The dynamic yaw significantly affects the aerodynamic load distribution of wind turbines, and the aerodynamic load is one of the main influencing factors of wind turbine structural stress variation. Taking the NACA4415 horizontal axis wind turbine designed by the research group as the research object, the numerical simulation was used to analyze the distribution characteristics of blade stress, surface thrust coefficient, and the wind turbine power output under periodic dynamic yaw conditions. The results show that the blade stress, blade axial thrust, and wind turbine output power were presented as a cosine distribution with yaw fluctuations. The distribution trend of blade stress showed an increase followed by a decrease from the inside out along the span direction. In addition, due to the influence of dynamic yaw and aerodynamic loads, the stress values near the blade root exhibited significant fluctuations. With the increase in tip speed ratio, the stress values of dynamic windward yaw gradually exceeded those of leeward yaw. Within the range of a 10° to 30° yaw variation period, the stress value with positive yaw was larger than that with negative yaw, and the highest stress value occurred in the range of −5° to 15°. The results can be provided as a theoretical basis for the structural design and yaw control strategies of wind turbines, considering dynamic yaw operation.

In this paper, the effect of melting characteristics of CuO/paraffin wax composite phase change material in a spherical heat storage unit in a constant temperature water bath is investigated. Experiments were conducted in three different water bath temperatures (65 °C, 70 °C, and 75 °C). The inner surface of the sphere was fixed with two, four, and six pin-shaped fins 3 mm in diameter. The spheres were filled with different mass fractions of CuO nanoparticles/paraffin phase change materials. Experimental CCD was used to model and optimize the spherical thermal storage unit. Regression models were developed to predict the effects of various operational factors on the melting time of the composite PCM. The factors in the model included the number of pin fins in the spherical heat storage unit, the water bath temperature, and the content of added CuO nanoparticles in the PCM, and ANOVA was used to statistically validate the regression model. The results showed that the interaction between the water bath temperature and the number of pin fins had the most significant effect on the melting time. With the melting time of the phase change material as the optimized objective function, the optimized optimal working condition was six pin fins, a water bath temperature of 75 °C, and the addition of 5 wt% CuO nanoparticles/paraffin phase change material, and the actual melting time under this condition was 78.9 min, which was lower than the predicted value of 79.4 min, with an error of 0.63% between them.