Ballooning oil prices both in the United States and globally have brought alternative energy sources including wind energy to the forefront. Offshore wind energy is fast becoming an attractive proposition because there are vast wind resources located offshore with little visual or noise impact to local communities. But developing these wind resources 15 to 30 km from shore would require large foundations which could be cost prohibitive. To make such a proposition cost effective requires even larger wind turbines. These large wind turbines will place large demands on the support structures and foundations. As an increasing number of wind farms are being planned offshore in water depths of over 50 m, the combination of water depth and the increased windmill tower heights and rotor blade diameters will create loads that make foundation design very complex. Moreover, offshore foundations are exposed to additional loads such as ocean currents, storm wave loading, ice loads and potential ship impact loads. All of these factors pose significant challenges in the design and construction of wind turbine foundations. This paper presents various issues facing the designer in designing offshore wind turbine tower foundations. Current practices are examined and summarized to assist developers in foundation type selection and design.
In the United States, offshore wind power development has not been a focus area because there is great potential for wind power on land. However, high quality onshore wind resources are mostly located in the Midwest and Central United States while the demand centers are located along the coasts, thereby making the cost of transmission high. On the northeast coast of the United States, offshore development is an attractive alternative because electricity costs are high and transmission line construction from the mid-west faces many obstacles. Higher quality wind resources, proximity to coastal population centers, potential for reducing land use, aesthetic concerns, and ease of transportation and installation are a few of the compelling reasons why power companies are turning their attention to offshore development.
