Then in the early 1970s, oil shortages created an environment eager for alternative energy sources, paving the way for the re-entry of the electric windmill on the American landscape. Today's wind machine is very different from yesterday's windmill. Along with the change in name have come changes in the use and technology of the windmill. While yesterday's machines were used primarily to convert the wind's kinetic energy into mechanical power to grind grain or pump water, today's wind machines are used primarily to generate electricity. Like old-fashioned windmills, today's wind machines still use blades to collect the wind's kinetic energy.
Windmills work because they slow down the speed of the wind.
The wind flows over the airfoil shaped blades causing lift, like the effect on airplane wings, causing them to turn. The blades are connected to a drive shaft that turns an electric generator to produce electricity. Modern wind machines are still wrestling with the problem of what to do when the wind isn't blowing. Large turbines are connected to the utility power network-some other type of generator picks up the load when there is no wind. Horizontal-axis wind machines are used the most.