Modern wind turbines fall into two basic groups;
The horizontal-axis variety, like the traditional farm windmills used for pumping water, and
The vertical-axis design. Most large modern wind turbines are horizontal-axis turbines.
Now, there are near silent wind turbines that are designed specifically for city rooftop use! They rotate on vertical axis, optimizing wind capture, even as the air stream shifts within the dynamic city landscape. They take up just 40 square feet to generate ONE kilowatt, to get that much juice from a solar array, you would need up to 400 square feet, which is a tough sell in major cities
Even though the cost of wind power has decreased dramatically in the past 10 years, the technology requires a higher initial investment than fossil-fueled generators.However, wind energy costs much less when compared with energy generated from fossil-fuel, because there is no fuel to purchase and minimal operating expenses.