Posts belonging to Category green power

Doubling The Electrical Output Of Solar Cells

One challenge in improving the efficiency of solar cells is that some of the absorbed light energy is lost as heat. So scientists have been looking to design materials that can convert more of that energy into useful electricity. Now a team from the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory and Columbia University has paired up polymers that recover some of that lost energy by producing two electrical charge carriers per unit of light instead of the usual one.

solar cell
Critically, we show how this multiplication process can be made efficient on a single molecular polymer chain,” said physicist Matthew Sfeir, who led the research at Brookhaven Lab’s Center for Functional Nanomaterials (CFN), a DOE Office of Science User Facility. Having the two charges on the same molecule means the light-absorbing, energy-producing materials don’t have to be arrayed as perfect crystals to produce extra electrical charges. Instead, the self-contained materials work efficiently when dissolved in liquids, which opens the way for a wide range of industrial scale manufacturing processes, including “printingsolar-energy-producing material like ink.

The research is published as an Advance Online Publication in Nature Materials, January 12, 2015.


Anti reflective Solar Cells Boost Energy Output

Reducing the amount of sunlight that bounces off the surface of solar cells helps maximize the conversion of the sun’s rays to electricity, so manufacturers use coatings to cut down on reflections. Now scientists at the U.S. Department of Energy’s Brookhaven National Laboratory show that etching a nanoscale texture onto the silicon material itself creates an antireflective surface that works as well as state-of-the-art thin-film multilayer coatings. The surface nanotexture … drastically cut down on reflection of many wavelengths of light simultaneously.
Their method, described in the journal Nature Communications and submitted for patent protection, has potential for streamlining silicon solar cell production and reducing manufacturing costs. The approach may find additional applications in reducing glare from windows, providing radar camouflage for military equipment, and increasing the brightness of light-emitting diodes.

antireflection square of siliconA closeup shows how the nanotextured square of silicon completely blocks reflection compared with the surrounding silicon wafer
For antireflection applications, the idea is to prevent light or radio waves from bouncing at interfaces between materials,” said physicist Charles Black, who led the research at Brookhaven Lab’s Center for Functional Nanomaterials (CFN), a DOE Office of Science User Facility.
The issue with using such coatings for solar cells,” he said, “is that we’d prefer to fully capture every color of the light spectrum within the device, and we’d like to capture the light irrespective of the direction it comes from. But each color of light couples best with a different antireflection coating, and each coating is optimized for light coming from a particular direction. So you deal with these issues by using multiple antireflection layers. We were interested in looking for a better way.”


Super Battery For Electric Vehicles

An ultra-thin nanomaterial is at the heart of a major breakthrough by scientists from the University of Waterloo (Canada) who are in a global race to invent a cheaper, lighter and more powerful rechargeable battery for electric vehicles. Chemistry Professor Linda Nazar and her research team in the Faculty of Science at the University of Waterloo have announced a breakthrough in lithium-sulphur battery technology in a recent issue of Nature Communications.

Their discovery of a material that maintains a rechargable sulphur cathode helps to overcome a primary hurdle to building a lithium-sulphur (Li-S) battery. Such a battery can theoretically power an electric car three times further than current lithium-ion batteries for the same weight – at much lower cost.
Sulphur as a battery material is extremely abundant, relatively light, and very cheap.

electric car
This is a major step forward and brings the lithim-sulphur battery one step closer to reality,” said Nazar, who also holds the Canada Research Chair in Solid State Energy Materials.
You have to focus on the a fundamental understanding of the phenomenon before you can develop new, advanced materials,” said Nazar.

They found that the oxygenated surface of the ultrathin MnO2 nanosheet chemically recycles the sulphides in a two-step process involving a surface-bound intermediate, polythiosulfate. The result is a high-performance cathode that can recharge more than 2000 cycles.


Nano Filters Clean Dirty Industry

Prototypes of nano-cellulose based filters with high purification capacity towards environmentally hazardous contaminants from industrial effluents eg. process industries, have been developed by researchers at Luleå University of Technology (Sweden). The research, conducted in collaboration with Imperial College in the UK has reached a breakthrough with the prototypes and they will now be tested on a few industries in Europe.

- The bio-based filter of nano-cellulose is to be used for the first time in real-life situations and tested within a process industry and in municipal wastewater treatment in Spain. Other industries have also shown interest in this technology and representatives of the mining industry have contacted me and I have even received requests from a large retail chain in the UK, says Aji Mathew Associate Professor, Division of Materials Science at Luleå University.
nano filter

Researchers have combined a cheap residue from the cellulose industry, with functional nano-cellulose to prepare adsorbent sheets with high filtration capacity. The sheets have since been constructed to different prototypes, called cartridges, to be tested. They have high capacity and can filter out heavy metal ions from industrial waters, dyes residues from the printing industry and nitrates from municipal water. Next year, larger sheets with a layer of nano-cellulose can be produced and formed into cartridges, with higher capacity.

- Each such membrane can be tailored to have different removal capability depending on the kind of pollutant, viz., copper, iron, silver, dyes, nitrates and the like.


Nano Sponges Cut Greenhouse Gases

In the fight against global warming, carbon capture – chemically trapping carbon dioxide before it releases into the atmosphere – is gaining momentum, but standard methods are plagued by toxicity, corrosiveness and inefficiency. Using a bag of chemistry tricks, Cornell materials scientists have invented low-toxicity, highly effective carbon-trapping “sponges” that could lead to increased use of the technology. A research team led by Emmanuel Giannelis, Professor of Engineering, has invented a powder that performs as well or better than industry benchmarks for carbon capture.
The researchers have been working on a better, safer carbon-capture method . Their latest consists of a silica scaffold, the sorbent support, with nanoscale pores for maximum surface area. They dip the scaffold into liquid amine, which soaks into the support like a sponge and partially hardens. The finished product is a stable, dry white powder that captures carbon dioxide even in the presence of moisture.

A scanning electron microscopy image of a pristine silica support, before the amine is added
We have made great strides in sustainability, particularly in the energy supply areas of alternative energy sources, and the demand side areas of energy conservation and building design standards,” KyuJung Whang, Cornell’s vice president for facilities services said.

A paper with their results, co-authored by postdoctoral associates Genggeng Qi and Liling Fu, appeared in Nature Communications.

How To Make Drinking Water From Air Humidity

Understanding how a desert beetle harvests water from dew could help to improve drinking water collection in dew condensers mimicking the nanostructure of the beetle’s back

Insects are full of marvels—and this is certainly the case with a beetle from the Tenebrionind family, found in the extreme conditions of the Namib desert. Now, a team of scientists from ESPCI Paristech – France – has demonstrated that such insects can collect dew on their backs—and not just fog as previously thought. This is made possible by the wax nanostructure on the surface of the beetle’s elytra. These findings by José Guadarrama-Cetina,and colleagues were recently published in EPJ E. They bring us a step closer to harvesting dew to make drinking water from the humidity in the air. This, the team hopes, can be done by improving the water yield of man-made dew condensers that mimick the nanostructure on the beetle’s back.
desert beerle
It was not clear from previous studies whether water harvested by such beetles came from dew droplets, in addition to fog.

Guadarrama-Cetina and colleagues also performed an image analysis of dew drops forming on the insect’s back on the surface of the elytra, which appears as a series of bumps and valleys. Dew primarily forms in the valleys endowed with a hexagonal microstructure, they found, unlike the smooth surface of the bumps. This explains how drops can slide to the insect’s mouth when they reach a critical size.

Spray-on Solar Power

Pretty soon, powering your tablet could be as simple as wrapping it in cling wrap. Illan Kramer and colleagues from the University of Toronto (U of T) have just invented a new way to spray solar cells onto flexible surfaces using miniscule light-sensitive materials known as colloidal quantum dots (CQDs)—a major step toward making spray-on solar cells easy and cheap to manufacture. Solar-sensitive CQDs printed onto a flexible film could be used to coat all kinds of weirdly shaped surfaces, from patio furniture to an airplane’s wing. A surface the size of your car’s roof wrapped with CQD-coated film would produce enough energy to power three 100-Watt light bulbs — or 24 compact fluorescents. He calls his system sprayLD, a play on the manufacturing process called ALD, short for atomic layer deposition, in which materials are laid down on a surface one atom-thickness at a time.
In two recent papers in the journals Advanced Materials and Applied Physics Letters, Kramer showed that the sprayLD method can be used on flexible materials without any major loss in solar-cell efficiency. Kramer built his sprayLD device using parts that are readily available and rather affordable—he sourced a spray nozzle used in steel mills to cool steel with a fine mist of water, and a few regular air brushes from an art store.
spray-on solar cells
My dream is that one day you’ll have two technicians with Ghostbusters backpacks come to your house and spray your roof,” said Kramer, a post-doctoral fellow with The Edward S. Rogers Sr. Department of Electrical & Computer Engineering at the University of Toronto and IBM Canada’s Research and Development Centre.
This is something you can build in a Junkyard Wars fashion, which is basically how we did it,” said Kramer.

“As quantum dot solar technology advances rapidly in performance, it’s important to determine how to scale them and make this new class of solar technologies manufacturable,” said Professor Ted Sargent (ECE), vice dean, research in the Faculty of Applied Science & Engineering at University of Toronto and Kramer’s supervisor. “We were thrilled when this attractively manufacturable spray-coating process also led to superior performance devices showing improved control and purity.”


Rewritable Paper 20 Times

First developed in China in about the year A.D. 150, paper has many uses, the most common being for writing and printing upon. Indeed, the development and spread of civilization owes much to paper’s use as writing material.
According to some surveys, 90 percent of all information in businesses today is retained on paper, even though the bulk of this printed paper is discarded after just one-time use.
Such waste of paper (and ink cartridges) — not to mention the accompanying environmental problems such as deforestation and chemical pollution to air, water and land — could be curtailed if the paper were “rewritable,” that is, capable of being written on and erased multiple times.

Chemists at the University of California, Riverside have now fabricated in the lab just such novel rewritable paper, one that is based on the color switching property of commercial chemicals called redox dyes. The dye forms the imaging layer of the paper. Printing is achieved by using ultraviolet light to photobleach the dye, except the portions that constitute the text on the paper. The new rewritable paper can be erased and written on more than 20 times with no significant loss in contrast or resolution.
Rewritable-paper-Yadong Yin’s lab at the University of California, Riverside has fabricated novel rewritable paper, one that is based on the color switching property of commercial chemicals called redox dyes
This rewritable paper does not require additional inks for printing, making it both economically and environmentally viable,” said Yadong Yin, a professor of chemistry, whose lab led the research. “It represents an attractive alternative to regular paper in meeting the increasing global needs for sustainability and environmental conservation.
Study results appear online in Nature Communications.


Solar Panels Covering Car Parks Produce Cheap Energy

The world is full of car parks. And one British start-up wants us to be using them to produce green energy. Founder of the Solar Cloth Company, Perry Carroll, says his flexible solar panels can be placed on structures that can’t take the weight of traditional glass panels. Like this car park in Cambridge.
solar roof
There are enough car parking spaces in Great Britain that if we covered with solar, we would end up without having an energy problem at all in Great Britain. Now, we don’t have to cover farming fields, we don’t have to cover roofs, we don’t have to cover, if you wish to call it, new areas. This is existing infrastructure that people use“, says Perry Carroll, the founder of the Solar Cloth Company. The company’s Innovation Director Christopher Jackson says the lightweight, flexible panels can also be used on non-load bearing commercial roof space.

Roofs which you would never see otherwise can now be turned into sources of electricity. And that means you don’t have to have any impact on the environment, there are no concerns to take into account of planning. It’s an elegant solution to turn an otherwise unused space into a source of electricity“, Jackson adds. And the company also has iconic buildings such as the 02 Arena in London in its sights.
Perry Carroll concludes: “Imagine that powering itself, because it’s been covered in a flexible solar tensile structure. Imagine looking at things like the Sydney Opera House, imagine looking at sporting stadia where basically the ground is completely covered with a solar solution that allows you to one, appreciate the artistic merits of the design of the stadium, but it also allows you to create energy for its needs.”


A Billion Holes Make a Postage Stamp Battery

Researchers at the University of Maryland (UMD) have invented a single tiny structure that includes all the components of a battery that they say could bring about the ultimate miniaturization of energy storage components.
A billion nanopores could fit on a postage stamp
The structure is called a nanopore: a tiny hole in a ceramic sheet that holds electrolyte to carry the electrical charge between nanotube electrodes at either end. The existing device is a test, but the bitsy battery performs well. First author Chanyuan Liu, a Ph.D. student in materials science, says that it can be fully charged in 12 minutes, and it can be recharged thousands of time.

Many millions of these nanopores can be crammed into one larger battery the size of a postage stamp. One of the reasons the researchers think this unit is so successful is because each nanopore is shaped just like the others, which allows them to pack the tiny thin batteries together efficiently.The space inside the holes is so small that the space they take up, all added together, would be no more than a grain of sand.
Now that the scientists have the battery working and have demonstrated the concept, they have also identified improvements that could make the next version 10 times more powerful. The next step to commercialization: the inventors have conceived strategies for manufacturing the battery in large batches.

A team of UMD chemists and materials scientists collaborated on the project: Gary Rubloff, director of the Maryland NanoCenter, Sang Bok Lee, a professor in the Department of Chemistry and seven of their Ph.D. students.