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. They make up 95 percent of all wind machines. A typical horizontal wind machine stands as tall as a 10-story building and has two or three blades that span 60 feet across.
Wind machines stand tall and wide to capture more wind.
Vertical-axis wind machines make up just five percent of the wind machines used today. The typical vertical wind machine stands 100 feet tall and 50 feet wide. The most popular vertical wind machine today is the Darrieus wind turbine, named after its inventor, J.G.S. Darrieus, a French engineer. Each wind machine has its advantages and disadvantages. Horizontal-axis machines need a way to keep the rotor facing the wind.