Segment V12.1: Windmills

(Related to Textbook Section 12.2 - Basic Energy Considerations)

Windmills are unducted, axial-flow turbomachines that extract energy from the moving air.

The windmill blades are shaped so that the absolute velocity of the air upstream of the windmill is different than that downstream. For this to occur, the blades must push on the air (or equal and opposite, the air must push on the blades), thereby producing a torque. Although the child's pin-wheel, the farm windmill, and the modern wind turbine are quite different in details, size, and purpose, their basic operating principles are the same.