The offshore wind market is growing rapidly as the world is investing heavily in renewable energy to curb rising global temperatures and reduce greenhouse gas emissions. South Korea also announced that it will install 3 GW of onshore wind turbines and 13 GW of offshore wind turbines in the "3020 implementation plan for renewables" announced in 2017. However, the reality of the wind industry is different from the rosy outlook of the government. The "Tamra offshore wind power project" and the "southwest offshore wind power project" have been delayed for a long time. The Korean Wind Energy Society (KWEA) conducted an online survey to determine what domestic offshore wind power experts thought about the delays of the two projects, the technology level and the industry status of domestic offshore wind power. The experts point out that the development of the two projects has been delayed because of difficulties in securing the acceptance of local residents. Many experts answered that the technology gap with Europe is more than 5 years. Wind turbines are a core technology that has the biggest technical gap. The reason for its low profitability was that most experts chose a low wind speed compared to Europe.

Multi-MW wind turbines have very long and large blades. There are some factors that exert asymmetric dynamic thrusts on a blade. Wind shear is one of the main factors that produce asymmetric dynamic loads on a blade of a multi-MW wind turbine. In this paper, a 2 MW on-shore wind turbine that has three blades with a rotor radius of 40 m and hub height of 60 m is considered and thrust variations on a blade under wind shear are calculated according to the wind speed. The commercial software GH Bladed is used for calculating thrust variations based on the blade element momentum (BEM) method. And the amplitudes of the thrust variations by wind shear with varying wind speed are investigated by introducing a "wind shear coefficient of thrust variation" based on the steady-state value of thrust without wind shear.

In order to assess the accuracy of four-beam nacelle light detection and ranging (LIDAR) measurements, a field measurement campaign was carried out in Dongbok wind farm on Jeju Island. The four-beam nacelle LIDAR was set up on the nacelle of a test wind turbine of HJWT 2,000 kW with an 80 m hub height for this investigation. The ground-based LIDAR was situated at three times the rotor diameter of the test wind turbine. First, the ground-based LIDAR measurements were verified by comparing them with neighboring 80-meter-tall met mast wind data. Then, the four-beam nacelle LIDAR measurements were compared with the ground-based LIDAR measurements. The carrier to noise ratio (CNR) variation was analyzed in terms of weather conditions (temperature, pressure, humidity) and mechanical movement (blade rotation, tilt variation of wind turbine). Measurement deviations were also analyzed according to data availability. Based on the analysis results of the characteristics of LIDAR measurements, reliable ground-based and nacelle LIDARs data sets were chosen for linear regression analysis. As a result, it was confirmed that the average CNR signals were higher than the CNR threshold in various weather conditions. The mechanical movement did not cause LIDAR measurement deviation. The correlation between wind data by nacelle and ground-based LIDARs was considerably high with a regression coefficient of 1.01 and coefficient of determination of 0.98.

To reduce capital expenditures for offshore wind farms, new concepts of support structures have been suggested. Floated gravity base structures (GBSs), which use the buoyancy of the structure instead of using heavy lift vessels during the transport and installation process, are receiving much attention. The main difference between the floated GBS and conventional structures is a design based on floating stability. A floated GBS should maintain floating stability on its own until it is lowered onto the seabed. Therefore, the concept design of the floated GBS is derived to satisfy the minimum metacentric height of 0.75 m during the lowering operation in the installation. As floated GBSs are ballasted with sea water during installation, free surface effects and bulkheads are also taken into account. In regard to the model with a conical base, designs with minimum weights are presented by varying the batter angle of the base. In addition, the maximum load at the bottom of each design is analyzed to assess the bearing capacity of floated GBSs. Although the weight of the floated GBS is minimized at a batter angle of $0^{\circ}$, a batter angle larger than $30^{\circ}$ is recommended in consideration of the bearing capacity.