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#71
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Electrically Powered Ultralight Aircraft
On Tue, 7 Aug 2007 18:09:36 -0400, "Morgans"
wrote in : I think I recall seeing someone do the calculations of how much solar energy hits the top surface of a sailplane and wing, and it was still not enough to motor without thermals, if it was all converted to electrical energy. Here's one that flew across the US seventeen years ago: http://www.solar-flight.com/sslink.html |
#72
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Electrically Powered Ultralight Aircraft
On Tue, 07 Aug 2007 23:14:59 GMT, wrote in
: Current conversion technology is about 22% at best. Technologies in the works are promising 50-60% http://www.boeing.com/news/releases/...60828a_nr.html ST. LOUIS, Aug. 28, 2006 -- The Boeing Company [NYSE: BA] has signed a contract to provide 600,000 solar concentrator cells to SolFocus, Inc., a California-based renewable energy company that is developing renewable terrestrial energy alternatives. "Companies on the cutting edge of the renewable energy revolution come to us because we are the world's leading manufacturer of solar cells," said Charles Toups, vice president of engineering for Boeing Space and Intelligence Systems. "Our Spectrolab subsidiary has leveraged its expertise in space photovoltaic products to create solar cells with record-breaking efficiencies for Earth-based applications." Under the 12-month contract from SolFocus, Inc. of Palo Alto, Calif., Spectrolab will build and deliver 600,000 solar concentrator cells that will be used to convert the sun's rays into affordable electricity for homes and businesses. The cells produced for SolFocus will be capable of generating more than 10 megawatts of electricity, or enough to power about 4,000 U.S. homes. With the average solar cell efficiency above 35 percent at concentration, Spectrolab's concentrator photovoltaic cells generate electricity at a rate that can be more economical than electricity generated from conventional, flat panel photovoltaic systems. "Our mission is to deliver reliable solar-generated electricity at wholesale energy prices, and Spectrolab's multi-junction concentrator solar cells are key to making that possible," said Gary D. Conley, CEO of SolFocus. "Spectrolab's cells will be integrated into our upcoming solar concentrator field test program and then into the first phase of active deployments." A significant advantage of concentrator systems is that fewer solar cells are required to achieve a specific power output, thus replacing large areas of semiconductor materials with relatively inexpensive optics that provide optical concentration. The slightly higher cost of multi-junction cells is offset by the use of fewer cells. Due to the higher efficiency of multi-junction cells used in the concentrator modules, only a small fraction of the cell area is required to generate the same power output compared to crystalline silicon or thin-film, flat-plate modules. ================================================== =================== http://www.boeing.com/news/releases/...60815b_nr.html ST. LOUIS, Aug. 15, 2006 -- The Boeing Company [NYSE: BA] today announced it has signed a multi-million dollar contract to supply concentrator photovoltaic (CPV) cell assemblies to an Australian company that produces renewable solar energy. Under the contract with Solar Systems Pty. Ltd. of Hawthorn, Victoria, Boeing will deliver 500,000 concentrator solar cell assemblies for use at power stations that generate renewable energy for small, remote Australian communities. Spectrolab, Inc. of Sylmar, Calif., a wholly-owned Boeing subsidiary, will manufacture the cells. Deliveries will begin later this year. The solar cell assemblies will be capable of generating more than 11 megawatts of electricity -- enough to power 3,500 average-sized homes. "For the past 50 years, Spectrolab has been a leader in space-based solar cells," said Dr. David Lillington, president of Spectrolab, the world's leading producer of space and terrestrial concentrating solar cells. "We have leveraged our expertise in space photovoltaic products and created terrestrial concentrating solar cells with record-breaking efficiencies averaging above 35 percent. We are now partnering with the best of industry and making great strides in reducing the cost of solar energy to homes and businesses worldwide." This contract with Solar Systems continues an earlier relationship between the two companies. In April, Spectrolab and Solar Systems brought the world's first full-scale ultra high efficiency 35-kilowatt solar generator online in Australia. The system created a new benchmark for solar concentrator systems both in system efficiency and cost, and showed great promise for the future of renewable energy. "The breakthrough demonstrated by this fully operating, full-scale system shows the potential for CPV to dramatically change the economics of solar power. We expect this to be the first commercial phase of a very large and valuable relationship," said Solar Systems Managing Director Dave Holland. "Our partnership with Spectrolab represents a new level of cooperation toward the common goal of meeting the community's power needs with clean, green electricity." Solar Systems' concentrators resemble a satellite dish with curved reflecting mirrors shaped to concentrate sunlight onto the solar cells. A sun-tracking mechanism allows electricity to be produced from morning to late afternoon. Small, remote communities are using a number of concentrator dishes in "solar farms" for energy during the day and switching to diesel generators at night. A significant advantage of concentrator systems is that fewer solar cells are required to achieve a specific power output. Large areas of semiconductor materials now can be replaced with lower cost concentration devices. The higher cost of ultra high efficiency multi-junction cells is offset by the need for fewer cells. Because multi-junction cells are so efficient, only a fraction of the cell area is required to generate the same power as crystalline silicon or thin-film flat-plate designs. ================================================== ============= |
#73
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Electrically Powered Ultralight Aircraft
Orval Fairbairn wrote:
In article , Orval Fairbairn wrote: In article . com, James Sleeman wrote: On Aug 6, 4:52 am, Larry Dighera wrote: Electrically Powered Ultralight Aircraft It's a nice idea, but realisitically there are too many problems, not the least of which is battery size, weight, cost and safety. I don't really see batteries as a viable in the near future (I struggle to see them as viable in the distant future either). Look at the problem this way: In an all-electric machine, you carry ALL of your energy supply with you: fuel and oxidizer -- to make electricity. With any IC engine, you carry the fuel only -- the air is free (20% oxygen), so, at 15:1 air/fuel ratio, you would need 90 lb of air for each gallon of fuel. Therefore, for a nominal 50 gallon fuel capacity (300 lb), you would have to carry an additional 7500 lb of air. That is a lot of weight for a 3000 lb aircraft! DUH! I meant 4500 lb of air! That is still a lot of weight penalty. Well, to be fair Orval, you do get the 90% efficiency in an electric motor, vs the 30% in an IC engine. You'd only have to drop 1500lb of useful load with the electric motor. Isn't the useful load of most light airplanes somewhere between 600 and 2000lbs? |
#74
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Electrically Powered Ultralight Aircraft
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#75
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Electrically Powered Ultralight Aircraft
Gattman wrote:
I agree. It's on the way. Wasn't too long ago that terms like "lithium ion" and "nickle metal hydride" were unheard of to the common consumer. It takes a lot of energy to manufacture those batteries ... and recycle them when they are used up. You have to factor that into the equation. These batteries have high energy per unit volume but they cost a lot of money because it takes a lot of energy to produce them. |
#76
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Electrically Powered Ultralight Aircraft
Larry Dighera wrote:
There is a 14 HP Powered Paraglider (PPG) engine offered he http://www.poweredparasports.com/Par...#Jet%20Details They also state that the weight of their engines ranges from 46 lbs. to 68 lbs. If a 14 HP electric propulsion system weighing 46 lbs could be constructed, apparently it would permit the use of PPGs by pilots up to 180 lbs. Yeah sure, but its not practical for anything but an hour or two of playing around on a Saturday afternoon. You can't carry anything or go anywhere to accomplish anything except maybe brag about how little energy you used goofing off for a few hours. Its like blasting around on a jet ski... basically a total waste of energy without producing any useful work or benefit to mankind. Don't get me wrong, I love new technology and if you can afford to spend money on extra curricular stuff like aimlessley cruising about in solar powered paragliders or jet skis fine. But don't think you are doing the world a big favor because you used something other than gasoline to power it. |
#77
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Electrically Powered Ultralight Aircraft
jimp wrote In rough numbers, you get about 1 kW/m^2 of energy from the sun on a clear day. Current conversion technology is about 22% at best. Technologies in the works are promising 50-60% (the check is in the mail and I will respect you in the morning). One presumes a sailplane is going to spend most of its time sailing and only using the motor (with batteries) to get off the ground and occassionaly cruise between thermals. So most of the time you are just charging the batteries. That is why I specified cruising with the motor without thermals; to get a feel on how the extra surface area and high aspect ratio (efficiency) would mimic a cross country, motor cruise. -- Jim in NC |
#78
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Electrically Powered Ultralight Aircraft
On Tue, 7 Aug 2007 21:08:12 -0400, "Morgans"
wrote in : That is why I specified cruising with the motor without thermals; to get a feel on how the extra surface area and high aspect ratio (efficiency) would mimic a cross country, motor cruise. It's beginning to look like the 21st century indeed: http://www.solar-impulse.com/en/index.php Bertrand Piccard and the EPFL unveil project to fly around the world in a solar powered airplane Lausanne, Switzerland -- A team of aviators and scientists led by Dr. Bertrand Piccard, the first man together with Brian Jones to circle the earth non-stop in a balloon in 1999, announced plans in Lausanne, Switzerland Friday to develop an aircraft powered by the sun and capable of circling the earth. The Piccard team envisions being able to spend full nights in the air by 2007. Piccard will be assisted by Jones, his co-pilot in their Breitling Orbiter 3 balloon, and André Borschberg, engineer and jet plane pilot. Their new project, dubbed Solar Impulse , is aimed at demonstrating the role of high technology in sustainable development. The EPFL (Swiss Federal Institute of Technology in Lausanne/ Ecole Polytechnique Fédérale de Lausanne ) is the official scientific advisor to the project. The EPFL conducted thermodynamic research in support of the Piccard/Jones 1999 balloon flight, and is the official scientific advisor to Alinghi , current holder of yacht racing's prestigious America's Cup. EPFL, November 28th 2003 ------------------------------------------------------------------ http://radio.weblogs.com/0105910/2004/04/01.html Solar Impulse Will Circle the Globe in 2009 Bertrand Piccard, the Swiss adventurer who was one of the two first men to fly around the world non-stop in a balloon in 1999, wants to achieve the same goal again. But next time, he will use a pollution-free, single-pilot solar-powered aircraft. The plane, named Solar Impulse, will look like a glider, but its 70-meter wingspan will exceed the one of a Boeing 747. Universe Today says a prototype will be ready next year and that the plane should be ready for its flight around the world in 2009. The proposed aircraft resembles a glider, but with a mammoth 70-metre wingspan, exceeding that of a Boeing 747. Completely covered by solar cells and equipped with possibly two tail-mounted propeller engines, the plane will be capable of unassisted take-off and will carry the necessary batteries for night flying. ... ---------------------------------------------------------------- http://www.universetoday.com/am/publ...und_earth.html Solar Plane Will Attempt to Go Around the Earth Summary - (Mar 31, 2004) The European Space Agency will be supplying technology to assist adventurer Bertrand Piccard's attempt to fly a solar-powered plane around the world. Piccard was part of the team that successfully flew a balloon around the Earth. The solar powered plane will have a 70-metre wingspan (larger than a Boeing 747), and carry enough batteries to be able to fly in the night as well. The plane would fly at an altitude of 10 km; well above the clouds to capture all the available sunlight. The first round-the-world attempt will be made some time after 2009. Full Story - Image credit: ESA ESA's Technology Transfer Programme is to supply state-of-the-art technologies to assist adventurer Bertrand Piccard's flight around the world in a single-pilot solar-powered aircraft, ... The EPFL study says that current off-the-shelf lithium-ion batteries provide just under 200 watt-hours per kilogram (Wh/kg), enough to support a single-pilot plane, while a two-pilot solution would require a capacity of at least 300 Wh/kg. The plan is to design and construct the first prototype aircraft in 2004-2005, with initial test flights in 2006. The next step is to complete night flights in 2007, initially at least 36 hours including one full night. From then on flying lengths are to be increased. . Innovative solutions will be required to store the necessary food and water while reduce weight to a minimum – familiar problems for ESA engineers designing space missions. When will the Solar Impulse fly around the world, non-stop? "It is planned to cross the Atlantic in 2008 and fly around the world with stop-overs in 2009," says André Borschberg, "To fly around non-stop depends very much on how quickly we will have higher energy density batteries…but not before 2009." ... |
#79
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Electrically Powered Ultralight Aircraft
On Wed, 08 Aug 2007 01:05:16 GMT, kontiki
wrote in : Yeah sure, but its not practical for anything but an hour or two of playing around on a Saturday afternoon. I'll bet you would have said something similar to the Wrights. :-) Where's you vision, man? Now here's an electrically powered aircraft that really is playing around: http://www.nesail.com/videos/jazz.wmv |
#80
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Electrically Powered Ultralight Aircraft
On Aug 8, 2:21 am, Larry Dighera wrote:
I see what you mean. Unfortunately, the highest power requirements of aircraft engines are during the takeoff and climb phases of flight. Hence why i was thinking more along the lines of a electric motor + reasonable battery coupled to a stirling. The battery provides the oompfh for takeoff (and other moments of urgency) from stored energy. The stirling charges the battery, or passes current through to the motor when the battery is at peak charge (hand waving the bajillion technical details which I don't know), it doesn't matter that the stirling doesn't run at peak efficiency at all times, in cruise mode you'd want it to be at peak and providing more than enough current to the motor with some spare to charge the battery. The article I linked to was more along the lines of a direct-drive, but I think hooking the output shaft from a stirling straight to a gearbox/prop would not be a good idea, you are stuck with too many disadvantages and it makes the engine design more complicated than necessary. The main advantage of the stirling+battery versus just battery, is that you remove the requirement for major infrastructure change (abundant charging points at airports), the stirling just needs some fuel (which could be anything from mogas to radiant solar heat) and that's it, no infrastructure change is necessary in the interim, and minimal in the long term. As an added benefit, you get much better cruise endurance than battery alone. |
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