New Nanomaterial helps Store Solar Energy (as Hydrogen) Efficiently and Inexpensively


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Efficient storage technologies are necessary if solar and wind energy is to help satisfy increased energy demands.

One important approach is storage in the form of hydrogen extracted from water using solar or wind energy. This process takes place in a so-called electrolyser. Thanks to a new material developed by researchers at the Paul Scherrer Institute PSI and Empa, these devices are likely to become cheaper and more efficient in the future. The material in question works as a catalyst accelerating the splitting of water molecules: the first step in the production of hydrogen. Researchers also showed that this new material can be reliably produced in large quantities and demonstrated its performance capability within a technical electrolysis cell – the main component of an electrolyser. The results of their research have been published in the current edition of the scientific journal Nature Materials.

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The scientists Emiliana Fabbri and Thomas Schmidt in a lab at PSI where they conducted experiments to study the performance of the newly developed catalyst for electrolysers. (Photo: Paul Scherrer Institute/Mahir Dzambegovic.)

Since solar and wind energy is not always available, it will only contribute significantly to meeting energy demands once a reliable storage method has been developed. One promising approach to this problem is storage in the form of hydrogen. This process requires an electrolyser, which uses electricity generated by solar or wind energy to split water into hydrogen and oxygen. Hydrogen serves as an energy carrier. It can be stored in tanks and later transformed back into electrical energy with the help of fuel cells. This process can be carried out locally, in places where energy is needed such as domestic residences or fuel cell vehicles, enabling mobility without the emission of CO2.

Inexpensive and efficient

Researchers at the Paul Scherrer Institute PSI have now developed a new material that functions as a catalyst within an electrolyser and thus accelerates the splitting of water molecules: the first step in the production of hydrogen. “There are currently two types of electrolysers on the market: one is efficient but expensive because its catalysts contain noble metals such as iridium. The others are cheaper but less efficient”, explains Emiliana Fabbri, researcher at the Paul Scherrer Institute. “We wanted to develop an efficient but less expensive catalyst that worked without using noble metals.”

Exploring this procedure, researchers were able to use a material that had already been developed: an intricate compound of the elements barium, strontium, cobalt, iron and oxygen – a so-called perovskite. But they were the first to develop a technique enabling its production in the form of miniscule nanoparticles. This is the form required for it to function efficiently since a catalyst requires a large surface area on which many reactive centres are able to accelerate the electrochemical reaction. Once individual catalyst particles have been made as small as possible, their respective surfaces combine to create a much larger overall surface area.

Researchers used a so-called flame-spray device to produce this nanopowder: a device operated by Empa that sends the material’s constituent parts through a flame where they merge and quickly solidify into small particles once they leave the flame. “We had to find a way of operating the device that reliably guaranteed the solidifying of the atoms of the various elements in the right structure,” emphasizes Fabbri. “We were also able to vary the oxygen content where necessary, enabling the production of different material variants.”

Successful Field Tests

Researchers were able to show that these procedures work not only in the laboratory but also in practice. The production method delivers large quantities of the catalyst powder and can be made readily available for industrial use. “We were eager to test the catalyst in field conditions. Of course, we have test facilities at PSI capable of examining the material but its value ultimately depends upon its suitability for industrial electrolysis cells that are used in commercial electrolysers,” says Fabbri. Researchers tested the catalyst in cooperation with an electrolyser manufacturer in the US and were able to show that the device worked more reliably with the new PSI-produced perovskite than with a conventional iridium-oxide catalyst.

Examining in Milliseconds

Researchers were also able to carry out precise experiments that provided accurate information on what happens in the new material when it is active. This involved studying the material with X-rays at PSI’s Swiss Light Source SLS. This facility provides researchers with a unique measuring station capable of analysing the condition of a material over successive timespans of just 200 milliseconds. “This enables us to monitor changes in the catalyst during the catalytic reaction: we can observe changes in the electronic properties or the arrangement of atoms,” says Fabbri. At other facilities, each individual measurement takes about 15 minutes, providing only an averaged image at best.” These measurements also showed how the structures of particle surfaces change when active – parts of the material become amorphous which means that the atoms in individual areas are no longer uniformly arranged. Unexpectedly, this makes the material a better catalyst.

Use in the ESI Platform

Working on the development of technological solutions for Switzerland’s energy future is an essential aspect of the research carried out at PSI. To this end, PSI makes its ESI (Energy System Integration) experimental platform available to research and industry, enabling promising solutions to be tested in a variety of complex contexts. The new catalyst provides an important base for the development of a new generation of water electrolysers.

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Beyond Tesla: Solar-Powered Battery Challenges Cost of Electricity in Australia


australia-solar-plug1Australia is at the dawn of a battery storage revolution. A recent report from US-based IHS Technology states that Australia’s energy storage market will grow from less than 500 battery installations in 2015 to 30,000 installations by 2018, while Morgan Stanley has found that half of all households in Australia are interested in installing solar panels with battery storage, with the market potential estimated to be $24bn.

 

From the lithium battery Tesla Powerwall unit to the lead acid gel battery ofAllGrid Energy’s GridWatt system, the Australian market seems to be welcoming one battery innovation after another.

However, one of the biggest gripes for those early adopters buying battery storage systems at the moment is the loss of efficiency of devices. For example, the Tesla Powerwall starts off with about 92% efficiency but, as the lithium cells degrade over time, these efficiencies, and its capacity, drop further.

But a new battery has come onto the Australian market that claims to not only maintain 100% of its storage capacity but also has a round trip DC-DC energy efficiency per cycle of 80% and is recyclable at its end of life. The ZCell is a zinc bromide flow battery designed by the Australian energy storage provider Redflowand is said to be the world’s smallest flow battery on the market. It could also have broad reaching implications for everyone’s electricity bills – if power grid operators take note.

Redflow’s executive chairman, Simon Hackett, with the ZCell
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Redflow’s executive chairman, Simon Hackett, with the ZCell. Photograph: ZCell

Originally designed for the commercial, industrial and telecommunication sectors, the ZBM battery has now been repackaged as the ZCell for the residential market, allowing people to “timeshift” solar power from day to night, store off-peak power for peak demand periods and support off-grid systems. Bizarrely, Redflow thanks Tesla for ZCell’s realisation.

“Energy storage is having its moment in the sun as a concept and we have Tesla to thank for that, for really lighting the battery storage fire”, says Redflow’s executive chairman, Simon Hackett.

Hackett says that although Tesla has been the harbinger of household battery storage in Australia, there’s room for improvement.

“There are different batteries suited for different sorts of applications. While it’s absolutely logical for Tesla to be packaging their lithium batteries for home use, I think lithium batteries are better suited for cars while flow batteries are better for the residential market.”

Redflow has designed the outdoor battery ZCell, which is about the size of a standard air conditioner unit, stores 10 kW hours (kWh) of electricity and comes with a 10-year warranty. What makes the battery really stand out, says Hackett, is that it can store as much energy at its end of life as it does at the beginning.

“Lithium battery cells get worn out when worked hard, as lithium is a sprinter of a battery. What you need for your house is a marathon runner and that’s what our flow battery is. It’s an industrial-strength battery built to go from completely full to dead empty every day.

The first ZCells are expected to go to homes later this year (around June) and Hackett estimates that the final cost for the system, including installation, will be about $18,000.

“It’s not an entry-level price,” Hackett concedes. “But it’s a large battery.”

ZCell is also recyclable when it reaches its end of life, as the zinc bromide solution can be cleaned and put into a new battery, while the plastic casing and electrodes can be recycled into bottles.

Hackett suggests the unit would be most useful for householders using large amounts of energy – for example, those who have electric cars. Hackett himself is said to be Tesla’s biggest individual customer in Australia for electric cars – and he’s charging them with the ZCell battery.Australia 042016 Solar-PV-uptake-in-Australia-by-Sunwiz-SMH-Clean-Energy-Regulator

However, he adds that everyone could benefit from battery storage as it could transform the way the power grid works, making it cheaper and more effective.

 

Last year, it was found that Australians are paying significantly more than people in other parts of the world in electricity network charges. These high charges cover the cost of electricity poles and wires and make up more than half of electricity bills.

In the last five-year period (running to 2015), networks recovered $44bn from our energy bills, which was used to replace ageing infrastructure (such as power lines, like those in Kilmore East which triggered fatal bushfires in 2009) and cover the forecast increase in energy demand.

But things didn’t quite go according to plan. The AER’s State of the Energy Market report 2015 revealed that, for the first time in Australian history, “demand for electricity declined or stayed flat for six consecutive years to 30 June 2015”, meaning that some of the investments weren’t needed.

The problem was exacerbated by the fact that, as network charges rose, customers used even less energy, thus making network prices increase further to cover losses.

Hackett argues that energy companies will continue to “drive people off the grid if they get too greedy about fixed network costs”, adding that if networks instead installed batteries into the grid and encouraged householders to do so by committing to purchase excess energy off them, then they could potentially save millions of dollars, make the grid more efficient, cheaper for consumers and therefore more attractive.

The concept is something that grid operators are looking into, Hackett says. “It’s just a question of how quickly the economics and batteries improve to make that business case stack up.”

He adds: “As batteries get cheaper in the near future, I expect that networks will increasingly move to this model.”

UCLA: Chemists Devise Technology that could Transform Solar Energy Storage


Energy Storage 061915 chemistsdeviThe materials in most of today’s residential rooftop solar panels can store energy from the sun for only a few microseconds at a time. A new technology developed by chemists at UCLA is capable of storing solar energy for up to several weeks—an advance that could change the way scientists think about designing solar cells.

The findings are published June 19 in the journal Science.

The new design is inspired by the way that plants generate energy through photosynthesis.

“Biology does a very good job of creating energy from sunlight,” said Sarah Tolbert, a UCLA professor of chemistry and one of the senior authors of the research. “Plants do this through photosynthesis with extremely high efficiency.”

“In photosynthesis, plants that are exposed to sunlight use carefully organized nanoscale structures within their cells to rapidly separate charges—pulling electrons away from the positively charged molecule that is left behind, and keeping positive and negative charges separated,” Tolbert said. “That separation is the key to making the process so efficient.”

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The scientists devised a new arrangement of solar cell ingredients, with bundles of polymer donors (green rods) and neatly organized fullerene acceptors (purple, tan). Credit: UCLA Chemistry 

To capture energy from sunlight, conventional rooftop solar cells use silicon, a fairly expensive material. There is currently a big push to make lower-cost solar cells using plastics, rather than silicon, but today’s are relatively inefficient, in large part because the separated positive and negative electric charges often recombine before they can become electrical energy.

“Modern plastic solar cells don’t have well-defined structures like plants do because we never knew how to make them before,” Tolbert said. “But this new system pulls charges apart and keeps them separated for days, or even weeks. Once you make the right structure, you can vastly improve the retention of energy.”

The two components that make the UCLA-developed system work are a polymer donor and a nano-scale acceptor. The polymer donor absorbs sunlight and passes electrons to the fullerene acceptor; the process generates electrical energy.

The plastic materials, called organic photovoltaics, are typically organized like a plate of cooked pasta—a disorganized mass of long, skinny polymer “spaghetti” with random fullerene “meatballs.” But this arrangement makes it difficult to get current out of the cell because the electrons sometimes hop back to the polymer spaghetti and are lost.

The UCLA technology arranges the elements more neatly—like small bundles of uncooked spaghetti with precisely placed meatballs. Some fullerene meatballs are designed to sit inside the spaghetti bundles, but others are forced to stay on the outside. The fullerenes inside the structure take electrons from the polymers and toss them to the outside fullerene, which can effectively keep the electrons away from the polymer for weeks.

“When the charges never come back together, the system works far better,” said Benjamin Schwartz, a UCLA professor of chemistry and another senior co-author. “This is the first time this has been shown using modern synthetic organic photovoltaic materials.”

In the new system, the materials self-assemble just by being placed in close proximity.

“We worked really hard to design something so we don’t have to work very hard,” Tolbert said.

The new design is also more environmentally friendly than current technology, because the materials can assemble in water instead of more toxic organic solutions that are widely used today.

“Once you make the materials, you can dump them into water and they assemble into the appropriate structure because of the way the materials are designed,” Schwartz said. “So there’s no additional work.”

The researchers are already working on how to incorporate the technology into actual .

Yves Rubin, a UCLA professor of chemistry and another senior co-author of the study, led the team that created the uniquely designed molecules. “We don’t have these materials in a real device yet; this is all in solution,” he said. “When we can put them together and make a closed circuit, then we will really be somewhere.”

For now, though, the UCLA research has proven that inexpensive photovoltaic can be organized in a way that greatly improves their ability to retain from sunlight.

Explore further: Improving the efficiency of solar energy cells

More information: Long-lived photoinduced polaron formation in conjugated polyelectrolyte-fullerene assemblies Science 19 June 2015: Vol. 348 no. 6241 pp. 1340-1343. DOI: 10.1126/science.aaa6850

Rice U. Researchers Fine-Tune Quantum Dots from Coal


rice QD finetuneGraphene quantum dots made from coal, introduced in 2013 by the Rice University lab of chemist James Tour, can be engineered for specific semiconducting properties in either of two single-step processes.

In a new study this week in the American Chemical Society journal Applied Materials & Interfaces, Tour and colleagues demonstrated fine control over the graphene oxide dots’ size-dependent band gap, the property that makes them semiconductors. Quantum dots are semiconducting materials that are small enough to exhibit quantum mechanical properties that only appear at the nanoscale.

Tour’s group found they could produce quantum dots with specific semiconducting properties by sorting them through ultrafiltration, a method commonly used in municipal and industrial water filtration and in food production.

The other single-step process involved direct control of the reaction temperature in the oxidation process that reduced coal to quantum dots. The researchers found hotter temperatures produced smaller dots, which had different semiconducting properties.

Tour said graphene quantum dots may prove highly efficient in applications ranging from medical imaging to additions to fabrics and upholstery for brighter and longer-lasting colors. “Quantum dots generally cost about $1 million per kilogram and we can now make them in an inexpensive reaction between coal and acid, followed by separation. And the coal is less than $100 per ton.”

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The dots in these experiments all come from treatment of anthracite, a kind of coal. The processes produce batches in specific sizes between 4.5 and 70 nanometers in diameter.

Rice University scientists have produced graphene quantum dots produced from coal with tuned band gaps and photoluminescent properties. These quantum dots, seen with an electron microscope, average 70 nanometers in diameter. Credit: Tour Group/Rice University

Graphene quantum dots are photoluminescent, which means they emit light of a particular wavelength in response to incoming light of a different wavelength. The emitted light ranges from green (smaller dots) to orange-red (larger dots). Because the emitted color also depends on the dots’ size, this property can also be tuned, Tour said. The lab found quantum dots that emit blue light were easiest to produce from bituminous .

The researchers suggested their quantum dots may also enhance sensing, electronic and photovoltaic applications. For instance, catalytic reactions could be enhanced by manipulating the reactive edges of . Their fluorescence could make them suitable for metal or chemical detection applications by tuning to avoid interference with the target materials’ emissions.

Rice University scientists have produced graphene quantum dots produced from coal with tuned band gaps and photoluminescent properties. These quantum dots are about 4.5 nanometers in diameter. Credit: Tour Group/Rice University

Explore further: Making quantum dots glow brighter

Read more at: http://phys.org/news/2015-03-fine-tune-quantum-dots-coal.html#jCp

Solar Power, and Somewhere to Store It


MIT sunedisonx519An innovative startup that blends solar energy and battery storage reflects broader interest combining the technologies.

A growing number of companies are now selling large-scale battery storage together with solar installations to lower costs and to address challenges introduced by the intermittent nature of solar power, which is produced only when the sun is shining.

Last week the U.S. solar giant SunEdison announced that it had acquired Solar Grid Storage, a startup that integrates solar installations with battery storage. And SolarCity, the largest solar power installer in the U.S., is almost done installing 430 combined solar and storage systems in a pilot program in the San Francisco Bay area; the company plans to roll out the technology more widely this summer.+

The U.S. Department of Energy, meanwhile, is gathering proposals for $15 million worth of research projects aimed at finding more effective ways to combine photovoltaic and storage technology. One goal is to lower the cost of storing solar power to no more than the projected average U.S. grid price for residential power in 2020: 14 cents per kilowatt-hour. Solar storage currently costs about 20 cents to $1 per kilowatt-hour.+

As more solar power is installed, intermittency will become more of a problem. At the same time, though, the grid storage that could help compensate for this problem is becoming cheaper, and new converter technology can be used for both.+

Tom Leyden, formerly CEO of Solar Grid Storageand now SunEdison’s vice president for energy storage deployment, says his company is using a power converter that links both a photovoltaic array and a battery to the grid. Solar panels and batteries both need converters because they produce direct current (DC) power, whereas power grids carry alternating current (AC)

The company’s four operating projects in Maryland, Pennsylvania, and New Jersey are partnerships. The customer buys solar panels for its site, and Leyden’s operation provides a 10-by-20-foot shipping container holding the dual-use power converter and lithium-ion batteries.+

At the height of a sunny day, for example, the converter is primarily producing AC power from the host’s solar panels. At all other times, however, it feeds spare capacity to the battery to serve the regional utility.+

The solar tax break for the combined system is slated to drop from 30 percent of the equipment cost to 10 percent in 2017, but Leyden says the dual-use converters should also come down in price as more are produced.+