can not be realized. In addition, the need for cheaper, cleaner energy sources is more urgent than ever, and if cold fusion were possible, it could be a disruptive technology that could change the world.




Reassessment of cold fusion

The team has now published its results: They have been unable to find evidence of cold fusion - yet.

The "still" is important - the team believes that it is worthwhile to continue trying because the "initial trial [on the Fleischmann and Pons experiment] may have been premature", in addition to presenting arguments that the effort made so far has already feather.


"We have embarked on a multi-institutional program to re-evaluate cold fusion with a high standard of scientific rigor." Here we describe our efforts, which are yet to produce any evidence of such an effect. provide new insights into highly hydrated metals and low-energy nuclear reactions, and we affirm that there is still a lot of interesting science to be done in this unexplored parameter space, "the team wrote in its report, published in the journal Nature.




Cold fusion experiments

The team reports that it failed to reach the experimental parameters that appear to be the most suitable for achieving cold fusion - in fact, it seems extremely difficult to obtain these material conditions with the experimental settings idealized so far, although the team did not rule out this possibility .


Three experimental sets that had been proposed to generate cold fusion were explored, two involving palladium and hydrogen, and one involving metallic powders and hydrogen.

The first involved loading the palladium with amounts of deuterium supposedly necessary to trigger fusion. But the team was unable to create stable samples with the desired high palladium concentrations.

The second attempted to replicate a 1990s experiment in which physicists claimed to have generated anomalous levels of tritium - a heavy hydrogen isotope created only by nuclear reactions - bombarding palladium with pulses of deuterium hot ions. Nuclear signatures showed no evidence of tritium production.

One last line involved heating metallic powders in a hydrogen-rich environment, a process that some current proponents of cold fusion claim to produce excessive and unexplained heat, theorizing that this heat would be the result of the fusion of elements. But in 420 tests, the team did not detect any excess heat.

However, even following all the rigor proposed, the team claims that the negative results are not enough to discard the lines of experimentation using palladium. According to them, it is worth trying to improve the techniques for enriching palladium to obtain stable samples. In the other case, the hypothetical effects in the tritium experiment may be too small to be measured with the current equipment.

Scientific gains 

As for the scientific gains of the project to which the team refers in its report, there are calorimeters that operate in a robust and consistent way under extreme conditions that have had to be developed and that are now available for other experiments in several other fields.

The highly hydrated metals that the team obtained, in turn, could be useful in other works in the area of ​​energy, including batteries of flow and in the own hot fusion nuclear, that is being investigated in several enterprises around the world, like ITER and Wendelstein 7X , and even more ambitious and shorter-term proposals such as SPARC and HB11 .

Moreover, in broader terms, the scientific community gains back an area where research can be done again without the risk that its authors will be ridiculed at congresses. "The project can help responsible research in this general area become less taboo, even though the chances of achieving cold fusion still seem extremely remote," Nature wrote in its editorial.

By the way, just over a month ago, a team claimed to have obtained signals of nuclear fusion on a tabletop device using a totally different apparatus, known as "Z-clamp." 


Bibliography:
Revisiting the Cold Case of Cold Fusion Curtis P. Berlinguette, Yet-Ming Chiang, Jeremy N. Munday, Thomas Schenkel, David K. Fork, Ross Koningstein, Matthew D. Trevithick Nature DOI: 10.1038 / s41586-019-1256- 6

Monday, 10 June 2019

Experiment reverses the direction of heat flow - and time

Inversion of heat and time

A crucial experiment that had a major impact on the scientific environment, published here  was published by a peer-reviewed scientific journal.

The delay in publication may be explained by the effects of the international team led by Brazilian physicists: they have reversed the sense of heat and in doing so have shown that the concept of the time arrow can be seen as a relative concept , not necessarily traveling inescapably from the past into the future.

Thermodynamic time arrow



Heat flows from hot objects to cold ones. When a hot object comes into thermal contact with a cold, both evolve into an equilibrium configuration. The hot cools and the cold gets hot. This is a phenomenon of nature as evidenced by daily experience and explained by the second law of thermodynamics.

According to this law, the entropy of any single system always tends to increase with time until it reaches a maximum value. Entropy is the greatness that describes the degree of undifferentiation of a system. Isolated systems evolve spontaneously into increasingly undifferentiated states.

The experiment showed that quantum correlations affect the way the entropy is distributed between the parts in thermal contact, changing the sense of the so-called "thermodynamic arrow of time". In other words, heat can flow spontaneously from the cold to the warm body without the need to invest energy in the process, as it does in an ordinary refrigerator.

"In the macroscopic world described by classical physics, the input of external energy can invert the direction of a system's heat flow, causing it to flow from the cold to the hot. which occurs in a common refrigerator, for example.

"It is possible to say that in our nanoscopic experiment, quantum correlations produced an effect analogous to that of energy." The direction of flow was inverted, without this being a violation of the second law of thermodynamics. information in the description of heat transport, we find a generalized form of the second law, unraveling the role of quantum correlations in the process, "explains Professor Roberto Serra of UFABC.

Reversing heat and time


The experiment was carried out with a sample of chloroform molecules (one hydrogen atom, one carbon and three chlorine atoms) labeled with the carbon isotope 13. This sample was diluted in solution and studied by means of a nuclear magnetic resonance device, similar to those used in hospitals for imaging tests, but with a much more intense magnetic field.

"We investigated changes in the temperature of the spins of the hydrogen and carbon nuclei." Chlorine atoms did not play a relevant role in the experiment. Using radiofrequency pulses, we put the spins of each of the hydrogen and carbon nuclei at different temperatures, one more The temperature differences were very small, in the order of tens of billionths of a kelvin, but modern techniques make it possible to manipulate and measure quantum systems with extreme accuracy, in which case the radiofrequency oscillations produced by atomic nuclei, "said Serra.

The researchers explored two situations: one in which the two nuclei (hydrogen and carbon) started the process uncorrelated and another in which both were correlated in a quantum form.

"In the first case, of the uncorrelated nuclei, we observe the heat flowing in the usual sense, from hot to cold, until the two nuclei are at the same temperature. In the second case, with the two nuclei initially correlated, we observe the heat flowing in the opposite direction , from the cold to the hot.The effect lasted a few thousandths of a second until the initial correlation was consumed, "he said.

The most interesting thing about this result is that it allows us to think of a quantum cooling process in which the external energy input (which is the resource used in refrigerators and air conditioners to cool a given environment) is replaced by correlations, by exchanging information between objects.

Maxwell's Demon


The idea that information could be used to reverse the sense of heat flow - that is, to promote the local decrease in entropy - arose in classical physics at the end of the 19th century, at a time when there was not even an information theory. 

This occurred in a mental experiment proposed by James Clerk Maxwell (1831-1879), author, among other things, of the famous equations of classical electromagnetism. In this mental experiment, Maxwell stated that if there was a being able to know the individual velocity of each molecule of a gas and act on it on a microscopic scale, it could separate those molecules into two containers. On the one hand, it would put the molecules faster, creating a warm compartment. On the other, it would put the molecules slower, creating a cold compartment. In this way, the gas, initially in thermal equilibrium due to the mixture of fast and slow molecules, would evolve to a differentiated state, therefore, of less entropy. 

Maxwell's idea with this mental experiment was to prove that the second law of thermodynamics had a purely statistical character. 

"Being proposed by him, capable of intervening in the material world on a molecular or atomic scale, became known as ' Maxwell's Devil .' He was a fictional figure Maxwell invented to present his point of view. to act on these scales and even on smaller scales, modifying the usual expectations, "said Professor Serra.



The experiment that motivated the now published article is proof of this. The study did not reproduce Maxwell's mental experiment, but produced an analogous result.

"When we talk about information, we are not referring to something imponderable. Information needs a physical substrate, a memory. Today, to erase a bit of memory from a pendrive it is necessary to spend 10 thousand times a minimum amount of energy constituted by This minimum of energy required to erase information is known as the Landauer Principle, and therefore erasing information generates heat. Heating is what consumes most the battery of notebooks, "said Serra.

What the researchers observed was that the information present in the quantum correlations can be used to produce a task that, in this case, was to transfer heat from a colder object to a warmer object without external energy consumption.

"We can quantify the correlation of two systems by means of bits." Connections between quantum mechanics and information theory are now creating what the scientific community has called quantum information science . to be employed to cool part of a quantum computer processor in the future. "

Bibliography: 

Reversing the thermodynamic arrow of time using quantum correlations
Kaonan Micadei, John PS Peterson, Alexandre M. Souza, Roberto S. Sarthour, Ivan S. Oliveira, Gabriel T. Landi, Tiago B. Batalhão, Roberto M. Serra, Eric Lutz
Nature Communications
Vol. 1711.03323
DOI: 10.1038 / s41467-019-10333-7
https://arxiv.org/abs/1711.03323