Analysis of throw distances of detached objects from horizontal-axis wind turbines

Abstract

This paper aims at predicting trajectories of the detached fragments from wind turbines, in order to better quantify consequences of wind turbine failures. The trajectories of thrown objects are attained using the solution to equations of motion and rotation, with the external loads and moments obtained using blade element approach. We have extended an earlier work by taking into account dynamic stall and wind variations due to shear, and investigated different scenarios of throw including throw of the entire or a part of blade, as well as throw of accumulated ice on the blade. Trajectories are simulated for modern wind turbines ranging in size from 2 to 20 MW using upscaling laws. Extensive parametric analyses are performed against initial release angle, tip speed ratio, detachment geometry, and blade pitch setting. It is found that, while at tip speeds of about 70 m/s (normal operating conditions), pieces of blade (with weights in the range of approximately 7-16 ton) would be thrown out less than 700 m for the entire range of wind turbines, and turbines operating at the extreme tip speed of 150 m/s may be subject to blade throw of up to 2 km from the turbine. For the ice throw cases, maximum distances of approximately 100 and 600 m are obtained for standstill and normal operating conditions of the wind turbine, respectively, with the ice pieces weighting from 0.4 to 6.5 kg. The simulations can be useful for revision of wind turbine setback standards, especially when combined with risk assessment studies.

Retracted: Analysis of blade fragment risk at a wind energy facility

“…Since their report, there has been a renewed interest in modeling risk, with several authors reporting on analysis of that risk. [5][6][7][8] The state-of-the-art modeling approach is 6 degrees-of-freedom motion of the blade fragments with aerodynamic loading. Simplified models do not match the results of the 6 degrees-of-freedom models; Sørensen 9 showed that drag ballistics do not capture the downwind distance and the range for vacuum ballistics is too far.…”

Analysis of blade fragment risk at a wind energy facility

“…The blade properties were matched at values of percentage radius. The Siemens turbine was scaled from the 1.5 model using scaling laws described in Sarlak and Sørensen for mass, mass center, and mass moment of inertia scaling. The adjustment to the mass was: where m ref is the reference (known) mass, and r ref is the reference radius.…”

“…Larwood and van Dam reported on the history of this risk and the modeling of rotor fragments in the context of safety setbacks for wind turbines. Since their report, there has been a renewed interest in modeling, with several authors reporting on fragment analysis . The state‐of‐the‐art modeling approach is six degrees‐of‐freedom (6DOF) motion of the blade fragments with aerodynamic loading.…”

Methodology to assess wind turbine blade throw risk to vehicles on nearby roads

“…The simulation used to model free-flight motion of a blade fragment includes the effects of aerodynamic and gravity forces as well as aerodynamic moments, and is identical to the one used in Slegers et al (2009) and Rogers et al (2012). Similar free-flight simulation models have been employed by Sarlak and Sørensen (2016) as well as Larwood and van Dam (2015). In light of the prevalence of such models across the prior literature on this topic, only a high-level overview of the trajectory simulation model will be presented here.…”

“…Numerous authors over the past 25 years have derived and used physics-based models to estimate lateral throw distances of blade fragments or ice fragments potentially released from wind turbines (Biswas et al, 2012; Eggers et al, 2001; Macqueen et al, 1983; Morgan and Bossanyi, 1996; Sarlak and Sørensen, 2016; Slegers et al, 2009; Szász et al, 2019). A common approach in the literature is to use a 6-degree-of-freedom modeling approach to simulate the flight of blade fragments, and a point-mass model to simulate the motion of ice fragments due to their irregular shape.…”