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Structu
ralDesign
of W
aveEn
ergy Devices
–w
ww
.sdw
ed.civil.aau
.dk
WP 3
Power-Take-Off Systems
03-09-2010
Structu
ralDesign
of W
aveEn
ergy Devices
–w
ww
.sdw
ed.civil.aau
.dk
Work Package 3
Work package partners:
Department of Energy Technology of the University of Aarlborg (AAU-E)
Fraunhofer Institute for Windenergy and Energy System Technology (IWES)
Research areas:
Electrical rotating and linear generators
Energy storage systems
Simulation of PTO-systems
Structu
ralDesign
of W
aveEn
ergy Devices
–w
ww
.sdw
ed.civil.aau
.dk
03-09-2010
Overview
• WEC concepts and impact on the PTO-systems
• Generator systems
• Energy storage systems
• Simulation of PTO-Systems
Structu
ralDesign
of W
aveEn
ergy Devices
–w
ww
.sdw
ed.civil.aau
.dk
03-09-2010
Oscillating Water Column
Oscillating Bodies Overtopper
Energy conversion step 1
Air-chamber Oscillating body Water-ramp/water-reservoir
Energy conversion step 2
Fast rotating air-turbine
Hydraulic PTO Slow rotatingturbine
Generator system Rotating generator Linear or rotating generator
Rotating generator
Integrated energy storage system
Turbine, generator Hydraulic-Tank,generator
Water-reservoir,generator, turbine
WEC Concepts
Oscillating Water Column Oscillating Bodies Overtopper(picture: Ocean Energy) (picture: PELAMIS) (picture: WaveDragon)
Structu
ralDesign
of W
aveEn
ergy Devices
–w
ww
.sdw
ed.civil.aau
.dk
03-09-2010
WEC concept:
Overtopper: generator system for low turbine speed
Oscillating body: linear generator designed for high force
Structure of generator system depends on WEC concept
Grid connection:
Smooth power delivered to the grid
General requirements:
Efficiency
Life time
Overload capacity
Scalability
=> Costs
Criteria for Generator System Design
€
(picture: WaveDragon)
(picture: Transpower)
Structu
ralDesign
of W
aveEn
ergy Devices
–w
ww
.sdw
ed.civil.aau
.dk
03-09-2010
ASG gear box
Three conversion steps:
1 – adaption to turbine speed
2 – conversion to electrical power
3 – grid connection Generator system components
Speed increaser
- Mechanical- Hydrodynamical- Hydrostatical
Generator - Induction generator- Doubly fed induction
generator- Synchronous generator
Frequency converter
- Intermediate voltage circuit
- Current-source - Direct converter
Components for Rotating Generator Systems
Generator system design:
Specification/choice of components
according to the criteria
Typical generator system
Structu
ralDesign
of W
aveEn
ergy Devices
–w
ww
.sdw
ed.civil.aau
.dk
Rework criteria considering partload
System 1: three-stage gearbox + doubly fed induction generator (DFIG)
System 2: high-pole permanent magnetic
synchronous generator (PM)
Variation of Generator System
(picture: WaveDragon)
Adaption to low turbine speed:
box gear
ASG System 1:
System 2:
System comparison:
Structu
ralDesign
of W
aveEn
ergy Devices
–w
ww
.sdw
ed.civil.aau
.dk
03-09-2010
Fluctuating power input Energy Storage System Smooth grid power
Wave characteristic
Period time: ..5..10 seconds
Power frequency = 2 * wave frequency
Requirements
High cycle lifetime
Short charge / discharge time
Single device <-> farm solution
Integrated storage systems
Inertia of rotating components
Hydraulic system
Water-reservoir
Impact on PTO
Derating of generator system
Damping of PTO-system
Degree of freedom for plant control system
Energy Storage Systems
(picture: Enercon) (picture: Transpower)
Structu
ralDesign
of W
aveEn
ergy Devices
–w
ww
.sdw
ed.civil.aau
.dk
03-09-2010
Storage System Wh/kg W/KG Life time (cycles)
Efficiency(%)
Cost(US$/kWH)
Battery 35-130 150-350 700-1000 75-95 150-2000
Ultracapacitor 5 2000 500.000 93-98 25.000
Flywheel 40 3000 5000 90 20.000
Characteristics of Storage Systems
(picture: DETA) (picture: WIMA) (picture: Enercon)Battery Ultracapacitor Flywheel
Structu
ralDesign
of W
aveEn
ergy Devices
–w
ww
.sdw
ed.civil.aau
.dk
03-09-2010
Design Process Tasks
• Definition of criteria for WEC
• Identification of system/components
• Benchmark of systems according to criteria
• Verification of choosen system/components -> simulation
Structu
ralDesign
of W
aveEn
ergy Devices
–w
ww
.sdw
ed.civil.aau
.dk
Sub model components
Requirements:
Multiphysic system simulation
Large component model libraries
Interface to overall model
High performance
Use cases:
Reliability investigations
Yield calculations
Operation control verification
Compoment dimensioning, etc
Modelling of PTO-System
(Bonfiglioli) (Hybrid Systems LLP)
(DETA) (Siemens) (AW)
(Parkers) (Siemens) (ZF)
(picture: Pelamis)
Structu
ralDesign
of W
aveEn
ergy Devices
–w
ww
.sdw
ed.civil.aau
.dk
Use Case Cycle time range
Yield calculation Minutes - hours
Operation control Seconds
Reliability Milliseconds -seconds
Graded models:
Level 1: transient values
Level 2: effective values
Level 3: power flux
=> Optimized models, adapted to use case
• Vibrations,
• Failure scenarios
• Switching operations
• Annual yield calculation
• Daily course investigations
Graded Models
Level 1 model for synchronous generator
Level 3 model for synchronous generator
Structu
ralDesign
of W
aveEn
ergy Devices
–w
ww
.sdw
ed.civil.aau
.dk
Interface
Balance variables
ForceVelocity
Rotation speedTorque
Voltage Current
Candidate tools:
Matlab/Simulink
Simplorer
Modellica
Force / counterforce
Velocity
physical behaviour of a multi-body system
Generic interface
(picture: Ocean Energy)
(picture: Kymaner)
Structu
ralDesign
of W
aveEn
ergy Devices
–w
ww
.sdw
ed.civil.aau
.dk
03-09-2010
Simulation Tasks
• Design of interface
• Choose simulation tools
• Development of component models (if necessary)
• Integration into overall model
• Application of model to WEC
Funded by
The International Research Alliance
03-09-2010
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