Vaneless ion wind generator

A vaneless ion wind generator or power fence is a device that generates electrical energy by using the wind to move charged particles across an electric field.

Ion wind generators are not commercially available, though working prototypes and proofs of concept have been created. Several prototypes exist in the Netherlands, one of which resides in Delft University of Technology, whose researchers developed some of the underlying technology. Ion wind generators are currently experimental, while conventional wind turbines are the most common form of wind energy generation. But ion wind generators, which have no moving parts, could be used in urban settings where wind turbines are impractical due to vibrational noise, moving shadows, and danger posed to birds. Though they are not identical in operation, Lord Kelvin's Thunderstorm demonstrates the behavior of water and concepts of electrostatics that underpin modern ion wind generators.

Design and construction

Theoretical operation

class=skin-invert-image|thumb|Wind exerts a force on a positively charged particle in the direction of the positive electrode. Its [[potential energy increases as the wind works against the electric field.]]

Ion wind generators use the force of the wind to move charged particles, typically water, against the force of an electric field. This increases the potential energy of the particles, which can be likened to moving a mass upwards against the force of gravity. The method of collecting the energy varies by implementation.

The design of ion wind generators eliminates the intermediate conversion of mechanical energy undergone in wind turbines. Wind turbines use the kinetic energy of the wind to rotate several blades about a rotor. The rotor's mechanical energy is converted into electrical energy by an electric generator.

Conversion between different forms of energy necessitates some energy loss, either to the environment or in a useless form, and fewer conversions improve theoretical output.

Simplified analytical model

Researchers from Delft University of Technology devised an equation to model the behavior of the water droplets as they move through the air in order to optimize the system mathematically and run computer simulations. For the purposes of the model, a simple electrode configuration and uniform electric field is assumed, wherein the electric force exerted on the particles will be directly opposite that of the wind.

[[File:Vaneless ion wind generator droplets repelling.png|class=skin-invert-image|thumb|Two droplets acted upon by wind and a uniform electric field, whose equal charges repel one other

Comparison with wind turbines

Ion wind generators and wind turbines share some of the same advantages and disadvantages. Both are subject to the conditions of the wind, and are unable to generate electricity if the weather conditions are not favorable. This can be mitigated to some degree with strategic placement of the devices in areas with more consistent wind speed.

Advantages

Ion wind generators are typically much smaller than wind turbines. Many wind turbine models exceed 400 feet (122 m) in height. Their size and complexity lead to high maintenance costs, which, when combined with the cost of operation, may account for a quarter of the total cost per kilowatt-hour. Wind turbines also produce noise which may disturb residents in the vicinity. The aerodynamic properties of wind turbine blades produce the noise, yet both features are not present in ion wind generators. Quieter operation has led researchers to consider using the technology in urban environments. The bladeless design of ion wind generators could make wind power more environmentally friendly, as current "wind power plants represent a risk of bird mortality." Wind turbines have maximum speeds of operation which vary by design. Wind turbines shut down when "cut-out" speeds are exceeded to prevent damage. Therefore, turbines are unable to generate energy in high speed winds which fall beyond the window of performance, while ion wind generators can theoretically continue to operate.

Disadvantages

The technology is still in its nascence, and ion wind generators are not as efficient as conventional wind turbines. During tests conducted in 2005, the EWICON was unable to match wind turbine output. Researchers were able to demonstrate "a conversion of 7% of the wind energy into electrical energy, whereas conventional wind turbine systems have an efficiency of 45% at their rated speeds. Improvements are suggested that could lead to an efficiency of the EWICON in the range of 25–30%." While the current level of development does not surpass wind turbines in efficiency, the technology could contribute to the energy mix in urban environments where a wind turbine may be impractical.

References

Patents

: Charged aerosol generator with uni-electrode source (Alvin Marks)
: Charged aerosol wind/electric power generator with solar and/or gravitational regeneration (Alvin Marks)