BAR: Big Adaptive Rotor Project

BAR aims to maximize the advantages of large-scale land-based rotors and their potential for increased energy generation.

Now in its second phase, the project involves researchers from NREL and Sandia National Laboratories.

Wind turbine

Hanging on the leading edge. Large rotors increase capacity factors and the amount of power a turbine outputs on average over the course of a year. Photo by Dennis Schroeder, NREL 27205

Building Better (Highly Flexible) Blades

The past few decades have seen substantial reductions in the cost of wind energy. One key factor behind this trend has been the increase in average rotor size. Larger rotors capture more energy while limiting costs, such as operation and maintenance and balance of stations. Low-specific-power turbines, i.e., relatively larger rotors on the same machine rating, increase capacity factors and the availability of wind power.

The U.S. Department of Energy's BAR project conducts several investigations to design the land-based wind turbines of the future. Investigating innovations like highly flexible blades, controlled-bending of components during rail transportation, distributed aerodynamic control, and novel materials in manufacturing could  simultaneously boost wind energy capture while limiting costs.

Coding Advances for Larger Land-Based Wind

To help clarify and better articulate the science and engineering hurdles facing potential turbine concepts, researchers have been extending the modeling capabilities of a variety of NREL's numerical tools. Improvements have been implemented in aeroservoelastic model OpenFAST, conceptual wind turbine design framework Wind-Plant-Integrated System Design and Engineering Model, turbine Reference OpenSource Controller, and the novel design framework Wind Energy with Integrated Servo-control. All these tools allow to model turbine performance and turbine system-level interactions.

BAR researchers have also developed cOnvecting LAgrangian Filaments, a new free-vortex wake module included in NREL's OpenFAST wind turbine simulation tool. The models the turbine wake using particles connected via filaments and is programmed to generate realistic representations of large, flexible turbine blades, providing users an alternative to traditional, lower-fidelity aerodynamic models. As an open-source, mid-fidelity tool, cOnvecting LAgrangian Filaments enables designers throughout the wind industry to more accurately and predictably model their own designs, reducing their development costs, while further developing the software collaboratively.

The BAR project has finally funded improvements to detailed, cross-sectional analysis solver ANBA4 and composite blade mesh tool Structural Optimization and Aeroelastic Analysis. These two tools are under active development.

Bar Project Team


Co-Project Lead: Nick Johnson

NREL research engineers include:

  • Ben Anderson
  • Pietro Bortolotti
  • Emmanuel Branlard
  • Scott Carron
  • Chris Kelley
  • Nicole Mendoza
  • Andy Platt
  • Kelsey Shaler.

Sandia National Laboratories

Co-Project Lead: Josh Paquette

Sandia National Laboratory research engineers include:

  • Evan Anderson
  • Ernesto Camarena
  • Chris Kelley.


Pietro Bortolotti

Researcher III, Mechanical Engineer