These collections of wind turbines are called wind farms. The most famous wind farm, in Altamont Pass, California, has 7,500 turbines. Most wind turbines look like airplane propellers mounted on towers. The propellers rotate on an axis that is horizontal to the ground. These turbines are called horizontal-axis turbines.
Some wind turbines have a vertical axis.
One kind, the Darius, looks like an upside-down eggbeater. Another kind, the Savonius windmill, is made of two upright semi-cylinders. They are both called vertical-axis turbines. Once a wind device is installed, the only cost is the cost of maintaining the equipment. The energy to run it is free.