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Title: Downwind pre-aligned rotors for extreme-scale wind turbines

Downwind force angles are small for current turbines systems (1-5 MW) such that they may be readily accommodated by conventional upwind configurations. However, analysis indicates that extreme-scale systems (10-20 MW) will have larger angles that may benefit from downwind-aligned configurations. To examine potential rotor mass reduction, the pre-alignment concept was investigated a two-bladed configuration by keeping the structural and aerodynamic characteristics of each blade fixed (to avoids a complete blade re-design). Simulations for a 13.2 MW rated rotor at steady-state conditions show that this concept-level two-bladed design may yield 25% rotor mass savings while also reducing average blade stress over all wind speeds. These results employed a pre-alignment on the basis of a wind speed of 1.25 times the rated wind speed. The downwind pre-aligned concept may also reduce damage equivalent loads on the blades by 60% for steady rated wind conditions. Even higher mass and damage equivalent load savings (relative to conventional upwind designs) may be possible for larger systems (15-20 MW) for which load-alignment angles become even larger. Furthermore, much more work is needed to determine whether this concept can be translated into a practical design that must meet a wide myriad of other criteria.
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [4]
  1. Univ. of Virginia, Charlottesville, VA (United States)
  2. Stanford Univ., Stanford, CA (United States)
  3. Univ. of Illinois at Urbana-Champaign, Urbana, IL (United States)
  4. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Report Number(s):
NREL/JA-5000-68262
Journal ID: ISSN 1095-4244
Grant/Contract Number:
AC36-08GO28308
Type:
Accepted Manuscript
Journal Name:
Wind Energy
Additional Journal Information:
Journal Volume: 20; Journal Issue: 7; Journal ID: ISSN 1095-4244
Publisher:
Wiley
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Country of Publication:
United States
Language:
English
Subject:
17 WIND ENERGY; downwind; extreme scale; load aligned; turbine; wind energy
OSTI Identifier:
1364153