Turns out a professor friend of mine is BIG into solar. We spent a good 40 minutes talking about it in his office today and flight and stuff.. If you have any questions on Thin Film solar, i will tryo to ask him when i see him again next week. Also, he will be giving me names of a few people who own companies that he knows, so yeah, we might get a discount or two versus buying outright. It's about 100+ for the goods per unit, so this isn't exactly a cheap endeavour, but for an exhaustive flight, it would be a nice thing to have.Thus far....we should get 8watts of power per square meter of thin film in a realistic setting. This is for electric planes, obviously. He also suggested compressed air engines? I don't know. my carbon fiber bottles for paintball are light, but i don't think they are THAT light...then again...battery weight...Oh, WIND POWER WILL NOT WORK, DON'T ASK, DON'T TRY.And please, no flaming or arguing...i'm only trying to help. You can politely disagree, and state your sources on why, but i would rather help than argue moot points. :)

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  • T3
    8 watts/m^2? At noon that would mean less than 0,9% efficiency - atleast according to the graph at: http://www.sky-sailor.ethz.ch/ . In their SkySailor project they got 84-90 watts from about 0,5 m^2 of panels. My EZG uses about 40 watts on average during a flight with camera so I could easily acheive sustained flight (during day time) if I could afford the panels since EZG has 0,41m^2 of wing surface area...... although they probably used some super efficient solar modules..

    BTW: I can't remember which university it was but anyways: some university (in Finalnd?) is developing printable electronics and solar cells.. Think about that: solar cells printed directly onto your RC!
    Sky-Sailor: Solar Autonomous Airplane for Mars exploration
  • As an investigative exercise a few years ago I looked into building a solar powered plane that could autonomously fly around the world.

    Unfortunately I found the construction of such an aircraft is not possible with current COTS technologies at the time. There are two factors that are preventing the creation of such an aircraft. The first is energy storage technology. Data on Li-S battery technology would indicate that it may be able to provide enough storage for multiple over night flights but current battery technologies lack the power to weight ratio required for such a mission. Super capacitors also provide interesting performance charachteristics. The second factor are solar cell efficiencies.

    As far as solar technologies go, thin film has an atrocious efficiency rate. The best cell available (that I found) is produced by sun power. http://www.sunpowercorp.com/Products-and-Services/Commercial-Solar-.... Boeing, and most recently NASA have demonstrated cells with a 40% conversion rate. Sun power advertises a 21% conversion rate for their cells. Somewhere I have some estimates on output of these panels when configured for a small aircraft wing.

    Certainly thin film is interesting from a weight and ease of fabircation perspective, but 8 W/m^2 is nothing to an electric motor.

    Compressed air is interesting, anyone have the energy density of compressed air at various pressures?
  • Wind power (fan on nose thing) will work, but adds drag which is proportional to power extracted plus inefficiencies. Good for fast sailplanes. I think you know that you cannot have perpetual motion. NASA did however patent in the 60's a system to extract power from wingtip vorticies using windmills on the wingtips; I believe they outfitted a Piper Warrior with them.

    I have been working on making a commercial solar cell unit for powering the R/C receiver and servos only. What I am trying to do is use a PIC to control cell voltage, thus the cell(s) will be at optimal power extraction, and use a MAX1771 chip or similar to output 5V@200mA from a source down to 1.2V so that the cell will provide power even when it is not in the best orientation and a standard small NiMH or LiPo cell can be used to provide backup power.

    In order to fly completely on solar power, the goal is to be aware of the aircraft's total power consumption; meaning the aircraft must be designed to be super energy efficient in the areas of aerodynamics, power management, and overall weight. This is the reason I am trying to control cell voltage, aka. minimal cell area required. The aircraft will in no way be a 'screamer', however a HALO design would work perfectly, ie. Helios.

    Compressed air or gas has been used in free flight modeling for years. The thing to watch is the cooling of gasses as they are expanded. For compressed air cars, see MDi from France, the tank pressures range from 3000psi on up.

    What university are you at? Major?

    I am a 4th year aerospace engineering major at CalPoly (calpoly.edu). I also do a lot of Electric Vehicle development and work at BatteriesPlus (batteriesplus.com) so I know my batteries. Most of the stuff I have done is High G capable sensing and data circuit integration for high power amateur rocketry.
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  • It's not true that Wind Power won't work, it's just that it is extremely complicated.

    A Sailboat, for example is a lighter-than-x object propelled by the velocity differential between two fluid bodies.

    By extension, any object can be motivated by the velocity differential of the same fluid body, provided one can achieve a purchase on parts of the fluid with contrasting velocities. A Kite is a partial example of a airplane powered by the wind - a full example would require two kite in contrasting winds. Such a pair of kites would need aerodynamic control - but there is no fundamental reason why such a pair of kites could not exist, nor why, if they were to exist, they could not derive motivation from the relative movements between their respective adjacent fluidspace.

    All the other questions are pedantic - ask the prof about the flight potential of relative air movement; at least its a suitably complicated question...
  • What would the weight be for the square meter of thin film? Using carbon and carbon/kevlar it is possible to build an extremely light frame to use for this kind of apps. What kind of shape do the panels come in?
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