Wind Energy in Sustainable Power Generation and Supply

Abstract

Modern wind turbines capture the kinetic energy of moving air and convert it into shaft power to drive an electrical generator/alternator. The turbine is typically comprised of three basic parts: the rotor, the nacelle, and the tower. The rotor includes the turbine's blades (most often 3 in horizontal wind axis turbines) and the nose cone/hub. The nacelle contains the driveshaft, transmission a, the unit's generator/alternator, the electronic controls to convert the generators or alternator's electrical output to quality suitable for use, and the tail vane or yaw drive that keeps the turbine oriented to the wind, either upwind or downwind depending on the turbine's design. Because wind speed generally increases and turbulence decreases with height, a tower helps the system increase its energy production and reduces turbulenceinduced mechanical stresses, thus enhancing its economic benefit. The ability of a turbine to produce energy from the wind fundamentally depends on the wind resource and the swept area of the turbine. Simplifying somewhat, the power output of a turbine is proportional to the cube of the wind velocity and the square of the blade length. A doubling of the wind speed thus yields an eight-fold increase in wind power while a doubling of a turbine's blade length yields a four-fold increase in energy capture (all other things kept constant). Larger turbines with longer blades not only produce more energy for a given wind resource, but they are also more capital cost-effective as well, because of inherent economies of scale as well as inefficiencies in the market for smaller turbines. The installed cost/kW for a small turbine is twice that for a mid-scale turbine and can be several times as expensive as that for a utility-scale turbine. While these factors argue for choosing the windiest sites and installing the largest turbines on the highest towers that are cost-effective for the site -an argument understood by wind farm developers -residential and commercial site hosts cannot follow this logic to its conclusion. It is a rare home or business owner that is going to move their establishment simply to take advantage of a windier site. And several practical constraints prevent home and business owners from using the giant turbines typically found in utility-scale wind farms. Neighbors might object to the presence of a turbine hundreds of feet tall because of safety, noise, and visual concerns. The turbine's capital costs are an additional consideration: even if a site host has the space for a giant turbine, the multi-million-dollar capital cost can be difficult to finance for someone not in the wind industry. As a result of these constraints, most distributed wind turbine installations are sized roughly equivalent to the site host's electrical load and use turbines much smaller than those found in current-day wind farms. This analysis therefore assumes that residential customers will install turbines with nominal capacity ratings of 1-9 kW, while commercial customers will install turbines with nominal...