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DEPARTMENT OF CIVIL ENGINEERING
AALBORG UNIVERSITY, DENMARK
www.civil.aau.dk Copenhagen August 30th 2010 1
SDWED:
WAVE TO WIRE MODELLING
Peter Frigaard
Department of Civil Engineering,Aalborg University
Denmark
DEPARTMENT OF CIVIL ENGINEERING
AALBORG UNIVERSITY, DENMARK
www.civil.aau.dk Copenhagen August 30th 2010 2
TRADITIONAL DEFINITION
A “wave to wire model” is a numerical
model (or a suit of numerical models)
used to evaluate the electrical power
generated by a given wave energy
converter from given wave conditions.
DEPARTMENT OF CIVIL ENGINEERING
AALBORG UNIVERSITY, DENMARK
www.civil.aau.dk Copenhagen August 30th 2010 3
OUR DEFINITION
A “wave to wire model” is a numerical
model (or a suit of numerical models)
used to evaluate the forces acting on a
wave energy converter, the stresses in
the structure, the behavior and the
electrical power generated by a given
wave energy converter from given
wave conditions.
DEPARTMENT OF CIVIL ENGINEERING
AALBORG UNIVERSITY, DENMARK
www.civil.aau.dk Copenhagen August 30th 2010 4
WHAT WILL WE USE THE MODEL
FOR?
Analyze/optimize behavior of system
(Wave energy converter)
• Efficiency
• Yearly power production
• Dimension of structure (Cost)
• Cost of energy
• Other environmental effects
DEPARTMENT OF CIVIL ENGINEERING
AALBORG UNIVERSITY, DENMARK
www.civil.aau.dk Copenhagen August 30th 2010 5
PROBLEM
Everything depends on everything.
Coupled problem
• Wave Forces
• Mooring
• Structural design
• Control Strategy
• Power production
DEPARTMENT OF CIVIL ENGINEERING
AALBORG UNIVERSITY, DENMARK
www.civil.aau.dk Copenhagen August 30th 2010 6
Example 1: Wave Dragon- A Slack Moored Wave Energy Device of the Overtopping Type 2003-2008
What if we cange the moorings ? / Control Strategy ?
www.wavedragon.net
1:50 Model in
Wave Tank
DEPARTMENT OF CIVIL ENGINEERING
AALBORG UNIVERSITY, DENMARK
www.civil.aau.dk Copenhagen August 30th 2010 7
DEPARTMENT OF CIVIL ENGINEERING
AALBORG UNIVERSITY, DENMARK
www.civil.aau.dk Copenhagen August 30th 2010
Example 1: Wave STAR- A Multipoint absorber
What if we cange the Control Strategy ?
DEPARTMENT OF CIVIL ENGINEERING
AALBORG UNIVERSITY, DENMARK
www.civil.aau.dk Copenhagen August 30th 2010 9
AGAIN THE PROBLEM
Everything depends on everything.
System must be solved in one go.
Traditional strategy: We use linear
subsystems – or model subsystems
using linear models.
Change from components to system
approach.
DEPARTMENT OF CIVIL ENGINEERING
AALBORG UNIVERSITY, DENMARK
www.civil.aau.dk Copenhagen August 30th 2010 10
Design considerations
• The ratio between design forces and operationel
forces are for Wave Energy devices typically 2-30,
where they for wind turbines are 1-2.
• As many forces as possible shall be taken as
„internal‟ forces, i.e. Pelamis where only 2. order
drift forces are taken by the moorings. The
reference point (foundation) shall not act against
all forces.
DEPARTMENT OF CIVIL ENGINEERING
AALBORG UNIVERSITY, DENMARK
www.civil.aau.dk Copenhagen August 30th 2010 11
SSG Project
Wave Forces
• Model tests for Gorliz, Spain
project
DEPARTMENT OF CIVIL ENGINEERING
AALBORG UNIVERSITY, DENMARK
www.civil.aau.dk Copenhagen August 30th 2010 12
Resonance systems
In t
Test from Griet De Backer, Ghent and my holiday
DEPARTMENT OF CIVIL ENGINEERING
AALBORG UNIVERSITY, DENMARK
www.civil.aau.dk Copenhagen August 30th 2010 13
In the range from normal wave to
survival condition it might be preferred
to use different numerical tools, and in
addition to power production also
evaluates design loads, fatigue elements
(WP5), control and failure aspects
associated with the wave energy
converter.
DEPARTMENT OF CIVIL ENGINEERING
AALBORG UNIVERSITY, DENMARK
www.civil.aau.dk Copenhagen August 30th 2010
Some systems might benefit or even
need estimations of the future.
14
DEPARTMENT OF CIVIL ENGINEERING
AALBORG UNIVERSITY, DENMARK
www.civil.aau.dk Copenhagen August 30th 2010 15
For Each Floater (in Real Time) we:
• Estimate the “Next Wave”. Difficult because Waves are
Dispersve and 3D
• Estimate Force on Floater. “Wamit-type” Multibody
Software (Depend on Control Strategy)
• Select “Gear” for the Power Take-Off for Each Floater
DEPARTMENT OF CIVIL ENGINEERING
AALBORG UNIVERSITY, DENMARK
www.civil.aau.dk Copenhagen August 30th 2010
Power and Efficiency
0.0
2.0
4.0
6.0
8.0
10.0
12.0
0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00
Hs [m]
Ave
rage
Pow
er [k
W]
Produced Estimated Hydraulic
DEPARTMENT OF CIVIL ENGINEERING
AALBORG UNIVERSITY, DENMARK
www.civil.aau.dk Copenhagen August 30th 2010
DEPARTMENT OF CIVIL ENGINEERING
AALBORG UNIVERSITY, DENMARK
www.civil.aau.dk Copenhagen August 30th 2010 18
What do we have today on wave to wire models?
• Basically nothing on system level. A lot on component
level. Some device depended system models.
What to do:
• Define interfaces
DEPARTMENT OF CIVIL ENGINEERING
AALBORG UNIVERSITY, DENMARK
www.civil.aau.dk Copenhagen August 30th 2010 19
To repeat
• We need models of systems
• We need non linear models of components
• Real time systems -> approximations
• Focus on structure more than power
production
• We have to decrease design loads
DEPARTMENT OF CIVIL ENGINEERING
AALBORG UNIVERSITY, DENMARK
www.civil.aau.dk Copenhagen August 30th 2010 20
Thank You….
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