Posts belonging to Category green power



Solar Cells: How To Boost Perovkite Efficiency Up To 31%

Scientists from the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have discovered a possible secret to dramatically boosting the efficiency of perovskite solar cells hidden in the nanoscale peaks and valleys of the crystalline material.

Solar cells made from compounds that have the crystal structure of the mineral perovskite have captured scientists’ imaginations. They’re inexpensive and easy to fabricate, like organic solar cells. Even more intriguing, the efficiency at which perovskite solar cells convert photons to electricity has increased more rapidly than any other material to date, starting at three percent in 2009—when researchers first began exploring the material’s photovoltaic capabilities—to 22 percent today. This is in the ballpark of the efficiency of silicon solar cells.

Now, as reported online July 4 in the journal Nature Energy, a team of scientists from the Molecular Foundry and the Joint Center for Artificial Photosynthesis, both at Berkeley Lab, found a surprising characteristic of a perovskite solar cell that could be exploited for even higher efficiencies, possibly up to 31 percent.

Using photoconductive atomic force microscopy, the scientists mapped two properties on the active layer of the solar cell that relate to its photovoltaic efficiency. The maps revealed a bumpy surface composed of grains about 200 nanometers in length, and each grain has multi-angled facets like the faces of a gemstone. Unexpectedly, the scientists discovered a huge difference in energy conversion efficiency between facets on individual grains. They found poorly performing facets adjacent to highly efficient facets, with some facets approaching the material’s theoretical energy conversion limit of 31 percent. The scientists say these top-performing facets could hold the secret to highly efficient solar cells, although more research is needed.

perovskite solar panel

“If the material can be synthesized so that only very efficient facets develop, then we could see a big jump in the efficiency of perovskite solar cells, possibly approaching 31 percent,” says Sibel Leblebici, a postdoctoral researcher at the Molecular Foundry.

Leblebici works in the lab of Alexander Weber-Bargioni, who is a corresponding author of the paper that describes this research. Ian Sharp, also a corresponding author, is a Berkeley Lab scientist at the Joint Center for Artificial Photosynthesis. Other Berkeley Lab scientists who contributed include Linn Leppert, Francesca Toma, and Jeff Neaton, the director of the Molecular Foundry.

Source: http://newscenter.lbl.gov/

Nanotechnology Boosts Oil Recovery

As oil producers struggle to adapt to , getting as much oil as possible out of every well has become even more important, despite concerns from nearby residents that some chemicals used to boost production may pollute underground water resources.

Researchers from the University of Houston have reported the discovery of a nanotechnology-based solution that could address both issues – achieving 15 percent tertiary oil recovery at low cost, without the large volume of chemicals used in most commercial fluids. The solution – graphene-based Janus amphiphilic nanosheets – is effective at a concentration of just 0.01 percent, meeting or exceeding the performance of both conventional and other nanotechnology-based fluids, said Zhifeng Ren, MD Anderson Chair professor of physics. Janus nanoparticles have at least two physical properties, allowing different chemical reactions on the same particle.

The low concentration and the high efficiency in boosting tertiary oil recovery make the nanofluid both more environmentally friendly and less expensive than options now on the market, said Ren, who also is a principal investigator at the Texas Center for Superconductivity at UH. He is lead author on a paper describing the work, published June 27 in the Proceedings of the National Academy of Sciences.

oil well

Our results provide a novel nanofluid flooding method for tertiary oil recovery that is comparable to the sophisticated chemical methods,” they wrote. “We anticipate that this work will bring simple nanofluid flooding at low concentration to the stage of oilfield practice, which could result in oil being recovered in a more environmentally friendly and cost-effective manner.

The U.S. Department of Energy estimates as much as 75 percent of recoverable reserves may be left after producers capture hydrocarbons that naturally rise to the surface or are pumped out mechanically, followed by a secondary recovery process using water or gas injection.

Traditional “tertiaryrecovery involves injecting a chemical mix into the well and can recover between 10 percent and 20 percent, according to the authors. But the large volume of chemicals used in tertiary oil recovery has raised concerns about potential environmental damage.

Obviously simple nanofluid flooding (containing only nanoparticles) at low concentration (0.01 wt% or less) shows the greatest potential from the environmental and economic perspective,” the researchers wrote.

Previously developed simple nanofluids recover less than 5 percent of the oil when used at a 0.01 percent concentration, they reported. That forces oil producers to choose between a higher nanoparticle concentration – adding to the cost – or mixing with polymers or surfactants. In contrast, they describe recovering 15.2 percent of the oil using their new and simple nanofluid at that concentration – comparable to chemical methods and about three times more efficient than other nanofluids.

Source: http://www.uh.edu/

Hydrogen Fuel Stations

A Stanford University research lab has developed new technologies to tackle two of the world’s biggest energy challenges – clean fuel for transportation and grid-scale energy storageHydrogen fuel has long been touted as a clean alternative to gasoline. Automakers began offering hydrogen-powered cars to American consumers last year, but only a handful have sold, mainly because hydrogen refueling stations are few and far between.

silicone nanoconesStanford engineers created arrays of silicon nanocones to trap sunlight and improve the performance of solar cells made of bismuth vanadate

Millions of cars could be powered by clean hydrogen fuel if it were cheap and widely available,” said Yi Cui, associate professor of materials science and engineering at Stanford.

Unlike gasoline-powered vehicles, which emit carbon dioxide, hydrogen cars themselves are emissions free. Making hydrogen fuel, however, is not emission free: Today, making most hydrogen fuel involves natural gas in a process that releases carbon dioxide into the atmosphere.

To address the problem, Cui and his colleagues have focused on photovoltaic water splitting. This emerging technology consists of a solar-powered electrode immersed in water. When sunlight hits the electrode, it generates an electric current that splits the water into its constituent parts, hydrogen and oxygen. Finding an affordable way to produce clean hydrogen from water has been a challenge. Conventional solar electrodes made of silicon quickly corrode when exposed to oxygen, a key byproduct of water splitting. Several research teams have reduced corrosion by coating the silicon with iridium and other precious metals.
The researchers described their findings in two studies published this month in the journals Science Advances and Nature Communications. 

Writing in the June 17 edition of Sciences Advances, Cui and his colleagues presented a new approach using bismuth vanadate, an inexpensive compound that absorbs sunlight and generates modest amounts of electricity.

Bismuth vanadate has been widely regarded as a promising material for photoelectrochemical water splitting, in part because of its low cost and high stability against corrosion,” said Cui, who is also an associate professor of photon science at SLAC National Accelerator Laboratory. “However, the performance of this material remains well below its theoretical solar-to-hydrogen conversion efficiency.”

Bismuth vanadate absorbs light but is a poor conductor of electricity. To carry a current, a solar cell made of bismuth vanadate must be sliced very thin, 200 nanometers or less, making it virtually transparent. As a result, visible light that could be used to generate electricity simply passes through the cell.

To capture sunlight before it escapes, Cui’s team turned to nanotechnology. The researchers created microscopic arrays containing thousands of silicon nanocones, each about 600 nanometers tall.

Nanocone structures have shown a promising light-trapping capability over a broad range of wavelengths,” Cui explained. “Each cone is optimally shaped to capture sunlight that would otherwise pass through the thin solar cell.”

In the experiment, Cui and his colleagues deposited the nanocone arrays on a thin film of bismuth vanadate. Both layers were then placed on a solar cell made of perovskite, another promising photovoltaic material.

When submerged, the three-layer tandem device immediately began splitting water at a solar-to-hydrogen conversion efficiency of 6.2 percent, already matching the theoretical maximum rate for a bismuth vanadate cell.

Source: http://news.stanford.edu/

Algae To Power Jets

Aviation giant Airbus hope algae could one day help power jets – and help airlines cut their C02 emissions. They’re working with the Munich Technical University (Germany) to cultivate the photosynthetic organisms in this lab. Algae here is cultivated in water with a salt content of 6-9 percent. A combination of light and carbon dioxide does the rest.

biofuel planesCLICK ON THE IMAGE TO ENJOY THE VIDEO

Primarily you need obviously algae cells that are able to generate fats and oils. In combination with CO2 and light these algae cells propagate and form algae biomass and under certain cultivation conditions, for example the lack of nitrogen in the cultivation media, these algae cells accumulate fats and oils in their cell mass and this can reach up to 50 to 70 percent of the total cell weight. That is quite a lot and once you formed that fat and oil you can actually extract it from the cell and convert it over a chemical process“, says  Thomas Brueck, Professor at Munich Technical University (TUM). In these open tanks algae grows 12 times faster than plants cultivated on soil, producing an oil yield 30 times that of rapeseed.

Algae fuel today is still in the state of research so today, we could probably not offer it at costs which are realistic to run an airline. But we are sure that over time, we will make it possible to offer kerosine made of algae for a competitive price“, comments Gregor von Kursell, Airbus Group Spokesman. The company says the project remains in its infancy. Researchers believe biofuel from algaculture could provide up to 5 percent of jetfuel needs by around 2050.

Source: http://www.reuters.com/

Nanotechnologies Boost Electric Car Batteries

On a drizzly, gray morning in April, Yi Cui weaves his scarlet red Tesla in and out of Silicon Valley traffic. Cui, a materials scientist at Stanford University here, is headed to visit Amprius, a battery company he founded 6 years ago. It’s no coincidence that he is driving a battery-powered car, and that he has leased rather than bought it. In a few years, he says, he plans to upgrade to a new model, with a crucial improvement: “Hopefully our batteries will be in it.” Cui and Amprius are trying to take lithium–ion batteries—today’s best commercial technology—to the next level. They have plenty of company. Massive corporations such as Panasonic, Samsung, LG Chem, Apple, and Tesla are vying to make batteries smaller, lighter, and more powerful. But among these power players, Cui remains a pioneering force.
Unlike others who focus on tweaking the chemical composition of a battery’s electrodes or its charge-conducting electrolyte, Cui is marrying battery chemistry with nanotechnology. He is building intricately structured battery electrodes that can soak up and release charge-carrying ions in greater quantities, and faster, than standard electrodes can, without producing troublesome side reactions.

Tesla Model 3

“He’s taking the innovation of nanotechnology and using it to control chemistry,” says Wei Luo, a materials scientist and battery expert at the University of Maryland, College Park.
In a series of lab demonstrations, Cui has shown how his architectural approach to electrodes can domesticate a host of battery chemistries that have long tantalized researchers but remained problematic. Among them: lithium-ion batteries with electrodes of silicon instead of the standard graphite, batteries with an electrode made of bare lithium metal, and batteries relying on lithium-sulfur chemistry, which are potentially more powerful than any lithium-ion battery. The nanoscale architectures he is exploring include silicon nanowires that expand and contract as they absorb and shed lithium ions, and tiny egglike structures with carbon shells protecting lithium-rich silicon yolks.

Source: http://www.sciencemag.org/

3D Printed Office

In Dubai the first fully 3D-printed and completely functional building has not only been built but has celebrated its grand opening, marking an architectural and engineering breakthrough. The prototype 3D-printed office building, with floorspace is about 2,700 square feet (250 m2).

UAE-Dubai-Office-of-the-Future-

The office has all the amenities of traditionally constructed structures, such as electricity, water, telecommunications, and air conditioning. The office is also outfitted with a number of energy saving features, including window shades to protect from Dubai’s blazing sun. In order to create all the pieces needed for the office, builders used a 3D printer measuring 20 feet high, 120 feet long, and 40 feet wide. Aside from the equipment, it took a very small team of workers to put the office together. Seven installers and 10 electricians and specialists worked together to assemble the fully functional office in just 17 days. Dubai’s media office estimates this represents a 50 percent cost savings in labor alone compared to buildings of similar size built with conventional methods. In Dubai 25% of the buildings should be 3D printed by 2030, says ruler.

Source: http://inhabitat.com/

Nanotechnology Boosts Solar Panel Efficiency

Solar power, which is power drawn from the sun, is a familiar concept for most Americans. You set out some thick, flat arrays the color of blueberries in your lawn or on your roof, and they use the photovoltaic effect to generate a current. For many people, this means they can expect to spend less on energy from nonrenewable sources like oil and gas, with the added benefit of reducing carbon emissions in the long run. The benefits for developing nations are even greater. Take Africa, for example. As a continent, it is extremely sunny and flat so it seems like a natural place to deploy solar panels. The main barriers preventing this rollout are the cost of cell production and limitations on cell efficiency.

solar farm

Fortunately, research costs for solar energy are comparatively lower than other fields. This has led to scientists coming up with a number of inventive ways to improve solar cells through the use of nanotechnology.
Nanotechnology refers to manmade matter measuring between 1 and 100 nanometers (nm). For reference, a sheet of paper is 100,000 nm, while a strand of hair is 80,000 nm. Due to their size and extreme variety, nanotechnology allows scientists to create microscopic components and enhance the performance of existing technologies. For example, electroplating solar panels with nanometers-thin layers of silver helps the system absorb heat and makes it resistant to corrosion. Hinging on the size and versatility of nanotechnology, scientists have discovered several different ways to leverage it to improve solar cells.

The amount of energy solar cell panels can produce is limited in part by the sunlight it collects. If the array can collect more sunlight while still taking up the same amount of space, the energy produced per panel will increase. This would have a profound effect on arrays in places like Africa, where it is extremely sunny. The increase in surface area would mean a greater amount of energy collected and output over the lifetime of the cell. Using nanotechnology, scientists have developed a way to do just this.

The actual product is called a dye-sensitive solar cell. It uses a layer of porous nanoparticles coated in dye to increase the surface area on the solar cell on a microscopic level. This has the added benefit of making the cell more flexible, and increasing its ability to work in extreme conditions. If that seems difficult to imagine, think about it this way: Picture a long strip of candy dots. The paper is the solar array while the candy is the layer of nanoparticles. The candy increases the surface area of the paper without adding much bulk. Thus, the paper remains supple. Some of the greatest advances in flexible solar cells have been made by Alberta scientist Jillian Buriak. Using a spray gun and laminators, Buriak and her team developed a way to spray nanoparticles onto the plastic. This sheet is then run through the laminator, which spreads out the layer even further. The result is an extremely thin solar cell with innumerable practical applications.

Using nanotechnology, scientists have discovered that they can create cells that absorb 90 percent of the sunlight that hits it. This allows for more efficient concentrating solar power (CSP) plants. Unlike traditional solar arrays, CSP plants generate power by focusing the sun, generally through mirrors, on molten salt. The heated salt is used to create steam to turn a turbine and generate electricity. One limitation of these plants is that the materials used to collect the sunlight degrade after about a year, causing a dip in production while they are repaired.

This new technology can withstand extreme heat and last for many years outdoors, despite exposure to the elements.

Source: http://africanbrains.net/

Electric Car: New Hydrogen Filling Station

A new hydrogen filling station is open to the public in London It creates the gas on site from tap water and renewable energy — a first for the British capital. The station uses electricity generated from renewable sources such as wind power to split water into hydrogen and oxygen. The whole facility can also be switched on and off by the power company to help them balance demand on the grid. Green power company ITM says it helps the problem of what to do with the UK’s excess renewable energy.

Tucson fuel cellCLICK ON THE IMAGE TO ENJOY THE VIDEO

You can re-fuel it in 3 minutes and it will go over three hundred miles (483 km). They are the limitations of a plug-in electric vehicle. You also export the energy from the power grid in a much more effective way,” says Dr Graham Cooley,  ITM Chief Executive.

Refuelling at the site fills the tank with 5kg of pressurised hydrogen which costs around of £10 per kilogram (12,7 euros or 14,5 Dollars), giving a range of around 300 miles. Three different models of hydrogen-powered cars are available in the UK at present, including the Hyundai ix35, though only a handful of people actually drive them.

The issue is dispensing it and delivering it to vehicles which is what we see here today in terms of the new infrastructure being developed. It’s the delivery of the fuel and it’s a relatively straightforward process to do it,”  comments Jon Hunt from the company Toyota.

The technology is still nascent — and, like the cars, hydrogen filling stations remain relatively scarce across Europe. But there are set to be 12 open across the UK by the end of next year.

Source:  https://en.wikipedia.org/

Sensor Detects Harmful Air Pollution In The Home

Scientists from the University of Southampton (UK) in partnership with the Japan Advanced Institute of Science and Technology (JAIST) have developed a graphene-based sensor and switch that can detect harmful air pollution in the home with very low power consumptionThe sensor detects individual CO2 molecules and volatile organic compounds (VOC) gas molecules found in building and interior materials, furniture and even household goods, which adversely affect our living in modern houses with good insulation. These harmful chemical gases have low concentrations of ppb (parts per billion) levels and are extremely difficult to detect with current environmental sensor technology, which can only detect concentrations of parts per million (ppm).

Graphene sensor.jpg_SIA_JPG_fit_to_width_INLINE

In recent years, there has been an increase in health problems due to air pollution in personal living spaces, known as sick building syndrome (SBS), along with other conditions such as sick car and sick school syndromes.

The research group, led by Professor Hiroshi Mizuta, who holds a joint appointment at the University of Southampton and JAIST, and Dr Jian Sun and Assistant Professor Manoharan Muruganathan of JAIST, developed the sensor to detect individual CO2 molecules adsorbed (the bond of molecules from a gas to a surface) onto the suspended graphene (single atomic sheet of carbon atoms arranged in a honeycomb-like hexagonal crystal lattice structure) one by one by applying an electric field across the structure.

By monitoring the electrical resistance of the graphene beam, the adsorption and desorption (whereby a substance is released from or through a surface) processes of individual CO2 molecules onto the graphene were detected as ‘quantisedchanges in resistance (step-wise increase or decrease in resistance). In the study, published today in Science Advances, the journal of the American Association for the Advancement of Science (AAAS), a small volume of  CO2 gas (equivalent to a concentration of approximately 30 ppb) was released and the detection time was only a few minutes.

Professor Mizuta said: “In contrast to the commercially available environmental monitoring tools, this extreme sensing technology enables us to realise significant miniaturisation, resulting in weight and cost reduction in addition to the remarkable improvement in the detection limit from the ppm levels to the ppb levels“.

Source: http://www.southampton.ac.uk/

Hydrogen Electric Car Powered By Fuel Cells 4 Times More Efficient

Inspired by the humble cactus, a new type of membrane has the potential to significantly boost the performance of fuel cells and transform the electric vehicle industry. The membrane, developed by scientists from CSIRO (Australia) and Hanyang University in Korea, was described today in the journal Nature . The paper shows that in hot conditions the membrane, which features a water repellent skin, can improve the efficiency of fuel cells by a factor of four.

According to CSIRO researcher and co-author Dr Aaron Thornton, the skin works in a similar way to a cactus plant, which thrives by retaining water in harsh and arid environments.

cactus

Fuel cells, like the ones used in electric vehicles, generate energy by mixing together simple gases, like hydrogen and oxygen. However, in order to maintain performance, proton exchange membrane fuel cells – or PEMFCs – need to stay constantly hydrated,” Dr Thornton said.

At the moment this is achieved by placing the cells alongside a radiator, water reservoir and a humidifier. The downside is that when used in a vehicle, these occupy a large amount of space and consume significant power,” he added.

According to CSIRO researcher and co-author Dr Cara Doherty, the team’s new cactus-inspired solution offers an alternative. A cactus plant has tiny cracks, called stomatal pores, which open at night when it is cool and humid, and close during the day when the conditions are hot and arid. This helps it retain water,” Dr Doherty said. “This membrane works in a similar way. Water is generated by an electrochemical reaction, which is then regulated through nano-cracks within the skin. The cracks widen when exposed to humidifying conditions, and close up when it is drier. This means that fuel cells can remain hydrated without the need for bulky external humidifier equipment. We also found that the skin made the fuel cells up to four times as efficient in hot and dry conditions,” she added.

Professor Young Moo Lee from Hanyang University, who led the research, said that this could have major implications for many industries, including the development of electric vehicles.

Source: http://www.csiro.au/

Friendly Alternative To Li-Ion Battery

An unexpected discovery has led to a rechargeable battery that’s as inexpensive as conventional car batteries, but has a much higher energy density. The new battery could become a cost-effective, environmentally friendly alternative for storing renewable energy and supporting the power grid.

A team based at the Department of Energy’s Pacific Northwest National Laboratory (PNNL) identified this energy storage gem after realizing the new battery works in a different way than they had assumed. The journal Nature Energy published a paper today that describes the battery.

PNNL batteryPNNL’s improved aqueous zinc-manganese oxide battery offers a cost-effective, environmentally friendly alternative for storing renewable energy and supporting the power grid.

“The idea of a rechargeable zinc-manganese battery isn’t new; researchers have been studying them as an inexpensive, safe alternative to lithium-ion batteries since the late 1990s,” said PNNL Laboratory Fellow Jun Liu, the paper’s corresponding author. “But these batteries usually stop working after just a few charges. Our research suggests these failures could have occurred because we failed to control chemical equilibrium in rechargeable zinc-manganese energy storage systems.”

After years of focusing on rechargeable lithium-ion batteries, researchers are used to thinking about the back-and-forth shuttle of lithium ions. Lithium-ion batteries store and release energy through a process called intercalation, which involves lithium ions entering and exiting microscopic spaces in between the atoms of a battery’s two electrodes.

This concept is so engrained in energy storage research that when PNNL scientists, collaborating with the University of Washington, started considering a low-cost, safe alternative to lithium-ion batteries − a rechargeable zinc-manganese oxide battery − they assumed zinc would similarly move in and out of that battery’s electrodes. After a battery of tests, the team was surprised to realize their device was undergoing an entirely different process. Instead of simply moving the zinc ions around, their zinc-manganese oxide battery was undergoing a reversible chemical reaction that converted its active materials into entirely new ones.

Source: http://www.pnnl.gov/

How To Harvest Heat In The Dark To Produce Electricity

Physicists have discovered radical new properties in a nanomaterial, opening new possibilities for highly efficient thermophotovoltaic cells that could one day harvest heat in the dark and turn it into electricity. The research team from the Australian National University (ANU/ARC Centre of Excellence CUDOS) and the University of California Berkeley demonstrated a new artificial material, or metamaterial, that glows in an unusual way when heated.

The findings could drive a revolution in the development of cells which convert radiated heat into electricity, known as thermophotovoltaic cells. “Thermophotovoltaic cells have the potential to be much more efficient than solar cells,” said Dr Sergey Kruk from the ANU Research School of Physics and Engineering.

thermophotovoltaic

Our metamaterial overcomes several obstacles and could help to unlock the potential of thermophotovoltaic cells.”

Thermophotovoltaic cells have been predicted to be more than twice as efficient as conventional solar cells. They do not need direct sunlight to generate electricity, and instead can harvest heat from their surroundings in the form of infrared radiation. They can also be combined with a burner to produce on-demand power or can recycle heat radiated by hot engines. The team’s metamaterial, made of tiny nanoscopic structures of gold and magnesium fluoride, radiates heat in specific directions. The geometry of the metamaterial can also be tweaked to give off radiation in specific spectral range, in contrast to standard materials that emit their heat in all directions as a broad range of infrared wavelengths. This makes the new material ideal for use as an emitter paired with a thermophotovoltaic cell.

The project started when Dr Kruk predicted the new metamaterial would have these surprising properties. The ANU team then worked with scientists at the University of California Berkeley, who have unique expertise in manufacturing such materials.

To fabricate this material the Berkeley team were operating at the cutting edge of technological possibilities,” Dr Kruk said. “The size of an individual building block of the metamaterial is so small that we could fit more than 12,000 of them on the cross-section of a human hair.

The research is published in Nature Communications.

Source: http://www.anu.edu.au/