February 23, 2017 | Leave a Comment
University of Kent scientists have discovered how bacteria make a component that facilitates converting carbon dioxide (CO2) into methane gas for energy use. Recycling CO2 back into energy has immense potential for making these emissions useful rather than a major factor in global warming.
So far the bacteria called methanogens, that can convert CO2 into methane are notoriously difficult to grow, their use in gas production remains extremely limited.
The methanogen cultivation challenge inspired the team of scientists led by Professor Martin Warren, of the University of Kent’s School of Biosciences, to investigate how a key molecule, coenzyme F430, is made in these bacteria.
Although F430 – the catalyst for the production process – is structurally very similar to the red pigment found in red blood cells (haem) and the green pigment found in plants (chlorophyll), the properties of this bright yellow coenzyme allows methanogenic bacteria to breathe in carbon dioxide and exhale methane.
By understanding how essential components of the methanogenensis process of biological methane production such as coenzyme F430 are made, scientists are one step closer to being able to engineer a more effective and obliging methane-producing bacterium.
The research team has shown that coenzyme F430 is made from the same starting molecular template from which haem and chlorophyll are derived, but uses a different suite of enzymes to convert this starting material into F430. Key to this process is the insertion of a metal ion, which is glued into the center of the coenzyme.
If the methanogenesis process of biological methane production could be engineered into bacteria that are easier to grow, such as the microbe E. coli, then engineered strains could be employed to catch carbon dioxide emissions and convert them into methane for energy production.
This breakthrough is in reality a discovery of the molecule and its function, not the genetic code the bacteria use to make it. It won’t take long to isolate that. That’s when the genetic engineering gets underway and learning if this molecule alone will produce methane or if more code is needed to get to a scalable type of bacteria.
February 22, 2017 | Leave a Comment
University of Southern California (USC) scientists have developed an alteration to the lithium-sulfur battery that could make it more than competitive with the lithium-ion battery. The solution is for one of the biggest stumbling blocks to the next wave of rechargeable batteries – small enough for cellphones and powerful enough for cars.
In a paper published in the January issue of the Journal of the Electrochemical Society, Sri Narayan and Derek Moy of the USC Loker Hydrocarbon Research Institute outline how they developed an alteration to the lithium-sulfur battery that could make it more than competitive with the industry standard lithium-ion battery.
The lithium-sulfur battery, long thought to be better at energy storage capacity than its more popular lithium-ion counterpart, has been hampered by its short cycle life. Currently the lithium-sulfur battery can be recharged 50 to 100 times – impractical as an alternative energy source compared to 1,000 times for many rechargeable batteries on the market today.
The solution devised by Narayan and lead author and research assistant Moy is something they call the “Mixed Conduction Membrane,” or MCM, a small piece of non-porous, fabricated material sandwiched between two layers of porous separators, soaked in electrolytes and placed between the two electrodes.
The membrane works as a barrier in reducing the shuttling of dissolved polysulfides between anode and cathode, a process that increases the kind of cycle strain that has made the use of lithium-sulfur batteries for energy storage a challenge. The MCM still allows for the necessary movement of lithium ions, mimicking the process as it occurs in lithium-ion batteries. This novel membrane solution preserves the high-discharge rate capability and energy density without losing capacity over time.
At various rates of discharge, the researchers found that the lithium-sulfur batteries that made use of MCM led to 100 percent capacity retention and had up to four times longer life compared to batteries without the membrane.
Narayan, senior author and professor of chemistry at the USC Dornsife College of Letters, Arts and Sciences said, “This advance removes one of the major technical barriers to the commercialization of the lithium-sulfur battery, allowing us to realize better options for energy efficiency. We can now focus our efforts on improving other parts of lithium-sulfur battery discharge and recharge that hurt the overall life cycle of the battery.”
Professor Narayan summed it up well. But left out the huge closing of the gap he and Moy have accomplished cutting the needed improvement from 10 to 20 times down to 3 to 5. The Lithium Sulfur technology may well soon be the better alternative.
February 21, 2017 | 1 Comment
Georgia Institute of Technology scientists have transformed an internal combustion engine into a modular reforming reactor that could make hydrogen available to power fuel cells wherever there’s a natural gas supply available.
Unlike conventional engines that run at thousands of revolutions per minute, the reactor operates at only a few cycles per minute – or more slowly – depending on the reactor scale and required rate of hydrogen production. And there are no spark plugs because there’s no fuel combusted.
Key to the reaction process named CHAMP, is the variable volume provided by a piston rising and falling in a cylinder. As with a conventional engine, a valve controls the flow of gases into and out of the reactor as the piston moves up and down. The four-stroke system works like this:
- Natural gas (methane) and steam are drawn into the reaction cylinder through a valve as the piston inside is lowered. The valve closes once the piston reaches the bottom of the cylinder.
- The piston rises into the cylinder, compressing the steam and methane as the reactor is heated. Once it reaches approximately 400º C, catalytic reactions take place inside the reactor, forming hydrogen and carbon dioxide. The hydrogen exits through a selective membrane, and the pressurized carbon dioxide is adsorbed by the sorbent material, which is mixed with the catalyst.
- Once the hydrogen has exited the reactor and carbon dioxide is tied up in the sorbent, the piston is lowered, reducing the volume (and pressure) in the cylinder thus releasing the carbon dioxide from the sorbent into the cylinder.
- The piston is again moved up into the chamber and the valve opens, expelling the concentrated carbon dioxide and clearing the reactor for the start of a new cycle.
“All of the pieces of the puzzle have come together,” said Fedorov, a professor in Georgia Tech’s George W. Woodruff School of Mechanical Engineering. “The challenges ahead are primarily economic in nature. Our next step would be to build a pilot-scale CHAMP reactor.”
By adding a catalyst, a hydrogen separating membrane and carbon dioxide sorbent to the over a century-old four-stroke engine cycle, researchers have demonstrated a laboratory-scale hydrogen reforming system that produces the green fuel at relatively low temperature in a process that can be scaled up or down to meet specific needs.
The process could provide hydrogen at the point of use for residential fuel cells or neighborhood power plants, electricity and power production in natural-gas powered vehicles, fueling of municipal buses or other hydrogen-based vehicles, and supplementing intermittent renewable energy sources such as photovoltaics.
Known as the CO2/H2 Active Membrane Piston (CHAMP) reactor, the device operates at temperatures much lower than conventional steam reforming processes, consumes substantially less water and could also operate on other fuels such as methanol or bio-derived feedstock. It also captures and concentrates carbon dioxide emissions, a by-product that now lacks a secondary use – though that could change in the future.
Professor Fedorov said, “We already have a nationwide natural gas distribution infrastructure, so it’s much better to produce hydrogen at the point of use rather than trying to distribute it. Our technology could produce this fuel of choice wherever natural gas is available, which could resolve one of the major challenges with the hydrogen economy.”
The team’s paper, published in the journal Industrial & Engineering Chemistry Research, describes the operating model of the CHAMP process, including a critical step of internally adsorbing carbon dioxide, a byproduct of the methane reforming process, so it can be concentrated and expelled from the reactor for capture, storage or utilization.
The project was begun to address some of the challenges to the use of hydrogen in fuel cells. Most hydrogen used today is produced in a high-temperature reforming process in which methane is combined with steam at about 900º C. The industrial-scale process requires as many as three water molecules for every molecule of hydrogen, and the resulting low density gas must be transported to where it will be used.
Fedorov’s lab first carried out thermodynamic calculations suggesting that the four-stroke process could be modified to produce hydrogen in relatively small amounts where it would be used. The goals of the research were to create a modular reforming process that could operate at between 400 and 500º C, use just two molecules of water for every molecule of methane to produce four hydrogen molecules, be able to scale down to meet the specific needs, and capture the resulting carbon dioxide for potential utilization or sequestration.
Fedorov said, “We wanted to completely rethink how we designed reactor systems. To gain the kind of efficiency we needed, we realized we’d need to dynamically change the volume of the reactor vessel. We looked at existing mechanical systems that could do this, and realized that this capability could be found in a system that has had more than a century of improvements: the internal combustion engine.”
The CHAMP system could be scaled up or down to produce the thousands of kilograms of hydrogen per day required for a typical automotive refueling station – or a few kilograms for an individual vehicle or residential fuel cell, Fedorov explained. The volume and piston speed in the CHAMP reactor can be adjusted to meet hydrogen demands while matching the requirements for the carbon dioxide sorbent regeneration and separation efficiency of the hydrogen membrane. In practical use, multiple reactors would likely be operated together to produce a continuous stream of hydrogen at a desired production level.
“We took the conventional chemical processing plant and created an analog using the magnificent machinery of the internal combustion engine,” Fedorov said. “The reactor is scalable and modular, so you could have one module or a hundred of modules depending on how much hydrogen you needed. The processes for reforming fuel, purifying hydrogen and capturing carbon dioxide emission are all combined into one compact system.”
Other implementations of the system have been reported as thesis work by three Georgia Tech Ph.D. graduates since the project began in 2008. The research was supported by the National Science Foundation, the Department of Defense through NDSEG fellowships, and the U.S. Civilian Research & Development Foundation (CRDF Global).
Well now, this just might work at commercial scale. Anywhere there is natural gas supplied with electric power and water you would have a viable system. Until natural gas gets expensive again.
February 16, 2017 | 1 Comment
Georgia Institute of Technology scientists have developed an anode material that enables sodium-ion batteries to perform at high capacity over hundreds of cycles. Lithium-ion batteries have become essential in everyday technology. But these power sources can explode under certain circumstances and are not ideal for grid-scale energy storage. Sodium-ion batteries are potentially a safer and less expensive alternative, but current versions don’t last long enough yet for practical use.
Meilin Liu, Chenghao Yang and their colleagues wanted to find an anode material that would give sodium-ion batteries a longer life. The colleagues hail from Georgia Institute of Technology, New Energy Research Institute, School of Environment and Energy, South China University of Technology and Department of Chemistry, National Taiwan Normal University.
For years, scientists have considered sodium-ion batteries a safer and lower-cost candidate for large-scale energy storage than lithium-ion. But so far, sodium-ion batteries have not operated at high capacity for long-term use. Lithium and sodium have similar properties in many ways, but sodium ions are much larger than lithium ions. This size difference leads to the rapid deterioration of a key battery component.
The researchers developed a simple approach to making a high-performance anode material by binding an antimony-based mineral onto sulfur-doped graphene sheets. Incorporating the anode into a sodium-ion battery allowed it to perform at 83 percent capacity over 900 cycles. The researchers say this is the best reported performance for a sodium-ion battery with an antimony-based anode material. To ultimately commercialize their technology, they would need to scale up battery fabrication while maintaining its high performance.
The team’s development is closing in on three years of life with daily charge and discharge cycling. Still in its lab stage of development the technology has lots of work yet to be done. For now the tech is very hopeful, some applications simply can’t tolerate the lithium-ion risk, getting those kinds of devices a higher power lower weight battery is a worthwhile effort, indeed.
University of Illinois at Urbana-Champaign (UI) researchers have invented a new kind of LED that can both emit and detect ambient light. The possibility then becomes that cellphones and other devices could soon be controlled with touchless gestures and charge themselves using ambient light. This would be a major design attribute for the future. Made of tiny nanorods arrayed in a thin film, the LEDs could enable new interactive functions and multitasking devices.
Moonsub Shim, a professor of materials science and engineering at the UI and the leader of the study said, “These LEDs are the beginning of enabling displays to do something completely different, moving well beyond just displaying information to be much more interactive devices. That can become the basis for new and interesting designs for a lot of electronics.”
The tiny nanorods, each measuring less than 5 nanometers in diameter, are made of three types of semiconductor material. One type emits and absorbs visible light. The other two semiconductors control how charge flows through the first material. The combination is what allows the LEDs to emit, sense and respond to light.
The nanorod LEDs are able to perform both functions by quickly switching back and forth from emitting to detecting. They switch so fast that, to the human eye, the display appears to stay on continuously – in fact, it’s three orders of magnitude faster than standard display refresh rates. Yet the LEDs are also near-continuously detecting and absorbing light, and a display made of the LEDs can be programmed to respond to light signals in a number of ways.
For example, a display could automatically adjust brightness in response to ambient light conditions – on a pixel-by-pixel basis.
Shim explained, “You can imagine sitting outside with your tablet, reading. Your tablet will detect the brightness and adjust it for individual pixels. Where there’s a shadow falling across the screen it will be dimmer, and where it’s in the sun it will be brighter, so you can maintain steady contrast.”
The researchers demonstrated pixels that automatically adjust brightness, as well as pixels that respond to an approaching finger, which could be integrated into interactive displays that respond to touchless gestures or recognize objects.
They also demonstrated arrays that respond to a laser stylus, which could be the basis of smart whiteboards, tablets or other surfaces for writing or drawing with light. And the researchers found that the LEDs not only respond to light, but can convert it to electricity as well.
“The way it responds to light is like a solar cell. So not only can we enhance interaction between users and devices or displays, now we can actually use the displays to harvest light,” Shim said. “So imagine your cellphone just sitting there collecting the ambient light and charging. That’s a possibility without having to integrate separate solar cells. We still have a lot of development to do before a display can be completely self-powered, but we think that we can boost the power-harvesting properties without compromising LED performance, so that a significant amount of the display’s power is coming from the array itself.”
In addition to interacting with users and their environment, nanorod LED displays can interact with each other as large parallel communication arrays. It would be slower than device-to-device technologies like Bluetooth, Shim said, but those technologies are serial – they can only send one bit at a time. Two LED arrays facing each other could communicate with as many bits as there are pixels in the screen.
Study coauthor Peter Trefonas, a corporate fellow in Electronic Materials at the Dow Chemical Company said, “We primarily interface with our electronic devices through their displays, and a display’s appeal resides in the user’s experience of viewing and manipulating information. The bidirectional capability of these new LED materials could enable devices to respond intelligently to external stimuli in new ways. The potential for touchless gesture control alone is intriguing, and we’re only scratching the surface of what could be possible.”
The researchers did all their demonstrations with arrays of red LEDs. They are now working on methods to pattern three-color displays with red, blue and green pixels, as well as working on ways to boost the light-harvesting capabilities by adjusting the composition of the nanorods.
This is an astonishing development. The possibility to have a cellphone that would charge up as it is standing by or even while in use is a bit numbing. Your humble writer is always, yes, always planning cellphone use so as to make it to the next charge without a shutdown.
The potentials other applications is also a bit numbing. Congratulations UI Urbana-Champaign and Dow Electronic Materials. Very happy you have collaborated and have obtained such an impressive result.