> Yahoo! is not affiliated with the authors of this page or responsible for its content.
Advanced Wind Turbine Program Next Generation Turbine Development Project: June 17, 1997 -- April 30, 2005
National Renewable Energy Laboratory
Innovation for Our Energy Future
A national laboratory of the U.S. Department of Energy
Office of Energy Efficiency & Renewable Energy
NREL is operated by Midwest Research Institute Battelle Contract No. DE-AC36-99-GO10337
Advanced Wind Turbine
Program Next Generation
Turbine Development Project
June 17, 1997 April 30, 2005
GE Wind Energy, LLC
Tehachapi, California

Subcontract Report
NREL/SR-500-38752
May 2006 Advanced Wind Turbine
Program Next Generation
Turbine Development Project
June 17, 1997 April 30, 2005
GE Wind Energy, LLC
Tehachapi, California
NREL Technical Monitor: S. Schreck

Prepared under Subcontract No. ZAM-7-13320-26
Subcontract Report
NREL/SR-500-38752
May 2006
National Renewable Energy Laboratory
1617 Cole Boulevard, Golden, Colorado 80401-3393
303-275-3000
www.nrel.gov
Operated for the U.S. Department of Energy
Office of Energy Efficiency and Renewable Energy
by Midwest Research Institute
Battelle
Contract No. DE-AC36-99-GO10337


NOTICE
This report was prepared as an account of work sponsored by an agency of the United States government.
Neither the United States government nor any agency thereof, nor any of their employees, makes any
warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or
usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not
infringe privately owned rights. Reference herein to any specific commercial product, process, or service by
trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement,
recommendation, or favoring by the United States government or any agency thereof. The views and
opinions of authors expressed herein do not necessarily state or reflect those of the United States
government or any agency thereof.
Available electronically at
http://www.osti.gov/bridge
Available for a processing fee to U.S. Department of Energy
and its contractors, in paper, from:
U.S. Department of Energy
Office of Scientific and Technical Information
P.O. Box 62
Oak Ridge, TN 37831-0062
phone: 865.576.8401
fax: 865.576.5728
email:
mailto:reports@adonis.osti.gov
Available for sale to the public, in paper, from:
U.S. Department of Commerce
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
phone: 800.553.6847
fax: 703.605.6900
email:
orders@ntis.fedworld.gov

online ordering:
http://www.ntis.gov/ordering.htm
This publication received minimal editorial review at NREL
Printed on paper containing at least 50% wastepaper, including 20% postconsumer waste

Notice Regarding Change of Subcontractor Name
At the time of the submission to the U.S. Department of Energy of the proposal which resulted in
award of NREL Subcontract Number ZAM-7-13320-26, the company now known as GE Wind
Energy LLC was known as Zond Energy Systems, Inc. Zond was subsequently acquired by an­
other company and eventually was sold to GE Power Systems Corp., a subsidiary of General
Electric Corporation, and renamed GE Wind Energy. The present document uses only the names
GE Wind Energy, or simply GE and refers to the companys products as the GE 750 or the GE
1.5, regardless of the time at which work being referenced was conducted. The titles of some
subcontractor reports submitted during earlier stages of this contract and referenced herein con­
tain the older name Zond or the interim names Enron Wind or Enron Wind Energy Systems Cor­
poration (EWESC), and these are the only exceptions to the exclusive use of the GE name.
Acknowledgments
This report summarizes the results of nearly seven years of wind turbine research and develop­
ment by GE Wind Energy and its predecessors. Such a comprehensive undertaking has involved
the contributions of scores of GE employees and dozens of consultants, subcontractors, vendors,
and suppliers. Unfortunately, their number is too great to list them all here, but GE is sincerely
appreciative of all of their individual and collective efforts to accomplish the work presented in
this report.
We have also received substantial technical and project management assistance from dozens of
personnel of the U.S. Department of Energy, the National Renewable Energy Laboratory, and
Sandia National Laboratories. Again, the contributions of all of these people are greatly appreci­
ated. We would specifically like to express our gratitude to Alan Laxson, Brian Smith, Scott
Schreck, Ed Cannon, and Paul Migliore, each of whom served as the NREL Project Manager
during some portion of this project, and to Neil Wikstrom for his seven years as the Subcontract
Administrator for this project.
i Abstract
This document reports the technical results of the Next Generation Turbine Development Project
conducted by GE Wind Energy LLC. This project is jointly funded by GE and the U.S. Depart­
ment of Energys National Renewable Energy Laboratory through Subcontract Number ZAM-7-
13320-26.
The goal of the NGT Program is for DOE to assist the U.S. wind industry in exploring new con­
cepts and applications of cutting-edge technology in pursuit of the specific objective of develop­
ing a wind turbine that can generate electricity at a levelized cost of energy of $0.025/kWh at
sites with an average wind speed of 15 mph (at 10 m height).
GE's NGT Project has consisted of three broad activities:
Concept Studies
Design, Fabrication, and Testing of the Proof of Concepts (POC) turbine
Design, Fabrication, and Testing of the Engineering and Manufacturing Development
(EMD) turbine.
GE Wind personnel, working with consultants, have completed investigations of a number of
wind turbine system and component concepts. The purpose of these studies has been to deter­
mine the trade-off between cost and improvement in energy capture resulting from each of the
concepts. These studies have focused on three broadly defined categories of concepts:
Electromechanical systems
Rotor and structural design
Controls.
The electromechanical systems studies have focused upon a large number of configurations cre­
ated by changing five key parameters:
1. generator synchronous speed and the corresponding required gearing
2. type of generator
3. number of generators
4. speed regulation, that is, variable speed or fixed speed
5. power conversion options.
The result of all of the electromechanical concept studies is that no concept produces a signifi­
cant improvement in the COE delivered by wind power relative to the existing GE Wind turbine
configuration. Only two concepts, 1) a medium-speed wound rotor induction generator operat­
ing in variable-speed, constant-frequency mode, and 2) a medium-speed wound rotor synchro­
nous generator operating in fixed-speed mode show any improvement at all in cost of energy
(COE), and even then, the estimated improvement is less than $0.01/kWh.
The control strategies which have been investigated in the present study are:
Coupling of Blade Pitch and Generator Torque Control
Tracking of Peak Power Coefficient
Tower Vibration Feedback Control
ii Independent Blade Pitch for Asymmetric Load Control
Load-Limiting Control
Alternative Yaw Control Strategies
Damage Monitoring and Feedback Control
Adaptive Drive Train Damping.
All of these concepts except for the alternative yaw control strategies show potential for improv­
ing the cost of energy, either through reductions in loads or improvement of energy capture.
The rotor and structural concepts investigated include:
Rotor and other turbine structural flexibility
Concurrent aerodynamic and structural design optimization
Carbon composite rotor blades
Aeroelastic tailoring of rotor blades
Variable diameter rotors.
Again, all of these concepts show potential for improving COE through either reduced compo­
nent costs or improved energy capture.
The implications of the concept studies that show innovations most likely to produce near-term
COE benefits at risk levels acceptable to the wind energy financial community are:
Optimized low-solidity rotor blades
Larger rotor enabled by sophisticated load-alleviating controls systems
Advanced controls systems, including:
o Independent blade pitch to effect asymmetric load control
o Tower top accelerometer feedback for tower damping
o Coupling of pitch and generator torque control
Taller, more flexible towers.
Achieving the originally stated NGT goal of $0.025/kWh at IEC Class II sites does not appear to
be achievable in the near term for technologies with market-compatible risk levels. GE has iden­
tified through its NGT concept studies, high-risk concepts that can provide additional reductions
in COE between 10%25%, thereby making the $0.025/kWh goal achievable. The most impor­
tant of