Abstract
Offshore wind has potential to generate electric power at lower prices than other renewable energy. However it is said offshore wind generation is more costly than onshore. Therefore we verified power curves for time varying wind velocities offshore and on land, taking into consideration the difference of mean wind speed ratio, vertical distributions of wind velocity, and wind spectra of the offshore and land respectively. As a result we found that while the power curve for the land is worse than that for the offshore, they are inferior to the theoretical power curve as a steady velocity. Then we estimated power generation yields and costs for land and offshore wind farms by using the actual data i.e. the annual occurrence of mean wind velocities measured at the Port of Akita and Akita Regional Meteorological Observatory. Thus the annual energy yields depends on the ratio of mean velocity offshore to on land and the offshore is more competitive from 1.1 to 1.9 than the land. Furthermore, condition of being feasible is that the mean velocity offshore is twenty percent larger than on land. The paper also describes dynamic structural analytical results against wind and wave loadings as vibration characteristics of wind turbine system consists of blade; turbine, tower and sub sea base structure which become important to design the offshore wind farm.
