What is a FLAG?

A FLAG is an Flexible Linear Aeroelectrostatic Generator, a new type of wind generator.  It is a flexible electronic circuit combined with an aerodynamic oscillator, generating electricity from moving air.

What are the potential applications for FLAGs?

In contrast to the extremely large rotary wind generators which are typically located at only the windiest sites, FLAGs are well suited to distributed small-scale power generation.  FLAGs can have the appearance of flags, trees, or kites.  For larger scale installations, FLAGs can be constructed with large multi-cell arrays, and multiple layers.  The FLAG is also well suited to specialty applications where ultra low-mass power generation is advantageous.

What are the potential advantages of FLAGs?

  • Printing based manufacturing
  • Low Mass
  • Low Cost
  • Broad Windspeed Range
  • Appearance of Tree Leaves, Flags, or Miniaturized
  • Airborne applications
  • Acceptable Noise Profile
  • High Efficiency
  • High Energy Density
  • Recyclability

What plastic films are best for a FLAG?

One of biggest benefits of the FLAG with respect to power generation, is it works well with ordinary low-cost plastics.  The best plastic films typically have the following basic characteristics: flexible, high dielectric constant, high dielectric strength, high surface resistivity, high volume resistivity, and low adsorption of humidity. Plastic films that have been surface treated for printing typically do not work well.

Examples of good plastics include:

  • Polyester (ie: Mylar)
  • ETFE (ie: Tefzel)

Polyethylene, polypropylene, acetyl, polyimide, and many other plastics will work. The thickness of the films are typically .002”- .005”.  Poor quality materials in an open-to-air design may have difficulty starting in high humidity conditions.

What conductive materials are FLAGs best made out of?

If a FLAG were to be made commercially, it would most likely be made using conductive inks, coatings, or metallization, and the conductive circuits should be completely encased within the insulating film material to eliminate surface conduction losses and dramatically improve the performance. For DIY FLAGs, the best material to use is conductive fabric tape with conductive adhesive (such as 3M CN-3190). FLAGs can also be constructed using inexpensive materials such as hardware store aluminum foil tape, and aluminum or copper tape with conductive adhesive.

Why use an electronics based harvesting system if a FLAG can be designed that will work without them?

The use of diodes makes FLAG designs possible that do not have exposed conductors and are relatively impervious to humidity. This allows significantly higher operating voltages and power output. FLAGs using mechanical contacts instead of diodes are more susceptible to humidity and are better suited to low humidity indoor demonstrations.

What kind of diodes are used in the harvesting circuits?

Microwave oven diodes, or electrostatic air cleaner diodes are best. For experimentation, a high performance option is the M100FF3 available from the following supplier: http://www.voltagemultipliers.com/products/diodes/.

Alternatively, 1N4007 diodes are inexpensive and also work, although with these diodes the FLAG does not always start immediately or as easily.  These are a fairly standard electronics component that can purchased from a number of online electronics suppliers such as Mouser and Digikey.

Can a DIY FLAG be insulated with adhesive tape to improve the performance?

Although this seems like a good idea in theory, virtually all tapes are not appropriate for this purpose.  The use of adhesive backed tapes as insulation on a FLAG will almost always prevent it from working for longer than a few seconds or minutes.  Charges conduct through the tape adhesive, and build up there creating a capacitance with the FLAG conductors that cannot easily be released (reversing polarity can temporarily correct this issue).

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