Design of wind turbines in an area with tropical cyclones

The lifetime and cost of wind turbines is influenced by a combination of fatigue and extreme loads and the applied design codes. In general wind turbines are designed for 20 years of operation using design standards which are based largely on European conditions. In areas with tropical cyclones application of these structural design codes and the fact that information on external conditions is limited may result in either too high cost or too high risk. The present paper analyses the design basis of wind turbines, when applied in areas of the world where tropical cyclones occur in certain parts of the year. Tropical cyclones are distinct different phenomena from ordinary storms and traditional extreme wind statistics will not take into account the tropical cyclones. A method is developed to characterise tropical cyclones and to derive the structural design wind speed (U5o) at a given site, based on existing and publicly available cyclone data. An extreme wind atlas with a resolution of 1 ° x 1 ° is developed for the Northern West Pacific i.e. the sea around the Philippines, Taiwan and Japan. Verification is in progress of the actual values in the atlas using data from ground stations. Based on a simple model of the cost of a wind turbine the increase in cost is estimated at 20- 30% in an area with an estimated U50 of 60 m/s compared to a site with U50 of 50 m/s