Abstract: A pair of vertical axis wind turbines are arranged in close proximity to each other so that their vortices interact with each other to provide enhanced aerodynamic efficiency. The wind turbines are spaced as closely as possible while providing for machine and personnel safety. Adjacent wind turbines rotate in opposite directions to enhance the coupled vortex effect. The vertical axis wind turbines may be located underneath a row of horizontal axis turbines in a “bush-tree” configuration to provide greater energy extraction from a parcel of land. The vertical axis turbine includes a simple, redundant, fail-safe braking system that self-resets after a fault condition clears. The braking system includes mechanical and aerodynamic braking and also includes a speed governor that stops the wind turbine even in the event that the primary brake fails.

Abstract: A pair of vertical axis wind turbines are arranged in close proximity to each other so that their vortices interact with each other to provide enhanced aerodynamic efficiency. The wind turbines are spaced as closely as possible while providing for machine and personnel safety. Adjacent wind turbines rotate in opposite directions to enhance the coupled vortex effect. The vertical axis wind turbines may be located underneath a row of horizontal axis turbines in a “bush-tree” configuration to provide greater energy extraction from a parcel of land.

Abstract: An omnidirectional windmill employing lift type airfoils mounted about a vertical axis. The windmill includes a support frame which defines the vertically oriented axis about which the elongate airfoils rotate. Five vertically oriented stators are positioned outwardly of the airfoils about the windmill to form an omnidirectional diffuser. These stators extend radially from the vertical axis to substantially enhance the efficiency of the windmill. The stators also make the windmill self-starting. A friction heater is also disclosed in association with the windmill.