In this study, wind and waves are studied for offshore wind power at the Donghae gas field in South Korea. Two kinds of data sets are compared: one set contains 39-year National Oceanic and Atmospheric Administration (NOAA) hindcast data and the other 3-year buoy-measured data obtained by the Korea Meteorological Administration in South Korea (KMA). The NOAA and KMA data sets for different reference periods, recording intervals, and measuring altitudes are compared. Furthermore, data from 2.7-year (2 years and 8 months) in situ measured waves at the end of a jetty and wind at a height of 100 m in the shipyard of Samsung Heavy Industries Co., Ltd. (hereafter referred to as the SHI yard) are used in advance to investigate the feasibility of these conversions. This study proposes the conversion relations between different conditions for wind and waves. For waves, an uncertainty correction factor with different reference periods is suggested to convert and compare the significant wave heights for the data sets in the Donghae gas field and the SHI yard. For wind, the traditional Norwegian Petroleum Directorate (NPD) wind profile optimized for open sea as recommended by DNV GL is directly used to convert the wind speed in the Donghae gas field with different reference periods. However, because of significantly complex terrain conditions in the SHI yard, a newly modified NPD wind profile is suggested to adjust the turbulence intensity. Then it is applied to convert and compare the wind speed in the SHI yard. This modified NPD wind profile shows a good match, but it requires further study because of the limited data length used in this study.
There is a growing interest in renewable energy around the world to reduce gas emissions from the combustion of fossil fuels. The Korean government has also developed offshore wind power as an alternative. Reliable design environment conditions such as wind and waves are highly desired in applications of offshore structures or floating offshore wind turbines (FOWTs). Unfortunately, there are several different reference periods of duration of wind and waves with different recording intervals, including idling times. For example, the National Oceanic and Atmospheric Administration (NOAA) hindcast wave data typically provide 3 hr-Hs and 10 m-1 hr-Vw every 3 hr as an offshore standard, where 3 hr-Hs denotes significant wave height (Hs) in a 3 hr reference period, and 10 m-1 hr-Vw denotes the 1 hr average wind speed (Vw) at an average water level of 10 m in a 1 hr reference period. Meanwhile, the Korea Meteorological Administration (KMA) in South Korea provides measurement data recorded by an offshore wave buoy composed of 17 min-Hs for wave heights and 5 m-10 min-Vw for wind speeds. Their recording interval is 30 min or 1 hr. Waves are sampled at 1 Hz. Every one of the 1,024 samples is analyzed by Fourier transform to get spectral quantities of Hs and the spectral peak wave period in seconds (Tp). The height of an anemometer on the buoy is about 5 m from its draft. Therefore, the conversion relations of magnitudes of wind and waves with different reference periods should be considered to compare them with different sources of data sets of wind and waves.
