Nowadays, interest in renewable energy is increasing. Electricity demand is steadily increasing due to industrialization; however, it is not possible to continue to use nuclear power plants and coal-fired power plants that are vulnerable to earthquakes and the main cause of fine dust, respectively. Wind power generation is a representative renewable energy source that generates electricity using the kinetic energy of wind, and is also a representative countermeasure against climate change that does not emit greenhouse gases. In this study, a 12 MW wind turbine blade was designed based on the NREL 5 MW standard wind turbine. Most of the blade information was extended using a scale ratio, and other blade information was adjusted to its characteristics.

This paper reviews the history and status of wind energy in South Korea using the wind power generation statistics (2002~2016) provided by the Electric Power Statistics Information System (EPSIS) and "2015 Renewable Energy Supply Statistics" from the Ministry of Trade, Industry, and Energy. In addition, the prediction accuracy of the Korea wind resource map made by the Korea Institute of Energy Research (KIER) was evaluated through correlation analysis of capacity factor by province between EPSIS and KIER. The average capacity factor of wind energy in South Korea is 23 %, which is in the middle class among the IEA Wind member countries. The monthly capacity factors of EPSIS and KIER showed a high correlation of R²=0.78. It was clearly reaffirmed that the wind energy supply is directly linked to the government's support policy. Therefore, in order to achieve the goal of 20 % renewable energy supply by 2030, establishing effective government policies is a matter of urgency to maximize the market share of domestic wind turbines and to solve conflicts related to environmental regulations and public acceptance.

A wind tunnel test for the side-furling device that was used for a horizontal type small wind turbine to reduce the output power in a high wind speed condition was conducted in a 5 m × 3.75 m open-jet test section. A simple experimental wind turbine model with a "MEXICO blade" and electric motor was used to simulate the small wind turbine system. The furling force of the tail was measured by a force sensor installed on the furling arm and the yawing moment of the turbine was measured by a moment sensor installed on the turbine strut. The turbine power was calculated by using the torque of the rotating axis and the rotational speed of the blade. Force characteristics of the tail system were studied by changing the arm length, wind speed and flow direction. Moment characteristics of the nacelle and blade system were studied by changing the offset distance, wind speed and RPM. Moment equilibrium conditions for the typical wind speed were estimated from those test results and confirmed by a fixed-tail-angle test. A free-tail-angle test was also conducted to verify the effect of the side-furling device in high wind speed conditions.

A concrete offshore wind turbine structure supported with suction pile for a weak soil foundation was proposed, and ship collision analysis was carried out to evaluate the concrete structure with a ship impact load. To take into account the effect of suction pile and soil on the structure, a lumped parameter model was used to calculate the soil stiffness matrix. As the first step, a linear analysis of the structure was carried out for a feasibility assessment of the designed structure. A 5 MW wind turbine and the environmental conditions of the southwest coast of Korea were applied. In a quasi-static analysis, maximum displacements and stresses did not exceed the allowable values from the offshore standard, and it was determined that no resonance occurred in a natural frequency analysis. For the ship collision evaluation, a nonlinear dynamic algorithm of ship collision was performed using a nonlinear concrete material model. A ship impact-load time history curve was applied, and maximum displacement and principal stresses were calculated. The principal stresses were not exceeded in the range of the concrete strength. Thus, damage to the concrete structure by ship collision was small, and it has enough stability to be applied on the southwest coast of Korea. Consequently, it is expected that the proposed structure can be a good solution for offshore wind farms.