A Los Alamos National Laboratory’s key energy security mission is developing safe and sustainable fuels for nuclear energy.

For now uranium dioxide, a radioactive actinide oxide, is the most widely used nuclear fuel in today’s nuclear power plants. But a new “combustion synthesis” process recently established for lanthanide metals – non-radioactive elements that are positioned one row above actinides on the periodic table – could be a guide for the production of safe, sustainable nuclear fuels in the actinide level.

Combustion synthesis of LnBTA compound. Image Credit: Los Alamos National Laboratory. Click image for the animation and largest view.

Bi Nguyen, Los Alamos National Laboratory Agnew postdoc and lead author of research recently published in the journal Inorganic Chemistry, which was selected as an American Chemical Society Editors’ Choice Featured Article said, “Actinide nitride fuels are potentially a safer and more economical option in current power-generating systems. Nitride fuels are also well suited to future Generation IV nuclear power systems, which focus on safety, and feature a sustainable closed reactor fuel cycle. Actinide nitrides have superior thermal conductivity compared to the oxides and are significantly more energy dense.”

Nitrides are a class of chemical compounds that contain nitrogen, versus oxides, which contain oxygen.

Actinide nitride fuels would provide more safety and sustainability because of their energy density, offering up more energy from less material, as well as better thermal conductivity – allowing for lower temperature operations, giving them a larger margin to meltdown under abnormal conditions.

The catch has been actinide nitrides are very challenging to make and the production of large amounts of high purity actinide nitrides continues to be a major impediment to their application. Both actinides and lanthanides are at the bottom of the periodic table and potential methods to make actinide materials are typically first tested with the lanthanides because they behave similarly, but are not radioactive.

The breakthrough is Los Alamos National Laboratory and Naval Research Laboratory scientists discovered that LnBTA [lanthanide bis(tetrazolato)amine] compounds can be burned to produce high-purity lanthanide nitride foams in a unique technique called combustion synthesis. This method uses a laser pulse to initiate dehydrated LnBTA complexes, which then undergo a self-sustained combustion reaction in an inert atmosphere to yield nanostructured lanthanide nitride foams.

LnBTA compounds are easily prepared in bulk and their combustion is readily scalable. There is an ongoing collaboration between the Laboratory’s Weapons Modernization and Chemistry divisions to examine actinide analogues for combustion synthesis of actinide nitride fuels.

The work was funded by the Laboratory Directed Research and Development (LDRD) program.

This work might just be what’s needed to crack the nuclear fission roadblock that has stalled America’s nuclear program. Its a near certainty that regulatory and political barriers are still going to be in the way, but the arguments coming from those will be significantly minimized. There is a large base of nuclear power potential in plants shut down and scheduled to shut down with immense potential to offer consumers from cell phones to electric vehicles a far less costly way to energize a modern economy.

Incheon National University scientists have announced a novel transparent solar cell design using thin silicon films, with efficient power generation.

Transparent Photovoltaics Sample. Image Credit: Incheon National University. Click image for the largest view.

Solar power has shown immense potential as a futuristic, ‘clean’ source of energy. Its not a wonder environmentalists worldwide have been looking for ways to advance the current solar cell technology. Now, scientists have put forth an innovative design for the development of a high-power transparent solar cell. This innovation brings us closer to realizing our goal of a sustainable green future with off-the-grid living.

Today, political pressure demands a shift from conventionally used fossil fuels to efficient sources of green energy. This has led to researchers looking into the concept of “personalized energy,” which would make on-site energy generation possible. For example, solar cells could possibly be integrated into windows, vehicles, cellphone screens, and other everyday products. But for this, it is important for the solar panels to be handy and transparent. To this end, scientists have recently developed “transparent photovoltaic” (TPV) devices – transparent versions of the traditional solar cell. Unlike the conventionally dark, opaque solar cells (which absorb visible light), TPVs make use of the “invisible” light that falls in the ultraviolet (UV) range.

Conventional solar cells can be either “wet type” (solution based) or “dry type” (made up of metal-oxide semiconductors). Of these, dry-type solar cells have a slight edge over the wet-type ones: they are more reliable, eco-friendly, and cost-effective. Moreover, metal-oxides are well-suited to make use of the UV light. Despite all this, however, the potential of metal-oxide TPVs has not been fully explored until now.

To this end, researchers from Incheon National University, Republic of Korea, came up with an innovative design for a metal-oxide-based TPV device. They inserted an ultra-thin layer of silicon (Si) between two transparent metal-oxide semiconductors with the goal of developing an efficient TPV device.

Their findings have been published in Nano Energy, in the December 2020 issue.

Prof Joondong Kim, who led the study, explains, “Our aim was to devise a high-power-producing transparent solar cell, by embedding an ultra-thin film of amorphous Si between zinc oxide and nickel oxide.”

The novel design consisting of the Si film had three major advantages. First, it allowed for the utilization of longer-wavelength light (as opposed to bare TPVs). Second, it resulted in efficient photon collection. Third, it allowed for the faster transport of charged particles to the electrodes. Moreover, the design can potentially generate electricity even under low-light situations (for instance, on cloudy or rainy days). The scientists further confirmed the power-generating ability of the device by using it to operate the DC motor of a fan. Based on these findings, the research team is optimistic that the real-life applicability of this new TPV design will soon be possible.

As for potential applications, there are plenty, as Prof Kim explained, “We hope to extend the use of our TPV design to all kinds of material, right from glass buildings to mobile devices like electric cars, smartphones, and sensors.” Not just this, the team is excited to take their design to the next level, by using innovative materials such as 2D semiconductors, nanocrystals of metal-oxides, and sulfide semiconductors. Prof Kim concluded, “Our research is essential for a sustainable green future – especially to connect the clean energy system with no or minimal carbon footprint.”

The sample in the photo above is quite clear and only slightly opaque. Its the best your humble reader has seen so far. One can be sure this work will trigger more as there is a great deal of potential in this solar field.

Massachusetts Institute of Technology researchers have analyzed the causes of many cost overruns on new nuclear power plants in the US, which have soared in the past 50 years. The findings may help designers of new plants build in resilience to prevent such added costs.

The 1150-megawatt Callaway nuclear power plant represented one of the largest and most complex challenges in Flour’s nuclear plant construction history to date. During the seven years from initial construction mobilization, more than 40 million man-hours of craft labor were expended. Image Credit: Fluor. Click image for the largest view.

Many analysts believe nuclear power will play an essential part in reducing global emissions of greenhouse gases, and finding ways to curb these rising costs could be an important step toward encouraging the construction of new plants, the researchers say.

The findings are being published in the journal Joule, in a paper by MIT professors Jessika Trancik and Jacopo Buongiorno, along with former students Philip Eash-Gates SM ’19, Magdalena Klemun PhD ’20, Goksin Kavlak PhD ’18, and Research Scientist James McNerney.

Among the surprising findings in the study, which covered 50 years of U.S. nuclear power plant construction data, was that, contrary to expectations, building subsequent plants based on an existing design actually costs more, not less, than building the initial plant.

The authors also found that while changes in safety regulations could account for some of the excess costs, that was only one of numerous factors contributing to the overages.

Trancik, who is an associate professor of energy studies in MIT’s Institute for Data, Systems and Society said, “It’s a known fact that costs have been rising in the U.S. and in a number of other locations, but what was not known is why and what to do about it.” The main lesson to be learned, she said, is that “we need to be rethinking our approach to engineering design.”

Part of that rethinking, she says, is to pay close attention to the details of what has caused past plant construction costs to spiral out of control, and to design plants in a way that minimizes the likelihood of such factors arising. This requires new methods and theories of technological innovation and change, which the team has been advancing over the past two decades.

For example, many of the excess costs were associated with delays caused by the need to make last-minute design changes based on particular conditions at the construction site or other local circumstances, so if more components of the plant, or even the entire plant, could be built offsite under controlled factory conditions, such extra costs could be substantially cut.

Specific design changes to the containment buildings surrounding the reactor could also help to reduce costs significantly, Trancik noted. For example, substituting some new kinds of concrete in the massive structures could reduce the overall amount of the material needed, and thus slash the onsite construction time as well as the material costs.

Many of the reasons behind the cost increases, Trancik said, “suggest that there’s a lack of resilience, in the process of constructing these plants, to variable construction conditions.” Those variations can come from safety regulations that are changing over time, but there are other reasons as well. “All of this points to the fact that there is a path forward to increasing resilience that involves understanding the mechanisms behind why costs increased in the first place.”

Consider overall construction costs are very sensitive to upfront design costs, for example: “If you’re having to go back and redo the design because of something about a particular site or a changing safety regulation, then if you build into your design that you have all of these different possibilities based on these things that could happen,” that can protect against the need for such last-minute redesign work.

“These are soft costs contributions,” Trancik said, which have not tended to be prioritized in the typical design process. “They’re not hardware costs, they are changes to the environment in which the construction is happening. . . If you build that in to your engineering models and your engineering design process, then you may be able to avoid the cost increases in the future.”

One approach, which would involve designing nuclear plants that could be built in factories and trucked to the site, has been advocated by many nuclear engineers for years. For example, rather than today’s huge nuclear plants, modular and smaller reactors could be completely self-contained and delivered to their final site with the nuclear fuel already installed. Numerous such plants could be ganged together to provide output comparable to that of larger plants, or they could be distributed more widely to reduce the need for long-distance transmission of the power. Alternatively, a larger plant could be designed to be assembled on site from an array of smaller factory-built subassemblies.

“This relationship between the hardware design and the soft costs really needs to be brought into the engineering design process,” she said, “but it’s not going to happen without a concerted effort, and without being informed by modeling that accounts for these potential ballooning soft costs.”

Trancik says that while some of the steps to control costs involve increased use of automated processes, these need to be considered in a societal context. “Many of these involve human jobs and it is important, especially in this time, where there’s such a need to create high-quality sustained jobs for people, this should also factor into the engineering design process. So it’s not that you need to look only at costs.” But the kind of analysis the team used, she said, can still be useful. “You can also look at the benefit of a technology in terms of jobs, and this approach to mechanistic modeling can allow you to do that.”

The methodology the team used to analyze the causes of cost overruns could potentially also be applied to other large, capital-intensive construction projects, Trancik said, where similar kinds of cost overruns often occur.

“One way to think about it as you’re bringing more of the entire construction process into manufacturing plants, that can be much more standardized.” That kind of increased standardization is part of what has led, for example, to a 95 percent cost reduction in solar panels and in lithium-ion batteries over the last few decades, she said. “We can think of it as making these larger projects more similar to those manufacturing processes.”

Buongiorno added that “only by reducing the cost of new plants can we expect nuclear energy to play a pivotal role in the upcoming energy transformation.”

This is very important work that one hopes utility firms and the nuclear designers, engineers and construction folks take to heart. For energy and modern life to continue for everyone that is consistent and affordable – nuclear is simply fundamental. We had to have it to get to this level of development and to stay and improve nuclear is essential for the foreseeable future. More. Better. Cheaper. Nuclear is the leader – even with many of the problems it has now.

National Institute of Standards and Technology (NIST) researchers have demonstrated a room-temperature method that could significantly reduce carbon dioxide levels in fossil-fuel power plant exhaust, one of the main sources of carbon emissions in the atmosphere and make it available for CO2 recycling.

Illustration of a novel room-temperature process to remove carbon dioxide (CO2) by converting the molecule into carbon monoxide (CO). Instead of using heat, the nanoscale method relies on the energy from surface plasmons (violet hue) that are excited when a beam of electrons (vertical beam) strikes aluminum nanoparticles resting on graphite, a crystalline form of carbon. In the presence of the graphite, aided by the energy derived from the plasmons, carbon dioxide molecules (black dot bonded to two red dots) are converted to carbon monoxide (black dot bonded to one red dot. The hole under the violet sphere represents the graphite etched away during the chemical reaction CO2 + C = 2CO. Image Credit: NIST. Click image for the largest view.

Although the researchers demonstrated this method in a small-scale, highly controlled environment with dimensions of just nanometers (billionths of a meter), they have already come up with concepts for scaling up the method and making it practical for real-world applications.

In addition to offering a potential new way of mitigating the effects of climate change, the chemical process employed by the scientists also could reduce costs and energy requirements for producing liquid hydrocarbons and other chemicals used by industry. That’s because the method’s byproducts include the building blocks for synthesizing methane, ethanol and other carbon-based compounds used in industrial processing.

The team tapped a novel energy source from the “nanoworld” to trigger a run-of-the-mill chemical reaction that eliminates carbon dioxide. In this reaction, solid carbon latches onto one of the oxygen atoms in carbon dioxide gas, reducing it to carbon monoxide. The conversion normally requires significant amounts of energy in the form of high heat – a temperature of at least 700° Celsius, hot enough to melt aluminum at normal atmospheric pressure.

Instead of heat, the team relied on the energy harvested from traveling waves of electrons, known as localized surface plasmons (LSPs), which surf on individual aluminum nanoparticles. The team triggered the LSP oscillations by exciting the nanoparticles with an electron beam that had an adjustable diameter. A narrow beam, about a nanometer in diameter, bombarded individual aluminum nanoparticles while a beam about a thousand times wider generated LSPs among a large set of the nanoparticles.

In the team’s experiment, the aluminum nanoparticles were deposited on a layer of graphite, a form of carbon. This allowed the nanoparticles to transfer the LSP energy to the graphite. In the presence of carbon dioxide gas, which the team injected into the system, the graphite served the role of plucking individual oxygen atoms from carbon dioxide, reducing it to carbon monoxide. The aluminum nanoparticles were kept at room temperature. In this way, the team accomplished a major feat: getting rid of the carbon dioxide without the need for a source of high heat.

Previous methods of removing carbon dioxide have had limited success because the techniques have required high temperature or pressure, employed costly precious metals, or had poor efficiency. In contrast, the LSP method not only saves energy but uses aluminum, a cheap and abundant metal.

Although the LSP reaction generates the poisonous gas carbon monoxide, the gas readily combines with hydrogen to produce essential hydrocarbon compounds, such as methane and ethanol, that are often used in industry, said NIST researcher Renu Sharma.

She and her colleagues, including scientists from the University of Maryland in College Park and DENSsolutions, in Delft, the Netherlands, reported their findings in Nature Materials.

Researcher Canhui Wang of NIST and the University of Maryland said, “We showed for the first time that this carbon dioxide reaction, which otherwise will only happen at 700° C or higher, can be triggered using LSPs at room temperature.”

The researchers chose an electron beam to excite the LSPs because the beam can also be used to image structures in the system as small as a few billionths of a meter. This enabled the team to estimate how much carbon dioxide had been removed. They studied the system using a transmission electron microscope (TEM).

Because both the concentration of carbon dioxide and the reaction volume of the experiment were so small, the team had to take special steps to directly measure the amount of carbon monoxide generated. They did so by coupling a specially modified gas cell holder from the TEM to a gas chromatograph mass spectrometer, allowing the team to measure parts-per-millions concentrations of carbon dioxide.

Sharma and her colleagues also used the images produced by the electron beam to measure the amount of graphite that was etched away during the experiment, a proxy for how much carbon dioxide had been taken away. They found that the ratio of carbon monoxide to carbon dioxide measured at the outlet of the gas cell holder increased linearly with the amount of carbon removed by etching.

Imaging with the electron beam also confirmed that most of the carbon etching – a proxy for carbon dioxide reduction – occurred near the aluminum nanoparticles. Additional studies revealed that when the aluminum nanoparticles were absent from the experiment, only about one-seventh as much carbon was etched.

Limited by the size of the electron beam, the team’s experimental system was small, only about 15 to 20 nanometers across (the size of a small virus).

To scale up the system so that it could remove carbon dioxide from the exhaust of a commercial power plant, a light beam may be a better choice than an electron beam to excite the LSPs, Wang said. Sharma proposes that a transparent enclosure containing loosely packed carbon and aluminum nanoparticles could be placed over the smokestack of a power plant. An array of light beams impinging upon the grid would activate the LSPs. When the exhaust passes through the device, the light-activated LSPs in the nanoparticles would provide the energy to remove carbon dioxide.

It will be interesting to learn if this technology will scale economically. For now we ca be impressed by the insight and innovation to get this powered and working at such a vastly reduced energy input. Impressive, indeed.

The aluminum nanoparticles, which are commercially available, should be evenly distributed to maximize contact with the carbon source and the incoming carbon dioxide, the team noted.

The new work also suggests that LSPs offer a way for a slew of other chemical reactions that now require a large infusion of energy to proceed at ordinary temperatures and pressures using plasmonic nanoparticles.

Sharma said, “Carbon dioxide reduction is a big deal, but it would be an even bigger deal, saving enormous amounts of energy, if we can start to do many chemical reactions at room temperature that now require heating.”

Gwangju Institute of Science and Technology (GIST) scientists have discovered that the amount of alkali metal introduced into crystals of flexible thin-film solar cells influences the path that charge carriers take to traverse between electrodes, thereby affecting the light-to-electricity conversion efficiency of the solar cell.

A digital camera image of a flexible CZTSSe solar cell. Image Credit: GIST. Click image for the largest view.

The press release asserts that given the immense application potential that such solar cells have today, this finding could be key to ushering in a green future.

Professor Dong-Seon Lee of GIST in Korea said, “When eco-friendly, inexpensive, versatile, and efficient solar cells are developed, all thermal and nuclear power plants will disappear, and solar cells installed over the ocean or in outer space will power our world.” His highly optimistic view of the future mirrors the visions of many researchers involved in the effort to improve solar cells.

Over the research history scientists have come to realize that doping – distorting a crystal structure by introducing an impurity – polycrystalline solar cells made by melting together crystals called CZTSSe with earth-abundant and eco-friendly alkali metals, such as sodium and potassium, can improve their light to electricity conversion efficiency while also leading to the creation of inexpensive flexible thin-film solar cells that could find many applications in a society that is increasingly making wearable electronics commonplace.

But why doping improves performance is yet unknown.

In a recent paper published in Advanced Science, Prof Lee and team reveal one part of this unknown. Their revelations come from their observations of composition and electric charge transport properties of CZTSSe cells doped with layers of sodium fluoride of varying thickness.

Upon analyzing these doped cells, Prof Lee and team saw that the amount of dopant determined the path that charge carriers took between electrodes, making the cell either more or less conductive. At an optimal doped-layer thickness of 25 nanometers, the charges flowed through the crystal via pathways that allowed for maximum conductivity. This in turn, the scientists hypothesized, affected the “fill factor” of the cell, which indicates the light-to-electricity conversion efficiency. At 25 nanometers, a record fill factor of 63% was obtained, a notable improvement over the previous limit of 50%. The overall performance was also competitive with this amount of doping.

These findings provide insight into CZTSSe and other polycrystalline solar cells, paving the way for improving them further and realizing a sustainable society. But the competitive performance of the solar cell that yielded these findings gives it real-world applications more tangible to us common folks, as Prof Lee explains: “We have developed flexible and eco-friendly solar cells that will be useful in many ways in our real lives, from building-integrated photovoltaics and solar panel roofs, to flexible electronic devices.” Given the bold vision that Prof Lee carries, perhaps a green economy is not too far away.

This is definitive work on getting thin film solar cells more efficiency deserving some attention and work on introducing it to scaling. There is also a noticeable enthusiasm in the team and the press release that evokes a smile and hope the dream gets closer to reality!


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