GT/ Solvent study solves solar cell durability puzzle
Energy & green technology biweekly vol.34, 23d September — 12th October
TL;DR
- The manufacture of high-efficiency solar cells with layers of 2D and 3D perovskites may be simplified by solvents that allow solution deposition of one layer without destroying the other.
- Due to their very high efficiency in transporting electric charges from light, perovskites are known as the next generation material for solar panels and LED displays. A team have now invented a brand-new application of perovskites as optical fibers.
- Electricity-generating rooftop solar cells not only save on planet-warming carbon emissions, they also save a significant amount of water. Water consumption is tightly bound to energy use, because without water we cannot mine, drill, frack, or cool thermoelectric and nuclear plants. A given household may save on average 16,200 gallons of water per year by installing rooftop solar.
- A new study documents how a durable plastic can be perpetually broken down and remade, without sacrificing its desired physical properties.
- An underutilized natural resource could be just what the airline industry needs to curb carbon emissions. Researchers report success in using lignin as a path toward a drop-in 100% sustainable aviation fuel. Lignin makes up the rigid parts of the cell walls of plants. Other parts of plants are used for biofuels, but lignin has been largely overlooked because of the difficulties in breaking it down chemically and converting it into useful products.
- Even small objects, such as dust and leaves, can block sunlight from reaching solar cells, and understanding how the loss of incoming radiation affects power output is essential for optimizing photovoltaic technology. Researchers explore how different shade conditions impact performance of single solar cells and two-cell systems connected in series and parallel. They found that the decrease in output current of a single cell or two cells connected in parallel was nearly identical to the ratio of shade to sunlight. However, for two cells running in series, there was excess power loss.
- A team of scientists has developed a system that uses carbon dioxide, CO2, to produce biodegradable plastics, or bioplastics, that could replace the nondegradable plastics used today. The research addresses two challenges: the accumulation of nondegradable plastics and the remediation of greenhouse gas emissions.
- Researchers have taken a water treatment technology and adapted it for another environmentally important function — selectively separating rare earth elements and transition metals. This chemical process significantly reduces both the energy and product consumption involved with rare earth element recovery.
- The carrier concentration and conductivity in p-type monovalent copper semiconductors can be significantly enhanced by adding alkali metal impurities. Doping with isovalent and larger-sized alkali metal ions effectively increased the free charge carrier concentration, and the mechanism was unraveled by their theoretical calculations. Their carrier doping technology enables high carrier concentration and high mobility p-type thin films to be prepared from the solution process, with photovoltaic device applications.
- With electric vehicles sales soaring worldwide, potential buyers are not just weighing up the price tag, but also the logistics and expense of charging the planet-friendly cars. A new study shows households with solar panels and batteries will be the big winners.
- And more!
Green Technology Market
Green technology is an applicable combination of advanced tools and solutions to conserve natural resources and environment, minimize or mitigate negative impacts from human activities on the environment, and ensure sustainability development. Green technology is also referred to as clean technology or environmental technology which includes technologies, such as IoT, AI, analytics, blockchain, digital twin, security, and cloud, which collect, integrate, and analyze data from various real-time data sources, such as sensors, cameras, and Global Positioning System (GPS).
Green technology, also known as sustainable technology, protects the environment by using various forms of sustainable energy. Some of the best examples of green technologies include solar panels, LED lighting, wind energy, electric vehicles, vertical farming, and composting.
The global Green Technology and Sustainability market size to grow from USD 11.2 billion in 2020 to USD 36.6 billion by 2025, at a Compound Annual Growth Rate (CAGR) of 26.6% during the forecast period. The growing consumer and industrial interest for the use of clean energy resources to conserve environment and increasing use of Radio Frequency Identification sensors across industries are driving the adoption of green technology and sustainability solutions and services in the market.
The blockchain segment is estimated to grow at the highest CAGR: Energy-intensive cryptocurrency mining has caused a spike in carbon emission, and hence blockchain is capable of driving innovation in the field of green technology.
Latest Research
Deterministic fabrication of 3D/2D perovskite bilayer stacks for durable and efficient solar cells
by Siraj Sidhik, Yafei Wang, Michael De Siena, Reza Asadpour, Andrew J. Torma, et al in Science
Rice University engineers say they’ve solved a long-standing conundrum in making stable, efficient solar panels out of halide perovskites.
It took finding the right solvent design to apply a 2D top layer of desired composition and thickness without destroying the 3D bottom one (or vice versa). Such a cell would turn more sunlight into electricity than either layer on its own, with better stability. Chemical and biomolecular engineer Aditya Mohite and his lab at Rice’s George R. Brown School of Engineering reported their success at building thin 3D/2D solar cells that deliver a power conversion efficiency of 24.5%. That’s as efficient as most commercially available solar cells, Mohite said.
“This is really good for flexible, bifacial cells where light comes in from both sides and also for back-contacted cells,” he said. “The 2D perovskites absorb blue and visible photons, and the 3D side absorbs near-infrared.”
Perovskites are crystals with cubelike lattices known to be efficient light harvesters, but the materials tend to be stressed by light, humidity and heat. Mohite and many others have worked for years to make perovskite solar cells practical. The new advance, he said, largely removes the last major roadblock to commercial production.
“This is significant at multiple levels,” Mohite said. “One is that it’s fundamentally challenging to make a solution-processed bilayer when both layers are the same material. The problem is they both dissolve in the same solvents.
“When you put a 2D layer on top of a 3D layer, the solvent destroys the underlying layer,” he said. “But our new method resolves this.”
Mohite said 2D perovskite cells are stable, but less efficient at converting sunlight. 3D perovskites are more efficient but less stable. Combining them incorporates the best features of both.
“This leads to very high efficiencies because now, for the first time in the field, we are able to create layers with tremendous control,” he said. “It allows us to control the flow of charge and energy for not only solar cells but also optoelectronic devices and LEDs.”
The efficiency of test cells exposed to the lab equivalent of 100% sunlight for more than 2,000 hours “does not degrade by even 1%,” he said. Not counting a glass substrate, the cells were about 1 micron thick. Solution processing is widely used in industry and incorporates a range of techniques — spin coating, dip coating, blade coating, slot die coating and others — to deposit material on a surface in a liquid. When the liquid evaporates, the pure coating remains. The key is a balance between two properties of the solvent itself: its dielectric constant and Gutmann donor number. The dielectric constant is the ratio of the electric permeability of the material to its free space. That determines how well a solvent can dissolve an ionic compound. The donor number is a measure of the electron-donating capability of the solvent molecules.
“If you find the correlation between them, you’ll find there are about four solvents that allow you to dissolve perovskites and spin-coat them without destroying the 3D layer,” Mohite said.
He said their discovery should be compatible with roll-to-roll manufacturing that typically produces 30 meters of solar cell per minute.
“This breakthrough is leading, for the first time, to perovskite device heterostructures containing more than one active layer,” said co-author Jacky Even, a professor of physics at the National Institute of Science and Technology in Rennes, France. “The dream of engineering complex semiconductor architectures with perovskites is about to come true. Novel applications and the exploration of new physical phenomena will be the next steps.”
“This has implications not just for solar energy but also for green hydrogen, with cells that can produce energy and convert it to hydrogen,” Mohite said. “It could also enable non-grid solar for cars, drones, building-integrated photovoltaics or even agriculture.”
Hole-Doping to a Cu(I)-Based Semiconductor with an Isovalent Cation: Utilizing a Complex Defect as a Shallow Acceptor
by Kosuke Matsuzaki, Naoki Tsunoda, Yu Kumagai, Yalun Tang, Kenji Nomura, Fumiyasu Oba, Hideo Hosono in Journal of the American Chemical Society
Perovskite solar cells have been the subject of much research as the next generation of photovoltaic devices. However, many challenges remain to be overcome for the practical application. One of them concerns the hole transport layer (p-type semiconductor) in photovoltaic cells that carries holes generated by light to the electrode. In conventional p-type organic transport semiconductors, hole dopants are chemically reactive and degrade the photovoltaic device. Inorganic p-type semiconductors, which are chemically stable, are promising alternatives, but fabrication of conventional inorganic p-type semiconductors requires high temperature treatment. In this regard, the p-type inorganic semiconductors that can be fabricated at low temperatures and have excellent hole transport ability have been desired.
Inorganic p-type copper iodide (CuI) semiconductor is a leading candidate for such hole transport materials in photovoltaic device applications. In this material, native defects give rise to charge imbalance and free charge carriers. However, the overall number of defects is generally too low for satisfactory device performance.
Adding impurities with acceptor (positively charged) or donor (negatively charged) properties, known as “impurity doping,” is the gold standard method for bolstering the transport properties of semiconductors and the device performance. In conventional methods, ions with lower valency than the constituent atoms have been used as such impurities. However, in Cu(I)-based semiconductors, there is no ion with a valence lower than that of monovalent copper ions (zero valence), and thus a p-type doping in copper compounds has not been established. To propose a new carrier doping design for p-type doping in CuI, researchers from Japan and USA recently focused on the alkali impurity effect, which has been empirically used for hole doping in copper monovalent semiconductors, copper oxide (Cu2O) and Cu(In,Ga)Se2.
In a novel approach outlined in a study, the team, led by Dr. Kosuke Matsuzaki from Tokyo Institute of Technology (Tokyo Tech), Japan, demonstrated experimentally that p-type doping with alkali ion impurities, which has the same valence as copper but larger size, can improve conductivity in Cu(I)-based semiconductors. The theoretical analyses show that the complex defects, which are composed of alkali ion impurity and vacancies of copper ions, are an origion of hole generation (p-type conductivity).
While alkali metal impurities are known to increase the carrier concentration in copper oxide, the underlying mechanism remained a mystery to scientists, until now. This mechanism has now been elucidated, as Dr. Matsuzaki explains, “Using a combination of experimental studies and theoretical analysis, we managed to uncover the effect of the alkali impurities in Cu(I)-based semiconductors. The alkali metal Na impurity interacts with neighboring Cu ions in Cu2O to form defect complexes. The complexes, in turn, lead to be a source of holes.”
As an impurity is added to the crystal structure, electrostatic Coulomb repulsion between the impurity and neighboring Cu ions pushes the Cu atoms from their positions in the structure and leads to the formation of multiple acceptor-type copper vacancies. This, in turn, increases the total p-type carrier concentration and, consequently, p-type conductivity.
“Our simulations show that it is critical that the impurity is somewhat larger for vacant spaces in the crystal lattice to invoke electrostatic repulsion. For alkali impurities smaller, for example lithium, the impurity ions fall into the interstitial sites and do not sufficiently deform the crystal lattice,” elaborates Dr. Matsuzaki.
Based on the p-type doping mechanism to form acceptor-type Cu vacancy defect complex, the team investigated larger alkaline ions, such as potassium, rubidium, and cesium (Cs), as acceptor impurities in ?-CuI. Among them, the Cs ions could bind even more Cu vacancies, leading to even greater concentration of stable charge carriers (1013–1019 cm-3) both in single crystals and thin-films prepared from the solution. “This suggests that the method can be used to fine-tune carrier concentrations under low-temperature processing for specific applications and devices. This would allow a whole new range of applications for these p-type materials,” concludes Matsuzaki.
Indeed, the development could be a major leap forward for copper(I)-based semiconductors, and could soon lead to their practical applications in solar cells and optoelectronic devices.
Single-crystal organometallic perovskite optical fibers
by Yongfeng Zhou, Michael A. Parkes, Jinshuai Zhang, Yufei Wang, Michael Ruddlesden, Helen H. Fielding, Lei Su in Science Advances
Due to their very high efficiency in transporting electric charges from light, perovskites are known as the next generation material for solar panels and LED displays. A team led by Dr Lei Su at Queen Mary University of London now have invented a brand-new application of perovskites as optical fibres.
Optical fibres are tiny wires as thin as a human hair, in which light travels at a superfast speed — 100 times faster than electrons in cables. These tiny optical fibres transmit the majority of our internet data. At present, most optical fibres are made of glass. The perovskite optical fibre made by Dr Su’s team consists of just one piece of a perovskite crystal. The optical fibres have a core width as low as 50 μm (the width of a human hair) and are very flexible — they can be bent to a radius of 3.5mm
Compared to their polycrystal counterparts, single-crystal organometallic perovskites are more stable, more efficient, more durable and have fewer defects. Scientists have therefore been seeking to make single-crystal perovskite optical fibres that can bring this high efficiency to fibre optics.
Dr Su, Reader in Photonics at Queen Mary University of London, said: ‘Single-crystal perovskite fibres could be integrated into current fibre-optical networks, to substitute key components in this system — for example in more efficient lasing and energy conversions, improving the speed and quality of our broadband networks.’
Dr Su’s team were able to grow and precisely control the length and diameter of single-crystal organometallic perovskite fibres in liquid solution (which is very cheap to run) by using a new temperature growth method. They gradually changed the heating position, line contact and temperature during the process to ensure continuous growth in the length while preventing random growth in the width. With their method, the length of the fibre can be controlled, and the cross section of the perovskite fibre core can be varied.
In line with their predictions, due to the single-crystal quality, their fibres proved to have good stability over several months, and a small transmission loss — lower than 0.7dB/cm sufficient for making optical devices. They have great flexibility (can be bent to a radius as small as 3.5mm), and larger photocurrent values than those of a polycrystalline counterpart (the polycrystalline MAPbBr3 milliwire photodetector with similar length).
Dr Su said, ‘This technology could also be used in medical imaging as high-resolution detectors. The small diameter of the fibre can be used to capture a much smaller pixel compared to the state of the art. So that means by using our fibre so we can have the pixel in micrometer scales, giving a much, much higher resolution image for doctors to make better and more accurate diagnosis. We could also use these fibres in textiles that absorb the light. Then when we’re wearing for example clothes or a device with these kinds of fibre woven into the textile, they could convert the solar energy into the electrical power. So we could have solar powered clothing.’
The water consumption reductions from home solar installation in the United States
by Avner Vengosh, Erika Weinthal in Science of The Total Environment
Electricity-generating rooftop solar cells not only save on planet-warming carbon emissions, they also save a significant amount of water, say a pair of Duke University researchers who have done the math.
A given household may save an average 16,200 gallons of water per year by installing rooftop solar, they found. In some states, like California, this saving can increase to 53,000 gallons, which is equivalent to 60 percent of the average household water use in the U.S. You won’t see the savings on your home water bill, but they’re still important. That’s because energy use is tightly bound to water consumption. Electrical energy production in the U.S. consumes nearly as much water as the agricultural sector. But that figure doesn’t include the additional water used produce fossil fuels in the first place, nor to manage coal ash waste.
“To generate electricity for the grid we need to mine and burn coal, frack and pump natural gas, and cool nuclear plants, all involving high volumes of water that is continuously lost,” said Avner Vengosh, a Duke University distinguished professor of environmental quality in the Nicholas School of the Environment and co-author of a new paper.
“However, with the solar cell, it’s a one-time consumption of much a lower volume of water for manufacturing,” Vengosh said. “And then, once it’s installed, there’s no longer any water use coming from that for the next 25 years of expected use.”
Currently, more than 70 percent of the world’s solar panels are being made in China, so the water consumption to generate solar energy occurs overseas. Co-author Erika Weinthal, a professor of environmental policy in the Nicholas School, said that to understand the broader water impacts from solar panel production, it is vital to look at the entire supply chain across the world.
“From a contamination point of view, solar cells have huge potential for environmental damage,” Vengosh said. “It contains heavy metals, some of which are very toxic, and therefore they could have impact on the immediate environment where the manufacturing occurs.” But after that, the water consumption of solar is zero.
Previous studies have attempted to evaluate the amount of water use for different stages of energy production, typically expressed as the volume of water to given energy such as liter or gallon per gigajoule. In the new study, the authors combined energy sources that are used to generate electricity for the residential sector across the contiguous U.S. and translated that to the volume of water consumption in each state. After evaluating the statewide water use for the residential sector, the new study calculated the virtual water use of individual homes in 48 states. These calculations estimate that the total amount of water consumed for powering the residential sector across the U.S. is 2.6 trillion gallons.
Converting to solar in homes reduces the use of the grid electricity and therefore also the volume of water. In some states, like in the southwestern U.S., the individual household water saving can reach up to 1000 percent upon installing rooftop solar. These water use calculations are a follow-up to a recent book Vengosh and Weinthal published earlier this year on intersection of energy and water quality that provides a detailed baseline for the water consumption of various fossil fuel sources. During the pandemic shutdown, the authors had decided to add solar panels to the home they share. While in the beginning the major motivation was to save carbon emission, after a while they realized it can save also water.
“So this article is really a product of wanting to decarbonize our own personal life,” Weinthal said. “I teach global environmental politics, and I teach about the Paris agreement, and I always try to get the students to connect what’s happening at the interstate level to what we can do with our own forms of agency.”
Today, photovoltaic solar cells account for about 1.5 percent of the nation’s electrical supply. That represents a saving of 99 billion gallons of water a year, the authors estimate, which is equivalent to about four days of California’s total water usage. But as the solar percentage grows, so too will the savings. Their paper also compares water consumption for energy by state, since each state uses different energy sources for electricity generation and has different use patterns and number of homes. The New England states, for example, show huge wins for converting to solar because they don’t use much electricity for air conditioning and they tend to heat their homes with oil, not electricity, Vengosh said. Arizona and California, states which have water shortages and a lot of sunny days, would also be big winners.
The researchers have already turned their attention to the water use and environmental effects of lithium mining, a metal that is key to next-generation batteries.
Continuous hydrodeoxygenation of lignin to jet-range aromatic hydrocarbons
by Michael L. Stone, Matthew S. Webber, William P. Mounfield, David C. Bell, Earl Christensen, Ana R.C. Morais, Yanding Li, Eric M. Anderson, Joshua S. Heyne, Gregg T. Beckham, Yuriy Román-Leshkov in Joule
An underutilized natural resource could be just what the airline industry needs to curb carbon emissions.
Researchers at three institutions — the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL), the Massachusetts Institute of Technology (MIT), and Washington State University — report success in using lignin as a path toward a drop-in 100% sustainable aviation fuel. Lignin makes up the rigid parts of the cell walls of plants. Other parts of plants are used for biofuels, but lignin has been largely overlooked because of the difficulties in breaking it down chemically and converting it into useful products. The newly published research demonstrated a process the researchers developed to remove the oxygen from lignin, such that the resulting hydrocarbons could be used as a jet fuel blendstock. Gregg Beckham, Ana Morais, and Earl Christensen are the researchers involved from NREL.
The paper points to the need to use sustainable sources for jet fuel as the airline industry has pledged to dramatically reduce carbon emissions. Airlines consumed 106 billion gallons of jet fuel globally during 2019, and that number is expected to more than double by 2050. Accomplishing the industry’s goal of achieving net carbon neutrality during that same period will require a massive deployment of sustainable aviation fuel (SAF) with high blend limits with conventional fuel.
Jet fuel is a blended mixture of different hydrocarbon molecules, including aromatics and cycloalkanes. Current commercialized technologies do not produce those components to qualify for a 100% SAF. Instead, SAF blendstocks are combined with conventional hydrocarbon fuels. As the largest source of renewable aromatics in nature, lignin could hold the answer to achieving a complete bio-based jet fuel. This newly published work illustrates the ability of a lignin pathway to complement existing and other developing pathways. Specifically, the lignin pathway described in this new work allows the SAF to have fuel system compatibility at higher blend ratios.
Because of its recalcitrance, lignin is typically burned for heat and power or used only in low-value applications. Previous research has yielded lignin oils with high oxygen contents ranging from 27% to 34%, but to be used as a jet fuel that amount must be reduced to less than a half-percent.
Other processes have been tried to reduce the oxygen content, but the catalysts involved require expensive noble metals and proved to be low yielding. Researchers at the trio of institutions demonstrated an efficient method that used earth-abundant molybdenum carbide as the catalyst in a continuous process, achieving an oxygen content of about 1%.
Experimental study on the power losses of a single photovoltaic cell and two series and parallel connected cells with partial shadows
by Xiaoxue Guo, Jiapu Zou, Zihua Wu, Yuanyuan Wang, Huaqing Xie in Journal of Renewable and Sustainable Energy
Large obstacles, like clouds and buildings, can block sunlight from reaching solar cells, but smaller sources, such as dust and leaves, can also create similar problems. Understanding how the loss of incoming radiation affects power output is essential for optimizing photovoltaic technology, which converts light into electricity and is an important contributor to the green energy transition.
Researchers from Shanghai Polytechnic University, Shanghai Engineering Research Center of Advanced Thermal Functional Materials, and Shanghai Solar Energy Research Center Co. Ltd explored how different shade conditions impact performance of single solar cells and two-cell systems connected in series and parallel.
“In the real world, photovoltaic cells are sometimes shaded by obstacles, which significantly alters the amount of incoming light,” said author Huaqing Xie, of Shanghai Polytechnic University and Shanghai Engineering Research Center of Advanced Thermal Functional Materials. “The degradation effects make power optimization difficult and result in significant power loss.”
Photovoltaics connected in series create a single path with the electrons flowing from one cell into the next. In contrast, cells in parallel provide two lanes for electrons to travel through, then recombine later. In practical applications, networks of solar cells are connected in series and parallel to expand the output current and power capability. The team found that the decrease in output current of a single cell or two cells connected in parallel was nearly identical to the ratio of shade to sunlight. However, for two cells running in series, there was excess power loss and a rise in temperature, which can cause further output degradation. For example, with 29.6% of the series photovoltaic module in the shade, the current decreased by 57.6%.
“Our study indicates that many factors, including shadow area, shadows on different cells of the module, and the connection of cells and modules, may affect the performance,” said Xie.
Previous studies have explored the consequences of shade on large photovoltaic modules but have largely ignored single cells and simple systems.
“In these complicated systems, shadows on one single cell may play vital role on the system output and reliability,” said Xie. “Therefore, studying single cells or a simple arrangement of two connected cells is necessary for solar panel development.”
In the future, the authors hope to examine the microscopic interaction behaviors and mechanisms in photovoltaic cells subjected to different shadows.
Solvent-driven fractional crystallization for atom-efficient separation of metal salts from permanent magnet leachates
by Caleb Stetson, Denis Prodius, Hyeonseok Lee, Christopher Orme, Byron White, Harry Rollins, Daniel Ginosar, Ikenna C. Nlebedim, Aaron D. Wilson in Nature Communications
It’s not uncommon in the scientific world for a process to have many unique applications. For example, Idaho National Laboratory researchers have taken a water treatment technology and adapted it for another environmentally important function — selectively separating rare earth elements and transition metals. This chemical process, recently described in article, significantly reduces both the energy and product consumption involved with rare earth element recovery.
Rare earth metals are a collection of chemically similar metallic elements that tend to occur at low concentrations in nature and can be difficult to separate from one another. They are valuable for their use in electric car motors, computer hard drives, solar panels and wind turbines. Transition metals are a class of metals that are excellent conductors of heat and electricity, often with high melting points and unique structural properties, making them essential for producing common alloys like steel and copper, as well as lithium-ion battery cathodes.
Currently, most of the components carrying these metals are simply disposed of. INL’s new method to extract these valuable metals involves dimethyl ether, a gaseous compound that served as one of the first commercial refrigerants. It drives fractional crystallization — a process that divides chemical substances based on their solubility — to separate rare earth elements and transition metals from magnet wastes.
“This process begins with a magnet that’s no longer useful, which is cut and ground into shavings,” said Caleb Stetson, the experimental lead for the project. “The magnet shavings are then put it into a solution with lixiviants, a liquid used to selectively extract metals from the material. Once the desired metals are leached from the material into the liquid, we can then apply a treatment process.”
The dimethyl ether-driven process uses far less energy and pressure than traditional methods, typically conducted at hundreds of degrees Celsius. Fractional crystallization can be carried out at ambient temperatures and requires only slightly elevated pressures of around five atmospheres. In comparison, the pressure in an unopened 12-ounce can of soda is 3.5 atmospheres. The lower energy and pressure needs also save money. Competing technologies also use added chemical “reagents” to drive precipitation and other separations, which inevitably become additional waste products with financial and environmental consequences. This is not the case with dimethyl ether-based fractional crystallization. Aaron Wilson, the project’s principal investigator, selected dimethyl ether for its ease of recovery, overcoming a shortcoming of prior attempts to use solvents to drive critical material separations. By dropping the pressure then recompressing the gas at the end of the experiment, the team can recover the solvent and reuse it in future cycles.
The process has other advantages as well. “It can be difficult to adjust temperatures for evaporative crystallization, but this fractional crystallization process eliminates all those challenges,” Stetson said. “For the process to separate distinct fractions from a metal-bearing solution, we only need to adjust the temperature by 10 degrees.”
When developing this solvent-based process for zero-waste metal recovery, the team worked closely with some of the electrochemical rare earth metal recovery processes already in place at INL. This includes the E-RECOV effort, which uses an electrochemical cell to efficiently recover metals from discarded electronics. Such work is funded by the Department of Energy’s Critical Materials Institute. Reducing the energy intensity and waste profile of critical material recovery also has significant environmental justice implications. In the past decades, primary extraction, like mining and enhancing the economic value of the product through strategic ore extraction, mining and beneficiation) has been shifted to underdeveloped nations like Congo, while energy-intensive downstream processing has been offshored to Asia. Much of this offshoring has been driven by public aversion to “dirty” mineral extraction processes taking place in their backyard. Creating a cleaner method will facilitate critical materials recovery domestically and abroad without exposing underserved communities to hazardous conditions.
Additionally, Wilson and his research team are working to address wastes associated with synthetic gypsum production via a project for the National Alliance for Water Innovation. Synthetic gypsum, the source of nearly 30% of dry wall in the U.S., is produced when scrubbing sulfur oxides from flue gas to prevent acid rain. Their team is isolating the wastes from the manufacturing process using dimethyl ether. This treatment has the potential to create even more products from what was originally merely an environmental problem.
Chem-Bio interface design for rapid conversion of CO2 to bioplastics in an integrated system
by Peng Zhang, Kainan Chen, Bing Xu, Jinghao Li, Cheng Hu, Joshua S. Yuan, Susie Y. Dai in Chem
A team of Texas A&M AgriLife Research scientists has developed a system that uses carbon dioxide, CO2, to produce biodegradable plastics, or bioplastics, that could replace the nondegradable plastics used today. The research addresses two challenges: the accumulation of nondegradable plastics and the remediation of greenhouse gas emissions.
The research was a collaboration of Susie Dai, Ph.D., associate professor in the Texas A&M Department of Plant Pathology and Microbiology, and Joshua Yuan, Ph.D., formerly with the Texas A&M Department of Plant Pathology and Microbiology as chair for synthetic biology and renewable products and now Lopata professor and chair in the Washington University in St. Louis Department of Energy, Environmental and Chemical Engineering. The research was made possible by the John ’90 and Sally ’92 Hood Fund for Sustainability and Renewable Products, Texas A&M AgriLife and Texas A&M University.
Dai said today’s petroleum-based plastics do not degrade easily and create a massive issue in the ecosystems and, ultimately, oceans. To address these issues, the Texas A&M College of Agriculture and Life Sciences researchers and their teams worked for almost two years to develop an integrated system that uses CO2 as a feedstock for bacteria to grow in a nutrient solution and produce bioplastics. Peng Zhang, Ph.D., postdoctoral research associate, and Kainan Chen, doctoral student, both in the Texas A&M Department of Plant Pathology and Microbiology, contributed to the work. The Texas A&M University System has filed a patent application for the integrated system.
“Carbon dioxide has been used in concert with bacteria to produce many chemicals, including bioplastics, but this design produces a highly efficient, smooth flow through our carbon dioxide-to-bioplastics pipeline,” Dai said.
“In theory, it is kind of like a train with units connected to each other,” Dai said. “The first unit uses electricity to convert the carbon dioxide to ethanol and other two-carbon molecules — a process called electrocatalysis. In the second unit, the bacteria consume the ethanol and carbon molecules to become a machine to produce bioplastics, which are different from petroleum-based plastic polymers that are harder to degrade.”
Using CO2 in the process could also help reduce greenhouse gas emissions. Many manufacturing processes emit CO2 as a waste product.
“If we can capture the waste carbon dioxide, we reduce greenhouse gas emission and can use it as a feedstock to produce something,” Dai said. “This new platform has great potential to address sustainability challenges and transform the future design of carbon dioxide reduction.”
The major strength of the new platform is a much faster reaction rate than photosynthesis and higher energy efficiency.
“We are expanding the capacity of this platform to broad product areas such as fuels, commodity chemicals and diverse materials,” Dai said. “The study demonstrated the blueprint for ‘decarbonized biomanufacturing’ that could transform our manufacturing sector.”
Dai said currently, bioplastics are more expensive than petroleum-based plastics. But if the technology is successful enough to produce bioplastics at an economic scale, industries could replace traditional plastic products with ones that have fewer negative environmental impacts. In addition, mitigating CO2 emissions from energy sectors such as gas and electric facilities would also be a benefit.
“This innovation opens the door for new products if the bacterium is engineered to consume carbon dioxide-derived molecules and produce target products,” Dai said. “One of the advantages of this design is the condition the bacteria grow in is mild and adaptable to industry-scale conditions.”
Techno-economic modelling for energy cost optimisation of households with electric vehicles and renewable sources under export limits
by Yan Wu, Syed Mahfuzul Aziz, Mohammed H. Haque in Renewable Energy
A new study by University of South Australia (UniSA) researchers shows that households with solar panels and batteries have a huge advantage when it comes to saving money on electric vehicles (EV).
With EV sales soaring worldwide, potential buyers are not just weighing up the price tag, but also the logistics and expense of charging the planet-friendly cars. UniSA engineers have calculated that EV owners can reduce annual electricity costs by almost 40 per cent if households are not totally reliant on the grid and they charge at home during off-peak periods.
In a new paper, Professor Mahfuz Aziz and colleagues address EV owners’ concerns about charging costs, one of the main obstacles in opting for an environmentally-friendly vehicle.
“Electric vehicles will become an important component of household energy consumption globally under plans to replace petrol-fuelled cars within the next decade,” Prof Aziz says.
“For motorists with private car spaces, home charging is the most convenient option, but for those still totally reliant on the electricity grid for their energy, the costs could mount significantly.”
Record-low prices for rooftop photovoltaic (PV) systems and declining battery costs are encouraging households to ‘go green,’ but consumers need to factor in multiple variables, researchers say. Using data from South Australia, where over 40 per cent of homes have rooftop solar panels, the researchers compared several household scenarios, considering EV charging demand, PV solar panel installation cost, battery degradation and export power limits. Based on typical household energy consumption (17 kW/day in SA) and motorists’ average daily travel distance (36.7km in AU), researchers analysed annual energy costs for households with petrol-based cars and those with EVs. They also analysed energy consumption during peak periods, between 5pm-9pm.
“In a basic case, all energy is imported from the grid where there are no solar panels, batteries or electric vehicles,” Prof Aziz says. “When solar panels are added, about 20 per cent less energy is imported and with batteries this is reduced by around 83 per cent. When electric vehicles are added, consumed energy rises significantly but imported energy can be reduced by around 89 per cent of total consumption.
“Our results demonstrate that households with petrol-based cars can reduce their annual energy costs by 6.71 per cent using solar panels, and by 10.38 per cent with the addition of a battery system. Replacing petrol-based cars with electric vehicles can reduce annual energy costs by 24 per cent and 32 per cent respectively. The most significant reduction (39.6 per cent) can be achieved with off-peak charging.”
The research team includes PhD student Ms Yan Wu and co-supervisor Dr Mohammed Haque. The team is currently investigating cost effective EV charging strategies for larger groups such as residential communities and university campuses while minimising impact on the power grid and distribution feeders. The popularity of electric vehicles is rapidly increasing across the globe, according to drive.com and it’s estimated that by 2030 there will be 145 million EVs on the road — compared to 11 million today. Despite the pandemic, electric vehicle sales increased globally by 43 per cent in 2020, although only made up 0.7 per cent of all car sales in Australia. By 2030, however, at least 50 per cent of all new cars sales in NSW are expected to be electric and other states are anticipated to follow this trend.
Recyclable and malleable thermosets enabled by activating dormant dynamic linkages
by Zepeng Lei, Hongxuan Chen, Chaoqian Luo, Yicheng Rong, Yiming Hu, Yinghua Jin, Rong Long, Kai Yu, Wei Zhang in Nature Chemistry
One day in the not-too-distant future, the plastics in our satellites, cars and electronics may all be living their second, 25th or 250th lives.
New research from the University of Colorado Boulder details how a class of durable plastics widely used in the aerospace and microelectronics industries can be chemically broken down into their most basic building blocks and then formed once again into the same material. It’s a major step in the development of repairable and fully recyclable network polymers, a particularly challenging material to recycle, as it is designed to hold its shape and integrity in extreme heat and other harsh conditions. The study documents how this type of plastic can be perpetually broken down and remade, without sacrificing its desired physical properties.
“We are thinking outside the box, about different ways of breaking chemical bonds,” said Wei Zhang, lead author of the study and chair of the chemistry department. “Our chemical methods can help create new technologies and new materials, as well as be utilized to help solve the existing plastic materials crisis.”
Their results also suggest that revisiting the chemical structures of other plastic materials could lead to similar discoveries of how to fully break down and rebuild their chemical bonds, enabling the circular production of more plastic materials in our daily lives.
In the mid-20th century, plastics were ubiquitously adopted in almost every industry and part of life as they are extremely convenient, functional and cheap. But half a century later, after exponential demand and production, plastics pose a major problem to the health of the planet and to people. The production of plastics requires large amounts of oil and the burning of fossil fuels. Disposable plastics create hundreds of millions of tons of waste every year, which ends up in landfills, oceans and even in our bodies, in the form of microplastics. Recycling, therefore, is key to reducing plastic pollution and fossil fuel emissions this century.
Conventional recycling methods mechanically break down polymers into powders, burn them or use bacterial enzymes to dissolve them. The goal is to end up with smaller pieces that can be used for something else. Think shoes made from recycled rubber tires or clothing made from recycled plastic water bottles. It’s not the same material anymore, but it doesn’t end up in a landfill or the ocean. But what if you could rebuild a new item from the same material? What if recycling didn’t just offer a second life to plastics, but a repeat experience? That’s exactly what Zhang and his colleagues have accomplished: They reversed a chemical method and discovered they can both break and form new chemical bonds in a particularly high-performance polymer.
“This chemistry can also be dynamic, can be reversible, and that bond can be reformed,” said Zhang. “We are thinking about a different way to form the same backbone, just from different starting points.”
They do this by breaking the polymer — “poly” meaning “many” — back into singular monomers, its molecules, a concept of reversible or dynamic chemistry. What’s especially novel about this latest method is that it has not only created a new class of polymer material that, like Legos, are easy to build, break apart and rebuild over and over, but the method can be applied to existing, especially hard-to-recycle polymers. These new chemical methods are also ready for commercialization and can plug and play with current industrial production.
“It can really benefit future design and development of plastics to not only create new polymers, but it’s also very important to know how to convert, upcycle and recycle older polymers,” said Zhang. “By using our new approach, we can prepare many new materials — some of which could have similar properties to the plastics in our daily life.”
This advance in the closed-loop recycling of plastics is inspired by the natural world, as plants, animals and human beings alike are currently part of a planetary-level, circular system of recycling, said Zhang. “Why can’t we make our materials the same way?”
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