Category Archives: energy

Canadian researchers harvest energy from chewing

Who knew that jaw movements have proved to be amongst the most promising activities for energy-harvesting? Apparently, scientists know and are coming up with ways to enjoy the harvest. From a Sept. 16, 2014 news item on Nanowerk,

A chin strap that can harvest energy from jaw movements has been created by a group of researchers in Canada.

It is hoped that the device can generate electricity from eating, chewing and talking, and power a number of small-scale implantable or wearable electronic devices, such as hearing aids, cochlear implants, electronic hearing protectors and communication devices.

An Institute of Physics (IOP) Sept. 16, 2014 news release (also on EurekAlert), which  generated the news item, explains just why jaw movements are so exciting and how the researchers went about ‘harvesting’,

Jaw movements have proved to be one of the most promising candidates for generating electricity from human body movements, with researchers estimating that an average of around 7 mW of power could be generated from chewing during meals alone.

To harvest this energy, the study’s researchers, from Sonomax-ÉTS Industrial Research Chair in In-ear Technologies (CRITIAS) at École de technologie supérieure (ÉTS) in Montreal, Canada, created a chinstrap made from piezoelectric fibre composites (PFC).

PFC is a type of piezoelectric smart material that consists of integrated electrodes and an adhesive polymer matrix. The material is able to produce an electric charge when it stretches and is subjected to mechanical stress.

In their study, the researchers created an energy-harvesting chinstrap made from a single layer of PFC and attached it to a pair of earmuffs using a pair of elastic side straps. To ensure maximum performance, the chinstrap was fitted snugly to the user, so when the user’s jaw moved it caused the strap to stretch.

To test the performance of the device, the subject was asked to chew gum for 60 seconds while wearing the device; at the same time the researchers recorded a number of different parameters.

The maximum amount of power that could be harvested from the jaw movements was around 18 µW, but taking into account the optimum set-up for the head-mounted device, the power output was around 10 µW.

Co-author of the study Aidin Delnavaz said: “Given that the average power available from chewing is around 7 mW, we still have a long way to go before we perfect the performance of the device.

“The power level we achieved is hardly sufficient for powering electrical devices at the moment; however, we can multiply the power output by adding more PFC layers to the chinstrap. For example, 20 PFC layers, with a total thickness of 6 mm, would be able to power a 200 µW intelligent hearing protector.”

One additional motivation for pursuing this area of research is the desire to curb the current dependency on batteries, which are not only expensive to replace but also extremely damaging to the environment if they are not disposed of properly.

“The only expensive part of the energy-harvesting device is the single PFC layer, which costs around $20. Considering the price and short lifetime of batteries, we estimate that a self-powered hearing protector based on the proposed chinstrap energy-harvesting device will start to pay back the investment after three years of use,” continued Delnavaz.

“Additionally, the device could substantially decrease the environmental impact of batteries and bring more comfort to users.

“We will now look at ways to increase the number of piezoelectric elements in the chinstrap to supply the power that small electronic devices demand, and also develop an appropriate power management circuit so that a tiny, rechargeable battery can be integrated into the device.”

Here’s a look at the ‘smart chinstrap’,

Caption: This is the experimental set up of an energy harvesting chin strap. Credit: Smart Materials and Structures/IOP Publishing

Caption: This is the experimental set up of an energy harvesting chin strap.
Credit: Smart Materials and Structures/IOP Publishing

I don’t see anyone rushing to get a chinstrap soon. Hopefully they’ll find a way to address some of the design issues. In the meantime, here’s a link to and a citation for the paper,

Flexible piezoelectric energy harvesting from jaw movements by Aidin Delnavaz and Jérémie Voix. 2014 Smart Mater. Struct. 23 105020 doi:10.1088/0964-1726/23/10/105020

This is an open access paper.

Buckydiamondoids steer electron flow

One doesn’t usually think about buckyballs (Buckminsterfullerenes) and diamondoids as being together in one molecule but that has not stopped scientists from trying to join them and, in this case, successfully. From a Sept. 9, 2014 news item on ScienceDaily,

Scientists have married two unconventional forms of carbon — one shaped like a soccer ball, the other a tiny diamond — to make a molecule that conducts electricity in only one direction. This tiny electronic component, known as a rectifier, could play a key role in shrinking chip components down to the size of molecules to enable faster, more powerful devices.

Here’s an illustration the scientists have provided,

Illustration of a buckydiamondoid molecule under a scanning tunneling microscope (STM). In this study the STM made images of the buckydiamondoids and probed their electronic properties.

Illustration of a buckydiamondoid molecule under a scanning tunneling microscope (STM). In this study the STM made images of the buckydiamondoids and probed their electronic properties.

A Sept. 9, 2014 Stanford University news release by Glenda Chui (also on EurekAlert), which originated the news item, provides some information about this piece of international research along with background information on buckyballs and diamondoids (Note: Links have been removed),

“We wanted to see what new, emergent properties might come out when you put these two ingredients together to create a ‘buckydiamondoid,’” said Hari Manoharan of the Stanford Institute for Materials and Energy Sciences (SIMES) at the U.S. Department of Energy’s SLAC National Accelerator Laboratory. “What we got was basically a one-way valve for conducting electricity – clearly more than the sum of its parts.”

The research team, which included scientists from Stanford University, Belgium, Germany and Ukraine, reported its results Sept. 9 in Nature Communications.

Many electronic circuits have three basic components: a material that conducts electrons; rectifiers, which commonly take the form of diodes, to steer that flow in a single direction; and transistors to switch the flow on and off. Scientists combined two offbeat ingredients – buckyballs and diamondoids – to create the new diode-like component.

Buckyballs – short for buckminsterfullerenes – are hollow carbon spheres whose 1985 discovery earned three scientists a Nobel Prize in chemistry. Diamondoids are tiny linked cages of carbon joined, or bonded, as they are in diamonds, with hydrogen atoms linked to the surface, but weighing less than a billionth of a billionth of a carat. Both are subjects of a lot of research aimed at understanding their properties and finding ways to use them.

In 2007, a team led by researchers from SLAC and Stanford discovered that a single layer of diamondoids on a metal surface can emit and focus electrons into a tiny beam. Manoharan and his colleagues wondered: What would happen if they paired an electron-emitting diamondoid with another molecule that likes to grab electrons? Buckyballs are just that sort of electron-grabbing molecule.

Details are then provided about this specific piece of research (from the Stanford news release),

For this study, diamondoids were produced in the SLAC laboratory of SIMES researchers Jeremy Dahl and Robert Carlson, who are world experts in extracting the tiny diamonds from petroleum. The diamondoids were then shipped to Germany, where chemists at Justus-Liebig University figured out how to attach them to buckyballs.

The resulting buckydiamondoids, which are just a few nanometers long, were tested in SIMES laboratories at Stanford. A team led by graduate student Jason Randel and postdoctoral researcher Francis Niestemski used a scanning tunneling microscope to make images of the hybrid molecules and measure their electronic behavior. They discovered that the hybrid is an excellent rectifier: The electrical current flowing through the molecule was up to 50 times stronger in one direction, from electron-spitting diamondoid to electron-catching buckyball, than in the opposite direction. This is something neither component can do on its own.

While this is not the first molecular rectifier ever invented, it’s the first one made from just carbon and hydrogen, a simplicity researchers find appealing, said Manoharan, who is an associate professor of physics at Stanford. The next step, he said, is to see if transistors can be constructed from the same basic ingredients.

“Buckyballs are easy to make – they can be isolated from soot – and the type of diamondoid we used here, which consists of two tiny cages, can be purchased commercially,” he said. “And now that our colleagues in Germany have figured out how to bind them together, others can follow the recipe. So while our research was aimed at gaining fundamental insights about a novel hybrid molecule, it could lead to advances that help make molecular electronics a reality.”

Other research collaborators came from the Catholic University of Louvain in Belgium and Kiev Polytechnic Institute in Ukraine. The primary funding for the work came from U.S. the Department of Energy Office of Science (Basic Energy Sciences, Materials Sciences and Engineering Divisions).

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

Unconventional molecule-resolved current rectification in diamondoid–fullerene hybrids by Jason C. Randel, Francis C. Niestemski,    Andrés R. Botello-Mendez, Warren Mar, Georges Ndabashimiye, Sorin Melinte, Jeremy E. P. Dahl, Robert M. K. Carlson, Ekaterina D. Butova, Andrey A. Fokin, Peter R. Schreiner, Jean-Christophe Charlier & Hari C. Manoharan. Nature Communications 5, Article number: 4877 doi:10.1038/ncomms5877 Published 09 September 2014

This paper is open access. The scientists provided not only a standard illustration but a pretty picture of the buckydiamondoid,

Caption: An international team led by researchers at SLAC National Accelerator Laboratory and Stanford University joined two offbeat carbon molecules -- diamondoids, the square cages at left, and buckyballs, the soccer-ball shapes at right -- to create "buckydiamondoids," center. These hybrid molecules function as rectifiers, conducting electrons in only one direction, and could help pave the way to molecular electronic devices. Credit: Manoharan Lab/Stanford University

Caption: An international team led by researchers at SLAC National Accelerator Laboratory and Stanford University joined two offbeat carbon molecules — diamondoids, the square cages at left, and buckyballs, the soccer-ball shapes at right — to create “buckydiamondoids,” center. These hybrid molecules function as rectifiers, conducting electrons in only one direction, and could help pave the way to molecular electronic devices.
Credit: Manoharan Lab/Stanford University

Tibetan Buddhist singing bowls inspire more efficient solar cells

There’s no mention as to whether or not Dr Niraj Lal practices any form of meditation or how he came across Tibetan Buddhist singing bowls but somehow he was inspired by them when studying for his PhD at Cambridge University (UK). From a Sept. 8, 2014 news item by Niall Byrne for physorg.com,

The shape of a centuries-old Buddhist singing bowl has inspired a Canberra scientist to re-think the way that solar cells are designed to maximize their efficiency.

Dr Niraj Lal, of the Australian National University,  found during his PhD at the University of Cambridge, that small nano-sized versions of Buddhist singing bowls resonate with light in the same way as they do with sound, and he’s applied this shape to solar cells to increase their ability to capture more light and convert it into electricity.

A Sept. ?, 2014 news release from Australian science communication company, Science in Public, fills in a few more details without any mention of Lal’s meditation practices, should he have any,

“Current standard solar panels lose a large amount of light-energy as it hits the surface, making the panels’ generation of electricity inefficient,” says Niraj. “But if the cells are singing bowl-shaped, then the light bounces around inside the cell for longer”.

Normally used in meditation, music, and relaxation, Buddhist singing bowls make a continuous harmonic ringing sound when the rim of the metal bowl is vibrated with a wooden or other utensil.

During his PhD, Niraj discovered that his ‘nanobowls’ manipulated light by creating a ‘plasmonic’ resonance, which quadrupled the laboratory solar cell’s efficiency compared to a similarly made flat solar cell.

Now, Niraj and his team aim to change all that by applying his singing-bowl discovery to tandem solar cells: a technology that has previously been limited to aerospace applications.

In research which will be published in the November issue of IEEE Journal of Photonics, Niraj and his colleagues have shown that by layering two different types of solar panels on top of each other in tandem, the efficiency of flat rooftop solar panels can achieve 30 per cent—currently, laboratory silicon solar panels convert only 25 per cent of light into electricity, while commercial varieties convert closer to 20 per cent.

The tandem cell design works by absorbing a sunlight more effectively —each cell is made from a different material so that it can ‘see’ a different light wavelength.

“To a silicon solar cell, a rainbow just looks like a big bit of red in the sky—they don’t ‘see’ the blue, green or UV light—they convert all light to electricity as if it was red ,” says Niraj. “But when we put a second cell on top, which ‘sees’ the blue part of light, but allows the red to pass through to the ‘red-seeing’ cell below, we can reach a combined efficiency of more than 30 percent.”

Niraj and a team at ANU are now looking at ways to super-charge the tandem cell design by applying the Buddhist singing bowl shape to further increase efficiency.

“If we can make a solar cell that ‘sees’ more colours and  keeps the right light in the right layers, then we could increase efficiency even further,” says Niraj.

“Every extra percent in efficiency saves you thousands of dollars over the lifetime of the panel,” says Niraj. “Current roof-top solar panels have been steadily increasing in efficiency, which has been a big driver of the fourfold drop in the price for these panels over the last five years.”

More importantly, says Niraj, greater efficiency will allow solar technology to compete with fossil fuels and meet the challenges of climate change and access.

“Electricity is also one of the most enabling technologies we have ever seen, and linking people in rural areas around the world to electricity is one of the most powerful things we can do.”

At the end of the Science in Public news release there’s mention of a science communication competition,

Niraj was a 2014 national finalist of FameLab Australia. FameLab is a global science communication competition for early-career scientists. His work is supported by the Australian Research Council and ARENA – the Australian Renewable Energy Agency.

About FameLab

In 2014, the British Council and Fresh Science have joined forces to bring FameLab to Australia.

FameLab Australia will offer specialist science media training and, ultimately, the chance for early-career researchers to pitch their research at the FameLab International Grand Final in the UK at The Times Cheltenham Science Festival from 3 to 5 June 2014.

FameLab is an international communication competition for scientists, including engineers and mathematicians. Designed to inspire and motivate young researchers to actively engage with the public and with potential stakeholders, FameLab is all about finding the best new voices of science and engineering across the world.

Founded in 2005 by The Times Cheltenham Science Festival, FameLab, working in partnership with the British Council, has already seen more than 5,000 young scientists and engineers participate in over 23 different countries — from Hong Kong to South Africa, USA to Egypt.

Now, FameLab comes to Australia in a landmark collaboration with the British Council and Fresh Science — Australia’s very own science communication competition.

For more information about FameLab Australia, head to www.famelab.org.au

You can find out more about Australia’s Fresh Science here.

Getting back to Dr. Lal, here’s a video he made about his work and where he demonstrates a Tibetan Buddhist singing bowl (this is a very low tech video and the sound quality isn’t great),

Here’s a link to and a citation for Lal’s most recent paper,

Optics and Light Trapping for Tandem Solar Cells on Silicon by Lal, N.N.; White, T.P. ; and Catchpole, K.R. Photovoltaics, IEEE Journal of  (Volume:PP ,  Issue: 99) Page(s): 1 – 7 ISSN : 2156-3381 DOI: 10.1109/JPHOTOV.2014.2342491 Published online 19 August 2014

The paper is behind a paywall but there is open access to Lal’s 2012 University of Cambridge PhD thesis on his approach,

Enhancing solar cells with plasmonic nanovoids by Lal, Niraj Narsey
URI: http://www.dspace.cam.ac.uk/handle/1810/243864 Date:2012-07-03

Hap;y reading!

A tattoo that’s a biobattery and a sensor?

It’s going to be an American Chemical Society (ACS) 248th meeting kind of week as yet another interesting piece of scientific research is bruited (spread) about the internet. This time it’s all about sweat, exercise, and biobatteries. From an Aug. 13, 2014 news item on Nanowerk,

In the future, working up a sweat by exercising may not only be good for your health, but it could also power your small electronic devices. Researchers will report today that they have designed a sensor in the form of a temporary tattoo that can both monitor a person’s progress during exercise and produce power from their perspiration.

An Aug. 13, 2014 ACS news release on EurekAlert, which originated the news item, describes the inspiration (as opposed to perspiration) for this technology,

The device works by detecting and responding to lactate, which is naturally present in sweat. “Lactate is a very important indicator of how you are doing during exercise,” says Wenzhao Jia, Ph.D.

In general, the more intense the exercise, the more lactate the body produces. During strenuous physical activity, the body needs to generate more energy, so it activates a process called glycolysis. Glycolysis produces energy and lactate, the latter of which scientists can detect in the blood.

Professional athletes monitor their lactate levels during performance testing as a way to evaluate their fitness and training program. In addition, doctors measure lactate during exercise testing of patients for conditions marked by abnormally high lactate levels, such as heart or lung disease. Currently, lactate testing is inconvenient and intrusive because blood samples must be collected from the person at different times during the exercise regime and then analyzed.

The news release goes on to describe the research process which resulted in a temporary tattoo that could be used to power small scale electronics,

Jia, a postdoctoral student in the lab of Joseph Wang, D.Sc., at the University of California San Diego, and her colleagues developed a faster, easier and more comfortable way to measure lactate during exercise. They imprinted a flexible lactate sensor onto temporary tattoo paper. The sensor contained an enzyme that strips electrons from lactate, generating a weak electrical current. The researchers applied the tattoo to the upper arms of 10 healthy volunteers. Then the team measured the electrical current produced as the volunteers exercised at increasing resistance levels on a stationary bicycle for 30 minutes. In this way, they could continuously monitor sweat lactate levels over time and with changes in exercise intensity.

The team then went a step further, building on these findings to make a sweat-powered biobattery. Batteries produce energy by passing current, in the form of electrons, from an anode to a cathode. In this case, the anode contained the enzyme that removes electrons from lactate, and the cathode contained a molecule that accepts the electrons.

When 15 volunteers wore the tattoo biobatteries while exercising on a stationary bike, they produced different amounts of power. Interestingly, people who were less fit (exercising fewer than once a week) produced more power than those who were moderately fit (exercising one to three times per week). Enthusiasts who worked out more than three times per week produced the least amount of power. The researchers say that this is probably because the less-fit people became fatigued sooner, causing glycolysis to kick in earlier, forming more lactate. The maximum amount of energy produced by a person in the low-fitness group was 70 microWatts per cm2 of skin.

“The current produced is not that high, but we are working on enhancing it so that eventually we could power some small electronic devices,” Jia says. “Right now, we can get a maximum of 70 microWatts per cm2, but our electrodes are only 2 by 3 millimeters in size and generate about 4 microWatts — a bit small to generate enough power to run a watch, for example, which requires at least 10 microWatts. So besides working to get higher power, we also need to leverage electronics to store the generated current and make it sufficient for these requirements.”

Biobatteries offer certain advantages over conventional batteries: They recharge more quickly, use renewable energy sources (in this case, sweat), and are safer because they do not explode or leak toxic chemicals.

“These represent the first examples of epidermal electrochemical biosensing and biofuel cells that could potentially be used for a wide range of future applications,” Wang says.

The ACS has made a video about this work available,

It seems to me this tattoo battery could be used as a self-powered monitoring device in a medical application for heart or lung disease.

Hemp as a substitute for graphene in supercapacitors

As a member of the Cannabis plant family, hemp has an undeserved reputation due to its cousin’s (marijuana) notoriety and consciousness-altering properties. Hemp is, by contrast, the Puritan in the family, associated by the knowledgeable with virtues of thrift and hard work.

An Aug. 12, 2014 news item on Nanowerk highlights a hemp/supercapacitor presentation at the 248th meeting of the American Chemical Society (ACS),

As hemp makes a comeback in the U.S. after a decades-long ban on its cultivation, scientists are reporting that fibers from the plant can pack as much energy and power as graphene, long-touted as the model material for supercapacitors. They’re presenting their research, which a Canadian start-up company is working on scaling up, at the 248th National Meeting & Exposition of the American Chemical Society (ACS), the world’s largest scientific society.

David Mitlin, Ph.D., explains that supercapacitors are energy storage devices that have huge potential to transform the way future electronics are powered. Unlike today’s rechargeable batteries, which sip up energy over several hours, supercapacitors can charge and discharge within seconds. But they normally can’t store nearly as much energy as batteries, an important property known as energy density. One approach researchers are taking to boost supercapacitors’ energy density is to design better electrodes. Mitlin’s team has figured out how to make them from certain hemp fibers — and they can hold as much energy as the current top contender: graphene.

An Aug. 12, 2014 ACS news release features David Mitlin, formerly of the University of Alberta (Canada) where this research took place,, Mitlin is now with now with Clarkson University in New York,

“Our device’s electrochemical performance is on par with or better than graphene-based devices,” Mitlin says. “The key advantage is that our electrodes are made from biowaste using a simple process, and therefore, are much cheaper than graphene.”

The race toward the ideal supercapacitor has largely focused on graphene — a strong, light material made of atom-thick layers of carbon, which when stacked, can be made into electrodes. Scientists are investigating how they can take advantage of graphene’s unique properties to build better solar cells, water filtration systems, touch-screen technology, as well as batteries and supercapacitors. The problem is it’s expensive.

Mitlin’s group decided to see if they could make graphene-like carbons from hemp bast fibers. The fibers come from the inner bark of the plant and often are discarded from Canada’s fast-growing industries that use hemp for clothing, construction materials and other products. …

His team found that if they heated the fibers for 24 hours at a little over 350 degrees Fahrenheit, and then blasted the resulting material with more intense heat, it would exfoliate into carbon nanosheets.

Mitlin’s team built their supercapacitors using the hemp-derived carbons as electrodes and an ionic liquid as the electrolyte. Fully assembled, the devices performed far better than commercial supercapacitors in both energy density and the range of temperatures over which they can work. The hemp-based devices yielded energy densities as high as 12 Watt-hours per kilogram, two to three times higher than commercial counterparts. They also operate over an impressive temperature range, from freezing to more than 200 degrees Fahrenheit.

“We’re past the proof-of-principle stage for the fully functional supercapacitor,” he says. “Now we’re gearing up for small-scale manufacturing.”

I have not been able to confirm the name for Mitlin’s startup but I think it’s called Alta Supercaps (Alta being an abbreviation for Alberta,, amongst other things, and supercaps for supercapacitors) as per the information about a new startup on the Mitlin Group webspace (scroll down to the July 2, 2013 news item) which can still be found on the University of Alberta website (as of Aug. 12, 2014).

For those who would like more technical details, there is this July 2013 article by Mark Crawford for the ASME (American Society of Mechanical Engineers); Note: A link has been removed.

Activated carbons, templated carbons, carbon nanofibers, carbon nanotubes, and graphene have all been intensively studied as materials for supercapacitor electrodes. High manufacturing costs is one issue—another is that the power characteristics of many of these carbons are limited. This is a result of high microporosity, which increases ion transport limitations.

“It is becoming well understood that the key to achieving high power in porous electrodes is to reduce the ion transport limitations” says Mitlin. “Nanomaterials based on graphene and their hybrids have emerged as a new class of promising high-rate electrode candidates—they are, however, too expensive to manufacture compared to activated carbons derived from pyrolysis of agricultural wastes, or from the coking operations.”

Biomass, which mainly contains cellulose and lignin by-products, is widely utilized as a feedstock for producing activated carbons. Mitlin decided to test hemp bast fiber’s unique cellular structure to see if it could produce graphene-like carbon nanosheets.

Hemp fiber waste was pressure-cooked (hydrothermal synthesis) at 180 °C for 24 hours. The resulting carbonized material was treated with potassium hydroxide and then heated to temperatures as high as 800 °C, resulting in the formation of uniquely structured nanosheets. Testing of this material revealed that it discharged 49 kW of power per kg of material—nearly triple what standard commercial electrodes supply, 17 kW/kg.

Mitlin and his team successfully synthesized two-dimensional, yet interconnected, carbon nanosheets with superior electrochemical storage properties comparable to those of state-of-the-art graphene-based electrodes. “We were able to achieve this by employing a biomass precursor with a unique structure—hemp bast fiber,” says Mitlin. “The resultant graphene-like nanosheets possess fundamentally different properties—such as pore size distribution, physical interconnectedness, and electrical conductivity—as compared to conventional biomass-derived activated carbons.”

This image from Wikimedia was used to illustrate the Crawford article,

Hemp bast fiber is a low-cost graphene-like nanomaterial. Image: Wikimedia Commons

Hemp bast fiber is a low-cost graphene-like nanomaterial. Image: Wikimedia Commons

It seems to me that over the last few months there have been more than the usual number of supercapacitor stories, which makes the race to create the one that will break through in the marketplace fascinating to observe.

Wearable solar panels with perovskite

There was a bit of a flutter online in late July 2014 about solar cell research and perovskite, a material that could replace silicon therefore making solar cells more affordable, which hopefully would lead to greater adoption of the technology. Happily, the publishers of the study seem to have reissued their news release (h/t Aug. 11, 2014 news item on Nanwerk).

From the Wiley online press release Nr. 29/2014,

Textile solar cells are an ideal power source for small electronic devices incorporated into clothing. In the journal Angewandte Chemie, Chinese scientists have now introduced novel solar cells in the form of fibers that can be woven into a textile. The flexible, coaxial cells are based on a perovskite material and carbon nanotubes; they stand out due to their excellent energy conversion efficiency of 3.3 % and their low production cost.

The dilemma for solar cells: they are either inexpensive and inefficient, or they have a reasonable efficiency and are very expensive. One solution may come from solar cells made of perovskite materials, which are less expensive than silicon and do not require any expensive additives. Perovskites are materials with a special crystal structure that is like that of perovskite, a calcium titanate. These structures are often semiconductors and absorb light relatively efficiently. Most importantly, they can move electrons excited by light for long distances within the crystal lattice before they return to their energetic ground state and take up a solid position – a property that is very important in solar cells.

A team led by Hisheng Peng at Fudan University in Shanghai has now developed perovskite solar cells in the form of flexible fibers that can be woven into electronic textiles. Their production process is relatively simple and inexpensive because it uses a solution-based process to build up the layers.

The anode is a fine stainless steel wire coated with a compact n-semiconducting titanium dioxide layer. A layer of porous nanocrystalline titanium dioxide is deposited on top of this. This provides a large surface area for the subsequent deposition of the perovskite material CH3NH3PbI3. This is followed by a layer made of a special organic material. Finally a transparent layer of aligned carbon nanotubes is continuously wound over the whole thing to act as the cathode. The resulting fiber is so fine and flexible that it can be woven into textiles.

The perovskite layer absorbs light, that excites electrons and sets them free, causing a charge separation between the electrons and the formally positively charged “holes” The electrons enter the conducting band of the compact titanium dioxide layer and move to the anode. The “holes” are captured by the organic layer. The large surface area and the high electrical conductivity of the carbon nanotube cathode aid in the rapid conduction of the charges with high photoelectric currents. The fiber solar cell can attain an energy conversion efficiency of 3.3 %, exceeding that of all previous coaxial fiber solar cells made with either dyes or polymers.

Here’s an image used in the press release illustrating the new fiber,

[downloaded from http://www.wiley-vch.de/vch/journals/2002/press/201429press.pdf]

[downloaded from http://www.wiley-vch.de/vch/journals/2002/press/201429press.pdf]

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

Integrating Perovskite Solar Cells into a Flexible Fiber by Longbin Qiu, Jue Deng, Xin Lu, Zhibin Yang, and Prof. Huisheng Peng. Angewandte Chemie International Edition DOI: 10.1002/anie.201404973 Article first published online: 22 JUL 2014

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

I found a second item about perovskite and solar cells in a May 16, 2014 article by Vicki Marshall for Chemistry World which discussed some research in the UK (Note: Links have been removed),

A lead-free and non-toxic alternative to current perovskite solar-cell technology has been reported by researchers in the UK: tin halide perovskite solar cells. They are also cheaper to manufacture than the silicon solar cells currently dominating the market.

Nakita Noel, part of Henry Snaith’s research team at the University of Oxford, describes how perovskite materials have caused a bit of a whirlwind since they came out in 2009: ‘Everybody that’s working in the solar community is looking to beat silicon.’ Despite the high efficiency of conventional crystalline silicon solar cells (around 20%), high production and installation costs decrease their economic feasibility and widespread use.

The challenge to find a cheaper alternative led to the development of perovskite-based solar cells, as organic–inorganic metal trihalide perovskites have both abundant and cheap starting materials. However, the presence of lead in some semiconductors could create toxicology issues in the future. As Noel puts it ‘every conference you present at somebody is bound to put up their hand and ask “What about the lead – isn’t this toxic?”’

Brian Hardin, co-founder of PLANT PV, US, and an expert in new materials for photovoltaic cells, says the study ‘should be considered a seminal work on alternative perovskites and is extremely valuable to the field as they look to better understand how changes in chemistry affect solar cell performance and stability.’

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

Lead-free organic–inorganic tin halide perovskites for photovoltaic applications by Nakita K. Noel, Samuel D. Stranks, Antonio Abate, Christian Wehrenfennig, Simone Guarnera, Amir-Abbas Haghighirad, Aditya Sadhana, Giles E. Eperon, Sandeep K. Pathak, Michael B. Johnston, Annamaria Petrozza, Laura M. Herza, and Henry J. Snaith. Energy Environ. Sci., 2014, Advance Article DOI: 10.1039/C4EE01076K First published online 01 May 2014

This article was open access until June 27, 2014 but now it is behind a paywall.

I notice there’s no mention of lead in the materials describing the research paper from the Chinese scientists. Perhaps they were working with lead-free materials.

Don’t throw that cigarette butt away—use it to store energy!

I’ve read the news release and briefly skimmed the research paper and cannot find any discussion of how these scientists got the idea to ‘recycle’ used cigarette butts for energy storage (supercapacitors) although the inspiration seems to have its roots in a desire to create better supercapacitors from recycled materials. From an Aug. 5, 2014 news item on ScienceDaily,

A group of scientists from South Korea have converted used-cigarette butts into a high-performing material that could be integrated into computers, handheld devices, electrical vehicles and wind turbines to store energy.

Presenting their findings today, 5 August 2014, in IOP Publishing’s journal Nanotechnology, the researchers have demonstrated the material’s superior performance compared to commercially available carbon, graphene and carbon nanotubes.

It is hoped the material can be used to coat the electrodes of supercapacitors — electrochemical components that can store extremely large amounts of electrical energy — whilst also offering a solution to the growing environmental problem caused by used-cigarette filters.

An Aug. 5, 2014 Institute of Physics (IOP) news release (also on EurekAlert), which originated the news item, further describes the situation regarding used cigarette butts and the characteristics that could render them into supercapacitors

It is estimated that as many as 5.6 trillion cigarette butts (equivalent to 766 571 metric tons), are deposited into the environment worldwide every year.

Co-author of the study Professor Jongheop Yi, from Seoul National University, said: “Our study has shown that used cigarette filters can be transformed into a high-performing carbon-based material using a simple one-step process, which simultaneously offers a green solution to meeting the energy demands of society.

“Numerous countries are developing strict regulations to avoid the trillions of toxic and non-biodegradable used cigarette filters that are disposed of into the environment each year; our method is just one way of achieving this.”

Carbon is the most popular material that supercapacitors are composed of, due to its low cost, high surface area, high electrical conductivity and long-term stability.

Scientists around the world are currently working towards improving the characteristics of supercapacitors – such as energy density, power density and cycle stability – while also trying to reduce production costs.

In their study, the researchers demonstrated that the cellulose acetate fibres that cigarette filters are mostly composed of could be transformed into a carbon-based material using a simple, one-step burning technique called pyrolysis.

As a result of this burning process, the resulting carbon-based material contained a number of tiny pores, increasing its performance as a supercapacitive material.

“A high-performing supercapacitor material should have a large surface area, which can be achieved by incorporating a large number of small pores into the material,” continued Professor Yi.

“A combination of different pore sizes ensures that the material has high power densities, which is an essential property in a supercapacitor for the fast charging and discharging.”

Once fabricated, the carbon-based material was attached to an electrode and tested in a three-electrode system to see how well the material could adsorb electrolyte ions (charge) and then release them (discharge).

The material stored a higher amount of electrical energy than commercially available carbon and also had a higher amount of storage compared to graphene and carbon nanotubes, as reported in previous studies.

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

Preparation of energy storage material derived from a used cigarette filter for a supercapacitor electrode by Minzae Lee, Gil-Pyo Kim, Hyeon Don Song, Soomin Park, and Jongheop Yi. Nanotechnology 25 (34) 5601 doi:10.1088/0957-4484/25/34/345601

This is an open access paper.

Germany’s nano-supercapacitors for electric cars

Kudos to the writer for giving a dull topic, supercapacitors and electric cars, a jolt of life. From a July 24, 2014 news item on ScienceDaily,

Innovative nano-material based supercapacitors are set to bring mass market appeal a good step closer to the lukewarm public interest in Germany. [emphasis mine] This movement is currently being motivated by the advancements in the state-of-the-art of this device.

A July 1, 2014 Fraunhofer-Gesellschaft press release (also on EurekAlert), which originated the news item and, sadly, did not reveal the writer’s name, goes on in this refreshing fashion,

Electric cars are very much welcomed in Norway and they are a common sight on the roads of the Scandinavian country – so much so that electric cars topped the list of new vehicle registrations for the second time. This poses a stark contrast to the situation in Germany, where electric vehicles claim only a small portion of the market. Of the 43 million cars on the roads in Germany, only a mere 8000 are electric powered. The main factors discouraging motorists in Germany from switching to electric vehicles are the high investments cost, their short driving ranges and the lack of charging stations. Another major obstacle en route to the mass acceptance of electric cars is the charging time involved. The minutes involved in refueling conventional cars are so many folds shorter that it makes the situation almost incomparable. However, the charging durations could be dramatically shortened with the inclusion of supercapacitors. These alternative energy storage devices are fast charging and can therefore better support the use of economical energy in electric cars. Taking traditional gasoline-powered vehicles for instance, the action of braking converts the kinetic energy into heat which is dissipated and unused. Per contra, generators on electric vehicles are able to tap into the kinetic energy by converting it into electricity for further usage. This electricity often comes in jolts and requires storage devices that can withstand high amount of energy input within a short period of time. In this example, supercapacitors with their capability in capturing and storing this converted energy in an instant fits in the picture wholly. Unlike batteries that offer limited charging/discharging rates, supercapacitors require only seconds to charge and can feed the electric power back into the air-conditioning systems, defogger, radio, etc. as required.

So, the Norwegians have embraced electric cars while the Germans have remained reluctant. The writer offers a clear explanation of supercapacitors and mentions a solution for improving the electric vehicle acceptance rate in Germany (from the press release)

Rapid energy storage devices are distinguished by their energy and power density characteristics – in other words, the amount of electrical energy the device can deliver with respect to its mass and within a given period of time. Supercapacitors are known to possess high power density, whereby large amounts of electrical energy can be provided or captured within short durations, albeit at a short-coming of low energy density. The amount of energy in which supercapacitors are able to store is generally about 10% that of electrochemical batteries (when the two devices of same weight are being compared). This is precisely where the challenge lies and what the “ElectroGraph” project is attempting to address.

ElectroGraph is a project supported by the EU and its consortium consists of ten partners from both research institutes and industries. One of the main tasks of this project is to develop new types of supercapacitors with significantly improved energy storage capacities. As the project is approaches its closing phase in June, the project coordinator at Fraunhofer Institute for Manufacturing Engineering and Automation IPA in Stuttgart, Carsten Glanz explained the concept and approach taken en route to its successful conclusion: “during the storage process, the electrical energy is stored as charged particles attached on the electrode material.” “So to store more energy efficiently, we designed light weight electrodes with larger, usable surfaces.”

Next, the ‘nano’ aspect (graphene) of this particular project is explained,

In numerous tests, the researcher and his team investigated the nano-material graphene, whose extremely high specific surface area of up to 2,600 m2/g and high electrical conductivity practically cries out for use as an electrode material. It consists of an ultrathin monolayer lattice made of carbon atoms. When used as an electrode material, it greatly increases the surface area with the same amount of material. From this aspect, graphene is showing its potential in replacing activated carbon – the material that has been used in commercial supercapacitors to date – which has a specific surface area between 1000 and 1800 m2/g.

“The space between the electrodes is filled with a liquid electrolyte,” revealed Glanz. “We use ionic liquids for this purpose. Graphene-based electrodes together with ionic liquid electrolytes present an ideal material combination where we can operate at higher voltages.” “By arranging the graphene layers in a manner that there is a gap between the individual layers, the researchers were able to establish a manufacturing method that efficiently uses the intrinsic surface area available of this nano-material. This prevents the individual graphene layers from restacking into graphite, which would reduce the storage surface and consequently the amount of energy storage capacity. “Our electrodes have already surpassed commercially available one by 75 percent in terms of storage capacity,” emphasizes the engineer. “I imagine that the cars of the future will have a battery connected to many capacitors spread throughout the vehicle, which will take over energy supply during high-power demand phases during acceleration for example and ramming up of the air-conditioning system. These capacitors will ease the burden on the battery and cover voltage peaks when starting the car. As a result, the size of massive batteries can be reduced.”

Whether this effort has already been or, at some time in the future, will be demonstrated is not entirely clear to me,

In order to present the new technology, the ElectroGraph consortium developed a demonstrator consisting of supercapacitors installed in an automobile side-view mirror and charged by a solar cell in an energetically self-sufficient system. The demonstrator will be unveiled at the end of May [2015?] during the dissemination workshop at Fraunhofer IPA.

I imagine improved supercapacitors will be prove to be an enticement for more than one reluctant electric car purchaser no matter where they reside.

Steampower via nanotechnology

It seems that researchers at MIT (Massachusetts Institute of Technology (US) have been inspired by steam punk, of a sort. From a July 21, 2014 news item on Nanowerk,

A new material structure developed at MIT generates steam by soaking up the sun.

The structure — a layer of graphite flakes and an underlying carbon foam — is a porous, insulating material structure that floats on water. When sunlight hits the structure’s surface, it creates a hotspot in the graphite, drawing water up through the material’s pores, where it evaporates as steam. The brighter the light, the more steam is generated.

The new material is able to convert 85 percent of incoming solar energy into steam — a significant improvement over recent approaches to solar-powered steam generation. What’s more, the setup loses very little heat in the process, and can produce steam at relatively low solar intensity. This would mean that, if scaled up, the setup would likely not require complex, costly systems to highly concentrate sunlight.

A July 21, 2014 MIT news release, which originated the news item, details the research,

Hadi Ghasemi, a postdoc in MIT’s Department of Mechanical Engineering, says the spongelike structure can be made from relatively inexpensive materials — a particular advantage for a variety of compact, steam-powered applications.

“Steam is important for desalination, hygiene systems, and sterilization,” says Ghasemi, who led the development of the structure. “Especially in remote areas where the sun is the only source of energy, if you can generate steam with solar energy, it would be very useful.”

Today, solar-powered steam generation involves vast fields of mirrors or lenses that concentrate incoming sunlight, heating large volumes of liquid to high enough temperatures to produce steam. However, these complex systems can experience significant heat loss, leading to inefficient steam generation.

Recently, scientists have explored ways to improve the efficiency of solar-thermal harvesting by developing new solar receivers and by working with nanofluids. The latter approach involves mixing water with nanoparticles that heat up quickly when exposed to sunlight, vaporizing the surrounding water molecules as steam. But initiating this reaction requires very intense solar energy — about 1,000 times that of an average sunny day.

By contrast, the MIT approach generates steam at a solar intensity about 10 times that of a sunny day — the lowest optical concentration reported thus far. The implication, the researchers say, is that steam-generating applications can function with lower sunlight concentration and less-expensive tracking systems.

“This is a huge advantage in cost-reduction,” Ghasemi says. “That’s exciting for us because we’ve come up with a new approach to solar steam generation.”

The approach itself is relatively simple: Since steam is generated at the surface of a liquid, Ghasemi looked for a material that could both efficiently absorb sunlight and generate steam at a liquid’s surface.

After trials with multiple materials, he settled on a thin, double-layered, disc-shaped structure. Its top layer is made from graphite that the researchers exfoliated by placing the material in a microwave. The effect, Chen says, is “just like popcorn”: The graphite bubbles up, forming a nest of flakes. The result is a highly porous material that can better absorb and retain solar energy.

The structure’s bottom layer is a carbon foam that contains pockets of air to keep the foam afloat and act as an insulator, preventing heat from escaping to the underlying liquid. The foam also contains very small pores that allow water to creep up through the structure via capillary action.

As sunlight hits the structure, it creates a hotspot in the graphite layer, generating a pressure gradient that draws water up through the carbon foam. As water seeps into the graphite layer, the heat concentrated in the graphite turns the water into steam. The structure works much like a sponge that, when placed in water on a hot, sunny day, can continuously absorb and evaporate liquid.

The researchers tested the structure by placing it in a chamber of water and exposing it to a solar simulator — a light source that simulates various intensities of solar radiation. They found they were able to convert 85 percent of solar energy into steam at a solar intensity 10 times that of a typical sunny day.

Ghasemi says the structure may be designed to be even more efficient, depending on the type of materials used.

“There can be different combinations of materials that can be used in these two layers that can lead to higher efficiencies at lower concentrations,” Ghasemi says. “There is still a lot of research that can be done on implementing this in larger systems.”

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

Solar steam generation by heat localization by Hadi Ghasemi, George Ni, Amy Marie Marconnet, James Loomis, Selcuk Yerci, Nenad Miljkovic, & Gang Chen. Nature Communications 5, Article number: 4449 doi:10.1038/ncomms5449 Published 21 July 2014

This paper is behind a paywall but a free preview is available via ReadCube Access.

Mining uranium from the ocean

We are running short of uranium as terrestrial mining of this element has become more hazardous environmentally. A July 18, 2014 news item on Azonano highlights an ‘ocean mining’ uranium project at the University of Alabama (US),

The U.S. Department of Energy [DOE] selected a University of Alabama [UA] start-up company for an approximate $1.5 million award to refine an alternative material to potentially extract uranium from the ocean.

Uranium, which naturally occurs in seawater and in the Earth’s crust, is the fuel for nuclear power. For decades, scientists have sought a more economical and efficient way to remove it from the ocean, as the terrestrial supply is dwindling and environmentally unfriendly to mine.

A July 17, 2014 University of Alabama news release, which originated the news item, describe the University of Alabama’s unique approach to the problem of extracting uranium from the ocean (Note: A link has been removed),

“Every scientist in the world, except us, who is trying to do this is working with plastics,” said Dr. Gabriela Gurau, a chemist and CEO of the UA-based company, 525 Solutions.

Instead, the UA company is developing an adsorbent, biodegradable material made from the compound chitin, which is found in shrimp shells and in other crustaceans and insects. The researchers have developed transparent sheets, or mats, comprised of tiny chitin fibers, modified for the task. When suspended beneath the ocean’s surface, the mats are designed to withdraw uranium.

“Once you put it in the ocean, it will attract uranium like a magnet, and uranium will stick to it,” said Gurau, a University of Alabama alumna.

If one day implemented, the mats, with uranium attached, would be taken to an industrial plant where the nuclear fuel source would be removed.

Earlier work led by Dr. Robin Rogers, Robert Ramsay Chair of Chemistry at UA and director of UA’s Center for Green Manufacturing, initially proved the concept for extracting uranium using chitin. Rogers is an owner/founder of 525 Solutions and serves as a scientific adviser to the company’s representatives.

“The oceans are estimated to contain more than a thousand times the amount of uranium found in total in any known land deposit,” Rogers said. “Fortunately, the concentration of uranium in the ocean is very, very low, but the volume of the oceans is, of course, very, very high. Assuming we could recover only half of this resource, this much uranium could support 6,500 years of nuclear capacity.”

Removing chitin, in a pure form, from shells had previously proven difficult, but Rogers and his UA colleagues discovered a way to use a relatively new class of solvents, called ionic liquids, for removal. Ionic liquids are liquid salts which have other unique and desirable properties that traditional solvents do not. Rogers is recognized as a world-leader in the field of  ionic liquids.

UA researchers use a time-honored laboratory technique called electrospinning to produce the mats. In this process, the scientists use a specially-prepared, chitin-based, ionic liquid solution, which is loaded in the electrospinning apparatus. Some 30,000 volts of electricity are applied, spinning the fibers into a water bath. After several hours, nanofiber mats, consisting of fibers much thinner than a strand of a spider’s web, form, weaved together into a solid sheet.

The increased surface area the nanomats provide is central to the project, said Dr. Julia Shamshina, the company’s chief technology officer and also a UA alumna.

“The larger the surface area, the larger modifications we can make and the more uranium it will uptake,” Shamshina said. “If you have one very thick fiber and 10 which, when combined, equal the size of the thick fiber, the ten smaller ones will take up hundreds, or even thousands, of times more uranium.”

Rogers extolled the potential environmental benefits of  the company’s approach and addressed cost factors.

“Mining uranium from land is a very dirty, energy intensive process, with a lot of hazardous waste produced,” Rogers said. “If we eliminate land mining by mining from the ocean, we not only clean up the ocean, we eliminate all of the environmental problems with terrestrial mining.

“Research studies have shown that uranium can be extracted from the ocean, but the process remains prohibitively costly,” said Rogers, a  two-time UA graduate. “The search for more effective adsorbents — which is what we’re doing  – is under way and expected to solve this issue.”

Gurau said the two-year grant, from the DOE’s Office of Science through its Small Business Innovation Research and Small Business Technology Transfer programs, will enable the researchers to refine their processes, measure costs and conduct an environmental analysis.

“We need to know if it’s viable from an economic standpoint,” Gurau said. “I think this is a critical step in getting this to the pilot-plant stage.”