sdwed: wave to wire modelling · • model tests for gorliz, spain project. department of civil...

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




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.




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.




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




PROBLEM

Everything depends on everything.

Coupled problem

• Wave Forces

• Mooring

• Structural design

• Control Strategy

• Power production




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



www.civil.aau.dk Copenhagen August 30th 2010

Example 1: Wave STAR- A Multipoint absorber

What if we cange the Control Strategy ?




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.




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.




SSG Project

Wave Forces

• Model tests for Gorliz, Spain

project




Resonance systems

In t

Test from Griet De Backer, Ghent and my holiday




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.




Some systems might benefit or even

need estimations of the future.

14




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




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




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




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




Thank You….

sdwed: wave to wire modelling · • model tests for gorliz, spain project. department of civil...

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