Preprints
https://doi.org/10.5194/wes-2021-74
https://doi.org/10.5194/wes-2021-74

  27 Aug 2021

27 Aug 2021

Review status: this preprint is currently under review for the journal WES.

Land-based wind turbines with flexible rail transportable blades – Part II: 3D FEM design optimization of the rotor blades

Ernesto Camarena1, Evan Anderson1, Josh Paquette1, Pietro Bortolotti2, Roland Feil2, and Nick Johnson2 Ernesto Camarena et al.
  • 1Sandia National Laboratories, Albuquerque, NM 87185, USA
  • 2National Renewable Energy Laboratory, National Wind Technology Center, Golden, CO 80401, USA

Abstract. Increasing growth in land-based wind turbine blades to enable higher machine capacities and capacity factors is creating challenges in design, manufacturing, logistics, and operation. Enabling further blade growth will require technology innovation. An emerging solution to overcome logistics constraints is to segment the blades spanwise and chordwise, which is effective, but the additional field-assembled joints result in added mass and loads, as well as increased reliability concerns in operation. An alternative to this methodology is to design slender flexible blades that can be shipped on rail lines by flexing during transport. However, the increased flexibility is challenging to accommodate with a typical glass-fiber, upwind design. In a two-part paper series, several design options are evaluated to enable slender flexible blades: downwind machines, optimized carbon fiber, and active aerodynamic controls. Part 1 presents the system-level optimization of the rotor variants as compared to conventional and segmented baselines, with a low-fidelity representation of the blades. The present work, Part 2, supplements the system-level optimization in Part 1 with high-fidelity blade structural optimization to ensure that the designs are at feasible optima with respect to material strength and fatigue limits, as well as global stability and structural dynamics constraints. To accommodate the requirements of the design process, a new version of the Numerical Manufacturing And Design (NuMAD) code has been developed and released. The code now supports laminate-level blade optimization and an interface to the International Energy Agency Wind Task 37 blade ontology. Transporting long, flexible blades via controlled flapwise bending is found to be a viable approach for blades up to 100 m. The results confirm that blade mass can be substantially reduced by going either to a downwind design or to a highly coned and tilted upwind design. A discussion of active and inactive constraints consisting of material rupture, fatigue damage, buckling, deflection, and resonant frequencies is presented. An analysis of driving load cases revealed that the downwind designs are dominated by loads from sudden, abrupt events like gusts rather than fatigue. Finally, an analysis of carbon fiber spar caps for downwind machines finds that, compared to typical carbon fibers, the use of a new heavy-tow carbon fiber in the spar caps is found to yield between 9 % and 13 % cost savings.

Ernesto Camarena et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on wes-2021-74', Malo Rosemeier, 30 Aug 2021
  • RC1: 'Comment on wes-2021-74', Anonymous Referee #1, 30 Sep 2021
  • RC2: 'Comment on wes-2021-74', Anonymous Referee #2, 13 Oct 2021

Ernesto Camarena et al.

Ernesto Camarena et al.

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Latest update: 25 Oct 2021
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Short summary
The length of rotor blades of land-based wind turbines is currently constrained by logistics constraints. Turbine manufacturers currently propose segmented solutions to overcome these limits, but blade joints come with extra masses and costs. This work investigates an alternative solution, namely the design of ultra-flexible blades that can be transported on rail via controlled bending. The results show that this is a promising pathway to further increase the size of land-based wind turbines.