Category Archives: energy

Fireworks for fuel?

Scientists are attempting to harness the power in fireworks for use as fuel according to a Jan. 18, 2017 news item on Nanowerk,

The world relies heavily on gasoline and other hydrocarbons to power its cars and trucks. In search of an alternative fuel type, some researchers are turning to the stuff of fireworks and explosives: metal powders. And now one team is reporting a method to produce a metal nanopowder fuel with high energy content that is stable in air and doesn’t go boom until ignited.

A Jan. 18, 2017 American Chemical Society (ACS) news release, which originated the news item, expands on the theme,

Hydrocarbon fuels are liquid at room temperature, are simple to store, and their energy can be used easily in cars and trucks. Metal powders, which can contain large amounts of energy, have long been used as a fuel in explosives, propellants and pyrotechnics. It might seem counterintuitive to develop them as a fuel for vehicles, but some researchers have proposed to do just that. A major challenge is that high-energy metal nanopowder fuels tend to be unstable and ignite on contact with air. Albert Epshteyn and colleagues wanted to find a way to harness and control them, producing a fuel with both high energy content and good air stability.

The researchers developed a method using an ultrasound-mediated chemical process to combine the metals titanium, aluminum and boron with a sprinkle of hydrogen in a mixed-metal nanopowder fuel. The resulting material was both more stable and had a higher energy content than the standard nano-aluminum fuels. With an energy density of at least 89 kilojoules/milliliter, which is significantly superior to hydrocarbons’ 33 kilojoules/milliliter, this new titanium-aluminum-boron nanopowder packs a big punch in a small package.

Here’s a link to and a citation for the paper,

Optimization of a High Energy Ti-Al-B Nanopowder Fuel by Albert Epshteyn, Michael Raymond Weismiller, Zachary John Huba, Emily L. Maling, and Adam S. Chaimowitz. Energy Fuels, DOI: 10.1021/acs.energyfuels.6b02321 Publication Date (Web): December 30, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall.

Going underground to observe atoms in a bid for better batteries

A Jan. 16, 2017 news item on ScienceDaily describes what lengths researchers at Stanford University (US) will go to in pursuit of their goals,

In a lab 18 feet below the Engineering Quad of Stanford University, researchers in the Dionne lab camped out with one of the most advanced microscopes in the world to capture an unimaginably small reaction.

The lab members conducted arduous experiments — sometimes requiring a continuous 30 hours of work — to capture real-time, dynamic visualizations of atoms that could someday help our phone batteries last longer and our electric vehicles go farther on a single charge.

Toiling underground in the tunneled labs, they recorded atoms moving in and out of nanoparticles less than 100 nanometers in size, with a resolution approaching 1 nanometer.

A Jan. 16, 2017 Stanford University news release (also on EurekAlert) by Taylor Kubota, which originated the news item, provides more detail,

“The ability to directly visualize reactions in real time with such high resolution will allow us to explore many unanswered questions in the chemical and physical sciences,” said Jen Dionne, associate professor of materials science and engineering at Stanford and senior author of the paper detailing this work, published Jan. 16 [2017] in Nature Communications. “While the experiments are not easy, they would not be possible without the remarkable advances in electron microscopy from the past decade.”

Their experiments focused on hydrogen moving into palladium, a class of reactions known as an intercalation-driven phase transition. This reaction is physically analogous to how ions flow through a battery or fuel cell during charging and discharging. Observing this process in real time provides insight into why nanoparticles make better electrodes than bulk materials and fits into Dionne’s larger interest in energy storage devices that can charge faster, hold more energy and stave off permanent failure.

Technical complexity and ghosts

For these experiments, the Dionne lab created palladium nanocubes, a form of nanoparticle, that ranged in size from about 15 to 80 nanometers, and then placed them in a hydrogen gas environment within an electron microscope. The researchers knew that hydrogen would change both the dimensions of the lattice and the electronic properties of the nanoparticle. They thought that, with the appropriate microscope lens and aperture configuration, techniques called scanning transmission electron microscopy and electron energy loss spectroscopy might show hydrogen uptake in real time.

After months of trial and error, the results were extremely detailed, real-time videos of the changes in the particle as hydrogen was introduced. The entire process was so complicated and novel that the first time it worked, the lab didn’t even have the video software running, leading them to capture their first movie success on a smartphone.

Following these videos, they examined the nanocubes during intermediate stages of hydrogenation using a second technique in the microscope, called dark-field imaging, which relies on scattered electrons. In order to pause the hydrogenation process, the researchers plunged the nanocubes into an ice bath of liquid nitrogen mid-reaction, dropping their temperature to 100 degrees Kelvin (-280 F). These dark-field images served as a way to check that the application of the electron beam hadn’t influenced the previous observations and allowed the researchers to see detailed structural changes during the reaction.

“With the average experiment spanning about 24 hours at this low temperature, we faced many instrument problems and called Ai Leen Koh [co-author and research scientist at Stanford’s Nano Shared Facilities] at the weirdest hours of the night,” recalled Fariah Hayee, co-lead author of the study and graduate student in the Dionne lab. “We even encountered a ‘ghost-of-the-joystick problem,’ where the joystick seemed to move the sample uncontrollably for some time.”

While most electron microscopes operate with the specimen held in a vacuum, the microscope used for this research has the advanced ability to allow the researchers to introduce liquids or gases to their specimen.

“We benefit tremendously from having access to one of the best microscope facilities in the world,” said Tarun Narayan, co-lead author of this study and recent doctoral graduate from the Dionne lab. “Without these specific tools, we wouldn’t be able to introduce hydrogen gas or cool down our samples enough to see these processes take place.”

Pushing out imperfections

Aside from being a widely applicable proof of concept for this suite of visualization techniques, watching the atoms move provides greater validation for the high hopes many scientists have for nanoparticle energy storage technologies.

The researchers saw the atoms move in through the corners of the nanocube and observed the formation of various imperfections within the particle as hydrogen moved within it. This sounds like an argument against the promise of nanoparticles but that’s because it’s not the whole story.

“The nanoparticle has the ability to self-heal,” said Dionne. “When you first introduce hydrogen, the particle deforms and loses its perfect crystallinity. But once the particle has absorbed as much hydrogen as it can, it transforms itself back to a perfect crystal again.”

The researchers describe this as imperfections being “pushed out” of the nanoparticle. This ability of the nanocube to self-heal makes it more durable, a key property needed for energy storage materials that can sustain many charge and discharge cycles.

Looking toward the future

As the efficiency of renewable energy generation increases, the need for higher quality energy storage is more pressing than ever. It’s likely that the future of storage will rely on new chemistries and the findings of this research, including the microscopy techniques the researchers refined along the way, will apply to nearly any solution in those categories.

For its part, the Dionne lab has many directions it can go from here. The team could look at a variety of material compositions, or compare how the sizes and shapes of nanoparticles affect the way they work, and, soon, take advantage of new upgrades to their microscope to study light-driven reactions. At present, Hayee has moved on to experimenting with nanorods, which have more surface area for the ions to move through, promising potentially even faster kinetics.

Here’s a link to and a citation for the paper,

Direct visualization of hydrogen absorption dynamics in individual palladium nanoparticles by Tarun C. Narayan, Fariah Hayee, Andrea Baldi, Ai Leen Koh, Robert Sinclair, & Jennifer A. Dionne. Nature Communications 8, Article number: 14020 (2017) doi:10.1038/ncomms14020 Published online: 16 January 2017

This paper is open access.

‘Brewing up’ conductive inks for printable electronics

Scientists from Duke University aren’t exactly ‘brewing’ or ‘cooking up’ the inks but they do come close according to a Jan. 3, 2017 news item on ScienceDaily,

By suspending tiny metal nanoparticles in liquids, Duke University scientists are brewing up conductive ink-jet printer “inks” to print inexpensive, customizable circuit patterns on just about any surface.

A Jan. 3, 2017 Duke University news release (also on EurekAlert), which originated the news item, explains why this technique could lead to more accessible printed electronics,

Printed electronics, which are already being used on a wide scale in devices such as the anti-theft radio frequency identification (RFID) tags you might find on the back of new DVDs, currently have one major drawback: for the circuits to work, they first have to be heated to melt all the nanoparticles together into a single conductive wire, making it impossible to print circuits on inexpensive plastics or paper.

A new study by Duke researchers shows that tweaking the shape of the nanoparticles in the ink might just eliminate the need for heat.

By comparing the conductivity of films made from different shapes of silver nanostructures, the researchers found that electrons zip through films made of silver nanowires much easier than films made from other shapes, like nanospheres or microflakes. In fact, electrons flowed so easily through the nanowire films that they could function in printed circuits without the need to melt them all together.

“The nanowires had a 4,000 times higher conductivity than the more commonly used silver nanoparticles that you would find in printed antennas for RFID tags,” said Benjamin Wiley, assistant professor of chemistry at Duke. “So if you use nanowires, then you don’t have to heat the printed circuits up to such high temperature and you can use cheaper plastics or paper.”

“There is really nothing else I can think of besides these silver nanowires that you can just print and it’s simply conductive, without any post-processing,” Wiley added.

These types of printed electronics could have applications far beyond smart packaging; researchers envision using the technology to make solar cells, printed displays, LEDS, touchscreens, amplifiers, batteries and even some implantable bio-electronic devices. The results appeared online Dec. 16 [2016] in ACS Applied Materials and Interfaces.

Silver has become a go-to material for making printed electronics, Wiley said, and a number of studies have recently appeared measuring the conductivity of films with different shapes of silver nanostructures. However, experimental variations make direct comparisons between the shapes difficult, and few reports have linked the conductivity of the films to the total mass of silver used, an important factor when working with a costly material.

“We wanted to eliminate any extra materials from the inks and simply hone in on the amount of silver in the films and the contacts between the nanostructures as the only source of variability,” said Ian Stewart, a recent graduate student in Wiley’s lab and first author on the ACS paper.

Stewart used known recipes to cook up silver nanostructures with different shapes, including nanoparticles, microflakes, and short and long nanowires, and mixed these nanostructures with distilled water to make simple “inks.” He then invented a quick and easy way to make thin films using equipment available in just about any lab — glass slides and double-sided tape.

“We used a hole punch to cut out wells from double-sided tape and stuck these to glass slides,” Stewart said. By adding a precise volume of ink into each tape “well” and then heating the wells — either to relatively low temperature to simply evaporate the water or to higher temperatures to begin melting the structures together — he created a variety of films to test.

The team say they weren’t surprised that the long nanowire films had the highest conductivity. Electrons usually flow easily through individual nanostructures but get stuck when they have to jump from one structure to the next, Wiley explained, and long nanowires greatly reduce the number of times the electrons have to make this “jump”.

But they were surprised at just how drastic the change was. “The resistivity of the long silver nanowire films is several orders of magnitude lower than silver nanoparticles and only 10 times greater than pure silver,” Stewart said.

The team is now experimenting with using aerosol jets to print silver nanowire inks in usable circuits. Wiley says they also want to explore whether silver-coated copper nanowires, which are significantly cheaper to produce than pure silver nanowires, will give the same effect.

Here’s a link to and a citation for the paper,

Effect of Morphology on the Electrical Resistivity of Silver Nanostructure Films by Ian E. Stewart, Myung Jun Kim, and Benjamin J. Wiley. ACS Appl. Mater. Interfaces, Article ASAP
DOI: 10.1021/acsami.6b12289 Publication Date (Web): December 16, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall but there is an image of the silver nanowires, which is not exactly compensation but is interesting,

Caption: Duke University chemists have found that silver nanowire films like these conduct electricity well enough to form functioning circuits without applying high temperatures, enabling printable electronics on heat-sensitive materials like paper or plastic.
Credit: Ian Stewart and Benjamin Wiley

Drip dry housing

This piece on new construction materials does have a nanotechnology aspect although it’s not made clear exactly how nanotechnology plays a role.

From a Dec. 28, 2016 news item on phys.org (Note: A link has been removed),

The construction industry is preparing to use textiles from the clothing and footwear industries. Gore-Tex-like membranes, which are usually found in weather-proof jackets and trekking shoes, are now being studied to build breathable, water-resistant walls. Tyvek is one such synthetic textile being used as a “raincoat” for homes.

You can find out more about Tyvek here.on the Dupont website.

A Dec. 21, 2016 press release by Chiara Cecchi for Youris ((European Research Media Center), which originated the news item, proceeds with more about textile-type construction materials,

Camping tents, which have been used for ages to protect against wind, ultra-violet rays and rain, have also inspired the modern construction industry, or “buildtech sector”. This new field of research focuses on the different fibres (animal-based such as wool or silk, plant-based such as linen and cotton and synthetic such as polyester and rayon) in order to develop technical or high-performance materials, thus improving the quality of construction, especially for buildings, dams, bridges, tunnels and roads. This is due to the fibres’ mechanical properties, such as lightness, strength, and also resistance to many factors like creep, deterioration by chemicals and pollutants in the air or rain.

“Textiles play an important role in the modernisation of infrastructure and in sustainable buildings”, explains Andrea Bassi, professor at the Department of Civil and Environmental Engineering (DICA), Politecnico of Milan, “Nylon and fiberglass are mixed with traditional fibres to control thermal and acoustic insulation in walls, façades and roofs. Technological innovation in materials, which includes nanotechnologies [emphasis mine] combined with traditional textiles used in clothes, enables buildings and other constructions to be designed using textiles containing steel polyvinyl chloride (PVC) or ethylene tetrafluoroethylene (ETFE). This gives the materials new antibacterial, antifungal and antimycotic properties in addition to being antistatic, sound-absorbing and water-resistant”.

Rooflys is another example. In this case, coated black woven textiles are placed under the roof to protect roof insulation from mould. These building textiles have also been tested for fire resistance, nail sealability, water and vapour impermeability, wind and UV resistance.

Photo: Production line at the co-operative enterprise CAVAC Biomatériaux, France. Natural fibres processed into a continuous mat (biofib) – Martin Ansell, BRE CICM, University of Bath, UK

In Spain three researchers from the Technical University of Madrid (UPM) have developed a new panel made with textile waste. They claim that it can significantly enhance both the thermal and acoustic conditions of buildings, while reducing greenhouse gas emissions and the energy impact associated with the development of construction materials.

Besides textiles, innovative natural fibre composite materials are a parallel field of the research on insulators that can preserve indoor air quality. These bio-based materials, such as straw and hemp, can reduce the incidence of mould growth because they breathe. The breathability of materials refers to their ability to absorb and desorb moisture naturally”, says expert Finlay White from Modcell, who contributed to the construction of what they claim are the world’s first commercially available straw houses, “For example, highly insulated buildings with poor ventilation can build-up high levels of moisture in the air. If the moisture meets a cool surface it will condensate and producing mould, unless it is managed. Bio-based materials have the means to absorb moisture so that the risk of condensation is reduced, preventing the potential for mould growth”.

The Bristol-based green technology firm [Modcell] is collaborating with the European Isobio project, which is testing bio-based insulators which perform 20% better than conventional materials. “This would lead to a 5% total energy reduction over the lifecycle of a building”, explains Martin Ansell, from BRE Centre for Innovative Construction Materials (BRE CICM), University of Bath, UK, another partner of the project.

“Costs would also be reduced. We are evaluating the thermal and hygroscopic properties of a range of plant-derived by-products including hemp, jute, rape and straw fibres plus corn cob residues. Advanced sol-gel coatings are being deposited on these fibres to optimise these properties in order to produce highly insulating and breathable construction materials”, Ansell concludes.

You can find Modcell here.

Here’s another image, which I believe is a closeup of the processed fibre shown in the above,

Production line at the co-operative enterprise CAVAC Biomatériaux, France. Natural fibres processed into a continuous mat (biofib) – Martin Ansell, BRE CICM, University of Bath, UK [Note: This caption appears to be a copy of the caption for the previous image]

Environmentally sustainable electromobility

Researchers at the Norwegian University of Science and Technology pose an interesting question in a Dec. 8, 2016 news item on Nanowerk,

Does it really help to drive an electric car if the electricity you use to charge the batteries come from a coal mine in Germany, or if the batteries were manufactured in China using coal?

Researchers at the Norwegian University of Science and Technology’s Industrial Ecology Programme have looked at all of the environmental costs of electric vehicles to determine the cradle-to-grave environmental footprint of building and operating these vehicles.

Increasingly, researchers are examining not just immediate environmental impacts but the impact a product has throughout its life cycle as this Dec. 8, 2016 Norwegian University of Science and Technology press release on EurekAlert notes,

In the 6 December [2016] issue of Nature Nanotechnology, the researchers report on a model that can help guide developers as they consider new nanomaterials for batteries or fuel cells. The goal is to create the most environmentally sustainable vehicle fleet possible, which is no small challenge given that there are already an estimated 1 billion cars and light trucks on the world’s roads, a number that is expected to double by 2035.

With this in mind, the researchers created an environmental life-cycle screening framework that looked at the environmental and other impacts of extraction, refining, synthesis, performance, durability and recyclablility of materials.

This allowed the researchers to evaluate the most promising nanomaterials for lithium-ion batteries (LIB) and proton exchange membrane hydrogen fuel cells (PEMFC) as power sources for electric vehicles. “Our analysis of the current situation clearly outlines the challenge,” the researchers wrote. “The materials with the best potential environmental profiles during the material extraction and production phase…. often present environmental disadvantages during their use phase… and vice versa.”

The hope is that by identifying all the environmental costs of different materials used to build electric cars, designers and engineers can “make the right design trade-offs that optimize LIB and PEMFC nanomaterials for EV usage towards mitigating climate change,” the authors wrote.

They encouraged material scientists and those who conduct life-cycle assessments to work together so that electric cars can be a key contributor to mitigating the effects of transportation on climate change.

Here’s a link to and a citation for the paper,

Nanotechnology for environmentally sustainable electromobility by Linda Ager-Wick Ellingsen, Christine Roxanne Hung, Guillaume Majeau-Bettez, Bhawna Singh, Zhongwei Chen, M. Stanley Whittingham, & Anders Hammer Strømman. Nature Nanotechnology 11, 1039–1051 (2016)  doi:10.1038/nnano.2016.237 Published online 06 December 2016 Corrected online 14 December 2016

This paper is behind a paywall.

Seawater batteries to replace lithium-ion batteries?

Replacing lithium-ion batteries with seawater batteries is a little more complicated than going out to scoop a little seawater and returning home to cook up a battery according to a Dec. 7, 2016 American Chemical Society news release (also on EurkeAlert),

With the ubiquity of lithium-ion batteries in smartphones and other rechargeable devices, it’s hard to imagine replacing them. But the rising price of lithium has spurred a search for alternatives. One up-and-coming battery technology uses abundant, readily available seawater. Now, making this option viable is one step closer with a new report on a sodium-air, seawater battery. The study appears in the journal ACS Applied Materials & Interfaces.

Sodium-air — or sodium-oxygen — batteries are considered one of the most promising, and cost-effective alternatives to today’s lithium-ion standby. But some challenges remain before they can become a commercial reality. Soo Min Hwang, Youngsik Kim and colleagues have been tackling these challenges, using seawater as the catholyte — an electrolyte and cathode combined. In batteries, the electrolyte is the component that allows an electrical charge to flow between the cathode and anode. A constant flow of seawater into and out of the battery provides the sodium ions and water responsible for producing a charge. The reactions have been sluggish, however, so the researchers wanted to find a way to speed them up.

For their new battery, the team prepared a catalyst using porous cobalt manganese oxide nanoparticles. The pores create a large surface area for encouraging the electrochemical reactions needed to produce a charge. A hard carbon electrode served as the anode. The resulting battery performed efficiently over 100 cycles with an average discharge voltage of about 2.7 volts. This doesn’t yet measure up to a lithium-ion cell, which can reach 3.6 to 4.0 volts, but the advance is getting close to bridging the gap, the researchers say.

Here’s a link to and a citation for the paper,

A Metal–Organic Framework Derived Porous Cobalt Manganese Oxide Bifunctional Electrocatalyst for Hybrid Na–Air/Seawater Batteries by Mari Abirami, Soo Min Hwang, Juchan Yang, Sirugaloor Thangavel Senthilkumar, Junsoo Kim, Woo-Seok Go, Baskar Senthilkumar, Hyun-Kon Song, and Youngsik Kim. ACS Appl. Mater. Interfaces, 2016, 8 (48), pp 32778–32787
DOI: 10.1021/acsami.6b10082 Publication Date (Web): November 14, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall.

Soft contact lenses key to supercapacitor breaththrough

It seems like pretty exciting news for anyone following the supercapacitor story but they are being awfully cagey about it all in a Dec. 6, 2016 news item on Nanowerk,

Ground-breaking research from the University of Surrey and Augmented Optics Ltd., in collaboration with the University of Bristol, has developed potentially transformational technology which could revolutionise the capabilities of appliances that have previously relied on battery power to work.

This development by Augmented Optics Ltd., could translate into very high energy density super-capacitors making it possible to recharge your mobile phone, laptop or other mobile devices in just a few seconds.

The technology could have a seismic impact across a number of industries, including transport, aerospace, energy generation, and household applications such as mobile phones, flat screen electronic devices, and biosensors. It could also revolutionise electric cars, allowing the possibility for them to recharge as quickly as it takes for a regular non-electric car to refuel with petrol – a process that currently takes approximately 6-8 hours to recharge. Imagine, instead of an electric car being limited to a drive from London to Brighton, the new technology could allow the electric car to travel from London to Edinburgh without the need to recharge, but when it did recharge for this operation to take just a few minutes to perform.

I imagine the reason for the caginess has to do with the efforts to commercialize the technology. In any event, here’s a little more from a Dec. 5, 2016 University of Surrey press release by Ashley Lovell,

Supercapacitor buses are already being used in China, but they have a very limited range whereas this technology could allow them to travel a lot further between recharges. Instead of recharging every 2-3 stops this technology could mean they only need to recharge every 20-30 stops and that will only take a few seconds.

Elon Musk, of Tesla and SpaceX, has previously stated his belief that supercapacitors are likely to be the technology for future electric air transportation. We believe that the present scientific advance could make that vision a reality.

The technology was adapted from the principles used to make soft contact lenses, which Dr Donald Highgate (of Augmented Optics, and an alumnus of the University of Surrey) developed following his postgraduate studies at Surrey 40 years ago. Supercapacitors, an alternative power source to batteries, store energy using electrodes and electrolytes and both charge and deliver energy quickly, unlike conventional batteries which do so in a much slower, more sustained way. Supercapacitors have the ability to charge and discharge rapidly over very large numbers of cycles. However, because of their poor energy density per kilogramme (approximately just one twentieth of existing battery technology), they have, until now, been unable to compete with conventional battery energy storage in many applications.

Dr Brendan Howlin of the University of Surrey, explained: “There is a global search for new energy storage technology and this new ultra capacity supercapacitor has the potential to open the door to unimaginably exciting developments.”

The ground-breaking research programme was conducted by researchers at the University of Surrey’s Department of Chemistry where the project was initiated by Dr Donald Highgate of Augmented Optics Ltd. The research team was co-led by the Principal Investigators Dr Ian Hamerton and Dr Brendan Howlin. Dr Hamerton continues to collaborate on the project in his new post at the University of Bristol, where the electrochemical testing to trial the research findings was carried out by fellow University of Bristol academic – David Fermin, Professor of Electrochemistry in the School of Chemistry.

Dr Ian Hamerton, Reader in Polymers and Composite Materials from the Department of Aerospace Engineering, University of Bristol said: “While this research has potentially opened the route to very high density supercapacitors, these *polymers have many other possible uses in which tough, flexible conducting materials are desirable, including bioelectronics, sensors, wearable electronics, and advanced optics. We believe that this is an extremely exciting and potentially game changing development.”

*the materials are based on large organic molecules composed of many repeated sub-units and bonded together to form a 3-dimensional network.

Jim Heathcote, Chief Executive of both Augmented Optics Ltd and Supercapacitor Materials Ltd, said: “It is a privilege to work with the teams from the University of Surrey and the University of Bristol. The test results from the new polymers suggest that extremely high energy density supercapacitors could be constructed in the very new future. We are now actively seeking commercial partners [emphasis mine] in order to supply our polymers and offer assistance to build these ultra high energy density storage devices.”

I was not able to find a website for Augmented Optics but there is one for SuperCapacitor Materials here.

Trying to push past the 30% energy conversion ceiling for solar cells

A Nov. 21, 2016 news item on Nanowerk describes some work in Japan which suggests that more energy conversion for solar cells is possible,

Solar energy could provide a renewable, sustainable source of power for our daily needs. However, even the most state-of-the-art solar cells struggle to achieve energy conversion efficiency of higher than 30%. While current solar-powered water heaters fare better in terms of energy efficiency, there are still improvements to be made if the systems are to be used more widely.

One potential candidate for inclusion in solar water heaters is “nanofluid,” that is, a liquid containing specially-designed nanoparticles that are capable of absorbing sunlight and transforming it into thermal energy in order to heat water directly.

A Nov. 20, 2016 (Japan) International Center for Materials Nanoarchitectonics (WPI-MANA) press release (received via email), explains further,

Nanoparticle Boost for Solar-powered Water Heating

Now, Satoshi Ishii and his co-workers at the International Center for Materials Nanoarchitectonics (WPI-MANA) and the Japan Science and Technology Agency have developed a new nanofluid containing titanium nitride (TiN) nanoparticles, which demonstrates high efficiency in heating water and generating water vapor.

The team analytically studied the optical absorption efficiency of a TiN nanoparticle and found that it has a broad and strong absorption peak thanks to lossy plasmonic resonances. Surprisingly, the sunlight absorption efficiency of a TiN nanoparticle outperforms that of a carbon nanoparticle and a gold nanoparticle.

They then exposed each nanofluid to sunlight and measured its ability to heat pure water. The TiN nanofluid had the highest water heating properties, stemming from the resonant sunlight absorption. It also generated more vapor than its carbon‒based counterpart. The efficiency of the TiN nanofluid reached nearly 90 %. Crucially, the TiN particles were not consumed during the process, meaning a TiN‒based heating system could essentially be self‒sustaining over time.

TiN nanofluids show great promise in solar heat applications, with high potential for use in everyday appliances such as showers. The new design could even contribute to methods for decontaminating water through vaporization.

90% is a very exiting conversion rate. Of course, now they need to make sure they can achieve those results consistently, get those results outside the laboratory, and scale up to industrial standards.

Here’s a link to and a citation for the paper,

Titanium Nitride Nanoparticles as Plasmonic Solar Heat Transducers by Satoshi Ishii, Ramu Pasupathi Sugavaneshwar, and Tadaaki Nagao. J. Phys. Chem. C, 2016, 120 (4), pp 2343–2348 DOI: 10.1021/acs.jpcc.5b09604 Publication Date (Web): December 21, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall and it’s almost a year old. I wonder what occasioned the push for publicity.

Offering privacy and light control via smart windows

There have been quite a few ‘smart’ window stories here on this blog but this one is the first to feature a privacy option. From a Nov. 17, 2016 news item on Nanowerk,

Smart windows get darker to filter out the sun’s rays on bright days, and turn clear on cloudy days to let more light in. This feature can help control indoor temperatures and offers some privacy without resorting to aids such as mini-blinds.

Now scientists report a new development in this growing niche: solar smart windows that can turn opaque on demand and even power other devices. …

A Nov. 17, 2016 American Chemical Society (ACS) news release, which originated the news item, goes on to explain the work,

Most existing solar-powered smart windows are designed to respond automatically to changing conditions, such as light or heat. But this means that on cool or cloudy days, consumers can’t flip a switch and tint the windows for privacy. Also, these devices often operate on a mere fraction of the light energy they are exposed to while the rest gets absorbed by the windows. This heats them up, which can add warmth to a room that the windows are supposed to help keep cool. Jeremy Munday and colleagues wanted to address these limitations.

The researchers created a new smart window by sandwiching a polymer matrix containing microdroplets of liquid crystal materials, and an amorphous silicon layer — the type often used in solar cells — between two glass panes. When the window is “off,” the liquid crystals scatter light, making the glass opaque. The silicon layer absorbs the light and provides the low power needed to align the crystals so light can pass through and make the window transparent when the window is turned “on” by the user. The extra energy that doesn’t go toward operating the window is harvested and could be redirected to power other devices, such as lights, TVs or smartphones, the researchers say.

For anyone who finds reading text a bit onerous, there’s this video,

Here’s a link to and a citation for the paper,

Electrically Controllable Light Trapping for Self-Powered Switchable Solar Windows by Joseph Murray, Dakang Ma, and Jeremy N. Munday. ACS Photonics, Article ASAP DOI: 10.1021/acsphotonics.6b00518 Publication Date (Web): October 26, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall.