Penn State – 3D Imaging Technique Unlocks Properties of Perovskite Crystals – Applications for Perovskite Solar Cells


A reconstruction of a perovskite crystal (CaTiO3) grown on a similar perovskite substrate (NdGaO3) showing electron density and oxygen octahedral tilt. (insert) Artist’s conception of the interface between substrate and film. Credit: Yakun Yuan/Penn State

A team of materials scientists from Penn State, Cornell and Argonne National Laboratory have, for the first time, visualized the 3D atomic and electron density structure of the most complex perovskite crystal structure system decoded to date.

Perovskites are minerals that are of interest as electrical insulators, semiconductors, metals or superconductors, depending on the arrangement of their atoms and electrons.

Perovskite crystals have an unusual grouping of oxygen atoms that form an octahedron, an eight-sided polygon. This arrangement of oxygen atoms acts like a cage that can hold a large number of the elemental atoms in the periodic table. Additionally, other atoms can be fixed to the corners of a cube outside of the cage at precise locations to alter the material’s properties, for instance in changing a metal into an insulator, or a non-magnet into a ferromagnet.

In their current work, the team grew the very first discovered perovskite crystal, called calcium titanate, on top of a series of other perovskite crystal substrates with similar but slightly different oxygen cages at their surfaces. Because the thin film perovskite on top wants to conform to the structure of the thicker substrate, it contorts its cages in a process known as tilt epitaxy.

The researchers found this tilt epitaxy of calcium titanate caused a very ordinary material to take on the property of ferroelectricity, a spontaneous polarization, and to remain ferroelectric up to 900 Kelvin, around three times hotter than room temperature. They were also able to visualize the three-dimensional electron density distribution in calcium titanate thin film for the first time.

“We have been able to see atoms for quite some time, but not map them and their electron distribution in space in a crystal in three dimensions,” said Venkat Gopalan, professor of materials science and physics, Penn State. “If we can see not just where atomic nuclei are located in space, but also how their electron clouds are shared, that will tell us basically everything we need to know about the material in order to infer its properties.”

That was the challenge the team set for itself over five years ago when Gopalan gave his student and lead author of a new report in Nature Communications, Yakun Yuan, the project.

Based on a rarely used x-ray visualization technique called COBRA, for coherent Bragg rod analysis, originally developed by a group in Israel, Yuan figured out how to expand and modify the technique to analyze one of the most complicated, least symmetrical material systems studied to date: the strained three-dimensional perovskite crystal with octahedral tilts in all directions, grown on another equally complex crystal structure.

“To reveal 3D structural details at the atomic level, we had to collect extensive datasets using the most brilliant synchrotron X-ray source available at Argonne National Labs and carefully analyze them with the COBRA analysis code modified for accommodating the complexity of such low symmetry,” said Yakun Yuan.

Gopalan went on to explain that very few perovskite oxygen cages are perfectly aligned throughout the material. Some rotate counterclockwise in one layer of atoms and clockwise in the next. Some cages are squeezed out of shape or tilt in directions that are in or out of plane to the substrate surface.

From the interface of a film with the substrate it is grown on, all the way to its surface, each atomic layer may have unique changes in their structure and pattern.  All of these distortions make a difference in the material properties, which they can predict using a computational technique called density functional theory (DFT).

“The predictions from the DFT calculations provide insights that complement the experimental data and help explain the way that material properties change with the alignment or tilting of the perovskite oxygen cages,” said Prof. Susan Sinnott, whose group performed the theoretical calculations.

The team also validated their advanced COBRA technique against multiple images of their material using the powerful Titan transmission electron microscope in the Materials Research Institute at Penn State.  Since the electron microscopes image extremely thin electron transparent samples in a 2-dimensional projection, not all of the 3-dimensional image could be captured even with the best microscope available today and with multiple sample orientations.

Why Perovskite Solar Cells Are So Efficient

This is an area where 3-dimensional imaging by the COBRA technique outperformed the electron microscopy in such complex structures.

The researchers believe their COBRA technique is applicable to the study of many other three-dimensional low-symmetry atomic crystals.

Additional authors on “Three-dimensional atomic scale electron density reconstruction of octahedral tilt epitaxy in functionals perovskites” are Yanfu Lu, a Ph.D. student in Sinnott’s group, Greg Stone, Gopalan’s former postdoctoral scholar, Ke Wang, a staff scientist in Penn State’s Materials Research Institute, Darrell Schlom and his Ph.D. student Charles Brooks, Cornell University, and Hua Zhou, staff scientist, Argonne National Laboratory.

img_0885-1Penn State University

Funding was provided by the National Science Foundation with additional support provided through the Department of Energy and the Penn State 2D Crystal Consortium, a NSF Materials Innovation Platform, and the Penn State institute for CyberScience.

Contact Venkat Gopalan at vxg8@psu.edu or Hua Zhou at hzhou@aps.anl.gov.

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Quantum Dots leader completes deal to manufacture NextGen Cadmium Free QD’s in Asia


A leading US quantum dot and nanomaterials manufacturer has announced a licensing and manufacturing deal in Assam, India.

The company, Quantum Materials Corp (QMC), has a range of products which can be used to make anything from superior Ultra High Definition television displays to ultra-thin solar cells and more efficient batteries.

The agreement will not only lead to significant job opportunities in the locality of Assam, but is also a major step in deploying QMC’s extraordinary technologies in the region.

There is the opportunity to adopt next-generation solar photovoltaic technology in the area, after the implementation of recent tariffs on imported photovoltaics into India.

QMC’s cadmium-free quantum dots offer a less hazardous and eco-friendlier alternative for producers and consumers, providing them with the color benefit without the risks of toxicity or liability.

The incorporation of cadmium in quantum dots has restricted their adoption, keeping manufacturers from leveraging the benefits of the technology. Restriction of Hazardous Substances regulations currently state that 1,000 parts per million (ppm) cadmium can be used, however this exception will soon expire and only 100 ppm of cadmium will be acceptable. In 2015, the European Parliament banned the continued use of cadmium in display and lighting devices.

img_0866Read More: What are quantum dots? The Science and Applications

Furthermore, controls and regulations are growing in Asia, with China implementing new laws of its own.

QMC signed the License and Development Agreement with Amtronics CC to allow for the establishment of large scale, low cost quantum dot production for the development and future commercial manufacture of: ultra-high definition display panels, solid state lighting LEDs and quantum dot driven thin-film solar cells.

The Agreement provides Amtronics CC with the right to manufacture quantum dots and thin-film quantum dot solar cells for commercial supply in India, as well as the right to use the QDXTM trademark and technical data to support its marketing initiatives. Under the terms of the Agreement, QMC receives an immediate upfront license fee of US$1,000,000 in addition to technology development funding, scheduled milestone payments and royalties on all quantum dots/solar cells produced.

The 12,000 square feet nanotech-focused facility is being established as the anchor project within the recently announced Electronics Manufacturing Cluster in the Guwahati Tech City.

“We are extremely pleased to partner with Amtronics CC and Amtron as they establish the necessary infrastructure to support large scale thin-film, quantum dot based solar cell production in Assam India using QMC patented technologies” explained Stephen B. Squires, President and CEO of Quantum Materials Corp.

“India’s recent implementation of tariffs applied to imported solar photovoltaics creates an ideal opportunity to establish QMC’s next generation thin-film photovoltaics for broad adoption in the region. I am highly confident that our technologies will help India fulfill its goal to deploy low cost renewables as a significant step toward energy independence”

Dr. George Anthony Balchin, Managing Director of Amtronics CC added, “We are pleased to be involved and provide the initial US $20,000,000 in funding for this enterprise and are anxious to see these extraordinary technologies deployed in a region that will benefit from both the end product as well as the significant potential for job creation.

The initial capital infusion will be used to build out the facility, purchase all the production and process equipment, including the micro reactors, train the staff and provide the initial working capital. It is very rare and rewarding to be involved with a project that is the culmination of a group of like-minded individuals striving for a common goal that has so much potential to enhance the lives of so many.”

Commenting further QMC CEO Squires stated: “As India represents one of the largest renewable energy and consumer electronics markets in the world, our partnership with Amtronics CC is an important step in expanding the value of the QMC franchise globally. This partnership will allow us to address global challenges such as rising energy costs, energy security, increasing power consumption and environmental quality on a more rapid basis.”

How a ‘solar battery’ could bring electricity to rural areas – A ‘solar flow’ battery could “Harvest (energy) in the Daytime and Provide Electricity in the Evening


New solar flow battery with a 14.1 percent efficiency. Photo: David Tenenbaum, UW-Madison

Solar energy is becoming more and more popular as prices drop, yet a home powered by the Sun isn’t free from the grid because solar panels don’t store energy for later. Now, researchers have refined a device that can both harvest and store solar energy, and they hope it will one day bring electricity to rural and underdeveloped areas.

The problem of energy storage has led to many creative solutions, like giant batteries. For a paper published today in the journal Chem, scientists trying to improve the solar cells themselves developed an integrated battery that works in three different ways.

It can work like a normal solar cell by converting sunlight to electricity immediately, explains study author Song Jin, a chemist at the University of Wisconsin at Madison. It can store the solar energy, or it can simply be charged like a normal battery.

“IT COULD HARVEST IN THE DAYTIME, PROVIDE ELECTRICITY IN THE EVENING.”

It’s a combination of two existing technologies: solar cells that harvest light, and a so-called flow battery.

The most commonly used batteries, lithium-ion, store energy in solid materials, like various metals. Flow batteries, on the other hand, store energy in external liquid tanks.

What is A ‘Flow Battery’

This means they are very easy to scale for large projects. Scaling up all the components of a lithium-ion battery might throw off the engineering, but for flow batteries, “you just make the tank bigger,” says Timothy Cook, a University at Buffalo chemist and flow battery expert not involved in the study.

“You really simplify how to make the battery grow in capacity,” he adds. “We’re not making flow batteries to power a cell phone, we’re thinking about buildings or industrial sites.

Jin and his team were the first to combine the two features. They have been working on the battery for years, and have now reached 14.1 percent efficiency.

Jin calls this “round-trip efficiency” — as in, the efficiency from taking that energy, storing it, and discharging it. “We can probably get to 20 percent efficiency in the next few years, and I think 25 percent round-trip is not out of the question,” Jin says.

Apart from improving efficiency, Jin and his team want to develop a better design that can use cheaper materials.

The invention is still at proof-of-concept stage, but he thinks it could have a large impact in less-developed areas without power grids and proper infrastructure. “There, you could have a medium-scale device like this operate by itself,” he says. “It could harvest in the daytime, provide electricity in the evening.” In many areas, Jin adds, having electricity is a game changer, because it can help people be more connected or enable more clinics to be open and therefore improve health care.

And Cook notes that if the solar flow battery can be scaled, it can still be helpful in the US.

The United States might have plenty of power infrastructure, but with such a device, “you can disconnect and have personalized energy where you’re storing and using what you need locally,” he says. And that could help us be less dependent on forms of energy that harm the environment.

“Harvesting Energy from Light” – ORNL: Multimodal imaging shows strain can drive chemistry in a photovoltaic material –


In a thin film of a solar-energy material, molecules in twin domains (modeled in left and right panels) align in opposing orientations within grain boundaries (shown by scanning electron microscopy in the center panel). Strain can change chemical segregation and may be engineered to tune photovoltaic efficiency. Credit: Stephen Jesse/Oak Ridge National Laboratory, U.S. Dept. of Energy (hi-res image)

OAK RIDGE, Tenn., Sept. 25, 2018—A unique combination of imaging tools and atomic-level simulations has allowed a team led by the Department of Energy’s Oak Ridge National Laboratory to solve a longstanding debate about the properties of a promising material that can harvest energy from light.

The researchers used multimodal imaging to “see” nanoscale interactions within a thin film of hybrid organic–inorganic perovskite, a material useful for solar cells.

They determined that the material is ferroelastic, meaning it can form domains of polarized strain to minimize elastic energy. This finding was contrary to previous assumptions that the material is ferroelectric, meaning it can form domains of polarized electric charge to minimize electric energy.

“We found that people were misguided by the mechanical signal in standard electromechanical measurements, resulting in the misinterpretation of ferroelectricity,” said Yongtao Liu of ORNL, whose contribution to the study became a focus of his PhD thesis at the University of Tennessee, Knoxville (UTK).

Olga Ovchinnikova, who directed the experiments at ORNL’s Center for Nanophase Materials Sciences (CNMS), added, “We used multimodal chemical imaging—scanning probe microscopy combined with mass spectrometry and optical spectroscopy—to show that this material is ferroelastic and how the ferroelasticity drives chemical segregation.”

The findings, reported in Nature Materials, revealed that differential strains cause ionized molecules to migrate and segregate within regions of the film, resulting in local chemistry that may affect the transport of electric charge.

The understanding that this unique suite of imaging tools enables allows researchers to better correlate structure and function and fine-tune energy-harvesting films for improved performance.

“We want to predictively make grains of particular sizes and geometries,” Liu said. “The geometry is going to control the strain, and the strain is going to control the local chemistry.”

For their experiment, the researchers made a thin film by spin-casting a perovskite on an indium tin oxide–coated glass substrate. This process created the conductive, transparent surface a photovoltaic device would need—but also generated strain.

To relieve the strain, tiny ferroelastic domains formed. One type of domain was “grains,” which look like what you might see flying over farmland with patches of different crops skewed in relation to one another. Within grains, sub-domains formed, similar to rows of two plant types alternating in a patch of farmland. These adjacent but opposing rows are “twin domains” of segregated chemicals.

The technique that scientists previously used to claim the material was ferroelectric was piezoresponse force microscopy (“piezo” means “pressure), in which the tip of an atomic force microscope (AFM) measures a mechanical displacement due to its coupling with electric polarization—namely, electromechanical displacement. “But you’re not actually measuring the true displacement of the material,” Ovchinnikova warned. “You’re measuring the deflection of this whole ‘diving board’ of the cantilever.” Therefore, the researchers used a new measurement technique to separate cantilever dynamics from displacement of the material due to piezoresponse—the Interferometric Displacement Sensor (IDS) option for the Cypher AFM, developed by co-author Roger Proksch, CEO of Oxford Instruments Asylum Research.

They found the response in this material is from cantilever dynamics alone and is not a true piezoresponse, proving the material is not ferroelectric.

“Our work shows the effect believed due to ferroelectric polarization can be explained by chemical segregation,” Liu said.

The study’s diverse microscopy and spectroscopy measurements provided experimental data to validate atomic-level simulations. The simulations bring predictive insights that could be used to design future materials.

We’re able to do this because of the unique environment at CNMS where we have characterization, theory and synthesis all under one roof,” Ovchinnikova said.

“We didn’t just utilize mass spectrometry because [it] gives you information about local chemistry. We also used optical spectroscopy and simulations to look at the orientation of the molecules, which is important for understanding these materials. Such a cohesive chemical imaging capability at ORNL leverages our functional imaging.”

Collaborations with industry allow ORNL to have unique tools available for scientists, including those that settled the debate about the true nature of the light-harvesting material. For example, an instrument that uses helium ion microscopy (HIM) to remove and ionize molecules was coupled with a secondary ion mass spectroscopy (SIMS) to identify molecules based on their weights.

The HIM-SIMS instrument ZEISS ORION NanoFab was made available to ORNL from developer ZEISS for beta testing and is one of only two such instruments in the world. Similarly, the IDS instrument from Asylum Research, which is a laser Doppler vibrometer, was also made available to ORNL for beta testing and is the only one in existence.

“Oak Ridge National Laboratory researchers are naturally a good fit for working with industry because they possess unique expertise and are able to first use the tools the way they’re meant to,” said Proksch of Asylum. “ORNL has a facility [CNMS] that makes instruments and expertise available to many scientific users who can test tools on different problems and provide strong feedback during beta testing as vendors develop and improve the tools, in this case our new IDS metrological AFM.”

The title of the paper is “Chemical Nature of Ferroelastic Twin Domains in CH3NH3PbI3 Perovskite.”

The research was supported by ORNL’s Laboratory Directed Research and Development Program and conducted at CNMS, a DOE Office of Science User Facility at ORNL.

UT-Battelle manages ORNL for DOE’s Office of Science. The single largest supporter of basic research in the physical sciences in the United States, the Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit https://science.energy.gov/.

NREL: Envisioning Net-Zero Emission Energy Systems


NREL researchers contribute to a major journal article describing pathways to net-zero emissions for particularly difficult-to-decarbonize economic sectors

As global energy consumption continues to grow—by some projections, more than doubling by 2100—all sectors of the economy will need to find ways to drastically reduce their carbon dioxide emissions if average global temperatures are to be held under international climate targets. Two NREL authors contributed to a recently published article in Science that examined potential barriers and opportunities to decarbonizing certain energy systems that are essential to modern civilization but remain stubbornly reliant on carbon-emitting processes.

Difficult to Decarbonize Energy Sectors Contribute 27% of Carbon Emissions

Many sectors of the economy, such as light-duty transportation, heating, cooling, and lighting, could be straightforward to decarbonize through electrification and use of low- or net-zero-emitting energy sources. However, some energy uses, such as aviation, long-distance transport and shipping, steel and cement production, and a highly reliable electricity supply, will be more difficult to decarbonize. Together, these sectors contribute 27% of global carbon emissions today. With global demand for many of these sectors growing rapidly, solutions are urgently needed, the article’s authors write.

“The timeframes and economic costs of any energy transition are enormous. Most technologies installed today will have a lifetime of perhaps 30 to 50 years and the transition from research to actual deployment can also be quite lengthy,” said Bri-Mathias Hodge, an author on the paper and manager of the Power Systems Design and Studies Group at NREL. “Because of this we need to be able to identify the most pertinent issues that will need to be solved fairly far in the future and get started now, before we find ourselves heavily invested in even more carbon-intensive, long-term infrastructure.”

Diverse Expert Perspectives Informed Study

Discussion of the article’s underlying issues began at an Aspen Global Change Institute meeting in July 2016. “The diversity and depth of expertise at the workshop—and contributing to the paper—were outstanding,” said Doug Arent, the other NREL researcher to contribute to the paper and deputy associate lab director for Scientific Computing and Energy Analysis. “It was great to hear the different perspectives and learn about new areas that are related to our work at NREL, but that I don’t get to hear about every day at NREL,” added Hodge.

Considering demographic trends, institutional barriers, and economic and technological constraints, the group of researchers concluded that future net-zero emission systems will depend critically on integration of now-discrete energy industries. Although a range of existing low or net zero emitting energy technologies exist for these energy services, they may only be able to fully meet future energy demands through cross-sector coordination. Collaboration could speed research and development of new technologies and coordinating operations across sectors could better utilize capital-intensive assets, create broader markets, and streamline regulations.

Research Should Pursue Technologies and Integration to Decarbonize These Sectors

The article’s authors suggest two broad research thrusts: research in technologies and processes that could decarbonize these energy services, and research in systems integration to provide these energy services in a more reliable and cost-effective way.

The Science article concludes by stating, “if we want to achieve a robust, reliable, affordable, net-zero emissions energy system later this century, we must be researching, developing, demonstrating, and deploying those candidate technologies now.”

Long-lasting solar cells from and “unexpected gray area” … U of Wisconsin-Madison Make Surprising Discovery


anunexpectedUW-Madison engineers found a way to dramatically extend the lifespan of solar energy-harvesting devices, which use energy from sunlight to generate hydrogen from water. Credit: iStock

University of Wisconsin-Madison materials engineers have made a surprising discovery that could dramatically improve the lifetime of solar energy harvesting devices.

The findings allowed them to achieve the longest-ever lifetime for a key component of some types of photovoltaic cells called the photoelectrochemical electrode, which uses sunlight to split water into its constituent parts of hydrogen and oxygen.

In a paper published July 24, 2018, in the research journal Nano Letters, a team led by UW-Madison materials science and engineering Ph.D. student Yanhao Yu and his advisor, Professor Xudong Wang, described a strategy that extended the lifetime of a photochemical electrode to a whopping 500 hours—more than five times (5X) the typical 80-hour lifespan.

Usually, these types of electrodes are made of silicon, which splits water well, but is highly unstable and quickly degrades when it comes into contact with corrosive conditions. To protect these electrodes, engineers often thinly coat their surfaces.

It’s a tactic that only delays their eventual breakdown—sometimes after a few days and sometimes within hours.

“Performance varies widely and nobody really knows why. It’s a big question,” says Wang, a professor of materials science and engineering at UW-Madison.

Intriguingly, the researchers didn’t make any changes to the coating material. Rather, they boosted the electrode’s lifetime by applying an even thinner coating of  than usual.

In other words, less really was more!

Key to this exceptional performance was the team’s discovery about the atomic structure of titanium dioxide thin , which the researchers create using a technique called .

Previously, researchers believed that the atoms in titanium dioxide thin films adopted one of two conformations—either scrambled and disordered in a state referred to as “amorphous,” or locked into a regularly repeating and predictable arrangement called the crystalline form.

Crucially, researchers were certain that all the atoms in a given thin film behaved the same way. Crystalline or amorphous. Black or white. No in-between.

What Wang colleagues found, however, is a gray area: They saw that small pockets of an in-between state persisted in the final coatings—the  in these areas was neither amorphous nor crystalline. These intermediates have never been observed before.

“This is a cutting edge of materials synthesis science,” says Wang. “We’re thinking that crystallization is not as straightforward as people believe.”

Observing those intermediates was no easy feat. Enter Wang’s colleague Paul Voyles, a microscopy expert who leveraged UW-Madison’s unique facilities to perform sophisticated scanning transmission electron microscopy measurements, enabling him to detect the tiny structures.

From there, the researchers determined those intermediates lowered the lifetime of titanium dioxide thin films by leading to spikes of electronic current that ate tiny holes in the protective coatings.

Eliminating those intermediates—thus extending the ‘s lifetime—is as simple as using a thinner film.

Thinner films make it more difficult for intermediates to form within the film, so by reducing the thickness by three quarters (from 10 nanometers to 2.5), the researchers created coatings that lasted more than five times longer than traditional coatings.

And now that they’ve discovered these peculiar structures, the researchers want to learn more about how they form and influence amorphous film properties. That’s knowledge that could reveal other strategies for eliminating them—which not only could improve performance, says Wang, but also open new opportunities in other energy-related systems, such as catalysts, solar cells and batteries.

“These intermediates could be something very important that has been overlooked,” says Wang. “They could be a critical aspect that controls properties of the film.”

 Explore further: Discovery brings renewable fuel production one step closer to reality

More information: Yanhao Yu et al. Metastable Intermediates in Amorphous Titanium Oxide: A Hidden Role Leading to Ultra-Stable Photoanode Protection, Nano Letters (2018). DOI: 10.1021/acs.nanolett.8b02559

 

Is Reliable Energy Storage (and Markets) On The Horizon?


Green and renewable energy markets are bringing power to millions with virtually no adverse environmental impacts, but before we can count on renewables for widespread reliability, one critical innovation must arrive: storage.

image-223

PetersenDean Inc. employees install solar panels on the roof of a home in Lafayette, California, U.S., Photographer: David Paul Morris/Bloomberg

On Tuesday, May 15, 2018. California became the first state in the U.S. to require solar panels on almost all new homes. Most new units built after Jan. 1, 2020, will be required to include solar systems as part of the standards adopted by the California Energy Commission.

While hydroelectric and some other renewable sources can generate power around the clock, solar and wind energy are irregular and not necessarily consistent sources for 24/7 projections.

Storms and darkness disrupt solar farms, while dozens of meteorological phenomena can impact wind farms. Because these sources have natural peaks, they cannot be made to align with consumer power demand without effective storage. Solar and wind may be able to meet demand during the day or a short period, but when energy is high and demand is low, the power generated must either be used or wasted if it cannot be stored in some type of battery.

According to projections from GTM Research and the Energy Storage Association, the energy storage market is expected to grow 17x from 2017 and 2023. This projection accounts for private and commercial deployment of storage capacity, including impacts from government policies like California’s solar panel mandate.

During the same interval, the energy storage market is expected to grow 14x in dollar value.

The exact type of storage deployments in these projections varies. Recent innovations have included advancements in traditional battery technology as well as battery alternatives like liquid air storage.

In New York, one project included a megawatt scaled lithium-ion battery storage system to replace lead acid schemes. The liquid air storage, however, uses excess energy to cool air in pressurized chambers until it is liquid. Rather than storing electrical or chemical energy like a battery, the process stores potential energy.

When demand arises, the liquefied air is allowed to rapidly heat and expand, turning turbines to generate electricity.

Meanwhile, Tesla has added nearly a third of the annual global energy storage deployments since 2015. Leading the charge with low-cost lithium-ion batteries, Telsla and other innovators are bringing global capacity up quickly.

These energy storage devices are versatile, capable of storing energy from any source–fossil fuel or renewable– and in any place–private homes or industrial operations.

With battery costs continuing to decrease and battery alternatives coming into the fore, projections of storage capacity are indeed quite possible. Assuming the electric industry can indeed upgrade its current infrastructure, new grid connections means that energy will be able to be shared more than ever, perhaps even traveling far distances during peak or be stored for non-peak use anywhere on the grid.

When storage costs and capacity align with market incentives, we may just see a renewable energy revolution, one that makes distributed generation mainstream for all consumers.

** Contributed from Forbes Energy

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Forbes on Energy: We Don’t Need Solar And Wind To Save The Climate — And It’s A Good Thing, Too


France and Sweden show solar and wind are not needed to [+] Special Contributor, M. Shellenberger

For 30 years, experts have claimed that humankind needs to switch to solar and wind energy to address climate change. But do we really?

Consider the fact that, while no nation has created a near-zero carbon electricity supply out of solar and wind, the only successful efforts to create near-zero carbon electricity supplies didn’t require solar or wind whatsoever.

As such solar and wind aren’t just insufficient, they are also unnecessary for solving climate change.

That turns out to be a good thing.

Sunlight and wind are inherently unreliable and energy-dilute. As such, adding solar panels and wind turbines to the grid in large quantities increases the cost of generating electricity, locks in fossil fuels, and increases the environmental footprint of energy production.

There is a better way. But to understand what it is, we first must understand the modern history of renewable energies.

Renewables Revolution: Always Just Around the Corner

Most people think of solar and wind as new energy sources. In fact, they are two of our oldest.

The predecessor to Stanford University Professor Mark Jacobson, who advocates “100 percent renewables,” is A man named John Etzler.

In 1833, Etzler proposed to build massive solar power plants that used mirrors to concentrate sunlight on boilers, mile-long wind farms, and new dams to store power.

Even electricity-generating solar panels and wind turbines are old. Both date back to the late 1800s.

Throughout the 20th Century, scientists claimed — and the media credulously reported — that solar, wind, and batteries were close to a breakthrough that would allow them to power all of civilization.

Consider these headlines from The New York Times and other major newspapers:

• 1891: “Solar Energy: What the Sun’s Rays Can Do and May Yet Be Able to Do“ — The author notes that while solar energy was not yet economical “…the day is not unlikely to arrive before long…”

• 1923: “World Awaits Big Invention to Meet Needs of Masses “…solar energy may be developed… or tidal energy… or solar energy through the production of fuel.”

• 1931: “Use of Solar Energy Near a Solution.” “Improved Device Held to Rival Hydroelectric Production”

• 1934: “After Coal, The Sun” “…surfaces of copper oxide already available”

• 1935: “New Solar Engine Gives Cheap Power”

• 1939. “M.I.T. Will ‘Store’ Heat of the Sun”

• 1948: “Changing Solar Energy into Fuel “Blocked Out” in GM Laboratory”  “…the most difficult part of the problem is over…”

• 1949: “U.S. Seeks to Harness Sun, May Ask Big Fund, Krug Says”

Reporters were as enthusiastic about renewables in 1930s as they are today.

“It is just possible the world is standing at a turning point,” a New York Times reporter gushed in 1931, “in the evolution of civilization similar to that which followed the invention by James Watt of the steam engine.”

Decade after decade, scientists and journalists re-discovered how much solar energy fell upon the earth.

“Even on such an area as small as Manhattan Island the noontime heat is enough, could it be utilized, to drive all the steam engines in the world,” The Washington Star reported in 1891.

Progress in chemistry and materials sciences was hyped. “Silver Selenide is Key Substance,” The New York Times assured readers.

In 1948, Interior Secretary Krug called for a clean energy moonshot consisting of “hundreds of millions” for solar energy, pointing to its “tremendous potential.”

R&D subsidies for solar began shortly after and solar and wind production subsidies began in earnest in the 1970s.

Solar and wind subsidies increased substantially, and were increased in 2005 and again in 2009 on the basis of a breakthrough being just around the corner.

By 2016, renewables were receiving 94 times more in U.S. subsidies than nuclear and 46 times more than fossil fuels per unit of energy generated.

According to Bloomberg New Energy Finance (BNEF), public and private actors spent $1.1 trillion on solar and over $900 billion on wind between 2007 and 2016.

Global investment in solar and wind hovered at around $300 billion per year between 2010 and 2016.

Did the solar and wind energy revolution arrive?

Judge for yourself: in 2016, solar and wind constituted 1.3 and 3.9 percent of the planet’s electricity, respectively.

Real World Renewables

Are there places in the world where wind and solar have become a significant share of electricity supplies?

The best real-world evidence for wind’s role in decarbonization comes from the nation of Denmark. By 2017, wind and solar had grown to become 48 and 3 percent of Denmark’s electricity.

Does that make Denmark a model?

Not exactly. Denmark has fewer people than Wisconsin, a land area smaller than West Virginia, and an economy smaller than the state of Washington.

Moreover, the reason Denmark was able to deploy so much wind was because it could easily export excess wind electricity to neighboring countries — albeit at a high cost: Denmark today has the most expensive electricity in Europe.

And as one of the world’s largest manufacturers of turbines, Denmark could justify expensive electricity as part of its export strategy.

As for solar, those U.S. states that have deployed the most of it have seen sharp rises in their electricity costs and prices compared to the national average.

As recently as two years ago, some renewable energy advocates held up Germany as a model for the world.

No more. While Germany has deployed some of the most solar and wind in the world, its emissions have been flat for a decade while its electricity has become the second most expensive in Europe.

More recently, Germany has permitted the demolition of old forests, churches, and villages in order to mine and burn coal.

Meanwhile, the two nations whose electricity sectors produce some of the least amount of carbon emissions per capita of any developed nation did so with very little solar and wind: France and Sweden.

Sweden last year generated a whopping 95 percent of its total electricity from zero-carbon sources, with 42 and 41 coming from nuclear and hydroelectric power.

France generated 88 percent of its total electricity from zero-carbon sources, with 72 and 10 coming from nuclear and hydroelectric power.

Other nations like Norway, Brazil, and Costa Rica have almost entirely decarbonized their electricity supplies with the use of hydroelectricity alone.

That being said, hydroelectricity is far less reliable and scalable than nuclear.

Brazil is A case in point. Hydro has fallen from over 90 percent of its electricity 20 years ago to about two-thirds in 2016. Because Brazil failed to grow its nuclear program in the 1990s, it made up for new electricity growth with fossil fuels.

And both Brazil and hydro-heavy California stand as warnings against relying on hydro-electricity in a period of climate change. Both had to use fossil fuels to make up for hydro during recent drought years.

That leaves us with nuclear power as the only truly scalable, reliable, low-carbon energy source proven capable of eliminating carbon emissions from the power sector.

Why This is Good News

The fact that we don’t need renewables to solve climate change is good news for humans and the natural environment.

The dilute nature of water, sunlight, and wind means that up to 5,000 times more land and 10 – 15 times more concrete, cement, steel, and glass, are required than for nuclear plants.

All of that material throughput results in renewables creating large quantities of waste, much of it toxic.

For example, solar panels create 200 – 300 times more hazardous waste than nuclear, with none of it required to be recycled or safely contained outside of the European Union.

Meanwhile, the huge amounts of land required for solar and wind production has had a devastating impact on rare and threatened desert tortoises, bats, and eagles — even when solar and wind are at just a small percentage of electricity supplies.

Does this mean renewables are never desirable?

Not necessarily. Hydroelectric dams remain the way many poor countries gain access to reliable electricity, and both solar and wind might be worthwhile in some circumstances.

But there is nothing in either their history or their physical attributes that suggests solar and wind in particular could or should be the centerpiece of efforts to deal with climate change.

In fact, France demonstrates the costs and consequences of adding solar and wind to an electricity system where decarbonization is nearly complete.

France is already seeing its electricity prices rise as a result of deploying more solar and wind.

Because France lacks Sweden’s hydroelectric potential, it would need to burn far more natural gas (and/or petroleum) in order to integrate significantly more solar and wind.

If France were to reduce the share of its electricity from nuclear from 75 percent to 50 percent — as had been planned — carbon emissions and the cost of electricity would rise.

It is partly for this reason that France’s president recently declared he would not reduce the amount of electricity from nuclear.

Some experts recently pointed out that nuclear plants, like hydroelectric dams, can ramp up and down. France currently does so to balance demand.

But ramping nuclear plants to accommodate intermittent electricity from solar and wind simply adds to the cost of making electricity without delivering fewer emissions or much in the way of cost-savings. That’s because only very small amounts of nuclear fuel and no labor is saved when nuclear plants are ramped down.

Do We Need Solar and Wind to Save Nuclear?

While solar and wind are largely unnecessary at best and counterproductive at worst when it comes to combating climate change, might we need to them in support of a political compromise to prevent nuclear plants from closing?

At least in some circumstances, the answer is yes. Recently in New Jersey, for example, nuclear energy advocates had to accept a subsidy rate 18 to 28 times higher for solar than for nuclear.

The extremely disproportionate subsidy for solar was a compromise in exchange for saving the state’s nuclear plants.

While nuclear enjoys the support of just half of the American people, for example, solar and wind are supported by 70 to 80 percent of them. Thus, in some cases, it might make sense to package nuclear and renewables together.

But we should be honest that such subsidies for solar and wind are policy sweeteners needed to win over powerful financial interests and not good climate policy.

What matters most is that we accept that there are real world physical obstacles to scaling solar and wind.

Consider that the problem of the unreliability of solar has been discussed for as long as there have existed solar panels. During all of that time, solar advocates have waved their hands about potential future solutions.

“Serious problems will, of course, be raised by the fact that sun-power will not be continuous,” wrote a New York Times reporter in 1931. “Whether these will be solved by some sort of storage arrangement or by the operating of photogenerators in conjuction with some other generator cannot be said at present.”

We now know that, in the real world, electricity grid managers cope with the unreliability of solar by firing up petroleum and natural gas generators.

As such —  while there might be good reasons to continue to subsidize the production of solar and wind — their role in locking in fossil fuel generators means that climate change should not be one of them.

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High efficiency solar power conversion allowed by a novel composite material


A composite thin film made of two different inorganic oxide materials significantly improves the performance of solar cells, as recently demonstrated by a joint team of researchers led by Professor Federico Rosei at the Institut national de la recherche scientifique (INRS), and Dr. Riad Nechache from École de technologie supérieure (ÉTS), both in the Montreal Area (Canada).

Following an original device concept, Mr. Joyprokash Chakrabartty, the researchers have developed this new composite thin film material which combines two different crystal phases comprising the atomic elements bismuth, manganese, and oxygen.

The combination of phases with two different compositions optimizes this material’s ability to absorb solar radiation and transform it into electricity. The results are highly promising for the development of future solar technologies, and also potentially useful in other optoelectronic devices.

The results of this research are discussed in an article published in Nature Photonics (“Improved photovoltaic performance from inorganic perovskite oxide thin films with mixed crystal phases”) by researchers and lead author Mr. Joyprokash Chakrabartty.

The key discovery consists in the observation that the composite thin film—barely 110 nanometres thick—absorbs a broader portion of the solar spectrum compared to the wavelengths absorbed in the thin films made of the two individual materials. The interfaces between the two different phases within the composite film play a crucial role in converting more sunlight into electricity. This is a surprising, novel phenomenon in the field of inorganic perovskite oxide-based solar cells.

The composite material leads to a power conversion efficiency of up to 4.2%, which is a record value for this class of materials.

Source: INRS

NREL, University of Washington Scientists Elevate Quantum Dot Solar Cell World Record to 13.4 Percent



Researchers at the U.S. Department of Energy’s (DOE) National Renewable Energy Laboratory (NREL) established a new world efficiency record for quantum dot solar cells, at 13.4 percent.

Colloidal quantum dots are electronic materials and because of their astonishingly small size (typically 3-20 nanometers in dimension) they possess fascinating optical properties. 


Quantum dot solar cells emerged in 2010 as the newest technology on an NREL chart that tracks research efforts to convert sunlight to electricity with increasing efficiency. 

The initial lead sulfide quantum dot solar cells had an efficiency of 2.9 percent. Since then, improvements have pushed that number into double digits for lead sulfide reaching a record of 12 percent set last year by the University of Toronto. 

The improvement from the initial efficiency to the previous record came from better understanding of the connectivity between individual quantum dots, better overall device structures and reducing defects in quantum dots.


 NREL scientists Joey Luther and Erin Sanehira are part of a team that has helped NREL set an efficiency record of 13.4% for a quantum dot solar cell.

The latest development in quantum dot solar cells comes from a completely different quantum dot material. The new quantum dot leader is cesium lead triiodide (CsPbI3), and is within the recently emerging family of halide perovskite materials. 

In quantum dot form, CsPbI3 produces an exceptionally large voltage (about 1.2 volts) at open circuit.

“This voltage, coupled with the material’s bandgap, makes them an ideal candidate for the top layer in a multijunction solar cell,” said Joseph Luther, a senior scientist and project leader in the Chemical Materials and Nanoscience team at NREL. 

The top cell must be highly efficient but transparent at longer wavelengths to allow that portion of sunlight to reach lower layers. 
Tandem cells can deliver a higher efficiency than conventional silicon solar panels that dominate today’s solar market.

This latest advance, titled “Enhanced mobility CsPbI3 quantum dot arrays for record-efficiency, high-voltage photovoltaic cells,” is published in Science Advances. The paper was co-authored by Erin Sanehira, Ashley Marshall, Jeffrey Christians, Steven Harvey, Peter Ciesielski, Lance Wheeler, Philip Schulz, and Matthew Beard, all from NREL; and Lih Lin from the University of Washington.

The multijunction approach is often used for space applications where high efficiency is more critical than the cost to make a solar module. 
The quantum dot perovskite materials developed by Luther and the NREL/University of Washington team could be paired with cheap thin-film perovskite materials to achieve similar high efficiency as demonstrated for space solar cells, but built at even lower costs than silicon technology–making them an ideal technology for both terrestrial and space applications.

“Often, the materials used in space and rooftop applications are totally different. It is exciting to see possible configurations that could be used for both situations,” said Erin Sanehira a doctoral student at the University of Washington who conducted research at NREL.

The NREL research was funded by DOE’s Office of Science, while Sanehira and Lin acknowledge a NASA space technology fellowship.

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.