Solar Energy Transforms Salt Water Into Fresh Drinking Water

A federally funded research effort to revolutionize water treatment has yielded an off-grid technology that uses energy from sunlight alone to turn salt water into fresh drinking water. The desalination system, which uses a combination of membrane distillation technology and light-harvesting nanophotonics, is the first major innovation from the Center for Nanotechnology Enabled Water Treatment (NEWT), a multi-institutional engineering research center based at Rice University.

NEWT’s “nanophotonics-enabled solar membrane distillation” technology, or NESMD, combines tried-and-true water treatment methods with cutting-edge nanotechnology that converts sunlight to heat. More than 18,000 desalination plants operate in 150 countries, but NEWT’s desalination technology is unlike any other used today.

Direct solar desalination could be a game changer for some of the estimated 1 billion people who lack access to clean drinking water,” said Rice scientist and water treatment expert Qilin Li, a corresponding author on the study. “This off-grid technology is capable of providing sufficient clean water for family use in a compact footprint, and it can be scaled up to provide water for larger communities.”

The technology is described online in the Proceedings of the National Academy of Sciences.


Clean Renewable Source Of Hydrogen Fuel For Electric Car

Rice University scientists have created an efficient, simple-to-manufacture oxygen-evolution catalyst that pairs well with semiconductors for solar water splitting, the conversion of solar energy to chemical energy in the form of hydrogen and oxygen.

anode RiceA photo shows an array of titanium dioxide nanorods with an even coating of an iron, manganese and phosphorus catalyst. The combination developed by scientists at Rice University and the University of Houston is a highly efficient photoanode for artificial photosynthesis. Click on the image for a larger version

The lab of Kenton Whitmire, a Rice professor of chemistry, teamed up with researchers at the University of Houston and discovered that growing a layer of an active catalyst directly on the surface of a light-absorbing nanorod array produced an artificial photosynthesis material that could split water at the full theoretical potential of the light-absorbing semiconductor with sunlight. An oxygen-evolution  catalyst splits water into hydrogen and oxygen. Finding a clean renewable source of hydrogen fuel is the focus of extensive research, but the technology has not yet been commercialized.

The Rice team came up with a way to combine three of the most abundant metalsiron, manganese and phosphorus — into a precursor that can be deposited directly onto any substrate without damaging it. To demonstrate the material, the lab placed the precursor into its custom chemical vapor deposition (CVD) furnace and used it to coat an array of light-absorbing, semiconducting titanium dioxide nanorods. The combined material, called a photoanode, showed excellent stability while reaching a current density of 10 milliamps per square centimeter, the researchers reported.

The results appear in two new studies. The first, on the creation of the films, appears in Chemistry: A European Journal. The second, which details the creation of photoanodes, appears in ACS Nano.


Solar Panels Reach 36.4 Percent Efficiency

Swiss start-up Insolight says its solar panels double the yield achieved by other sun-powered technology. In independent tests the panels reached an efficiency of 36.4 percent.


Traditionally the market sits at around 18 percent and we can double this. Therefore we can double the return on investment for the final client….Our key innovation is that you do not need to rotate the panel in order to follow the sun. We can follow the sun in a flat manner, like any other solar panel, which makes it that our panel can be installed on standard rooftops, with standard mounting technology,” says Florian Gerlich Co-Founder of Insolight company.

Tiny square super cells capture all of the sun’s rays, underneath round lenses, using a patented microtracking system. “Why micro? Why tracking? Micro is a really really small movement that is encapsulated into the solar panel and tracking is to track the sun to concentrate the light into our really tiny solar cell,” comments Noe Bory from Insolight.  An injection-moulded transparent plate moves one centimetre throughout the day, a small sensor detecting the sun’s position.

“As you see here the small squares spread out over the whole surface and under each of these lenses there is a small solar cell. It’s a bit like the lenses that you’re using in your reading lenses or your reading glasses. It’s the same technology, it’s just a particular shape in order to be able to follow the sun from morning to the evening,” adds Florian Gerlich.

The panels may be more expensive to buy than current technology. But Insolight says energy prices will be slashed from 14 US cents per kilowatt hour to 9 cents. A large bed of panels will be tested in Lausanne this summer. Insolight says the system could be market-ready next year.

Very Cheap Long-Lasting Batteries

Chemists at the University of Waterloo (Canada) have developed a long-lasting zinc-ion battery that costs half the price of current lithium-ion batteries and could help enable communities to shift away from traditional power plants and into renewable solar and wind energy production. Professor Linda Nazar and her colleagues from the Faculty of Science at Waterloo made the important discovery, which appears in the journal, Nature Energy.

The battery uses safe, non-flammable, non-toxic materials and a pH-neutral, water-based salt. It consists of a water-based electrolyte, a pillared vanadium oxide positive electrode and an inexpensive metallic zinc negative electrode. The battery generates electricity through a reversible process called intercalation, where positively-charged zinc ions are oxidized from the zinc metal negative electrode, travel through the electrolyte and insert between the layers of vanadium oxide nanosheets in the positive electrode. This drives the flow of electrons in the external circuit, creating an electrical current. The reverse process occurs on charge.

The cell represents the first demonstration of zinc ion intercalation in a solid state material that satisfies four vital criteria: high reversibility, rate and capacity and no zinc dendrite formation. It provides more than 1,000 cycles with 80 per cent capacity retention and an estimated energy density of 450 watt-hours per litre. Lithium-ion batteries also operate by intercalation—of lithium ions—but they typically use expensive, flammable, organic electrolytes.

zinc-ion batteries

The worldwide demand for sustainable energy has triggered a search for a reliable, low-cost way to store it,” said Nazar, a University Research Professor in the Department of Chemistry. “The aqueous zinc-ion battery we’ve developed is ideal for this type of application because it’s relatively inexpensive and it’s inherently safe.”



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.


Solar Cells: How To Transform More Solar Energy Into Electricity

Sagrario Domínguez-Fernández, a Spanish telecommunications engineer at CEMITEC, has managed to increase light absorption in silicon by means of nanostructures etched onto photovoltaic cells. This increases the efficiency obtained in these electronic devices which are made of this element and which transform solar energy into electricity.
solar cells

Over 30 percent of the sunlight that strikes a silicon is reflected, which means it cannot be used in the photoelectric conversion,” explained Sagrario Domínguez. “Because the nanostructures on the surface of a material have dimensions in the light wavelength range, they interfere with the surface in a particular way and allow the amount of reflected light to be modified.”

Sagrario Domínguez designed and optimised structures on a nanometric scaleto try and find one that would minimise the reflectance [ability of a surface to reflect light] of the silicon in the wavelength range in which solar cells function.” In their manufacturing process, she resorted to what is known as laser interference lithography which consists of applying laser radiation to a photo-sensitive material to create structures on a nanometric scale. Specifically, she used polished silicon wafers to which she gave the shape of cylindrical pillar and obtained a 77 percent reduction in the reflectance of this element.

Sagrario Domínguez then went on to modify the manufacturing processes to produce the nanostructures on the silicon substrates used in commercial solar cells. “These substrates have dimensions and a surface roughness that makes them, ‘a priori’, unsuitable for processes,” pointed out the researcher. Having overcome the difficulties, she incorporated nanostructures onto following the standard processes of the photovoltaics industry. “According to the literature, this is the first time that it has been possible to manufacture periodic nanostructures; they are the ones that on the surface of a material are continuously repeated on substrates of this type, and therefore, the first standard solar cell with periodic nanostructures,” pointed out the new MIT PhD holder. The efficiency obtained is 15.56 percent, which is a very promising value when compared with others included in the literature.


Solar Hubs Provide Clean Water, Electricity & Internet to 3000 people

The Italian company Watly aims to deliver a hat trick of very needful things to the developing world, in the form of both a standalone unit and as a network of units. The team of this ambitious company describes their creation as the “biggest solar-powered computer in the world,” which combines solar photovoltaics (PV) and battery storage for powering the unit (and for charging external devices), with a water filtration system and an internet connectivity and telecommunications hub. The Watly system, which has been in the works for the last few years, and has now attracted the attention of The Discovery Channel, was run as a pilot program at a village in Ghana, where the 2.0 version of the device was successfully deployed to deliver clean drinking water to residents.

watly solar hub

The next step, however, is to build out the Watly 3.0 system, which is the full-sized version of the device, measuring some 40 meters long, and which is expected to be able to provide as much as 5000 liters of water per day, every day, for at least 15 years, along with producing solar electricity and charging services to as many as 3000 people. According to the company, one unit could offset the emissions equivalent of 2500 barrels of oil over the course of those 15 years, along with providing clean water and an off-grid power source. To get to that next step, Watly has turned to – wait for it – crowdfunding with an Indiegogo campaign that seeks to raise money for the installation of the 3.0 version as a pilot program in Africa (location TBD).

Along with the solar power and drinking water, Watly aims to provide an internet/telecom hub for local residents, with an onboard system for connecting to 3G/4G, radio link data systems, and/or satellites, as well as to communicate with other Watly units to act as a node in an “EnergyNet.”

Watly is a powerful communication device that can collect and send any kind of data (videos, images, audios, texts, ratios, etc.) to the Internet as well as to any other compatible communication device. A single Watly is a standing alone machine, but two or more Watlys become a network where each node is auto-powered, self-sustained and multi-functional.


Nanoparticles Activated By Solar Energy Boil Water

Young researchers created a superconducting heat ink that functions as a solar heater. It heats water up to 68 degrees Celsius and is 40 percent cheaper than commercial inks.

hot shower 2

A pipe exposed to the sun reaches a temperature of 40 C°, if we add the superconducting ink the temperature increases 70 percent and reaches 68 C°,” says Sandra Casillas Bolaños, master at the Technological Institute of the Lagoon (ITL), in north of Mexico, and head of the project.

She explains that the ink acts as a boiler that contains nanoparticles activated by solar energy and increasing the temperature.


The ink is made of two layers, the first is an internal magnetic titanium nanoparticle, which is responsible for trapping the heat and the second is external and consists of a coating of tungsten (filament in light bulbs) which researchers transform into a nano salt and adhere with polyvinyl alcohol, to finish with a layer of copper.

Casillas Bolaños states that by a treatment called burnishing copper blackens in order that trap and retain heat inside the particles. “Thus the center is heated more intensely: first the titanium, then tungsten and finally the copper“.

The project has been developed for two years and the product is classified as an ink because it uses a series of solvents making it fast drying and with an odor similar to hair dye. The ink is applied on the surface of a conventional pipe that carries water and to potentiate the heat, students working on the project with professor Casillas Bolaños in the nonmetallic materials field, put two layers of PET bottles over the tubes in order to create a greenhouse effect and raise the temperature faster, as well as protect the ink from outdoor wear.

The technology has been implemented in some houses, where, by flowing for five meters water at 68 C° is obtained instantly, and even in cloudy weather the ink nicely captures the heat. Sandra Casillas adds that the ink was implemented in a major sports complex of the city to heat the pool, where two million cubic meters of water are heated from 26 to 37 C°. To achieve this, the researcher and her team placed tubes covered with ink on the edge of the indoor pool and a pump pulls the liquid from seven o’clock until the sun sets. As it flows, the water is heated and reaches the ideal temperature.

The ink is in the process of patenting and is intended to be market at 600 pesos a liter (about 40 dollars); however, for house piping only 150 pesos (10 dollars) are invested because very little is needed, says Casillas Bolaños.


Solar Cell: How To Boost Perovskites Performance

One of the fastest-growing areas of solar energy research is with materials called perovskites. These promising light harvesters could revolutionize the solar and electronics industries because they show potential to convert sunlight into electricity more efficiently and less expensively than today’s silicon-based semiconductors. These superefficient crystal structures have taken the scientific community by storm in the past few years because they can be processed very inexpensively and can be used in applications ranging from solar cells to light-emitting diodes (LEDs) found in phones and computer monitors.
A new study published online in the journal Science by University of Washington (UW) and University of Oxford researchers demonstrates that perovskite materials, generally believed to be uniform in composition, actually contain flaws that can be engineered to improve solar devices even further.
peroskite solar cell
Perovskites are the fastest-growing class of photovoltaic material over the past four years,” said lead author Dane deQuilettes, a UW doctoral student working with David Ginger, professor of chemistry and associate director of the UW Clean Energy Institute.

In that short amount of time, the ability of these materials to convert sunlight directly into electricity is approaching that of today’s silicon-based solar cells, rivaling technology that took 50 years to develop,” deQuilettes said. “But we also suspect there is room for improvement.”

Perovskite solar cells have so far have achieved efficiencies of roughly 20 percent, compared to about 25 percent for silicon-based solar cells. The team found “dark” or poorly performing regions of the perovskite material at intersections of the crystals. In addition, they discovered that they could “turn on” some of the dark areas by using a simple chemical treatment.

Bionic Particles To Turn Sunlight Into Fuel

Inspired by fictional cyborgs like Terminator, a team of researchers at the University of Michigan and the University of Pittsburgh has made the first bionic particles from semiconductors and proteins. These particles recreate the heart of the process that allows plants to turn sunlight into fuel.

Human endeavors to transform the energy of sunlight into biofuels using either artificial materials or whole organisms have low efficiency,” said Nicholas Kotov, the Florence B. Cejka Professor of Engineering at the University of Michigan, who led the experiment. A bionic approach could change that. The bionic particles blend the strengths of inorganic materials, which can readily convert light energy to electron energy, with biological molecules whose chemical functions have been highly developed through evolution. The team first designed the particles to combine cadmium telluride, a semiconductor commonly used in solar cells, with cytochrome C, a protein used by plants to transport electrons in photosynthesis. With this combination, the semiconductor can turn a ray from the sun into an electron, and the cytochrome C can pull that electron away for use in chemical reactions that could clean up pollution or produce fuel, for instance. U-M‘s Sharon Glotzer, the Stuart W. Churchill Professor of Chemical Engineering, who led the simulations, compares the self-assembly to the way that the surfaces of living cells form, using attractive forces that are strong at small scales but weaken as the structure grows. Kotov’s group confirmed that the semiconductor particles and proteins naturally assemble into larger particles, roughly 100 nanometers (0.0001 millimeters) in diameter.

We merged biological and inorganic in a way that leverages the attributes of both to get something better than either alone,” Glotzer said. Powered by electrons from the cytochrome C, the enzyme could remove oxygen from nitrate molecules. Like the structures that accomplish photosynthesis in plants, the bionic particles took a beating from handling the energy. Nature constantly renews these working parts in plants, and through self-assembly, the particles may also be able to renew themselves.

Solar Cells Used As Lasers

A relatively new type of solar cell based on a perovskite material – named for scientist Lev Perovski, who first discovered materials with this structure in the Ural Mountains in the 19th century – was recently pioneered by an Oxford research team led by Professor Henry Snaith. Commercial silicon-based solar cells – such as those seen on the roofs of houses across the country – operate at about 20% efficiency for converting the Sun’s rays into electrical energy. It’s taken over 20 years to achieve that rate of efficiency. Latest research finds that the trailblazing ‘perovskite’ material used in solar cells can double up as a laser, strongly suggesting the astonishing efficiency levels already achieved in these cells is only part of the journey. Scientists have demonstrated potential uses for this material in telecommunications and for light emitting devices.

Perovskite solar cells, the source of huge excitement in the research community, already lie just a fraction behind commercial silicon, having reached a remarkable 17% efficiency after a mere two years of research – transforming prospects for cheap large-area solar energy generation.
Now, researchers from Professor Sir Richard Friend’s group at Cambridge’s Cavendish Laboratory – working with Snaith’s Oxford group – have demonstrated that perovskite cells excel not just at absorbing light but also at emitting it. The new findings, recently published online in the Journal of Physical Chemistry Letters, show that these ‘wonder cells’ can also produce cheap lasers. By sandwiching a thin layer of the lead halide perovskite between two mirrors, the team produced an optically driven laser which proves these cells “show very efficient luminescence” – with up to 70% of absorbed light re-emitted.


How To Tap The Sun’s Energy Through Heat

A new approach to harvesting solar energy, developed by MIT researchers, could improve efficiency by using sunlight to heat a high-temperature material whose infrared radiation would then be collected by a conventional photovoltaic cell. This technique could also make it easier to store the energy for later use, the researchers say. In this case, adding the extra step improves performance, because it makes it possible to take advantage of wavelengths of light that ordinarily go to waste.

A conventional silicon-based solar celldoesn’t take advantage of all the photons,” explains associate professor of mechanical engineering Evelyn Wang,. That’s because converting the energy of a photon into electricity requires that the photon’s energy level match that of a characteristic of the photovoltaic (PV) material called a bandgap. Silicon’s bandgap responds to many wavelengths of light, but misses many others. This basic concept has been explored for several years, since in theory such solar thermophotovoltaic (STPV) systems could provide a way to circumvent a theoretical limit on the energy-conversion efficiency of semiconductor-based photovoltaic devices. That limit, called the Shockley-Queisser limit, imposes a cap of 33.7 percent on such efficiency, but Wang says that with TPV systems, “the efficiency would be significantly higher — it could ideally be over 80 percent.
nanophotonic solar photovoltaicNanophotonic solar thermophotovoltaic device

Zhuomin Zhang, a professor of mechanical engineering at the Georgia Institute of Technology who was not involved in this research, says, “This work is a breakthrough in solar thermophotovoltaics, which in principle may achieve higher efficiency than conventional solar cells because STPV can take advantage of the whole solar spectrum. … This achievement paves the way for rapidly boosting the STPV efficiency.

The process is described in a paper published this week in the journal Nature Nanotechnology.