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Wind Farms
Introduction
Renewable energy is energy generated from our natural resources such as sunlight, wind, tides, and geothermal heat, which are all renewable - naturally replenished. Wind power is growing at the rate of 30% annually, with a worldwide installed capacity of 121,000 megawatts (MW) in 2008, and is widely used in European countries and the United States. Wind farms are a group of wind turbines (varying from a few turbines to several hundred) in the same location used for production of electric power. A wind farm may be located off-shore to take advantage of strong winds blowing over the surface of an ocean or lake.
Wind Farm Types
Onshore
Onshore wind farms installations require hilly or mountainous regions typically three kilometres or more inland from the nearest shoreline, exploiting the topographic acceleration as the wind accelerates over a increase altitude. The additional wind speeds gained in this way make a significant difference to the amount of energy that is produced.
Offshore and Nearshore
Offshore wind farms are generally considered to be ten kilometres or more from land. Offshore wind turbines are less obtrusive than onshore turbines, as their size and noise is lessened by distance. Because water has less surface roughness than land, the average wind velocity is usually considerably higher over open water. Capacity factors (utilisation rates) are considerably higher than for onshore and near-shore locations.
Nearshore wind farms are on land within three kilometres from the coastline or on water within ten kilometres of land. These locations are good sites for turbine installation, because of wind produced by convection due to differential heating of land and sea each day. Wind speeds in these zones share the characteristics of both onshore and offshore wind, depending on the prevailing wind direction.
Corrosion
The demanding offshore environment places stricter technical requirements to Offshore and Nearshore wind turbines and therefore greater risks of structural corrosion. In addition, there is the greater problem of access during bad weather, and greater expense when replacing larger main components. Wind turbines in offshore locations require increased corrosion protection from the sea, with reduced maintenance and service requirements.
The exterior corrosion protection of the various steel components (transition piece, foundations etc) require a cathodic protection design system (sacrificial anodes) and a paint system fulfilling the standards required for North Sea offshore installations, drilling rigs and platforms.
