Two-bladed wind turbines offer the potential for a lower cost of energy compared with three-bladed rotor turbines. This investigation was conducted to quantify the differences between the loads of upwind and downwind two-bladed wind turbines operating under random wind conditions. This paper focuses on a comparison of maximum and average loads that can cause first excursion failure, and loads that can cause fatigue failure. In this study, upwind and downwind turbines with two bladed rotors are compared. The NREL 5MW reference wind turbine was used as a baseline design and was modified as necessary to design a two bladed upwind wind turbine. The tower shadow effect was considered for the downwind turbine. The IEC61400-3 standard load cases were used to define the loading conditions for the wind turbine simulations. The computed load effects generally showed that the downwind configuration had lower load effects. Moreover, fatigue damage was lower for the two-bladed downwind turbine compared to the upwind turbine.
There is randomness in both the applied loads and the strength of systems. Therefore, to account for the uncertainty, the safety of the system must be quantified using its reliability. Monte Carlo Simulation (MCS) is widely used for probabilistic analysis because of its robustness. However, the high computational cost limits the accuracy of MCS. Smarslok et al. [2010] developed an improved sampling technique for reliability assessment called Separable Monte Carlo (SMC) that can significantly increase the accuracy of estimation without increasing the cost of sampling. However, this method was applied to time-invariant problems involving two random variables. This paper extends SMC to problems with multiple random variables and develops a novel method for estimation of the standard deviation of the probability of failure of a structure. The method is demonstrated and validated on reliability assessment of an offshore wind turbine under turbulent wind loads. The results show the method can reduce the computational cost by two orders of magnitude compared to standard MCS for failure probabilities as low as 10 −4 .
In this study, load effects of identically rated power two- and three-bladed rotor wind turbines are computed and compared using the requirements of the IEC61400-3 standard. The two-bladed turbine includes a teeter mechanism. Moreover, an improved blade design is considered for the two-bladed turbine. A series of wind turbine operational simulations was performed for the wind turbine models under selected design load cases of IEC61400-3 standard. Loads were computed using the FAST code. The series of simulations were driven and post-processed using the FAST_SM code. Additionally, fatigue damages of the two- and three-bladed rotor wind turbines were computed. The study showed that the maximum load effects and fatigue damage of the two-bladed wind turbine generally increased compared to the three-bladed turbine. The simulation results also showed that the baseline design blade of the two-bladed wind turbine requires improvement in order to sustain the computed large load effects.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.