The Wind Farm becomes available in the Information Era and is one of the modern ways to supply Power to cities without burning fossil fuels and reducing your strategic supplies. Of course, it will have to compete for space on the map, usually with the Mine improvement. Compared to it, the Wind Farm will supply 2 less Production to the city, but it will offset it somewhat with an additional 2 Gold! At this point in the game your cities should be sufficiently developed (that is, have other sources of Production) for that to be worth it, unless you have an abundant supply of fossil fuels and don't mind polluting the environment.
People have been harnessing the power of the wind for thousands of years to sail ships and mechanically power small machines. The middle ages saw the rise in popularity of windmills to pump water, grind flour, and frighten quixotic knights. But it wasn't until December of 1980 that the very first wind farm, a group of turbines used to produce electricity, was installed in New Hampshire, United States. That farm was made up of only 20 turbines. In 2010, the first phase of construction of the Gansu Wind Farm in China was completed with 3,500 turbines.
To be most successful, these farms need to be located in an area with a consistent wind speed, and are often found along hills and in mountainous regions. As the wind blows, the blades of the turbines turn a shaft to a generator, creating electricity. Despite the specific conditions these farms need, the renewable and clean energy produced has continued to increase their popularity in recent years.