Disclosed is a vertical axis wind turbine air concentration tower with reduced radar cross section. The air concentration tower has a polygonal outer perimeter, a pivot located at each vertex of the polygonal outer perimeter, and an inwardly-positioned rudder blade operatively connected at each pivot. Each inwardly positioned rudder blade has a first wind-neutral position, and is pivotable through a plurality of angles that adjust based on an incoming wind direction, such that the incoming wind is channeled to the vertical axis wind turbine, which is located approximately at a center area of the polygonal outer perimeter. A radar absorbent material is applied to the vertical axis wind turbine air concentration tower to reduce the radar cross section. The air concentration tower is designed to provide higher wind speed to the vertical axis wind turbine than the surrounding ambient air.

Disclosed is a vertical axis wind turbine air concentration tower with reduced radar cross section. The air concentration tower has a polygonal outer perimeter, a pivot located at each vertex of the polygonal outer perimeter, and an inwardly-positioned rudder blade operatively connected at each pivot. Each inwardly positioned rudder blade has a first wind-neutral position, and is pivotable through a plurality of angles that adjust based on an incoming wind direction, such that the incoming wind is channeled to the vertical axis wind turbine, which is located approximately at a center area of the polygonal outer perimeter. A radar absorbent material is applied to the vertical axis wind turbine air concentration tower to reduce the radar cross section. The air concentration tower is designed to provide higher wind speed to the vertical axis wind turbine than the surrounding ambient air.

A wind farm comprising a number of wind turbines arranged on a ground comprising a first ground portion having a first ground surface and an outer periphery and a second ground portion having a second ground surface and surrounding the first ground portion. The first ground portion is covered with a reflective artificial covering to provide a reflecting surface having an albedo higher than the albedo of the second ground portion and thereby generating a lower temperature and a higher pressure in the first ground portion than in the second ground portion and a wind having a speed in a direction from the first ground portion towards the second ground portion. Some of the wind turbines are arranged in the second ground portion in such a distance from the periphery of the first ground portion that they are subjected to the wind coming from the first ground portion.