As government agencies, utilities and communities across the country seek to move beyond coal, wind energy has become increasingly popular. Wind energy developments, aided by a variety of federal, state and local incentives, have helped to diversify the sources of electricity moving through the nation’s grids, and provide for small-scale, on-site generation for homes and businesses as well.
Wind energy is harvested through wind turbines, which come in various forms. Modern wind turbines are generally broken down into two categories – horizontal-axis wind turbines (HAWTs) and vertical-axis wind turbines (VAWTs) – based on the direction in which the shaft or rotor rotates. Most VAWTs are considered less efficient that the common HAWT, due to the additional drag that they have as their blades rotate into the wind.
The propeller type HAWT turbine–similar to a windmill–has been around the longest, but it is subject to certain efficiency barriers, known as Betz Limit, as well as maintenance considerations in high wind and noise. Modern HAWTs typically either have two or three blades and are designed to operate “upwind,” with their blades facing into the wind. They come in different sizes, ranging from up to 100 kilowatts for residential and single-use applications (i.e., running a satellite dish, or pumping water), and from 100 kilowatts to several megawatts for utility-scale projects.