Jean-Luc Soullier, holder of Fédération Aéronautique Internationale records for speed and altitude in an aircraft almost lighter than its pilot, has a greater series of ambitions to expand the range and speed of electric aircraft. Having stretched the limits of his Colomban MC-30e with two different motors, he’s looking at a longer-spanned, cleaner aircraft – the Windward Performance Duckhawk – as a means of getting higher speed and much longer range for a truly formidable (tres formidable) crossing of the Atlantic Ocean, not once, but twice. The airplane, with a Rotex motor on the nose and a specially-designed Arplast three-bladed propeller, will weigh a mere 105 kilograms (231 pounds) empty – without batteries. This is considerably less than the lightest Duckhawk in standard form, and shows that designer Greg Cole and Jean-Luc are making room for the added weight of long-range energy storage. Since the original airplane manages +7.5/-5 g’s, the lighter version will be restricted to a never-exceed velocity …
Solar Impulse 2 Ready to Take on the World
Even while the first Solar Impulse was scaling the Alps, traversing the Moroccan desert, and crossing America, skilled craftsmen and women were designing and building Solar Impulse 2, a larger, heavier solar-powered airplane rolled out this week. Its next challenge, that of flying around the world, will test the limits of even this seasoned team. As shown on the first Solar Impulse’s flights, “Flying the Solar Impulse aircraft is quite different from being at the commands of any other airplane. Flight tactics, piloting skills, aerodynamics had to be re-learned from scratch.” Part of the difference comes from the aircraft’s huge size and light weight. Solar Impulse shares this: “Here’s a fun fact for you to understand how special this aircraft is: the wingspan of Si2 is bigger than that of a Boeing 747, but the former’s weight is just slightly more than 1% of the latter (remember: the weight of a car)!” This jumbo-jet sized craft has all the performance of …
Solar Cells a Few Atoms Thick
Researchers at the Vienna University of Technology have come up with a way to create one-atom thick, flexible, semi-transparent solar cells. Instead of the graphene often touted as a means toward such an end, however, the scientists have turned to atom-thick layers of tungsten diselenide for their wonder material. Experiments show that ultrathin layers of tungsten and selenium may have properties that would make them applicable even to electric aircraft use – if they can capture a significant amount of energy – or at least as much as thin-film silicon cells can. Graphene has been a popular favorite since its Russian “discoverers” were awarded the Nobel Prize in physics in 2010. One of the strongest materials, graphene can manage stresses and strains better than most and has “great opto-electronic properties.” Its atomic-scale thinness allows it to transform optical signals into electronic pulses extremely quickly. Despite these outstanding characteristics, “The electronic states are not very practical for creating photovoltaics,” according to …
Solar Cells Collect More Light, Display Art
Friend and frequent contributor Colin Rush sent this Economist item about Semprius, a concentrating solar cell maker about to go into production with their highly efficient technology. It’s big news that a production solar panel is able to convert 42.5 percent of sunlight falling on it into energy, when the world’s record for any solar cell was set last September by the German Fraunhofer Institute for Solar Energy Systems with an experimental multi-junction solar cell that’s 44.7 percent efficient. The 42.5 percent for Semprius cells drops to about 35 percent when they are surrounded by the normal mounting flanges and connecting lines – still well above most production panels. These may achieve 50 percent with suitable refinement. Using breakthroughs devised by John Rogers of the University of Illinois, Urbana-Champaign, Semprius is able to mass produce these four cells stacked on top of one another and deploy them in the field. The Economist explains that, “Solar cells are made of semiconductors, …
5X Batteries? How About 70,000X Solar Cells?
Matt Shipman of North Carolina State University News Services reports on a connector that could allow stacking solar cells without losing voltage. This stacking could allow cells to operate at solar concentrations of “70,000 suns worth of energy without losing much voltage as ‘wasted energy’ or heat.” This could have tremendous implications improving the overall efficiency of solar energy devices and reducing the cost of solar energy production. Stacked solar cells live up to their name, simply being several cells stacked on one another, with their layering leading to up to 45-percent efficiency in converting solar energy into electricity. So far, the big drawback has been the junctions between cells, which tend to waste the energy from the connected cells as heat. Dr. Salah Bedair, a professor of electrical engineering at NC State and senior author of a paper describing the work says, “We have discovered that by inserting a very thin film of gallium arsenide into the connecting junction of …
Solar Cells and Artificial Photosynthesis Make Hydrogen Directly
Science 2.0.com reports on an exciting potential breakthrough in solar energy and its direct transformation into hydrogen fuel. Usually, solar cells generate current from photons, making electricity which can run things or be stored in batteries. This new and different approach, using an innovative and inexpensive solar cell and a metal oxide photo anode, can store nearly five percent of solar energy chemically as hydrogen. The metal oxide bismuth vanadate (BiVO4) photo anode includes a small dose of tungsten atoms, was then sprayed onto conducting glass and “coated with an inexpensive cobalt phosphate catalyst,” which helped speed up oxygen formation during water splitting. Science 2.0 reports Professor Dr. Roel van de Krol’s remarks. He’s head of the Helmholtz Zentrum Berlin Institute for Solar Fuels, and worked with researchers there and at Deflt University. “Basically, we combined the best of both worlds. We start with a chemically stable, low cost metal oxide, add a really good but sim ple silicon-based thin …
Thinner than Kleenex®, as Powerful as the Sun
David L. Chandler of the Massachusetts Institute of Technology (MIT) News Office reports that an MIT research team headed by Jeffrey Grossman has found a way to make sheets that push “towards the ultimate power conversion from a material” for solar power. His team has managed to fabricate molecule-thick photovoltaic sheets which could pack hundreds of times more power per weight than conventional solar cells. Senior author of a new paper on the team’s study in Nano Letters, Grossman found that despite the interest in two-dimensional materials such as graphene – only an atom thick – few have studied their potential for solar applications. Grossman says, “They’re not only OK, but it’s amazing how well they do.” Stacking sheets of graphene and materials such as molybdenum disulfide would make solar cells with one to two percent efficiency in converting sunlight to electricity. That seems disappointingly low compared to the 15 to 20 percent efficiency of commercially available silicon solar cells. …
GraphExeter Aims for Power with Transparency
It doesn’t sound much like dispassionate, objective scholarly reporting, but the University of Exeter in England headlines its report on a University-created breakthrough material, “Revolutionary new device joins world of smart electronics.” Layering graphene and the GraphExeter, a material obviously headed for product marketing, gives a “new flexible, transparent, photosensitive device” that can lead to solar-powered clothing able to charge the wearer’s cell phone, “intelligent” windows that can “harvest light and display images,” and just maybe (in this writer’s dreams) help power electric cars and airplanes. GraphExeter, Exeter claims, is the best known room temperature transparent conductor and with graphene – the thinnest conductive material – the pair make for great potential. Researchers developed GraphExeter by sandwiching molecules of ferric chloride in between two layers of graphene. According to the University, “Saverio Russo, Professor of Physics at the University of Exeter said: ‘This new flexible and transparent photosensitive device uses graphene and graphExeter to convert light into electrical signals …
Peel-and-Stick Solar Cells Make Debut
The U. S. Department of Energy’s National Renewable Energy Laboratory (NREL) and Stanford University have teamed up to create what may be the thinnest of thin solar cells – a peel-and-stick decal. One micron thick, the decal-like peel-and-stick, or water-assisted transfer printing (WTP), technologies were developed by Stanford researchers and have been used for nanowire based electronics. Meeting at a conference where both made presentations, Stanford’s Xiaolin Zheng talked about her peel-and-stick technology, and NREL principal scientist Qi Wang spoke on his team’s research in thin-film amorphous solar cells. Zheng realized that the NREL had the type of solar cells needed for her peel-and-stick project, according to the NREL announcement. The NREL press release explains, “The university and NREL showed that thin-film solar cells less than one-micron thick can be removed from a silicon substrate used for fabrication by dipping them in water at room temperature. Then, after exposure to heat of about 90°C for a few seconds, they can …
Alchemy with Thin Film Structures
The blog has looked at several recent attempts to pull electricity from solar cells that have the ability to capture a broad range of light wavelengths. These are based on everything from layers of graphene and zinc nano-wires, to an exotic subwavelength plasmonic cavity, to straining solar cells to form wide bandgap funnels which capture light’s energy. Joining these efforts along with those of researchers in America and Germany, colleagues at the Vienna University of Technology are testing single atomic layers of oxide heterostructures, a new class of materials, to “create a new kind of extremely efficient ultra-thin solar cells.” Professor Karsten Held from the Institute for Solid State Physics at the University, explains, “Single atomic layers of different oxides are stacked, creating a material with electronic properties which are vastly different from the properties the individual oxides have on their own.” Researchers used large-scale computer simulations to discover that these layered structures “hold great potential for building solar cells.” …