Humanity has been using the wind to do work for thousands of years. The kinetic energy of the wind can be changed into other forms of energy, either mechanical energy or electrical energy. When wind fills a sail, its kinetic energy is being used to push a sailboat through the water. Farmers have been using wind energy for many years to pump water from wells using windmills like the one shown on the right. Wind is also used to turn large grinding stones to mill or grind wheat or corn, just like a water wheel is turned by water power.
The wind is also used by a wind turbine to make electricity.
According to the online Illustrated History of Wind Power Development, the first use of a large windmill to generate electricity was a system built in Cleveland, Ohio, in 1888 by Charles F. Brush. The Brush machine had multiple-blades more than 50 feet in diameter. Over the last 100 years, wind turbines have advanced dramatically through newer technology and better understanding of the dynamics of the wind. But in order to generate electricity, you still need relatively constant wind speeds in any given location.
We have many windy areas in California. The only problem with wind is that it is not windy all year long, nor is the speed fairly constant. It is usually windier during the summer months when wind rushes inland from cooler areas, such as near the ocean, to replace hot rising air in California's warm central valleys and deserts. By placing mechanical wind turbines in these windy areas, we tap the moving wind to make electricity.
A wind turbine is very similar to a child's pinwheel or the propeller of an airplane. The blade of a turbine is tilted an angle. The movement of the air is channeled creating low and high pressures on the blade that force it to move. The blade is connected to a shaft, which in turn is connected to an electrical generator. The mechanical energy of the turning blades is changed into electricity.
Wind speeds typically must be sustained and at least 10 miles per hour to turn larger turbines fast enough to generate electricity. The turbines usually produce about 50 to 300 kilowatts of electricity each. A kilowatt is 1,000 watts (kilo means 1,000). You can light ten 100 watt light bulbs with 1,000 watts. So, a 300 kilowatt (300,000 watts) wind turbine could light up 3,000 light bulbs that use 100 watts.
There are more than 14,000 wind turbines in California grouped together in what are called wind "farms." The farms have roughly 1,800 megawatts of installed capacity. These wind farms are located mostly in the three windiest areas of the state:
- Altamont Pass east of San Francisco
- San Gorgonio Pass near Palm Springs
- Tehachapi south of Bakersfield
Together these three places make enough electricity to supply an entire city the size of San Francisco with electrical power! All together the wind turbines in California produce about 1 percent of California's total electricity.
Photo by Warren Gretz, NREL 11144
If you're driving along the freeways near California's wind farms, many of them may appear to not be working. There are any number of factors: wind speed is not high enough, the turbine may be too old to produce electricity, the turbine may be down for maintenance, or the wind speed may be too high. Many of the older turbines are being upgraded and replaced by newer, more efficient models.