Tall Concrete Wind Turbine Towers
Markus Wernli, PhD, PE
BergerABAM
Outline
1. Market Conditions for Tall Towers
2. Tall Tower Technologies
3. Design Considerations
4. Tower Construction Example
5. Conclusions
Established Wind Industry
• 75 GW Installed Capacity in the U.S
• 5% of Power in U.S. from Wind Energy
• Over 20% of Power in Kansas from Wind Energy
• $128 Billion Invested over Past Decade
Growth of Wind Industry
U.S. Wind Power Installations by State
AWEA Second Quarter 2016 Market Report
KS
Development Path of Wind Turbines
Source: NREL/CP-500-43374, Wind Energy Technology: Current Status and R&D Future, 2008
Where the Wind Blew in 2008
Annual Average Wind Speed at 50 m
KS
Where the Wind Blows Today
KS
Where the Wind Blows Tomorrow
KS
Average Turbine Size Installed during
period (only turbines larger than 100 kW)
DOE Wind Technologies Market Report 2014
Trend in Turbine Hub Height in US
DOE 2014 Wind Technologies Market Report
Reasons for Slow Growth of Hub
Height in U.S.
• Tubular steel towers become exponentially more
expensive for heights beyond 100 meters
• Plenty regions that can be developed with
conventional hub heights
• Risk avert industry
• Additional FAA permit requirements for structures
exceeding 500 feet
• Tall towers need to be installed with means of
specialized lifting equipment
• No established wind industry in prime target
markets for tall wind turbines
• Lack of long-term wind measurements at 140
meters
Tall Tower Technologies
Anatomy of a Turbine
• Rotor
• Nacelle
• Turbine
• Tower
• Foundation
By Photo: Molgreen, Animation:Amada44
Advantages of Concrete Towers
• Taller towers to higher, steadier winds
• On-site or off-site component fabrication
• Site assembly with fewer fatigue critical joints
• Enhanced dynamic performance
• Reduction of foundation volume
• Lower maintenance costs inherent with concrete
as the construction material
• Increased service life due to the high fatigue
resistance of prestressed concrete
Current Proprietary Tower Systems on the Market
Enercon
Advanced Tower
Systems
Inneo Torres
Tindall
Enercon
Source: Enercon
Postensa (Advanced Tower System)
Source: Advanced Tower Technology
Acciona
Source: Acciona Wind Power
Tindall
Source: Tindall Corporation
Wind Tower Technologies
Source: MidAmerican
Hexcrete Tower
Source: Iowa State University
Tower Section Connection
• Column Connection Only
• Grouted Keyway
• External PT bars
Source: Iowa State University
Fabrication in Precast Plant
Source: Iowa State University
Transport
Conventional Flat-Bed
Instead of…
Special Transporter
Source: Iowa State University
GE Space Frame Technology
Source: GE Renewable Energy
Keystone Tower Technology
Source: Keystone Tower Systems
Design Considerations
Design Codes and Guidelines
• International Electrotechnical Commission
IEC 61400-1 “Wind Turbines Part 1: Design
Requirements”
• ASCE/AWEA “Recommended Practice for
Compliance of Large Land-based Wind Turbine
Support Structures”
• ACI ITG-9R-16 “Report on Design of Concrete
Wind Turbine Towers”
• DNV-GL “Guideline for the Certification of Wind
Turbines”
• Local Design Codes
Simplified Load Distribution
Assumption
Mandatory Design Checks for Concrete Towers
Dynamic Characteristic of Tower
Relevant Frequencies:
1P = Rotor Evolution
3P = Blade Passing
Fatigue Check
Source: Tindall Corporation
Concrete Fatigue Strength Fatigue Spectrum
Woehler Curves for Concrete per CEB-FIB MC90
Design Check of Foundation
Overburden Soil
Foundation Lift-Off Soil Bearing Check
Soil Pressure
Soil Pressure
Tower Construction Sample
Assembly of Hexcrete Tower
Source: Iowa State University
Assembly of MidAmerican Tower
Source: MidAmerican Energy
Conclusions
Conclusions
Concrete towers are a cost effective solution
for tall wind turbines and will be built in the
U.S. as the wind industry develops in low wind
velocity and high wind shear markets