October 24, 2017
MicroLink Devices opens the door for new multijunction solar cell applications
October 24, 2017
The U.S. Department of Energy’s (DOE) National Renewable Energy Laboratory (NREL) has entered into a license agreement with MicroLink Devices, Inc. (Niles, IL) to commercialize NREL’s patented inverted metamorphic (IMM) multijunction solar cells.
While high-efficiency multijunction solar cells are commonly used for space satellites, researchers have continued to look for ways to improve cost and performance to enable a broader range of applications.
The IMM technique licensed by MicroLink Devices enables multijunction III-V solar cells to be grown with both higher efficiencies and lower costs than traditional multijunction solar cells by reversing the order in which individual sub-cells are typically grown.
Two hands holding the IMM solar cellA 6-inch MicroLink Devices high-efficiency, lightweight and flexible ELO IMM solar cell wafer. Photo courtesy of MicroLink Devices
The IMM architecture enables greater power extraction from the higher-bandgap sub-cells and further allows the use of more efficient low-bandgap sub-cell materials such as Indium Gallium Arsenide.
In contrast to traditional III-V multijunction solar cells, IMM devices are removed from their growth substrate, allowing the substrate to be reused over multiple growth runs – a significant component in reducing overall device costs. Removing the substrate also reduces the weight of the solar cell, which is important for applications such as solar-powered unmanned aerial vehicles.
MicroLink Devices is an Illinois-based ISO 9001 certified semiconductor manufacturer specializing in removing active semiconductor device layers from their growth substrate via a proprietary epitaxial liftoff (ELO) process.
By utilizing its ELO capabilities, MicroLink will be able to make thin, lightweight, and highly flexible IMM solar cells which are ideal for use in unmanned aerial vehicles, space-based vehicles and equipment, and portable power generation applications.
“IMM makes multijunction solar cells practical for a wide variety of weight-, geometry-, and space-constrained applications where high efficiency is critical,” said Jeff Carapella, one of the researchers in NREL’s III-V multijunction materials and devices research group that developed the technology.
“Former NREL Scientist Mark Wanlass pioneered the use of metamorphic buffer layers to form tandem III-V solar cells with three or more junctions.
This approach is very synergistic with our ELO process technology, and MicroLink Devices is excited to now be commercializing IMM solar cells for high-performance space and UAV applications,” said Noren Pan, CEO of MicroLink Devices.
MicroLink and NREL have collaborated to evaluate the use of ELO for producing IMM solar cells since 2009, when MicroLink was the recipient of a DOE PV Incubator subcontract from NREL.
Tests of MicroLink-produced IMM solar cells conducted at NREL have demonstrated multiple successful substrate reuses and efficiencies exceeding 30%.
NREL has more than 800 technologies available for licensing and continues to engage in advanced research and development of next-generation IMM and ultra-high-efficiency multijunction solar cells with both academic and commercial collaborators.
Companies interested in partnering to advance research on or commercialize renewable energy technologies can visit the EERE Energy Innovation Portal, which features descriptions of all renewable energy technologies funded by the DOE’s Office of Energy Efficiency and Renewable Energy.
Parties interested specifically in ongoing development of IMM solar cells can contact Dan Friedman, Manager of NREL’s High Efficiency Crystalline Photovoltaics Group, for more information.
NREL is the U.S. Department of Energy’s primary national laboratory for renewable energy and energy efficiency research and development. NREL is operated for the Energy Department by The Alliance for Sustainable Energy, LLC.
With Tesla purportedly gearing up to introduce an all-electric semi next month, diesel engine supplier Cummins took some of the automaker’s buzz away on Tuesday, revealed an all-electric prototype truck of its own.
Billed as a Class 7 Urban Hauler Tractor, the 18,000-pound truck was built by Roush and is geared for local deliveries, according to the Indianapolis Star. The company said it plans to begin selling a 140 kWh battery pack for bus operators and commercial truck fleets in 2019, reports Forbes.
With a claimed range of 100 miles, it certainly seems apt to handle short drives, and Cummins said it only takes an hour to charge. By the time it’s introduced in 2020, Forbes reports, the company hopes to drop that number to 20 minutes.
A hybrid, with a diesel engine used on-board as a generator, is planned later and will offer 300 miles in range.
Cummins’ chief exec, Thomas Linebarger, told Forbes that electric technology isn’t quite ready for 18-wheelers, mostly due to the long distances they travel. Tesla’s truck will reportedly be set to handle lengthier tasks, with 200 to 300 miles on a single charge, but that remains far below the 1,000 miles a typical heavy-duty truck can handle on one tank of gas.
Cummins may have introduced a prototype truck cab to show off, but the company only intends to produce the powertrain for trucks, Forbes reports.
WHICH is the world’s most innovative country? Answering this question is the aim of the annual Global Innovation Index and a related report, which were published this morning by Cornell University, INSEAD, a business school, and the World Intellectual Property Organisation.
The ranking of 140 countries and economies around the world, which are scored using 79 indicators, is not surprising: Switzerland, Britain, Sweden, the Netherlands and America lead the pack.
But the authors also look at their data from other angles, for instance how countries do relative to their economic development and the quality of innovation (measured by indicators such as university rankings). In both cases the results are more remarkable. The chart above shows that in innovation many countries in Africa punch above their economic weight. And the chart below indicates that, even though China is now churning out a lot of patents, it is still way behind America and other rich countries when it comes to innovation quality.
Hydrogen fuel cells may have just taken a giant leap forward. Indiana University scientists just announced they’ve managed to create a highly efficient biomaterial that takes in protons and “spits out” hydrogen gas. Called “P22-Hyd,” this modified enzyme can be grown using a simple room temperature fermentation process — making it much more eco-friendly and considerably cheaper than the materials currently used in fuel cells, like platinum.
In a press release, lead author of the study Trevor Douglas noted, “This material is comparable to platinum, except it’s truly renewable. You don’t need to mine it; you can create it at room temperature on a massive scale using fermentation technology; it’s biodegradable. It’s a very green process to make a very high-end sustainable material.”
The way the enzyme is created is interesting in its own right. Researchers use two genes from E. coli bacteria inserted into the capsid, or viral protein shell, of a second virus. These genes then produce hydrogenase, the enzyme used to set off the hydrogen reaction.
This may sound a little complicated — and it is. Douglas admits that in the past, it’s been hard to harness hydrogenase for biofuel production due to its sensitivity to environmental conditions like warm temperatures. This new method creates enzymes that are much more stable, allowing it to be used more efficiently. Hopefully this discover will help drive down the cost of hydrogen cars — currently the vehicles retail for between $50,000 and $100,000.
THE WATERLOO RESEARCHERS HELPING POWER A GLOBAL REVOLUTION
There is no magic bullet, no single solution that will address the massive global energy inequities that leave billions of people with little or no access to electricity. Instead, change will come from connecting the ideas, innovations and experience of some of the world’s top minds.
Affordable Energy for Humanity (AE4H) focuses on four broad areas of research with the greatest opportunity to create meaningful, sustainable energy change.
RESEARCH AREA 1
Generation, Devices And Advanced Materials
Promise and potential: Next-generation batteries
Watch the Video
Next-generation batteries are an emerging market with unlimited potential — and Waterloo chemistry professor Linda Nazar is eager to see her team’s extraordinary labours pay off.
Nazar, who was recently named an Officer of the Order of Canada for her advancements in battery systems and clean-energy storage, is contributing to breakthroughs in the design of rechargeable batteries for grid storage, electric vehicles and other clean-energy technology.
“Our research team and others at the University of Waterloo are working on a lot of different battery technologies where we’re starting to see the hard efforts that we’ve put in over the last decade really paying off in terms of making batteries that have higher energy density, that are safer and also have longer cycle life,” says Nazar, who along with colleagues at the Waterloo Institute for Nanotechnology, Zhongwei Chen and Michel Pope, are planning to launch an Electrochemical Energy Research Centre at the University.
Their work could have huge ramifications for energy-poor developing countries.
“In impoverished countries where there’s an abundance of sunshine, it’s critical to be able to store renewable energy in affordable energy storage systems to allow for load leveling and also for storage at night or even off-season storage,” Nazar says.
“That allows communities that are limited in their electrical resources to have a cheap, abundant source of energy to power activity in the evening and when the sun isn’t shining.”
RESEARCH AREA 2
Information And Communication Technologies For Energy System Convergence
Reducing the carbon footprint, improving energy efficiency
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Energy poverty is one of the biggest challenges facing humanity, according to Waterloo computer science professor Srinivasan Keshav.
“More than one billion around the world don’t have access to good forms of energy,” Keshav says. “The only energy they have is their own human labour, so if they want to dig a trench they have to do it by hand. How much firewood they can carry determines what they’re going to cook. That’s really what it comes down to.”
Keshav and his research team are focusing on greener, more efficient sources of energy that will ultimately help address these inequities.
“The work I’m doing in this lab is focused on two things,” Keshav explains. “One is to reduce the carbon footprint. The other is to improve the energy efficiency of systems that generate, transmit and consume energy — everything from power plants to the solar panels on your roof.
“Solar efficiency is going up and the costs are coming down at the same rate as costs have gone down for electronics. The same thing is happening with lighting. The technology is now coming into place which allows us to put a panel on the roof, [add] storage and efficient lighting — and you have the ability to transform lives.
“At some level the changes come not just from technology but from policy, not from research but from imagination. We make it possible for somebody to imagine a different future — and that perhaps is the biggest thing we do.”
A smart grid for smarter energy
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Just as smartphone technology has come to dominate the way we communicate, the future of 21st-century electricity may well belong to the smart grid.
The smart grid is an intelligent infrastructure that uses information technology — sensors, communications, automation and computers — to improve the way electricity is delivered. It also allows for renewables such as wind and solar power to be part of the equation.
“A lot of people do not have access to the electrical grid the way we do,” says Catherine Rosenberg, a professor of engineering and Canada Research Chair in the Future Internet at Waterloo. “There are two types of technologies that can have a major impact on the smart grid. The first technology is renewables — solar, wind. The second is energy storage.”
Rosenberg, who is collaborating with computer science professor Srinivasan Keshav, says that having access to renewable energy — solar panels, for example — and some storage would allow communities without grid access or with poor grid access to be self-sufficient.
Just as importantly, access must be affordable, and Rosenberg is optimistic that storage will become cost-efficient in the near future.
“Because there are more and more needs for energy storage— for example for electric vehicles — the price of energy storage is going to decrease,” she says. “We are in the business of designing systems by integrating many technologies and showing how those systems should be operated in a cost-efficient manner.”
Environmental and Human Dimensions Of Energy Transitions
Energy and sustainability: Lessons from the North
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Energy poverty is not confined to the developing world. There are nearly 300 remote communities across northern Canada — about 170 of them First Nations — and most rely on diesel generators with fuel flown in or trucked in via ice road.
It’s not only environmentally damaging, it’s also incredibly expensive — up to $1 per kilowatt hour — so building capacity to get energy from renewable sources is the preferred option.
“In our First Nations communities, we see both huge need and huge opportunity,” says Paul Parker, a professor in the Faculty of Environment. “We are here to work with communities to achieve what they want. The first question is, ‘What future do you want?’ And then it’s, ‘How do we design, evaluate and implement it?’
“The University of Waterloo is probably most famous for its technical capacity, but we also realize that technical capacity needs to have social context. We need the social scientists to work with our engineers and technicians in the North. Our students are fantastic. We’ve trained economic developers for communities across the North where they look and they see an opportunity and they say, ‘Let’s take those solutions to as many communities as possible,’ ” Parker says.
“We already have the technology to make these things happen, so [it’s about] the implementation. And what we are learning in Canada has [global implications] in other parts of the world that experience energy poverty.”
As flaws in centralized power grids become apparent — their vulnerability to disruption and dependence on planet-warming fossil fuels — the time has come for renewable energy microgrids to take centre stage.
“Here at Waterloo we have a lot of expertise to provide in microgrids, not only to Canada but to the world, from simulation and modelling to hardware and social interactions withcommunities,” says Claudio Cañizares, a professor of electrical and computer engineering at Waterloo.
Scientists are trying to transform microgrids — which can operate independently or in conjunction with main power grids — into renewable energy-based systems by introducing solar and wind power. Challenges being addressed by research at Waterloo include making the systems economically feasible, and learning to manage the variability inherent to renewable energy sources like wind and solar. Cañizares and his fellow researchers are doing both theoretical work — simulation, modeling, optimization — and applied science so they can understand how the controls work in different environments.
“One of the main motivations for our work here is to try to improve or facilitate the introduction of these renewable sources and to move away from diesel in the remote, mostly indigenous, communities in Canada,” Cañizares says.
Ultimately, Cañizares believes the impact of affordable energy access will change lives.
His research partners in northern Chile, for example, are seeing young people who had left their communities return once affordable energy sources are introduced, and business opportunities cropping up that didn’t exist before.
“We have come a long way,” he says. “We believe Waterloo is particularly well-positioned … people are paying attention.”
Video: Matt Regehr and Light Imaging
Research and responsibility — what’s the right balance? And are we doing enough? Share your thoughts with us in our “Comments” section of our Blog.
Amarjeet Sohi (left), minister of infrastructure and communities, tours chemistry professor Jillian Buriak’s lab after announcing $75 million in federal funding to U of Alberta through the Canada First Research Excellence Fund.
Government of Canada investment establishes the Future Energy Systems ResearchInstitute.
The University of Alberta will launch a new institute aimed at reducing the environmental footprint of fossil fuels and developing new low-carbon energy systems, thanks to a $75-million federal grant.
The U of A’s Future Energy Systems Research Institute will bring together researchers across disciplines to improve energy systems related to unconventional hydrocarbon resources—tailings ponds, greenhouse emissions, water use, land reclamation, and safe, efficient energy transportation.
The institute will also build on U of A strengths in advanced materials, smart electrical grids and bioprocessing to help move Canada to a low-carbon energy economy.
The $75-million federal investment is part of the Canada First Excellence Research Fund to strategically invest in areas where post-secondary research institutions have a competitive advantage and can become global leaders.
“I thank the Government of Canada’s historic investment in the Canada First Excellence Research Fund. This funding marks a major step forward for Canada and our collective ability to provide global leadership in response to a diverse set of grand challenges,” said U of A President David Turpin.
Turpin said the Future Energy Systems Research Institute pushes Canadian energy and environment research “onto a new level.”
“We will build on our broad historic strengths in these areas and spearhead provincial, national and international research partnerships and projects that envision and deliver solutions to the world’s most urgent energy challenges—reducing the environmental footprint of today’s energy system and making the transition to a cleaner, safer and more abundant low-carbon energy future.”
Kirsty Duncan, Canada’s minister of science, unveiled the latest round of investments Sept. 6 at the University of Waterloo. In total, the Government of Canada invested $900 million in 13 Canadian research universities.
“The Canada First Research Excellence Fund will equip Canada to respond to some of the most pressing issues it will face in the future: brain health, sustainable food and water supplies, environmental concerns, future energy supplies. The research supported through this fund will make the country stronger,” Duncan said.
Low-cost solar on par with hydrocarbons
Jillian Buriak’s work toward low-cost solar cells is the kind of innovative energy research that will benefit from $75 million in new federal funding announced today.
U of A chemistry professor Jillian Buriak represents the type of research innovator who could apply for funding through the new institute. Buriak is developing low-cost solar cells, including a version that uses a spray-coating technology.
Buriak said some estimates predict energy use by humans will double by 2050 and triple by 2100. The sun is the largest source of power we can access, and the cost of solar power is now on par with hydrocarbons, making it an increasingly viable alternative, she said.
“A clean, low-carbon source of plentiful energy is needed to maintain the social and economic security of humanity. From climate change to escalating conflict over energy and resources, our future is at risk unless we transition to a low-carbon future,” said Buriak. “The Canada First Excellence Research Fund allows the University of Alberta to pioneer a made-in-Alberta solution to help solve the world’s energy challenges, helping us to transition to a low-carbon economy.”
The U of A will work collaboratively with the University of Calgary, which also received $75 million for its Global Research Initiative in Low Carbon Unconventional Resources. The U of C’s initiative aims to transform the extraction of unconventional energy resources such as the oil-sands to improve efficiency and reduce Canada’s carbon footprint.
The late Richard Smalley, often considered to be one of the fathers of nanotechnology following his Nobel Prize-winning work on fullerenes, had a keen interest in energy. In many presentations he would ask the audience to call out what they considered to be the most pressing issues facing humanity.
Watch Video: Dr. Wade Adams of The Smalley Institute and Rice University:
Nanotechnology and the Future of Energy
The answers were often similar to those identified in the World Economic Forum’s Global Risks Report, including persistent worries such as disease, clean water, poverty, inequality and access to resources. Smalley would then rearrange the list to put energy at the top and proceed to explain how a happy, healthy world of 9 billion could be achieved if we could only fix the problem of providing cheap and abundant clean energy.
Back in the early 2000s, most of the imagined solutions to the energy challenge involved novel materials such as carbon nanotubes for lossless electricity transmission, or hydrogen storage to enable fuel-cell vehicles. While novel materials like nanotubes never quite lived up to their promise, 15 years later many nanotechnologies, including the latest carbon-based material graphene, are now promising to deliver huge leaps in the way that we generate, store and use energy.
But these advances are not enabled by nanotechnologies in isolation. Many of the technologies identified in the Forum’s top 10 emerging technologies list for the past three years, from gene editing to additive manufacturing, also play a role, supporting our ability to understand the nanoscale processes in nature, generating new insights into how to move beyond conventional solar cells and copy some of nature’s tricks, such as photosynthesis.
The problem is that conventional silicon-based solar cells, while effective, have many drawbacks. They are brittle, which means that they need to be fixed to a rigid support, and they only harvest a small amount of the spectrum of light generated by the sun. For instance, silicon is transparent to infrared light, which means a lot of potential energy available is not harvested.
Researchers at the University of California, Riverside, are helping to solve this by working with hybrid material combining inorganic semiconductor nanoparticles with organic compounds. These first capture two infrared photons that would normally pass right through a solar cell without being converted to electricity, then add their energies together to make one higher energy photon.
An alternative approach is the use of quantum dots. These are nanoscale particles where the response to different wavelengths can be tuned by altering their sizes. Because of their unique optical properties, they are finding increasing uses in lighting and televisions, but these properties are also useful in solar cells. While the efficiency of quantum-dot solar cells reported in recent studies is increasing to as high as 9%, the real breakthrough is that the new devices can be produced at room temperature and in an atmosphere, rather than an expensive and hard-to-maintain vacuum. Perhaps the most exciting aspect of quantum-dot solar cells, though, is that the quantum dots can be dispersed in other materials, leading to “spray on” low-cost and large-area solar cells that can be applied to buildings or vehicles.
A leaf out of nature’s book
But the big prize in advanced photovoltaics will come with achieving artificial photosynthesis. The aim is to enable the production of useful chemicals and fuels directly from sunlight and carbon dioxide, just as plants do. By combining nanotechnology and biology, researchers are mimicking the processes that occur in the leaf of a plant to produce fuels such as butanol and biodegradable plastics. Once combined with synthetic biology to precisely engineer the bacteria, the possibilities are endless.
Generating energy is only half the solution, though. It also has to be stored for later use. This is an addressable issue for energy utilities, who balance peaks and troughs in demand by using techniques such as pumping water uphill into hydro-electric dams. But such large-scale engineering solutions are not an option for off-grid communities in much of the developing world. Local energy use requires a cheap and efficient way of storing energy, as do electric vehicles and smartphones.
Nanomaterials, and graphene in particular, have been attracting significant interest as potential game-changers for energy storage. One driver for this is the high surface area of many nanomaterials, which increases the ability to store charge within a given volume. Graphene – which is formed from layers of carbon a single atom thick – has a tremendous surface area for a given amount of material, and has created a lot of excitement about graphene-based supercapacitors and anodes for lithium ion batteries.
One of the biggest problems with the lithium ion batteries is the amount of charge that can be stored in the conventional graphite-based anodes they use. Lithium is added to the graphite when the battery is charging and removed as it discharges, but the low capacity of graphite means that the anode is limited in the amount of energy it can store. Researchers have been looking at silicon anodes that promise 10 times better capacity for the best part of decade, but the constant stresses on the material results in a short lifetime. One way of addressing this issue has been to place the silicon in cage of fullerenes, nanotubes or nanowires. Companies such as XG Sciences andCalifornia Lithium Battery are developing graphene-coated silicon, or “silicon-graphene nano-composite anode material”.
Taking a more bio-inspired approach, the Israeli company StoreDot is combining nanotechnology and biology to create nanoscale peptide crystals to produce a battery that will charge in less than a minute, while researchers in Singapore have recently developed a nanotube-based battery that could last more than 10 times as long as normal ion batteries and can also charge in minutes.
Watch Video: Rice University’s laser-induced graphene makes simple, powerful energy storage possible
In the meantime, while we wait for current nanotechnology research to bear fruit, the biggest contribution that nanotechnology can make today is simply to reduce the amount of energy required to perform common tasks, such as heating and cooling.
The UK company Xefro, for instance, is making use of graphene to create a smart home-heating system which promises savings of up to 70%. The heaters make use of the high surface area of what is effectively a two-dimensional material to create an efficient heating material which is then applied as an ink. The ink can be printed on a variety of materials and in just about any shape, including water heaters. In a two-dimensional material, energy isn’t wasted in heating up the heater, so the heat can be turned on and off quickly. This both reduces energy use and makes the system ideal for use with smart thermostats.
Meanwhile, another UK start-up called Inclusive Designs is addressing the problem of keeping things cool by combining nanomaterials and fractals with 3D printing. The company prints 3D fractal structures designed to absorb infrared (heat) and then removes the heat by making use of the high thermal conductivity of graphene, creating a cooling system with no liquids or moving parts.
Since Richard Smalley’s untimely death in 2005, the energy situation has improved, with an increasing number of countries now generating the majority of their power from renewable sources; electric vehicles are now a common sight. But cheap, efficient renewable-energy production – together with its storage and transmission – remains a challenge. The combination of nanotechnology, with a wide range of other emerging and transformative technologies, promises to make Smalley’s dream of a world of abundant, cheap, clean energy a reality over the coming decade.
Bruce W. Hoy ~ CEO of Genesis Nanotechnology, Inc.
Bruce has been the ‘catalyst force’ for GNT™ recognizing early-on the generational and transformative opportunity of Nanotechnology (The Fourth Industrial Revolution). Bruce has sought to position Genesis in the forefront of the coming “Nano-Sea-Change.” Focusing and applying 35+ years of experience in Business Start-Up and Venture Capital, Bruce has built ‘Nano-Bridge-Relationships’, working to forge Nanotechnologies Industry & Markets together with Commercial Opportunities that will solve the most essential ‘Grand Challenges’ for multi-generations.
Identification of a gene needed to expand light harvesting in photosynthesis into the far-red-light spectrum provides clues to the development of oxygen-producing photosynthesis, an evolutionary advance that changed the history of life on Earth. “Knowledge of how photosynthesis evolved could empower scientists to design better ways to use light energy for the benefit of mankind,” said Donald A. Bryant, the Ernest C. Pollard Professor of Biotechnology and professor of biochemistry and molecular biology at Penn State University and the leader of the research team that made the discovery.
This discovery, which could enable scientists to engineer crop plants that more efficiently harness the energy of the Sun, will be published online by the journal Science on Thursday July 7, 2016.
“Photosynthesis usually ranks about third after the origin of life and the invention of DNA in lists of the greatest inventions of evolution,” said Bryant. “Photosynthesis was such a powerful invention that it changed the Earth’s atmosphere by producing oxygen, allowing diverse and complex life forms—algae, plants, and animals—to evolve.”
The researchers identified the gene that converts chlorophyll a—the most abundant light-absorbing pigment used by plants and other organisms that harness energy through photosynthesis—into chlorophyll f—a type of chlorophyll that absorbs light in the far-red range of the light spectrum. There are several different types of chlorophyll, each tuned to absorb light in different wavelengths. Most organisms that get their energy from photosynthesis use light in the visible range, wavelengths of about 400 to 700 nanometers. Bryant’s lab previously had shown that chlorophyll f allows certain cyanobacteria—bacteria that use photosynthesis and that are sometimes called blue-green algae—to grow efficiently in light just outside of the usual human visual range—far-red light (700 to 800 nanometers). The ability to use light wavelengths other than those absorbed by plants, algae, and other cyanobacteria confers a powerful advantage to those organisms that produce chlorophyll f—they can survive and grow when the visible light they normally use is blocked.
“There is nearly as much energy in the far-red and near-infrared light that reaches the Earth from the Sun as there is in visible light,” said Bryant. “Therefore, the ability to extend light harvesting in plants into this range would allow the plants to more efficiently use the energy from the Sun and could increase plant productivity.”
The gene the researchers identified encodes an enzyme that is distantly related to one of the main components of the protein machinery used in oxygen-producing photosynthesis. The researchers showed that the conversion of chlorophyll a to chlorophyll f requires only this one enzyme in a simple system that could represent an early intermediate stage in the evolution of photosynthesis. Understanding the mechanism by which the enzyme functions could provide clues that enable scientists to design better ways to use light energy.
“There is intense interest in creating artificial photosynthesis as an alternative energy source,” said Bryant. “Understanding the evolutionary trajectory that nature used to create oxygen production in photosynthesis is one component that will help scientists design an efficient and effective system. The difficulty is that photosynthesis is an incredibly complex process with hundreds of components and, until now, there were few known intermediate stages in its evolution. The simple system that we describe in this paper provides a model that can be further manipulated experimentally for studying those early stages in the evolution of photosynthesis.”
By disabling the gene that encodes the enzyme in two cyanobacteria that normally produce chlorophyll f, the researchers demonstrated that the enzyme is required for the production of chlorophyll f. The experiment showed that, without this enzyme, these cyanobacteria could no longer synthesize chlorophyll f. By artificially adding the gene that encodes the enzyme, the researchers also showed that this one enzyme is all that is necessary to convert cyanobacteria that normally do not produce chlorophyll f into ones that can produce it.
Another clue that the newly identified enzyme could represent an early stage in the evolution of photosynthesis is that the enzyme requires light to catalyze its reaction and may not require oxygen, as scientists had previously suspected. “Because the enzyme that synthesizes chlorophyll f requires light but may not require oxygen for its activity, it is possible that it evolved before Photosystem II, the photosynthetic complex that produces oxygen and to which the enzyme is related. If the enzyme is an evolutionary predecessor of Photosystem II, then evolution borrowed an enzyme that was originally used for chlorophyll synthesis and used it to evolve an enzyme that could produce oxygen, which ultimately led to changes in Earth’s atmosphere,” said Bryant.
Small flakes of graphene could1 expand the usable spectral region of light in silicon solar cells to boost their efficiency, new research from KAUST shows1.
Solar cell materials have become significantly cheaper to produce in recent years, yet further cost savings are needed to make solar technologies commercially attractive. The prevalence of silicon in solar cells makes them a good target for efficiency enhancement.
“By improving the efficiency of silicon solar cells, we can provide a more cost-effective way for energy production,” said Jr-Hau He, KAUST associate professor of electrical engineering, who also led the research team.
Graphene quantum dots are small flakes of graphene that are useful because of their interaction with light. One of these interactions is optical downconversion, which is a process that transforms light of high energies into lower energy (for example, from the ultraviolet to the visible).
Downconversion can be used to boost solar cells. Silicon absorbs light very efficiently in the visible part of the spectrum, and therefore appears black. However, the absorption strength of silicon for ultraviolet light is much smaller, meaning that less of this light is absorbed, reducing the efficiency of solar cells in that part of the spectrum.
One way to circumvent this problem is the downconversion of ultraviolet light to energies where silicon is a more efficient absorber.
Graphene quantum dots are ideal candidates for this purpose. They are easy to manufacture using readily-available materials such as sugar and by then heating them with microwave radiation. While the dots are almost transparent to visible light, which is important to pass that light through to the solar cell, they are efficient in converting UV light to lower energies.
The researchers integrated the quantum dots on a silicon solar cell device. The efficiency of the solar cells increased in comparison to control samples. For a mature technology to show a clear improvement in efficiency is promising, because it can be produced using an easy manufacturing process.
The test sample solar cells measured so far have not yet been optimized to be closer to the record-breaking performances seen in silicon. The researchers therefore plan to combine some other enhancement technologies previously achieved in similar devices.
He noted. “We have been successfully utilized surface engineering treatments, including fabricating nanostructures and passivation layers, to improve the light harvesting and the electrical properties of solar cells. By integrating these techniques all together, we hope that in the next few years the world record can be broken at KAUST,” he said.
Tsai, M.-L., Tu, W.-C., Tang, L., Wei, T.-C., Wei, W.-R., Lau, S.P., Chen, L.-J. & He, J.-H. Efficiency enhancement of silicon heterojunction solar cells via photon management using graphene quantum dot as downconverters. Nano Letters 16, 309−313 (2016).| article
Wellbores drilled to extract oil and gas can be dramatically reinforced with a small amount of modified graphene nanoribbons added to a polymer and microwaved, according to Rice University researchers.
The Rice labs of chemist James Tour and civil and environmental engineer Rouzbeh Shahsavari combined the nanoribbons with an oil-based thermoset polymer intended to make wells more stable and cut production costs. When cured in place with low-power microwaves emanating from the drill assembly, the composite would plug the microscopic fractures that allow drilling fluid to seep through and destabilize the walls.
Results of their study appeared in the American Chemical Society journal ACS Applied Materials and Interfaces.
The researchers said that in the past, drillers have tried to plug fractures with mica, calcium carbonate, gilsonite and asphalt to little avail because the particles are too large and the method is not efficient enough to stabilize the wellbore.
In lab tests, a polymer-nanoribbon mixture was placed on a sandstone block, similar to the rock that is encountered in many wells. The team found that rapidly heating the graphene nanoribbons to more than 200 degrees Celsius with a 30-watt microwave was enough to cause crosslinking in the polymer that had infiltrated the sandstone, Tour said. The microwave energy needed is just a fraction of that typically used by a kitchen appliance, he said.
“This is a far more practical and cost-effective way to increase the stability of a well over a long period,” Tour said.
In the lab, the nanoribbons were functionalized—or modified—with polypropylene oxide to aid their dispersal in the polymer. Mechanical tests on composite-reinforced sandstone showed the process increased its average strength from 5.8 to 13.3 megapascals, a 130 percent boost in this measurement of internal pressure, Shahsavari said. Similarly, the toughness of the composite increased by a factor of six.
“That indicates the composite can absorb about six times more energy before failure,” he said. “Mechanical testing at smaller scales via nanoindentation exhibited even more local enhancement, mainly due to the strong interaction between nanoribbons and the polymer. This, combined with the filling effect of the nanoribbon-polymer into the pore spaces of the sandstone, led to the observed enhancements.”
The researchers suggested a low-power microwave attachment on the drill head would allow for in-well curing of the nanoribbon-polymer solution.
More information: Nam Dong Kim et al, Microwave Heating of Functionalized Graphene Nanoribbons in Thermoset Polymers for Wellbore Reinforcement, ACS Applied Materials & Interfaces (2016). DOI: 10.1021/acsami.6b01756
Genesis Nanotechnology, Inc. ~ “Great Things from Small Things”
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