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

Sunday, 15 March 2020

Researchers have found a way to efficiently produce hydrogen using rust and a light source.


Scientists identify a new and efficient way of producing hydrogen from organic waste solution using a catalyst derived from -- of all things -- rust

Production of hydrogen fuel is a key goal towards the development of sustainable energy practices, but this process does not have feasible techniques yet. A team of Japanese scientists from Tokyo University of Science, led by Prof Ken-ichi Katsumata, have identified a novel technique of using rust and light to speed up hydrogen production from organic waste solution, a finding that can revolutionize the clean energy industry.

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In today's narrative of climate change, pollution, and diminishing resources, one fuel could be a game-changer within the energy industry: hydrogen. When burned in a combustion engine or in an electrical power-plant, hydrogen fuel produces only water-making it far cleaner than our current fossil fuels. With no toxic gas production, no contribution to climate change, and no smog, hydrogen may be the answer to a future of cleaner energy, so why is it not more widely used?



There are two reasons for this. First, hydrogen is highly flammable and leaks very easily from storage tanks, causing potential explosion hazards during storage and transport. Second, although pure hydrogen occurs naturally on Earth, it is not found in quantities sufficient for cost-effective utilization. Hydrogen atoms must be extracted from molecules like methane or water, which requires a large amount of energy. Although several techniques exist to produce hydrogen fuel, scientists are yet to make this process "efficient" enough to make hydrogen a commercially competitive fuel on the energy market. Until this is achieved, fossil fuels will probably continue to dominate the industry.

For decades, scientists have been working towards a cheap, efficient, and safe way to produce hydrogen fuel. One of the most promising methods to achieve this is through solar-driven processes, using light to speed up (or "catalyze") the reaction to split water molecules into oxygen and hydrogen gas. In the 1970s, two scientists described the Honda-Fujishima effect, which uses titanium dioxide as a photocatalyst in hydrogen production. Building on this research, a team of Japanese researchers led by Prof Ken-ichi Katsumata of Tokyo University of Science, sought to use a cheaper, more readily available semiconductor catalyst for this reaction, with the hope to increase its efficiency even further, reducing the production costs and safety of hydrogen fuel. Their study published in Chemistry: A European Journal indicates that, by using a form of rust called α-FeOOH, hydrogen production under Hg-Xe lamp irradiation can be 25 times higher than titanium dioxide catalyst under the same light.

The experiment conducted by Prof Katsumata and colleagues aimed to address common challenges encountered in using semiconductor catalysts in solar-driven hydrogen production. There are three major obstacles described by the authors. The first is the need for the catalyst material to be suitable for the use of light energy. The second is that most photocatalysts currently used require rare or "noble" metals as cocatalysts, which are expensive and difficult to obtain. The last problem arises from the actual production of hydrogen and oxygen gases. If not separated straight away, the mixture of these two gases can at best reduce the hydrogen fuel output, and at worst, cause an explosion. Therefore, they aimed to find a solution that can not only increase the reaction's efficiency, but also successfully prevent hydrogen and oxygen from re-coupling and creating a potential hazard.

The team identified a promising candidate catalyst in α-FeOOH (or rust) and set out an experiment to evaluate its efficiency for hydrogen production and the optimal experimental conditions for its activation. "We were really surprised at the generation of hydrogen using this catalyst," states Prof Katsumata, "because most of the iron oxides are not known to reduce to hydrogen. Subsequently, we searched for the condition for activating α-FeOOH and found that oxygen was an indispensable factor, which was the second surprise because many studies showed that oxygen suppresses hydrogen production by capturing the excited electrons." The team confirmed the production mechanism of hydrogen from water-methanol solution using a 'gas-chromatography-mass-spectrometry' method, showing that α-FeOOH was 25 times more active than the titanium dioxide catalyst used in previous research, supporting stable hydrogen production for more than 400 hours!



More research will be required to optimize this process. Prof Katsumata elaborates: "The specific function of the oxygen in activating light-induced α-FeOOH has not been unveiled yet. Therefore, exploring the mechanism is the next challenge." For now, these findings of Katsumata and his colleagues represent new advancements in the production of a clean, zero-emissions energy source that will be central to the sustainable societies of the future!


Bibliography:

Hydrogen Production System by Light‐Induced α‐FeOOH Coupled with Photoreduction.

Tetsuya Yamada, Norihiro Suzuki, Kazuya Nakata, Chiaki Terashima, Nobuhiro Matsushita, Kiyoshi Okada, Akira Fujishima, Ken‐ichi Katsumata.

Chemistry – A European Journal, 2020;

DOI: 10.1002/chem.201903642

Sunday, 23 February 2020

New material doubles the battery life of electric vehicles


The anodes currently constituting most energy storage systems are made from graphite. However, this material is not the most optimal for ensuring long-term storage and stability during the many charge / discharge cycles. The alternative is silicon, a much more effective material, but suffering from certain defects preventing its commercialization. Recently, a team of Korean researchers has developed a series of very simple procedures using corn starch, making it possible to correct these defects and opening the way for a massive use of silicon in future batteries.

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Hun-Gi Jung and his research team at the Center for Energy Storage Research at the Korean Institute of Science and Technology (KIST) announced the development of silicon anodes that can quadruple the capacity of a battery, compared to graphite anode materials, and which allow rapid charging to over 80% of capacity in just five minutes. When applied to electric vehicle batteries, the new materials are expected to more than double their range.

The batteries currently installed in standard electric vehicles use graphite materials, but their low capacity contributes to the fact that electric vehicles have a shorter range than vehicles with internal combustion engines. Consequently, silicon, with an energy storage capacity 10 times greater than graphite, has attracted attention as a new generation material for the development of long-range electric vehicles.



Improving silicon capabilities with carbon-silicon composites

However, the silicon materials have not yet been marketed because their volume increases rapidly and the storage capacity decreases considerably during the charge and discharge cycles, which limits marketing. A number of methods have been suggested to improve the stability of silicon as an anode material, but the cost and complexity of these methods have prevented silicon from replacing graphite.

To improve the stability of silicon, Jung and his team focused on the use of common materials in our daily lives, such as water, oil and starch. They dissolved starch and silicon in water and oil, respectively, and then mixed and heated them in order to produce carbon-silicon composites. A simple thermal process used for frying food was employed to firmly fix the carbon and silicon, preventing the silicon anode materials from expanding during charge and discharge cycles.

Higher performance than graphite anodes
The composite materials developed by the research team demonstrated a capacity four-times greater than that of graphite anode materials (360mAh/g - 1,530mAh/g) and stable capacity retention over 500 cycles. It was also found that the materials enable batteries to charge to more than 80% capacity in only five minutes.  The results were published in the journal Nano Letters.


Structure and properties of the carbon-silicon hybrid developed by the researchers. Credits: Hyun Jung Kwon et al. 2020

Carbon spheres prevent the usual volume expansion of silicon, thereby enhancing the stability of silicon materials. Also, the use of highly conductive carbon and the rearrangement of the silicon structure resulted in a high output.

"We were able to develop carbon-silicon composite materials using common, everyday materials and simple mixing and thermal processes with no reactors," said Dr. Jung, the lead researcher of the KIST team. He continued, "The simple processes we adopted and the composites with excellent properties that we developed are highly likely to be commercialized and mass-produced. The composites could be applied to lithium-ion batteries for electric vehicles and energy storage systems (ESSs)."





Bibliography:

Nano/Microstructured Silicon–Carbon Hybrid Composite Particles Fabricated with Corn Starch Biowaste as Anode Materials for Li-Ion Batteries

Hyun Jung KwonJang-Yeon HwangHyeon-Ji ShinMin-Gi JeongKyung Yoon ChungYang-Kook Sun, Hun-Gi Jung

Nano Lett. 2020, 20, 1, 625-635
Publication Date:December 11, 2019

https://doi.org/10.1021/acs.nanolett.9b04395

Wednesday, 19 February 2020

New device generates electricity from moisture in the air


In the race for renewable energies, engineers are redoubling their inventiveness to find and exploit the energies freely available from the environment. But sometimes it's nature itself that gives scientists a boost. This is particularly the case of a very specific bacterium, Geobacter sulfurreducens, whose bacterial nanowires naturally conduct electricity. And researchers used these nanowires to create a device that generates electricity from the humidity of the air.

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This unusual bacterium, belonging to the genus Geobacter, was first spotted for its ability to produce magnetite in the absence of oxygen, but over time scientists discovered that it could also make other things, like bacterial nanowires that conduct electricity.

For years, researchers have tried to find ways to use this natural gift usefully. And they recently did it with a device called Air-gen.

According to the team, their device can generate electricity from practically nothing. “We literally generate electricity from the air. Air-gen generates clean energy 24/7,” said Jun Yao, electrical engineer at the University of Massachusetts. The study was published in the journal Nature.



Generate electricity via air humidity thanks to nanowires from G. sulfurreducens

The claim may seem exaggerated, but a new study by Yao and his team describes how the generator can indeed create electricity with nothing but the presence of air around it. All this thanks to the nanowires of electrically conductive proteins produced by Geobacter ( G. sulfurreducens, in this case).

The Air-gen consists of a thin film of protein nanowires measuring only 7 micrometers thick, positioned between two electrodes, but also exposed to air.

(A) Bacterial nanowires and generator structure. (B, C, D) Properties of the output voltage. Credits: Xiaomeng Liu et al. 2020


Due to this exposure, the nanowire film is capable of absorbing water vapor present in the atmosphere, allowing the device to generate a direct electric current conducted between the two electrodes. The team says the charge is likely created by a humidity gradient that causes protons to diffuse into the nanowire material.

"This diffusion of charges should induce an electric field of counterweight or a potential similar to that of membranes at rest in biological systems. A maintained humidity gradient, which is fundamentally different from anything seen in previous systems, explains the continuous output voltage of our nanowire device.”

Hydroelectric production more efficient than graphene

The discovery was made almost by accident, when Yao noticed that the devices he was experimenting with were conducting electricity apparently on their own. “I saw that when the nanowires were in contact with electrodes in a specific way, the devices generated a current. I found that exposure to atmospheric humidity was essential and that protein nanowires absorb water, producing a voltage gradient across the device.”

Properties of the voltage supplied by the generator. The generation of 0.5 V continuously allows powering small electronic devices. Credits: Xiaomeng Liu et al. 2020

Previous research has demonstrated the production of hydroelectric power using other types of nanomaterials - such as graphene, but these attempts have largely produced only short bursts of electricity, lasting only a few seconds. In contrast, the Air-gen produces a sustained voltage of approximately 0.5 V, with a current density of approximately 17 microamps per square centimeter.

Towards large-scale energy production

It doesn't take a lot of energy, but the team says connecting multiple devices could generate enough to charge small devices like smartphones and other personal electronics - all without wasting and using only ambient humidity (even in regions as dry as the Sahara Desert).

“The ultimate goal is to build systems on a large scale. Once we reach an industrial scale for the production of nanowires, I expect we will be able to build large generation systems that will make a major contribution to sustainable energy production," said Yao, explaining that the efforts future could use the technology to power homes via nanowires embedded in the mural.



If there is one obstacle to realizing this seemingly incredible potential, it is the limited amount of nanowires produced by G. sulfurreducens. Related research from one of the teams - microbiologist Derek Lovley, who first identified Geobacter bacteria in the 1980s - may have a solution: genetically designing other bacteria, such as E. coli, to perform the same process in larger proportions.


Bibliography:

Power generation from ambient humidity using protein nanowires.

Xiaomeng Liu, Hongyan Gao, Joy E. Ward, Xiaorong Liu, Bing Yin, Tianda Fu, Jianhan Chen, Derek R. Lovley, Jun Yao.

Nature, 2020;

DOI: 10.1038/s41586-020-2010-9

Friday, 14 February 2020

Movement of a liquid droplet on MoS2 generates over 5 volts of electricity


Japanese scientists have developed an energy capture device that generates more than 5 volts of electricity from a single drop of liquid rolling downhill. It was already known that a sheet of graphene can generate electricity from the movement of a liquid on its surface. However, the output voltage is limited to about 0.1 volts, which is not enough to drive electronic devices.

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The result was much better using molybdenite , or molybdenum disulfide (MoS2), as the active material in the nanogenerator, allowing to reach just over 5 volts of electricity from a drop of liquid rolling over the surface of the thin and flexible material - molybdenite is one of the stars of ultrafine electronics , surpassing graphene in several ways.

This voltage is important because it is at the level required for any electronic circuit, but the current generated by a single drop is also miniscule, with peaks of six nanowatts, which directs the nanogenerator for applications where there are continuous flows of liquids.



"To use MoS2 for the generator, it was necessary to form a large-area single-layer MoS2 film on a plastic film. With conventional methods, however, it was difficult to grow MoS2 uniformly on a large-area substrate," says Professor Ohno of the Institute of Materials and Systems for Sustainability at Nagoya University. "In our study, we succeeded in fabricating this form of MoS2 film by means of chemical vapor deposition using a sapphire substrate with molybdenum oxide (MoO3) and sulphur powders. We also used a polystyrene film as a bearing material for the MoS2 film, so that we were able to transfer the synthesized MoS2 film to the surface of the plastic film quite easily."

Harvesting Energy

The harvest of energy , incorporated in nanogenerators capable of transforming small amounts of naturally occurring energy (by light, heat and vibration) into electricity, is gaining attention as a method to power the Internet of Things (IoT) devices.

This technology is expected to have applications, for example, in autonomous and self-powered sensors, which will be able to work continuously without any concern with power or battery change.

The newly developed generator is flexible enough to be installed on the curved inner surface of plumbing, and is thus expected to be used to power IoT devices used in liquids, such as self-powered rain gauges and acid rain monitors, as well as water quality sensors that can generate power from industrial wastewater while monitoring it.



Professor Ohno says, "Our MoS2 nanogenerator is able to harvest energy from multiple forms of liquid motion, including droplets, spraying, and sea waves. From a broader perspective, this device could also be used in applications involving hydrodynamics, such as generating electricity from rainwater and waterfalls."


Bibliography:

Article: High output voltage generation of over 5 V from liquid motion on single-layer MoS2

Authors: Adha Sukma Aji, Ryohei Nishi, Hiroki Ago, Yutaka Ohno

Magazine: Nano Energy

Vol .: 68, 104370

DOI: 10.1016 / j. nanoen.2019.104370

Tuesday, 11 February 2020

New Electricity generator powers 100 small LED bulbs with a single drop of water

City University HK


Liquid water is omnipresent on Earth, from rivers to oceans through rain. However, the energy potential it contains is still insufficiently exploited. Recently, a team of Chinese engineers has developed a new method capable of harnessing the kinetic energy of water movements, such as falling raindrops, and converting it into electricity. A single drop of rain could thus power 100 LED bulbs.

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A single drop of rain can now power 100 small LED bulbs, setting a new milestone for energy generation technologies. The droplet-based electricity generator developed has a high energy conversion efficiency and a power density a thousand times greater than its counterparts. The study was published in the journal Nature .

The developers hope the technology will help tackle the global energy crisis by providing new ways to use the environmental energy that surrounds us in water and rain. The generator could be used in a variety of contexts where water meets a solid surface - such as on boat hulls, along coasts and even above shelters or umbrellas.

“Our research shows that a drop of 100 microliters of water released from a height of 15 centimeters can generate a voltage of more than 140 volts. The power generated can light up 100 small LED bulbs,” said Zuankai Wang, engineer at City University of Hong Kong.



Limited current hydroelectric technologies

Although the concept of hydroelectricity is not new - hydroelectric dams and tidal power plants operate around the world, the limitations of current technology have prevented us from taking full advantage of the available energy from waves and raindrops. This power is in the form of low frequency kinetic energy. “The kinetic energy caused by waterfalls is due to gravity and can be considered free and renewable. It should be used better.”

Conventional droplet energy generators take advantage of the triboelectric effect, in which electricity is generated when certain materials come into contact with each other, friction causing them to exchange electrons . Unfortunately, the size of the charge that can be generated on such surfaces is generally very limited, leading to very low energy conversion efficiency. The researchers' new energy recovery method overcomes these limitations in two different ways.

Optimized electricity generation thanks to polytetrafluoroethylene

First, the team used a material called polytetrafluoroethylene (or PTFE), which has an almost permanent electrical charge. They found that when drops hit the PTFE, the charges on its surface gradually accumulated until reaching a saturation point - which allowed them to overcome the bottleneck presented by the previous approaches, which could not accumulate only small charges.

(Left): the technology uses the kinetic energy generated by the drop of the drops on the electrodes in order to generate electricity. (Right): diagram of the structure of the PTFE-based device. Credits: City University HK


The second characteristic of the new method is its resemblance to a field effect transistor - a basic element of modern electronics and for which the 1956 Nobel Prize in physics was awarded. The design of the power generator includes two electrodes - one made of aluminum, the other made of tin and indium oxide with a PTFE coating, on which the charge is generated.

Many potential applications

When droplets fall on this last surface, they connect the two electrodes, transforming the original configuration into an electric circuit in a closed loop, releasing the stored charge and generating an electric current to power the LEDs. The researchers also found that the technique is not affected by lower relative humidities - and that it works with both rainwater and seawater.



According to the researchers, the concept could be used on various surfaces where liquids come into contact with solids, to fully exploit the low frequency kinetic energy that can be found in water. Professor Wang said he hopes the technology will help harvest energy from water to tackle the global problem of renewable energy shortages. Researchers have patented their technology in the United States and mainland China.


Bibliography:

Article: A droplet-based electricity generator with high instantaneous power density.

Authors: Wanghuai Xu, Huanxi Zheng, Yuan Liu, Xiaofeng Zhou, Chao Zhang, Yuxin Song, Xu Deng, Michael Leung, Zhengbao Yang, Ronald X. Xu, Zhong Lin Wang, Xiao Cheng Zeng & Zuankai Wang

Nature (2020).

https://doi.org/10.1038/s41586-020-1985-6

Monday, 10 February 2020

New droplet-based electricity generator Produces 1000 times more electricity than convectional systems



Researchers have designed a system that generates electricity from falling water drops. A drop is enough to light up 100 small LEDs. This is made possible by a combination of Teflon, the semiconductor indium tin oxide and an aluminum electrode. If a drop hits this ensemble, electrical current is generated. This opens up completely new ways of generating electricity, the researchers report in the journal "Nature".

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Electrical energy can be obtained from water - as evidenced by hydroelectric power plants at dams , run-of-river power plants or tidal power plants. Water can also be used to store energy. However, all of these systems require larger amounts of water to work efficiently. This is different with test systems that are based on the triboelectric effect : In these, the contact of certain materials with water causes an electrostatic charge and thus generates electricity - albeit in very small quantities.



Teflon, a semiconductor and a few pieces of aluminum

But there is another way: Researchers led by Zuankai Wang from City University Hong Kong have now developed a generator that generates electricity from individual drops of water - and this is a thousand times more efficient than previous approaches of this kind Drop generator on the interaction of water drops with certain materials.

Structure of the drop generator in the diagram and in the photo.

The device consists of a layer of indium tin oxide (ITO), on which the polymer polytetrafluoroethylene (PTFE) is applied - better known as Teflon. This electrically insulating material is a so-called electret, which can store electrical charges or accumulate, for example, through friction. A small piece of aluminum connects both layers and serves as an electrode.

Accumulating charges

If a drop of water falls on this ensemble, it spreads out on the water-repellent Teflon surface and creates an electrical charge through electrochemical interactions. In contrast to previous drop generators, this electrical energy is not lost after every drop, but accumulates. "With an increasing number of water drops hitting the surface, the charge increases," report Wang and his team. "After around 16,000 drops, the surface charge reaches a stable value of around 50 nanocoulombs."

Now a second process comes into play: The water spreading on the surface forms a bridge between the aluminum electrode and the ITO and Teflon layer. This creates an electrical circuit through which the charge can flow. As the researchers explain, the functioning of the system is similar to that of a field effect transistor. According to her, the drop generator achieves an energy density of 50 watts per square meter.

One drop lights up 100 LEDs

In initial tests, a prototype of this drop generator already generated a thousand times more energy than conventional systems: "A drop of 100 microliters of tap water that falls from a height of 15 centimeters can generate a voltage of 140 volts and a current of 270 microamperes," report Wang and his team. "This electrical energy is sufficient to make a hundred small LEDs light up."

According to the researchers, their drop generator can be used not only with tap water, but also for sea water and raindrops. They adapted the design for use in the rain so that the rainwater is first collected and then divided into small, regularly falling droplets by a capillary. Seawater can be dosed in a similar way.

"By adjusting the diameter of the capillary and the drop height, we can control the size and speed of the drops and thus the amount of energy generated," explains Wang and his colleagues.



Renewable, decentralized energy

According to the scientists, this technology opens up new possibilities for using the energy of water. "The kinetic energy of the falling water comes from gravity and can therefore be viewed as freely available and renewable," says Wang. “It should therefore be used better. Electricity from drops of water instead of oil or nuclear power could advance the sustainable development of the world."

The drop generator is particularly suitable for decentralized power generation. Wherever rain falls or there is water, it could be used to generate electrical energy - even on the hull of a ferry or on the surface of an umbrella.


Bibliography:

Xu, W., Zheng, H., Liu, Y. et al.

A droplet-based electricity generator with high instantaneous power density.

Nature (2020).

https://doi.org/10.1038/s41586-020-1985-6

Tuesday, 4 February 2020

Anti-solar cell: a photovoltaic cell that works at night



One of the major drawbacks of photovoltaic solar panels is that they do not produce electricity at night. The energy generated during the day must therefore be stored for use in the evening. What if we could develop solar panels that generate electricity at night? Jeremy Munday, professor in the Department of Electrical and Computer Engineering at UC Davis, says it is entirely possible. A specially designed photovoltaic cell could generate up to 50 watts of energy per square meter under ideal conditions at night, about a quarter of what a conventional solar panel can generate during the day.

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Munday, who recently joined UC Davis, is developing prototypes of these nocturnal solar cells capable of generating small amounts of energy. The researchers now hope to improve the power output and the efficiency of the system.

The operation would be similar to that of a normal solar cell, but involves a reverse process. An object that is warm relative to its surroundings will emit heat in the form of infrared light. A conventional solar cell is cold (compared to solar radiation), so it absorbs light.



Space is an extremely cold place, so if a hot object is pointed at the sky, it will radiate heat towards it. This phenomenon has been used in particular for night cooling for hundreds of years. "Over the past five years, there has been a lot of interest in devices that can generate energy during the day (by harnessing sunlight)," said Munday.

A conventional photovoltaic cell (left) absorbs photons from sunlight and generates an electric current. A thermoradiative cell (on the right) generates an electric current when it radiates infrared light (heat) towards the extreme cold of deep space. UC Davis engineers suggest that such cells could generate a significant amount of energy and help balance the power grid over the day-night cycle. Credits: Tristan Deppe / Jeremy Munday, UC Davis


Generate energy by radiating heat

There is another type of device called a “thermoradiative cell”, which generates energy by radiating heat to its environment. Researchers have notably explored its use to capture residual heat from engines.

"We said to ourselves, what if we took one of these cells and placed it in a hot area with the sky pointing at it," said Munday. This thermoradiative cell pointed towards the night sky would emit infrared radiation because it is hotter than outer space.

“An ordinary solar cell generates energy by absorbing sunlight, which causes voltage to appear across the device and the flow of current. In these new devices, the light is rather emitted and the current and voltage go in the opposite direction, but it still generates energy," said Munday. "It requires different materials, but the physics is the same."



The device would also work during the day, as long as direct sunlight is blocked. Because this new type of solar cell could potentially operate 24 hours a day, it is an attractive option for balancing the electrical network on the day-night cycle.


Bibliography:

Nighttime Photovoltaic Cells: Electrical Power Generation by Optically Coupling with Deep Space

Tristan Deppe Jeremy N. Munday*

ACS Photonics 2020, 7, 1, 1-9

Publication Date:November 20, 2019

https://doi.org/10.1021/acsphotonics.9b00679

Friday, 24 January 2020

New UV-C laser diode promises to disinfect your various health conditions

Structure and prototype of the UV-C laser diode. [Image: Asahi Kasei Corp / Nagoya University]


Japanese researchers made a laser diode that emits the shortest wavelength ultraviolet light ever achieved, covering an area of ​​applications that until now has not benefited from lasers.

These new devices could be used for health disinfection, treatment of skin diseases, such as psoriasis, and gas and DNA analysis.

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"Our laser diode emits the shortest wavelength in the world, at 271.8 nanometers (nm), under injection of alternating [electrical] current at room temperature," announced Professor Chiaki Sasaoka, from Nagoya University.

Previous efforts in the development of ultraviolet laser diodes have only managed to achieve emissions up to 336 nm, explains Sasaoka, not reaching the short-wavelength ultraviolet, or UV-C, which is in the range between 200 and 280 nm.


Material quality

To overcome the various problems that had been preventing the manufacture of this UV-C diode, the team used a high quality aluminum nitride (AlN) substrate as a basis to form the layers of the laser diode. The quality of the material was essential, since the lower quality AlN contains a large number of defects, which end up affecting the efficiency of the active layer of the laser diode in converting electrical energy into light energy.

In a laser diode the ‘p-type’ and ‘n-type’ layers are separated by a ‘quantum well’. When an electric current is passed through a laser diode, positively charged openings in the p-type layer and negatively charged electrons in the n-type flow flow to the center to connect, energy in the form of light particles called photons, is released.

The researchers designed quantum so well that it emitted deep UV light. P and N type layers consist of aluminum gallium nitride (AlGaN). The cladding layer, also made of AlGaN, is arranged on both sides of the p and n layers. The layer below the n-type layer contains silicon impurities, a process called doping. Doping is used as a technique to change material properties.

The layer above the p-type layer is subject to distributed polarization doping which touches the layer without adding impurity.

The aluminum content of the p-side layer is designed so that it is highest at the bottom and reduced at the top. The researchers believe that this aluminum gradient increases the flow of positively charged openings. Finally, a top contact layer was added, which consisted of p-type AlGaN magnesium alloy.



The researchers found that the doping of polarization - insertion of elements to change the behavior of the material - of the coating layer on the positive side ensured operation with a "remarkably low operating voltage" of 13.8V, and the emission "of the shortest length of wave reported so far ".

Asahi Kasei Corporation has already taken an interest in the project, and will help researchers develop deep UV lasers to come up with a commercial product.


Bibliography:

Article: A 271.8 nm deep-ultraviolet laser diode for room temperature operation

Authors: Ziyi Zhang, Maki Kushimoto, Tadayoshi Sakai, Naoharu Sugiyama, Leo J. Schowalter, Chiaki Sasaoka, Hiroshi Amano

Magazine: Applied Physics Express

DOI: 10.7567 / 1882 -0786 / ab50e0

Saturday, 14 December 2019

Scientists discovered cheaper way to make hydrogen from water


Researchers have discovered a cheaper way to make hydrogen from water: a team of scientists led by the UNSW has demonstrated a sustainable way to get hydrogen, which is necessary, among other things, for fueling vehicles hydrogen.

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Scientists from UNSW Sydney, Griffith University and Swinburne University of Technology have demonstrated that the capture of hydrogen by separating it from oxygen in water can be done using low-metals cost like iron and nickel (as catalysts), which speeds up the chemical reaction, while requiring less energy.

It should be noted that iron and nickel, which are found in abundance on Earth, would replace ruthenium, platinum and iridium, precious metals which until now have been considered as reference catalysts in the process of "Water fractionation".



Professor Chuan Zhao, of the UNSW School of Chemistry, explains that in water fractionation, two electrodes apply an electrical charge to the water, which allows the hydrogen to be separated from the water. 'oxygen. It can then be used as an energy carrier in a fuel cell.

“ What we do is coat the electrodes with our catalyst to reduce energy consumption. On this catalyst, there is a tiny nanoscale interface where iron and nickel meet at the atomic level, which then becomes an active site for water separation: this is where hydrogen can be separated from oxygen and captured as fuel, and oxygen can be released as environmentally friendly waste,” he explains.

Iron and nickel, but on a nanometric scale

Already in 2015, Professor Zhao's team invented a nickel-iron electrode for generating oxygen with unprecedented efficiency. However, Zhao believes that iron and nickel alone are not good enough catalysts for the generation of hydrogen, but that it is when they meet on the nanometric scale that the “magic operates ".

Nanoparticle design and electron microscopies. a Schematic representation of the Ni and Fe nanoparticles and the Ni-Fe Janus nanoparticles synthesis through the oleate-assisted micelle formation and the illustration on the HER across the Ni-γ-Fe2O3 interface in alkaline medium. b STEM-HAADF image of a single Ni–Fe NP nanoparticle and its corresponding EDS line-scan spectrum (scale bar: 1 nm). c High-resolution EDS mapping on STEM-HAADF images of the nanoparticles for Ni and Fe, selected area electron diffraction inset (image scale bars: 20 nm; SAED scale bar: 2 nm−1).


The nanoscale interface fundamentally changes the properties of these materials. Our results show that the nickel-iron catalyst can be as active as platinum in the generation of hydrogen,  ”he explains. "  An added benefit is that our nickel-iron electrode can catalyze both hydrogen and oxygen generation, so not only could we reduce production costs by using elements that are abundant on Earth, but also allow the use of one catalyst instead of two . ”

And indeed: a quick glance at current metal prices clearly demonstrates why this could be the change needed to accelerate the transition to the so-called hydrogen economy. Iron and nickel are priced at € 0.12 and € 19.65 per kilogram respectively. On the other hand, ruthenium, platinum and iridium are priced at € 10.6, € 37.9 and € 62.6 per gram respectively. In other words, thousands of times more expensive.



“ Right now, in our fossil fuel economy, we have this great incentive to move to a hydrogen economy so that we can use hydrogen as a clean and abundant energy carrier on Earth. Many people have been talking about the hydrogen economy for ages, but this time it seems like it really does happen  , "said Professor Zhao.

According to him, if water separation technology is developed, there could one day be hydrogen refueling stations (just like the service stations we know today), where we could refuel our hydrogen vehicles with hydrogen produced by this water division reaction. This could be done in a few minutes, compared to recharging hours in the case of electric cars with lithium battery.


Bibliography:

Overall electrochemical splitting of water at the heterogeneous interface of nickel and iron oxide
Bryan H. R. Suryanto, Yun Wang, Rosalie K. Hocking, William Adamson & Chuan Zhao

Nature Communications volume 10, Article number: 5599

http://dx.doi.org/10.1038/s41467-019-13415-8

Thursday, 12 December 2019

New study: Energy can be stored in the mountains using sand

Energy can be stored as sand or water for as long as needed.

Store energy in the mountains

Storing energy for long periods of time is one of the biggest challenges for a permanent move to a renewable and environmentally friendly energy matrix.

Solar energy, wind energy, wave energy, tidal energy and others are widely available, but they cannot maintain a constant supply of energy needed to meet the continuing demand of society.

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Julian Hunt and colleagues from Austria, Denmark and Italy believe they have come up with a suitable solution for situations where current alternatives do not apply - such as underwater hydropower , flow batteries and various ways of " storing the wind ", for example. .

The concept was named MGES for "mountain gravity energy storage" - and can be combined with a hydroelectric dam.


Generate electricity with sand

MGES consists of placing cranes on the edge of a steep mountain with sufficient reach to carry sand (or gravel) from a base storage to a mountain top storage location. An engine / generator moves sand-filled storage containers from the bottom up, similar to a cable car.

During this process, the potential energy is stored. Electricity is generated by lowering the sand from the upper storage location back to the base, harnessing the energy of the descending containers like a zip line.

If there are streams in the mountain, the MGES system can be hybridized with hydropower, where water would be used to fill storage containers in periods of high availability rather than sand or gravel, generating power.

MGES systems have the benefit that water can be added at any time in the system, thus increasing the possibility of capturing water from different heights on the mountain, which is not possible with conventional hydroelectric dams.

The nuclear fusion continues in a very distant future, so there are those who still bet on cold fusion

Sand does not evaporate

"One of the benefits [of the MGES system] is that sand is cheap and, unlike water, doesn't evaporate - so you never lose potential energy, and it can be reused countless times. That makes it particularly interesting for dry regions.

"In addition, hydroelectric plants are limited to a height difference of 1,200 meters due to very high hydraulic pressures. MGES plants can have height differences of more than 5,000 meters.

"Regions with high mountains, for example the Himalayas, Alps and Rockies, could therefore become important long-term energy storage centers. Other interesting places for MGES are islands such as Hawaii, Cape Verde, Madeira and the Isles. Pacific, with steep mountain terrain, "detailed Hunt.

To test the concept, the team proposed a future energy matrix for Molokai Island in Hawaii, using only wind , solar , batteries and MGES to meet the island's energy demand.

Although designed to store electricity on a large scale, liquid batteries are being tested in electric cars

Store energy

Hunt emphasizes that MGES technology is not suitable for meeting peak demand or storing energy in daily cycles; Its main advantage is to fill a gap in the market as a long term energy storage location.

MGES systems could, for example, store energy continuously for months and then generate electricity continuously for months or when water is available for hydropower, while batteries would handle daily storage cycles.



"It's important to note that MGES technology does not replace current energy storage options, but opens up new ways to store energy and harness untapped water potential in high mountain regions," said Hunt.




Bibliography:

Article: Mountain Gravity Energy Storage: A new solution for closing the gap between existing short- and long-term storage technologies

Authors: Julian David Hunt, Behnam Zakeri, Giacomo Falchett, Andreas Nascimento, Yoshihide Wada, Keywan Riahi

Journal: Nature Energy

DOI: 10.1016 / j.energy.2019.116419

Saturday, 23 November 2019

First superconducting wind generator successfully tested

The superconducting generator is smaller and lighter than the equivalent of permanent magnets

Superconducting Wind Generator

A superconducting wind generator was successfully tested for the first time on an active, full-scale turbine.

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The 3.6 megawatt superconducting generator is designed, developed and manufactured by the European consortium EcoSwing, and field tested in Thyboron, Denmark.

"The size of wind turbines has increased significantly in recent decades. However, current technology has been having trouble keeping up with the trend of increasing levels of energy per unit," said Anne Bergen of the University of Twente in the Netherlands. Low.

To meet this challenge, the team built a “high temperature” (-196 ° C) barium oxide ( ReBCO ) superconducting wired generator , one of the rare earth family members.

This option required fewer rare earth materials than permanent magnet wind generators - also built with materials from the same family - resulting in a lower cost. The superconducting can also carry high current densities, resulting in denser in coil power and a smaller weight.

The union of universities and companies in the project allowed technology to be transferred from laboratories to industry

From lab to factory

"The generator field test was extremely successful. When the generator was installed at Thyboron, the turbine reached its desired power range, including over 650 hours of grid operation. This shows the compatibility of the superconducting generator technology with all elements of an operating environment such as variable speeds, grid failures, electromagnetic harmonics and vibrations, "said Bergen.

But the advances were not limited to the technical part of the generator.

"He demonstrated that the production of high temperature superconducting coils is not limited to specialized laboratories, but constitutes a successful technology transfer from science to industry. The high temperature superconducting rotor has also been assembled in an industrial environment, showing that Superconducting components can be deployed in a standard manufacturing environment.

"Now that the concept has been proven, we expect superconducting generator technology to begin to be widely applied to wind turbines ," added Bergen.


Bibliography:

Article: Design and in-field testing of the world's first ReBCO rotor for a 3.6 MW wind generator

Authors: Anne Bergen, Rasmus Andersen, Markus Bauer, Hermann Boy, Marcel ter Brake, Patrick Brutsaert, Carsten Bührer, Marc Dhallé, Jesper Hansen, Herman ten Kate, Jürgen Kellers, Jens Krause, Erik Krooshoop, Christian Kruse, Hans Kylling, Martin Pilas, Hendrik Pütz, Anders Rebsdorf, Michael Reckhard, Eric Seitz, Helmut Springer, Nir Tzabar, Sander Wessel, Jan Wiezoreck , Tiemo Winkler, Konstantin Yagotyntsev

Magazine: Superconductor Science and Technology

Vol .: 32, Number 12

DOI: 10.1088 / 1361-6668 / ab48d6

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.



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