Site-specific response of a 5 MW offshore wind turbine for Gujarat Coast of India

In India, the coastline of Gujarat is known to have a high potential for offshore wind energy. However, the region is highly seismically active with large magnitude earthquakes experienced in the past. The aim of the work is to investigate the site-specific response of an offshore wind turbine (OWT) for assessment of suitability of installation of OWT along the Gujarat coast. Seismic hazard analyses of 44 sites are performed using deterministic approach and response spectrum matched acceleration time histories at all these sites are obtained. Monopile for the wind turbine is designed considering a two-layered soil profile. As per specifications of National Renewable Energy Laboratory (NREL), three-dimensional finite element model of 5 MW OWT along with the soil domain is developed in the software ABAQUS considering material nonlinearity. Earthquake time histories combined with wind and wave load are being employed for the analyses. It is observed that the sites lying between Kachchh and Saurashtra regions are most vulnerable whereas sites along the western coast of Saurashtra are found to be least vulnerable. Further, seismic fragility curves for the OWT are derived for different damage states in order to evaluate the probability of damage under various seismic scenarios.