Environmental Engineering Reference
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As the contrast, most of small wind turbines are off-grid for residential homes,
farms, telecommunications, and other applications. However, as an intermittent
power source, wind power produced from off-grid wind turbines may change dra-
matically over a short period of time with little warning. Consequently, off-grid
wind turbines are usually used in connection with batteries, diesel generators, and
photovoltaic systems for improving the stability of wind power supply.
5.1.6 Onshore and offshore wind turbines
Onshore wind turbines have a long history on its development. There are a number
of advantages of onshore turbines, including lower cost of foundations, easier inte-
gration with the electrical-grid network, lower cost in tower building and turbine
installation, and more convenient access for operation and maintenance.
Offshore wind turbines have developed faster than onshore since the 1990s due
to the excellent offshore wind resource, in terms of wind power intensity and
continuity. A wind turbine installed offshore can make higher power output and
operate more hours each year compared with the same turbine installed onshore.
In addition, environmental restrictions are more lax at offshore sites than at
onshore sites. For instance, turbine noise is no long an issue for offshore wind
turbines.
5.2 Wind turbine confi guration
Most of the modern large wind turbines are horizontal-axis turbines with typically
three blades. As shown in Fig. 7, a wind turbine is comprised of a nacelle, which
Wind vane
Control panel
Nacelle
Gearbox
Coupling
Main shaft
Hub
Mainframe
Generator
Pitch control
Yaw deck
Main bearing
Yaw control
Tower
Figure 7: A horizontal-axis wind turbine confi guration. Courtesy of the US Patent
& Trademark Offi ce.
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