inputs occur during the manufacturing and installation stages; (2) there are no associated fuel costs (except for biomass-fueled electricity generation); (3) opportunities for achieving economies of scale are greater at the manufacturing stage than at the generating site—larger-generation units do not necessarily reduce the average cost of electricity generation as much as they do for coal-fired or nuclear plants; and (4) renewable electricity technologies can be deployed in smaller increments and come on line more rapidly.

Technology Descriptions
Wind

Wind power uses a turbine and related components to convert the kinetic energy of moving air into electricity. A typical wind turbine assembly includes the rotor, controls, drive train (gearbox, generator, and power converter), other electronics (wiring, inverters, and controllers), and a tower. Each of these components has undergone significant development in the last 10 years, and the resulting modifications have been integrated into the latest turbine designs. Critical objectives for these and future improvements are to make it easier to integrate the wind power plants into the electrical system and to increase their capacity factors. Especially important has been the development of electronic controls that allow modern turbines to remain connected to the electricity grid during voltage disturbances and reduce the draw on the grid’s reactive power resources. Advances in computerized controls will allow more aspects of the turbine to be monitored, resulting in more efficient use and the potential to better target and deploy technical upgrades.

Along with advances in electronics have come improvements in wind turbine structures, allowing turbine size and generating capacity to grow. Based on the fact that wind speed increases with height and that energy-capture ability depends on the turbine’s rotor diameter, the most common turbines at present are three-bladed rotors with diameters of 70–80 m, mounted atop 60–80 m towers, that have a capacity of 1.5 MW. The rotor blade has gone through many generations of designs, using various types of materials and structures, to maximize its aerodynamic performance without compromising stability.

Wind power technologies are actively being deployed today, and no major technological breakthroughs are expected in the near future. However, evolutionary modifications in various turbine components are expected to bring 30–40 percent improvement in cost-effectiveness (cost per kilowatt-hour) over the next



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